€•Âj      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/process/debugging/gdb-kernel-debugging”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$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ:/translations/zh_TW/process/debugging/gdb-kernel-debugging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ:/translations/it_IT/process/debugging/gdb-kernel-debugging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ:/translations/ja_JP/process/debugging/gdb-kernel-debugging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ:/translations/ko_KR/process/debugging/gdb-kernel-debugging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ:/translations/sp_SP/process/debugging/gdb-kernel-debugging”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”Nubh Œhighlightlang”“”)”}”(hhh]”h}”(h]”h ]”h"]”h$]”h&]”Œlang”Œnone”Œforce”‰Œlinenothreshold”Šÿÿÿÿÿÿÿuh1h¡hhhžhhŸŒT/var/lib/git/docbuild/linux/Documentation/process/debugging/gdb-kernel-debugging.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒ$Debugging kernel and modules via gdb”h]”hŒ$Debugging kernel and modules via gdb”…””}”(hh¸hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¶hh³hžhhŸh°h KubhŒ	paragraph”“”)”}”(hXì  The kernel debugger kgdb, hypervisors like QEMU or JTAG-based hardware
interfaces allow to debug the Linux kernel and its modules during runtime
using gdb. Gdb comes with a powerful scripting interface for python. The
kernel provides a collection of helper scripts that can simplify typical
kernel debugging steps. This is a short tutorial about how to enable and use
them. It focuses on QEMU/KVM virtual machines as target, but the examples can
be transferred to the other gdb stubs as well.”h]”hXì  The kernel debugger kgdb, hypervisors like QEMU or JTAG-based hardware
interfaces allow to debug the Linux kernel and its modules during runtime
using gdb. Gdb comes with a powerful scripting interface for python. The
kernel provides a collection of helper scripts that can simplify typical
kernel debugging steps. This is a short tutorial about how to enable and use
them. It focuses on QEMU/KVM virtual machines as target, but the examples can
be transferred to the other gdb stubs as well.”…””}”(hhÈhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h Khh³hžhubh²)”}”(hhh]”(h·)”}”(hŒRequirements”h]”hŒRequirements”…””}”(hhÙhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¶hhÖhžhhŸh°h KubhŒbullet_list”“”)”}”(hhh]”hŒ	list_item”“”)”}”(hŒ]gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true
for distributions)

”h]”hÇ)”}”(hŒ[gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true
for distributions)”h]”hŒ[gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true
for distributions)”…””}”(hhòhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h Khhîubah}”(h]”h ]”h"]”h$]”h&]”uh1hìhhéhžhhŸh°h Nubah}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1hçhŸh°h KhhÖhžhubeh}”(h]”Œrequirements”ah ]”h"]”Œrequirements”ah$]”h&]”uh1h±hh³hžhhŸh°h Kubh²)”}”(hhh]”(h·)”}”(hŒSetup”h]”hŒSetup”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¶hj  hžhhŸh°h Kubhè)”}”(hhh]”(hí)”}”(hŒòCreate a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and
www.qemu.org for more details). For cross-development,
https://landley.net/aboriginal/bin keeps a pool of machine images and
toolchains that can be helpful to start from.
”h]”hÇ)”}”(hŒñCreate a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and
www.qemu.org for more details). For cross-development,
https://landley.net/aboriginal/bin keeps a pool of machine images and
toolchains that can be helpful to start from.”h]”(hŒ~Create a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and
www.qemu.org for more details). For cross-development,
”…””}”(hj.  hžhhŸNh NubhŒ	reference”“”)”}”(hŒ"https://landley.net/aboriginal/bin”h]”hŒ"https://landley.net/aboriginal/bin”…””}”(hj8  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”j:  uh1j6  hj.  ubhŒQ keeps a pool of machine images and
toolchains that can be helpful to start from.”…””}”(hj.  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h Khj*  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hìhj'  hžhhŸh°h Nubhí)”}”(hŒ Build the kernel with CONFIG_GDB_SCRIPTS enabled, but leave
CONFIG_DEBUG_INFO_REDUCED off. If your architecture supports
CONFIG_FRAME_POINTER, keep it enabled.
”h]”hÇ)”}”(hŒŸBuild the kernel with CONFIG_GDB_SCRIPTS enabled, but leave
CONFIG_DEBUG_INFO_REDUCED off. If your architecture supports
CONFIG_FRAME_POINTER, keep it enabled.”h]”hŒŸBuild the kernel with CONFIG_GDB_SCRIPTS enabled, but leave
CONFIG_DEBUG_INFO_REDUCED off. If your architecture supports
CONFIG_FRAME_POINTER, keep it enabled.”…””}”(hj[  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h KhjW  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hìhj'  hžhhŸh°h Nubhí)”}”(hXÃ  Install that kernel on the guest, turn off KASLR if necessary by adding
"nokaslr" to the kernel command line.
Alternatively, QEMU allows to boot the kernel directly using -kernel,
-append, -initrd command line switches. This is generally only useful if
you do not depend on modules. See QEMU documentation for more details on
this mode. In this case, you should build the kernel with
CONFIG_RANDOMIZE_BASE disabled if the architecture supports KASLR.
”h]”hÇ)”}”(hXÂ  Install that kernel on the guest, turn off KASLR if necessary by adding
"nokaslr" to the kernel command line.
Alternatively, QEMU allows to boot the kernel directly using -kernel,
-append, -initrd command line switches. This is generally only useful if
you do not depend on modules. See QEMU documentation for more details on
this mode. In this case, you should build the kernel with
CONFIG_RANDOMIZE_BASE disabled if the architecture supports KASLR.”h]”hXÆ  Install that kernel on the guest, turn off KASLR if necessary by adding
â€œnokaslrâ€ to the kernel command line.
Alternatively, QEMU allows to boot the kernel directly using -kernel,
-append, -initrd command line switches. This is generally only useful if
you do not depend on modules. See QEMU documentation for more details on
this mode. In this case, you should build the kernel with
CONFIG_RANDOMIZE_BASE disabled if the architecture supports KASLR.”…””}”(hjs  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K"hjo  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hìhj'  hžhhŸh°h Nubhí)”}”(hŒQBuild the gdb scripts (required on kernels v5.1 and above)::

  make scripts_gdb
”h]”(hÇ)”}”(hŒ<Build the gdb scripts (required on kernels v5.1 and above)::”h]”hŒ;Build the gdb scripts (required on kernels v5.1 and above):”…””}”(hj‹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K*hj‡  ubhŒliteral_block”“”)”}”(hŒmake scripts_gdb”h]”hŒmake scripts_gdb”…””}”hj›  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1j™  hŸh°h K,hj‡  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhj'  hžhhŸh°h Nubhí)”}”(hŒ¼Enable the gdb stub of QEMU/KVM, either

  - at VM startup time by appending "-s" to the QEMU command line

or

  - during runtime by issuing "gdbserver" from the QEMU monitor
    console
”h]”(hÇ)”}”(hŒ'Enable the gdb stub of QEMU/KVM, either”h]”hŒ'Enable the gdb stub of QEMU/KVM, either”…””}”(hjµ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K.hj±  ubhŒblock_quote”“”)”}”(hŒ@- at VM startup time by appending "-s" to the QEMU command line
”h]”hè)”}”(hhh]”hí)”}”(hŒ>at VM startup time by appending "-s" to the QEMU command line
”h]”hÇ)”}”(hŒ=at VM startup time by appending "-s" to the QEMU command line”h]”hŒAat VM startup time by appending â€œ-sâ€ to the QEMU command line”…””}”(hjÐ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K0hjÌ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÉ  ubah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1hçhŸh°h K0hjÅ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jÃ  hŸh°h K0hj±  ubhÇ)”}”(hŒor”h]”hŒor”…””}”(hjð  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K2hj±  ubjÄ  )”}”(hŒH- during runtime by issuing "gdbserver" from the QEMU monitor
  console
”h]”hè)”}”(hhh]”hí)”}”(hŒDduring runtime by issuing "gdbserver" from the QEMU monitor
console
”h]”hÇ)”}”(hŒCduring runtime by issuing "gdbserver" from the QEMU monitor
console”h]”hŒGduring runtime by issuing â€œgdbserverâ€ from the QEMU monitor
console”…””}”(hj	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K4hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hìhj  ubah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1hçhŸh°h K4hjþ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jÃ  hŸh°h K4hj±  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhj'  hžhhŸh°h Nubhí)”}”(hŒcd /path/to/linux-build
”h]”hÇ)”}”(hŒcd /path/to/linux-build”h]”hŒcd /path/to/linux-build”…””}”(hj3  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K7hj/  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hìhj'  hžhhŸh°h Nubhí)”}”(hX
  Start gdb: gdb vmlinux

Note: Some distros may restrict auto-loading of gdb scripts to known safe
directories. In case gdb reports to refuse loading vmlinux-gdb.py, add::

  add-auto-load-safe-path /path/to/linux-build

to ~/.gdbinit. See gdb help for more details.
”h]”(hÇ)”}”(hŒStart gdb: gdb vmlinux”h]”hŒStart gdb: gdb vmlinux”…””}”(hjK  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K9hjG  ubhÇ)”}”(hŒ’Note: Some distros may restrict auto-loading of gdb scripts to known safe
directories. In case gdb reports to refuse loading vmlinux-gdb.py, add::”h]”hŒ‘Note: Some distros may restrict auto-loading of gdb scripts to known safe
directories. In case gdb reports to refuse loading vmlinux-gdb.py, add:”…””}”(hjY  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K;hjG  ubjš  )”}”(hŒ,add-auto-load-safe-path /path/to/linux-build”h]”hŒ,add-auto-load-safe-path /path/to/linux-build”…””}”hjg  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h K>hjG  ubhÇ)”}”(hŒ-to ~/.gdbinit. See gdb help for more details.”h]”hŒ-to ~/.gdbinit. See gdb help for more details.”…””}”(hju  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K@hjG  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhj'  hžhhŸh°h Nubhí)”}”(hŒ;Attach to the booted guest::

  (gdb) target remote :1234

”h]”(hÇ)”}”(hŒAttach to the booted guest::”h]”hŒAttach to the booted guest:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h KBhj‰  ubjš  )”}”(hŒ(gdb) target remote :1234”h]”hŒ(gdb) target remote :1234”…””}”hj›  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h KDhj‰  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhj'  hžhhŸh°h Nubeh}”(h]”h ]”h"]”h$]”h&]”j  j  uh1hçhŸh°h Khj  hžhubeh}”(h]”Œsetup”ah ]”h"]”Œsetup”ah$]”h&]”uh1h±hh³hžhhŸh°h Kubh²)”}”(hhh]”(h·)”}”(hŒ0Examples of using the Linux-provided gdb helpers”h]”hŒ0Examples of using the Linux-provided gdb helpers”…””}”(hjÀ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¶hj½  hžhhŸh°h KHubhè)”}”(hhh]”(hí)”}”(hX]  Load module (and main kernel) symbols::

  (gdb) lx-symbols
  loading vmlinux
  scanning for modules in /home/user/linux/build
  loading @0xffffffffa0020000: /home/user/linux/build/net/netfilter/xt_tcpudp.ko
  loading @0xffffffffa0016000: /home/user/linux/build/net/netfilter/xt_pkttype.ko
  loading @0xffffffffa0002000: /home/user/linux/build/net/netfilter/xt_limit.ko
  loading @0xffffffffa00ca000: /home/user/linux/build/net/packet/af_packet.ko
  loading @0xffffffffa003c000: /home/user/linux/build/fs/fuse/fuse.ko
  ...
  loading @0xffffffffa0000000: /home/user/linux/build/drivers/ata/ata_generic.ko
”h]”(hÇ)”}”(hŒ'Load module (and main kernel) symbols::”h]”hŒ&Load module (and main kernel) symbols:”…””}”(hjÕ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h KJhjÑ  ubjš  )”}”(hX  (gdb) lx-symbols
loading vmlinux
scanning for modules in /home/user/linux/build
loading @0xffffffffa0020000: /home/user/linux/build/net/netfilter/xt_tcpudp.ko
loading @0xffffffffa0016000: /home/user/linux/build/net/netfilter/xt_pkttype.ko
loading @0xffffffffa0002000: /home/user/linux/build/net/netfilter/xt_limit.ko
loading @0xffffffffa00ca000: /home/user/linux/build/net/packet/af_packet.ko
loading @0xffffffffa003c000: /home/user/linux/build/fs/fuse/fuse.ko
...
loading @0xffffffffa0000000: /home/user/linux/build/drivers/ata/ata_generic.ko”h]”hX  (gdb) lx-symbols
loading vmlinux
scanning for modules in /home/user/linux/build
loading @0xffffffffa0020000: /home/user/linux/build/net/netfilter/xt_tcpudp.ko
loading @0xffffffffa0016000: /home/user/linux/build/net/netfilter/xt_pkttype.ko
loading @0xffffffffa0002000: /home/user/linux/build/net/netfilter/xt_limit.ko
loading @0xffffffffa00ca000: /home/user/linux/build/net/packet/af_packet.ko
loading @0xffffffffa003c000: /home/user/linux/build/fs/fuse/fuse.ko
...
loading @0xffffffffa0000000: /home/user/linux/build/drivers/ata/ata_generic.ko”…””}”hjã  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h KLhjÑ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÎ  hžhhŸh°h Nubhí)”}”(hŒøSet a breakpoint on some not yet loaded module function, e.g.::

  (gdb) b btrfs_init_sysfs
  Function "btrfs_init_sysfs" not defined.
  Make breakpoint pending on future shared library load? (y or [n]) y
  Breakpoint 1 (btrfs_init_sysfs) pending.
”h]”(hÇ)”}”(hŒ?Set a breakpoint on some not yet loaded module function, e.g.::”h]”hŒ>Set a breakpoint on some not yet loaded module function, e.g.:”…””}”(hjû  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h KWhj÷  ubjš  )”}”(hŒ®(gdb) b btrfs_init_sysfs
Function "btrfs_init_sysfs" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (btrfs_init_sysfs) pending.”h]”hŒ®(gdb) b btrfs_init_sysfs
Function "btrfs_init_sysfs" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (btrfs_init_sysfs) pending.”…””}”hj	  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h KYhj÷  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÎ  hžhhŸh°h Nubhí)”}”(hŒ!Continue the target::

  (gdb) c
”h]”(hÇ)”}”(hŒContinue the target::”h]”hŒContinue the target:”…””}”(hj!  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K^hj  ubjš  )”}”(hŒ(gdb) c”h]”hŒ(gdb) c”…””}”hj/  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h K`hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÎ  hžhhŸh°h Nubhí)”}”(hX/  Load the module on the target and watch the symbols being loaded as well as
the breakpoint hit::

  loading @0xffffffffa0034000: /home/user/linux/build/lib/libcrc32c.ko
  loading @0xffffffffa0050000: /home/user/linux/build/lib/lzo/lzo_compress.ko
  loading @0xffffffffa006e000: /home/user/linux/build/lib/zlib_deflate/zlib_deflate.ko
  loading @0xffffffffa01b1000: /home/user/linux/build/fs/btrfs/btrfs.ko

  Breakpoint 1, btrfs_init_sysfs () at /home/user/linux/fs/btrfs/sysfs.c:36
  36              btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj);
”h]”(hÇ)”}”(hŒ`Load the module on the target and watch the symbols being loaded as well as
the breakpoint hit::”h]”hŒ_Load the module on the target and watch the symbols being loaded as well as
the breakpoint hit:”…””}”(hjG  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h KbhjC  ubjš  )”}”(hXÀ  loading @0xffffffffa0034000: /home/user/linux/build/lib/libcrc32c.ko
loading @0xffffffffa0050000: /home/user/linux/build/lib/lzo/lzo_compress.ko
loading @0xffffffffa006e000: /home/user/linux/build/lib/zlib_deflate/zlib_deflate.ko
loading @0xffffffffa01b1000: /home/user/linux/build/fs/btrfs/btrfs.ko

Breakpoint 1, btrfs_init_sysfs () at /home/user/linux/fs/btrfs/sysfs.c:36
36              btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj);”h]”hXÀ  loading @0xffffffffa0034000: /home/user/linux/build/lib/libcrc32c.ko
loading @0xffffffffa0050000: /home/user/linux/build/lib/lzo/lzo_compress.ko
loading @0xffffffffa006e000: /home/user/linux/build/lib/zlib_deflate/zlib_deflate.ko
loading @0xffffffffa01b1000: /home/user/linux/build/fs/btrfs/btrfs.ko

Breakpoint 1, btrfs_init_sysfs () at /home/user/linux/fs/btrfs/sysfs.c:36
36              btrfs_kset = kset_create_and_add("btrfs", NULL, fs_kobj);”…””}”hjU  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h KehjC  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÎ  hžhhŸh°h Nubhí)”}”(hX  Dump the log buffer of the target kernel::

  (gdb) lx-dmesg
  [     0.000000] Initializing cgroup subsys cpuset
  [     0.000000] Initializing cgroup subsys cpu
  [     0.000000] Linux version 3.8.0-rc4-dbg+ (...
  [     0.000000] Command line: root=/dev/sda2 resume=/dev/sda1 vga=0x314
  [     0.000000] e820: BIOS-provided physical RAM map:
  [     0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
  [     0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
  ....
”h]”(hÇ)”}”(hŒ*Dump the log buffer of the target kernel::”h]”hŒ)Dump the log buffer of the target kernel:”…””}”(hjm  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h Kmhji  ubjš  )”}”(hXÂ  (gdb) lx-dmesg
[     0.000000] Initializing cgroup subsys cpuset
[     0.000000] Initializing cgroup subsys cpu
[     0.000000] Linux version 3.8.0-rc4-dbg+ (...
[     0.000000] Command line: root=/dev/sda2 resume=/dev/sda1 vga=0x314
[     0.000000] e820: BIOS-provided physical RAM map:
[     0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
[     0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
....”h]”hXÂ  (gdb) lx-dmesg
[     0.000000] Initializing cgroup subsys cpuset
[     0.000000] Initializing cgroup subsys cpu
[     0.000000] Linux version 3.8.0-rc4-dbg+ (...
[     0.000000] Command line: root=/dev/sda2 resume=/dev/sda1 vga=0x314
[     0.000000] e820: BIOS-provided physical RAM map:
[     0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
[     0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
....”…””}”hj{  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h Kohji  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÎ  hžhhŸh°h Nubhí)”}”(hŒÁExamine fields of the current task struct(supported by x86 and arm64 only)::

  (gdb) p $lx_current().pid
  $1 = 4998
  (gdb) p $lx_current().comm
  $2 = "modprobe\000\000\000\000\000\000\000"
”h]”(hÇ)”}”(hŒLExamine fields of the current task struct(supported by x86 and arm64 only)::”h]”hŒKExamine fields of the current task struct(supported by x86 and arm64 only):”…””}”(hj“  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h Kyhj  ubjš  )”}”(hŒj(gdb) p $lx_current().pid
$1 = 4998
(gdb) p $lx_current().comm
$2 = "modprobe\000\000\000\000\000\000\000"”h]”hŒj(gdb) p $lx_current().pid
$1 = 4998
(gdb) p $lx_current().comm
$2 = "modprobe\000\000\000\000\000\000\000"”…””}”hj¡  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h K{hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÎ  hžhhŸh°h Nubhí)”}”(hŒ¸Make use of the per-cpu function for the current or a specified CPU::

  (gdb) p $lx_per_cpu("runqueues").nr_running
  $3 = 1
  (gdb) p $lx_per_cpu("runqueues", 2).nr_running
  $4 = 0
”h]”(hÇ)”}”(hŒEMake use of the per-cpu function for the current or a specified CPU::”h]”hŒDMake use of the per-cpu function for the current or a specified CPU:”…””}”(hj¹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K€hjµ  ubjš  )”}”(hŒh(gdb) p $lx_per_cpu("runqueues").nr_running
$3 = 1
(gdb) p $lx_per_cpu("runqueues", 2).nr_running
$4 = 0”h]”hŒh(gdb) p $lx_per_cpu("runqueues").nr_running
$3 = 1
(gdb) p $lx_per_cpu("runqueues", 2).nr_running
$4 = 0”…””}”hjÇ  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h K‚hjµ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÎ  hžhhŸh°h Nubhí)”}”(hXÑ  Dig into hrtimers using the container_of helper::

  (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next
  (gdb) p *$container_of($next, "struct hrtimer", "node")
  $5 = {
    node = {
      node = {
        __rb_parent_color = 18446612133355256072,
        rb_right = 0x0 <irq_stack_union>,
        rb_left = 0x0 <irq_stack_union>
      },
      expires = {
        tv64 = 1835268000000
      }
    },
    _softexpires = {
      tv64 = 1835268000000
    },
    function = 0xffffffff81078232 <tick_sched_timer>,
    base = 0xffff88003fd0d6f0,
    state = 1,
    start_pid = 0,
    start_site = 0xffffffff81055c1f <hrtimer_start_range_ns+20>,
    start_comm = "swapper/2\000\000\000\000\000\000"
  }

”h]”(hÇ)”}”(hŒ1Dig into hrtimers using the container_of helper::”h]”hŒ0Dig into hrtimers using the container_of helper:”…””}”(hjß  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K‡hjÛ  ubjš  )”}”(hXn  (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next
(gdb) p *$container_of($next, "struct hrtimer", "node")
$5 = {
  node = {
    node = {
      __rb_parent_color = 18446612133355256072,
      rb_right = 0x0 <irq_stack_union>,
      rb_left = 0x0 <irq_stack_union>
    },
    expires = {
      tv64 = 1835268000000
    }
  },
  _softexpires = {
    tv64 = 1835268000000
  },
  function = 0xffffffff81078232 <tick_sched_timer>,
  base = 0xffff88003fd0d6f0,
  state = 1,
  start_pid = 0,
  start_site = 0xffffffff81055c1f <hrtimer_start_range_ns+20>,
  start_comm = "swapper/2\000\000\000\000\000\000"
}”h]”hXn  (gdb) set $next = $lx_per_cpu("hrtimer_bases").clock_base[0].active.next
(gdb) p *$container_of($next, "struct hrtimer", "node")
$5 = {
  node = {
    node = {
      __rb_parent_color = 18446612133355256072,
      rb_right = 0x0 <irq_stack_union>,
      rb_left = 0x0 <irq_stack_union>
    },
    expires = {
      tv64 = 1835268000000
    }
  },
  _softexpires = {
    tv64 = 1835268000000
  },
  function = 0xffffffff81078232 <tick_sched_timer>,
  base = 0xffff88003fd0d6f0,
  state = 1,
  start_pid = 0,
  start_site = 0xffffffff81055c1f <hrtimer_start_range_ns+20>,
  start_comm = "swapper/2\000\000\000\000\000\000"
}”…””}”hjí  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h K‰hjÛ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hìhjÎ  hžhhŸh°h Nubeh}”(h]”h ]”h"]”h$]”h&]”j  j  uh1hçhŸh°h KJhj½  hžhubeh}”(h]”Œ0examples-of-using-the-linux-provided-gdb-helpers”ah ]”h"]”Œ0examples of using the linux-provided gdb helpers”ah$]”h&]”uh1h±hh³hžhhŸh°h KHubh²)”}”(hhh]”(h·)”}”(hŒList of commands and functions”h]”hŒList of commands and functions”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¶hj  hžhhŸh°h K£ubhÇ)”}”(hŒ{The number of commands and convenience functions may evolve over the time,
this is just a snapshot of the initial version::”h]”hŒzThe number of commands and convenience functions may evolve over the time,
this is just a snapshot of the initial version:”…””}”(hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K¥hj  hžhubjš  )”}”(hXô  (gdb) apropos lx
function lx_current -- Return current task
function lx_module -- Find module by name and return the module variable
function lx_per_cpu -- Return per-cpu variable
function lx_task_by_pid -- Find Linux task by PID and return the task_struct variable
function lx_thread_info -- Calculate Linux thread_info from task variable
lx-dmesg -- Print Linux kernel log buffer
lx-lsmod -- List currently loaded modules
lx-symbols -- (Re-)load symbols of Linux kernel and currently loaded modules”h]”hXô  (gdb) apropos lx
function lx_current -- Return current task
function lx_module -- Find module by name and return the module variable
function lx_per_cpu -- Return per-cpu variable
function lx_task_by_pid -- Find Linux task by PID and return the task_struct variable
function lx_thread_info -- Calculate Linux thread_info from task variable
lx-dmesg -- Print Linux kernel log buffer
lx-lsmod -- List currently loaded modules
lx-symbols -- (Re-)load symbols of Linux kernel and currently loaded modules”…””}”hj.  sbah}”(h]”h ]”h"]”h$]”h&]”j©  jª  uh1j™  hŸh°h K¨hj  hžhubhÇ)”}”(hŒƒDetailed help can be obtained via "help <command-name>" for commands and "help
function <function-name>" for convenience functions.”h]”hŒ‹Detailed help can be obtained via â€œhelp <command-name>â€ for commands and â€œhelp
function <function-name>â€ for convenience functions.”…””}”(hj<  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÆhŸh°h K²hj  hžhubeh}”(h]”Œlist-of-commands-and-functions”ah ]”h"]”Œlist of commands and functions”ah$]”h&]”uh1h±hh³hžhhŸh°h K£ubeh}”(h]”Œ$debugging-kernel-and-modules-via-gdb”ah ]”h"]”Œ$debugging kernel and modules via gdb”ah$]”h&]”uh1h±hhhžhhŸh°h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h°uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¶NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j}  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h°Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(jW  jT  j  j  jº  j·  j  j	  jO  jL  uŒ	nametypes”}”(jW  ‰j  ‰jº  ‰j  ‰jO  ‰uh}”(jT  h³j  hÖj·  j  j	  j½  jL  j  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.