€•Gb      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/arch/x86/kernel-stacks”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$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/zh_TW/arch/x86/kernel-stacks”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/it_IT/arch/x86/kernel-stacks”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/ja_JP/arch/x86/kernel-stacks”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/ko_KR/arch/x86/kernel-stacks”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/sp_SP/arch/x86/kernel-stacks”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒD/var/lib/git/docbuild/linux/Documentation/arch/x86/kernel-stacks.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒKernel Stacks”h]”hŒKernel Stacks”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒKernel stacks on x86-64 bit”h]”hŒKernel stacks on x86-64 bit”…””}”(hhÌhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hhÉhžhhŸh³h KubhŒ	paragraph”“”)”}”(hŒ/Most of the text from Keith Owens, hacked by AK”h]”hŒ/Most of the text from Keith Owens, hacked by AK”…””}”(hhÜhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K
hhÉhžhubhÛ)”}”(hŒ#x86_64 page size (PAGE_SIZE) is 4K.”h]”hŒ#x86_64 page size (PAGE_SIZE) is 4K.”…””}”(hhêhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhÉhžhubhÛ)”}”(hXC  Like all other architectures, x86_64 has a kernel stack for every
active thread.  These thread stacks are THREAD_SIZE (4*PAGE_SIZE) big.
These stacks contain useful data as long as a thread is alive or a
zombie. While the thread is in user space the kernel stack is empty
except for the thread_info structure at the bottom.”h]”hXC  Like all other architectures, x86_64 has a kernel stack for every
active thread.  These thread stacks are THREAD_SIZE (4*PAGE_SIZE) big.
These stacks contain useful data as long as a thread is alive or a
zombie. While the thread is in user space the kernel stack is empty
except for the thread_info structure at the bottom.”…””}”(hhøhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhÉhžhubhÛ)”}”(hX  In addition to the per thread stacks, there are specialized stacks
associated with each CPU.  These stacks are only used while the kernel
is in control on that CPU; when a CPU returns to user space the
specialized stacks contain no useful data.  The main CPU stacks are:”h]”hX  In addition to the per thread stacks, there are specialized stacks
associated with each CPU.  These stacks are only used while the kernel
is in control on that CPU; when a CPU returns to user space the
specialized stacks contain no useful data.  The main CPU stacks are:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhÉhžhubhŒbullet_list”“”)”}”(hhh]”hŒ	list_item”“”)”}”(hXÏ  Interrupt stack.  IRQ_STACK_SIZE

Used for external hardware interrupts.  If this is the first external
hardware interrupt (i.e. not a nested hardware interrupt) then the
kernel switches from the current task to the interrupt stack.  Like
the split thread and interrupt stacks on i386, this gives more room
for kernel interrupt processing without having to increase the size
of every per thread stack.

The interrupt stack is also used when processing a softirq.
”h]”(hÛ)”}”(hŒ Interrupt stack.  IRQ_STACK_SIZE”h]”hŒ Interrupt stack.  IRQ_STACK_SIZE”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Khj  ubhÛ)”}”(hXo  Used for external hardware interrupts.  If this is the first external
hardware interrupt (i.e. not a nested hardware interrupt) then the
kernel switches from the current task to the interrupt stack.  Like
the split thread and interrupt stacks on i386, this gives more room
for kernel interrupt processing without having to increase the size
of every per thread stack.”h]”hXo  Used for external hardware interrupts.  If this is the first external
hardware interrupt (i.e. not a nested hardware interrupt) then the
kernel switches from the current task to the interrupt stack.  Like
the split thread and interrupt stacks on i386, this gives more room
for kernel interrupt processing without having to increase the size
of every per thread stack.”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Khj  ubhÛ)”}”(hŒ;The interrupt stack is also used when processing a softirq.”h]”hŒ;The interrupt stack is also used when processing a softirq.”…””}”(hj;  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K"hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  hžhhŸh³h Nubah}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ*”uh1j  hŸh³h KhhÉhžhubhÛ)”}”(hŒµSwitching to the kernel interrupt stack is done by software based on a
per CPU interrupt nest counter. This is needed because x86-64 "IST"
hardware stacks cannot nest without races.”h]”hŒ¹Switching to the kernel interrupt stack is done by software based on a
per CPU interrupt nest counter. This is needed because x86-64 â€œISTâ€
hardware stacks cannot nest without races.”…””}”(hjW  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K$hhÉhžhubhÛ)”}”(hXÙ  x86_64 also has a feature which is not available on i386, the ability
to automatically switch to a new stack for designated events such as
double fault or NMI, which makes it easier to handle these unusual
events on x86_64.  This feature is called the Interrupt Stack Table
(IST).  There can be up to 7 IST entries per CPU. The IST code is an
index into the Task State Segment (TSS). The IST entries in the TSS
point to dedicated stacks; each stack can be a different size.”h]”hXÙ  x86_64 also has a feature which is not available on i386, the ability
to automatically switch to a new stack for designated events such as
double fault or NMI, which makes it easier to handle these unusual
events on x86_64.  This feature is called the Interrupt Stack Table
(IST).  There can be up to 7 IST entries per CPU. The IST code is an
index into the Task State Segment (TSS). The IST entries in the TSS
point to dedicated stacks; each stack can be a different size.”…””}”(hje  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K(hhÉhžhubhÛ)”}”(hXK  An IST is selected by a non-zero value in the IST field of an
interrupt-gate descriptor.  When an interrupt occurs and the hardware
loads such a descriptor, the hardware automatically sets the new stack
pointer based on the IST value, then invokes the interrupt handler.  If
the interrupt came from user mode, then the interrupt handler prologue
will switch back to the per-thread stack.  If software wants to allow
nested IST interrupts then the handler must adjust the IST values on
entry to and exit from the interrupt handler.  (This is occasionally
done, e.g. for debug exceptions.)”h]”hXK  An IST is selected by a non-zero value in the IST field of an
interrupt-gate descriptor.  When an interrupt occurs and the hardware
loads such a descriptor, the hardware automatically sets the new stack
pointer based on the IST value, then invokes the interrupt handler.  If
the interrupt came from user mode, then the interrupt handler prologue
will switch back to the per-thread stack.  If software wants to allow
nested IST interrupts then the handler must adjust the IST values on
entry to and exit from the interrupt handler.  (This is occasionally
done, e.g. for debug exceptions.)”…””}”(hjs  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K0hhÉhžhubhÛ)”}”(hXç  Events with different IST codes (i.e. with different stacks) can be
nested.  For example, a debug interrupt can safely be interrupted by an
NMI.  arch/x86_64/kernel/entry.S::paranoidentry adjusts the stack
pointers on entry to and exit from all IST events, in theory allowing
IST events with the same code to be nested.  However in most cases, the
stack size allocated to an IST assumes no nesting for the same code.
If that assumption is ever broken then the stacks will become corrupt.”h]”hXç  Events with different IST codes (i.e. with different stacks) can be
nested.  For example, a debug interrupt can safely be interrupted by an
NMI.  arch/x86_64/kernel/entry.S::paranoidentry adjusts the stack
pointers on entry to and exit from all IST events, in theory allowing
IST events with the same code to be nested.  However in most cases, the
stack size allocated to an IST assumes no nesting for the same code.
If that assumption is ever broken then the stacks will become corrupt.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K:hhÉhžhubhÛ)”}”(hŒ&The currently assigned IST stacks are:”h]”hŒ&The currently assigned IST stacks are:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KBhhÉhžhubj  )”}”(hhh]”(j  )”}”(hX[  ESTACK_DF.  EXCEPTION_STKSZ (PAGE_SIZE).

Used for interrupt 8 - Double Fault Exception (#DF).

Invoked when handling one exception causes another exception. Happens
when the kernel is very confused (e.g. kernel stack pointer corrupt).
Using a separate stack allows the kernel to recover from it well enough
in many cases to still output an oops.
”h]”(hÛ)”}”(hŒ(ESTACK_DF.  EXCEPTION_STKSZ (PAGE_SIZE).”h]”hŒ(ESTACK_DF.  EXCEPTION_STKSZ (PAGE_SIZE).”…””}”(hj¤  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KDhj   ubhÛ)”}”(hŒ4Used for interrupt 8 - Double Fault Exception (#DF).”h]”hŒ4Used for interrupt 8 - Double Fault Exception (#DF).”…””}”(hj²  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KFhj   ubhÛ)”}”(hŒúInvoked when handling one exception causes another exception. Happens
when the kernel is very confused (e.g. kernel stack pointer corrupt).
Using a separate stack allows the kernel to recover from it well enough
in many cases to still output an oops.”h]”hŒúInvoked when handling one exception causes another exception. Happens
when the kernel is very confused (e.g. kernel stack pointer corrupt).
Using a separate stack allows the kernel to recover from it well enough
in many cases to still output an oops.”…””}”(hjÀ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KHhj   ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  hžhhŸh³h Nubj  )”}”(hX  ESTACK_NMI.  EXCEPTION_STKSZ (PAGE_SIZE).

Used for non-maskable interrupts (NMI).

NMI can be delivered at any time, including when the kernel is in the
middle of switching stacks.  Using IST for NMI events avoids making
assumptions about the previous state of the kernel stack.
”h]”(hÛ)”}”(hŒ)ESTACK_NMI.  EXCEPTION_STKSZ (PAGE_SIZE).”h]”hŒ)ESTACK_NMI.  EXCEPTION_STKSZ (PAGE_SIZE).”…””}”(hjØ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KMhjÔ  ubhÛ)”}”(hŒ'Used for non-maskable interrupts (NMI).”h]”hŒ'Used for non-maskable interrupts (NMI).”…””}”(hjæ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KOhjÔ  ubhÛ)”}”(hŒÃNMI can be delivered at any time, including when the kernel is in the
middle of switching stacks.  Using IST for NMI events avoids making
assumptions about the previous state of the kernel stack.”h]”hŒÃNMI can be delivered at any time, including when the kernel is in the
middle of switching stacks.  Using IST for NMI events avoids making
assumptions about the previous state of the kernel stack.”…””}”(hjô  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KQhjÔ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  hžhhŸh³h Nubj  )”}”(hXb  ESTACK_DB.  EXCEPTION_STKSZ (PAGE_SIZE).

Used for hardware debug interrupts (interrupt 1) and for software
debug interrupts (INT3).

When debugging a kernel, debug interrupts (both hardware and
software) can occur at any time.  Using IST for these interrupts
avoids making assumptions about the previous state of the kernel
stack.

To handle nested #DB correctly there exist two instances of DB stacks. On
#DB entry the IST stackpointer for #DB is switched to the second instance
so a nested #DB starts from a clean stack. The nested #DB switches
the IST stackpointer to a guard hole to catch triple nesting.
”h]”(hÛ)”}”(hŒ(ESTACK_DB.  EXCEPTION_STKSZ (PAGE_SIZE).”h]”hŒ(ESTACK_DB.  EXCEPTION_STKSZ (PAGE_SIZE).”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KUhj  ubhÛ)”}”(hŒZUsed for hardware debug interrupts (interrupt 1) and for software
debug interrupts (INT3).”h]”hŒZUsed for hardware debug interrupts (interrupt 1) and for software
debug interrupts (INT3).”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KWhj  ubhÛ)”}”(hŒÅWhen debugging a kernel, debug interrupts (both hardware and
software) can occur at any time.  Using IST for these interrupts
avoids making assumptions about the previous state of the kernel
stack.”h]”hŒÅWhen debugging a kernel, debug interrupts (both hardware and
software) can occur at any time.  Using IST for these interrupts
avoids making assumptions about the previous state of the kernel
stack.”…””}”(hj(  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KZhj  ubhÛ)”}”(hX  To handle nested #DB correctly there exist two instances of DB stacks. On
#DB entry the IST stackpointer for #DB is switched to the second instance
so a nested #DB starts from a clean stack. The nested #DB switches
the IST stackpointer to a guard hole to catch triple nesting.”h]”hX  To handle nested #DB correctly there exist two instances of DB stacks. On
#DB entry the IST stackpointer for #DB is switched to the second instance
so a nested #DB starts from a clean stack. The nested #DB switches
the IST stackpointer to a guard hole to catch triple nesting.”…””}”(hj6  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K_hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  hžhhŸh³h Nubj  )”}”(hX'  ESTACK_MCE.  EXCEPTION_STKSZ (PAGE_SIZE).

Used for interrupt 18 - Machine Check Exception (#MC).

MCE can be delivered at any time, including when the kernel is in the
middle of switching stacks.  Using IST for MCE events avoids making
assumptions about the previous state of the kernel stack.
”h]”(hÛ)”}”(hŒ)ESTACK_MCE.  EXCEPTION_STKSZ (PAGE_SIZE).”h]”hŒ)ESTACK_MCE.  EXCEPTION_STKSZ (PAGE_SIZE).”…””}”(hjN  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KdhjJ  ubhÛ)”}”(hŒ6Used for interrupt 18 - Machine Check Exception (#MC).”h]”hŒ6Used for interrupt 18 - Machine Check Exception (#MC).”…””}”(hj\  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KfhjJ  ubhÛ)”}”(hŒÃMCE can be delivered at any time, including when the kernel is in the
middle of switching stacks.  Using IST for MCE events avoids making
assumptions about the previous state of the kernel stack.”h]”hŒÃMCE can be delivered at any time, including when the kernel is in the
middle of switching stacks.  Using IST for MCE events avoids making
assumptions about the previous state of the kernel stack.”…””}”(hjj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhjJ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  hžhhŸh³h Nubeh}”(h]”h ]”h"]”h$]”h&]”jU  jV  uh1j  hŸh³h KDhhÉhžhubhÛ)”}”(hŒFFor more details see the Intel IA32 or AMD AMD64 architecture manuals.”h]”hŒFFor more details see the Intel IA32 or AMD AMD64 architecture manuals.”…””}”(hj„  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KlhhÉhžhubeh}”(h]”Œkernel-stacks-on-x86-64-bit”ah ]”h"]”Œkernel stacks on x86-64 bit”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒPrinting backtraces on x86”h]”hŒPrinting backtraces on x86”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjš  hžhhŸh³h KpubhÛ)”}”(hŒóThe question about the '?' preceding function names in an x86 stacktrace
keeps popping up, here's an indepth explanation. It helps if the reader
stares at print_context_stack() and the whole machinery in and around
arch/x86/kernel/dumpstack.c.”h]”hŒùThe question about the â€˜?â€™ preceding function names in an x86 stacktrace
keeps popping up, hereâ€™s an indepth explanation. It helps if the reader
stares at print_context_stack() and the whole machinery in and around
arch/x86/kernel/dumpstack.c.”…””}”(hj«  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Krhjš  hžhubhÛ)”}”(hŒIAdapted from Ingo's mail, Message-ID: <20150521101614.GA10889@gmail.com>:”h]”(hŒ)Adapted from Ingoâ€™s mail, Message-ID: <”…””}”(hj¹  hžhhŸNh NubhŒ	reference”“”)”}”(hŒ 20150521101614.GA10889@gmail.com”h]”hŒ 20150521101614.GA10889@gmail.com”…””}”(hjÃ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œ'mailto:20150521101614.GA10889@gmail.com”uh1jÁ  hj¹  ubhŒ>:”…””}”(hj¹  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kwhjš  hžhubhÛ)”}”(hŒ½We always scan the full kernel stack for return addresses stored on
the kernel stack(s) [1]_, from stack top to stack bottom, and print out
anything that 'looks like' a kernel text address.”h]”(hŒXWe always scan the full kernel stack for return addresses stored on
the kernel stack(s) ”…””}”(hjÝ  hžhhŸNh NubhŒfootnote_reference”“”)”}”(hŒ[1]_”h]”hŒ1”…””}”(hjç  hžhhŸNh Nubah}”(h]”Œid1”ah ]”h"]”h$]”h&]”Œrefid”Œid2”Œdocname”Œarch/x86/kernel-stacks”uh1jå  hjÝ  Œresolved”KubhŒe, from stack top to stack bottom, and print out
anything that â€˜looks likeâ€™ a kernel text address.”…””}”(hjÝ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kyhjš  hžhubhÛ)”}”(hŒ{If it fits into the frame pointer chain, we print it without a question
mark, knowing that it's part of the real backtrace.”h]”hŒ}If it fits into the frame pointer chain, we print it without a question
mark, knowing that itâ€™s part of the real backtrace.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K}hjš  hžhubhÛ)”}”(hŒ€If the address does not fit into our expected frame pointer chain we
still print it, but we print a '?'. It can mean two things:”h]”hŒ„If the address does not fit into our expected frame pointer chain we
still print it, but we print a â€˜?â€™. It can mean two things:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K€hjš  hžhubhŒblock_quote”“”)”}”(hX  - either the address is not part of the call chain: it's just stale
  values on the kernel stack, from earlier function calls. This is
  the common case.

- or it is part of the call chain, but the frame pointer was not set
  up properly within the function, so we don't recognize it.
”h]”j  )”}”(hhh]”(j  )”}”(hŒ”either the address is not part of the call chain: it's just stale
values on the kernel stack, from earlier function calls. This is
the common case.
”h]”hÛ)”}”(hŒ“either the address is not part of the call chain: it's just stale
values on the kernel stack, from earlier function calls. This is
the common case.”h]”hŒ•either the address is not part of the call chain: itâ€™s just stale
values on the kernel stack, from earlier function calls. This is
the common case.”…””}”(hj.  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kƒhj*  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj'  ubj  )”}”(hŒ~or it is part of the call chain, but the frame pointer was not set
up properly within the function, so we don't recognize it.
”h]”hÛ)”}”(hŒ}or it is part of the call chain, but the frame pointer was not set
up properly within the function, so we don't recognize it.”h]”hŒor it is part of the call chain, but the frame pointer was not set
up properly within the function, so we donâ€™t recognize it.”…””}”(hjF  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K‡hjB  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj'  ubeh}”(h]”h ]”h"]”h$]”h&]”jU  Œ-”uh1j  hŸh³h Kƒhj#  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j!  hŸh³h Kƒhjš  hžhubhÛ)”}”(hX7  This way we will always print out the real call chain (plus a few more
entries), regardless of whether the frame pointer was set up correctly
or not - but in most cases we'll get the call chain right as well. The
entries printed are strictly in stack order, so you can deduce more
information from that as well.”h]”hX9  This way we will always print out the real call chain (plus a few more
entries), regardless of whether the frame pointer was set up correctly
or not - but in most cases weâ€™ll get the call chain right as well. The
entries printed are strictly in stack order, so you can deduce more
information from that as well.”…””}”(hjg  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KŠhjš  hžhubhÛ)”}”(hX,  The most important property of this method is that we _never_ lose
information: we always strive to print _all_ addresses on the stack(s)
that look like kernel text addresses, so if debug information is wrong,
we still print out the real call chain as well - just with more question
marks than ideal.”h]”hX,  The most important property of this method is that we _never_ lose
information: we always strive to print _all_ addresses on the stack(s)
that look like kernel text addresses, so if debug information is wrong,
we still print out the real call chain as well - just with more question
marks than ideal.”…””}”(hju  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Khjš  hžhubhŒfootnote”“”)”}”(hŒ»For things like IRQ and IST stacks, we also scan those stacks, in
the right order, and try to cross from one stack into another
reconstructing the call chain. This works most of the time.”h]”(hŒlabel”“”)”}”(hŒ1”h]”hŒ1”…””}”(hj‹  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j‰  hj…  ubhÛ)”}”(hŒ»For things like IRQ and IST stacks, we also scan those stacks, in
the right order, and try to cross from one stack into another
reconstructing the call chain. This works most of the time.”h]”hŒ»For things like IRQ and IST stacks, we also scan those stacks, in
the right order, and try to cross from one stack into another
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decoration”Nhžhub.