x86/entry: Use PUSH_AND_CLEAR_REGS for compat

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2090231



commit 8c42819b
Author: Peter Zijlstra <peterz@infradead.org>
Date:   Fri, 6 May 2022 14:14:34 +0200

    x86/entry: Use PUSH_AND_CLEAR_REGS for compat

    Since the upper regs don't exist for ia32 code, preserving them
    doesn't hurt and it simplifies the code.

    This doesn't add any attack surface that would not already be
    available through INT80.

    Notably:

     - 32bit SYSENTER: didn't clear si, dx, cx.

     - 32bit SYSCALL, INT80: *do* clear si since the C functions don't
       take a second argument.

     - 64bit: didn't clear si since the C functions take a second
       argument; except the error_entry path might have only one argument,
       so clearing si was missing here.

    32b SYSENTER should be clearing all those 3 registers, nothing uses them
    and selftests pass.

    Unconditionally clear rsi since it simplifies code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
    Link: https://lore.kernel.org/r/20220506121631.293889636@infradead.org



Signed-off-by: Waiman Long <longman@redhat.com>