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x86/kconfig: Make it easier to switch to the new ORC unwinder

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A couple of Kconfig changes which make it much easier to switch to the
new CONFIG_ORC_UNWINDER:

1) Remove x86 dependencies on CONFIG_FRAME_POINTER for lockdep,
   latencytop, and fault injection.  x86 has a 'guess' unwinder which
   just scans the stack for kernel text addresses.  It's not 100%
   accurate but in many cases it's good enough.  This allows those users
   who don't want the text overhead of the frame pointer or ORC
   unwinders to still use these features.  More importantly, this also
   makes it much more straightforward to disable frame pointers.

2) Make CONFIG_ORC_UNWINDER depend on !CONFIG_FRAME_POINTER.  While it
   would be possible to have both enabled, it doesn't really make sense
   to do so.  So enforce a sane configuration to prevent the user from
   making a dumb mistake.

With these changes, when you disable CONFIG_FRAME_POINTER, "make
oldconfig" will ask if you want to enable CONFIG_ORC_UNWINDER.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/9985fb91ce5005fe33ea5cc2a20f14bd33c61d03.1500938583.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2017-07-24 18:36:58 -05:00 committed by Ingo Molnar
parent ee9f8fce99
commit a34a766ff9
2 changed files with 6 additions and 7 deletions
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7
arch/x86/Kconfig.debug
View file

@ -357,7 +357,7 @@ config PUNIT_ATOM_DEBUG
config ORC_UNWINDER
bool "ORC unwinder"
depends on X86_64
depends on X86_64 && !FRAME_POINTER
select STACK_VALIDATION
---help---
This option enables the ORC (Oops Rewind Capability) unwinder for
@ -365,9 +365,8 @@ config ORC_UNWINDER
a simplified version of the DWARF Call Frame Information standard.
This unwinder is more accurate across interrupt entry frames than the
frame pointer unwinder. It can also enable a 5-10% performance
improvement across the entire kernel if CONFIG_FRAME_POINTER is
disabled.
frame pointer unwinder. It also enables a 5-10% performance
improvement across the entire kernel compared to frame pointers.
Enabling this option will increase the kernel's runtime memory usage
by roughly 2-4MB, depending on your kernel config.

6
lib/Kconfig.debug
View file

@ -1124,7 +1124,7 @@ config LOCKDEP
bool
depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
select STACKTRACE
select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE
select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE && !X86
select KALLSYMS
select KALLSYMS_ALL
@ -1543,7 +1543,7 @@ config FAULT_INJECTION_STACKTRACE_FILTER
depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT
depends on !X86_64
select STACKTRACE
select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE
select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE && !X86
help
Provide stacktrace filter for fault-injection capabilities
@ -1552,7 +1552,7 @@ config LATENCYTOP
depends on DEBUG_KERNEL
depends on STACKTRACE_SUPPORT
depends on PROC_FS
select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC
select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !X86
select KALLSYMS
select KALLSYMS_ALL
select STACKTRACE