On Wed, Aug 28, 2024 at 02:26:08PM +0200, Jason A. Donenfeld wrote:

On Wed, Aug 28, 2024 at 2:24 PM Arnd Bergmann [off-list ref] wrote:

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On Wed, Aug 28, 2024, at 11:18, Jason A. Donenfeld wrote:

quoted

On Tue, Aug 27, 2024 at 05:53:30PM -0500, Segher Boessenkool wrote:

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On Tue, Aug 27, 2024 at 11:08:19AM -0700, Eric Biggers wrote:

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Is there a compiler flag that could be used to disable the generation of calls
to memset?

-fno-tree-loop-distribute-patterns .  But, as always, read up on it, see
what it actually does (and how it avoids your problem, and mostly: learn
what the actual problem *was*!)

This might help with various loops, but it doesn't help with the matter
that this patch fixes, which is struct initialization. I just tried it
with the arm64 patch to no avail.

Maybe -ffreestanding can help here? That should cause the vdso to be built
with the assumption that there is no libc, so it would neither add nor
remove standard library calls. Not sure if that causes other problems,
e.g. if the calling conventions are different.

quoted

From https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90701:

| You need -ffreestanding but that is documented to emit memset and
memcpy still.

Yeah.

'-nostdlib'
     Do not use the standard system startup files or libraries when
     linking.

This won't help a bit, the compiler will still optimise your
initialisation loop to a memset() call, it just won't link to libgcc.a
and crt*.o and its ilk (which is not where mem* are implemented in the
first place!)


Segher