mainline inclusion
from mainline-5.12-rc1
commit 3f2a8fc4
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I410UT
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3f2a8fc4b15de18644e8a80a09edda168676e22c

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

Provide a stub function that return 0 and wire up the static call site
patching to replace the CALL with a single 5 byte instruction that
clears %RAX, the return value register.

The function can be cast to any function pointer type that has a
single %RAX return (including pointers). Also provide a version that
returns an int for convenience. We are clearing the entire %RAX register
in any case, whether the return value is 32 or 64 bits, since %RAX is
always a scratch register anyway.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-2-frederic@kernel.orgSigned-off-by: NMa Junhai <majunhai2@huawei.com>
Reviewed-by: NChen Hui <judy.chenhui@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>