arm64: kprobes: Restore local irqflag if kprobes is cancelled

If instruction being single stepped caused a page fault, the kprobes
is cancelled to let the page fault handler continue as a normal page
fault. But the local irqflags are disabled so cpu will restore pstate
with DAIF masked. After pagefault is serviced, the kprobes is
triggerred again, we overwrite the saved_irqflag by calling
kprobes_save_local_irqflag(). NOTE, DAIF is masked in this new saved
irqflag. After kprobes is serviced, the cpu pstate is retored with
DAIF masked.

This patch is inspired by one patch for riscv from Liao Chang.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20210412174101.6bfb0594@xhacker.debian
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index 66aac2881ba84ea06b2318b45f42919982c31c98..85645b2b0c7ab5ff4161039037c5d787d5db8b5e 100644 (file)
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -267,10 +267,12 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
                if (!instruction_pointer(regs))
                        BUG();
 
-               if (kcb->kprobe_status == KPROBE_REENTER)
+               if (kcb->kprobe_status == KPROBE_REENTER) {
                        restore_previous_kprobe(kcb);
-               else
+               } else {
+                       kprobes_restore_local_irqflag(kcb, regs);
                        reset_current_kprobe();
+               }
 
                break;
        case KPROBE_HIT_ACTIVE: