On Thu, Aug 27, 2020 at 7:07 AM H.J. Lu [off-list ref] wrote:

On Thu, Aug 27, 2020 at 6:36 AM Florian Weimer [off-list ref] wrote:

quoted

* H. J. Lu:

quoted

On Thu, Aug 27, 2020 at 6:19 AM Florian Weimer [off-list ref] wrote:

quoted

* Dave Martin:

quoted

You're right that this has implications: for i386, libc probably pulls
more arguments off the stack than are really there in some situations.
This isn't a new problem though.  There are already generic prctls with
fewer than 4 args that are used on x86.

As originally posted, glibc prctl would have to know that it has to pull
an u64 argument off the argument list for ARCH_X86_CET_DISABLE.  But
then the u64 argument is a problem for arch_prctl as well.

Argument of ARCH_X86_CET_DISABLE is int and passed in register.

The commit message and the C source say otherwise, I think (not sure
about the C source, not a kernel hacker).

It should read:

arch_prctl(ARCH_X86_CET_DISABLE, unsigned long features)

Or

arch_prctl(ARCH_X86_CET_DISABLE, unsigned int features)


-- 
H.J.