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@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Link: https://lkml.kernel.org/r/30821468a0e7d28251954b578e5051dc09300d04.1647258493.git.christophe.leroy@xxxxxxxxxx
> ---
> 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
