linux-kernel - [PATCH 2/2] x86/unwind: Make CONFIG_UNWINDER_ORC=y the default in kconfig for 64-bit

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Message-Id: <9b1237bbe7244ed9cdf8db2dcb1253e37e1c341e.1507924831.git.jpoimboe@redhat.com>
Date:   Fri, 13 Oct 2017 15:02:01 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        peterz@...radead.org, hpa@...or.com, tglx@...utronix.de
Subject: [PATCH 2/2] x86/unwind: Make CONFIG_UNWINDER_ORC=y the default in kconfig for 64-bit

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@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/Kconfig.debug | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index f274dbb87c26..a4ff214fb760 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -358,27 +358,13 @@ 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
@@ -395,6 +381,21 @@ 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
-- 
2.13.6