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authorSteven Rostedt <srostedt@redhat.com>2012-04-30 09:17:03 -0400
committerSteven Rostedt <rostedt@goodmis.org>2012-05-16 20:00:29 -0400
commitb732d439cb43336cd6d7e804ecb2c81193ef63b0 (patch)
tree8c89aec44ef3fbc6ff3e3afbf74ca5ded1354bc1
parente4f5d5440bb860a3e8942ca8f7277a7f31798965 (diff)
downloadlinux-b732d439cb43336cd6d7e804ecb2c81193ef63b0.tar.gz
ftrace: Remove selecting FRAME_POINTER with FUNCTION_TRACER
The function tracer will enable the -pg option with gcc, which requires
that frame pointers. When FRAME_POINTER is defined in the kernel config
it adds the gcc option -fno-omit-frame-pointer which causes some problems
on some architectures. For those architectures, the FRAME_POINTER select
was not set.

When FUNCTION_TRACER was selected on these architectures that can not have
-fno-omit-frame-pointer, the -pg option is still set. But when
FRAME_POINTER is not selected, the kernel config would add the gcc option
-fomit-frame-pointer. Adding this option is incompatible with -pg
even on archs that do not need frame pointers with -pg.

The answer to this was to just not add either -fno-omit-frame-pointer
or -fomit-frame-pointer on these archs that want function tracing
but do not set FRAME_POINTER.

As it turns out, for archs that require frame pointers for function
tracing, the same can be used. If gcc requires frame pointers with
-pg, it will simply add it. The best thing to do is not select FRAME_POINTER
when function tracing is selected, and let gcc add it if needed.

Only add the -fno-omit-frame-pointer when something else selects
FRAME_POINTER, but do not add -fomit-frame-pointer if function tracing
is selected.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--kernel/trace/Kconfig1
1 files changed, 0 insertions, 1 deletions
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index a1d2849f2473..d81a1a532994 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -141,7 +141,6 @@ if FTRACE
 config FUNCTION_TRACER
 	bool "Kernel Function Tracer"
 	depends on HAVE_FUNCTION_TRACER
-	select FRAME_POINTER if !ARM_UNWIND && !PPC && !S390 && !MICROBLAZE
 	select KALLSYMS
 	select GENERIC_TRACER
 	select CONTEXT_SWITCH_TRACER