From 0ecf6a9e47d825b7dddfebca738386b809e59a94 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 3 Feb 2021 00:02:06 +1100 Subject: [PATCH] powerpc/64: Make stack tracing work during very early boot If we try to stack trace very early during boot, either due to a WARN/BUG or manual dump_stack(), we will oops in valid_emergency_stack() when we try to dereference the paca_ptrs array. The fix is simple, we just return false if paca_ptrs isn't allocated yet. The stack pointer definitely isn't part of any emergency stack because we haven't allocated any yet. Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210202130207.1303975-1-mpe@ellerman.id.au --- arch/powerpc/kernel/process.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 8520ed5ae144..e296440e9d16 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -2047,6 +2047,9 @@ static inline int valid_emergency_stack(unsigned long sp, struct task_struct *p, unsigned long stack_page; unsigned long cpu = task_cpu(p); + if (!paca_ptrs) + return 0; + stack_page = (unsigned long)paca_ptrs[cpu]->emergency_sp - THREAD_SIZE; if (sp >= stack_page && sp <= stack_page + THREAD_SIZE - nbytes) return 1;