* [PATCH] mm: Outline copy_overflow()
@ 2022-02-07 10:55 Christophe Leroy
2022-02-07 13:46 ` kernel test robot
2022-02-07 20:40 ` Andrew Morton
0 siblings, 2 replies; 4+ messages in thread
From: Christophe Leroy @ 2022-02-07 10:55 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:
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
That function being a non conditional warning on an error path,
it is not worth inlining.
Outline it.
This reduces the size of vmlinux by almost 4kbytes.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
include/linux/thread_info.h | 5 +----
mm/maccess.c | 5 +++++
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 73a6f34b3847..1087d1e2be5c 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -209,10 +209,7 @@ __bad_copy_from(void);
extern void __compiletime_error("copy destination size is too small")
__bad_copy_to(void);
-static inline void copy_overflow(int size, unsigned long count)
-{
- WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
-}
+void copy_overflow(int size, unsigned long count);
static __always_inline __must_check bool
check_copy_size(const void *addr, size_t bytes, bool is_source)
diff --git a/mm/maccess.c b/mm/maccess.c
index d3f1a1f0b1c1..d15c7b2324b4 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -335,3 +335,8 @@ 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);
+}
--
2.33.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] mm: Outline copy_overflow()
2022-02-07 10:55 [PATCH] mm: Outline copy_overflow() Christophe Leroy
@ 2022-02-07 13:46 ` kernel test robot
2022-02-07 20:40 ` Andrew Morton
1 sibling, 0 replies; 4+ messages in thread
From: kernel test robot @ 2022-02-07 13:46 UTC (permalink / raw)
To: Christophe Leroy, Andrew Morton
Cc: kbuild-all, Linux Memory Management List, Christophe Leroy, linux-kernel
Hi Christophe,
I love your patch! Yet something to improve:
[auto build test ERROR on hnaz-mm/master]
url: https://github.com/0day-ci/linux/commits/Christophe-Leroy/mm-Outline-copy_overflow/20220207-190441
base: https://github.com/hnaz/linux-mm master
config: i386-randconfig-a013-20220207 (https://download.01.org/0day-ci/archive/20220207/202202072148.OAzMGrDo-lkp@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/2ae7547d08e23e529db61b3de0cb93879630a102
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Christophe-Leroy/mm-Outline-copy_overflow/20220207-190441
git checkout 2ae7547d08e23e529db61b3de0cb93879630a102
# 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 >>, old ones prefixed by <<):
>> ERROR: modpost: "copy_overflow" [drivers/usb/gadget/function/usb_f_fs.ko] undefined!
>> ERROR: modpost: "copy_overflow" [drivers/scsi/sg.ko] undefined!
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mm: Outline copy_overflow()
2022-02-07 10:55 [PATCH] mm: Outline copy_overflow() Christophe Leroy
2022-02-07 13:46 ` kernel test robot
@ 2022-02-07 20:40 ` Andrew Morton
2022-02-08 19:04 ` Christophe Leroy
1 sibling, 1 reply; 4+ messages in thread
From: Andrew Morton @ 2022-02-07 20:40 UTC (permalink / raw)
To: Christophe Leroy; +Cc: linux-kernel, linux-mm
On Mon, 7 Feb 2022 11:55:18 +0100 Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
> While building a small config with CONFIG_CC_OPTIMISE_FOR_SIZE,
> I ended up with more than 50 times the following function in vmlinux:
>
> 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
>
> That function being a non conditional warning on an error path,
> it is not worth inlining.
>
> Outline it.
"uninline" is the conventional term for this.
> This reduces the size of vmlinux by almost 4kbytes.
Did you consider uninlining check_copy_size() instead?
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] mm: Outline copy_overflow()
2022-02-07 20:40 ` Andrew Morton
@ 2022-02-08 19:04 ` Christophe Leroy
0 siblings, 0 replies; 4+ messages in thread
From: Christophe Leroy @ 2022-02-08 19:04 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-kernel, linux-mm
Le 07/02/2022 à 21:40, Andrew Morton a écrit :
> On Mon, 7 Feb 2022 11:55:18 +0100 Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
>
>> While building a small config with CONFIG_CC_OPTIMISE_FOR_SIZE,
>> I ended up with more than 50 times the following function in vmlinux:
>>
>> 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
>>
>> That function being a non conditional warning on an error path,
>> it is not worth inlining.
>>
>> Outline it.
>
> "uninline" is the conventional term for this.
>
>> This reduces the size of vmlinux by almost 4kbytes.
>
> Did you consider uninlining check_copy_size() instead?
>
If you uninline check_copy_size() you loose the benefit of constant
folding and build time overflow detection for constant sizes, and I'm
not sure __builtin_object_size() works at all if uninlined.
Christophe
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-02-07 13:46 ` kernel test robot
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