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: 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>

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index dc10ec6ead6e6af73f2453c0851573f8823c5e02..268a318f9439bffb15a13082c112fe90e29b32a3 100644 (file)
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -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.

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 0f0d019ffb99f1050b6f0f00f2d8929f4774e41f..32a48e739e26425cfec0c9657794755d895f6ec4 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -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