x86: um: vdso: Add '%rcx' and '%r11' to the syscall clobber list

stable inclusion
from stable-v5.10.173
commit 7cb46fa16b96ff197eb84a33b23a8448fe0c1e8d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7X0QU

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7cb46fa16b96ff197eb84a33b23a8448fe0c1e8d



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[ Upstream commit 5541992e ]

The 'syscall' instruction clobbers '%rcx' and '%r11', but they are not
listed in the inline Assembly that performs the syscall instruction.

No real bug is found. It wasn't buggy by luck because '%rcx' and '%r11'
are caller-saved registers, and not used in the functions, and the
functions are never inlined.

Add them to the clobber list for code correctness.

Fixes: f1c2bb8b ("um: implement a x86_64 vDSO")
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>