linux-kernel - Re: dynamic ftrace/recordmcount.c problem on ARMv5

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Message-ID: <20160113110856.4e7c5cdb@gandalf.local.home>
Date:	Wed, 13 Jan 2016 11:08:56 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Marc Kleine-Budde <mkl@...gutronix.de>
Cc:	linux-kernel@...r.kernel.org, ptx kernel <kernel@...gutronix.de>
Subject: Re: dynamic ftrace/recordmcount.c problem on ARMv5

On Wed, 13 Jan 2016 09:51:28 +0100
Marc Kleine-Budde <mkl@...gutronix.de> wrote:

> There are 5 calls to __gnu_mcount_nc in the object file:
> > $ objdump -x arch/arm/kernel/stacktrace.o | grep R_ARM_CALL | grep __gnu_mcount_nc
> > 00000054 R_ARM_CALL        __gnu_mcount_nc
> > 0000016c R_ARM_CALL        __gnu_mcount_nc
> > 00000234 R_ARM_CALL        __gnu_mcount_nc
> > 0000026c R_ARM_CALL        __gnu_mcount_nc
> > 000002f4 R_ARM_CALL        __gnu_mcount_nc  
> 
> However there are 6 references in the __mcount_loc section:
> > $ readelf -R __mcount_loc arch/arm/kernel/stacktrace.o                            
> > 
> > Hex dump of section '__mcount_loc':
> >   0x00000000 24000000 54000000 6c010000 34020000 $...T...l...4...
> >   0x00000010 6c020000 f4020000                   l.......  
> 
> Note: The first and wrong offset is 0x24, which is a "bx r6" (see above
> objdump of stacktrace.o):
> >   24:	e12fff16 	bx	r6  

Interesting. Have you tried a make mrproper and tried again? Also, do
you use hardlinks with ccache?

> 
> I hacked scripts/Makefile.build to use the perl version of recordmcount,
> that works without problems.

Note, you could also just removed CONFIG_HAVE_C_RECORDMCOUNT from
arch/arm/Kconfig.

-- Steve