[RFC PATCH 2/3] LoongArch: Add larch_insn_gen_break() to generate break insn

[Tiezhu Yang]

There exist various break insns such as BRK_KPROBE_BP, BRK_KPROBE_SSTEPBP,
BRK_UPROBE_BP and BRK_UPROBE_XOLBP, add larch_insn_gen_break() to generate
break insns simpler and easier.

This is preparation for later patch, no functionality change.

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
 arch/loongarch/include/asm/inst.h    | 30 +++++++++++++++++++++++++++---
 arch/loongarch/include/asm/kprobes.h |  2 +-
 arch/loongarch/kernel/inst.c         |  9 +++++++++
 arch/loongarch/kernel/kprobes.c      | 17 +++--------------
 4 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
index af494b5..a0fce06 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -409,8 +409,12 @@ static inline bool is_self_loop_ins(union loongarch_instruction *ip, struct pt_r
 void simu_pc(struct pt_regs *regs, union loongarch_instruction insn);
 void simu_branch(struct pt_regs *regs, union loongarch_instruction insn);
 
-static inline bool insns_not_supported(union loongarch_instruction insn)
+static inline bool insns_not_supported(u32 code)
 {
+	union loongarch_instruction insn;
+
+	insn.word = code;
+
 	switch (insn.reg2i14_format.opcode) {
 	case llw_op:
 	case lld_op:
@@ -429,8 +433,12 @@ static inline bool insns_not_supported(union loongarch_instruction insn)
 	return false;
 }
 
-static inline bool insns_need_simulation(union loongarch_instruction insn)
+static inline bool insns_need_simulation(u32 code)
 {
+	union loongarch_instruction insn;
+
+	insn.word = code;
+
 	if (is_pc_ins(&insn))
 		return true;
 
@@ -440,8 +448,12 @@ static inline bool insns_need_simulation(union loongarch_instruction insn)
 	return false;
 }
 
-static inline void arch_simulate_insn(union loongarch_instruction insn, struct pt_regs *regs)
+static inline void arch_simulate_insn(u32 code, struct pt_regs *regs)
 {
+	union loongarch_instruction insn;
+
+	insn.word = code;
+
 	if (is_pc_ins(&insn))
 		simu_pc(regs, insn);
 	else if (is_branch_ins(&insn))
@@ -456,6 +468,8 @@ u32 larch_insn_gen_nop(void);
 u32 larch_insn_gen_b(unsigned long pc, unsigned long dest);
 u32 larch_insn_gen_bl(unsigned long pc, unsigned long dest);
 
+u32 larch_insn_gen_break(int imm);
+
 u32 larch_insn_gen_or(enum loongarch_gpr rd, enum loongarch_gpr rj, enum loongarch_gpr rk);
 u32 larch_insn_gen_move(enum loongarch_gpr rd, enum loongarch_gpr rj);
 
@@ -474,6 +488,16 @@ static inline bool unsigned_imm_check(unsigned long val, unsigned int bit)
 	return val < (1UL << bit);
 }
 
+#define DEF_EMIT_REG0I15_FORMAT(NAME, OP)				\
+static inline void emit_##NAME(union loongarch_instruction *insn,	\
+			       int imm)					\
+{									\
+	insn->reg0i15_format.opcode = OP;				\
+	insn->reg0i15_format.immediate = imm;				\
+}
+
+DEF_EMIT_REG0I15_FORMAT(break, break_op)
+
 #define DEF_EMIT_REG0I26_FORMAT(NAME, OP)				\
 static inline void emit_##NAME(union loongarch_instruction *insn,	\
 			       int offset)				\
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/inst.c b/arch/loongarch/kernel/inst.c
index 258ef26..31b8efe 100644
--- a/arch/loongarch/kernel/inst.c
+++ b/arch/loongarch/kernel/inst.c
@@ -208,6 +208,15 @@ u32 larch_insn_gen_bl(unsigned long pc, unsigned long dest)
 	return insn.word;
 }
 
+u32 larch_insn_gen_break(int imm)
+{
+	union loongarch_instruction insn;
+
+	emit_break(&insn, imm);
+
+	return insn.word;
+}
+
 u32 larch_insn_gen_or(enum loongarch_gpr rd, enum loongarch_gpr rj, enum loongarch_gpr rk)
 {
 	union loongarch_instruction insn;
diff --git a/arch/loongarch/kernel/kprobes.c b/arch/loongarch/kernel/kprobes.c
index 08c78d2..a5c3712 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 breakpoint_insn larch_insn_gen_break(BRK_KPROBE_BP)
+#define singlestep_insn larch_insn_gen_break(BRK_KPROBE_SSTEPBP)
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -253,7 +242,7 @@ bool kprobe_breakpoint_handler(struct pt_regs *regs)
 		}
 	}
 
-	if (addr->word != breakpoint_insn.word) {
+	if (*addr != breakpoint_insn) {
 		/*
 		 * The breakpoint instruction was removed right
 		 * after we hit it.  Another cpu has removed
-- 
2.1.0