Messages in this thread | | | Date | Fri, 8 May 2020 11:01:22 -0500 | From | Josh Poimboeuf <> | Subject | Re: mmotm 2020-05-05-15-28 uploaded (objtool warning) |
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On Fri, May 08, 2020 at 12:38:30PM +0200, Peter Zijlstra wrote: > Subject: objtool: Allow no-op CFI ops in alternatives > From: Peter Zijlstra <peterz@infradead.org> > Date: Fri May 8 12:34:33 CEST 2020 > > Randy reported a false-positive: "alternative modifies stack". > > What happens is that: > > alternative_io("movl %0, %P1", "xchgl %0, %P1", X86_BUG_11AP, > 13d: 89 9d 00 d0 7f ff mov %ebx,-0x803000(%rbp) > > decodes to an instruction with CFI-ops because it modifies RBP. > However, due to this being a !frame-pointer build, that should not in > fact change the CFI state. > > So instead of dis-allowing any CFI-op, verify the op would've actually > changed the CFI state. > > Fixes: 7117f16bf460 ("objtool: Fix ORC vs alternatives") > Reported-by: Randy Dunlap <rdunlap@infradead.org> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
It helps to put an example of the fixed warning in the commit log, like:
This fixes the following warning:
arch/x86/hyperv/hv_apic.o: warning: objtool: hv_apic_write()+0x25: alternative modifies stack
Otherwise it looks good.
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
-- Josh
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