linux-kernel - [PATCH V2 3/3] arm64/kprobe: Optimize the performance of patching single-step slot

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Message-ID: <20220913033454.104519-4-liaochang1@huawei.com>
Date:   Tue, 13 Sep 2022 11:34:54 +0800
From:   Liao Chang <liaochang1@...wei.com>
To:     <catalin.marinas@....com>, <will@...nel.org>, <guoren@...nel.org>,
        <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <rostedt@...dmis.org>,
        <mhiramat@...nel.org>, <liaochang1@...wei.com>, <maz@...nel.org>,
        <alexandru.elisei@....com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-csky@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>
Subject: [PATCH V2 3/3] arm64/kprobe: Optimize the performance of patching single-step slot

Single-step slot would not be used until kprobe is enabled, that means
no race condition occurs on it under SMP, hence it is safe to pacth ss
slot without stopping machine.

Signed-off-by: Liao Chang <liaochang1@...wei.com>
---
 arch/arm64/kernel/probes/kprobes.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index d1d182320245..5902e33fd3b6 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -44,11 +44,10 @@ post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);
 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
 {
 	kprobe_opcode_t *addr = p->ainsn.api.insn;
-	void *addrs[] = {addr, addr + 1};
-	u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS};
 
 	/* prepare insn slot */
-	aarch64_insn_patch_text(addrs, insns, 2);
+	aarch64_insn_write(addr, p->opcode);
+	aarch64_insn_write(addr + 1, BRK64_OPCODE_KPROBES_SS);
 
 	flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE));
 
-- 
2.17.1