Randy reported a false-positive:
arch/x86/hyperv/hv_apic.o: warning: objtool: hv_apic_write()+0x25: 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: 7117f16bf4 ("objtool: Fix ORC vs alternatives")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
ab3852ab5c