On 8/27/2020 7:08 AM, H.J. Lu wrote:
On Thu, Aug 27, 2020 at 7:07 AM H.J. Lu <hjl.tools@xxxxxxxxx> wrote:
On Thu, Aug 27, 2020 at 6:36 AM Florian Weimer <fweimer@xxxxxxxxxx> wrote:
* H. J. Lu:
On Thu, Aug 27, 2020 at 6:19 AM Florian Weimer <fweimer@xxxxxxxxxx> wrote:
* Dave Martin:
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)
Like other arch_prctl()'s, this parameter was 'unsigned long' earlier.
The idea was, since this arch_prctl is only implemented for the 64-bit
kernel, we wanted it to look as 64-bit only. I will change it back to
'unsigned long'.
Yu-cheng
