21 Apr
2016
21 Apr
'16
1:30 p.m.
I have found a bug in .../libc/string/generic/memmove.c, which is the one that
MIPS uses, since there's no specialized, optimized version for MIPS.
We're currently using uClibc v. 1.0.12, but I suspect the bug to be present in
earlier releases too.
Here's a snippet from memmove.c#memmove():
---------------------oOo---------------------
/* This test makes the forward copying code be used whenever possible.
Reduces the working set. */
if (dstp - srcp >= len) /* *Unsigned* compare! */
{
#ifndef __ARCH_HAS_BWD_MEMCPY__
/* Backward memcpy implementation cannot be used */
memcpy(dest, src, len);
#else
/* Copy from the beginning to the end. */
---------------------oOo---------------------
Given the name of the define (__ARCH_HAS_BWD_MEMCPY__) it sounds as when this is
defined, the architecture indeed has backward memcpy() support. But how come the
line is preceded by #ifndef and not #ifdef, when the code inside calls memcpy()?
Also, the first comment inside the #ifndef seems odd, since memcpy() indeed is called:
/* Backward memcpy implementation cannot be used */
Our SDK does not define __ARCH_HAS_BWD_MEMCPY__, so when memmove()
resorts to a simple memcpy() that does the wrong thing for overlapping regions,
our application fails with disastrous side-effects.
I have attached a patch that fixes this.
Please CC me in case of any inquiries/replies: rene.nielsen (at) microsemi.com
Thanks & regards,
Rene Schipp von Branitz Nielsen
21 Apr
21 Apr
6:34 p.m.
Hi Rene,
Rene Nielsen wrote,
I have found a bug in
.../libc/string/generic/memmove.c, which is the one that
MIPS uses, since there's no specialized, optimized version for MIPS.
We're currently using uClibc v. 1.0.12, but I suspect the bug to be present in
earlier releases too.
Here's a snippet from memmove.c#memmove():
---------------------oOo---------------------
/* This test makes the forward copying code be used whenever possible.
Reduces the working set. */
if (dstp - srcp >= len) /* *Unsigned* compare! */
{
#ifndef __ARCH_HAS_BWD_MEMCPY__
/* Backward memcpy implementation cannot be used */
memcpy(dest, src, len);
#else
/* Copy from the beginning to the end. */
---------------------oOo---------------------
Given the name of the define (__ARCH_HAS_BWD_MEMCPY__) it sounds as when this is
defined, the architecture indeed has backward memcpy() support. But how come the
line is preceded by #ifndef and not #ifdef, when the code inside calls memcpy()?
Also, the first comment inside the #ifndef seems odd, since memcpy() indeed is called:
/* Backward memcpy implementation cannot be used */
Our SDK does not define __ARCH_HAS_BWD_MEMCPY__, so when memmove()
resorts to a simple memcpy() that does the wrong thing for overlapping regions,
our application fails with disastrous side-effects.
I have attached a patch that fixes this.
Please CC me in case of any inquiries/replies: rene.nielsen (at) microsemi.com
You are right, there is no special MIPS version for memmove().
The __ARCH_HAS_BWD_MEMCPY__ symbols was added in 2008 by this
commit e4f55f33f69fce85099dd5936cc74856aa1b453d. I would rather say,
that a default memcpy is used and there was a change for MIPS
recently.
Can you either try 1.0.9 or revert
2636b17616a19d628c3dbc373ebae67ef6e2b1f6 from 1.0.14?
The change to add MIPSr6 support ported from glibc and submitted by
Steve Ellcey <sellcey(a)imgtec.com> seems to trigger a problem with
old kernels on MIPS32 systems. If you search the mailinglist we had
some reports in the past, but I still couldn't reproduce the issue
to report to Steve.
Can you create a small test program showing your problem?
Something for the included test-suite would be really great.
What MIPS system do you use? MIPS32r2? little or big endian?
hard or soft-float toolchain? Which kernel version?
thanks
Waldemar
25 Apr
25 Apr
2:28 p.m.
Thanks for your swift reply, Waldemar!
We're using a flavor of MIPS32r2 called MIPS 24KEc. It's running little-endian
with soft-floats, kernel version 3.14.
I have attached a tiny program (test.c) that fails (see fail.txt) on uClibc v. 1.0.12
without the patch I attached to my previous post.
Reverting to v. 1.0.9 also solves the problem!
Thanks,
René (rene.nielsen (at) microsemi.com)
-----Original Message-----
From: Waldemar Brodkorb [mailto:wbx@uclibc-ng.org]
Sent: 21. april 2016 20:34
To: Rene Nielsen <rene.nielsen(a)microsemi.com>
Cc: devel(a)uclibc-ng.org
Subject: Re: [uclibc-ng-devel] memmove() is failing on MIPS CPU
EXTERNAL EMAIL
Hi Rene,
Rene Nielsen wrote,
I have found a bug in
.../libc/string/generic/memmove.c, which is the
one that MIPS uses, since there's no specialized, optimized version for MIPS.
We're currently using uClibc v. 1.0.12, but I suspect the bug to be
present in earlier releases too.
Here's a snippet from memmove.c#memmove():
---------------------oOo---------------------
/* This test makes the forward copying code be used whenever possible.
Reduces the working set. */
if (dstp - srcp >= len) /* *Unsigned* compare! */
{
#ifndef __ARCH_HAS_BWD_MEMCPY__
/* Backward memcpy implementation cannot be used */
memcpy(dest, src, len);
#else
/* Copy from the beginning to the end. */
---------------------oOo---------------------
Given the name of the define (__ARCH_HAS_BWD_MEMCPY__) it sounds as
when this is defined, the architecture indeed has backward memcpy()
support. But how come the line is preceded by #ifndef and not #ifdef, when the code
inside calls memcpy()?
Also, the first comment inside the #ifndef seems odd, since memcpy() indeed is called:
/* Backward memcpy implementation cannot be used */
Our SDK does not define __ARCH_HAS_BWD_MEMCPY__, so when memmove()
resorts to a simple memcpy() that does the wrong thing for overlapping
regions, our application fails with disastrous side-effects.
I have attached a patch that fixes this.
Please CC me in case of any inquiries/replies: rene.nielsen (at)
microsemi.com
You are right, there is no special MIPS version for memmove().
The __ARCH_HAS_BWD_MEMCPY__ symbols was added in 2008 by this commit
e4f55f33f69fce85099dd5936cc74856aa1b453d. I would rather say, that a default memcpy is
used and there was a change for MIPS recently.
Can you either try 1.0.9 or revert
from 1.0.14?
The change to add MIPSr6 support ported from glibc and submitted by Steve Ellcey
<sellcey(a)imgtec.com> seems to trigger a problem with old kernels on MIPS32 systems.
If you search the mailinglist we had some reports in the past, but I still couldn't
reproduce the issue to report to Steve.
Can you create a small test program showing your problem?
Something for the included test-suite would be really great.
What MIPS system do you use? MIPS32r2? little or big endian?
hard or soft-float toolchain? Which kernel version?
thanks
Waldemar
26 Apr
26 Apr
6:47 a.m.
Hi Rene,
Rene Nielsen wrote,
Thanks for your swift reply, Waldemar!
We're using a flavor of MIPS32r2 called MIPS 24KEc. It's running little-endian
with soft-floats, kernel version 3.14.
I have attached a tiny program (test.c) that fails (see fail.txt) on uClibc v. 1.0.12
without the patch I attached to my previous post.
Reverting to v. 1.0.9 also solves the problem!
It is okay to apply your test with following header:
# Copyright (C) 2016 Rene Nielsen <rene.nielsen(a)microsemi.com>
# Licensed under the LGPL v2.1, see the file COPYING.LIB in this
# tarball.
I couldn't reproduce the failure, yet. Tried mips32 little endian
with soft-float and MIPS32r2 in Qemu. binutils 2.25.1/gcc 5.3.0
and Linux Kernel 4.4.6.
Which binutils/gcc version are you using? Do you remove the FPU
emulation from the kernel?
I will try with older Kernels next as I am still unsure how to
reproduce the failure.
best regards
Waldemar
8:03 a.m.
Thanks for taking this seriously! And yes, please apply the header, you mentioned, to the
test.
Here's a list of the host and target packages we use for the rootfs and the kernel,
respectively:
Host, rootfs (Linux XXX 3.13.0-78-generic #122-Ubuntu SMP Mon Feb 1 23:11:33 UTC 2016
x86_64 x86_64 x86_64 GNU/Linux):
autoconf-2.69
automake-1.15
binutils-2.24
buildroot-2016.05-git
cmake-3.4.3
fakeroot_1.20.2
gcc-5.3.0
gmp-6.1.0
libtool-2.4.6
m4-1.4.17
mpc-1.0.3
mpfr-3.1.4
pkgconf-0.9.12
xz-5.2.2
Target, rootfs:
busybox-1.24.1
dropbear-2015.71
hiawatha-10.0
iptables-1.6.0
libevent-2.0.22-stable
libfcgi-2.4.0
libupnp-1.6.19
linux-headers-3.14.63
mbedtls-2.2.1
mtd-1.5.2
netsnmp-5.7.3
ntp-4.2.8p6
strace-4.11
uclibc-1.0.12
xz-embedded-20130513
zlib-1.2.8
Host, kernel:
autoconf-2.69
automake-1.15
binutils-2.24
buildroot-2016.05-git
cmake-3.4.3
fakeroot_1.20.2
gcc-5.3.0
gmp-6.1.0
kmod-22
libtool-2.4.6
lz4-r131
lzo-2.09
lzop-1.03
m4-1.4.17
mpc-1.0.3
mpfr-3.1.4
pkgconf-0.9.12
squashfs4.3
xz-5.2.2
zlib-1.2.8
Target, kernel:
linux-headers-3.14.63
mbedtls-2.2.1
uclibc-1.0.12
zlib-1.2.8
And here's a list of selected settings from the .config for the kernel:
CONFIG_MIPS=y
CONFIG_RWSEM_GENERIC_SPINLOCK=y
CONFIG_GENERIC_HWEIGHT=y
CONFIG_GENERIC_CALIBRATE_DELAY=y
CONFIG_SCHED_OMIT_FRAME_POINTER=y
CONFIG_BOOT_RAW=y
CONFIG_CEVT_R4K=y
CONFIG_CSRC_R4K=y
CONFIG_DMA_NONCOHERENT=y
CONFIG_NEED_DMA_MAP_STATE=y
CONFIG_CPU_LITTLE_ENDIAN=y
CONFIG_SYS_SUPPORTS_BIG_ENDIAN=y
CONFIG_SYS_SUPPORTS_LITTLE_ENDIAN=y
CONFIG_IRQ_CPU=y
CONFIG_MIPS_L1_CACHE_SHIFT=5
CONFIG_CPU_MIPS32_R2=y
CONFIG_SYS_HAS_CPU_MIPS32_R2=y
CONFIG_CPU_MIPS32=y
CONFIG_CPU_MIPSR2=y
CONFIG_SYS_SUPPORTS_32BIT_KERNEL=y
CONFIG_CPU_SUPPORTS_32BIT_KERNEL=y
CONFIG_HARDWARE_WATCHPOINTS=y
CONFIG_32BIT=y
CONFIG_PAGE_SIZE_4KB=y
CONFIG_FORCE_MAX_ZONEORDER=11
CONFIG_CPU_HAS_PREFETCH=y
CONFIG_CPU_GENERIC_DUMP_TLB=y
CONFIG_CPU_R4K_FPU=y
CONFIG_CPU_R4K_CACHE_TLB=y
CONFIG_MIPS_MT_DISABLED=y
CONFIG_CPU_HAS_SYNC=y
CONFIG_CPU_SUPPORTS_HIGHMEM=y
CONFIG_ARCH_FLATMEM_ENABLE=y
CONFIG_FLATMEM=y
CONFIG_FLAT_NODE_MEM_MAP=y
CONFIG_HAVE_MEMBLOCK=y
CONFIG_HAVE_MEMBLOCK_NODE_MAP=y
CONFIG_ARCH_DISCARD_MEMBLOCK=y
CONFIG_PAGEFLAGS_EXTENDED=y
CONFIG_SPLIT_PTLOCK_CPUS=4
CONFIG_COMPACTION=y
CONFIG_MIGRATION=y
CONFIG_ZONE_DMA_FLAG=0
CONFIG_VIRT_TO_BUS=y
CONFIG_DEFAULT_MMAP_MIN_ADDR=4096
CONFIG_CROSS_MEMORY_ATTACH=y
CONFIG_NEED_PER_CPU_KM=y
CONFIG_HZ_250=y
CONFIG_SYS_SUPPORTS_ARBIT_HZ=y
CONFIG_HZ=250
CONFIG_PREEMPT_NONE=y
CONFIG_SECCOMP=y
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_STACKTRACE_SUPPORT=y
CONFIG_DEFCONFIG_LIST="/lib/modules/$UNAME_RELEASE/.config"
CONFIG_IRQ_WORK=y
CONFIG_BUILDTIME_EXTABLE_SORT=y
Please don't hesitate to write me, if you need additional info.
Thanks,
René
-----Original Message-----
From: Waldemar Brodkorb [mailto:wbx@uclibc-ng.org]
Sent: 26. april 2016 08:48
To: Rene Nielsen <rene.nielsen(a)microsemi.com>
Cc: Waldemar Brodkorb <wbx(a)uclibc-ng.org>rg>; devel(a)uclibc-ng.org
Subject: Re: [uclibc-ng-devel] memmove() is failing on MIPS CPU
EXTERNAL EMAIL
Hi Rene,
Rene Nielsen wrote,
Thanks for your swift reply, Waldemar!
We're using a flavor of MIPS32r2 called MIPS 24KEc. It's running little-endian
with soft-floats, kernel version 3.14.
I have attached a tiny program (test.c) that fails (see fail.txt) on uClibc v. 1.0.12
without the patch I attached to my previous post.
Reverting to v. 1.0.9 also solves the problem!
It is okay to apply your test with following header:
# Copyright (C) 2016 Rene Nielsen <rene.nielsen(a)microsemi.com> # Licensed under the
LGPL v2.1, see the file COPYING.LIB in this # tarball.
I couldn't reproduce the failure, yet. Tried mips32 little endian with soft-float and
MIPS32r2 in Qemu. binutils 2.25.1/gcc 5.3.0 and Linux Kernel 4.4.6.
Which binutils/gcc version are you using? Do you remove the FPU emulation from the
kernel?
I will try with older Kernels next as I am still unsure how to reproduce the failure.
best regards
Waldemar
2:23 p.m.
I've also experienced the same issues described by Rene. Up until now
I've been applying the patches that entware-ng/optware-ng use which
revert the mipsel changes between 1.0.9 and 1.0.10.
Without Rene's patch, or reverting those mipsel commits, Rene's test.c
fails to run, and experiences same error's he experiences.
With his patch it is working as expected.
Note: with or without patching, the static "test" binary I make works
with qemu on x64_86 machine. It's only when I run it on the actual
mipsel hardware that it fails. So testing with qemu for whatever reason
is not an indication in this case of how it will work on the actual
hardware.
kernel 2.6.22.19
binutils 2.25.1
gcc 5.3.0
mips32 soft-float
I'm working with routers like entware-ng/optware-ng, so am also stuck on
the same kernel they are. I know entware-ng is using cross-tools-ng for
their toolchain. I am using buildroot for mine.
thanks,
Lance
20 May
20 May
11:17 a.m.
On Thu, Apr 21, 2016 at 4:30 PM, Rene Nielsen
<rene.nielsen(a)microsemi.com> wrote:
I have found a bug in
.../libc/string/generic/memmove.c, which is the one that
MIPS uses, since there's no specialized, optimized version for MIPS.
We're currently using uClibc v. 1.0.12, but I suspect the bug to be present in
earlier releases too.
Here's a snippet from memmove.c#memmove():
---------------------oOo---------------------
/* This test makes the forward copying code be used whenever possible.
Reduces the working set. */
if (dstp - srcp >= len) /* *Unsigned* compare! */
{
#ifndef __ARCH_HAS_BWD_MEMCPY__
/* Backward memcpy implementation cannot be used */
memcpy(dest, src, len);
#else
/* Copy from the beginning to the end. */
---------------------oOo---------------------
Given the name of the define (__ARCH_HAS_BWD_MEMCPY__) it sounds as when this is
defined, the architecture indeed has backward memcpy() support. But how come the
line is preceded by #ifndef and not #ifdef, when the code inside calls memcpy()?
Also, the first comment inside the #ifndef seems odd, since memcpy() indeed is called:
/* Backward memcpy implementation cannot be used */
Our SDK does not define __ARCH_HAS_BWD_MEMCPY__, so when memmove()
resorts to a simple memcpy() that does the wrong thing for overlapping regions,
our application fails with disastrous side-effects.
I have attached a patch that fixes this.
Hi Rene!
I am Optware-ng project maintainer. I have tried your patch to see if
it fixes memset/memcpy related issue we were having on mipsel (e.g.,
see transmission issue
https://github.com/Optware/Optware-ng/issues/53). Unfortunately, even
though your test passes fine with 'memmove() succeeded', transmission
still crashes after a while when a torrent is added, so I had to
restore the old patch that reverted memcpy.S/memset.S to
pre-2636b17616 (e3c3bf2b580), which fixed the issue. Probably, even
with your patch, there's still something wrong with memcpy.S/memset.S.
Regards,
Alex
29 May
29 May
7:46 a.m.
Hi Alex,
Alex Potapenko wrote,
On Thu, Apr 21, 2016 at 4:30 PM, Rene Nielsen
<rene.nielsen(a)microsemi.com> wrote:
Can you please try uClibc-ng 1.0.15 and disable
UCLIBC_USE_MIPS_PREFETCH in your build?
We identified prefetch as the problematic instructions on the
combination of MIPS CPU, kernel and uClibc-ng.
It is not perfect, but a valid workaround, until we find the reason
for the problems.
Thanks in advance,
Waldemar
I have found a bug in
.../libc/string/generic/memmove.c, which is the one that
MIPS uses, since there's no specialized, optimized version for MIPS.
We're currently using uClibc v. 1.0.12, but I suspect the bug to be present in
earlier releases too.
Here's a snippet from memmove.c#memmove():
---------------------oOo---------------------
/* This test makes the forward copying code be used whenever possible.
Reduces the working set. */
if (dstp - srcp >= len) /* *Unsigned* compare! */
{
#ifndef __ARCH_HAS_BWD_MEMCPY__
/* Backward memcpy implementation cannot be used */
memcpy(dest, src, len);
#else
/* Copy from the beginning to the end. */
---------------------oOo---------------------
Given the name of the define (__ARCH_HAS_BWD_MEMCPY__) it sounds as when this is
defined, the architecture indeed has backward memcpy() support. But how come the
line is preceded by #ifndef and not #ifdef, when the code inside calls memcpy()?
Also, the first comment inside the #ifndef seems odd, since memcpy() indeed is called:
/* Backward memcpy implementation cannot be used */
Our SDK does not define __ARCH_HAS_BWD_MEMCPY__, so when memmove()
resorts to a simple memcpy() that does the wrong thing for overlapping regions,
our application fails with disastrous side-effects.
I have attached a patch that fixes this.
Hi Rene!
I am Optware-ng project maintainer. I have tried your patch to see if
it fixes memset/memcpy related issue we were having on mipsel (e.g.,
see transmission issue
https://github.com/Optware/Optware-ng/issues/53). Unfortunately, even
though your test passes fine with 'memmove() succeeded', transmission
still crashes after a while when a torrent is added, so I had to
restore the old patch that reverted memcpy.S/memset.S to
pre-2636b17616 (e3c3bf2b580), which fixed the issue. Probably, even
with your patch, there's still something wrong with memcpy.S/memset.S.
10:10 a.m.
Hi Waldemar!
On Sun, May 29, 2016 at 10:46 AM, Waldemar Brodkorb <wbx(a)uclibc-ng.org> wrote:
Can you please try uClibc-ng 1.0.15 and disable
UCLIBC_USE_MIPS_PREFETCH in your build?
We identified prefetch as the problematic instructions on the
combination of MIPS CPU, kernel and uClibc-ng.
It is not perfect, but a valid workaround, until we find the reason
for the problems.
I confirm that disabling UCLIBC_USE_MIPS_PREFETCH in uClibc-ng 1.0.15
does the trick, so you're on the right track!
Thanks,
Alex
2882
days inactive
2920
days old
8 comments
4 participants
participants (4)
-
Alex Potapenko -
Lance Fredrickson -
Rene Nielsen -
Waldemar Brodkorb