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    Subject[patch V4 part 3 01/29] x86/traps: Mark fixup_bad_iret() noinstr
    This is called from deep entry ASM in a situation where instrumentation
    will cause more harm than providing useful information.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    arch/x86/kernel/traps.c | 16 +++++++++-------
    1 file changed, 9 insertions(+), 7 deletions(-)

    --- a/arch/x86/kernel/traps.c
    +++ b/arch/x86/kernel/traps.c
    @@ -621,7 +621,7 @@ struct bad_iret_stack {
    struct pt_regs regs;
    };

    -asmlinkage __visible notrace
    +asmlinkage __visible noinstr
    struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
    {
    /*
    @@ -632,19 +632,21 @@ struct bad_iret_stack *fixup_bad_iret(st
    * just below the IRET frame) and we want to pretend that the
    * exception came from the IRET target.
    */
    - struct bad_iret_stack *new_stack =
    - (struct bad_iret_stack *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
    + struct bad_iret_stack tmp, *new_stack =
    + (struct bad_iret_stack *)__this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;

    - /* Copy the IRET target to the new stack. */
    - memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
    + /* Copy the IRET target to the temporary storage. */
    + memcpy(&tmp.regs.ip, (void *)s->regs.sp, 5*8);

    /* Copy the remainder of the stack from the current stack. */
    - memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
    + memcpy(&tmp, s, offsetof(struct bad_iret_stack, regs.ip));
    +
    + /* Update the entry stack */
    + memcpy(new_stack, &tmp, sizeof(tmp));

    BUG_ON(!user_mode(&new_stack->regs));
    return new_stack;
    }
    -NOKPROBE_SYMBOL(fixup_bad_iret);
    #endif

    static bool is_sysenter_singlestep(struct pt_regs *regs)
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