Messages in this thread Patch in this message | | | Date | Mon, 15 Jun 2020 17:20:56 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH -tip v3 1/2] kcov: Make runtime functions noinstr-compatible |
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On Mon, Jun 15, 2020 at 05:03:27PM +0200, Peter Zijlstra wrote:
> Yes, I think so. x86_64 needs lib/memcpy_64.S in .noinstr.text then. For > i386 it's an __always_inline inline-asm thing.
Bah, I tried writing it without memcpy, but clang inserts memcpy anyway :/
--- diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index af75109485c26..d74fd6313a4ed 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -686,17 +686,17 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s) * just below the IRET frame) and we want to pretend that the * exception came from the IRET target. */ - struct bad_iret_stack tmp, *new_stack = + struct bad_iret_stack tmp = *s, *new_stack = (struct bad_iret_stack *)__this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1; + unsigned long *p = (unsigned long *)s->regs.sp; - /* Copy the IRET target to the temporary storage. */ - memcpy(&tmp.regs.ip, (void *)s->regs.sp, 5*8); + tmp.regs.ip = p[0]; + tmp.regs.cs = p[1]; + tmp.regs.flags = p[2]; + tmp.regs.sp = p[3]; + tmp.regs.ss = p[4]; - /* Copy the remainder of the stack from the current stack. */ - memcpy(&tmp, s, offsetof(struct bad_iret_stack, regs.ip)); - - /* Update the entry stack */ - memcpy(new_stack, &tmp, sizeof(tmp)); + *new_stack = tmp; BUG_ON(!user_mode(&new_stack->regs)); return new_stack;
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