* [PATCH v4] mm: Uninline copy_overflow()
@ 2022-02-12 7:50 Christophe Leroy
2022-02-12 18:17 ` kernel test robot
0 siblings, 1 reply; 4+ messages in thread
From: Christophe Leroy @ 2022-02-12 7:50 UTC (permalink / raw)
To: Andrew Morton; +Cc: Christophe Leroy, linux-kernel, linux-mm
While building a small config with CONFIG_CC_OPTIMISE_FOR_SIZE,
I ended up with more than 50 times the following function in vmlinux
because GCC doesn't honor the 'inline' keyword:
c00243bc <copy_overflow>:
c00243bc: 94 21 ff f0 stwu r1,-16(r1)
c00243c0: 7c 85 23 78 mr r5,r4
c00243c4: 7c 64 1b 78 mr r4,r3
c00243c8: 3c 60 c0 62 lis r3,-16286
c00243cc: 7c 08 02 a6 mflr r0
c00243d0: 38 63 5e e5 addi r3,r3,24293
c00243d4: 90 01 00 14 stw r0,20(r1)
c00243d8: 4b ff 82 45 bl c001c61c <__warn_printk>
c00243dc: 0f e0 00 00 twui r0,0
c00243e0: 80 01 00 14 lwz r0,20(r1)
c00243e4: 38 21 00 10 addi r1,r1,16
c00243e8: 7c 08 03 a6 mtlr r0
c00243ec: 4e 80 00 20 blr
With -Winline, GCC tells:
/include/linux/thread_info.h:212:20: warning: inlining failed in call to 'copy_overflow': call is unlikely and code size would grow [-Winline]
copy_overflow() is a non conditional warning called by
check_copy_size() on an error path.
check_copy_size() have to remain inlined in order to benefit
from constant folding, but copy_overflow() is not worth inlining.
Uninline it when CONFIG_BUG is selected.
When CONFIG_BUG is not selected, WARN() does nothing so skip it.
This reduces the size of vmlinux by almost 4kbytes.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v4: Make copy_overflow() a no-op when CONFIG_BUG is not selected
v3: Added missing ; after EXPORT_SYMBOL()
v2: Added missing EXPORT_SYMBOL() and enhanced commit message
---
include/linux/thread_info.h | 5 ++++-
mm/maccess.c | 6 ++++++
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 73a6f34b3847..9f392ec76f2b 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -209,9 +209,12 @@ __bad_copy_from(void);
extern void __compiletime_error("copy destination size is too small")
__bad_copy_to(void);
+void __copy_overflow(int size, unsigned long count);
+
static inline void copy_overflow(int size, unsigned long count)
{
- WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
+ if (IS_ENABLED(CONFIG_BUG))
+ __copy_overflow(size, count);
}
static __always_inline __must_check bool
diff --git a/mm/maccess.c b/mm/maccess.c
index d3f1a1f0b1c1..4d46708c9a0d 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -335,3 +335,9 @@ long strnlen_user_nofault(const void __user *unsafe_addr, long count)
return ret;
}
+
+void __copy_overflow(int size, unsigned long count)
+{
+ WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
+}
+EXPORT_SYMBOL_GPL(__copy_overflow);
--
2.34.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v4] mm: Uninline copy_overflow()
2022-02-12 7:50 [PATCH v4] mm: Uninline copy_overflow() Christophe Leroy
@ 2022-02-12 18:17 ` kernel test robot
2022-02-13 18:58 ` Christophe Leroy
0 siblings, 1 reply; 4+ messages in thread
From: kernel test robot @ 2022-02-12 18:17 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 3777 bytes --]
Hi Christophe,
I love your patch! Yet something to improve:
[auto build test ERROR on linux/master]
[also build test ERROR on linus/master v5.17-rc3]
[cannot apply to hnaz-mm/master next-20220211]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Christophe-Leroy/mm-Uninline-copy_overflow/20220212-155040
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2c271fe77d52a0555161926c232cd5bc07178b39
config: i386-allyesconfig (https://download.01.org/0day-ci/archive/20220213/202202130121.dZLDqfpe-lkp(a)intel.com/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
# https://github.com/0day-ci/linux/commit/cf4474ac62f0332bd9d39f9dd74dbb5afce9a7a4
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Christophe-Leroy/mm-Uninline-copy_overflow/20220212-155040
git checkout cf4474ac62f0332bd9d39f9dd74dbb5afce9a7a4
# save the config file to linux build tree
mkdir build_dir
make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
In file included from arch/x86/include/asm/preempt.h:7,
from include/linux/preempt.h:78,
from include/linux/percpu.h:6,
from include/linux/context_tracking_state.h:5,
from include/linux/hardirq.h:5,
from drivers/net/ethernet/mellanox/mlx4/cq.c:37:
In function 'check_copy_size',
inlined from 'copy_to_user' at include/linux/uaccess.h:199:6,
inlined from 'mlx4_init_user_cqes' at drivers/net/ethernet/mellanox/mlx4/cq.c:317:9,
inlined from 'mlx4_cq_alloc' at drivers/net/ethernet/mellanox/mlx4/cq.c:394:10:
>> include/linux/thread_info.h:228:4: error: call to '__bad_copy_from' declared with attribute error: copy source size is too small
228 | __bad_copy_from();
| ^~~~~~~~~~~~~~~~~
vim +/__bad_copy_from +228 include/linux/thread_info.h
b0377fedb65280 Al Viro 2017-06-29 219
9dd819a15162f8 Kees Cook 2019-09-25 220 static __always_inline __must_check bool
b0377fedb65280 Al Viro 2017-06-29 221 check_copy_size(const void *addr, size_t bytes, bool is_source)
b0377fedb65280 Al Viro 2017-06-29 222 {
c80d92fbb67b2c Kees Cook 2021-06-17 223 int sz = __builtin_object_size(addr, 0);
b0377fedb65280 Al Viro 2017-06-29 224 if (unlikely(sz >= 0 && sz < bytes)) {
b0377fedb65280 Al Viro 2017-06-29 225 if (!__builtin_constant_p(bytes))
b0377fedb65280 Al Viro 2017-06-29 226 copy_overflow(sz, bytes);
b0377fedb65280 Al Viro 2017-06-29 227 else if (is_source)
b0377fedb65280 Al Viro 2017-06-29 @228 __bad_copy_from();
b0377fedb65280 Al Viro 2017-06-29 229 else
b0377fedb65280 Al Viro 2017-06-29 230 __bad_copy_to();
b0377fedb65280 Al Viro 2017-06-29 231 return false;
b0377fedb65280 Al Viro 2017-06-29 232 }
6d13de1489b6bf Kees Cook 2019-12-04 233 if (WARN_ON_ONCE(bytes > INT_MAX))
6d13de1489b6bf Kees Cook 2019-12-04 234 return false;
b0377fedb65280 Al Viro 2017-06-29 235 check_object_size(addr, bytes, is_source);
b0377fedb65280 Al Viro 2017-06-29 236 return true;
b0377fedb65280 Al Viro 2017-06-29 237 }
b0377fedb65280 Al Viro 2017-06-29 238
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v4] mm: Uninline copy_overflow()
2022-02-12 18:17 ` kernel test robot
@ 2022-02-13 18:58 ` Christophe Leroy
2022-02-16 8:55 ` Chen, Rong A
0 siblings, 1 reply; 4+ messages in thread
From: Christophe Leroy @ 2022-02-13 18:58 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 2708 bytes --]
Le 12/02/2022 à 19:17, kernel test robot a écrit :
> Hi Christophe,
>
> I love your patch! Yet something to improve:
>
> [auto build test ERROR on linux/master]
> [also build test ERROR on linus/master v5.17-rc3]
> [cannot apply to hnaz-mm/master next-20220211]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch]
>
> url: https://github.com/0day-ci/linux/commits/Christophe-Leroy/mm-Uninline-copy_overflow/20220212-155040
> base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2c271fe77d52a0555161926c232cd5bc07178b39
> config: i386-allyesconfig (https://download.01.org/0day-ci/archive/20220213/202202130121.dZLDqfpe-lkp(a)intel.com/config)
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> reproduce (this is a W=1 build):
> # https://github.com/0day-ci/linux/commit/cf4474ac62f0332bd9d39f9dd74dbb5afce9a7a4
> git remote add linux-review https://github.com/0day-ci/linux
> git fetch --no-tags linux-review Christophe-Leroy/mm-Uninline-copy_overflow/20220212-155040
> git checkout cf4474ac62f0332bd9d39f9dd74dbb5afce9a7a4
> # save the config file to linux build tree
> mkdir build_dir
> make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All errors (new ones prefixed by >>):
>
> In file included from arch/x86/include/asm/preempt.h:7,
> from include/linux/preempt.h:78,
> from include/linux/percpu.h:6,
> from include/linux/context_tracking_state.h:5,
> from include/linux/hardirq.h:5,
> from drivers/net/ethernet/mellanox/mlx4/cq.c:37:
> In function 'check_copy_size',
> inlined from 'copy_to_user' at include/linux/uaccess.h:199:6,
> inlined from 'mlx4_init_user_cqes' at drivers/net/ethernet/mellanox/mlx4/cq.c:317:9,
> inlined from 'mlx4_cq_alloc' at drivers/net/ethernet/mellanox/mlx4/cq.c:394:10:
>>> include/linux/thread_info.h:228:4: error: call to '__bad_copy_from' declared with attribute error: copy source size is too small
> 228 | __bad_copy_from();
> | ^~~~~~~~~~~~~~~~~
>
This looks like a bug in GCC 9.x
You get the exact same result without my patch when unselecting CONFIG_BUG
You don't get the problem with gcc 8.5
You don't get the problem with gcc 10.3
My patch itself doesn't explain getting this error.
Christophe
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v4] mm: Uninline copy_overflow()
2022-02-13 18:58 ` Christophe Leroy
@ 2022-02-16 8:55 ` Chen, Rong A
0 siblings, 0 replies; 4+ messages in thread
From: Chen, Rong A @ 2022-02-16 8:55 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 2942 bytes --]
Hi Christophe,
On 2/14/2022 2:58 AM, Christophe Leroy wrote:
>
>
> Le 12/02/2022 à 19:17, kernel test robot a écrit :
>> Hi Christophe,
>>
>> I love your patch! Yet something to improve:
>>
>> [auto build test ERROR on linux/master]
>> [also build test ERROR on linus/master v5.17-rc3]
>> [cannot apply to hnaz-mm/master next-20220211]
>> [If your patch is applied to the wrong git tree, kindly drop us a note.
>> And when submitting patch, we suggest to use '--base' as documented in
>> https://git-scm.com/docs/git-format-patch]
>>
>> url: https://github.com/0day-ci/linux/commits/Christophe-Leroy/mm-Uninline-copy_overflow/20220212-155040
>> base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2c271fe77d52a0555161926c232cd5bc07178b39
>> config: i386-allyesconfig (https://download.01.org/0day-ci/archive/20220213/202202130121.dZLDqfpe-lkp(a)intel.com/config)
>> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
>> reproduce (this is a W=1 build):
>> # https://github.com/0day-ci/linux/commit/cf4474ac62f0332bd9d39f9dd74dbb5afce9a7a4
>> git remote add linux-review https://github.com/0day-ci/linux
>> git fetch --no-tags linux-review Christophe-Leroy/mm-Uninline-copy_overflow/20220212-155040
>> git checkout cf4474ac62f0332bd9d39f9dd74dbb5afce9a7a4
>> # save the config file to linux build tree
>> mkdir build_dir
>> make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash
>>
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kernel test robot <lkp@intel.com>
>>
>> All errors (new ones prefixed by >>):
>>
>> In file included from arch/x86/include/asm/preempt.h:7,
>> from include/linux/preempt.h:78,
>> from include/linux/percpu.h:6,
>> from include/linux/context_tracking_state.h:5,
>> from include/linux/hardirq.h:5,
>> from drivers/net/ethernet/mellanox/mlx4/cq.c:37:
>> In function 'check_copy_size',
>> inlined from 'copy_to_user' at include/linux/uaccess.h:199:6,
>> inlined from 'mlx4_init_user_cqes' at drivers/net/ethernet/mellanox/mlx4/cq.c:317:9,
>> inlined from 'mlx4_cq_alloc' at drivers/net/ethernet/mellanox/mlx4/cq.c:394:10:
>>>> include/linux/thread_info.h:228:4: error: call to '__bad_copy_from' declared with attribute error: copy source size is too small
>> 228 | __bad_copy_from();
>> | ^~~~~~~~~~~~~~~~~
>>
>
> This looks like a bug in GCC 9.x
>
> You get the exact same result without my patch when unselecting CONFIG_BUG
>
> You don't get the problem with gcc 8.5
> You don't get the problem with gcc 10.3
>
> My patch itself doesn't explain getting this error.
Thanks for the detailed explanation, we'll add the error to ignore list.
Best Regards,
Rong Chen
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-02-12 7:50 [PATCH v4] mm: Uninline copy_overflow() Christophe Leroy
2022-02-12 18:17 ` kernel test robot
2022-02-13 18:58 ` Christophe Leroy
2022-02-16 8:55 ` Chen, Rong A
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