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    SubjectRe: [PATCH 3/6] x86/entry: Use PUSH_AND_CLEAR_REGS for compat
    On Fri, May 6, 2022 at 8:20 PM Peter Zijlstra <peterz@infradead.org> wrote:
    >
    > 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>
    > Reviewed-by: Borislav Petkov <bp@suse.de>


    Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>

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