[PATCH] Don't profile branches in arm's boot decompressor

[PATCH] Don't profile branches in arm's boot decompressor

[Uwe Kleine-König]

This fixes many compile errors for arch/arm/boot/compressed/misc.c of
the type:

	arch/arm/boot/compressed/misc.c:127: error: section attribute cannot be specified for local variables

Fix was suggested by Steven Rostedt in #linux-rt.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Steven Rostedt <rostedt@home.goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>

---
 arch/arm/boot/compressed/Makefile |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index fbe5eef..0bcc98c 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -89,7 +89,7 @@ LDFLAGS_vmlinux += -p --no-undefined -X \
 
 # Don't allow any static data in misc.o, which
 # would otherwise mess up our GOT table
-CFLAGS_misc.o := -Dstatic=
+CFLAGS_misc.o := -Dstatic= -DDISABLE_BRANCH_PROFILING
 
 $(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/$(HEAD) $(obj)/piggy.o \
 	 	$(addprefix $(obj)/, $(OBJS)) FORCE
-- 
tg: (db50eec..) t/ftrace/fix-PROFILE_ALL_BRANCHES (depends on: tip/master)

Re: [PATCH] Don't profile branches in arm's boot decompressor

[Daniel Walker]

On Fri, 2009-02-27 at 22:09 +0100, Uwe Kleine-König wrote:
> This fixes many compile errors for arch/arm/boot/compressed/misc.c of
> the type:
> 
> 	arch/arm/boot/compressed/misc.c:127: error: section attribute cannot be specified for local variables

Why do you think this error showed up just in that one file? It looks
like the branch tracer puts section tags on non-globals all over the
kernel..

Daniel

Re: [PATCH] Don't profile branches in arm's boot decompressor

[Uwe Kleine-König]

Hi Daniel,

On Fri, Feb 27, 2009 at 01:19:47PM -0800, Daniel Walker wrote:
> On Fri, 2009-02-27 at 22:09 +0100, Uwe Kleine-König wrote:
> > This fixes many compile errors for arch/arm/boot/compressed/misc.c of
> > the type:
> > 
> > 	arch/arm/boot/compressed/misc.c:127: error: section attribute cannot be specified for local variables
> 
> Why do you think this error showed up just in that one file? It looks
> like the branch tracer puts section tags on non-globals all over the
> kernel..
With this patch I was able to compile an ARM kernel with profiling
enabled.  Is that enough justification?

Best regards
Uwe

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |

Re: [PATCH] Don't profile branches in arm's boot decompressor

[Daniel Walker]

On Fri, 2009-02-27 at 22:28 +0100, Uwe Kleine-König wrote:
> Hi Daniel,
> 
> On Fri, Feb 27, 2009 at 01:19:47PM -0800, Daniel Walker wrote:
> > On Fri, 2009-02-27 at 22:09 +0100, Uwe Kleine-König wrote:
> > > This fixes many compile errors for arch/arm/boot/compressed/misc.c of
> > > the type:
> > > 
> > > 	arch/arm/boot/compressed/misc.c:127: error: section attribute cannot be specified for local variables
> > 
> > Why do you think this error showed up just in that one file? It looks
> > like the branch tracer puts section tags on non-globals all over the
> > kernel..
> With this patch I was able to compile an ARM kernel with profiling
> enabled.  Is that enough justification?

I'm not asking for any sort of justification .. I'm just wondering if
you know why that error is showing up there and not in other places..

Daniel

Re: [PATCH] Don't profile branches in arm's boot decompressor

[Steven Rostedt]

On Fri, 27 Feb 2009, Daniel Walker wrote:

> On Fri, 2009-02-27 at 22:09 +0100, Uwe Kleine-K?nig wrote:
> > This fixes many compile errors for arch/arm/boot/compressed/misc.c of
> > the type:
> > 
> > 	arch/arm/boot/compressed/misc.c:127: error: section attribute cannot be specified for local variables
> 
> Why do you think this error showed up just in that one file? It looks
> like the branch tracer puts section tags on non-globals all over the
> kernel..

The problem was with the -Dstatic= in the CFLAGS of the boot parameters. 
Since the branch profiler requires a static variable in the section, this 
would simply fail. That was the issue, and the solution was to disable the 
branch profiler for the boot code. No need for it there anyway.

-- Steve

Re: [PATCH] Don't profile branches in arm's boot decompressor

[Steven Rostedt]

Thanks Uwe!



On Fri, Feb 27, 2009 at 10:09:43PM +0100, Uwe Kleine-K??nig wrote:
> This fixes many compile errors for arch/arm/boot/compressed/misc.c of
> the type:
> 
> 	arch/arm/boot/compressed/misc.c:127: error: section attribute cannot be specified for local variables
> 
> Fix was suggested by Steven Rostedt in #linux-rt.
> 
> Signed-off-by: Uwe Kleine-K??nig <u.kleine-koenig@pengutronix.de>
> Cc: Steven Rostedt <rostedt@home.goodmis.org>
> Cc: Ingo Molnar <mingo@elte.hu>
> 
> ---
>  arch/arm/boot/compressed/Makefile |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index fbe5eef..0bcc98c 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -89,7 +89,7 @@ LDFLAGS_vmlinux += -p --no-undefined -X \
>  
>  # Don't allow any static data in misc.o, which
>  # would otherwise mess up our GOT table
> -CFLAGS_misc.o := -Dstatic=
> +CFLAGS_misc.o := -Dstatic= -DDISABLE_BRANCH_PROFILING

Could you also add a comment saying something to the effect:

# The branch profiler requires static variables.
# No need to profile the boot up code, so simply disable it.

Thanks,

-- Steve

>  
>  $(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/$(HEAD) $(obj)/piggy.o \
>  	 	$(addprefix $(obj)/, $(OBJS)) FORCE
> -- 
> tg: (db50eec..) t/ftrace/fix-PROFILE_ALL_BRANCHES (depends on: tip/master)
> --
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[PATCH] Don't profile branches in arm's boot decompressor

[Uwe Kleine-König]

This fixes many compile errors for arch/arm/boot/compressed/misc.c of
the type:

	arch/arm/boot/compressed/misc.c:127: error: section attribute cannot be specified for local variables

The problem is that the branch profiler requires static variables and
arch/arm/boot/compressed/misc.c is compiled with "-Dstatic=".  Anyhow,
there is no big win in profiling boot up code, so simply disable it.

Fix was suggested by Steven Rostedt in #linux-rt.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Steven Rostedt <rostedt@home.goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Daniel Walker <dwalker@fifo99.com>
---
 arch/arm/boot/compressed/Makefile |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index fbe5eef..0bcc98c 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -89,7 +89,7 @@ LDFLAGS_vmlinux += -p --no-undefined -X \
 
 # Don't allow any static data in misc.o, which
 # would otherwise mess up our GOT table
-CFLAGS_misc.o := -Dstatic=
+CFLAGS_misc.o := -Dstatic= -DDISABLE_BRANCH_PROFILING
 
 $(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/$(HEAD) $(obj)/piggy.o \
 	 	$(addprefix $(obj)/, $(OBJS)) FORCE
-- 
tg: (db50eec..) t/ftrace/fix-PROFILE_ALL_BRANCHES (depends on: tip/master)