[PATCH 4.14 014/159] x86/unwind: Make CONFIG_UNWINDER_ORC=y the default in kconfig for 64-bit

Greg Kroah-Hartman
2017-12-22T09:51:44Z

From: Josh Poimboeuf <jpoimboe@redhat.com>

commit fc72ae40e30327aa24eb88a24b9c7058f938bd36 upstream.

The ORC unwinder has been stable in testing so far. Give it much wider
testing by making it the default in kconfig for x86_64. It's not yet
supported for 32-bit, so leave frame pointers as the default there.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/9b1237bbe7244ed9cdf8db2dcb1253e37e1c341e.1507924831.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/Kconfig.debug | 33 +++++++++++++++++----------------
1 file changed, 17 insertions(+), 16 deletions(-)

--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -359,27 +359,13 @@ config PUNIT_ATOM_DEBUG

choice
prompt "Choose kernel unwinder"
- default UNWINDER_FRAME_POINTER
+ default UNWINDER_ORC if X86_64
+ default UNWINDER_FRAME_POINTER if X86_32
---help---
This determines which method will be used for unwinding kernel stack
traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
livepatch, lockdep, and more.

-config UNWINDER_FRAME_POINTER
- bool "Frame pointer unwinder"
- select FRAME_POINTER
- ---help---
- This option enables the frame pointer unwinder for unwinding kernel
- stack traces.
-
- The unwinder itself is fast and it uses less RAM than the ORC
- unwinder, but the kernel text size will grow by ~3% and the kernel's
- overall performance will degrade by roughly 5-10%.
-
- This option is recommended if you want to use the livepatch
- consistency model, as this is currently the only way to get a
- reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE).
-
config UNWINDER_ORC
bool "ORC unwinder"
depends on X86_64
@@ -396,6 +382,21 @@ config UNWINDER_ORC
Enabling this option will increase the kernel's runtime memory usage
by roughly 2-4MB, depending on your kernel config.

+config UNWINDER_FRAME_POINTER
+ bool "Frame pointer unwinder"
+ select FRAME_POINTER
+ ---help---
+ This option enables the frame pointer unwinder for unwinding kernel
+ stack traces.
+
+ The unwinder itself is fast and it uses less RAM than the ORC
+ unwinder, but the kernel text size will grow by ~3% and the kernel's
+ overall performance will degrade by roughly 5-10%.
+
+ This option is recommended if you want to use the livepatch
+ consistency model, as this is currently the only way to get a
+ reliable stack trace (CONFIG_HAVE_RELIABLE_STACKTRACE).
+
config UNWINDER_GUESS
bool "Guess unwinder"
depends on EXPERT