[PATCH AUTOSEL 5.10 25/85] powerpc/32: Statically initialise first emergency context

From: Sasha Levin
Date: Wed May 05 2021 - 13:01:40 EST


From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>

[ Upstream commit a4719f5bb6d7dc220bffdc1b9f5ce5eaa5543581 ]

The check of the emergency context initialisation in
vmap_stack_overflow is buggy for the SMP case, as it
compares r1 with 0 while in the SMP case r1 is offseted
by the CPU id.

Instead of fixing it, just perform static initialisation
of the first emergency context.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/4a67ba422be75713286dca0c86ee0d3df2eb6dfa.1615552867.git.christophe.leroy@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/powerpc/kernel/head_32.h | 6 +-----
arch/powerpc/kernel/setup_32.c | 2 +-
2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h
index fef0b34a77c9..f8e3d15ddf69 100644
--- a/arch/powerpc/kernel/head_32.h
+++ b/arch/powerpc/kernel/head_32.h
@@ -338,11 +338,7 @@
lis r1, emergency_ctx@ha
#endif
lwz r1, emergency_ctx@l(r1)
- cmpwi cr1, r1, 0
- bne cr1, 1f
- lis r1, init_thread_union@ha
- addi r1, r1, init_thread_union@l
-1: addi r1, r1, THREAD_SIZE - INT_FRAME_SIZE
+ addi r1, r1, THREAD_SIZE - INT_FRAME_SIZE
EXCEPTION_PROLOG_2
SAVE_NVGPRS(r11)
addi r3, r1, STACK_FRAME_OVERHEAD
diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
index 057d6b8e9bb0..e7f2eb7837fc 100644
--- a/arch/powerpc/kernel/setup_32.c
+++ b/arch/powerpc/kernel/setup_32.c
@@ -164,7 +164,7 @@ void __init irqstack_early_init(void)
}

#ifdef CONFIG_VMAP_STACK
-void *emergency_ctx[NR_CPUS] __ro_after_init;
+void *emergency_ctx[NR_CPUS] __ro_after_init = {[0] = &init_stack};

void __init emergency_stack_init(void)
{
--
2.30.2