On Mon, Apr 11, 2022 at 06:54:43PM +0200, Christophe Leroy wrote:
This is backport to 5.15,5.16,5.17
(cherry picked from commit 8fd4ddda2f49a66bf5dd3d0c01966c4b1971308b)
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 Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Josh Poimboeuf jpoimboe@redhat.com Link: https://lkml.kernel.org/r/30821468a0e7d28251954b578e5051dc09300d04.164725849...
include/linux/static_call.h | 5 +- kernel/Makefile | 3 +- kernel/static_call.c | 542 +----------------- .../{static_call.c => static_call_inline.c} | 5 - 4 files changed, 4 insertions(+), 551 deletions(-) copy kernel/{static_call.c => static_call_inline.c} (99%)
Thanks for this, now queued up!
greg k-h