[RFC PATCH] ARM: debug: Add prompt for FRAME_POINTER to Kconfig.debug

[RFC PATCH] ARM: debug: Add prompt for FRAME_POINTER to Kconfig.debug

[Gregory Fong]

Without a prompt string, it is impossible to disable FRAME_POINTER on
ARM. It will simply set the default value anytime you run 'make'.

To reproduce the original issue, run:
  make multi_v7_defconfig
  scripts/config -d ARM_UNWIND
  make oldconfig
  # check .config, note that FRAME_POINTER=y
  scripts/config -d FRAME_POINTER
  make oldconfig
  # check .config, note that FRAME_POINTER is still y

Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com>
---
 arch/arm/Kconfig.debug | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 970de75..b881fd3 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -33,7 +33,7 @@ config STRICT_DEVMEM
 # traces, you can get a slightly smaller kernel by setting this option to
 # n, but then RMK will have to kill you ;).
 config FRAME_POINTER
-	bool
+	bool "Compile the kernel with frame pointers"
 	depends on !THUMB2_KERNEL
 	default y if !ARM_UNWIND || FUNCTION_GRAPH_TRACER
 	help
-- 
1.9.1

[RFC PATCH] ARM: debug: Add prompt for FRAME_POINTER to Kconfig.debug

[Russell King - ARM Linux]

On Wed, Apr 08, 2015 at 05:04:43PM -0700, Gregory Fong wrote:
> Without a prompt string, it is impossible to disable FRAME_POINTER on
> ARM. It will simply set the default value anytime you run 'make'.

Have you read the comment above it?

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according to speedtest.net.

[RFC PATCH] ARM: debug: Add prompt for FRAME_POINTER to Kconfig.debug

[Gregory Fong]

On Thu, Apr 9, 2015 at 12:45 AM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> On Wed, Apr 08, 2015 at 05:04:43PM -0700, Gregory Fong wrote:
>> Without a prompt string, it is impossible to disable FRAME_POINTER on
>> ARM. It will simply set the default value anytime you run 'make'.
>
> Have you read the comment above it?

Yes!  It says that you'll kill those who disable the option, but
that's not itself a reason to be completely unable to turn it off.

Just think of it as a good way to increase your reputation as a bounty hunter ;)

Seriously though, I agree it's a terrible idea to turn this off in
general, but really that's not a reason to make it impossible, as it
does still have value in very specific cases.  You can still disable
CONFIG_BUG, for example.

[RFC PATCH] ARM: debug: Add prompt for FRAME_POINTER to Kconfig.debug

[Gregory Fong]

On Wed, Apr 8, 2015 at 5:04 PM, Gregory Fong <gregory.0xf0@gmail.com> wrote:
> Without a prompt string, it is impossible to disable FRAME_POINTER on
> ARM. It will simply set the default value anytime you run 'make'.

NAK'ing myself.  You should not disable both FRAME_POINTER and
ARM_UNWIND on ARM, as a working unwind_frame() is required in several
places.  Sorry for the noise.