RE: arch/riscv/kernel/hibernate.c:76:65: warning: array subscript -1 is outside array bounds of 'const void[]'

[JeeHeng Sia]

Hi,

I followed the reproduction steps provided at the link: https://download.01.org/0day-ci/archive/20231019/202310190159.mAUo9iEX-lkp@xxxxxxxxx/reproduce to download the Linux kernel, compiler version, and the config found here: https://download.01.org/0day-ci/archive/20231019/202310190159.mAUo9iEX-lkp@xxxxxxxxx/config.
Indeed, I was able to reproduce the issue, but only with kernel v6.3-rc1.

When I tested with the same compiler version and config on kernel v6.6-rc6, I found no issues. Given these findings, do you believe it's still necessary to address the problem?

Thanks
Regards
Jee Heng

> -----Original Message-----
> From: kernel test robot <lkp@xxxxxxxxx>
> Sent: Thursday, October 19, 2023 1:23 AM
> To: JeeHeng Sia <jeeheng.sia@xxxxxxxxxxxxxxxx>
> Cc: oe-kbuild-all@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Palmer Dabbelt <palmer@xxxxxxxxxxxx>; Leyfoon Tan
> <leyfoon.tan@xxxxxxxxxxxxxxxx>; Mason Huo <mason.huo@xxxxxxxxxxxxxxxx>; Conor Dooley <conor.dooley@xxxxxxxxxxxxx>;
> Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> Subject: arch/riscv/kernel/hibernate.c:76:65: warning: array subscript -1 is outside array bounds of 'const void[]'
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   06dc10eae55b5ceabfef287a7e5f16ceea204aa0
> commit: c0317210012e3b985779ddd92a7c5db8424e1e97 RISC-V: Add arch functions to support hibernation/suspend-to-disk
> date:   6 months ago
> config: riscv-allyesconfig (https://download.01.org/0day-ci/archive/20231019/202310190159.mAUo9iEX-lkp@xxxxxxxxx/config)
> compiler: riscv64-linux-gcc (GCC) 13.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231019/202310190159.mAUo9iEX-
> lkp@xxxxxxxxx/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202310190159.mAUo9iEX-lkp@xxxxxxxxx/
> 
> All warnings (new ones prefixed by >>):
> 
>    In file included from arch/riscv/include/asm/page.h:12,
>                     from arch/riscv/include/asm/thread_info.h:11,
>                     from include/linux/thread_info.h:60,
>                     from include/asm-generic/preempt.h:5,
>                     from ./arch/riscv/include/generated/asm/preempt.h:1,
>                     from include/linux/preempt.h:78,
>                     from include/linux/spinlock.h:56,
>                     from include/linux/mmzone.h:8,
>                     from include/linux/gfp.h:7,
>                     from include/linux/mm.h:7,
>                     from arch/riscv/include/asm/cacheflush.h:9,
>                     from arch/riscv/kernel/hibernate.c:11:
>    arch/riscv/kernel/hibernate.c: In function 'pfn_is_nosave':
> >> arch/riscv/kernel/hibernate.c:76:65: warning: array subscript -1 is outside array bounds of 'const void[]' [-Warray-bounds=]
>       76 |         unsigned long nosave_end_pfn = sym_to_pfn(&__nosave_end - 1);
>    include/linux/pfn.h:22:43: note: in definition of macro 'PHYS_PFN'
>       22 | #define PHYS_PFN(x)     ((unsigned long)((x) >> PAGE_SHIFT))
>          |                                           ^
>    arch/riscv/include/asm/page.h:172:33: note: in expansion of macro '__phys_to_pfn'
>      172 | #define sym_to_pfn(x)           __phys_to_pfn(__pa_symbol(x))
>          |                                 ^~~~~~~~~~~~~
>    arch/riscv/include/asm/page.h:156:44: note: in expansion of macro 'RELOC_HIDE'
>      156 | #define __pa_symbol(x)  __phys_addr_symbol(RELOC_HIDE((unsigned long)(x), 0))
>          |                                            ^~~~~~~~~~
>    arch/riscv/include/asm/page.h:172:47: note: in expansion of macro '__pa_symbol'
>      172 | #define sym_to_pfn(x)           __phys_to_pfn(__pa_symbol(x))
>          |                                               ^~~~~~~~~~~
>    arch/riscv/kernel/hibernate.c:76:40: note: in expansion of macro 'sym_to_pfn'
>       76 |         unsigned long nosave_end_pfn = sym_to_pfn(&__nosave_end - 1);
>          |                                        ^~~~~~~~~~
>    In file included from arch/riscv/include/asm/sections.h:8,
>                     from include/linux/interrupt.h:21,
>                     from include/linux/kernel_stat.h:9,
>                     from include/linux/cgroup.h:26,
>                     from include/linux/memcontrol.h:13,
>                     from include/linux/swap.h:9,
>                     from include/asm-generic/tlb.h:15,
>                     from arch/riscv/include/asm/tlb.h:14,
>                     from arch/riscv/include/asm/pgalloc.h:11,
>                     from arch/riscv/kernel/hibernate.c:14:
>    include/asm-generic/sections.h:59:45: note: at offset -1 into object '__nosave_end' of size [0, 9223372036854775807]
>       59 | extern __visible const void __nosave_begin, __nosave_end;
>          |                                             ^~~~~~~~~~~~
> 
> 
> vim +76 arch/riscv/kernel/hibernate.c
> 
>     69
>     70	/*
>     71	 * Check if the given pfn is in the 'nosave' section.
>     72	 */
>     73	int pfn_is_nosave(unsigned long pfn)
>     74	{
>     75		unsigned long nosave_begin_pfn = sym_to_pfn(&__nosave_begin);
>   > 76		unsigned long nosave_end_pfn = sym_to_pfn(&__nosave_end - 1);
>     77
>     78		return ((pfn >= nosave_begin_pfn) && (pfn <= nosave_end_pfn));
>     79	}
>     80
> 
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki