* [PATCH v3] mm/sparsemem: Fix 'mem_section' will never be NULL gcc 12 warning
@ 2022-03-30 20:59 Waiman Long
2022-03-31 15:54 ` kernel test robot
0 siblings, 1 reply; 4+ messages in thread
From: Waiman Long @ 2022-03-30 20:59 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, Kirill A . Shutemov, Ingo Molnar,
Justin Forbes, Rafael Aquini, Waiman Long
The gcc 12 compiler reports a "'mem_section' will never be NULL"
warning on the following code:
static inline struct mem_section *__nr_to_section(unsigned long nr)
{
#ifdef CONFIG_SPARSEMEM_EXTREME
if (!mem_section)
return NULL;
#endif
if (!mem_section[SECTION_NR_TO_ROOT(nr)])
return NULL;
:
It happens with CONFIG_SPARSEMEM_EXTREME off. The mem_section
definition is
#ifdef CONFIG_SPARSEMEM_EXTREME
extern struct mem_section **mem_section;
#else
extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
#endif
In the !CONFIG_SPARSEMEM_EXTREME case, mem_section
is a static 2-dimensional array and so the check
"!mem_section[SECTION_NR_TO_ROOT(nr)]" doesn't make sense.
Fix this warning by moving the "!mem_section[SECTION_NR_TO_ROOT(nr)]"
check up inside the CONFIG_SPARSEMEM_EXTREME block.
Fixes: 3e347261a80b ("sparsemem extreme implementation")
Reported-by: Justin Forbes <jforbes@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
---
include/linux/mmzone.h | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 962b14d403e8..8a89efe47571 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1398,11 +1398,9 @@ static inline unsigned long *section_to_usemap(struct mem_section *ms)
static inline struct mem_section *__nr_to_section(unsigned long nr)
{
#ifdef CONFIG_SPARSEMEM_EXTREME
- if (!mem_section)
+ if (!mem_section || !mem_section[SECTION_NR_TO_ROOT(nr)])
return NULL;
#endif
- if (!mem_section[SECTION_NR_TO_ROOT(nr)])
- return NULL;
return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
}
extern size_t mem_section_usage_size(void);
--
2.27.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v3] mm/sparsemem: Fix 'mem_section' will never be NULL gcc 12 warning
2022-03-30 20:59 [PATCH v3] mm/sparsemem: Fix 'mem_section' will never be NULL gcc 12 warning Waiman Long
@ 2022-03-31 15:54 ` kernel test robot
2022-03-31 16:05 ` Waiman Long
2022-03-31 17:33 ` Waiman Long
0 siblings, 2 replies; 4+ messages in thread
From: kernel test robot @ 2022-03-31 15:54 UTC (permalink / raw)
To: Waiman Long, Andrew Morton
Cc: kbuild-all, Linux Memory Management List, linux-kernel,
Kirill A . Shutemov, Ingo Molnar, Justin Forbes, Rafael Aquini,
Waiman Long
Hi Waiman,
I love your patch! Perhaps something to improve:
[auto build test WARNING on hnaz-mm/master]
url: https://github.com/intel-lab-lkp/linux/commits/Waiman-Long/mm-sparsemem-Fix-mem_section-will-never-be-NULL-gcc-12-warning/20220331-050049
base: https://github.com/hnaz/linux-mm master
config: arm-randconfig-c024-20220330 (https://download.01.org/0day-ci/archive/20220331/202203312327.XGeCiD5T-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/intel-lab-lkp/linux/commit/2098f1d78cde338e81b3ba596ea39f37824e496e
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Waiman-Long/mm-sparsemem-Fix-mem_section-will-never-be-NULL-gcc-12-warning/20220331-050049
git checkout 2098f1d78cde338e81b3ba596ea39f37824e496e
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arm SHELL=/bin/bash security/keys/encrypted-keys/
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All warnings (new ones prefixed by >>):
In file included from include/linux/gfp.h:6,
from include/linux/umh.h:4,
from include/linux/kmod.h:9,
from include/linux/module.h:17,
from security/keys/encrypted-keys/encrypted.c:15:
security/keys/encrypted-keys/encrypted.c: In function 'derived_key_encrypt.constprop':
>> include/linux/mmzone.h:1432:23: warning: array subscript 32 is outside array bounds of 'struct mem_section[32][1]' [-Warray-bounds]
1432 | unsigned long map = section->section_mem_map;
| ^~~
include/linux/mmzone.h:1390:27: note: while referencing 'mem_section'
1390 | extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
| ^~~~~~~~~~~
vim +1432 include/linux/mmzone.h
29751f6991e845 Andy Whitcroft 2005-06-23 1429
29751f6991e845 Andy Whitcroft 2005-06-23 1430 static inline struct page *__section_mem_map_addr(struct mem_section *section)
29751f6991e845 Andy Whitcroft 2005-06-23 1431 {
29751f6991e845 Andy Whitcroft 2005-06-23 @1432 unsigned long map = section->section_mem_map;
29751f6991e845 Andy Whitcroft 2005-06-23 1433 map &= SECTION_MAP_MASK;
29751f6991e845 Andy Whitcroft 2005-06-23 1434 return (struct page *)map;
29751f6991e845 Andy Whitcroft 2005-06-23 1435 }
29751f6991e845 Andy Whitcroft 2005-06-23 1436
--
0-DAY CI Kernel Test Service
https://01.org/lkp
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v3] mm/sparsemem: Fix 'mem_section' will never be NULL gcc 12 warning
2022-03-31 15:54 ` kernel test robot
@ 2022-03-31 16:05 ` Waiman Long
2022-03-31 17:33 ` Waiman Long
1 sibling, 0 replies; 4+ messages in thread
From: Waiman Long @ 2022-03-31 16:05 UTC (permalink / raw)
To: kernel test robot, Andrew Morton
Cc: kbuild-all, Linux Memory Management List, linux-kernel,
Kirill A . Shutemov, Ingo Molnar, Justin Forbes, Rafael Aquini
On 3/31/22 11:54, kernel test robot wrote:
> Hi Waiman,
>
> I love your patch! Perhaps something to improve:
>
> [auto build test WARNING on hnaz-mm/master]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Waiman-Long/mm-sparsemem-Fix-mem_section-will-never-be-NULL-gcc-12-warning/20220331-050049
> base: https://github.com/hnaz/linux-mm master
> config: arm-randconfig-c024-20220330 (https://download.01.org/0day-ci/archive/20220331/202203312327.XGeCiD5T-lkp@intel.com/config)
> compiler: arm-linux-gnueabi-gcc (GCC) 11.2.0
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # https://github.com/intel-lab-lkp/linux/commit/2098f1d78cde338e81b3ba596ea39f37824e496e
> git remote add linux-review https://github.com/intel-lab-lkp/linux
> git fetch --no-tags linux-review Waiman-Long/mm-sparsemem-Fix-mem_section-will-never-be-NULL-gcc-12-warning/20220331-050049
> git checkout 2098f1d78cde338e81b3ba596ea39f37824e496e
> # save the config file to linux build tree
> mkdir build_dir
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arm SHELL=/bin/bash security/keys/encrypted-keys/
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/gfp.h:6,
> from include/linux/umh.h:4,
> from include/linux/kmod.h:9,
> from include/linux/module.h:17,
> from security/keys/encrypted-keys/encrypted.c:15:
> security/keys/encrypted-keys/encrypted.c: In function 'derived_key_encrypt.constprop':
>>> include/linux/mmzone.h:1432:23: warning: array subscript 32 is outside array bounds of 'struct mem_section[32][1]' [-Warray-bounds]
> 1432 | unsigned long map = section->section_mem_map;
> | ^~~
> include/linux/mmzone.h:1390:27: note: while referencing 'mem_section'
> 1390 | extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
> | ^~~~~~~~~~~
>
>
> vim +1432 include/linux/mmzone.h
>
> 29751f6991e845 Andy Whitcroft 2005-06-23 1429
> 29751f6991e845 Andy Whitcroft 2005-06-23 1430 static inline struct page *__section_mem_map_addr(struct mem_section *section)
> 29751f6991e845 Andy Whitcroft 2005-06-23 1431 {
> 29751f6991e845 Andy Whitcroft 2005-06-23 @1432 unsigned long map = section->section_mem_map;
> 29751f6991e845 Andy Whitcroft 2005-06-23 1433 map &= SECTION_MAP_MASK;
> 29751f6991e845 Andy Whitcroft 2005-06-23 1434 return (struct page *)map;
> 29751f6991e845 Andy Whitcroft 2005-06-23 1435 }
> 29751f6991e845 Andy Whitcroft 2005-06-23 1436
I think this is a pre-existing warning. It is not caused by my patch,
but I will take a look what cause the warning.
Thanks,
Longman
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v3] mm/sparsemem: Fix 'mem_section' will never be NULL gcc 12 warning
2022-03-31 15:54 ` kernel test robot
2022-03-31 16:05 ` Waiman Long
@ 2022-03-31 17:33 ` Waiman Long
1 sibling, 0 replies; 4+ messages in thread
From: Waiman Long @ 2022-03-31 17:33 UTC (permalink / raw)
To: kernel test robot, Andrew Morton
Cc: kbuild-all, Linux Memory Management List, linux-kernel,
Kirill A . Shutemov, Ingo Molnar, Justin Forbes, Rafael Aquini
On 3/31/22 11:54, kernel test robot wrote:
> Hi Waiman,
>
> I love your patch! Perhaps something to improve:
>
> [auto build test WARNING on hnaz-mm/master]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Waiman-Long/mm-sparsemem-Fix-mem_section-will-never-be-NULL-gcc-12-warning/20220331-050049
> base: https://github.com/hnaz/linux-mm master
> config: arm-randconfig-c024-20220330 (https://download.01.org/0day-ci/archive/20220331/202203312327.XGeCiD5T-lkp@intel.com/config)
> compiler: arm-linux-gnueabi-gcc (GCC) 11.2.0
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # https://github.com/intel-lab-lkp/linux/commit/2098f1d78cde338e81b3ba596ea39f37824e496e
> git remote add linux-review https://github.com/intel-lab-lkp/linux
> git fetch --no-tags linux-review Waiman-Long/mm-sparsemem-Fix-mem_section-will-never-be-NULL-gcc-12-warning/20220331-050049
> git checkout 2098f1d78cde338e81b3ba596ea39f37824e496e
> # save the config file to linux build tree
> mkdir build_dir
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arm SHELL=/bin/bash security/keys/encrypted-keys/
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/gfp.h:6,
> from include/linux/umh.h:4,
> from include/linux/kmod.h:9,
> from include/linux/module.h:17,
> from security/keys/encrypted-keys/encrypted.c:15:
> security/keys/encrypted-keys/encrypted.c: In function 'derived_key_encrypt.constprop':
>>> include/linux/mmzone.h:1432:23: warning: array subscript 32 is outside array bounds of 'struct mem_section[32][1]' [-Warray-bounds]
> 1432 | unsigned long map = section->section_mem_map;
> | ^~~
> include/linux/mmzone.h:1390:27: note: while referencing 'mem_section'
> 1390 | extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
> | ^~~~~~~~~~~
>
>
> vim +1432 include/linux/mmzone.h
>
> 29751f6991e845 Andy Whitcroft 2005-06-23 1429
> 29751f6991e845 Andy Whitcroft 2005-06-23 1430 static inline struct page *__section_mem_map_addr(struct mem_section *section)
> 29751f6991e845 Andy Whitcroft 2005-06-23 1431 {
> 29751f6991e845 Andy Whitcroft 2005-06-23 @1432 unsigned long map = section->section_mem_map;
> 29751f6991e845 Andy Whitcroft 2005-06-23 1433 map &= SECTION_MAP_MASK;
> 29751f6991e845 Andy Whitcroft 2005-06-23 1434 return (struct page *)map;
> 29751f6991e845 Andy Whitcroft 2005-06-23 1435 }
> 29751f6991e845 Andy Whitcroft 2005-06-23 1436
>
This warning happens with !CONFIG_SPARSEMEM_VMEMMAP && CONFIG_SPARSEMEM.
In this case, __section_mem_map_addr() is used only by __pfn_to_page()
and __page_to_pfn(). My patch only modifies __nr_to_section. In this
particular case, it is removing The !mem_section[32] check. Perhaps it
is somewhat equivalent to a (sec >= 32) check for gcc 11.2. However,
this check will cause a warning in gcc 12. I will update the patch to
add an explicit (sec >= NR_SECTION_ROOTS) then.
Thanks,
Longman
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-03-30 20:59 [PATCH v3] mm/sparsemem: Fix 'mem_section' will never be NULL gcc 12 warning Waiman Long
2022-03-31 15:54 ` kernel test robot
2022-03-31 16:05 ` Waiman Long
2022-03-31 17:33 ` Waiman Long
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