€•     Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ+/translations/zh_CN/admin-guide/kdump/kdump”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ+/translations/zh_TW/admin-guide/kdump/kdump”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ+/translations/it_IT/admin-guide/kdump/kdump”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ+/translations/ja_JP/admin-guide/kdump/kdump”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ+/translations/ko_KR/admin-guide/kdump/kdump”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ+/translations/sp_SP/admin-guide/kdump/kdump”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒ@Documentation for Kdump - The kexec-based Crash Dumping Solution”h]”hŒ@Documentation for Kdump - The kexec-based Crash Dumping Solution”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒE/var/lib/git/docbuild/linux/Documentation/admin-guide/kdump/kdump.rst”h KubhŒ	paragraph”“”)”}”(hŒOThis document includes overview, setup, installation, and analysis
information.”h]”hŒOThis document includes overview, setup, installation, and analysis
information.”…””}”(hh¹hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¢)”}”(hhh]”(h§)”}”(hŒOverview”h]”hŒOverview”…””}”(hhÊhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhÇhžhhŸh¶h K	ubh¸)”}”(hX  Kdump uses kexec to quickly boot to a dump-capture kernel whenever a
dump of the system kernel's memory needs to be taken (for example, when
the system panics). The system kernel's memory image is preserved across
the reboot and is accessible to the dump-capture kernel.”h]”hX  Kdump uses kexec to quickly boot to a dump-capture kernel whenever a
dump of the system kernelâ€™s memory needs to be taken (for example, when
the system panics). The system kernelâ€™s memory image is preserved across
the reboot and is accessible to the dump-capture kernel.”…””}”(hhØhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÇhžhubh¸)”}”(hŒ¡You can use common commands, such as cp, scp or makedumpfile to copy
the memory image to a dump file on the local disk, or across the network
to a remote system.”h]”hŒ¡You can use common commands, such as cp, scp or makedumpfile to copy
the memory image to a dump file on the local disk, or across the network
to a remote system.”…””}”(hhæhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÇhžhubh¸)”}”(hŒfKdump and kexec are currently supported on the x86, x86_64, ppc64,
s390x, arm and arm64 architectures.”h]”hŒfKdump and kexec are currently supported on the x86, x86_64, ppc64,
s390x, arm and arm64 architectures.”…””}”(hhôhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÇhžhubh¸)”}”(hX$  When the system kernel boots, it reserves a small section of memory for
the dump-capture kernel. This ensures that ongoing Direct Memory Access
(DMA) from the system kernel does not corrupt the dump-capture kernel.
The kexec -p command loads the dump-capture kernel into this reserved
memory.”h]”hX$  When the system kernel boots, it reserves a small section of memory for
the dump-capture kernel. This ensures that ongoing Direct Memory Access
(DMA) from the system kernel does not corrupt the dump-capture kernel.
The kexec -p command loads the dump-capture kernel into this reserved
memory.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÇhžhubh¸)”}”(hXC  On x86 machines, the first 640 KB of physical memory is needed for boot,
regardless of where the kernel loads. For simpler handling, the whole
low 1M is reserved to avoid any later kernel or device driver writing
data into this area. Like this, the low 1M can be reused as system RAM
by kdump kernel without extra handling.”h]”hXC  On x86 machines, the first 640 KB of physical memory is needed for boot,
regardless of where the kernel loads. For simpler handling, the whole
low 1M is reserved to avoid any later kernel or device driver writing
data into this area. Like this, the low 1M can be reused as system RAM
by kdump kernel without extra handling.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KhhÇhžhubh¸)”}”(hŒ±On PPC64 machines first 32KB of physical memory is needed for booting
regardless of where the kernel is loaded and to support 64K page size
kexec backs up the first 64KB memory.”h]”hŒ±On PPC64 machines first 32KB of physical memory is needed for booting
regardless of where the kernel is loaded and to support 64K page size
kexec backs up the first 64KB memory.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K#hhÇhžhubh¸)”}”(hŒéFor s390x, when kdump is triggered, the crashkernel region is exchanged
with the region [0, crashkernel region size] and then the kdump kernel
runs in [0, crashkernel region size]. Therefore no relocatable kernel is
needed for s390x.”h]”hŒéFor s390x, when kdump is triggered, the crashkernel region is exchanged
with the region [0, crashkernel region size] and then the kdump kernel
runs in [0, crashkernel region size]. Therefore no relocatable kernel is
needed for s390x.”…””}”(hj,  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K'hhÇhžhubh¸)”}”(hX  All of the necessary information about the system kernel's core image is
encoded in the ELF format, and stored in a reserved area of memory
before a crash. The physical address of the start of the ELF header is
passed to the dump-capture kernel through the elfcorehdr= boot
parameter. Optionally the size of the ELF header can also be passed
when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax.”h]”hX‘  All of the necessary information about the system kernelâ€™s core image is
encoded in the ELF format, and stored in a reserved area of memory
before a crash. The physical address of the start of the ELF header is
passed to the dump-capture kernel through the elfcorehdr= boot
parameter. Optionally the size of the ELF header can also be passed
when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax.”…””}”(hj:  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K,hhÇhžhubh¸)”}”(hX  With the dump-capture kernel, you can access the memory image through
/proc/vmcore. This exports the dump as an ELF-format file that you can
write out using file copy commands such as cp or scp. You can also use
makedumpfile utility to analyze and write out filtered contents with
options, e.g with '-d 31' it will only write out kernel data. Further,
you can use analysis tools such as the GNU Debugger (GDB) and the Crash
tool to debug the dump file. This method ensures that the dump pages are
correctly ordered.”h]”hX  With the dump-capture kernel, you can access the memory image through
/proc/vmcore. This exports the dump as an ELF-format file that you can
write out using file copy commands such as cp or scp. You can also use
makedumpfile utility to analyze and write out filtered contents with
options, e.g with â€˜-d 31â€™ it will only write out kernel data. Further,
you can use analysis tools such as the GNU Debugger (GDB) and the Crash
tool to debug the dump file. This method ensures that the dump pages are
correctly ordered.”…””}”(hjH  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K3hhÇhžhubeh}”(h]”Œoverview”ah ]”h"]”Œoverview”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K	ubh¢)”}”(hhh]”(h§)”}”(hŒSetup and Installation”h]”hŒSetup and Installation”…””}”(hja  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj^  hžhhŸh¶h K=ubh¢)”}”(hhh]”(h§)”}”(hŒInstall kexec-tools”h]”hŒInstall kexec-tools”…””}”(hjr  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjo  hžhhŸh¶h K@ubhŒenumerated_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒLogin as the root user.
”h]”h¸)”}”(hŒLogin as the root user.”h]”hŒLogin as the root user.”…””}”(hj‹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KBhj‡  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj‚  hžhhŸh¶h Nubj†  )”}”(hŒDDownload the kexec-tools user-space package from the following URL:
”h]”h¸)”}”(hŒCDownload the kexec-tools user-space package from the following URL:”h]”hŒCDownload the kexec-tools user-space package from the following URL:”…””}”(hj£  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KDhjŸ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj‚  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”Œenumtype”Œarabic”Œprefix”hŒsuffix”Œ)”uh1j€  hjo  hžhhŸh¶h KBubh¸)”}”(hŒAhttp://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools.tar.gz”h]”hŒ	reference”“”)”}”(hjÄ  h]”hŒAhttp://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools.tar.gz”…””}”(hjÈ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”jÄ  uh1jÆ  hjÂ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KFhjo  hžhubh¸)”}”(hŒ(This is a symlink to the latest version.”h]”hŒ(This is a symlink to the latest version.”…””}”(hjÜ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KHhjo  hžhubh¸)”}”(hŒ0The latest kexec-tools git tree is available at:”h]”hŒ0The latest kexec-tools git tree is available at:”…””}”(hjê  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KJhjo  hžhubhŒbullet_list”“”)”}”(hhh]”(j†  )”}”(hŒ?git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git”h]”h¸)”}”(hjÿ  h]”hŒ?git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KLhjý  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjú  hžhhŸh¶h Nubj†  )”}”(hŒAhttp://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
”h]”h¸)”}”(hŒ@http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git”h]”jÇ  )”}”(hj  h]”hŒ@http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”j  uh1jÆ  hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KMhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjú  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1jø  hŸh¶h KLhjo  hžhubh¸)”}”(hŒmThere is also a gitweb interface available at
http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git”h]”(hŒ.There is also a gitweb interface available at
”…””}”(hj>  hžhhŸNh NubjÇ  )”}”(hŒ?http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git”h]”hŒ?http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git”…””}”(hjF  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”jH  uh1jÆ  hj>  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KOhjo  hžhubh¸)”}”(hŒSMore information about kexec-tools can be found at
http://horms.net/projects/kexec/”h]”(hŒ3More information about kexec-tools can be found at
”…””}”(hj[  hžhhŸNh NubjÇ  )”}”(hŒ http://horms.net/projects/kexec/”h]”hŒ http://horms.net/projects/kexec/”…””}”(hjc  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”je  uh1jÆ  hj[  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KRhjo  hžhubj  )”}”(hhh]”(j†  )”}”(hŒYUnpack the tarball with the tar command, as follows::

     tar xvpzf kexec-tools.tar.gz
”h]”(h¸)”}”(hŒ5Unpack the tarball with the tar command, as follows::”h]”hŒ4Unpack the tarball with the tar command, as follows:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KUhj{  ubhŒliteral_block”“”)”}”(hŒtar xvpzf kexec-tools.tar.gz”h]”hŒtar xvpzf kexec-tools.tar.gz”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1j  hŸh¶h KWhj{  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjx  hžhhŸh¶h Nubj†  )”}”(hŒOChange to the kexec-tools directory, as follows::

     cd kexec-tools-VERSION
”h]”(h¸)”}”(hŒ1Change to the kexec-tools directory, as follows::”h]”hŒ0Change to the kexec-tools directory, as follows:”…””}”(hj©  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KYhj¥  ubjŽ  )”}”(hŒcd kexec-tools-VERSION”h]”hŒcd kexec-tools-VERSION”…””}”hj·  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K[hj¥  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjx  hžhhŸh¶h Nubj†  )”}”(hŒ6Configure the package, as follows::

     ./configure
”h]”(h¸)”}”(hŒ#Configure the package, as follows::”h]”hŒ"Configure the package, as follows:”…””}”(hjÏ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K]hjË  ubjŽ  )”}”(hŒ./configure”h]”hŒ./configure”…””}”hjÝ  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K_hjË  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjx  hžhhŸh¶h Nubj†  )”}”(hŒ-Compile the package, as follows::

     make
”h]”(h¸)”}”(hŒ!Compile the package, as follows::”h]”hŒ Compile the package, as follows:”…””}”(hjõ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kahjñ  ubjŽ  )”}”(hŒmake”h]”hŒmake”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Kchjñ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjx  hžhhŸh¶h Nubj†  )”}”(hŒ6Install the package, as follows::

     make install

”h]”(h¸)”}”(hŒ!Install the package, as follows::”h]”hŒ Install the package, as follows:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kehj  ubjŽ  )”}”(hŒmake install”h]”hŒmake install”…””}”hj)  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Kghj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjx  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  Œstart”Kuh1j€  hjo  hžhhŸh¶h KUubeh}”(h]”Œinstall-kexec-tools”ah ]”h"]”Œinstall kexec-tools”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h K@ubh¢)”}”(hhh]”(h§)”}”(hŒ)Build the system and dump-capture kernels”h]”hŒ)Build the system and dump-capture kernels”…””}”(hjO  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjL  hžhhŸh¶h Kkubh¸)”}”(hŒ.There are two possible methods of using Kdump.”h]”hŒ.There are two possible methods of using Kdump.”…””}”(hj]  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KlhjL  hžhubj  )”}”(hhh]”(j†  )”}”(hŒPBuild a separate custom dump-capture kernel for capturing the
kernel core dump.
”h]”h¸)”}”(hŒOBuild a separate custom dump-capture kernel for capturing the
kernel core dump.”h]”hŒOBuild a separate custom dump-capture kernel for capturing the
kernel core dump.”…””}”(hjr  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Knhjn  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjk  hžhhŸh¶h Nubj†  )”}”(hX'  Or use the system kernel binary itself as dump-capture kernel and there is
no need to build a separate dump-capture kernel. This is possible
only with the architectures which support a relocatable kernel. As
of today, i386, x86_64, ppc64, arm and arm64 architectures support
relocatable kernel.
”h]”h¸)”}”(hX&  Or use the system kernel binary itself as dump-capture kernel and there is
no need to build a separate dump-capture kernel. This is possible
only with the architectures which support a relocatable kernel. As
of today, i386, x86_64, ppc64, arm and arm64 architectures support
relocatable kernel.”h]”hX&  Or use the system kernel binary itself as dump-capture kernel and there is
no need to build a separate dump-capture kernel. This is possible
only with the architectures which support a relocatable kernel. As
of today, i386, x86_64, ppc64, arm and arm64 architectures support
relocatable kernel.”…””}”(hjŠ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kqhj†  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjk  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hjL  hžhhŸh¶h Knubh¸)”}”(hŒíBuilding a relocatable kernel is advantageous from the point of view that
one does not have to build a second kernel for capturing the dump. But
at the same time one might want to build a custom dump capture kernel
suitable to his needs.”h]”hŒíBuilding a relocatable kernel is advantageous from the point of view that
one does not have to build a second kernel for capturing the dump. But
at the same time one might want to build a custom dump capture kernel
suitable to his needs.”…””}”(hj¤  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KwhjL  hžhubh¸)”}”(hŒpFollowing are the configuration setting required for system and
dump-capture kernels for enabling kdump support.”h]”hŒpFollowing are the configuration setting required for system and
dump-capture kernels for enabling kdump support.”…””}”(hj²  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K|hjL  hžhubeh}”(h]”Œ)build-the-system-and-dump-capture-kernels”ah ]”h"]”Œ)build the system and dump-capture kernels”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h Kkubh¢)”}”(hhh]”(h§)”}”(hŒSystem kernel config options”h]”hŒSystem kernel config options”…””}”(hjË  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjÈ  hžhhŸh¶h K€ubj  )”}”(hhh]”(j†  )”}”(hŒÒEnable "kexec system call" or "kexec file based system call" in
"Processor type and features."::

     CONFIG_KEXEC=y or CONFIG_KEXEC_FILE=y

And both of them will select KEXEC_CORE::

     CONFIG_KEXEC_CORE=y
”h]”(h¸)”}”(hŒ`Enable "kexec system call" or "kexec file based system call" in
"Processor type and features."::”h]”hŒkEnable â€œkexec system callâ€ or â€œkexec file based system callâ€ in
â€œProcessor type and features.â€:”…””}”(hjà  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K‚hjÜ  ubjŽ  )”}”(hŒ%CONFIG_KEXEC=y or CONFIG_KEXEC_FILE=y”h]”hŒ%CONFIG_KEXEC=y or CONFIG_KEXEC_FILE=y”…””}”hjî  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K…hjÜ  ubh¸)”}”(hŒ)And both of them will select KEXEC_CORE::”h]”hŒ(And both of them will select KEXEC_CORE:”…””}”(hjü  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K‡hjÜ  ubjŽ  )”}”(hŒCONFIG_KEXEC_CORE=y”h]”hŒCONFIG_KEXEC_CORE=y”…””}”hj
  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K‰hjÜ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÙ  hžhhŸh¶h Nubj†  )”}”(hX·  Enable "sysfs file system support" in "Filesystem" -> "Pseudo
filesystems." This is usually enabled by default::

     CONFIG_SYSFS=y

Note that "sysfs file system support" might not appear in the "Pseudo
filesystems" menu if "Configure standard kernel features (expert users)"
is not enabled in "General Setup." In this case, check the .config file
itself to ensure that sysfs is turned on, as follows::

     grep 'CONFIG_SYSFS' .config
”h]”(h¸)”}”(hŒpEnable "sysfs file system support" in "Filesystem" -> "Pseudo
filesystems." This is usually enabled by default::”h]”hŒ{Enable â€œsysfs file system supportâ€ in â€œFilesystemâ€ -> â€œPseudo
filesystems.â€ This is usually enabled by default:”…””}”(hj"  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K‹hj  ubjŽ  )”}”(hŒCONFIG_SYSFS=y”h]”hŒCONFIG_SYSFS=y”…””}”hj0  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h KŽhj  ubh¸)”}”(hX  Note that "sysfs file system support" might not appear in the "Pseudo
filesystems" menu if "Configure standard kernel features (expert users)"
is not enabled in "General Setup." In this case, check the .config file
itself to ensure that sysfs is turned on, as follows::”h]”hX  Note that â€œsysfs file system supportâ€ might not appear in the â€œPseudo
filesystemsâ€ menu if â€œConfigure standard kernel features (expert users)â€
is not enabled in â€œGeneral Setup.â€ In this case, check the .config file
itself to ensure that sysfs is turned on, as follows:”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khj  ubjŽ  )”}”(hŒgrep 'CONFIG_SYSFS' .config”h]”hŒgrep 'CONFIG_SYSFS' .config”…””}”hjL  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K•hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÙ  hžhhŸh¶h Nubj†  )”}”(hŒüEnable "Compile the kernel with debug info" in "Kernel hacking."::

     CONFIG_DEBUG_INFO=Y

This causes the kernel to be built with debug symbols. The dump
analysis tools require a vmlinux with debug symbols in order to read
and analyze a dump file.
”h]”(h¸)”}”(hŒBEnable "Compile the kernel with debug info" in "Kernel hacking."::”h]”hŒIEnable â€œCompile the kernel with debug infoâ€ in â€œKernel hacking.â€:”…””}”(hjd  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K—hj`  ubjŽ  )”}”(hŒCONFIG_DEBUG_INFO=Y”h]”hŒCONFIG_DEBUG_INFO=Y”…””}”hjr  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K™hj`  ubh¸)”}”(hŒThis causes the kernel to be built with debug symbols. The dump
analysis tools require a vmlinux with debug symbols in order to read
and analyze a dump file.”h]”hŒThis causes the kernel to be built with debug symbols. The dump
analysis tools require a vmlinux with debug symbols in order to read
and analyze a dump file.”…””}”(hj€  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K›hj`  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÙ  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hjÈ  hžhhŸh¶h K‚ubeh}”(h]”Œsystem-kernel-config-options”ah ]”h"]”Œsystem kernel config options”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h K€ubh¢)”}”(hhh]”(h§)”}”(hŒ5Dump-capture kernel config options (Arch Independent)”h]”hŒ5Dump-capture kernel config options (Arch Independent)”…””}”(hj¥  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj¢  hžhhŸh¶h K ubj  )”}”(hhh]”(j†  )”}”(hŒÐEnable "kernel crash dumps" support under "Processor type and
features"::

     CONFIG_CRASH_DUMP=y

And this will select VMCORE_INFO and CRASH_RESERVE::
     CONFIG_VMCORE_INFO=y
     CONFIG_CRASH_RESERVE=y
”h]”(h¸)”}”(hŒIEnable "kernel crash dumps" support under "Processor type and
features"::”h]”hŒPEnable â€œkernel crash dumpsâ€ support under â€œProcessor type and
featuresâ€:”…””}”(hjº  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¢hj¶  ubjŽ  )”}”(hŒCONFIG_CRASH_DUMP=y”h]”hŒCONFIG_CRASH_DUMP=y”…””}”hjÈ  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K¥hj¶  ubhŒdefinition_list”“”)”}”(hhh]”hŒdefinition_list_item”“”)”}”(hŒaAnd this will select VMCORE_INFO and CRASH_RESERVE::
CONFIG_VMCORE_INFO=y
CONFIG_CRASH_RESERVE=y
”h]”(hŒterm”“”)”}”(hŒ4And this will select VMCORE_INFO and CRASH_RESERVE::”h]”hŒ4And this will select VMCORE_INFO and CRASH_RESERVE::”…””}”(hjã  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1já  hŸh¶h K©hjÝ  ubhŒ
definition”“”)”}”(hhh]”h¸)”}”(hŒ+CONFIG_VMCORE_INFO=y
CONFIG_CRASH_RESERVE=y”h]”hŒ+CONFIG_VMCORE_INFO=y
CONFIG_CRASH_RESERVE=y”…””}”(hjö  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¨hjó  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jñ  hjÝ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jÛ  hŸh¶h K©hjØ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj¶  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj³  hžhhŸNh Nubj†  )”}”(hŒ³Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::

     CONFIG_PROC_VMCORE=y

(CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
”h]”(h¸)”}”(hŒKEnable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::”h]”hŒVEnable â€œ/proc/vmcore supportâ€ under â€œFilesystemsâ€ -> â€œPseudo filesystemsâ€:”…””}”(hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K«hj  ubjŽ  )”}”(hŒCONFIG_PROC_VMCORE=y”h]”hŒCONFIG_PROC_VMCORE=y”…””}”hj.  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K­hj  ubh¸)”}”(hŒJ(CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)”h]”hŒJ(CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)”…””}”(hj<  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¯hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj³  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hj¢  hžhhŸh¶h K¢ubeh}”(h]”Œ3dump-capture-kernel-config-options-arch-independent”ah ]”h"]”Œ5dump-capture kernel config options (arch independent)”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h K ubh¢)”}”(hhh]”(h§)”}”(hŒDDump-capture kernel config options (Arch Dependent, i386 and x86_64)”h]”hŒDDump-capture kernel config options (Arch Dependent, i386 and x86_64)”…””}”(hja  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj^  hžhhŸh¶h K²ubj  )”}”(hhh]”(j†  )”}”(hŒaOn i386, enable high memory support under "Processor type and
features"::

     CONFIG_HIGHMEM4G
”h]”(h¸)”}”(hŒIOn i386, enable high memory support under "Processor type and
features"::”h]”hŒLOn i386, enable high memory support under â€œProcessor type and
featuresâ€:”…””}”(hjv  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K´hjr  ubjŽ  )”}”(hŒCONFIG_HIGHMEM4G”h]”hŒCONFIG_HIGHMEM4G”…””}”hj„  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h K·hjr  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjo  hžhhŸh¶h Nubj†  )”}”(hXP  With CONFIG_SMP=y, usually nr_cpus=1 need specified on the kernel
command line when loading the dump-capture kernel because one
CPU is enough for kdump kernel to dump vmcore on most of systems.

However, you can also specify nr_cpus=X to enable multiple processors
in kdump kernel.

With CONFIG_SMP=n, the above things are not related.
”h]”(h¸)”}”(hŒÁWith CONFIG_SMP=y, usually nr_cpus=1 need specified on the kernel
command line when loading the dump-capture kernel because one
CPU is enough for kdump kernel to dump vmcore on most of systems.”h]”hŒÁWith CONFIG_SMP=y, usually nr_cpus=1 need specified on the kernel
command line when loading the dump-capture kernel because one
CPU is enough for kdump kernel to dump vmcore on most of systems.”…””}”(hjœ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K¹hj˜  ubh¸)”}”(hŒVHowever, you can also specify nr_cpus=X to enable multiple processors
in kdump kernel.”h]”hŒVHowever, you can also specify nr_cpus=X to enable multiple processors
in kdump kernel.”…””}”(hjª  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K½hj˜  ubh¸)”}”(hŒ4With CONFIG_SMP=n, the above things are not related.”h]”hŒ4With CONFIG_SMP=n, the above things are not related.”…””}”(hj¸  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÀhj˜  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjo  hžhhŸh¶h Nubj†  )”}”(hŒ³A relocatable kernel is suggested to be built by default. If not yet,
enable "Build a relocatable kernel" support under "Processor type and
features"::

     CONFIG_RELOCATABLE=y
”h]”(h¸)”}”(hŒ—A relocatable kernel is suggested to be built by default. If not yet,
enable "Build a relocatable kernel" support under "Processor type and
features"::”h]”hŒžA relocatable kernel is suggested to be built by default. If not yet,
enable â€œBuild a relocatable kernelâ€ support under â€œProcessor type and
featuresâ€:”…””}”(hjÐ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÂhjÌ  ubjŽ  )”}”(hŒCONFIG_RELOCATABLE=y”h]”hŒCONFIG_RELOCATABLE=y”…””}”hjÞ  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h KÆhjÌ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjo  hžhhŸh¶h Nubj†  )”}”(hX  Use a suitable value for "Physical address where the kernel is
loaded" (under "Processor type and features"). This only appears when
"kernel crash dumps" is enabled. A suitable value depends upon
whether kernel is relocatable or not.

If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
This will compile the kernel for physical address 1MB, but given the fact
kernel is relocatable, it can be run from any physical address hence
kexec boot loader will load it in memory region reserved for dump-capture
kernel.

Otherwise it should be the start of memory region reserved for
second kernel using boot parameter "crashkernel=Y@X". Here X is
start of memory region reserved for dump-capture kernel.
Generally X is 16MB (0x1000000). So you can set
CONFIG_PHYSICAL_START=0x1000000
”h]”(h¸)”}”(hŒéUse a suitable value for "Physical address where the kernel is
loaded" (under "Processor type and features"). This only appears when
"kernel crash dumps" is enabled. A suitable value depends upon
whether kernel is relocatable or not.”h]”hŒõUse a suitable value for â€œPhysical address where the kernel is
loadedâ€ (under â€œProcessor type and featuresâ€). This only appears when
â€œkernel crash dumpsâ€ is enabled. A suitable value depends upon
whether kernel is relocatable or not.”…””}”(hjö  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÈhjò  ubh¸)”}”(hX)  If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
This will compile the kernel for physical address 1MB, but given the fact
kernel is relocatable, it can be run from any physical address hence
kexec boot loader will load it in memory region reserved for dump-capture
kernel.”h]”hX)  If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
This will compile the kernel for physical address 1MB, but given the fact
kernel is relocatable, it can be run from any physical address hence
kexec boot loader will load it in memory region reserved for dump-capture
kernel.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÍhjò  ubh¸)”}”(hX  Otherwise it should be the start of memory region reserved for
second kernel using boot parameter "crashkernel=Y@X". Here X is
start of memory region reserved for dump-capture kernel.
Generally X is 16MB (0x1000000). So you can set
CONFIG_PHYSICAL_START=0x1000000”h]”hX  Otherwise it should be the start of memory region reserved for
second kernel using boot parameter â€œcrashkernel=Y@Xâ€. Here X is
start of memory region reserved for dump-capture kernel.
Generally X is 16MB (0x1000000). So you can set
CONFIG_PHYSICAL_START=0x1000000”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÓhjò  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjo  hžhhŸh¶h Nubj†  )”}”(hŒlMake and install the kernel and its modules. DO NOT add this kernel
to the boot loader configuration files.
”h]”h¸)”}”(hŒkMake and install the kernel and its modules. DO NOT add this kernel
to the boot loader configuration files.”h]”hŒkMake and install the kernel and its modules. DO NOT add this kernel
to the boot loader configuration files.”…””}”(hj*  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KÙhj&  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjo  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hj^  hžhhŸh¶h K´ubeh}”(h]”ŒAdump-capture-kernel-config-options-arch-dependent-i386-and-x86-64”ah ]”h"]”ŒDdump-capture kernel config options (arch dependent, i386 and x86_64)”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h K²ubh¢)”}”(hhh]”(h§)”}”(hŒ:Dump-capture kernel config options (Arch Dependent, ppc64)”h]”hŒ:Dump-capture kernel config options (Arch Dependent, ppc64)”…””}”(hjO  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjL  hžhhŸh¶h KÝubj  )”}”(hhh]”(j†  )”}”(hŒ_Enable "Build a kdump crash kernel" support under "Kernel" options::

     CONFIG_CRASH_DUMP=y
”h]”(h¸)”}”(hŒDEnable "Build a kdump crash kernel" support under "Kernel" options::”h]”hŒKEnable â€œBuild a kdump crash kernelâ€ support under â€œKernelâ€ options:”…””}”(hjd  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kßhj`  ubjŽ  )”}”(hŒCONFIG_CRASH_DUMP=y”h]”hŒCONFIG_CRASH_DUMP=y”…””}”hjr  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Káhj`  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj]  hžhhŸh¶h Nubj†  )”}”(hŒGEnable "Build a relocatable kernel" support::

   CONFIG_RELOCATABLE=y
”h]”(h¸)”}”(hŒ-Enable "Build a relocatable kernel" support::”h]”hŒ0Enable â€œBuild a relocatable kernelâ€ support:”…””}”(hjŠ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kãhj†  ubjŽ  )”}”(hŒCONFIG_RELOCATABLE=y”h]”hŒCONFIG_RELOCATABLE=y”…””}”hj˜  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Kåhj†  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj]  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hjL  hžhhŸh¶h KßubhŒblock_quote”“”)”}”(hŒ-Make and install the kernel and its modules.
”h]”h¸)”}”(hŒ,Make and install the kernel and its modules.”h]”hŒ,Make and install the kernel and its modules.”…””}”(hj¸  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kçhj´  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h KçhjL  hžhubeh}”(h]”Œ7dump-capture-kernel-config-options-arch-dependent-ppc64”ah ]”h"]”Œ:dump-capture kernel config options (arch dependent, ppc64)”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h KÝubh¢)”}”(hhh]”(h§)”}”(hŒ8Dump-capture kernel config options (Arch Dependent, arm)”h]”hŒ8Dump-capture kernel config options (Arch Dependent, arm)”…””}”(hj×  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjÔ  hžhhŸh¶h Kêubjù  )”}”(hhh]”j†  )”}”(hŒhTo use a relocatable kernel,
Enable "AUTO_ZRELADDR" support under "Boot" options::

    AUTO_ZRELADDR=y
”h]”(h¸)”}”(hŒRTo use a relocatable kernel,
Enable "AUTO_ZRELADDR" support under "Boot" options::”h]”hŒYTo use a relocatable kernel,
Enable â€œAUTO_ZRELADDRâ€ support under â€œBootâ€ options:”…””}”(hjì  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kìhjè  ubjŽ  )”}”(hŒAUTO_ZRELADDR=y”h]”hŒAUTO_ZRELADDR=y”…””}”hjú  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Kïhjè  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjå  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j<  j=  uh1jø  hŸh¶h KìhjÔ  hžhubeh}”(h]”Œ5dump-capture-kernel-config-options-arch-dependent-arm”ah ]”h"]”Œ8dump-capture kernel config options (arch dependent, arm)”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h Kêubh¢)”}”(hhh]”(h§)”}”(hŒ:Dump-capture kernel config options (Arch Dependent, arm64)”h]”hŒ:Dump-capture kernel config options (Arch Dependent, arm64)”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h Kòubjù  )”}”(hhh]”j†  )”}”(hŒ¬Please note that kvm of the dump-capture kernel will not be enabled
on non-VHE systems even if it is configured. This is because the CPU
will not be reset to EL2 on panic.
”h]”h¸)”}”(hŒ«Please note that kvm of the dump-capture kernel will not be enabled
on non-VHE systems even if it is configured. This is because the CPU
will not be reset to EL2 on panic.”h]”hŒ«Please note that kvm of the dump-capture kernel will not be enabled
on non-VHE systems even if it is configured. This is because the CPU
will not be reset to EL2 on panic.”…””}”(hj4  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kôhj0  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj-  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j<  j=  uh1jø  hŸh¶h Kôhj  hžhubeh}”(h]”Œ7dump-capture-kernel-config-options-arch-dependent-arm64”ah ]”h"]”Œ:dump-capture kernel config options (arch dependent, arm64)”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h Kòubeh}”(h]”Œsetup-and-installation”ah ]”h"]”Œsetup and installation”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K=ubh¢)”}”(hhh]”(h§)”}”(hŒcrashkernel syntax”h]”hŒcrashkernel syntax”…””}”(hja  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj^  hžhhŸh¶h Kùubj  )”}”(hhh]”(j†  )”}”(hX   crashkernel=size@offset

Here 'size' specifies how much memory to reserve for the dump-capture kernel
and 'offset' specifies the beginning of this reserved memory. For example,
"crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
starting at physical address 0x01000000 (16MB) for the dump-capture kernel.

The crashkernel region can be automatically placed by the system
kernel at run time. This is done by specifying the base address as 0,
or omitting it all together::

      crashkernel=256M@0

or::

      crashkernel=256M

If the start address is specified, note that the start address of the
kernel will be aligned to a value (which is Arch dependent), so if the
start address is not then any space below the alignment point will be
wasted.
”h]”(h¸)”}”(hŒcrashkernel=size@offset”h]”jÇ  )”}”(hjx  h]”hŒcrashkernel=size@offset”…””}”(hjz  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:crashkernel=size@offset”uh1jÆ  hjv  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kúhjr  ubh¸)”}”(hX,  Here 'size' specifies how much memory to reserve for the dump-capture kernel
and 'offset' specifies the beginning of this reserved memory. For example,
"crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
starting at physical address 0x01000000 (16MB) for the dump-capture kernel.”h]”(hŒ£Here â€˜sizeâ€™ specifies how much memory to reserve for the dump-capture kernel
and â€˜offsetâ€™ specifies the beginning of this reserved memory. For example,
â€œ”…””}”(hj  hžhhŸNh NubjÇ  )”}”(hŒcrashkernel=64M@16M”h]”hŒcrashkernel=64M@16M”…””}”(hj—  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:crashkernel=64M@16M”uh1jÆ  hj  ubhŒ‚â€ tells the system kernel to reserve 64 MB of memory
starting at physical address 0x01000000 (16MB) for the dump-capture kernel.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Kühjr  ubh¸)”}”(hŒ¤The crashkernel region can be automatically placed by the system
kernel at run time. This is done by specifying the base address as 0,
or omitting it all together::”h]”hŒ£The crashkernel region can be automatically placed by the system
kernel at run time. This is done by specifying the base address as 0,
or omitting it all together:”…””}”(hj±  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjr  ubjŽ  )”}”(hŒcrashkernel=256M@0”h]”hŒcrashkernel=256M@0”…””}”hj¿  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Mhjr  ubh¸)”}”(hŒor::”h]”hŒor:”…””}”(hjÍ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjr  ubjŽ  )”}”(hŒcrashkernel=256M”h]”hŒcrashkernel=256M”…””}”hjÛ  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h M	hjr  ubh¸)”}”(hŒÚIf the start address is specified, note that the start address of the
kernel will be aligned to a value (which is Arch dependent), so if the
start address is not then any space below the alignment point will be
wasted.”h]”hŒÚIf the start address is specified, note that the start address of the
kernel will be aligned to a value (which is Arch dependent), so if the
start address is not then any space below the alignment point will be
wasted.”…””}”(hjé  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjr  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjo  hžhhŸh¶h Nubj†  )”}”(hX  range1:size1[,range2:size2,...][@offset]

While the "crashkernel=size[@offset]" syntax is sufficient for most
configurations, sometimes it's handy to have the reserved memory dependent
on the value of System RAM -- that's mostly for distributors that pre-setup
the kernel command line to avoid a unbootable system after some memory has
been removed from the machine.

The syntax is::

    crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
    range=start-[end]

For example::

    crashkernel=512M-2G:64M,2G-:128M

This would mean:

    1) if the RAM is smaller than 512M, then don't reserve anything
       (this is the "rescue" case)
    2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
    3) if the RAM size is larger than 2G, then reserve 128M
”h]”(h¸)”}”(hŒ(range1:size1[,range2:size2,...][@offset]”h]”hŒ(range1:size1[,range2:size2,...][@offset]”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjý  ubh¸)”}”(hXD  While the "crashkernel=size[@offset]" syntax is sufficient for most
configurations, sometimes it's handy to have the reserved memory dependent
on the value of System RAM -- that's mostly for distributors that pre-setup
the kernel command line to avoid a unbootable system after some memory has
been removed from the machine.”h]”hXL  While the â€œcrashkernel=size[@offset]â€ syntax is sufficient for most
configurations, sometimes itâ€™s handy to have the reserved memory dependent
on the value of System RAM -- thatâ€™s mostly for distributors that pre-setup
the kernel command line to avoid a unbootable system after some memory has
been removed from the machine.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjý  ubh¸)”}”(hŒThe syntax is::”h]”hŒThe syntax is:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjý  ubjŽ  )”}”(hŒNcrashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
range=start-[end]”h]”hŒNcrashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
range=start-[end]”…””}”hj+  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Mhjý  ubh¸)”}”(hŒFor example::”h]”hŒFor example:”…””}”(hj9  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjý  ubjŽ  )”}”(hŒ crashkernel=512M-2G:64M,2G-:128M”h]”hŒ crashkernel=512M-2G:64M,2G-:128M”…””}”hjG  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Mhjý  ubh¸)”}”(hŒThis would mean:”h]”hŒThis would mean:”…””}”(hjU  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M!hjý  ubj³  )”}”(hŒß1) if the RAM is smaller than 512M, then don't reserve anything
   (this is the "rescue" case)
2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
3) if the RAM size is larger than 2G, then reserve 128M
”h]”j  )”}”(hhh]”(j†  )”}”(hŒXif the RAM is smaller than 512M, then don't reserve anything
(this is the "rescue" case)”h]”h¸)”}”(hŒXif the RAM is smaller than 512M, then don't reserve anything
(this is the "rescue" case)”h]”hŒ^if the RAM is smaller than 512M, then donâ€™t reserve anything
(this is the â€œrescueâ€ case)”…””}”(hjn  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M#hjj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjg  ubj†  )”}”(hŒDif the RAM size is between 512M and 2G (exclusive), then reserve 64M”h]”h¸)”}”(hj„  h]”hŒDif the RAM size is between 512M and 2G (exclusive), then reserve 64M”…””}”(hj†  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M%hj‚  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjg  ubj†  )”}”(hŒ5if the RAM size is larger than 2G, then reserve 128M
”h]”h¸)”}”(hŒ4if the RAM size is larger than 2G, then reserve 128M”h]”hŒ4if the RAM size is larger than 2G, then reserve 128M”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M&hj™  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjg  ubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hjc  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h M#hjý  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjo  hžhhŸh¶h Nubj†  )”}”(hXð  crashkernel=size,high and crashkernel=size,low

If memory above 4G is preferred, crashkernel=size,high can be used to
fulfill that. With it, physical memory is allowed to be allocated from top,
so could be above 4G if system has more than 4G RAM installed. Otherwise,
memory region will be allocated below 4G if available.

When crashkernel=X,high is passed, kernel could allocate physical memory
region above 4G, low memory under 4G is needed in this case. There are
three ways to get low memory:

   1) Kernel will allocate at least 256M memory below 4G automatically
      if crashkernel=Y,low is not specified.
   2) Let user specify low memory size instead.
   3) Specified value 0 will disable low memory allocation::

         crashkernel=0,low
”h]”(h¸)”}”(hŒ.crashkernel=size,high and crashkernel=size,low”h]”hŒ.crashkernel=size,high and crashkernel=size,low”…””}”(hjÇ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M(hjÃ  ubh¸)”}”(hX  If memory above 4G is preferred, crashkernel=size,high can be used to
fulfill that. With it, physical memory is allowed to be allocated from top,
so could be above 4G if system has more than 4G RAM installed. Otherwise,
memory region will be allocated below 4G if available.”h]”hX  If memory above 4G is preferred, crashkernel=size,high can be used to
fulfill that. With it, physical memory is allowed to be allocated from top,
so could be above 4G if system has more than 4G RAM installed. Otherwise,
memory region will be allocated below 4G if available.”…””}”(hjÕ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M*hjÃ  ubh¸)”}”(hŒ­When crashkernel=X,high is passed, kernel could allocate physical memory
region above 4G, low memory under 4G is needed in this case. There are
three ways to get low memory:”h]”hŒ­When crashkernel=X,high is passed, kernel could allocate physical memory
region above 4G, low memory under 4G is needed in this case. There are
three ways to get low memory:”…””}”(hjã  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M/hjÃ  ubj³  )”}”(hŒî1) Kernel will allocate at least 256M memory below 4G automatically
   if crashkernel=Y,low is not specified.
2) Let user specify low memory size instead.
3) Specified value 0 will disable low memory allocation::

      crashkernel=0,low
”h]”j  )”}”(hhh]”(j†  )”}”(hŒgKernel will allocate at least 256M memory below 4G automatically
if crashkernel=Y,low is not specified.”h]”h¸)”}”(hŒgKernel will allocate at least 256M memory below 4G automatically
if crashkernel=Y,low is not specified.”h]”hŒgKernel will allocate at least 256M memory below 4G automatically
if crashkernel=Y,low is not specified.”…””}”(hjü  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M3hjø  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjõ  ubj†  )”}”(hŒ)Let user specify low memory size instead.”h]”h¸)”}”(hj	  h]”hŒ)Let user specify low memory size instead.”…””}”(hj	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M5hj	  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjõ  ubj†  )”}”(hŒMSpecified value 0 will disable low memory allocation::

   crashkernel=0,low
”h]”(h¸)”}”(hŒ6Specified value 0 will disable low memory allocation::”h]”hŒ5Specified value 0 will disable low memory allocation:”…””}”(hj+	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M6hj'	  ubjŽ  )”}”(hŒcrashkernel=0,low”h]”hŒcrashkernel=0,low”…””}”hj9	  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h M8hj'	  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjõ  ubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hjñ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h M3hjÃ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjo  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hj^  hžhhŸh¶h Kúubh¢)”}”(hhh]”(h§)”}”(hŒBoot into System Kernel”h]”hŒBoot into System Kernel”…””}”(hjh	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hje	  hžhhŸh¶h M;ubj  )”}”(hhh]”(j†  )”}”(hŒYUpdate the boot loader (such as grub, yaboot, or lilo) configuration
files as necessary.
”h]”h¸)”}”(hŒXUpdate the boot loader (such as grub, yaboot, or lilo) configuration
files as necessary.”h]”hŒXUpdate the boot loader (such as grub, yaboot, or lilo) configuration
files as necessary.”…””}”(hj}	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M<hjy	  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjv	  hžhhŸh¶h Nubj†  )”}”(hX"  Boot the system kernel with the boot parameter "crashkernel=Y@X".

On x86 and x86_64, use "crashkernel=Y[@X]". Most of the time, the
start address 'X' is not necessary, kernel will search a suitable
area. Unless an explicit start address is expected.

On ppc64, use "crashkernel=128M@32M".

On s390x, typically use "crashkernel=xxM". The value of xx is dependent
on the memory consumption of the kdump system. In general this is not
dependent on the memory size of the production system.

On arm, the use of "crashkernel=Y@X" is no longer necessary; the
kernel will automatically locate the crash kernel image within the
first 512MB of RAM if X is not given.

On arm64, use "crashkernel=Y[@X]".  Note that the start address of
the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
”h]”(h¸)”}”(hŒABoot the system kernel with the boot parameter "crashkernel=Y@X".”h]”hŒEBoot the system kernel with the boot parameter â€œcrashkernel=Y@Xâ€.”…””}”(hj•	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M?hj‘	  ubh¸)”}”(hŒ·On x86 and x86_64, use "crashkernel=Y[@X]". Most of the time, the
start address 'X' is not necessary, kernel will search a suitable
area. Unless an explicit start address is expected.”h]”hŒ¿On x86 and x86_64, use â€œcrashkernel=Y[@X]â€. Most of the time, the
start address â€˜Xâ€™ is not necessary, kernel will search a suitable
area. Unless an explicit start address is expected.”…””}”(hj£	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MAhj‘	  ubh¸)”}”(hŒ%On ppc64, use "crashkernel=128M@32M".”h]”(hŒOn ppc64, use â€œ”…””}”(hj±	  hžhhŸNh NubjÇ  )”}”(hŒcrashkernel=128M@32M”h]”hŒcrashkernel=128M@32M”…””}”(hj¹	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:crashkernel=128M@32M”uh1jÆ  hj±	  ubhŒâ€.”…””}”(hj±	  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MEhj‘	  ubh¸)”}”(hŒÄOn s390x, typically use "crashkernel=xxM". The value of xx is dependent
on the memory consumption of the kdump system. In general this is not
dependent on the memory size of the production system.”h]”hŒÈOn s390x, typically use â€œcrashkernel=xxMâ€. The value of xx is dependent
on the memory consumption of the kdump system. In general this is not
dependent on the memory size of the production system.”…””}”(hjÓ	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MGhj‘	  ubh¸)”}”(hŒ©On arm, the use of "crashkernel=Y@X" is no longer necessary; the
kernel will automatically locate the crash kernel image within the
first 512MB of RAM if X is not given.”h]”hŒ­On arm, the use of â€œcrashkernel=Y@Xâ€ is no longer necessary; the
kernel will automatically locate the crash kernel image within the
first 512MB of RAM if X is not given.”…””}”(hjá	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MKhj‘	  ubh¸)”}”(hŒOn arm64, use "crashkernel=Y[@X]".  Note that the start address of
the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).”h]”hŒ‘On arm64, use â€œcrashkernel=Y[@X]â€.  Note that the start address of
the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).”…””}”(hjï	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MOhj‘	  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjv	  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j½  j¾  j¿  hjÀ  jÁ  uh1j€  hje	  hžhhŸh¶h M<ubeh}”(h]”Œboot-into-system-kernel”ah ]”h"]”Œboot into system kernel”ah$]”h&]”uh1h¡hj^  hžhhŸh¶h M;ubeh}”(h]”Œcrashkernel-syntax”ah ]”h"]”Œcrashkernel syntax”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kùubh¢)”}”(hhh]”(h§)”}”(hŒLoad the Dump-capture Kernel”h]”hŒLoad the Dump-capture Kernel”…””}”(hj
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj
  hžhhŸh¶h MSubh¸)”}”(hŒKAfter booting to the system kernel, dump-capture kernel needs to be
loaded.”h]”hŒKAfter booting to the system kernel, dump-capture kernel needs to be
loaded.”…””}”(hj*
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MUhj
  hžhubh¸)”}”(hŒÁBased on the architecture and type of image (relocatable or not), one
can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
of dump-capture kernel. Following is the summary.”h]”hŒÁBased on the architecture and type of image (relocatable or not), one
can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
of dump-capture kernel. Following is the summary.”…””}”(hj8
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MXhj
  hžhubh¸)”}”(hŒFor i386 and x86_64:”h]”hŒFor i386 and x86_64:”…””}”(hjF
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M\hj
  hžhubj³  )”}”(hŒ\- Use bzImage/vmlinuz if kernel is relocatable.
- Use vmlinux if kernel is not relocatable.
”h]”jù  )”}”(hhh]”(j†  )”}”(hŒ-Use bzImage/vmlinuz if kernel is relocatable.”h]”h¸)”}”(hj]
  h]”hŒ-Use bzImage/vmlinuz if kernel is relocatable.”…””}”(hj_
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M^hj[
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjX
  ubj†  )”}”(hŒ*Use vmlinux if kernel is not relocatable.
”h]”h¸)”}”(hŒ)Use vmlinux if kernel is not relocatable.”h]”hŒ)Use vmlinux if kernel is not relocatable.”…””}”(hjv
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M_hjr
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjX
  ubeh}”(h]”h ]”h"]”h$]”h&]”j<  j=  uh1jø  hŸh¶h M^hjT
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h M^hj
  hžhubh¸)”}”(hŒ
For ppc64:”h]”hŒ
For ppc64:”…””}”(hj–
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mahj
  hžhubj³  )”}”(hŒ- Use vmlinux
”h]”jù  )”}”(hhh]”j†  )”}”(hŒUse vmlinux
”h]”h¸)”}”(hŒUse vmlinux”h]”hŒUse vmlinux”…””}”(hj¯
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mchj«
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj¨
  ubah}”(h]”h ]”h"]”h$]”h&]”j<  j=  uh1jø  hŸh¶h Mchj¤
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h Mchj
  hžhubh¸)”}”(hŒ
For s390x:”h]”hŒ
For s390x:”…””}”(hjÏ
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mehj
  hžhubj³  )”}”(hŒ- Use image or bzImage
”h]”jù  )”}”(hhh]”j†  )”}”(hŒUse image or bzImage
”h]”h¸)”}”(hŒUse image or bzImage”h]”hŒUse image or bzImage”…””}”(hjè
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mghjä
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjá
  ubah}”(h]”h ]”h"]”h$]”h&]”j<  j=  uh1jø  hŸh¶h MghjÝ
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h Mghj
  hžhubh¸)”}”(hŒFor arm:”h]”hŒFor arm:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mihj
  hžhubj³  )”}”(hŒ- Use zImage
”h]”jù  )”}”(hhh]”j†  )”}”(hŒUse zImage
”h]”h¸)”}”(hŒ
Use zImage”h]”hŒ
Use zImage”…””}”(hj!  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mkhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hj  ubah}”(h]”h ]”h"]”h$]”h&]”j<  j=  uh1jø  hŸh¶h Mkhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h Mkhj
  hžhubh¸)”}”(hŒ
For arm64:”h]”hŒ
For arm64:”…””}”(hjA  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mmhj
  hžhubj³  )”}”(hŒ- Use vmlinux or Image
”h]”jù  )”}”(hhh]”j†  )”}”(hŒUse vmlinux or Image
”h]”h¸)”}”(hŒUse vmlinux or Image”h]”hŒUse vmlinux or Image”…””}”(hjZ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MohjV  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjS  ubah}”(h]”h ]”h"]”h$]”h&]”j<  j=  uh1jø  hŸh¶h MohjO  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h Mohj
  hžhubh¸)”}”(hŒgIf you are using an uncompressed vmlinux image then use following command
to load dump-capture kernel::”h]”hŒfIf you are using an uncompressed vmlinux image then use following command
to load dump-capture kernel:”…””}”(hjz  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mqhj
  hžhubjŽ  )”}”(hŒškexec -p <dump-capture-kernel-vmlinux-image> \
--initrd=<initrd-for-dump-capture-kernel> --args-linux \
--append="root=<root-dev> <arch-specific-options>"”h]”hŒškexec -p <dump-capture-kernel-vmlinux-image> \
--initrd=<initrd-for-dump-capture-kernel> --args-linux \
--append="root=<root-dev> <arch-specific-options>"”…””}”hjˆ  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Mthj
  hžhubh¸)”}”(hŒgIf you are using a compressed bzImage/vmlinuz, then use following command
to load dump-capture kernel::”h]”hŒfIf you are using a compressed bzImage/vmlinuz, then use following command
to load dump-capture kernel:”…””}”(hj–  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mxhj
  hžhubjŽ  )”}”(hŒ‡kexec -p <dump-capture-kernel-bzImage> \
--initrd=<initrd-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"”h]”hŒ‡kexec -p <dump-capture-kernel-bzImage> \
--initrd=<initrd-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"”…””}”hj¤  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h M{hj
  hžhubh¸)”}”(hŒ^If you are using a compressed zImage, then use following command
to load dump-capture kernel::”h]”hŒ]If you are using a compressed zImage, then use following command
to load dump-capture kernel:”…””}”(hj²  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj
  hžhubjŽ  )”}”(hŒ»kexec --type zImage -p <dump-capture-kernel-bzImage> \
--initrd=<initrd-for-dump-capture-kernel> \
--dtb=<dtb-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"”h]”hŒ»kexec --type zImage -p <dump-capture-kernel-bzImage> \
--initrd=<initrd-for-dump-capture-kernel> \
--dtb=<dtb-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"”…””}”hjÀ  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h M‚hj
  hžhubh¸)”}”(hŒ`If you are using an uncompressed Image, then use following command
to load dump-capture kernel::”h]”hŒ_If you are using an uncompressed Image, then use following command
to load dump-capture kernel:”…””}”(hjÎ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M‡hj
  hžhubjŽ  )”}”(hŒ…kexec -p <dump-capture-kernel-Image> \
--initrd=<initrd-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"”h]”hŒ…kexec -p <dump-capture-kernel-Image> \
--initrd=<initrd-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"”…””}”hjÜ  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h MŠhj
  hžhubh¸)”}”(hŒbFollowing are the arch specific command line options to be used while
loading dump-capture kernel.”h]”hŒbFollowing are the arch specific command line options to be used while
loading dump-capture kernel.”…””}”(hjê  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MŽhj
  hžhubh¸)”}”(hŒFor i386 and x86_64:”h]”hŒFor i386 and x86_64:”…””}”(hjø  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M‘hj
  hžhubj³  )”}”(hŒ$"1 irqpoll nr_cpus=1 reset_devices"
”h]”h¸)”}”(hŒ#"1 irqpoll nr_cpus=1 reset_devices"”h]”hŒ'â€œ1 irqpoll nr_cpus=1 reset_devicesâ€”…””}”(hj
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M“hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h M“hj
  hžhubh¸)”}”(hŒ
For ppc64:”h]”hŒ
For ppc64:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M•hj
  hžhubj³  )”}”(hŒ)"1 maxcpus=1 noirqdistrib reset_devices"
”h]”h¸)”}”(hŒ("1 maxcpus=1 noirqdistrib reset_devices"”h]”hŒ,â€œ1 maxcpus=1 noirqdistrib reset_devicesâ€”…””}”(hj0  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M—hj,  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h M—hj
  hžhubh¸)”}”(hŒ
For s390x:”h]”hŒ
For s390x:”…””}”(hjD  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M™hj
  hžhubj³  )”}”(hŒ$"1 nr_cpus=1 cgroup_disable=memory"
”h]”h¸)”}”(hŒ#"1 nr_cpus=1 cgroup_disable=memory"”h]”hŒ'â€œ1 nr_cpus=1 cgroup_disable=memoryâ€”…””}”(hjV  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M›hjR  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h M›hj
  hžhubh¸)”}”(hŒFor arm:”h]”hŒFor arm:”…””}”(hjj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj
  hžhubj³  )”}”(hŒ"1 maxcpus=1 reset_devices"
”h]”h¸)”}”(hŒ"1 maxcpus=1 reset_devices"”h]”hŒâ€œ1 maxcpus=1 reset_devicesâ€”…””}”(hj|  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MŸhjx  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h MŸhj
  hžhubh¸)”}”(hŒ
For arm64:”h]”hŒ
For arm64:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M¡hj
  hžhubj³  )”}”(hŒ"1 nr_cpus=1 reset_devices"
”h]”h¸)”}”(hŒ"1 nr_cpus=1 reset_devices"”h]”hŒâ€œ1 nr_cpus=1 reset_devicesâ€”…””}”(hj¢  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M£hjž  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h M£hj
  hžhubh¸)”}”(hŒ)Notes on loading the dump-capture kernel:”h]”hŒ)Notes on loading the dump-capture kernel:”…””}”(hj¶  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M¥hj
  hžhubjù  )”}”(hhh]”(j†  )”}”(hX½  By default, the ELF headers are stored in ELF64 format to support
systems with more than 4GB memory. On i386, kexec automatically checks if
the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
So, on non-PAE systems, ELF32 is always used.

The --elf32-core-headers option can be used to force the generation of ELF32
headers. This is necessary because GDB currently cannot open vmcore files
with ELF64 headers on 32-bit systems.
”h]”(h¸)”}”(hŒþBy default, the ELF headers are stored in ELF64 format to support
systems with more than 4GB memory. On i386, kexec automatically checks if
the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
So, on non-PAE systems, ELF32 is always used.”h]”hŒþBy default, the ELF headers are stored in ELF64 format to support
systems with more than 4GB memory. On i386, kexec automatically checks if
the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
So, on non-PAE systems, ELF32 is always used.”…””}”(hjË  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M§hjÇ  ubh¸)”}”(hŒ¼The --elf32-core-headers option can be used to force the generation of ELF32
headers. This is necessary because GDB currently cannot open vmcore files
with ELF64 headers on 32-bit systems.”h]”hŒ¼The --elf32-core-headers option can be used to force the generation of ELF32
headers. This is necessary because GDB currently cannot open vmcore files
with ELF64 headers on 32-bit systems.”…””}”(hjÙ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M¬hjÇ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÄ  hžhhŸh¶h Nubj†  )”}”(hŒyThe "irqpoll" boot parameter reduces driver initialization failures
due to shared interrupts in the dump-capture kernel.
”h]”h¸)”}”(hŒxThe "irqpoll" boot parameter reduces driver initialization failures
due to shared interrupts in the dump-capture kernel.”h]”hŒ|The â€œirqpollâ€ boot parameter reduces driver initialization failures
due to shared interrupts in the dump-capture kernel.”…””}”(hjñ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M°hjí  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÄ  hžhhŸh¶h Nubj†  )”}”(hŒpYou must specify <root-dev> in the format corresponding to the root
device name in the output of mount command.
”h]”h¸)”}”(hŒoYou must specify <root-dev> in the format corresponding to the root
device name in the output of mount command.”h]”hŒoYou must specify <root-dev> in the format corresponding to the root
device name in the output of mount command.”…””}”(hj	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M³hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÄ  hžhhŸh¶h Nubj†  )”}”(hŒ|Boot parameter "1" boots the dump-capture kernel into single-user
mode without networking. If you want networking, use "3".
”h]”h¸)”}”(hŒ{Boot parameter "1" boots the dump-capture kernel into single-user
mode without networking. If you want networking, use "3".”h]”hŒƒBoot parameter â€œ1â€ boots the dump-capture kernel into single-user
mode without networking. If you want networking, use â€œ3â€.”…””}”(hj!  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M¶hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÄ  hžhhŸh¶h Nubj†  )”}”(hXX  We generally don't have to bring up a SMP kernel just to capture the
dump. Hence generally it is useful either to build a UP dump-capture
kernel or specify maxcpus=1 option while loading dump-capture kernel.
Note, though maxcpus always works, you had better replace it with
nr_cpus to save memory if supported by the current ARCH, such as x86.
”h]”h¸)”}”(hXW  We generally don't have to bring up a SMP kernel just to capture the
dump. Hence generally it is useful either to build a UP dump-capture
kernel or specify maxcpus=1 option while loading dump-capture kernel.
Note, though maxcpus always works, you had better replace it with
nr_cpus to save memory if supported by the current ARCH, such as x86.”h]”hXY  We generally donâ€™t have to bring up a SMP kernel just to capture the
dump. Hence generally it is useful either to build a UP dump-capture
kernel or specify maxcpus=1 option while loading dump-capture kernel.
Note, though maxcpus always works, you had better replace it with
nr_cpus to save memory if supported by the current ARCH, such as x86.”…””}”(hj9  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M¹hj5  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÄ  hžhhŸh¶h Nubj†  )”}”(hXn  You should enable multi-cpu support in dump-capture kernel if you intend
to use multi-thread programs with it, such as parallel dump feature of
makedumpfile. Otherwise, the multi-thread program may have a great
performance degradation. To enable multi-cpu support, you should bring up an
SMP dump-capture kernel and specify maxcpus/nr_cpus options while loading it.
”h]”h¸)”}”(hXm  You should enable multi-cpu support in dump-capture kernel if you intend
to use multi-thread programs with it, such as parallel dump feature of
makedumpfile. Otherwise, the multi-thread program may have a great
performance degradation. To enable multi-cpu support, you should bring up an
SMP dump-capture kernel and specify maxcpus/nr_cpus options while loading it.”h]”hXm  You should enable multi-cpu support in dump-capture kernel if you intend
to use multi-thread programs with it, such as parallel dump feature of
makedumpfile. Otherwise, the multi-thread program may have a great
performance degradation. To enable multi-cpu support, you should bring up an
SMP dump-capture kernel and specify maxcpus/nr_cpus options while loading it.”…””}”(hjQ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M¿hjM  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÄ  hžhhŸh¶h Nubj†  )”}”(hX  For s390x there are two kdump modes: If a ELF header is specified with
the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
is done on all other architectures. If no elfcorehdr= kernel parameter is
specified, the s390x kdump kernel dynamically creates the header. The
second mode has the advantage that for CPU and memory hotplug, kdump has
not to be reloaded with kexec_load().
”•A‘      h]”h¸)”}”(hXŒ  For s390x there are two kdump modes: If a ELF header is specified with
the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
is done on all other architectures. If no elfcorehdr= kernel parameter is
specified, the s390x kdump kernel dynamically creates the header. The
second mode has the advantage that for CPU and memory hotplug, kdump has
not to be reloaded with kexec_load().”h]”hXŒ  For s390x there are two kdump modes: If a ELF header is specified with
the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
is done on all other architectures. If no elfcorehdr= kernel parameter is
specified, the s390x kdump kernel dynamically creates the header. The
second mode has the advantage that for CPU and memory hotplug, kdump has
not to be reloaded with kexec_load().”…””}”(hji  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MÅhje  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÄ  hžhhŸh¶h Nubj†  )”}”(hXx  For s390x systems with many attached devices the "cio_ignore" kernel
parameter should be used for the kdump kernel in order to prevent allocation
of kernel memory for devices that are not relevant for kdump. The same
applies to systems that use SCSI/FCP devices. In that case the
"allow_lun_scan" zfcp module parameter should be set to zero before
setting FCP devices online.
”h]”h¸)”}”(hXw  For s390x systems with many attached devices the "cio_ignore" kernel
parameter should be used for the kdump kernel in order to prevent allocation
of kernel memory for devices that are not relevant for kdump. The same
applies to systems that use SCSI/FCP devices. In that case the
"allow_lun_scan" zfcp module parameter should be set to zero before
setting FCP devices online.”h]”hX  For s390x systems with many attached devices the â€œcio_ignoreâ€ kernel
parameter should be used for the kdump kernel in order to prevent allocation
of kernel memory for devices that are not relevant for kdump. The same
applies to systems that use SCSI/FCP devices. In that case the
â€œallow_lun_scanâ€ zfcp module parameter should be set to zero before
setting FCP devices online.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MÌhj}  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  hjÄ  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j<  Œ*”uh1jø  hŸh¶h M§hj
  hžhubeh}”(h]”Œload-the-dump-capture-kernel”ah ]”h"]”Œload the dump-capture kernel”ah$]”h&]”uh1h¡hh£hžhhŸh¶h MSubh¢)”}”(hhh]”(h§)”}”(hŒKernel Panic”h]”hŒKernel Panic”…””}”(hj§  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj¤  hžhhŸh¶h MÔubh¸)”}”(hX   After successfully loading the dump-capture kernel as previously
described, the system will reboot into the dump-capture kernel if a
system crash is triggered.  Trigger points are located in panic(),
die(), die_nmi() and in the sysrq handler (ALT-SysRq-c).”h]”hX   After successfully loading the dump-capture kernel as previously
described, the system will reboot into the dump-capture kernel if a
system crash is triggered.  Trigger points are located in panic(),
die(), die_nmi() and in the sysrq handler (ALT-SysRq-c).”…””}”(hjµ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MÖhj¤  hžhubh¸)”}”(hŒ<The following conditions will execute a crash trigger point:”h]”hŒ<The following conditions will execute a crash trigger point:”…””}”(hjÃ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MÛhj¤  hžhubh¸)”}”(hŒIf a hard lockup is detected and "NMI watchdog" is configured, the system
will boot into the dump-capture kernel ( die_nmi() ).”h]”hŒƒIf a hard lockup is detected and â€œNMI watchdogâ€ is configured, the system
will boot into the dump-capture kernel ( die_nmi() ).”…””}”(hjÑ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MÝhj¤  hžhubh¸)”}”(hŒÎIf die() is called, and it happens to be a thread with pid 0 or 1, or die()
is called inside interrupt context or die() is called and panic_on_oops is set,
the system will boot into the dump-capture kernel.”h]”hŒÎIf die() is called, and it happens to be a thread with pid 0 or 1, or die()
is called inside interrupt context or die() is called and panic_on_oops is set,
the system will boot into the dump-capture kernel.”…””}”(hjß  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Màhj¤  hžhubh¸)”}”(hŒ…On powerpc systems when a soft-reset is generated, die() is called by all cpus
and the system will boot into the dump-capture kernel.”h]”hŒ…On powerpc systems when a soft-reset is generated, die() is called by all cpus
and the system will boot into the dump-capture kernel.”…””}”(hjí  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mähj¤  hžhubh¸)”}”(hŒŠFor testing purposes, you can trigger a crash by using "ALT-SysRq-c",
"echo c > /proc/sysrq-trigger" or write a module to force the panic.”h]”hŒ’For testing purposes, you can trigger a crash by using â€œALT-SysRq-câ€,
â€œecho c > /proc/sysrq-triggerâ€ or write a module to force the panic.”…””}”(hjû  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mçhj¤  hžhubeh}”(h]”Œkernel-panic”ah ]”h"]”Œkernel panic”ah$]”h&]”uh1h¡hh£hžhhŸh¶h MÔubh¢)”}”(hhh]”(h§)”}”(hŒWrite Out the Dump File”h]”hŒWrite Out the Dump File”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h Mëubh¸)”}”(hŒ]After the dump-capture kernel is booted, write out the dump file with
the following command::”h]”hŒ\After the dump-capture kernel is booted, write out the dump file with
the following command:”…””}”(hj"  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Míhj  hžhubjŽ  )”}”(hŒcp /proc/vmcore <dump-file>”h]”hŒcp /proc/vmcore <dump-file>”…””}”hj0  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Mðhj  hžhubh¸)”}”(hŒGor use scp to write out the dump file between hosts on a network, e.g::”h]”hŒFor use scp to write out the dump file between hosts on a network, e.g:”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mòhj  hžhubjŽ  )”}”(hŒ6scp /proc/vmcore remote_username@remote_ip:<dump-file>”h]”hŒ6scp /proc/vmcore remote_username@remote_ip:<dump-file>”…””}”hjL  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Môhj  hžhubh¸)”}”(hŒ~You can also use makedumpfile utility to write out the dump file
with specified options to filter out unwanted contents, e.g::”h]”hŒ}You can also use makedumpfile utility to write out the dump file
with specified options to filter out unwanted contents, e.g:”…””}”(hjZ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Möhj  hžhubjŽ  )”}”(hŒ@makedumpfile -l --message-level 1 -d 31 /proc/vmcore <dump-file>”h]”hŒ@makedumpfile -l --message-level 1 -d 31 /proc/vmcore <dump-file>”…””}”hjh  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Mùhj  hžhubeh}”(h]”Œwrite-out-the-dump-file”ah ]”h"]”Œwrite out the dump file”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Mëubh¢)”}”(hhh]”(h§)”}”(hŒAnalysis”h]”hŒAnalysis”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj~  hžhhŸh¶h Müubh¸)”}”(hŒHBefore analyzing the dump image, you should reboot into a stable kernel.”h]”hŒHBefore analyzing the dump image, you should reboot into a stable kernel.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mþhj~  hžhubh¸)”}”(hŒ–You can do limited analysis using GDB on the dump file copied out of
/proc/vmcore. Use the debug vmlinux built with -g and run the following
command::”h]”hŒ•You can do limited analysis using GDB on the dump file copied out of
/proc/vmcore. Use the debug vmlinux built with -g and run the following
command:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M hj~  hžhubjŽ  )”}”(hŒgdb vmlinux <dump-file>”h]”hŒgdb vmlinux <dump-file>”…””}”hj«  sbah}”(h]”h ]”h"]”h$]”h&]”j  jž  uh1j  hŸh¶h Mhj~  hžhubh¸)”}”(hŒXStack trace for the task on processor 0, register display, and memory
display work fine.”h]”hŒXStack trace for the task on processor 0, register display, and memory
display work fine.”…””}”(hj¹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj~  hžhubh¸)”}”(hŒÙNote: GDB cannot analyze core files generated in ELF64 format for x86.
On systems with a maximum of 4GB of memory, you can generate
ELF32-format headers using the --elf32-core-headers kernel option on the
dump kernel.”h]”hŒÙNote: GDB cannot analyze core files generated in ELF64 format for x86.
On systems with a maximum of 4GB of memory, you can generate
ELF32-format headers using the --elf32-core-headers kernel option on the
dump kernel.”…””}”(hjÇ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h M	hj~  hžhubh¸)”}”(hŒrYou can also use the Crash utility to analyze dump files in Kdump
format. Crash is available at the following URL:”h]”hŒrYou can also use the Crash utility to analyze dump files in Kdump
format. Crash is available at the following URL:”…””}”(hjÕ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj~  hžhubj³  )”}”(hŒ'https://github.com/crash-utility/crash
”h]”h¸)”}”(hŒ&https://github.com/crash-utility/crash”h]”jÇ  )”}”(hjé  h]”hŒ&https://github.com/crash-utility/crash”…””}”(hjë  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”jé  uh1jÆ  hjç  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhjã  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j²  hŸh¶h Mhj~  hžhubj×  )”}”(hhh]”jÜ  )”}”(hŒACrash document can be found at:
https://crash-utility.github.io/
”h]”(jâ  )”}”(hŒCrash document can be found at:”h]”hŒCrash document can be found at:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1já  hŸh¶h Mhj  ubjò  )”}”(hhh]”h¸)”}”(hŒ https://crash-utility.github.io/”h]”jÇ  )”}”(hj  h]”hŒ https://crash-utility.github.io/”…””}”(hj!  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”j  uh1jÆ  hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Mhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jñ  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jÛ  hŸh¶h Mhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj~  hžhhŸh¶h Nubeh}”(h]”Œanalysis”ah ]”h"]”Œanalysis”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Müubh¢)”}”(hhh]”(h§)”}”(hŒTrigger Kdump on WARN()”h]”hŒTrigger Kdump on WARN()”…””}”(hjR  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjO  hžhhŸh¶h Mubh¸)”}”(hX	  The kernel parameter, panic_on_warn, calls panic() in all WARN() paths.  This
will cause a kdump to occur at the panic() call.  In cases where a user wants
to specify this during runtime, /proc/sys/kernel/panic_on_warn can be set to 1
to achieve the same behaviour.”h]”hX	  The kernel parameter, panic_on_warn, calls panic() in all WARN() paths.  This
will cause a kdump to occur at the panic() call.  In cases where a user wants
to specify this during runtime, /proc/sys/kernel/panic_on_warn can be set to 1
to achieve the same behaviour.”…””}”(hj`  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h MhjO  hžhubeh}”(h]”Œtrigger-kdump-on-warn”ah ]”h"]”Œtrigger kdump on warn()”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Mubh¢)”}”(hhh]”(h§)”}”(hŒTrigger Kdump on add_taint()”h]”hŒTrigger Kdump on add_taint()”…””}”(hjy  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjv  hžhhŸh¶h Mubh¸)”}”(hX  The kernel parameter panic_on_taint facilitates a conditional call to panic()
from within add_taint() whenever the value set in this bitmask matches with the
bit flag being set by add_taint().
This will cause a kdump to occur at the add_taint()->panic() call.”h]”hX  The kernel parameter panic_on_taint facilitates a conditional call to panic()
from within add_taint() whenever the value set in this bitmask matches with the
bit flag being set by add_taint().
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GDB macros”h]”hŒ
GDB macros”…””}”(hjå  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjâ  hžhhŸh¶h M,ubjŽ  )”}”(hXY"  #
# This file contains a few gdb macros (user defined commands) to extract
# useful information from kernel crashdump (kdump) like stack traces of
# all the processes or a particular process and trapinfo.
#
# These macros can be used by copying this file in .gdbinit (put in home
# directory or current directory) or by invoking gdb command with
# --command=<command-file-name> option
#
# Credits:
# Alexander Nyberg <alexn@telia.com>
# V Srivatsa <vatsa@in.ibm.com>
# Maneesh Soni <maneesh@in.ibm.com>
#

define bttnobp
	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
	set $init_t=&init_task
	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
	set var $stacksize = sizeof(union thread_union)
	while ($next_t != $init_t)
		set $next_t=(struct task_struct *)$next_t
		printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
		printf "===================\n"
		set var $stackp = $next_t.thread.sp
		set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize

		while ($stackp < $stack_top)
			if (*($stackp) > _stext && *($stackp) < _sinittext)
				info symbol *($stackp)
			end
			set $stackp += 4
		end
		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
		while ($next_th != $next_t)
			set $next_th=(struct task_struct *)$next_th
			printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
			printf "===================\n"
			set var $stackp = $next_t.thread.sp
			set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize

			while ($stackp < $stack_top)
				if (*($stackp) > _stext && *($stackp) < _sinittext)
					info symbol *($stackp)
				end
				set $stackp += 4
			end
			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
		end
		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
	end
end
document bttnobp
	dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
end

define btthreadstack
	set var $pid_task = $arg0

	printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
	printf "task struct: "
	print $pid_task
	printf "===================\n"
	set var $stackp = $pid_task.thread.sp
	set var $stacksize = sizeof(union thread_union)
	set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
	set var $stack_bot = ($stackp & ~($stacksize - 1))

	set $stackp = *((unsigned long *) $stackp)
	while (($stackp < $stack_top) && ($stackp > $stack_bot))
		set var $addr = *(((unsigned long *) $stackp) + 1)
		info symbol $addr
		set $stackp = *((unsigned long *) $stackp)
	end
end
document btthreadstack
	 dump a thread stack using the given task structure pointer
end


define btt
	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
	set $init_t=&init_task
	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
	while ($next_t != $init_t)
		set $next_t=(struct task_struct *)$next_t
		btthreadstack $next_t

		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
		while ($next_th != $next_t)
			set $next_th=(struct task_struct *)$next_th
			btthreadstack $next_th
			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
		end
		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
	end
end
document btt
	dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER
end

define btpid
	set var $pid = $arg0
	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
	set $init_t=&init_task
	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
	set var $pid_task = 0

	while ($next_t != $init_t)
		set $next_t=(struct task_struct *)$next_t

		if ($next_t.pid == $pid)
			set $pid_task = $next_t
		end

		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
		while ($next_th != $next_t)
			set $next_th=(struct task_struct *)$next_th
			if ($next_th.pid == $pid)
				set $pid_task = $next_th
			end
			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
		end
		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
	end

	btthreadstack $pid_task
end
document btpid
	backtrace of pid
end


define trapinfo
	set var $pid = $arg0
	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
	set $init_t=&init_task
	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
	set var $pid_task = 0

	while ($next_t != $init_t)
		set $next_t=(struct task_struct *)$next_t

		if ($next_t.pid == $pid)
			set $pid_task = $next_t
		end

		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
		while ($next_th != $next_t)
			set $next_th=(struct task_struct *)$next_th
			if ($next_th.pid == $pid)
				set $pid_task = $next_th
			end
			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
		end
		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
	end

	printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \
				$pid_task.thread.cr2, $pid_task.thread.error_code

end
document trapinfo
	Run info threads and lookup pid of thread #1
	'trapinfo <pid>' will tell you by which trap & possibly
	address the kernel panicked.
end

define dump_record
	set var $desc = $arg0
	set var $info = $arg1
	if ($argc > 2)
		set var $prev_flags = $arg2
	else
		set var $prev_flags = 0
	end

	set var $prefix = 1
	set var $newline = 1

	set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits)
	set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits)

	# handle data-less record
	if ($begin & 1)
		set var $text_len = 0
		set var $log = ""
	else
		# handle wrapping data block
		if ($begin > $next)
			set var $begin = 0
		end

		# skip over descriptor id
		set var $begin = $begin + sizeof(long)

		# handle truncated message
		if ($next - $begin < $info->text_len)
			set var $text_len = $next - $begin
		else
			set var $text_len = $info->text_len
		end

		set var $log = &prb->text_data_ring.data[$begin]
	end

	# prev & LOG_CONT && !(info->flags & LOG_PREIX)
	if (($prev_flags & 8) && !($info->flags & 4))
		set var $prefix = 0
	end

	# info->flags & LOG_CONT
	if ($info->flags & 8)
		# (prev & LOG_CONT && !(prev & LOG_NEWLINE))
		if (($prev_flags & 8) && !($prev_flags & 2))
			set var $prefix = 0
		end
		# (!(info->flags & LOG_NEWLINE))
		if (!($info->flags & 2))
			set var $newline = 0
		end
	end

	if ($prefix)
		printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000
	end
	if ($text_len)
		eval "printf \"%%%d.%ds\", $log", $text_len, $text_len
	end
	if ($newline)
		printf "\n"
	end

	# handle dictionary data

	set var $dict = &$info->dev_info.subsystem[0]
	set var $dict_len = sizeof($info->dev_info.subsystem)
	if ($dict[0] != '\0')
		printf " SUBSYSTEM="
		set var $idx = 0
		while ($idx < $dict_len)
			set var $c = $dict[$idx]
			if ($c == '\0')
				loop_break
			else
				if ($c < ' ' || $c >= 127 || $c == '\\')
					printf "\\x%02x", $c
				else
					printf "%c", $c
				end
			end
			set var $idx = $idx + 1
		end
		printf "\n"
	end

	set var $dict = &$info->dev_info.device[0]
	set var $dict_len = sizeof($info->dev_info.device)
	if ($dict[0] != '\0')
		printf " DEVICE="
		set var $idx = 0
		while ($idx < $dict_len)
			set var $c = $dict[$idx]
			if ($c == '\0')
				loop_break
			else
				if ($c < ' ' || $c >= 127 || $c == '\\')
					printf "\\x%02x", $c
				else
					printf "%c", $c
				end
			end
			set var $idx = $idx + 1
		end
		printf "\n"
	end
end
document dump_record
	Dump a single record. The first parameter is the descriptor,
	the second parameter is the info, the third parameter is
	optional and specifies the previous record's flags, used for
	properly formatting continued lines.
end

define dmesg
	# definitions from kernel/printk/printk_ringbuffer.h
	set var $desc_committed = 1
	set var $desc_finalized = 2
	set var $desc_sv_bits = sizeof(long) * 8
	set var $desc_flags_shift = $desc_sv_bits - 2
	set var $desc_flags_mask = 3 << $desc_flags_shift
	set var $id_mask = ~$desc_flags_mask

	set var $desc_count = 1U << prb->desc_ring.count_bits
	set var $prev_flags = 0

	set var $id = prb->desc_ring.tail_id.counter
	set var $end_id = prb->desc_ring.head_id.counter

	while (1)
		set var $desc = &prb->desc_ring.descs[$id % $desc_count]
		set var $info = &prb->desc_ring.infos[$id % $desc_count]

		# skip non-committed record
		set var $state = 3 & ($desc->state_var.counter >> $desc_flags_shift)
		if ($state == $desc_committed || $state == $desc_finalized)
			dump_record $desc $info $prev_flags
			set var $prev_flags = $info->flags
		end

		if ($id == $end_id)
			loop_break
		end
		set var $id = ($id + 1) & $id_mask
	end
end
document dmesg
	print the kernel ring buffer
end
”h]”hX/  #
# This file contains a few gdb macros (user defined commands) to extract
# useful information from kernel crashdump (kdump) like stack traces of
# all the processes or a particular process and trapinfo.
#
# These macros can be used by copying this file in .gdbinit (put in home
# directory or current directory) or by invoking gdb command with
# --command=<command-file-name> option
#
# Credits:
# Alexander Nyberg <alexn@telia.com>
# V Srivatsa <vatsa@in.ibm.com>
# Maneesh Soni <maneesh@in.ibm.com>
#

define bttnobp
        set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
        set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
        set $init_t=&init_task
        set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
        set var $stacksize = sizeof(union thread_union)
        while ($next_t != $init_t)
                set $next_t=(struct task_struct *)$next_t
                printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
                printf "===================\n"
                set var $stackp = $next_t.thread.sp
                set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize

                while ($stackp < $stack_top)
                        if (*($stackp) > _stext && *($stackp) < _sinittext)
                                info symbol *($stackp)
                        end
                        set $stackp += 4
                end
                set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
                while ($next_th != $next_t)
                        set $next_th=(struct task_struct *)$next_th
                        printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
                        printf "===================\n"
                        set var $stackp = $next_t.thread.sp
                        set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize

                        while ($stackp < $stack_top)
                                if (*($stackp) > _stext && *($stackp) < _sinittext)
                                        info symbol *($stackp)
                                end
                                set $stackp += 4
                        end
                        set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
                end
                set $next_t=(char *)($next_t->tasks.next) - $tasks_off
        end
end
document bttnobp
        dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
end

define btthreadstack
        set var $pid_task = $arg0

        printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
        printf "task struct: "
        print $pid_task
        printf "===================\n"
        set var $stackp = $pid_task.thread.sp
        set var $stacksize = sizeof(union thread_union)
        set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
        set var $stack_bot = ($stackp & ~($stacksize - 1))

        set $stackp = *((unsigned long *) $stackp)
        while (($stackp < $stack_top) && ($stackp > $stack_bot))
                set var $addr = *(((unsigned long *) $stackp) + 1)
                info symbol $addr
                set $stackp = *((unsigned long *) $stackp)
        end
end
document btthreadstack
         dump a thread stack using the given task structure pointer
end


define btt
        set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
        set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
        set $init_t=&init_task
        set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
        while ($next_t != $init_t)
                set $next_t=(struct task_struct *)$next_t
                btthreadstack $next_t

                set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
                while ($next_th != $next_t)
                        set $next_th=(struct task_struct *)$next_th
                        btthreadstack $next_th
                        set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
                end
                set $next_t=(char *)($next_t->tasks.next) - $tasks_off
        end
end
document btt
        dump all thread stack traces on a kernel compiled with CONFIG_FRAME_POINTER
end

define btpid
        set var $pid = $arg0
        set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
        set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
        set $init_t=&init_task
        set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
        set var $pid_task = 0

        while ($next_t != $init_t)
                set $next_t=(struct task_struct *)$next_t

                if ($next_t.pid == $pid)
                        set $pid_task = $next_t
                end

                set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
                while ($next_th != $next_t)
                        set $next_th=(struct task_struct *)$next_th
                        if ($next_th.pid == $pid)
                                set $pid_task = $next_th
                        end
                        set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
                end
                set $next_t=(char *)($next_t->tasks.next) - $tasks_off
        end

        btthreadstack $pid_task
end
document btpid
        backtrace of pid
end


define trapinfo
        set var $pid = $arg0
        set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
        set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
        set $init_t=&init_task
        set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
        set var $pid_task = 0

        while ($next_t != $init_t)
                set $next_t=(struct task_struct *)$next_t

                if ($next_t.pid == $pid)
                        set $pid_task = $next_t
                end

                set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
                while ($next_th != $next_t)
                        set $next_th=(struct task_struct *)$next_th
                        if ($next_th.pid == $pid)
                                set $pid_task = $next_th
                        end
                        set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
                end
                set $next_t=(char *)($next_t->tasks.next) - $tasks_off
        end

        printf "Trapno %ld, cr2 0x%lx, error_code %ld\n", $pid_task.thread.trap_no, \
                                $pid_task.thread.cr2, $pid_task.thread.error_code

end
document trapinfo
        Run info threads and lookup pid of thread #1
        'trapinfo <pid>' will tell you by which trap & possibly
        address the kernel panicked.
end

define dump_record
        set var $desc = $arg0
        set var $info = $arg1
        if ($argc > 2)
                set var $prev_flags = $arg2
        else
                set var $prev_flags = 0
        end

        set var $prefix = 1
        set var $newline = 1

        set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits)
        set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits)

        # handle data-less record
        if ($begin & 1)
                set var $text_len = 0
                set var $log = ""
        else
                # handle wrapping data block
                if ($begin > $next)
                        set var $begin = 0
                end

                # skip over descriptor id
                set var $begin = $begin + sizeof(long)

                # handle truncated message
                if ($next - $begin < $info->text_len)
                        set var $text_len = $next - $begin
                else
                        set var $text_len = $info->text_len
                end

                set var $log = &prb->text_data_ring.data[$begin]
        end

        # prev & LOG_CONT && !(info->flags & LOG_PREIX)
        if (($prev_flags & 8) && !($info->flags & 4))
                set var $prefix = 0
        end

        # info->flags & LOG_CONT
        if ($info->flags & 8)
                # (prev & LOG_CONT && !(prev & LOG_NEWLINE))
                if (($prev_flags & 8) && !($prev_flags & 2))
                        set var $prefix = 0
                end
                # (!(info->flags & LOG_NEWLINE))
                if (!($info->flags & 2))
                        set var $newline = 0
                end
        end

        if ($prefix)
                printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000
        end
        if ($text_len)
                eval "printf \"%%%d.%ds\", $log", $text_len, $text_len
        end
        if ($newline)
                printf "\n"
        end

        # handle dictionary data

        set var $dict = &$info->dev_info.subsystem[0]
        set var $dict_len = sizeof($info->dev_info.subsystem)
        if ($dict[0] != '\0')
                printf " SUBSYSTEM="
                set var $idx = 0
                while ($idx < $dict_len)
                        set var $c = $dict[$idx]
                        if ($c == '\0')
                                loop_break
                        else
                                if ($c < ' ' || $c >= 127 || $c == '\\')
                                        printf "\\x%02x", $c
                                else
                                        printf "%c", $c
                                end
                        end
                        set var $idx = $idx + 1
                end
                printf "\n"
        end

        set var $dict = &$info->dev_info.device[0]
        set var $dict_len = sizeof($info->dev_info.device)
        if ($dict[0] != '\0')
                printf " DEVICE="
                set var $idx = 0
                while ($idx < $dict_len)
                        set var $c = $dict[$idx]
                        if ($c == '\0')
                                loop_break
                        else
                                if ($c < ' ' || $c >= 127 || $c == '\\')
                                        printf "\\x%02x", $c
                                else
                                        printf "%c", $c
                                end
                        end
                        set var $idx = $idx + 1
                end
                printf "\n"
        end
end
document dump_record
        Dump a single record. The first parameter is the descriptor,
        the second parameter is the info, the third parameter is
        optional and specifies the previous record's flags, used for
        properly formatting continued lines.
end

define dmesg
        # definitions from kernel/printk/printk_ringbuffer.h
        set var $desc_committed = 1
        set var $desc_finalized = 2
        set var $desc_sv_bits = sizeof(long) * 8
        set var $desc_flags_shift = $desc_sv_bits - 2
        set var $desc_flags_mask = 3 << $desc_flags_shift
        set var $id_mask = ~$desc_flags_mask

        set var $desc_count = 1U << prb->desc_ring.count_bits
        set var $prev_flags = 0

        set var $id = prb->desc_ring.tail_id.counter
        set var $end_id = prb->desc_ring.head_id.counter

        while (1)
                set var $desc = &prb->desc_ring.descs[$id % $desc_count]
                set var $info = &prb->desc_ring.infos[$id % $desc_count]

                # skip non-committed record
                set var $state = 3 & ($desc->state_var.counter >> $desc_flags_shift)
                if ($state == $desc_committed || $state == $desc_finalized)
                        dump_record $desc $info $prev_flags
                        set var $prev_flags = $info->flags
                end

                if ($id == $end_id)
                        loop_break
                end
                set var $id = ($id + 1) & $id_mask
        end
end
document dmesg
        print the kernel ring buffer
end
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