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

On Thu, Oct 01, 2026 at 12:48:10PM +0200, Jason A. Donenfeld wrote:

On Thu, Oct 01, 2026 at 12:20:59PM +0200, Nathan Chancellor wrote:

quoted

control. The change that introduced -max-store-memset only did it to
"allow fine-tuning of the inlining threshold for performance analysis
and optimization". If they decide to remove it for whatever reason,
we're back to square one.

I suppose all the more reason to get -finline-stringops=memset added to
clang. Then the dual-default thing you came up with below will naturally
start choosing the first option when it becomes available.

Fair point, I can file an issue with LLVM upstream.

quoted

I know something like below would be uglier due to the ifdef but it
would avoid changing anything for GCC while clearing up the issue at
hand for clang in a guaranteed stable and succinct manner.

But then we're back to the byte-by-byte codegen that Christophe pointed
out.

I thought that was only because the fallback memset_inline() from v2 was
doing a byte-by-byte initialization? With my suggested diff, nothing
should change for GCC, as it does not have __builtin_memset_inline(), so
the "Before the patch" code generation that Christophe showed should
still be present.

quoted

If that is not acceptable, something like the following does appear to
work for me.

Okay, great, let's do that.

Does this commit seem okay with you? I used the diff you sent below and
adjusted the commit message: https://git.zx2c4.com/linux-rng/commit/?id=56ff95ee85715047eb5b5220243778af657778c8

Yeah, that seems fine to me, thanks for taking care of it!

-- 
Cheers,
Nathan