Commit a34a766f authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

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



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: default avatarJosh 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: default avatarIngo Molnar <mingo@kernel.org>
parent ee9f8fce

arch/x86/Kconfig.debug

+3 −4
Original line number Diff line number Diff line
@@ -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.

lib/Kconfig.debug

+3 −3
Original line number Diff line number Diff line
@@ -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

CRA Git | Maintained and supported by SUSTech CRA and CCSE