On Mon, Mar 14, 2022 at 08:21:30AM +0100, Christophe Leroy wrote:
> System.map shows that vmlinux contains several instances of
> __static_call_return0():
>
> c0004fc0 t __static_call_return0
> c0011518 t __static_call_return0
> c00d8160 t __static_call_return0
>
> arch_static_call_transform() uses the middle one to check whether we are
> setting a call to __static_call_return0 or not:
>
> c0011520 <arch_static_call_transform>:
> c0011520: 3d 20 c0 01 lis r9,-16383 <== r9 =
> 0xc001 << 16
> c0011524: 39 29 15 18 addi r9,r9,5400 <== r9 += 0x1518
> c0011528: 7c 05 48 00 cmpw r5,r9 <== r9 has
> value 0xc0011518 here
>
> So if static_call_update() is called with one of the other instances of
> __static_call_return0(), arch_static_call_transform() won't recognise it.
>
> In order to work properly, global single instance of __static_call_return0()
> is required.
>
> Fixes: 3f2a8fc4b15d ("static_call/x86: Add __static_call_return0()")
> Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
Acked-by: Josh Poimboeuf <jpoim...@redhat.com>
--
Josh
