diff mbox

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

Message ID 1448068997-26631-3-git-send-email-sboyd@codeaurora.org
State New
Headers show

Commit Message

Stephen Boyd Nov. 21, 2015, 1:23 a.m. UTC 
The ARM compiler inserts calls to __aeabi_uidiv() and
__aeabi_idiv() when it needs to perform division on signed and
unsigned integers. If a processor has support for the udiv and
sdiv division instructions the calls to these support routines
can be replaced with those instructions. Therefore, record the
location of calls to these library functions into two sections
(one for udiv and one for sdiv) similar to how we trace calls to
mcount. When the kernel boots up it will check to see if the
processor supports the instructions and then patch the call sites
with the instruction.

Cc: Nicolas Pitre <nico@fluxnic.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Måns Rullgård <mans@mansr.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
 scripts/recordmcount.h | 335 +++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 269 insertions(+), 66 deletions(-)

Comments

Russell King - ARM Linux Nov. 21, 2015, 10:13 a.m. UTC | #1 
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.

I had assumed that this message was produced by something in the
toolchain, not something in the kernel.
Stephen Boyd Nov. 23, 2015, 8:53 p.m. UTC | #2 
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?
Steven Rostedt Nov. 23, 2015, 8:58 p.m. UTC | #3 
On Mon, 23 Nov 2015 12:53:35 -0800
Stephen Boyd <sboyd@codeaurora.org> wrote:

 
> 
> 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 believe I hit this by hitting ctrl-C during a build and then starting
it again. It's been a while so it could have been something else.

-- Steve


> 
> 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?
>
Russell King - ARM Linux Nov. 23, 2015, 9:03 p.m. UTC | #4 
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
Stephen Boyd Nov. 23, 2015, 9:16 p.m. UTC | #5 
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.
Russell King - ARM Linux Nov. 23, 2015, 9:33 p.m. UTC | #6 
On Mon, Nov 23, 2015 at 01:16:01PM -0800, Stephen Boyd wrote:
> Thanks. I don't see the prints on my system even with this config
> on top of allyesconfig. Odd.

Hmm.

It could be because I use ccache in hardlink mode to avoid the disk
overhead of having two copies and having to duplicate the file
contents.

If the kernel build thinks it can modify an object file in place, it
will lead to this, as it will end up modifying the stored ccache
file unless it specifically breaks the hardlink.
Stephen Boyd Nov. 24, 2015, 1:04 a.m. UTC | #7 
On 11/23, Russell King - ARM Linux wrote:
> On Mon, Nov 23, 2015 at 01:16:01PM -0800, Stephen Boyd wrote:
> > Thanks. I don't see the prints on my system even with this config
> > on top of allyesconfig. Odd.
> 
> Hmm.
> 
> It could be because I use ccache in hardlink mode to avoid the disk
> overhead of having two copies and having to duplicate the file
> contents.
> 
> If the kernel build thinks it can modify an object file in place, it
> will lead to this, as it will end up modifying the stored ccache
> file unless it specifically breaks the hardlink.
> 

That sounds very possible. I'd have to get ccache setup with
hardlinks to test out your theory. 

Is it supported to use ccache with hardlinks to build the kernel?
The ccache documentation makes it sounds like it will confuse
make and isn't a good idea.
diff mbox

Patch

diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
index 6e196dba748d..cab91ffc82a6 100644
--- a/scripts/recordmcount.h
+++ b/scripts/recordmcount.h
@@ -18,11 +18,13 @@ 
  *
  * Licensed under the GNU General Public License, version 2 (GPLv2).
  */
+#undef append_section
 #undef append_func
 #undef is_fake_mcount
 #undef fn_is_fake_mcount
 #undef MIPS_is_fake_mcount
 #undef mcount_adjust
+#undef add_relocation
 #undef sift_rel_mcount
 #undef nop_mcount
 #undef find_secsym_ndx
@@ -30,6 +32,7 @@ 
 #undef has_rel_mcount
 #undef tot_relsize
 #undef get_mcountsym
+#undef get_arm_sym
 #undef get_sym_str_and_relp
 #undef do_func
 #undef Elf_Addr
@@ -52,7 +55,9 @@ 
 #undef _size
 
 #ifdef RECORD_MCOUNT_64
+# define append_section		append_section64
 # define append_func		append64
+# define add_relocation		add_relocation_64
 # define sift_rel_mcount	sift64_rel_mcount
 # define nop_mcount		nop_mcount_64
 # define find_secsym_ndx	find64_secsym_ndx
@@ -62,6 +67,7 @@ 
 # define get_sym_str_and_relp	get_sym_str_and_relp_64
 # define do_func		do64
 # define get_mcountsym		get_mcountsym_64
+# define get_arm_sym		get_arm_sym_64
 # define is_fake_mcount		is_fake_mcount64
 # define fn_is_fake_mcount	fn_is_fake_mcount64
 # define MIPS_is_fake_mcount	MIPS64_is_fake_mcount
@@ -85,7 +91,9 @@ 
 # define _align			7u
 # define _size			8
 #else
+# define append_section		append_section32
 # define append_func		append32
+# define add_relocation		add_relocation_32
 # define sift_rel_mcount	sift32_rel_mcount
 # define nop_mcount		nop_mcount_32
 # define find_secsym_ndx	find32_secsym_ndx
@@ -95,6 +103,7 @@ 
 # define get_sym_str_and_relp	get_sym_str_and_relp_32
 # define do_func		do32
 # define get_mcountsym		get_mcountsym_32
+# define get_arm_sym		get_arm_sym_32
 # define is_fake_mcount		is_fake_mcount32
 # define fn_is_fake_mcount	fn_is_fake_mcount32
 # define MIPS_is_fake_mcount	MIPS32_is_fake_mcount
@@ -174,6 +183,62 @@  static int MIPS_is_fake_mcount(Elf_Rel const *rp)
 	return is_fake;
 }
 
+static void append_section(uint_t const *const mloc0,
+			   uint_t const *const mlocp,
+			   Elf_Rel const *const mrel0,
+			   Elf_Rel const *const mrelp,
+			   char const *name,
+			   unsigned int const rel_entsize,
+			   unsigned int const symsec_sh_link,
+			   uint_t *name_offp,
+			   uint_t *tp,
+			   unsigned *shnump
+		)
+{
+	Elf_Shdr mcsec;
+	uint_t name_off = *name_offp;
+	uint_t t = *tp;
+	uint_t loc_diff = (void *)mlocp - (void *)mloc0;
+	uint_t rel_diff = (void *)mrelp - (void *)mrel0;
+	unsigned shnum = *shnump;
+
+	mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
+		+ name_off);
+	mcsec.sh_type = w(SHT_PROGBITS);
+	mcsec.sh_flags = _w(SHF_ALLOC);
+	mcsec.sh_addr = 0;
+	mcsec.sh_offset = _w(t);
+	mcsec.sh_size = _w(loc_diff);
+	mcsec.sh_link = 0;
+	mcsec.sh_info = 0;
+	mcsec.sh_addralign = _w(_size);
+	mcsec.sh_entsize = _w(_size);
+	uwrite(fd_map, &mcsec, sizeof(mcsec));
+	t += loc_diff;
+
+	mcsec.sh_name = w(name_off);
+	mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
+		? w(SHT_RELA)
+		: w(SHT_REL);
+	mcsec.sh_flags = 0;
+	mcsec.sh_addr = 0;
+	mcsec.sh_offset = _w(t);
+	mcsec.sh_size   = _w(rel_diff);
+	mcsec.sh_link = w(symsec_sh_link);
+	mcsec.sh_info = w(shnum);
+	mcsec.sh_addralign = _w(_size);
+	mcsec.sh_entsize = _w(rel_entsize);
+	uwrite(fd_map, &mcsec, sizeof(mcsec));
+	t += rel_diff;
+
+	shnum += 2;
+	name_off += strlen(name) + 1;
+
+	*tp = t;
+	*shnump = shnum;
+	*name_offp = name_off;
+}
+
 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
 static void append_func(Elf_Ehdr *const ehdr,
 			Elf_Shdr *const shstr,
@@ -181,20 +246,50 @@  static void append_func(Elf_Ehdr *const ehdr,
 			uint_t const *const mlocp,
 			Elf_Rel const *const mrel0,
 			Elf_Rel const *const mrelp,
+			uint_t const *const mloc0_u,
+			uint_t const *const mlocp_u,
+			Elf_Rel const *const mrel0_u,
+			Elf_Rel const *const mrelp_u,
+			uint_t const *const mloc0_i,
+			uint_t const *const mlocp_i,
+			Elf_Rel const *const mrel0_i,
+			Elf_Rel const *const mrelp_i,
 			unsigned int const rel_entsize,
 			unsigned int const symsec_sh_link)
 {
 	/* Begin constructing output file */
-	Elf_Shdr mcsec;
 	char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
 		? ".rela__mcount_loc"
 		:  ".rel__mcount_loc";
-	unsigned const old_shnum = w2(ehdr->e_shnum);
+	char const *udiv_name = (sizeof(Elf_Rela) == rel_entsize)
+		? ".rela__udiv_loc"
+		:  ".rel__udiv_loc";
+	char const *idiv_name = (sizeof(Elf_Rela) == rel_entsize)
+		? ".rela__idiv_loc"
+		:  ".rel__idiv_loc";
+	unsigned old_shnum = w2(ehdr->e_shnum);
 	uint_t const old_shoff = _w(ehdr->e_shoff);
 	uint_t const old_shstr_sh_size   = _w(shstr->sh_size);
 	uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
-	uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
 	uint_t new_e_shoff;
+	uint_t t = _w(shstr->sh_size);
+	uint_t name_off = old_shstr_sh_size;
+	int mc = 0, udiv = 0, idiv = 0;
+	int num_sections;
+
+	if (mlocp != mloc0) {
+		t += 1 + strlen(mc_name);
+		mc = 1;
+	}
+	if (mlocp_u != mloc0_u) {
+		t += 1 + strlen(udiv_name);
+		udiv = 1;
+	}
+	if (mlocp_i != mloc0_i) {
+		t += 1 + strlen(idiv_name);
+		idiv = 1;
+	}
+	num_sections = (mc * 2) + (udiv * 2) + (idiv * 2);
 
 	shstr->sh_size = _w(t);
 	shstr->sh_offset = _w(sb.st_size);
@@ -204,8 +299,13 @@  static void append_func(Elf_Ehdr *const ehdr,
 
 	/* body for new shstrtab */
 	ulseek(fd_map, sb.st_size, SEEK_SET);
-	uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size);
-	uwrite(fd_map, mc_name, 1 + strlen(mc_name));
+	uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, name_off);
+	if (mc)
+		uwrite(fd_map, mc_name, 1 + strlen(mc_name));
+	if (udiv)
+		uwrite(fd_map, udiv_name, 1 + strlen(udiv_name));
+	if (idiv)
+		uwrite(fd_map, idiv_name, 1 + strlen(idiv_name));
 
 	/* old(modified) Elf_Shdr table, word-byte aligned */
 	ulseek(fd_map, t, SEEK_SET);
@@ -214,39 +314,38 @@  static void append_func(Elf_Ehdr *const ehdr,
 	       sizeof(Elf_Shdr) * old_shnum);
 
 	/* new sections __mcount_loc and .rel__mcount_loc */
-	t += 2*sizeof(mcsec);
-	mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
-		+ old_shstr_sh_size);
-	mcsec.sh_type = w(SHT_PROGBITS);
-	mcsec.sh_flags = _w(SHF_ALLOC);
-	mcsec.sh_addr = 0;
-	mcsec.sh_offset = _w(t);
-	mcsec.sh_size = _w((void *)mlocp - (void *)mloc0);
-	mcsec.sh_link = 0;
-	mcsec.sh_info = 0;
-	mcsec.sh_addralign = _w(_size);
-	mcsec.sh_entsize = _w(_size);
-	uwrite(fd_map, &mcsec, sizeof(mcsec));
-
-	mcsec.sh_name = w(old_shstr_sh_size);
-	mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
-		? w(SHT_RELA)
-		: w(SHT_REL);
-	mcsec.sh_flags = 0;
-	mcsec.sh_addr = 0;
-	mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t);
-	mcsec.sh_size   = _w((void *)mrelp - (void *)mrel0);
-	mcsec.sh_link = w(symsec_sh_link);
-	mcsec.sh_info = w(old_shnum);
-	mcsec.sh_addralign = _w(_size);
-	mcsec.sh_entsize = _w(rel_entsize);
-	uwrite(fd_map, &mcsec, sizeof(mcsec));
-
-	uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0);
-	uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0);
+	t += num_sections * sizeof(Elf_Shdr);
+	if (mc)
+		append_section(mloc0, mlocp, mrel0, mrelp, mc_name, rel_entsize,
+			       symsec_sh_link, &name_off, &t, &old_shnum);
+
+	/* new sections __udiv_loc and .rel__udiv_loc */
+	if (udiv)
+		append_section(mloc0_u, mlocp_u, mrel0_u, mrelp_u, udiv_name,
+			       rel_entsize, symsec_sh_link, &name_off, &t,
+			       &old_shnum);
+
+	/* new sections __idiv_loc and .rel__idiv_loc */
+	if (idiv)
+		append_section(mloc0_i, mlocp_i, mrel0_i, mrelp_i, idiv_name,
+			       rel_entsize, symsec_sh_link, &name_off, &t,
+			       &old_shnum);
+
+	if (mc) {
+		uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0);
+		uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0);
+	}
+	if (udiv) {
+		uwrite(fd_map, mloc0_u, (void *)mlocp_u - (void *)mloc0_u);
+		uwrite(fd_map, mrel0_u, (void *)mrelp_u - (void *)mrel0_u);
+	}
+	if (idiv) {
+		uwrite(fd_map, mloc0_i, (void *)mlocp_i - (void *)mloc0_i);
+		uwrite(fd_map, mrel0_i, (void *)mrelp_i - (void *)mrel0_i);
+	}
 
 	ehdr->e_shoff = _w(new_e_shoff);
-	ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum));  /* {.rel,}__mcount_loc */
+	ehdr->e_shnum = w2(num_sections + w2(ehdr->e_shnum));
 	ulseek(fd_map, 0, SEEK_SET);
 	uwrite(fd_map, ehdr, sizeof(*ehdr));
 }
@@ -273,6 +372,20 @@  static unsigned get_mcountsym(Elf_Sym const *const sym0,
 	return mcountsym;
 }
 
+static unsigned get_arm_sym(Elf_Sym const *const sym0,
+			      Elf_Rel const *relp,
+			      char const *const str0, const char *find)
+{
+	unsigned sym = 0;
+	Elf_Sym const *const symp = &sym0[Elf_r_sym(relp)];
+	char const *symname = &str0[w(symp->st_name)];
+
+	if (strcmp(find, symname) == 0)
+		sym = Elf_r_sym(relp);
+
+	return sym;
+}
+
 static void get_sym_str_and_relp(Elf_Shdr const *const relhdr,
 				 Elf_Ehdr const *const ehdr,
 				 Elf_Sym const **sym0,
@@ -296,28 +409,65 @@  static void get_sym_str_and_relp(Elf_Shdr const *const relhdr,
 	*relp = rel0;
 }
 
+static void add_relocation(Elf_Rel const *relp, uint_t *mloc0, uint_t **mlocpp,
+			   uint_t const recval, unsigned const recsym,
+			   Elf_Rel **const mrelpp, unsigned offbase,
+			   unsigned rel_entsize, unsigned const reltype)
+{
+	uint_t *mlocp = *mlocpp;
+	Elf_Rel *mrelp = *mrelpp;
+	uint_t const addend = _w(_w(relp->r_offset) - recval + mcount_adjust);
+	mrelp->r_offset = _w(offbase + ((void *)mlocp - (void *)mloc0));
+	Elf_r_info(mrelp, recsym, reltype);
+	if (rel_entsize == sizeof(Elf_Rela)) {
+		((Elf_Rela *)mrelp)->r_addend = addend;
+		*mlocp++ = 0;
+	} else
+		*mlocp++ = addend;
+
+	*mlocpp = mlocp;
+	*mrelpp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
+}
+
 /*
  * Look at the relocations in order to find the calls to mcount.
  * Accumulate the section offsets that are found, and their relocation info,
  * onto the end of the existing arrays.
  */
-static uint_t *sift_rel_mcount(uint_t *mlocp,
-			       unsigned const offbase,
+static void sift_rel_mcount(uint_t **mlocpp,
+			       uint_t *mloc_base,
 			       Elf_Rel **const mrelpp,
+			       uint_t **mlocpp_u,
+			       uint_t *mloc_base_u,
+			       Elf_Rel **const mrelpp_u,
+			       uint_t **mlocpp_i,
+			       uint_t *mloc_base_i,
+			       Elf_Rel **const mrelpp_i,
 			       Elf_Shdr const *const relhdr,
 			       Elf_Ehdr const *const ehdr,
 			       unsigned const recsym,
 			       uint_t const recval,
 			       unsigned const reltype)
 {
+	uint_t *mlocp = *mlocpp;
+	unsigned const offbase = (void *)mlocp - (void *)mloc_base;
 	uint_t *const mloc0 = mlocp;
 	Elf_Rel *mrelp = *mrelpp;
+	uint_t *mlocp_u = *mlocpp_u;
+	unsigned const offbase_u = (void *)mlocp_u - (void *)mloc_base_u;
+	uint_t *const mloc0_u = mlocp_u;
+	Elf_Rel *mrelp_u = *mrelpp_u;
+	uint_t *mlocp_i = *mlocpp_i;
+	unsigned const offbase_i = (void *)mlocp_i - (void *)mloc_base_i;
+	uint_t *const mloc0_i = mlocp_i;
+	Elf_Rel *mrelp_i = *mrelpp_i;
 	Elf_Sym const *sym0;
 	char const *str0;
 	Elf_Rel const *relp;
 	unsigned rel_entsize = _w(relhdr->sh_entsize);
 	unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
-	unsigned mcountsym = 0;
+	int arm = w2(ehdr->e_machine) == EM_ARM;
+	unsigned mcountsym = 0, udiv_sym = 0, idiv_sym =0;
 	unsigned t;
 
 	get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
@@ -326,24 +476,53 @@  static uint_t *sift_rel_mcount(uint_t *mlocp,
 		if (trace_mcount && !mcountsym)
 			mcountsym = get_mcountsym(sym0, relp, str0);
 
-		if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
-			uint_t const addend =
-				_w(_w(relp->r_offset) - recval + mcount_adjust);
-			mrelp->r_offset = _w(offbase
-				+ ((void *)mlocp - (void *)mloc0));
-			Elf_r_info(mrelp, recsym, reltype);
-			if (rel_entsize == sizeof(Elf_Rela)) {
-				((Elf_Rela *)mrelp)->r_addend = addend;
-				*mlocp++ = 0;
-			} else
-				*mlocp++ = addend;
-
-			mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
+		if (arm && !udiv_sym)
+			udiv_sym = get_arm_sym(sym0, relp, str0,
+					       "__aeabi_uidiv");
+		if (arm && !idiv_sym)
+			idiv_sym = get_arm_sym(sym0, relp, str0,
+						 "__aeabi_idiv");
+
+		if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp))
+			add_relocation(relp, mloc0, &mlocp, recval, recsym,
+				       &mrelp, offbase, rel_entsize, reltype);
+
+		if (udiv_sym == Elf_r_sym(relp)) {
+			switch (relp->r_info & 0xff) {
+			case R_ARM_PC24:
+			case 28:
+			case 29:
+				add_relocation(relp, mloc0_u, &mlocp_u, recval,
+						recsym, &mrelp_u, offbase_u,
+						rel_entsize, reltype);
+				break;
+			default:
+				break;
+			}
 		}
+
+		if (idiv_sym == Elf_r_sym(relp)) {
+			switch (relp->r_info & 0xff) {
+			case R_ARM_PC24:
+			case 28:
+			case 29:
+				add_relocation(relp, mloc0_i, &mlocp_i, recval,
+						recsym, &mrelp_i, offbase_i,
+						rel_entsize, reltype);
+				break;
+			default:
+				break;
+			}
+		}
+
 		relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
 	}
+	*mrelpp_i = mrelp_i;
+	*mrelpp_u = mrelp_u;
 	*mrelpp = mrelp;
-	return mlocp;
+	*mlocpp_i = mlocp_i;
+	*mlocpp_u = mlocp_u;
+	*mlocpp = mlocp;
 }
 
 /*
@@ -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,
 			fname);
 		succeed_file();
 	}
@@ -472,25 +651,25 @@  __has_rel_mcount(Elf_Shdr const *const relhdr,  /* is SHT_REL or SHT_RELA */
 static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
 				  Elf_Shdr const *const shdr0,
 				  char const *const shstrtab,
-				  char const *const fname)
+				  char const *const fname, const char *find)
 {
 	if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
 		return NULL;
-	return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
+	return __has_rel_mcount(relhdr, shdr0, shstrtab, fname, find);
 }
 
 
 static unsigned tot_relsize(Elf_Shdr const *const shdr0,
 			    unsigned nhdr,
 			    const char *const shstrtab,
-			    const char *const fname)
+			    const char *const fname, const char *find)
 {
 	unsigned totrelsz = 0;
 	Elf_Shdr const *shdrp = shdr0;
 	char const *txtname;
 
 	for (; nhdr; --nhdr, ++shdrp) {
-		txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname);
+		txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname, find);
 		if (txtname && is_mcounted_section_name(txtname))
 			totrelsz += _w(shdrp->sh_size);
 	}
@@ -513,7 +692,8 @@  do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
 	unsigned k;
 
 	/* Upper bound on space: assume all relevant relocs are for mcount. */
-	unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
+	unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname,
+					      "__mcount_loc");
 	Elf_Rel *const mrel0 = umalloc(totrelsz);
 	Elf_Rel *      mrelp = mrel0;
 
@@ -521,12 +701,28 @@  do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
 	uint_t *const mloc0 = umalloc(totrelsz>>1);
 	uint_t *      mlocp = mloc0;
 
+	/* Allocate for arm too */
+	Elf_Rel *const mrel0_u = umalloc(totrelsz);
+	Elf_Rel *      mrelp_u = mrel0_u;
+
+	/* 2*sizeof(address) <= sizeof(Elf_Rel) */
+	uint_t *const mloc0_u = umalloc(totrelsz>>1);
+	uint_t *      mlocp_u = mloc0_u;
+
+	/* Allocate for arm too */
+	Elf_Rel *const mrel0_i = umalloc(totrelsz);
+	Elf_Rel *      mrelp_i = mrel0_i;
+
+	/* 2*sizeof(address) <= sizeof(Elf_Rel) */
+	uint_t *const mloc0_i = umalloc(totrelsz>>1);
+	uint_t *      mlocp_i = mloc0_i;
+
 	unsigned rel_entsize = 0;
 	unsigned symsec_sh_link = 0;
 
 	for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
 		char const *const txtname = has_rel_mcount(relhdr, shdr0,
-			shstrtab, fname);
+			shstrtab, fname, "__mcount_loc");
 		if (txtname && is_mcounted_section_name(txtname)) {
 			uint_t recval = 0;
 			unsigned const recsym = find_secsym_ndx(
@@ -535,9 +731,10 @@  do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
 				ehdr);
 
 			rel_entsize = _w(relhdr->sh_entsize);
-			mlocp = sift_rel_mcount(mlocp,
-				(void *)mlocp - (void *)mloc0, &mrelp,
-				relhdr, ehdr, recsym, recval, reltype);
+			sift_rel_mcount(&mlocp, mloc0, &mrelp,
+				&mlocp_u, mloc0_u, &mrelp_u, &mlocp_i, mloc0_i,
+				&mrelp_i, relhdr, ehdr, recsym, recval,
+				reltype);
 		} else if (txtname && (warn_on_notrace_sect || make_nop)) {
 			/*
 			 * This section is ignored by ftrace, but still
@@ -546,10 +743,16 @@  do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
 			nop_mcount(relhdr, ehdr, txtname);
 		}
 	}
-	if (mloc0 != mlocp) {
+	if (mloc0 != mlocp || mloc0_u != mlocp_u || mloc0_i != mlocp_i) {
 		append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
+			    mloc0_u, mlocp_u, mrel0_u, mrelp_u,
+			    mloc0_i, mlocp_i, mrel0_i, mrelp_i,
 			    rel_entsize, symsec_sh_link);
 	}
 	free(mrel0);
 	free(mloc0);
+	free(mrel0_u);
+	free(mloc0_u);
+	free(mrel0_i);
+	free(mloc0_i);
 }