Messages in this thread | | | Date | Tue, 15 Mar 2022 14:11:58 -0700 | From | Josh Poimboeuf <> | Subject | Re: [PATCH] static_call: Don't make __static_call_return0 static |
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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.leroy@csgroup.eu>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
-- Josh
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