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Message-Id: <20220704123818.4828-1-alexandr.lobakin@intel.com>
Date: Mon, 4 Jul 2022 14:38:18 +0200
From: Alexander Lobakin <alexandr.lobakin@...el.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Alexander Lobakin <alexandr.lobakin@...el.com>,
linux-kernel@...r.kernel.org
Subject: Re: [lkp@...el.com: [norov:fns 9/23] include/asm-generic/percpu.h:21:44: warning: array subscript 4 is above array bounds of 'long unsigned int[4]']
From: Yury Norov <yury.norov@...il.com>
Date: Fri, 1 Jul 2022 19:33:24 -0700
> Hi Alexander,
Hi!
>
> I'm working on top of your recent cons bitmap series, and again
> received a bug report from LKP regarding one of you patches. Can
> you please look at this report?
>
> I tried reproduce it myself, but the build is failed for me:
> arch/arc/kernel/entry.S: Assembler messages:
> arch/arc/kernel/entry.S:280: Error: operand out of range (260 is not between -256 and 255)
> make[2]: *** [scripts/Makefile.build:322: arch/arc/kernel/entry-compact.o] Error 1
> make[2]: *** Waiting for unfinished jobs....
>
> If you think it's mis-attributed, we should let LKP people know that
> something is wrong on their side.
>
> Thanks,
> Yury
>
> ----- Forwarded message from kernel test robot <lkp@...el.com> -----
>
> Date: Sat, 2 Jul 2022 08:42:59 +0800
> From: kernel test robot <lkp@...el.com>
> To: Yury Norov <yury.norov@...il.com>
> Cc: kbuild-all@...ts.01.org
> Subject: [norov:fns 9/23] include/asm-generic/percpu.h:21:44: warning: array subscript 4 is above array bounds of
> 'long unsigned int[4]'
>
> tree: https://github.com/norov/linux fns
> head: 1df9509fd92a58cb37e9a419235823bbb13367de
> commit: 3e7e5baaaba78075a7f3a57432609e363bf2a486 [9/23] bitmap: don't assume compiler evaluates small mem*() builtins calls
> config: arc-randconfig-r035-20220629 (https://download.01.org/0day-ci/archive/20220702/202207020812.oTFxIVue-lkp@intel.com/config)
> compiler: arc-elf-gcc (GCC) 11.3.0
> 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/norov/linux/commit/3e7e5baaaba78075a7f3a57432609e363bf2a486
> git remote add norov https://github.com/norov/linux
> git fetch --no-tags norov fns
> git checkout 3e7e5baaaba78075a7f3a57432609e363bf2a486
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash kernel/
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
> In file included from include/linux/compiler_types.h:93,
> from <command-line>:
> kernel/sched/topology.c: In function 'build_sched_domains':
> >> include/asm-generic/percpu.h:21:44: warning: array subscript 4 is above array bounds of 'long unsigned int[4]' [-Warray-bounds]
> 21 | #define per_cpu_offset(x) (__per_cpu_offset[x])
> include/linux/compiler-gcc.h:35:33: note: in definition of macro 'RELOC_HIDE'
> 35 | (typeof(ptr)) (__ptr + (off)); \
> | ^~~
> include/linux/percpu-defs.h:236:9: note: in expansion of macro 'SHIFT_PERCPU_PTR'
> 236 | SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))); \
> | ^~~~~~~~~~~~~~~~
> include/linux/percpu-defs.h:236:33: note: in expansion of macro 'per_cpu_offset'
> 236 | SHIFT_PERCPU_PTR((ptr), per_cpu_offset((cpu))); \
> | ^~~~~~~~~~~~~~
> kernel/sched/topology.c:969:20: note: in expansion of macro 'per_cpu_ptr'
> 969 | sg->sgc = *per_cpu_ptr(sdd->sgc, cpu);
> | ^~~~~~~~~~~
> In file included from ./arch/arc/include/generated/asm/percpu.h:1,
> from include/linux/irqflags.h:17,
> from include/linux/rcupdate.h:26,
> from include/linux/rculist.h:11,
> from include/linux/sched/signal.h:5,
> from include/linux/sched/cputime.h:5,
> from kernel/sched/build_utility.c:13:
> include/asm-generic/percpu.h:19:22: note: while referencing '__per_cpu_offset'
> 19 | extern unsigned long __per_cpu_offset[NR_CPUS];
> | ^~~~~~~~~~~~~~~~
Ah, I've seen that one and tried to reproduce it hardly, but didn't
manage to do that. Then I took a look at the code mentioned here,
but again couldn't find any code pieces which would go past the
array (with CPU ID higher than 3 on a 4-CPU kernel).
I've heard that `-Warray-bounds` is still somewhat noisy and
produces a fair amount of false-positives, so that it's been even
disabled for 5.19-rc1 after being enabled during the merge window.
I'm super fine with letting lkp guys know that it's an unrelated
stuff, whom should I write to?
BTW, I didn't receive any reports from the linux-next bots and
haven't found a single over the LKML, so looks like it should be
okay in general :)
>
>
> vim +21 include/asm-generic/percpu.h
>
> ^1da177e4c3f415 Linus Torvalds 2005-04-16 20
> a875a69f8b00a38 Ingo Molnar 2006-07-03 @21 #define per_cpu_offset(x) (__per_cpu_offset[x])
> acdac87202a4081 travis@....com 2008-01-30 22 #endif
> acdac87202a4081 travis@....com 2008-01-30 23
>
> :::::: The code at line 21 was first introduced by commit
> :::::: a875a69f8b00a38b4f40d9632a4fc71a159f0e0d [PATCH] lockdep: add per_cpu_offset()
>
> :::::: TO: Ingo Molnar <mingo@...e.hu>
> :::::: CC: Linus Torvalds <torvalds@...osdl.org>
>
> --
> 0-DAY CI Kernel Test Service
> https://01.org/lkp
>
> ----- End forwarded message -----
Thanks,
Olek
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