virt_to_phys outside array bounds warning (GCC 12.1.0)

virt_to_phys outside array bounds warning (GCC 12.1.0)

[Bagas Sanjaya]

Hi everyone,

When cross-compiling arm 5.19-rc1 kernel using GCC 12.1.0 (armv7 with neon
fpu, multi_v7_defconfig), I got outside array bounds warning pointing to
virt_to_phys() macro:

  DTC     arch/arm/boot/dts/am335x-evm.dtb
In file included from ./arch/arm/include/asm/page.h:163,
                 from ./arch/arm/include/asm/thread_info.h:14,
                 from ./include/linux/thread_info.h:60,
                 from ./include/asm-generic/preempt.h:5,
                 from ./arch/arm/include/generated/asm/preempt.h:1,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:55,
                 from ./include/linux/wait.h:9,
                 from ./include/linux/wait_bit.h:8,
                 from ./include/linux/fs.h:6,
                 from ./include/linux/proc_fs.h:10,
                 from ./include/linux/efi.h:19,
                 from arch/arm/kernel/setup.c:7:
In function 'request_standard_resources',
    inlined from 'setup_arch' at arch/arm/kernel/setup.c:1158:2:
./arch/arm/include/asm/memory.h:311:22: warning: array subscript -1 is outside array bounds of 'char[2147483647]' [-Warray-bounds]
  311 | #define virt_to_phys virt_to_phys
arch/arm/kernel/setup.c:855:31: note: in expansion of macro 'virt_to_phys'
  855 |         kernel_code.end     = virt_to_phys(__init_begin - 1);
      |                               ^~~~~~~~~~~~
In file included from ./include/linux/pid_namespace.h:7,
                 from ./include/linux/ptrace.h:10,
                 from ./include/linux/elfcore.h:11,
                 from ./include/linux/crash_core.h:6,
                 from ./include/linux/kexec.h:18,
                 from arch/arm/kernel/setup.c:20:
./include/linux/mm.h: In function 'setup_arch':
./include/linux/mm.h:2500:21: note: at offset -1 into object '__init_begin' of size [0, 2147483647]
 2500 |         extern char __init_begin[], __init_end[];
      |                     ^~~~~~~~~~~~
In function 'request_standard_resources',
    inlined from 'setup_arch' at arch/arm/kernel/setup.c:1158:2:
./arch/arm/include/asm/memory.h:311:22: warning: array subscript -1 is outside array bounds of 'char[2147483647]' [-Warray-bounds]
  311 | #define virt_to_phys virt_to_phys
arch/arm/kernel/setup.c:857:31: note: in expansion of macro 'virt_to_phys'
  857 |         kernel_data.end     = virt_to_phys(_end - 1);
      |                               ^~~~~~~~~~~~
In file included from ./arch/arm/include/asm/sections.h:5,
                 from ./include/linux/interrupt.h:21,
                 from ./include/linux/rtc.h:17,
                 from ./include/linux/efi.h:20:
./include/asm-generic/sections.h: In function 'setup_arch':
./include/asm-generic/sections.h:41:13: note: at offset -1 into object '_end' of size [0, 2147483647]
   41 | extern char _end[];
      |             ^~~~

Thanks.

Reported-by: Bagas Sanjaya <bagasdotme@gmail.com>

-- 
An old man doll... just what I always wanted! - Clara

Re: virt_to_phys outside array bounds warning (GCC 12.1.0)

[Krzysztof Kozlowski]

On 08/06/2022 10:39, Bagas Sanjaya wrote:
> Hi everyone,
> 
> When cross-compiling arm 5.19-rc1 kernel using GCC 12.1.0 (armv7 with neon
> fpu, multi_v7_defconfig), I got outside array bounds warning pointing to
> virt_to_phys() macro:
> 

Thanks for the report!

I think this was already reported:
https://lore.kernel.org/all/CAK8P3a3X0UwQiVNZqvGmSKi8BX6zg=k07+9Q3rDGqHVkc8Hdsg@mail.gmail.com/

Anyway, for the future:
I don't think the CC list matches the problem. Please bisect this issue
(since it is reproducible build time, it should be straightforward) to
find offending commit and then Cc responsible people and maintainers
(scripts/get_maintainer.pl). Ccing half-random people might not get
necessary attention.

Best regards,
Krzysztof

Re: virt_to_phys outside array bounds warning (GCC 12.1.0)

[Bagas Sanjaya]

On 6/8/22 16:28, Krzysztof Kozlowski wrote:
> On 08/06/2022 10:39, Bagas Sanjaya wrote:
>> Hi everyone,
>>
>> When cross-compiling arm 5.19-rc1 kernel using GCC 12.1.0 (armv7 with neon
>> fpu, multi_v7_defconfig), I got outside array bounds warning pointing to
>> virt_to_phys() macro:
>>
> 
> Thanks for the report!
> 
> I think this was already reported:
> https://lore.kernel.org/all/CAK8P3a3X0UwQiVNZqvGmSKi8BX6zg=k07+9Q3rDGqHVkc8Hdsg@mail.gmail.com/
> 

The report above is for arm64, but similar to this report (arm report).

> Anyway, for the future:
> I don't think the CC list matches the problem. Please bisect this issue
> (since it is reproducible build time, it should be straightforward) to
> find offending commit and then Cc responsible people and maintainers
> (scripts/get_maintainer.pl). Ccing half-random people might not get
> necessary attention.
> 

I think the most likely culprit is commit 37efe6427dd50e ("[ARM] use asm/sections.h")
and 14c4a533e0996f ("ARM: 8583/1: mm: fix location of _etext").


Thanks.

-- 
An old man doll... just what I always wanted! - Clara