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Re: V2 [PATCH] x86/CET: Add a setcontext test for CET
- From: Carlos O'Donell <carlos at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Wed, 25 Jul 2018 11:34:28 -0400
- Subject: Re: V2 [PATCH] x86/CET: Add a setcontext test for CET
- References: <CAMe9rOrCwy5vpQNHMXCkDU2Y7CMdnLim1rvLhvOwOQnCqABemail@example.com>
On 07/25/2018 11:01 AM, H.J. Lu wrote:
> On Wed, Jul 25, 2018 at 6:29 AM, Carlos O'Donell <firstname.lastname@example.org> wrote:
>> On 07/25/2018 08:22 AM, H.J. Lu wrote:
>>> Verify that setcontext works with gaps above and below the newly
>>> allocated shadow stack.
>>> OK for master?
>>> * sysdeps/x86/Makefile (tests): Add tst-cet-setcontext-1 if
>>> CET is enabled.
>>> (CFLAGS-tst-cet-setcontext-1.c): Add -mshstk.
>>> * sysdeps/x86/tst-cet-setcontext-1.c: New file.
>> OK for 2.28 only if you add a paragraph about exactly how the shadow
>> stacks are being laid out by the calls and why unmapping ctx3 and ctx4 works
>> to leave ctx1 with gap above and below.
> Here is the updated patch with a comment:
> /* NB: When shadow stack is enabled, makecontext calls arch_prctl
> with ARCH_CET_ALLOC_SHSTK to allocate a new shadow stack which
> can be unmapped. The base address and size of the new shadow
> stack are returned in __ssp and __ssp. makecontext is
> called for CTX1, CTX3 and CTX4. But only CTX1 is used. New
> shadow stacks are allocated in the order of CTX3, CTX1, CTX4.
> It is very likely that CTX1's shadow stack is placed between
> CTX3 and CTX4. We munmap CTX3's and CTX4's shadow stacks to
> create gaps above and below CTX1's shadow stack. We check that
> setcontext CTX1 works correctly in this case. */
> It is also moved to sysdeps/unix/sysv/linux/x86/tst-cet-setcontext-1.c since
> it is Linux/x86 specific.
> OK for master?
OK for 2.28.
Thanks for the update.