[PATCH v5 0/4] Add kprobe and kretprobe support for LoongArch

[PATCH v5 0/4] Add kprobe and kretprobe support for LoongArch

[Tiezhu Yang]

v5:
  -- Rebase on the latest code
  -- Use stop_machine_cpuslocked() to modify insn to avoid CPU race

v4:
  -- Remove kprobe_exceptions_notify() in kprobes.c
  -- Call kprobe_breakpoint_handler() and kprobe_singlestep_handler()
     in do_bp()

v3:
  -- Rebase on the latest code
  -- Check the alignment of PC in simu_branch() and simu_pc()
  -- Add ibar in flush_insn_slot()
  -- Rename kprobe_{pre,post}_handler() to {post_}kprobe_handler
  -- Add preempt_disable() and preempt_enable_no_resched()
  -- Remove r0 save/restore and do some minor changes
     in kprobes_trampoline.S
  -- Do not enable CONFIG_KPROBES by default

v2:
  -- Split simu_branch() and simu_pc() into a single patch
  -- Call kprobe_page_fault() in do_page_fault()
  -- Add kprobes_trampoline.S for kretprobe


Tiezhu Yang (4):
  LoongArch: Simulate branch and PC instructions
  LoongArch: Add kprobe support
  LoongArch: Add kretprobe support
  samples/kprobes: Add LoongArch support

 arch/loongarch/Kconfig                     |   2 +
 arch/loongarch/include/asm/inst.h          |  22 ++
 arch/loongarch/include/asm/kprobes.h       |  65 ++++++
 arch/loongarch/include/asm/ptrace.h        |   1 +
 arch/loongarch/kernel/Makefile             |   2 +
 arch/loongarch/kernel/inst.c               | 123 ++++++++++
 arch/loongarch/kernel/kprobes.c            | 350 +++++++++++++++++++++++++++++
 arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
 arch/loongarch/kernel/traps.c              |   6 +-
 arch/loongarch/mm/fault.c                  |   4 +
 samples/kprobes/kprobe_example.c           |   8 +
 11 files changed, 675 insertions(+), 4 deletions(-)
 create mode 100644 arch/loongarch/include/asm/kprobes.h
 create mode 100644 arch/loongarch/kernel/kprobes.c
 create mode 100644 arch/loongarch/kernel/kprobes_trampoline.S

-- 
2.1.0

[PATCH v5 1/4] LoongArch: Simulate branch and PC instructions

[Tiezhu Yang]

According to LoongArch Reference Manual, simulate branch and
PC instructions, this is preparation for later patch.

Link: https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#branch-instructions
Link: https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#_pcaddi_pcaddu121_pcaddu18l_pcalau12i

Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/include/asm/inst.h   |  12 ++++
 arch/loongarch/include/asm/ptrace.h |   1 +
 arch/loongarch/kernel/inst.c        | 123 ++++++++++++++++++++++++++++++++++++
 3 files changed, 136 insertions(+)

diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
index 6cd994d..a91798b 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -7,6 +7,7 @@
 
 #include <linux/types.h>
 #include <asm/asm.h>
+#include <asm/ptrace.h>
 
 #define INSN_NOP		0x03400000
 #define INSN_BREAK		0x002a0000
@@ -32,6 +33,7 @@ enum reg1i20_op {
 	lu12iw_op	= 0x0a,
 	lu32id_op	= 0x0b,
 	pcaddi_op	= 0x0c,
+	pcalau12i_op	= 0x0d,
 	pcaddu12i_op	= 0x0e,
 	pcaddu18i_op	= 0x0f,
 };
@@ -366,6 +368,16 @@ u32 larch_insn_gen_lu12iw(enum loongarch_gpr rd, int imm);
 u32 larch_insn_gen_lu32id(enum loongarch_gpr rd, int imm);
 u32 larch_insn_gen_lu52id(enum loongarch_gpr rd, enum loongarch_gpr rj, int imm);
 u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, unsigned long pc, unsigned long dest);
+void simu_branch(struct pt_regs *regs, union loongarch_instruction insn);
+void simu_pc(struct pt_regs *regs, union loongarch_instruction insn);
+
+static inline unsigned long sign_extended(unsigned long val, unsigned int idx)
+{
+	if (val & (1UL << idx))
+		return ~((1UL << (idx + 1)) - 1) | val;
+	else
+		return ((1UL << (idx + 1)) - 1) & val;
+}
 
 static inline bool signed_imm_check(long val, unsigned int bit)
 {
diff --git a/arch/loongarch/include/asm/ptrace.h b/arch/loongarch/include/asm/ptrace.h
index 59c4608..58596c4 100644
--- a/arch/loongarch/include/asm/ptrace.h
+++ b/arch/loongarch/include/asm/ptrace.h
@@ -6,6 +6,7 @@
 #define _ASM_PTRACE_H
 
 #include <asm/page.h>
+#include <asm/irqflags.h>
 #include <asm/thread_info.h>
 #include <uapi/asm/ptrace.h>
 
diff --git a/arch/loongarch/kernel/inst.c b/arch/loongarch/kernel/inst.c
index 512579d..aaaf9de 100644
--- a/arch/loongarch/kernel/inst.c
+++ b/arch/loongarch/kernel/inst.c
@@ -165,3 +165,126 @@ u32 larch_insn_gen_jirl(enum loongarch_gpr rd, enum loongarch_gpr rj, unsigned l
 
 	return insn.word;
 }
+
+void simu_branch(struct pt_regs *regs, union loongarch_instruction insn)
+{
+	unsigned int imm, imm_l, imm_h, rd, rj;
+	unsigned long pc = regs->csr_era;
+
+	if (pc & 3) {
+		pr_warn("%s: invalid pc 0x%lx\n", __func__, pc);
+		return;
+	}
+
+	imm_l = insn.reg0i26_format.immediate_l;
+	imm_h = insn.reg0i26_format.immediate_h;
+	switch (insn.reg0i26_format.opcode) {
+	case b_op:
+		regs->csr_era = pc + sign_extended((imm_h << 16 | imm_l) << 2, 27);
+		return;
+	case bl_op:
+		regs->csr_era = pc + sign_extended((imm_h << 16 | imm_l) << 2, 27);
+		regs->regs[1] = pc + LOONGARCH_INSN_SIZE;
+		return;
+	}
+
+	imm_l = insn.reg1i21_format.immediate_l;
+	imm_h = insn.reg1i21_format.immediate_h;
+	rj = insn.reg1i21_format.rj;
+	switch (insn.reg1i21_format.opcode) {
+	case beqz_op:
+		if (regs->regs[rj] == 0)
+			regs->csr_era = pc + sign_extended((imm_h << 16 | imm_l) << 2, 22);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		return;
+	case bnez_op:
+		if (regs->regs[rj] != 0)
+			regs->csr_era = pc + sign_extended((imm_h << 16 | imm_l) << 2, 22);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		return;
+	}
+
+	imm = insn.reg2i16_format.immediate;
+	rj = insn.reg2i16_format.rj;
+	rd = insn.reg2i16_format.rd;
+	switch (insn.reg2i16_format.opcode) {
+	case beq_op:
+		if (regs->regs[rj] == regs->regs[rd])
+			regs->csr_era = pc + sign_extended(imm << 2, 17);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		break;
+	case bne_op:
+		if (regs->regs[rj] != regs->regs[rd])
+			regs->csr_era = pc + sign_extended(imm << 2, 17);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		break;
+	case blt_op:
+		if ((long)regs->regs[rj] < (long)regs->regs[rd])
+			regs->csr_era = pc + sign_extended(imm << 2, 17);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		break;
+	case bge_op:
+		if ((long)regs->regs[rj] >= (long)regs->regs[rd])
+			regs->csr_era = pc + sign_extended(imm << 2, 17);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		break;
+	case bltu_op:
+		if (regs->regs[rj] < regs->regs[rd])
+			regs->csr_era = pc + sign_extended(imm << 2, 17);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		break;
+	case bgeu_op:
+		if (regs->regs[rj] >= regs->regs[rd])
+			regs->csr_era = pc + sign_extended(imm << 2, 17);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		break;
+	case jirl_op:
+		regs->csr_era = regs->regs[rj] + sign_extended(imm << 2, 17);
+		regs->regs[rd] = pc + LOONGARCH_INSN_SIZE;
+		break;
+	default:
+		pr_info("%s: unknown opcode\n", __func__);
+		return;
+	}
+}
+
+void simu_pc(struct pt_regs *regs, union loongarch_instruction insn)
+{
+	unsigned long pc = regs->csr_era;
+	unsigned int rd = insn.reg1i20_format.rd;
+	unsigned int imm = insn.reg1i20_format.immediate;
+
+	if (pc & 3) {
+		pr_warn("%s: invalid pc 0x%lx\n", __func__, pc);
+		return;
+	}
+
+	switch (insn.reg1i20_format.opcode) {
+	case pcaddi_op:
+		regs->regs[rd] = pc + sign_extended(imm << 2, 21);
+		break;
+	case pcaddu12i_op:
+		regs->regs[rd] = pc + sign_extended(imm << 12, 31);
+		break;
+	case pcaddu18i_op:
+		regs->regs[rd] = pc + sign_extended(imm << 18, 37);
+		break;
+	case pcalau12i_op:
+		regs->regs[rd] = pc + sign_extended(imm << 12, 31);
+		regs->regs[rd] &= ~((1 << 12) - 1);
+		break;
+	default:
+		pr_info("%s: unknown opcode\n", __func__);
+		return;
+	}
+
+	regs->csr_era += LOONGARCH_INSN_SIZE;
+}
-- 
2.1.0

[PATCH v5 2/4] LoongArch: Add kprobe support

[Tiezhu Yang]

Kprobes allows you to trap at almost any kernel address and
execute a callback function, this commit adds kprobe support
for LoongArch.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/Kconfig               |   1 +
 arch/loongarch/include/asm/inst.h    |  10 ++
 arch/loongarch/include/asm/kprobes.h |  65 +++++++
 arch/loongarch/kernel/Makefile       |   2 +
 arch/loongarch/kernel/kprobes.c      | 326 +++++++++++++++++++++++++++++++++++
 arch/loongarch/kernel/traps.c        |   6 +-
 arch/loongarch/mm/fault.c            |   4 +
 7 files changed, 410 insertions(+), 4 deletions(-)
 create mode 100644 arch/loongarch/include/asm/kprobes.h
 create mode 100644 arch/loongarch/kernel/kprobes.c

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 5c4f1dc..925d46d 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -102,6 +102,7 @@ config LOONGARCH
 	select HAVE_IOREMAP_PROT
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK
 	select HAVE_IRQ_TIME_ACCOUNTING
+	select HAVE_KPROBES
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_NMI
 	select HAVE_PCI
diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
index a91798b..f5fb2be 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -24,6 +24,10 @@
 
 #define ADDR_IMM(addr, INSN)	((addr & ADDR_IMMMASK_##INSN) >> ADDR_IMMSHIFT_##INSN)
 
+enum reg0i15_op {
+	break_op	= 0x54,
+};
+
 enum reg0i26_op {
 	b_op		= 0x14,
 	bl_op		= 0x15,
@@ -180,6 +184,11 @@ enum reg3sa2_op {
 	alsld_op	= 0x16,
 };
 
+struct reg0i15_format {
+	unsigned int immediate : 15;
+	unsigned int opcode : 17;
+};
+
 struct reg0i26_format {
 	unsigned int immediate_h : 10;
 	unsigned int immediate_l : 16;
@@ -265,6 +274,7 @@ struct reg3sa2_format {
 
 union loongarch_instruction {
 	unsigned int word;
+	struct reg0i15_format	reg0i15_format;
 	struct reg0i26_format	reg0i26_format;
 	struct reg1i20_format	reg1i20_format;
 	struct reg1i21_format	reg1i21_format;
diff --git a/arch/loongarch/include/asm/kprobes.h b/arch/loongarch/include/asm/kprobes.h
new file mode 100644
index 0000000..e2d0729
--- /dev/null
+++ b/arch/loongarch/include/asm/kprobes.h
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_LOONGARCH_KPROBES_H
+#define __ASM_LOONGARCH_KPROBES_H
+
+#include <asm-generic/kprobes.h>
+#include <asm/cacheflush.h>
+
+#ifdef CONFIG_KPROBES
+
+#include <asm/inst.h>
+
+#define __ARCH_WANT_KPROBES_INSN_SLOT
+#define MAX_INSN_SIZE			2
+
+#define flush_insn_slot(p)						\
+do {									\
+	if (p->addr)							\
+		flush_icache_range((unsigned long)p->addr,		\
+			   (unsigned long)p->addr +			\
+			   (MAX_INSN_SIZE * sizeof(kprobe_opcode_t)));	\
+} while (0)
+
+#define kretprobe_blacklist_size	0
+
+typedef union loongarch_instruction kprobe_opcode_t;
+
+/* Architecture specific copy of original instruction */
+struct arch_specific_insn {
+	/* copy of the original instruction */
+	kprobe_opcode_t *insn;
+};
+
+struct prev_kprobe {
+	struct kprobe *kp;
+	unsigned long status;
+	unsigned long saved_irq;
+	unsigned long saved_era;
+};
+
+/* per-cpu kprobe control block */
+struct kprobe_ctlblk {
+	unsigned long kprobe_status;
+	unsigned long kprobe_saved_irq;
+	unsigned long kprobe_saved_era;
+	struct prev_kprobe prev_kprobe;
+};
+
+struct patch_insn {
+	void *addr;
+	union loongarch_instruction insn;
+	atomic_t cpu_count;
+};
+
+void arch_remove_kprobe(struct kprobe *p);
+bool kprobe_fault_handler(struct pt_regs *regs, int trapnr);
+bool kprobe_breakpoint_handler(struct pt_regs *regs);
+bool kprobe_singlestep_handler(struct pt_regs *regs);
+
+#else /* !CONFIG_KPROBES */
+
+static inline bool kprobe_breakpoint_handler(struct pt_regs *regs) { return 0; }
+static inline bool kprobe_singlestep_handler(struct pt_regs *regs) { return 0; }
+
+#endif /* CONFIG_KPROBES */
+#endif /* __ASM_LOONGARCH_KPROBES_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 27a5b62..a87b7f5 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -47,4 +47,6 @@ obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o
 
 obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_regs.o
 
+obj-$(CONFIG_KPROBES)		+= kprobes.o
+
 CPPFLAGS_vmlinux.lds		:= $(KBUILD_CFLAGS)
diff --git a/arch/loongarch/kernel/kprobes.c b/arch/loongarch/kernel/kprobes.c
new file mode 100644
index 0000000..d01ecb2
--- /dev/null
+++ b/arch/loongarch/kernel/kprobes.c
@@ -0,0 +1,326 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/preempt.h>
+#include <linux/stop_machine.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_PER_CPU(struct kprobe *, current_kprobe);
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+static bool insns_are_not_supported(union loongarch_instruction insn)
+{
+	switch (insn.reg2i14_format.opcode) {
+	case llw_op:
+	case lld_op:
+	case scw_op:
+	case scd_op:
+		pr_notice("kprobe: ll or sc instructions are not supported\n");
+		return true;
+	}
+
+	switch (insn.reg1i21_format.opcode) {
+	case bceqz_op:
+		pr_notice("kprobe: bceqz or bcnez instructions are not supported\n");
+		return true;
+	}
+
+	return false;
+}
+NOKPROBE_SYMBOL(insns_are_not_supported);
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+	union loongarch_instruction insn;
+
+	insn = p->addr[0];
+	if (insns_are_not_supported(insn))
+		return -EINVAL;
+
+	p->ainsn.insn = get_insn_slot();
+	if (!p->ainsn.insn)
+		return -ENOMEM;
+
+	p->ainsn.insn[0] = *p->addr;
+	p->ainsn.insn[1] = singlestep_insn;
+
+	p->opcode = *p->addr;
+
+	return 0;
+}
+NOKPROBE_SYMBOL(arch_prepare_kprobe);
+
+static int patch_text_cb(void *data)
+{
+	struct patch_insn *param = data;
+	int ret = 0;
+
+	if (atomic_inc_return(&param->cpu_count) == num_online_cpus()) {
+		ret = larch_insn_patch_text(param->addr, param->insn.word);
+		atomic_inc(&param->cpu_count);
+	} else {
+		while (atomic_read(&param->cpu_count) <= num_online_cpus())
+			cpu_relax();
+		smp_mb();
+	}
+
+	return ret;
+}
+NOKPROBE_SYMBOL(patch_text_cb);
+
+static int patch_text(void *addr, union loongarch_instruction insn)
+{
+	struct patch_insn param = { addr, insn, ATOMIC_INIT(0) };
+
+	return stop_machine_cpuslocked(patch_text_cb, &param, cpu_online_mask);
+}
+NOKPROBE_SYMBOL(patch_text);
+
+/* Install breakpoint in text */
+void arch_arm_kprobe(struct kprobe *p)
+{
+	patch_text(p->addr, breakpoint_insn);
+}
+NOKPROBE_SYMBOL(arch_arm_kprobe);
+
+/* Remove breakpoint from text */
+void arch_disarm_kprobe(struct kprobe *p)
+{
+	patch_text(p->addr, p->opcode);
+}
+NOKPROBE_SYMBOL(arch_disarm_kprobe);
+
+void arch_remove_kprobe(struct kprobe *p)
+{
+	if (p->ainsn.insn) {
+		free_insn_slot(p->ainsn.insn, 0);
+		p->ainsn.insn = NULL;
+	}
+}
+NOKPROBE_SYMBOL(arch_remove_kprobe);
+
+static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	kcb->prev_kprobe.kp = kprobe_running();
+	kcb->prev_kprobe.status = kcb->kprobe_status;
+	kcb->prev_kprobe.saved_irq = kcb->kprobe_saved_irq;
+	kcb->prev_kprobe.saved_era = kcb->kprobe_saved_era;
+}
+NOKPROBE_SYMBOL(save_previous_kprobe);
+
+static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
+	kcb->kprobe_status = kcb->prev_kprobe.status;
+	kcb->kprobe_saved_irq = kcb->prev_kprobe.saved_irq;
+	kcb->kprobe_saved_era = kcb->prev_kprobe.saved_era;
+}
+NOKPROBE_SYMBOL(restore_previous_kprobe);
+
+static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
+			       struct kprobe_ctlblk *kcb)
+{
+	__this_cpu_write(current_kprobe, p);
+	kcb->kprobe_saved_irq = regs->csr_prmd & CSR_PRMD_PIE;
+	kcb->kprobe_saved_era = regs->csr_era;
+}
+NOKPROBE_SYMBOL(set_current_kprobe);
+
+static bool insns_are_not_simulated(struct kprobe *p, struct pt_regs *regs)
+{
+	if (is_branch_ins(&p->opcode)) {
+		simu_branch(regs, p->opcode);
+		return false;
+	} else if (is_pc_ins(&p->opcode)) {
+		simu_pc(regs, p->opcode);
+		return false;
+	} else {
+		return true;
+	}
+}
+NOKPROBE_SYMBOL(insns_are_not_simulated);
+
+static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
+			     struct kprobe_ctlblk *kcb, int reenter)
+{
+	if (reenter) {
+		save_previous_kprobe(kcb);
+		set_current_kprobe(p, regs, kcb);
+		kcb->kprobe_status = KPROBE_REENTER;
+	} else {
+		kcb->kprobe_status = KPROBE_HIT_SS;
+	}
+
+	if (p->ainsn.insn->word == breakpoint_insn.word) {
+		regs->csr_prmd &= ~CSR_PRMD_PIE;
+		regs->csr_prmd |= kcb->kprobe_saved_irq;
+		preempt_enable_no_resched();
+		return;
+	}
+
+	regs->csr_prmd &= ~CSR_PRMD_PIE;
+
+	if (insns_are_not_simulated(p, regs)) {
+		kcb->kprobe_status = KPROBE_HIT_SS;
+		regs->csr_era = (unsigned long)&p->ainsn.insn[0];
+	} else {
+		kcb->kprobe_status = KPROBE_HIT_SSDONE;
+		if (p->post_handler)
+			p->post_handler(p, regs, 0);
+		reset_current_kprobe();
+		preempt_enable_no_resched();
+	}
+}
+NOKPROBE_SYMBOL(setup_singlestep);
+
+static bool reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
+			  struct kprobe_ctlblk *kcb)
+{
+	switch (kcb->kprobe_status) {
+	case KPROBE_HIT_SSDONE:
+	case KPROBE_HIT_ACTIVE:
+		kprobes_inc_nmissed_count(p);
+		setup_singlestep(p, regs, kcb, 1);
+		break;
+	case KPROBE_HIT_SS:
+	case KPROBE_REENTER:
+		pr_warn("Failed to recover from reentered kprobes.\n");
+		dump_kprobe(p);
+		BUG();
+		break;
+	default:
+		WARN_ON(1);
+		return false;
+	}
+
+	return true;
+}
+NOKPROBE_SYMBOL(reenter_kprobe);
+
+bool kprobe_breakpoint_handler(struct pt_regs *regs)
+{
+	struct kprobe *p, *cur_kprobe;
+	struct kprobe_ctlblk *kcb;
+	unsigned long addr = instruction_pointer(regs);
+
+	preempt_disable();
+	kcb = get_kprobe_ctlblk();
+	cur_kprobe = kprobe_running();
+
+	p = get_kprobe((kprobe_opcode_t *)addr);
+	if (p) {
+		if (cur_kprobe) {
+			if (reenter_kprobe(p, regs, kcb))
+				return true;
+		} else {
+			/* Probe hit */
+			set_current_kprobe(p, regs, kcb);
+			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+			/*
+			 * If we have no pre-handler or it returned 0, we
+			 * continue with normal processing.  If we have a
+			 * pre-handler and it returned non-zero, it will
+			 * modify the execution path and no need to single
+			 * stepping. Let's just reset current kprobe and exit.
+			 *
+			 * pre_handler can hit a breakpoint and can step thru
+			 * before return.
+			 */
+			if (!p->pre_handler || !p->pre_handler(p, regs)) {
+				setup_singlestep(p, regs, kcb, 0);
+			} else {
+				reset_current_kprobe();
+				preempt_enable_no_resched();
+			}
+		}
+		return true;
+	}
+
+	/*
+	 * The breakpoint instruction was removed right
+	 * after we hit it.  Another cpu has removed
+	 * either a probepoint or a debugger breakpoint
+	 * at this address.  In either case, no further
+	 * handling of this interrupt is appropriate.
+	 * Return back to original instruction, and continue.
+	 */
+	preempt_enable_no_resched();
+	return false;
+}
+NOKPROBE_SYMBOL(kprobe_breakpoint_handler);
+
+bool kprobe_singlestep_handler(struct pt_regs *regs)
+{
+	struct kprobe *cur = kprobe_running();
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	if (!cur)
+		return false;
+
+	/* Restore back the original saved kprobes variables and continue */
+	if (kcb->kprobe_status == KPROBE_REENTER) {
+		restore_previous_kprobe(kcb);
+		goto out;
+	}
+
+	/* Call post handler */
+	kcb->kprobe_status = KPROBE_HIT_SSDONE;
+	if (cur->post_handler)
+		cur->post_handler(cur, regs, 0);
+
+	regs->csr_era = kcb->kprobe_saved_era + LOONGARCH_INSN_SIZE;
+	regs->csr_prmd |= kcb->kprobe_saved_irq;
+
+	reset_current_kprobe();
+out:
+	preempt_enable_no_resched();
+
+	return true;
+}
+NOKPROBE_SYMBOL(kprobe_singlestep_handler);
+
+bool kprobe_fault_handler(struct pt_regs *regs, int trapnr)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	if (kcb->kprobe_status & KPROBE_HIT_SS) {
+		regs->csr_era = kcb->kprobe_saved_era + LOONGARCH_INSN_SIZE;
+		regs->csr_prmd |= kcb->kprobe_saved_irq;
+
+		reset_current_kprobe();
+		preempt_enable_no_resched();
+	}
+
+	return false;
+}
+NOKPROBE_SYMBOL(kprobe_fault_handler);
+
+/*
+ * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
+ * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
+ */
+int __init arch_populate_kprobe_blacklist(void)
+{
+	return kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
+					 (unsigned long)__irqentry_text_end);
+}
+
+int __init arch_init_kprobes(void)
+{
+	return 0;
+}
diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index 7ea62fa..8525446 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -448,14 +448,12 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
 	 */
 	switch (bcode) {
 	case BRK_KPROBE_BP:
-		if (notify_die(DIE_BREAK, "Kprobe", regs, bcode,
-			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
+		if (kprobe_breakpoint_handler(regs))
 			goto out;
 		else
 			break;
 	case BRK_KPROBE_SSTEPBP:
-		if (notify_die(DIE_SSTEPBP, "Kprobe_SingleStep", regs, bcode,
-			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
+		if (kprobe_singlestep_handler(regs))
 			goto out;
 		else
 			break;
diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
index 1ccd536..fc9225a 100644
--- a/arch/loongarch/mm/fault.c
+++ b/arch/loongarch/mm/fault.c
@@ -253,12 +253,16 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 {
 	irqentry_state_t state = irqentry_enter(regs);
 
+	if (kprobe_page_fault(regs, current->thread.trap_nr))
+		goto out;
+
 	/* Enable interrupt if enabled in parent context */
 	if (likely(regs->csr_prmd & CSR_PRMD_PIE))
 		local_irq_enable();
 
 	__do_page_fault(regs, write, address);
 
+out:
 	local_irq_disable();
 
 	irqentry_exit(regs, state);
-- 
2.1.0

[PATCH v5 3/4] LoongArch: Add kretprobe support

[Tiezhu Yang]

Use the generic kretprobe trampoline handler to add kretprobe
support for LoongArch.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/Kconfig                     |  1 +
 arch/loongarch/kernel/Makefile             |  2 +-
 arch/loongarch/kernel/kprobes.c            | 24 ++++++++
 arch/loongarch/kernel/kprobes_trampoline.S | 96 ++++++++++++++++++++++++++++++
 4 files changed, 122 insertions(+), 1 deletion(-)
 create mode 100644 arch/loongarch/kernel/kprobes_trampoline.S

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 925d46d..e3eedfe 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -103,6 +103,7 @@ config LOONGARCH
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK
 	select HAVE_IRQ_TIME_ACCOUNTING
 	select HAVE_KPROBES
+	select HAVE_KRETPROBES
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_NMI
 	select HAVE_PCI
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index a87b7f5..0172a3d 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -47,6 +47,6 @@ obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o
 
 obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_regs.o
 
-obj-$(CONFIG_KPROBES)		+= kprobes.o
+obj-$(CONFIG_KPROBES)		+= kprobes.o kprobes_trampoline.o
 
 CPPFLAGS_vmlinux.lds		:= $(KBUILD_CFLAGS)
diff --git a/arch/loongarch/kernel/kprobes.c b/arch/loongarch/kernel/kprobes.c
index d01ecb2..541994c 100644
--- a/arch/loongarch/kernel/kprobes.c
+++ b/arch/loongarch/kernel/kprobes.c
@@ -320,6 +320,30 @@ int __init arch_populate_kprobe_blacklist(void)
 					 (unsigned long)__irqentry_text_end);
 }
 
+/* Called from __kretprobe_trampoline */
+void __used *trampoline_probe_handler(struct pt_regs *regs)
+{
+	return (void *)kretprobe_trampoline_handler(regs, NULL);
+}
+NOKPROBE_SYMBOL(trampoline_probe_handler);
+
+void arch_prepare_kretprobe(struct kretprobe_instance *ri,
+			    struct pt_regs *regs)
+{
+	ri->ret_addr = (kprobe_opcode_t *)regs->regs[1];
+	ri->fp = NULL;
+
+	/* Replace the return addr with trampoline addr */
+	regs->regs[1] = (unsigned long)&__kretprobe_trampoline;
+}
+NOKPROBE_SYMBOL(arch_prepare_kretprobe);
+
+int arch_trampoline_kprobe(struct kprobe *p)
+{
+	return 0;
+}
+NOKPROBE_SYMBOL(arch_trampoline_kprobe);
+
 int __init arch_init_kprobes(void)
 {
 	return 0;
diff --git a/arch/loongarch/kernel/kprobes_trampoline.S b/arch/loongarch/kernel/kprobes_trampoline.S
new file mode 100644
index 0000000..af94b0d
--- /dev/null
+++ b/arch/loongarch/kernel/kprobes_trampoline.S
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+#include <linux/linkage.h>
+#include <asm/stackframe.h>
+
+	.text
+
+	.macro save_all_base_regs
+	cfi_st  ra, PT_R1
+	cfi_st	tp, PT_R2
+	cfi_st	a0, PT_R4
+	cfi_st	a1, PT_R5
+	cfi_st	a2, PT_R6
+	cfi_st	a3, PT_R7
+	cfi_st	a4, PT_R8
+	cfi_st	a5, PT_R9
+	cfi_st	a6, PT_R10
+	cfi_st	a7, PT_R11
+	cfi_st	t0, PT_R12
+	cfi_st	t1, PT_R13
+	cfi_st	t2, PT_R14
+	cfi_st	t3, PT_R15
+	cfi_st	t4, PT_R16
+	cfi_st	t5, PT_R17
+	cfi_st	t6, PT_R18
+	cfi_st	t7, PT_R19
+	cfi_st	t8, PT_R20
+	cfi_st	u0, PT_R21
+	cfi_st	fp, PT_R22
+	cfi_st	s0, PT_R23
+	cfi_st	s1, PT_R24
+	cfi_st	s2, PT_R25
+	cfi_st	s3, PT_R26
+	cfi_st	s4, PT_R27
+	cfi_st	s5, PT_R28
+	cfi_st	s6, PT_R29
+	cfi_st	s7, PT_R30
+	cfi_st	s8, PT_R31
+	csrrd	t0, LOONGARCH_CSR_CRMD
+	andi	t0, t0, 0x7 /* extract bit[1:0] PLV, bit[2] IE */
+	LONG_S	t0, sp, PT_CRMD
+	.endm
+
+	.macro restore_all_base_regs
+	cfi_ld	tp, PT_R2
+	cfi_ld	a0, PT_R4
+	cfi_ld	a1, PT_R5
+	cfi_ld	a2, PT_R6
+	cfi_ld	a3, PT_R7
+	cfi_ld	a4, PT_R8
+	cfi_ld	a5, PT_R9
+	cfi_ld	a6, PT_R10
+	cfi_ld	a7, PT_R11
+	cfi_ld	t0, PT_R12
+	cfi_ld	t1, PT_R13
+	cfi_ld	t2, PT_R14
+	cfi_ld	t3, PT_R15
+	cfi_ld	t4, PT_R16
+	cfi_ld	t5, PT_R17
+	cfi_ld	t6, PT_R18
+	cfi_ld	t7, PT_R19
+	cfi_ld	t8, PT_R20
+	cfi_ld	u0, PT_R21
+	cfi_ld	fp, PT_R22
+	cfi_ld	s0, PT_R23
+	cfi_ld	s1, PT_R24
+	cfi_ld	s2, PT_R25
+	cfi_ld	s3, PT_R26
+	cfi_ld	s4, PT_R27
+	cfi_ld	s5, PT_R28
+	cfi_ld	s6, PT_R29
+	cfi_ld	s7, PT_R30
+	cfi_ld	s8, PT_R31
+	LONG_L  t0, sp, PT_CRMD
+	li.d	t1, 0x7 /* mask bit[1:0] PLV, bit[2] IE */
+	csrxchg t0, t1, LOONGARCH_CSR_CRMD
+	.endm
+
+SYM_CODE_START(__kretprobe_trampoline)
+	addi.d	sp, sp, -PT_SIZE
+	save_all_base_regs
+
+	addi.d	t0, sp, PT_SIZE
+	LONG_S	t0, sp, PT_R3
+
+	move a0, sp /* pt_regs */
+
+	bl trampoline_probe_handler
+
+	/* use the result as the return-address */
+	move ra, a0
+
+	restore_all_base_regs
+	addi.d	sp, sp, PT_SIZE
+
+	jr ra
+SYM_CODE_END(__kretprobe_trampoline)
-- 
2.1.0

[PATCH v5 4/4] samples/kprobes: Add LoongArch support

[Tiezhu Yang]

Add LoongArch specific info in handler_pre() and handler_post().

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 samples/kprobes/kprobe_example.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/samples/kprobes/kprobe_example.c b/samples/kprobes/kprobe_example.c
index fd346f5..ef44c61 100644
--- a/samples/kprobes/kprobe_example.c
+++ b/samples/kprobes/kprobe_example.c
@@ -55,6 +55,10 @@ static int __kprobes handler_pre(struct kprobe *p, struct pt_regs *regs)
 	pr_info("<%s> p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
 		p->symbol_name, p->addr, regs->psw.addr, regs->flags);
 #endif
+#ifdef CONFIG_LOONGARCH
+	pr_info("<%s> p->addr = 0x%p, era = 0x%lx, estat = 0x%lx\n",
+		p->symbol_name, p->addr, regs->csr_era, regs->csr_estat);
+#endif
 
 	/* A dump_stack() here will give a stack backtrace */
 	return 0;
@@ -92,6 +96,10 @@ static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
 	pr_info("<%s> p->addr, 0x%p, flags = 0x%lx\n",
 		p->symbol_name, p->addr, regs->flags);
 #endif
+#ifdef CONFIG_LOONGARCH
+	pr_info("<%s> p->addr = 0x%p, estat = 0x%lx\n",
+		p->symbol_name, p->addr, regs->csr_estat);
+#endif
 }
 
 static int __init kprobe_init(void)
-- 
2.1.0

Re: [PATCH v5 2/4] LoongArch: Add kprobe support

[Jinyang He]

On 2022-11-29 10:02, Tiezhu Yang wrote:

> Kprobes allows you to trap at almost any kernel address and
> execute a callback function, this commit adds kprobe support
> for LoongArch.
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> ---
>   arch/loongarch/Kconfig               |   1 +
>   arch/loongarch/include/asm/inst.h    |  10 ++
>   arch/loongarch/include/asm/kprobes.h |  65 +++++++
>   arch/loongarch/kernel/Makefile       |   2 +
>   arch/loongarch/kernel/kprobes.c      | 326 +++++++++++++++++++++++++++++++++++
>   arch/loongarch/kernel/traps.c        |   6 +-
>   arch/loongarch/mm/fault.c            |   4 +
>   7 files changed, 410 insertions(+), 4 deletions(-)
>   create mode 100644 arch/loongarch/include/asm/kprobes.h
>   create mode 100644 arch/loongarch/kernel/kprobes.c
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 5c4f1dc..925d46d 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -102,6 +102,7 @@ config LOONGARCH
>   	select HAVE_IOREMAP_PROT
>   	select HAVE_IRQ_EXIT_ON_IRQ_STACK
>   	select HAVE_IRQ_TIME_ACCOUNTING
> +	select HAVE_KPROBES
>   	select HAVE_MOD_ARCH_SPECIFIC
>   	select HAVE_NMI
>   	select HAVE_PCI
> diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
> index a91798b..f5fb2be 100644
> --- a/arch/loongarch/include/asm/inst.h
> +++ b/arch/loongarch/include/asm/inst.h
> @@ -24,6 +24,10 @@
>   
>   #define ADDR_IMM(addr, INSN)	((addr & ADDR_IMMMASK_##INSN) >> ADDR_IMMSHIFT_##INSN)
>   
> +enum reg0i15_op {
> +	break_op	= 0x54,
> +};
> +
>   enum reg0i26_op {
>   	b_op		= 0x14,
>   	bl_op		= 0x15,
> @@ -180,6 +184,11 @@ enum reg3sa2_op {
>   	alsld_op	= 0x16,
>   };
>   
> +struct reg0i15_format {
> +	unsigned int immediate : 15;
> +	unsigned int opcode : 17;
> +};
> +
>   struct reg0i26_format {
>   	unsigned int immediate_h : 10;
>   	unsigned int immediate_l : 16;
> @@ -265,6 +274,7 @@ struct reg3sa2_format {
>   
>   union loongarch_instruction {
>   	unsigned int word;
> +	struct reg0i15_format	reg0i15_format;
>   	struct reg0i26_format	reg0i26_format;
>   	struct reg1i20_format	reg1i20_format;
>   	struct reg1i21_format	reg1i21_format;
> diff --git a/arch/loongarch/include/asm/kprobes.h b/arch/loongarch/include/asm/kprobes.h
> new file mode 100644
> index 0000000..e2d0729
> --- /dev/null
> +++ b/arch/loongarch/include/asm/kprobes.h
> @@ -0,0 +1,65 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef __ASM_LOONGARCH_KPROBES_H
> +#define __ASM_LOONGARCH_KPROBES_H
> +
> +#include <asm-generic/kprobes.h>
> +#include <asm/cacheflush.h>
> +
> +#ifdef CONFIG_KPROBES
> +
> +#include <asm/inst.h>
> +
> +#define __ARCH_WANT_KPROBES_INSN_SLOT
> +#define MAX_INSN_SIZE			2
> +
> +#define flush_insn_slot(p)						\
> +do {									\
> +	if (p->addr)							\
> +		flush_icache_range((unsigned long)p->addr,		\
> +			   (unsigned long)p->addr +			\
> +			   (MAX_INSN_SIZE * sizeof(kprobe_opcode_t)));	\
> +} while (0)
> +
> +#define kretprobe_blacklist_size	0
> +
> +typedef union loongarch_instruction kprobe_opcode_t;
> +
> +/* Architecture specific copy of original instruction */
> +struct arch_specific_insn {
> +	/* copy of the original instruction */
> +	kprobe_opcode_t *insn;
> +};
> +
> +struct prev_kprobe {
> +	struct kprobe *kp;
> +	unsigned long status;
> +	unsigned long saved_irq;
> +	unsigned long saved_era;
> +};
> +
> +/* per-cpu kprobe control block */
> +struct kprobe_ctlblk {
> +	unsigned long kprobe_status;
> +	unsigned long kprobe_saved_irq;
> +	unsigned long kprobe_saved_era;
> +	struct prev_kprobe prev_kprobe;
> +};
> +
> +struct patch_insn {
> +	void *addr;
> +	union loongarch_instruction insn;
> +	atomic_t cpu_count;
> +};
> +
> +void arch_remove_kprobe(struct kprobe *p);
> +bool kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> +bool kprobe_breakpoint_handler(struct pt_regs *regs);
> +bool kprobe_singlestep_handler(struct pt_regs *regs);
> +
> +#else /* !CONFIG_KPROBES */
> +
> +static inline bool kprobe_breakpoint_handler(struct pt_regs *regs) { return 0; }
> +static inline bool kprobe_singlestep_handler(struct pt_regs *regs) { return 0; }
> +
> +#endif /* CONFIG_KPROBES */
> +#endif /* __ASM_LOONGARCH_KPROBES_H */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 27a5b62..a87b7f5 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -47,4 +47,6 @@ obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o
>   
>   obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_regs.o
>   
> +obj-$(CONFIG_KPROBES)		+= kprobes.o
> +
>   CPPFLAGS_vmlinux.lds		:= $(KBUILD_CFLAGS)
> diff --git a/arch/loongarch/kernel/kprobes.c b/arch/loongarch/kernel/kprobes.c
> new file mode 100644
> index 0000000..d01ecb2
> --- /dev/null
> +++ b/arch/loongarch/kernel/kprobes.c
> @@ -0,0 +1,326 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <linux/kprobes.h>
> +#include <linux/kdebug.h>
> +#include <linux/preempt.h>
> +#include <linux/stop_machine.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_PER_CPU(struct kprobe *, current_kprobe);
> +DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
> +
> +static bool insns_are_not_supported(union loongarch_instruction insn)
> +{
> +	switch (insn.reg2i14_format.opcode) {
> +	case llw_op:
> +	case lld_op:
> +	case scw_op:
> +	case scd_op:
> +		pr_notice("kprobe: ll or sc instructions are not supported\n");
> +		return true;
> +	}
> +
> +	switch (insn.reg1i21_format.opcode) {
> +	case bceqz_op:
> +		pr_notice("kprobe: bceqz or bcnez instructions are not supported\n");
> +		return true;
> +	}
> +
> +	return false;
> +}
> +NOKPROBE_SYMBOL(insns_are_not_supported);
> +
> +int arch_prepare_kprobe(struct kprobe *p)
> +{
> +	union loongarch_instruction insn;
> +
> +	insn = p->addr[0];
> +	if (insns_are_not_supported(insn))
> +		return -EINVAL;
> +
> +	p->ainsn.insn = get_insn_slot();
> +	if (!p->ainsn.insn)
> +		return -ENOMEM;
> +
> +	p->ainsn.insn[0] = *p->addr;
> +	p->ainsn.insn[1] = singlestep_insn;
> +
> +	p->opcode = *p->addr;
> +
> +	return 0;
> +}
> +NOKPROBE_SYMBOL(arch_prepare_kprobe);
> +
> +static int patch_text_cb(void *data)
> +{
> +	struct patch_insn *param = data;
> +	int ret = 0;
> +
> +	if (atomic_inc_return(&param->cpu_count) == num_online_cpus()) {
> +		ret = larch_insn_patch_text(param->addr, param->insn.word);
> +		atomic_inc(&param->cpu_count);
> +	} else {
> +		while (atomic_read(&param->cpu_count) <= num_online_cpus())
> +			cpu_relax();
> +		smp_mb();
> +	}
> +
> +	return ret;
> +}
> +NOKPROBE_SYMBOL(patch_text_cb);
> +
> +static int patch_text(void *addr, union loongarch_instruction insn)
> +{
> +	struct patch_insn param = { addr, insn, ATOMIC_INIT(0) };
> +
> +	return stop_machine_cpuslocked(patch_text_cb, &param, cpu_online_mask);
> +}
> +NOKPROBE_SYMBOL(patch_text);
> +
> +/* Install breakpoint in text */
> +void arch_arm_kprobe(struct kprobe *p)
> +{
> +	patch_text(p->addr, breakpoint_insn);
> +}
> +NOKPROBE_SYMBOL(arch_arm_kprobe);
> +
> +/* Remove breakpoint from text */
> +void arch_disarm_kprobe(struct kprobe *p)
> +{
> +	patch_text(p->addr, p->opcode);
> +}
> +NOKPROBE_SYMBOL(arch_disarm_kprobe);
> +
> +void arch_remove_kprobe(struct kprobe *p)
> +{
> +	if (p->ainsn.insn) {
> +		free_insn_slot(p->ainsn.insn, 0);
> +		p->ainsn.insn = NULL;
> +	}
> +}
> +NOKPROBE_SYMBOL(arch_remove_kprobe);
> +
> +static void save_previous_kprobe(struct kprobe_ctlblk *kcb)
> +{
> +	kcb->prev_kprobe.kp = kprobe_running();
> +	kcb->prev_kprobe.status = kcb->kprobe_status;
> +	kcb->prev_kprobe.saved_irq = kcb->kprobe_saved_irq;
> +	kcb->prev_kprobe.saved_era = kcb->kprobe_saved_era;
> +}
> +NOKPROBE_SYMBOL(save_previous_kprobe);
> +
> +static void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
> +{
> +	__this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
> +	kcb->kprobe_status = kcb->prev_kprobe.status;
> +	kcb->kprobe_saved_irq = kcb->prev_kprobe.saved_irq;
> +	kcb->kprobe_saved_era = kcb->prev_kprobe.saved_era;
> +}
> +NOKPROBE_SYMBOL(restore_previous_kprobe);
> +
> +static void set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
> +			       struct kprobe_ctlblk *kcb)
> +{
> +	__this_cpu_write(current_kprobe, p);
> +	kcb->kprobe_saved_irq = regs->csr_prmd & CSR_PRMD_PIE;
> +	kcb->kprobe_saved_era = regs->csr_era;
> +}
> +NOKPROBE_SYMBOL(set_current_kprobe);
> +
> +static bool insns_are_not_simulated(struct kprobe *p, struct pt_regs *regs)
> +{
> +	if (is_branch_ins(&p->opcode)) {
> +		simu_branch(regs, p->opcode);
> +		return false;
> +	} else if (is_pc_ins(&p->opcode)) {
> +		simu_pc(regs, p->opcode);
> +		return false;
> +	} else {
> +		return true;
> +	}
> +}
> +NOKPROBE_SYMBOL(insns_are_not_simulated);
> +
> +static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
> +			     struct kprobe_ctlblk *kcb, int reenter)
> +{
> +	if (reenter) {
> +		save_previous_kprobe(kcb);
> +		set_current_kprobe(p, regs, kcb);
> +		kcb->kprobe_status = KPROBE_REENTER;
> +	} else {
> +		kcb->kprobe_status = KPROBE_HIT_SS;
> +	}
> +
> +	if (p->ainsn.insn->word == breakpoint_insn.word) {
> +		regs->csr_prmd &= ~CSR_PRMD_PIE;
> +		regs->csr_prmd |= kcb->kprobe_saved_irq;
> +		preempt_enable_no_resched();
> +		return;
> +	}
> +
> +	regs->csr_prmd &= ~CSR_PRMD_PIE;
> +
> +	if (insns_are_not_simulated(p, regs)) {
> +		kcb->kprobe_status = KPROBE_HIT_SS;
> +		regs->csr_era = (unsigned long)&p->ainsn.insn[0];
> +	} else {
> +		kcb->kprobe_status = KPROBE_HIT_SSDONE;
> +		if (p->post_handler)
> +			p->post_handler(p, regs, 0);
> +		reset_current_kprobe();
> +		preempt_enable_no_resched();
> +	}
> +}
> +NOKPROBE_SYMBOL(setup_singlestep);
> +
> +static bool reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
> +			  struct kprobe_ctlblk *kcb)
> +{
> +	switch (kcb->kprobe_status) {
> +	case KPROBE_HIT_SSDONE:
> +	case KPROBE_HIT_ACTIVE:
> +		kprobes_inc_nmissed_count(p);
> +		setup_singlestep(p, regs, kcb, 1);
> +		break;
> +	case KPROBE_HIT_SS:
> +	case KPROBE_REENTER:
> +		pr_warn("Failed to recover from reentered kprobes.\n");
> +		dump_kprobe(p);
> +		BUG();
> +		break;
> +	default:
> +		WARN_ON(1);
> +		return false;
> +	}
> +
> +	return true;
> +}
> +NOKPROBE_SYMBOL(reenter_kprobe);
> +
> +bool kprobe_breakpoint_handler(struct pt_regs *regs)
> +{
> +	struct kprobe *p, *cur_kprobe;
> +	struct kprobe_ctlblk *kcb;
> +	unsigned long addr = instruction_pointer(regs);
> +
> +	preempt_disable();
> +	kcb = get_kprobe_ctlblk();
> +	cur_kprobe = kprobe_running();
> +
> +	p = get_kprobe((kprobe_opcode_t *)addr);
> +	if (p) {
> +		if (cur_kprobe) {
> +			if (reenter_kprobe(p, regs, kcb))
> +				return true;
> +		} else {
> +			/* Probe hit */
> +			set_current_kprobe(p, regs, kcb);
> +			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
> +
> +			/*
> +			 * If we have no pre-handler or it returned 0, we
> +			 * continue with normal processing.  If we have a
> +			 * pre-handler and it returned non-zero, it will
> +			 * modify the execution path and no need to single
> +			 * stepping. Let's just reset current kprobe and exit.
> +			 *
> +			 * pre_handler can hit a breakpoint and can step thru
> +			 * before return.
> +			 */
> +			if (!p->pre_handler || !p->pre_handler(p, regs)) {
> +				setup_singlestep(p, regs, kcb, 0);
> +			} else {
> +				reset_current_kprobe();
> +				preempt_enable_no_resched();
> +			}
> +		}
> +		return true;
> +	}
> +
> +	/*
> +	 * The breakpoint instruction was removed right
> +	 * after we hit it.  Another cpu has removed
> +	 * either a probepoint or a debugger breakpoint
> +	 * at this address.  In either case, no further
> +	 * handling of this interrupt is appropriate.
> +	 * Return back to original instruction, and continue.
> +	 */
> +	preempt_enable_no_resched();
> +	return false;

Return false? As your note explained, it should return true and stop 
this time bp exception. Otherwise it would die in another switch(bcode) 
in do_bp().

And you really should be careful that the original instruction is also a 
'break hint'. I think it is better to re-get bcode and go on bp-handler 
to avoid double trigger bp exception.


Jinyang


> +}
> +NOKPROBE_SYMBOL(kprobe_breakpoint_handler);
> +
> +bool kprobe_singlestep_handler(struct pt_regs *regs)
> +{
> +	struct kprobe *cur = kprobe_running();
> +	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> +
> +	if (!cur)
> +		return false;
> +
> +	/* Restore back the original saved kprobes variables and continue */
> +	if (kcb->kprobe_status == KPROBE_REENTER) {
> +		restore_previous_kprobe(kcb);
> +		goto out;
> +	}
> +
> +	/* Call post handler */
> +	kcb->kprobe_status = KPROBE_HIT_SSDONE;
> +	if (cur->post_handler)
> +		cur->post_handler(cur, regs, 0);
> +
> +	regs->csr_era = kcb->kprobe_saved_era + LOONGARCH_INSN_SIZE;
> +	regs->csr_prmd |= kcb->kprobe_saved_irq;
> +
> +	reset_current_kprobe();
> +out:
> +	preempt_enable_no_resched();
> +
> +	return true;
> +}
> +NOKPROBE_SYMBOL(kprobe_singlestep_handler);
> +
> +bool kprobe_fault_handler(struct pt_regs *regs, int trapnr)
> +{
> +	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> +
> +	if (kcb->kprobe_status & KPROBE_HIT_SS) {
> +		regs->csr_era = kcb->kprobe_saved_era + LOONGARCH_INSN_SIZE;
> +		regs->csr_prmd |= kcb->kprobe_saved_irq;
> +
> +		reset_current_kprobe();
> +		preempt_enable_no_resched();
> +	}
> +
> +	return false;
> +}
> +NOKPROBE_SYMBOL(kprobe_fault_handler);
> +
> +/*
> + * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
> + * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
> + */
> +int __init arch_populate_kprobe_blacklist(void)
> +{
> +	return kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
> +					 (unsigned long)__irqentry_text_end);
> +}
> +
> +int __init arch_init_kprobes(void)
> +{
> +	return 0;
> +}
> diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
> index 7ea62fa..8525446 100644
> --- a/arch/loongarch/kernel/traps.c
> +++ b/arch/loongarch/kernel/traps.c
> @@ -448,14 +448,12 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
>   	 */
>   	switch (bcode) {
>   	case BRK_KPROBE_BP:
> -		if (notify_die(DIE_BREAK, "Kprobe", regs, bcode,
> -			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
> +		if (kprobe_breakpoint_handler(regs))
>   			goto out;
>   		else
>   			break;
>   	case BRK_KPROBE_SSTEPBP:
> -		if (notify_die(DIE_SSTEPBP, "Kprobe_SingleStep", regs, bcode,
> -			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
> +		if (kprobe_singlestep_handler(regs))
>   			goto out;
>   		else
>   			break;
> diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
> index 1ccd536..fc9225a 100644
> --- a/arch/loongarch/mm/fault.c
> +++ b/arch/loongarch/mm/fault.c
> @@ -253,12 +253,16 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
>   {
>   	irqentry_state_t state = irqentry_enter(regs);
>   
> +	if (kprobe_page_fault(regs, current->thread.trap_nr))
> +		goto out;
> +
>   	/* Enable interrupt if enabled in parent context */
>   	if (likely(regs->csr_prmd & CSR_PRMD_PIE))
>   		local_irq_enable();
>   
>   	__do_page_fault(regs, write, address);
>   
> +out:
>   	local_irq_disable();
>   
>   	irqentry_exit(regs, state);