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SubjectRe: [PATCH v3 3/5] arm64: vdso32: Fix compilation warning
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On 10/1/19 2:21 PM, Will Deacon wrote:
> On Thu, Sep 26, 2019 at 10:43:40PM +0100, Vincenzo Frascino wrote:
>> As reported by Will Deacon the following compilation warning appears
>> during the compilation of the vdso32:
>>
>> In file included from ./arch/arm64/include/asm/thread_info.h:17:0,
>> from ./include/linux/thread_info.h:38,
>> from ./arch/arm64/include/asm/preempt.h:5,
>> from ./include/linux/preempt.h:78,
>> from ./include/linux/spinlock.h:51,
>> from ./include/linux/seqlock.h:36,
>> from ./include/linux/time.h:6,
>> from .../work/linux/lib/vdso/gettimeofday.c:7,
>> from <command-line>:0:
>> ./arch/arm64/include/asm/memory.h: In function ‘__tag_set’:
>> ./arch/arm64/include/asm/memory.h:233:15: warning: cast from pointer to
>> integer of different size [-Wpointer-to-int-cast]
>> u64 __addr = (u64)addr & ~__tag_shifted(0xff);
>> ^
>> In file included from ./arch/arm64/include/asm/pgtable-hwdef.h:8:0,
>> from ./arch/arm64/include/asm/processor.h:34,
>> from ./arch/arm64/include/asm/elf.h:118,
>> from ./include/linux/elf.h:5,
>> from ./include/linux/elfnote.h:62,
>> from arch/arm64/kernel/vdso32/note.c:11:
>> ./arch/arm64/include/asm/memory.h: In function ‘__tag_set’:
>> ./arch/arm64/include/asm/memory.h:233:15: warning: cast from pointer to
>> integer of different size [-Wpointer-to-int-cast]
>> u64 __addr = (u64)addr & ~__tag_shifted(0xff);
>> ^
>>
>> This happens because few 64 bit compilation headers are included during
>> the generation of vdso32.
>>
>> Fix the issue redefining the __tag_set function.
>>
>> Note: This fix is meant to be temporary, a more comprehensive solution
>> based on the refactoring of the generic headers will be provided with a
>> future patch set. At that point it will be possible to revert this patch.
>>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> ---
>> arch/arm64/include/asm/memory.h | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
>> index b61b50bf68b1..c61b2eb50a3b 100644
>> --- a/arch/arm64/include/asm/memory.h
>> +++ b/arch/arm64/include/asm/memory.h
>> @@ -228,11 +228,14 @@ static inline unsigned long kaslr_offset(void)
>> #define __tag_get(addr) 0
>> #endif /* CONFIG_KASAN_SW_TAGS */
>>
>> +#ifdef __aarch64__
>> +/* Do not attempt to compile this code with compat vdso */
>> static inline const void *__tag_set(const void *addr, u8 tag)
>> {
>> u64 __addr = (u64)addr & ~__tag_shifted(0xff);
>> return (const void *)(__addr | __tag_shifted(tag));
>> }
>> +#endif
>
> Sorry, but I'm not taking this.
>
> I know you're trying to fix the issues I reported as quickly as you can (and
> thank you for that), but I'm sure that you agree this needs more thought to
> develop a proper solution to what is a much bigger issue than can be solved
> by sprinkling #ifdefs. I can live with the warning on the basis that a
> proper fix is in the pipeline, but in the meantime it can serve as a
> reminder that we're not done here.
>

This was my original preference as well, if we silence the warnings we tend to
forget about them. Since you reported the issue as urgent, I reacted with
something that fixes it temporarily, but I have not objections if you want to
wait for a more comprehensive solution.

> Will
>

--
Regards,
Vincenzo

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