From: Michael Ellerman Date: Tue, 2 Feb 2021 13:02:06 +0000 (+1100) Subject: powerpc/64: Make stack tracing work during very early boot X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0ecf6a9e47d825b7dddfebca738386b809e59a94;p=linux.git 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 --- diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 8520ed5ae144d..e296440e9d16a 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;