linux-kernel - [PATCH] arm64: kprobes: Restore local irqflag if kprobes is cancelled

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Message-ID: <20210412174101.6bfb0594@xhacker.debian>
Date:   Mon, 12 Apr 2021 17:41:01 +0800
From:   Jisheng Zhang <Jisheng.Zhang@...aptics.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Liao Chang <liaochang1@...wei.com>
Subject: [PATCH] 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@...aptics.com>
---
 arch/arm64/kernel/probes/kprobes.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index 66aac2881ba8..85645b2b0c7a 100644
--- 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:
-- 
2.31.0