Subject: [RFC/PATCH 2/3] recordmcount: Record locations of __aeabi_{u}idiv() calls on ARM

From: [email-masked] (Stephen Boyd)
Date: Mon, 23 Nov 2015 13:16:01 -0800

On 11/23, Russell King - ARM Linux wrote:
> 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.

That's because I copied from the perl version of recordmcount.
The C version of this tool doesn't have that nice comment.

> 
> 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
> 

Thanks. I don't see the prints on my system even with this config
on top of allyesconfig. Odd.

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