[PATCH v3 3/6] LoongArch: Use larch_insn_gen_break() for kprobes

From: Tiezhu Yang
Date: Wed Apr 19 2023 - 05:57:39 EST


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@xxxxxxxxxxx>
---
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