On Thu, Nov 19, 2020 at 11:02:35AM -0800, Chang S. Bae wrote:

Historically, signal.h defines MINSIGSTKSZ (2KB) and SIGSTKSZ (8KB), for
use by all architectures with sigaltstack(2). Over time, the hardware state
size grew, but these constants did not evolve. Today, literal use of these
constants on several architectures may result in signal stack overflow, and
thus user data corruption.

A few years ago, the ARM team addressed this issue by establishing
getauxval(AT_MINSIGSTKSZ), such that the kernel can supply at runtime value
that is an appropriate replacement on the current and future hardware.

Add getauxval(AT_MINSIGSTKSZ) support to x86, analogous to the support
added for ARM in commit 94b07c1f8c39 ("arm64: signal: Report signal frame
size to userspace via auxv").

I don't see it documented here:

https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/man3/getauxval.3

Dunno, now that two architectures will have it, maybe that is good
enough reason to document it.

Adding Michael.

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    Boris.

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