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

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Message-ID: <20220923084658.99304-4-liaochang1@huawei.com>
Date:   Fri, 23 Sep 2022 16:46:58 +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>, <mhiramat@...nel.org>,
        <rostedt@...dmis.org>, <mark.rutland@....com>, <maz@...nel.org>,
        <liaochang1@...wei.com>, <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 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.

Since I and D caches are coherent within single-step slot from
aarch64_insn_patch_text_nosync(), hence no need to do it again via
flush_icache_range().

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Liao Chang <liaochang1@...wei.com>
---
 arch/arm64/kernel/probes/kprobes.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index d1d182320245..29b98bc12833 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -44,13 +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);
-
-	flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE));
+	aarch64_insn_patch_text_nosync(addr, p->opcode);
+	aarch64_insn_patch_text_nosync(addr + 1, BRK64_OPCODE_KPROBES_SS);
 
 	/*
 	 * Needs restoring of return address after stepping xol.
-- 
2.17.1