Re: [PATCH v2] random: vDSO: Avoid call to memset() when zeroing reserved in __cvdso_getrandom_data()

[sashiko-bot@kernel.org]

> After a recent change in LLVM [1], builds with the random vDSO
> implementation, such as PowerPC and RISC-V, fail when checking the vDSO:
> 
>   arch/powerpc/kernel/vdso/vdso32.so.dbg: dynamic relocations are not supported
>   arch/riscv/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported
> 
> memset() is now generated when zeroing params->reserved for some builds
> because LLVM has an optimization (now run in more instances) that can
> recognize at compile time when it is assigning a static value to a
> contiguous area of memory and turn that into a call to memset(). Both
> clang and GCC assume memset() is always available [2].
> 
> clang provides a builtin, __builtin_memset_inline [3][4], that can be
> used to ensure an external function call is not generated when zeroing
> this memory. Use it when it is available.
> [ ... ]
> Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=1ff6d9f7428b0668cd8ab0b3e3ab94f1d733124d [5]
> Link: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-finline-stringops [6]
> Suggested-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260925-vdso-getrandom-avoid-memset-llvm-24-v2-1-ce640f872393@kernel.org?part=1