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From:   Tiezhu Yang <yangtiezhu@loongson.cn>
To:     Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>
Cc:     loongarch@lists.linux.dev, linux-kernel@vger.kernel.org,
        loongson-kernel@lists.loongnix.cn
Subject: [PATCH v2 3/4] LoongArch: Use larch_insn_gen_break() for kprobes
Date:   Fri, 14 Apr 2023 17:33:00 +0800
Message-Id: <1681464781-4428-4-git-send-email-yangtiezhu@loongson.cn>
In-Reply-To: <1681464781-4428-1-git-send-email-yangtiezhu@loongson.cn>
References: <1681464781-4428-1-git-send-email-yangtiezhu@loongson.cn>
Precedence: bulk

For now, we can use larch_insn_gen_break() to define KPROBE_BP_INSN and
KPROBE_SSTEPBP_INSN. Because larch_insn_gen_break() returns instruction
word, define kprobe_opcode_t as u32, then do some small changes related
with type conversion, no functional change intended.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/include/asm/kprobes.h |  2 +-
 arch/loongarch/kernel/kprobes.c      | 33 ++++++++++++++-------------------
 2 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/arch/loongarch/include/asm/kprobes.h b/arch/loongarch/include/asm/kprobes.h
index 798020a..7ef7a0f 100644
--- a/arch/loongarch/include/asm/kprobes.h
+++ b/arch/loongarch/include/asm/kprobes.h
@@ -22,7 +22,7 @@ do {									\
 
 #define kretprobe_blacklist_size	0
 
-typedef union loongarch_instruction kprobe_opcode_t;
+typedef u32 kprobe_opcode_t;
 
 /* Architecture specific copy of original instruction */
 struct arch_specific_insn {
diff --git a/arch/loongarch/kernel/kprobes.c b/arch/loongarch/kernel/kprobes.c
index 08c78d2..1835102 100644
--- a/arch/loongarch/kernel/kprobes.c
+++ b/arch/loongarch/kernel/kprobes.c
@@ -4,19 +4,8 @@
 #include <linux/preempt.h>
 #include <asm/break.h>
 
-static const union loongarch_instruction breakpoint_insn = {
-	.reg0i15_format = {
-		.opcode = break_op,
-		.immediate = BRK_KPROBE_BP,
-	}
-};
-
-static const union loongarch_instruction singlestep_insn = {
-	.reg0i15_format = {
-		.opcode = break_op,
-		.immediate = BRK_KPROBE_SSTEPBP,
-	}
-};
+#define KPROBE_BP_INSN		larch_insn_gen_break(BRK_KPROBE_BP)
+#define KPROBE_SSTEPBP_INSN	larch_insn_gen_break(BRK_KPROBE_SSTEPBP)
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -24,7 +13,7 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 static void arch_prepare_ss_slot(struct kprobe *p)
 {
 	p->ainsn.insn[0] = *p->addr;
-	p->ainsn.insn[1] = singlestep_insn;
+	p->ainsn.insn[1] = KPROBE_SSTEPBP_INSN;
 	p->ainsn.restore = (unsigned long)p->addr + LOONGARCH_INSN_SIZE;
 }
 NOKPROBE_SYMBOL(arch_prepare_ss_slot);
@@ -37,17 +26,20 @@ NOKPROBE_SYMBOL(arch_prepare_simulate);
 
 int arch_prepare_kprobe(struct kprobe *p)
 {
+	union loongarch_instruction insn;
+
 	if ((unsigned long)p->addr & 0x3)
 		return -EILSEQ;
 
 	/* copy instruction */
 	p->opcode = *p->addr;
+	insn.word = p->opcode;
 
 	/* decode instruction */
-	if (insns_not_supported(p->opcode))
+	if (insns_not_supported(insn))
 		return -EINVAL;
 
-	if (insns_need_simulation(p->opcode)) {
+	if (insns_need_simulation(insn)) {
 		p->ainsn.insn = NULL;
 	} else {
 		p->ainsn.insn = get_insn_slot();
@@ -68,7 +60,7 @@ NOKPROBE_SYMBOL(arch_prepare_kprobe);
 /* Install breakpoint in text */
 void arch_arm_kprobe(struct kprobe *p)
 {
-	*p->addr = breakpoint_insn;
+	*p->addr = KPROBE_BP_INSN;
 	flush_insn_slot(p);
 }
 NOKPROBE_SYMBOL(arch_arm_kprobe);
@@ -163,6 +155,8 @@ NOKPROBE_SYMBOL(post_kprobe_handler);
 static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
 			     struct kprobe_ctlblk *kcb, int reenter)
 {
+	union loongarch_instruction insn;
+
 	if (reenter) {
 		save_previous_kprobe(kcb);
 		set_current_kprobe(p);
@@ -178,7 +172,8 @@ static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
 		regs->csr_era = (unsigned long)p->ainsn.insn;
 	} else {
 		/* simulate single steping */
-		arch_simulate_insn(p->opcode, regs);
+		insn.word = p->opcode;
+		arch_simulate_insn(insn, regs);
 		/* now go for post processing */
 		post_kprobe_handler(p, kcb, regs);
 	}
@@ -253,7 +248,7 @@ bool kprobe_breakpoint_handler(struct pt_regs *regs)
 		}
 	}
 
-	if (addr->word != breakpoint_insn.word) {
+	if (*addr != KPROBE_BP_INSN) {
 		/*
 		 * The breakpoint instruction was removed right
 		 * after we hit it.  Another cpu has removed
-- 
2.1.0