selftests/rseq: x86-32: use %gs segment selector for accessing rseq thread area

stable inclusion
from stable-v5.10.129
commit 7e617278bf3afd4ed81c04a75e4a32ce8fb5bf44
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YNDQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7e617278bf3afd4ed81c04a75e4a32ce8fb5bf44



--------------------------------

commit 127b6429 upstream.

Rather than use rseq_get_abi() and pass its result through a register to
the inline assembler, directly access the per-thread rseq area through a
memory reference combining the %gs segment selector, the constant offset
of the field in struct rseq, and the rseq_offset value (in a register).

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220124171253.22072-16-mathieu.desnoyers@efficios.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>