linux-kernel - Re: [RFC/PATCH 2/3] recordmcount: Record locations of __aeabi

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Message-ID: <20151123210347.GW8644@n2100.arm.linux.org.uk>
Date:	Mon, 23 Nov 2015 21:03:48 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Måns Rullgård <mans@...sr.com>,
	Arnd Bergmann <arnd@...db.de>,
	Nicolas Pitre <nico@...xnic.net>,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC/PATCH 2/3] recordmcount: Record locations of
 __aeabi_{u}idiv() calls on ARM

On Mon, Nov 23, 2015 at 12:53:35PM -0800, Stephen Boyd wrote:
> On 11/21, Russell King - ARM Linux wrote:
> > On Fri, Nov 20, 2015 at 05:23:16PM -0800, Stephen Boyd wrote:
> > > @@ -452,14 +631,14 @@ static char const *
> > >  __has_rel_mcount(Elf_Shdr const *const relhdr,  /* is SHT_REL or SHT_RELA */
> > >  		 Elf_Shdr const *const shdr0,
> > >  		 char const *const shstrtab,
> > > -		 char const *const fname)
> > > +		 char const *const fname, const char *find)
> > >  {
> > >  	/* .sh_info depends on .sh_type == SHT_REL[,A] */
> > >  	Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
> > >  	char const *const txtname = &shstrtab[w(txthdr->sh_name)];
> > >  
> > > -	if (strcmp("__mcount_loc", txtname) == 0) {
> > > -		fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
> > > +	if (strcmp(find, txtname) == 0) {
> > > +		fprintf(stderr, "warning: %s already exists: %s\n", find,
> > 
> > Oh, it's this which has been spewing that silly
> > 	"warning: __mcount_loc already exists"
> > 
> > message thousands of times in my nightly kernel builds (so much so, that
> > I've had to filter the thing out of the logs.)  Given that this is soo
> > noisy, I think first we need to get to the bottom of why this program is
> > soo noisy before we try to make it more functional.
> > 
> 
> This comment in recordmcount.pl may tell us something.
> 
> 	#
> 	# Somehow the make process can execute this script on an
> 	# object twice. If it does, we would duplicate the mcount
> 	# section and it will cause the function tracer self test
> 	# to fail. Check if the mcount section exists, and if it does,
> 	# warn and exit.
> 	#
> 	print STDERR "ERROR: $mcount_section already in $inputfile\n" .
> 	    "\tThis may be an indication that your build is corrupted.\n" .
> 	    "\tDelete $inputfile and try again. If the same object file\n" .
> 	    "\tstill causes an issue, then disable CONFIG_DYNAMIC_FTRACE.\n";
> 	exit(-1);
> 
> I don't think there's much that can be done here besides making
> it silent unless there's some verbose build flag set (-v?), but
> it is interesting that you see it spew thousands of times. I've
> never seen the error printed, but perhaps I'm not building the
> kernel the same way you are. Care to share how you're building
> and seeing these error messages?

All I get is this:

warning: __mcount_loc already exists: arch/arm/mm/mmap.o

Not the "ERROR: ... already in ..." that the above would give.

Nothing special.  It's a seeded allyesconfig built with:

$ make -k -j2 zImage modules dtbs LOADADDR=0x60008000 CONFIG_DEBUG_SECTION_MISMATCH=y O=/path/to/build/dir

The seed being:

CONFIG_MODULES=y
# CONFIG_LOCALVERSION_AUTO is not set
CONFIG_LOG_BUF_SHIFT=19
CONFIG_ZBOOT_ROM_TEXT=0x70000000
CONFIG_ZBOOT_ROM_BSS=0x61000000
CONFIG_CMDLINE="root=/dev/mmcblk0p1 rootdelay=2 ro"
CONFIG_ARCH_VEXPRESS=y
# Must not have XIP support enabled
CONFIG_XIP_KERNEL=n
# Our toolchain has no T2 support
CONFIG_THUMB2_KERNEL=n
# Disable samples - this needs linux/seccomp.h in our host environment
CONFIG_SAMPLES=n
# Disable debug info (stop the kernel getting too large)
CONFIG_DEBUG_INFO=n
# 30 Dec 2013: disable building wanxl firmware: we don't have as68k etc
CONFIG_WANXL_BUILD_FIRMWARE=n
# 14 Jan 2015: disable GCOV
CONFIG_GCOV_KERNEL=n

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