[PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

[PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

[Tiezhu Yang]

v10:
  -- Remove sign_extend() based on the latest code
  -- Rename insns_are_not_supported() to insns_not_supported()
  -- Rename insns_are_not_simulated() to insns_not_simulated()
  -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
  -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()

v9:
  -- Rename sign_extended() to sign_extend()
  -- Modify kprobe_fault_handler() to handle all of kprobe_status

v8:
  -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
  -- Add code comment of preempt_disable()
  -- Put kprobe_page_fault() in __do_page_fault()
  -- Modify the check condition of break insn in kprobe_breakpoint_handler()

v7:
  -- Remove stop_machine_cpuslocked() related code

v6:
  -- Add a new patch to redefine larch_insn_patch_text() with
     stop_machine_cpuslocked()
  -- Modify kprobe_breakpoint_handler() to consider the original
     insn is break and return the correct value
  -- Modify do_bp() to refresh bcode when original insn is break

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          |  20 ++
 arch/loongarch/include/asm/kprobes.h       |  59 +++++
 arch/loongarch/include/asm/ptrace.h        |   1 +
 arch/loongarch/kernel/Makefile             |   2 +
 arch/loongarch/kernel/inst.c               | 123 ++++++++++
 arch/loongarch/kernel/kprobes.c            | 364 +++++++++++++++++++++++++++++
 arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
 arch/loongarch/kernel/traps.c              |  13 +-
 arch/loongarch/mm/fault.c                  |   3 +
 samples/kprobes/kprobe_example.c           |   8 +
 11 files changed, 687 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 v10 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   |   5 ++
 arch/loongarch/include/asm/ptrace.h |   1 +
 arch/loongarch/kernel/inst.c        | 123 ++++++++++++++++++++++++++++++++++++
 3 files changed, 129 insertions(+)

diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
index c00e151..e25fd54 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,
 };
@@ -367,6 +369,9 @@ 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 bool signed_imm_check(long val, unsigned int bit)
 {
 	return -(1L << (bit - 1)) <= val && val < (1L << (bit - 1));
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..af48faf 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_extend((imm_h << 16 | imm_l) << 2, 27);
+		return;
+	case bl_op:
+		regs->csr_era = pc + sign_extend((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_extend((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_extend((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_extend(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_extend(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_extend(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_extend(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_extend(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_extend(imm << 2, 17);
+		else
+			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
+		break;
+	case jirl_op:
+		regs->csr_era = regs->regs[rj] + sign_extend(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_extend(imm << 2, 21);
+		break;
+	case pcaddu12i_op:
+		regs->regs[rd] = pc + sign_extend(imm << 12, 31);
+		break;
+	case pcaddu18i_op:
+		regs->regs[rd] = pc + sign_extend(imm << 18, 37);
+		break;
+	case pcalau12i_op:
+		regs->regs[rd] = pc + sign_extend(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 v10 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    |  15 ++
 arch/loongarch/include/asm/kprobes.h |  59 ++++++
 arch/loongarch/kernel/Makefile       |   2 +
 arch/loongarch/kernel/kprobes.c      | 340 +++++++++++++++++++++++++++++++++++
 arch/loongarch/kernel/traps.c        |  13 +-
 arch/loongarch/mm/fault.c            |   3 +
 7 files changed, 429 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 16bf1b6..f6fc156 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 e25fd54..a7c85df 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;
@@ -335,6 +345,11 @@ static inline bool is_branch_ins(union loongarch_instruction *ip)
 		ip->reg1i21_format.opcode <= bgeu_op;
 }
 
+static inline bool is_break_ins(union loongarch_instruction *ip)
+{
+	return ip->reg0i15_format.opcode == break_op;
+}
+
 static inline bool is_ra_save_ins(union loongarch_instruction *ip)
 {
 	/* st.d $ra, $sp, offset */
diff --git a/arch/loongarch/include/asm/kprobes.h b/arch/loongarch/include/asm/kprobes.h
new file mode 100644
index 0000000..d3903f3
--- /dev/null
+++ b/arch/loongarch/include/asm/kprobes.h
@@ -0,0 +1,59 @@
+/* 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;
+};
+
+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 fcaa024..6fe4a4e 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..546a3c3
--- /dev/null
+++ b/arch/loongarch/kernel/kprobes.c
@@ -0,0 +1,340 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#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_PER_CPU(struct kprobe *, current_kprobe);
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+static bool insns_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 and sc instructions are not supported\n");
+		return true;
+	}
+
+	switch (insn.reg1i21_format.opcode) {
+	case bceqz_op:
+		pr_notice("kprobe: bceqz and bcnez instructions are not supported\n");
+		return true;
+	}
+
+	return false;
+}
+NOKPROBE_SYMBOL(insns_not_supported);
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+	union loongarch_instruction insn;
+
+	insn = p->addr[0];
+	if (insns_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);
+
+/* Install breakpoint in text */
+void arch_arm_kprobe(struct kprobe *p)
+{
+	*p->addr = breakpoint_insn;
+	flush_insn_slot(p);
+}
+NOKPROBE_SYMBOL(arch_arm_kprobe);
+
+/* Remove breakpoint from text */
+void arch_disarm_kprobe(struct kprobe *p)
+{
+	*p->addr = p->opcode;
+	flush_insn_slot(p);
+}
+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_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_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;
+	}
+
+	regs->csr_prmd &= ~CSR_PRMD_PIE;
+
+	if (p->ainsn.insn->word == breakpoint_insn.word) {
+		regs->csr_prmd |= kcb->kprobe_saved_irq;
+		preempt_enable_no_resched();
+		return;
+	}
+
+	if (insns_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_ctlblk *kcb;
+	struct kprobe *p, *cur_kprobe;
+	kprobe_opcode_t *addr = (kprobe_opcode_t *)regs->csr_era;
+
+	/*
+	 * We don't want to be preempted for the entire
+	 * duration of kprobe processing.
+	 */
+	preempt_disable();
+	kcb = get_kprobe_ctlblk();
+	cur_kprobe = kprobe_running();
+
+	p = get_kprobe(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;
+	}
+
+	if (!is_break_ins(addr)) {
+		/*
+		 * 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 true;
+	}
+
+	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 */
+	if (cur->post_handler) {
+		kcb->kprobe_status = KPROBE_HIT_SSDONE;
+		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 *cur = kprobe_running();
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	switch (kcb->kprobe_status) {
+	case KPROBE_HIT_SS:
+	case KPROBE_REENTER:
+		/*
+		 * We are here because the instruction being single
+		 * stepped caused a page fault. We reset the current
+		 * kprobe and the ip points back to the probe address
+		 * and allow the page fault handler to continue as a
+		 * normal page fault.
+		 */
+		regs->csr_era = (unsigned long) cur->addr;
+		BUG_ON(!instruction_pointer(regs));
+
+		if (kcb->kprobe_status == KPROBE_REENTER) {
+			restore_previous_kprobe(kcb);
+		} else {
+			regs->csr_prmd |= kcb->kprobe_saved_irq;
+			reset_current_kprobe();
+		}
+		preempt_enable_no_resched();
+		break;
+	case KPROBE_HIT_ACTIVE:
+	case KPROBE_HIT_SSDONE:
+		/*
+		 * In case the user-specified fault handler returned
+		 * zero, try to fix up.
+		 */
+		if (fixup_exception(regs))
+			return true;
+
+		/*
+		 * If fixup_exception() could not handle it,
+		 * let do_page_fault() fix it.
+		 */
+		break;
+	default:
+		break;
+	}
+	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 a19bb32..4d9f775 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;
@@ -479,6 +477,13 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
 			break;
 	}
 
+	if (bcode == BRK_KPROBE_BP) {
+		if (__get_inst(&opcode, (u32 *)era, user))
+			goto out_sigsegv;
+
+		bcode = (opcode & 0x7fff);
+	}
+
 	switch (bcode) {
 	case BRK_BUG:
 		bug_handler(regs);
diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
index 1ccd536..449087b 100644
--- a/arch/loongarch/mm/fault.c
+++ b/arch/loongarch/mm/fault.c
@@ -135,6 +135,9 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
 	struct vm_area_struct *vma = NULL;
 	vm_fault_t fault;
 
+	if (kprobe_page_fault(regs, current->thread.trap_nr))
+		return;
+
 	/*
 	 * We fault-in kernel-space virtual memory on-demand. The
 	 * 'reference' page table is init_mm.pgd.
-- 
2.1.0

[PATCH v10 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 f6fc156..12571ee 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 6fe4a4e..7ca6519 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 546a3c3..a8ee861 100644
--- a/arch/loongarch/kernel/kprobes.c
+++ b/arch/loongarch/kernel/kprobes.c
@@ -334,6 +334,30 @@ 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 v10 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 v10 0/4] Add kprobe and kretprobe support for LoongArch

[Huacai Chen]

Hi, Masami,

This series looks good to me now, but I'm not familiar with kprobes.
So, if you have any comments, please let me know.

And Jeff,

As we all know, you are an expert in this domain, so could you please
help me to test this series?

If there are no objections, I plan to merge this series in a few days.
But since the next merge window will be open soon, if there are any
problems, I will revert the patches to wait for the next cycle.

Thanks,
Huacai

On Fri, Dec 9, 2022 at 4:53 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
> v10:
>   -- Remove sign_extend() based on the latest code
>   -- Rename insns_are_not_supported() to insns_not_supported()
>   -- Rename insns_are_not_simulated() to insns_not_simulated()
>   -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
>   -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()
>
> v9:
>   -- Rename sign_extended() to sign_extend()
>   -- Modify kprobe_fault_handler() to handle all of kprobe_status
>
> v8:
>   -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
>   -- Add code comment of preempt_disable()
>   -- Put kprobe_page_fault() in __do_page_fault()
>   -- Modify the check condition of break insn in kprobe_breakpoint_handler()
>
> v7:
>   -- Remove stop_machine_cpuslocked() related code
>
> v6:
>   -- Add a new patch to redefine larch_insn_patch_text() with
>      stop_machine_cpuslocked()
>   -- Modify kprobe_breakpoint_handler() to consider the original
>      insn is break and return the correct value
>   -- Modify do_bp() to refresh bcode when original insn is break
>
> 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          |  20 ++
>  arch/loongarch/include/asm/kprobes.h       |  59 +++++
>  arch/loongarch/include/asm/ptrace.h        |   1 +
>  arch/loongarch/kernel/Makefile             |   2 +
>  arch/loongarch/kernel/inst.c               | 123 ++++++++++
>  arch/loongarch/kernel/kprobes.c            | 364 +++++++++++++++++++++++++++++
>  arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
>  arch/loongarch/kernel/traps.c              |  13 +-
>  arch/loongarch/mm/fault.c                  |   3 +
>  samples/kprobes/kprobe_example.c           |   8 +
>  11 files changed, 687 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
>

Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

[WANG Xuerui]

On 2022/12/9 18:01, Huacai Chen wrote:
> Hi, Masami,
> 
> This series looks good to me now, but I'm not familiar with kprobes.
> So, if you have any comments, please let me know.
> 
> And Jeff,
> 
> As we all know, you are an expert in this domain, so could you please
> help me to test this series?
> 
> If there are no objections, I plan to merge this series in a few days.
> But since the next merge window will be open soon, if there are any
> problems, I will revert the patches to wait for the next cycle.

Sorry for jumping in so late, but due to the imminence of the merge 
window, and Linus having *specifically* asked for readiness of all 6.2 
material upfront due to holidays, IMHO it could be more prudent to wait 
one more cycle. Especially considering some other people's code probably 
already made the respective maintainers more cautious due to the compile 
warnings, and hurried fixes to some other similarly hurried commits...

-- 
WANG "xen0n" Xuerui

Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/

Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

[Jeff Xie]

On Fri, Dec 9, 2022 at 6:01 PM Huacai Chen <chenhuacai@kernel.org> wrote:
>
> Hi, Masami,
>
> This series looks good to me now, but I'm not familiar with kprobes.
> So, if you have any comments, please let me know.
>
> And Jeff,
>
> As we all know, you are an expert in this domain, so could you please
> help me to test this series?
>
> If there are no objections, I plan to merge this series in a few days.
> But since the next merge window will be open soon, if there are any
> problems, I will revert the patches to wait for the next cycle.

I can't use the kprobe function normally now, tested the function from
the branch: https://github.com/loongson/linux/commits/loongarch-next

steps:
1. Try to probe __memset_fast()

[root@loongarch ]# cat /proc/kallsyms | grep __memset_fast
90000000012c75f0 T __memset_fast

./samples/kprobes/kprobe_example.c
static char symbol[KSYM_NAME_LEN] = "__memset_fast";

2. Loading the kprobe_example.ko
[root@loongarch mnt]# insmod ./kprobe_example.ko

*** The system will keep hanging ***

dmesg-messages:
gef➤  lx-dmesg
[   12.348047] handler_pre: <__memset_fast> p->addr =
0x(____ptrval____), era = 0x90000000012c75f0, estat = 0xc0000
[   12.348512] handler_post: <__memset_fast> p->addr =
0x(____ptrval____), estat = 0xc0000
[   12.348525] handler_post: <__memset_fast> p->addr =
0x(____ptrval____), estat = 0xc0000
[   12.349248] handler_pre: <__memset_fast> p->addr =
0x(____ptrval____), era = 0x90000000012c75f0, estat = 0xc0000
[   12.349259] handler_post: <__memset_fast> p->addr =
0x(____ptrval____), estat = 0xc0000

call trace:
gef➤  bt
#0  0x90000000012f45f8 in queued_spin_lock_slowpath
(lock=0x9000000001cc0018 <die_lock>, val=0x1) at
kernel/locking/qspinlock.c:383
#1  0x9000000000223b2c in die (str=str@entry=0x90000000017e3488 "Break
instruction in kernel code", regs=regs@entry=0x900000010fd735f0) at
arch/loongarch/kernel/traps.c:240
#2  0x90000000012e3968 in die_if_kernel (regs=<optimized out>,
str=<optimized out>) at ./arch/loongarch/include/asm/ptrace.h:131
#3  do_bp (regs=0x900000010fd735f0) at arch/loongarch/kernel/traps.c:485
#4  0x9000000001cb1924 in exception_handlers ()
Backtrace stopped: frame did not save the PC



> Thanks,
> Huacai
>
> On Fri, Dec 9, 2022 at 4:53 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
> >
> > v10:
> >   -- Remove sign_extend() based on the latest code
> >   -- Rename insns_are_not_supported() to insns_not_supported()
> >   -- Rename insns_are_not_simulated() to insns_not_simulated()
> >   -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
> >   -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()
> >
> > v9:
> >   -- Rename sign_extended() to sign_extend()
> >   -- Modify kprobe_fault_handler() to handle all of kprobe_status
> >
> > v8:
> >   -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
> >   -- Add code comment of preempt_disable()
> >   -- Put kprobe_page_fault() in __do_page_fault()
> >   -- Modify the check condition of break insn in kprobe_breakpoint_handler()
> >
> > v7:
> >   -- Remove stop_machine_cpuslocked() related code
> >
> > v6:
> >   -- Add a new patch to redefine larch_insn_patch_text() with
> >      stop_machine_cpuslocked()
> >   -- Modify kprobe_breakpoint_handler() to consider the original
> >      insn is break and return the correct value
> >   -- Modify do_bp() to refresh bcode when original insn is break
> >
> > 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          |  20 ++
> >  arch/loongarch/include/asm/kprobes.h       |  59 +++++
> >  arch/loongarch/include/asm/ptrace.h        |   1 +
> >  arch/loongarch/kernel/Makefile             |   2 +
> >  arch/loongarch/kernel/inst.c               | 123 ++++++++++
> >  arch/loongarch/kernel/kprobes.c            | 364 +++++++++++++++++++++++++++++
> >  arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
> >  arch/loongarch/kernel/traps.c              |  13 +-
> >  arch/loongarch/mm/fault.c                  |   3 +
> >  samples/kprobes/kprobe_example.c           |   8 +
> >  11 files changed, 687 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
> >



-- 
Thanks,
JeffXie

Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

[Hengqi Chen]

Hi, Tiezhu:

I tested this patchset from BPF side, failed with EINVAL:

    $ cat /sys/kernel/tracing/error_log
    [  262.299093] trace_kprobe: error: Failed to register probe event
      Command: p:kprobes/libbpf_4609_inet_bind_0x0_0 inet_bind+0x0
                                                 ^
--
Hengqi

On 2022/12/9 16:52, Tiezhu Yang wrote:
> v10:
>   -- Remove sign_extend() based on the latest code
>   -- Rename insns_are_not_supported() to insns_not_supported()
>   -- Rename insns_are_not_simulated() to insns_not_simulated()
>   -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
>   -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()
> 
> v9:
>   -- Rename sign_extended() to sign_extend()
>   -- Modify kprobe_fault_handler() to handle all of kprobe_status
> 
> v8:
>   -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
>   -- Add code comment of preempt_disable()
>   -- Put kprobe_page_fault() in __do_page_fault()
>   -- Modify the check condition of break insn in kprobe_breakpoint_handler()
> 
> v7:
>   -- Remove stop_machine_cpuslocked() related code
> 
> v6:
>   -- Add a new patch to redefine larch_insn_patch_text() with
>      stop_machine_cpuslocked()
>   -- Modify kprobe_breakpoint_handler() to consider the original
>      insn is break and return the correct value
>   -- Modify do_bp() to refresh bcode when original insn is break
> 
> 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          |  20 ++
>  arch/loongarch/include/asm/kprobes.h       |  59 +++++
>  arch/loongarch/include/asm/ptrace.h        |   1 +
>  arch/loongarch/kernel/Makefile             |   2 +
>  arch/loongarch/kernel/inst.c               | 123 ++++++++++
>  arch/loongarch/kernel/kprobes.c            | 364 +++++++++++++++++++++++++++++
>  arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
>  arch/loongarch/kernel/traps.c              |  13 +-
>  arch/loongarch/mm/fault.c                  |   3 +
>  samples/kprobes/kprobe_example.c           |   8 +
>  11 files changed, 687 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
> 

Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

[Qing Zhang]

Hi, Hengqi

On 2022/12/12 下午4:41, Hengqi Chen wrote:
> Hi, Tiezhu:
> 
> I tested this patchset from BPF side, failed with EINVAL:
> 
>      $ cat /sys/kernel/tracing/error_log
>      [  262.299093] trace_kprobe: error: Failed to register probe event
>        Command: p:kprobes/libbpf_4609_inet_bind_0x0_0 inet_bind+0x0
> 
This is because KPROBE_ON_FTRACE is not yet supported. Trace Event 
cannot be used now.
We will support it soon, if you want to test it by install 
kprobe_example.ko as jeff did.

Thanks
-Qing                                                ^
> --
> Hengqi
> 
> On 2022/12/9 16:52, Tiezhu Yang wrote:
>> v10:
>>    -- Remove sign_extend() based on the latest code
>>    -- Rename insns_are_not_supported() to insns_not_supported()
>>    -- Rename insns_are_not_simulated() to insns_not_simulated()
>>    -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
>>    -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()
>>
>> v9:
>>    -- Rename sign_extended() to sign_extend()
>>    -- Modify kprobe_fault_handler() to handle all of kprobe_status
>>
>> v8:
>>    -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
>>    -- Add code comment of preempt_disable()
>>    -- Put kprobe_page_fault() in __do_page_fault()
>>    -- Modify the check condition of break insn in kprobe_breakpoint_handler()
>>
>> v7:
>>    -- Remove stop_machine_cpuslocked() related code
>>
>> v6:
>>    -- Add a new patch to redefine larch_insn_patch_text() with
>>       stop_machine_cpuslocked()
>>    -- Modify kprobe_breakpoint_handler() to consider the original
>>       insn is break and return the correct value
>>    -- Modify do_bp() to refresh bcode when original insn is break
>>
>> 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          |  20 ++
>>   arch/loongarch/include/asm/kprobes.h       |  59 +++++
>>   arch/loongarch/include/asm/ptrace.h        |   1 +
>>   arch/loongarch/kernel/Makefile             |   2 +
>>   arch/loongarch/kernel/inst.c               | 123 ++++++++++
>>   arch/loongarch/kernel/kprobes.c            | 364 +++++++++++++++++++++++++++++
>>   arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
>>   arch/loongarch/kernel/traps.c              |  13 +-
>>   arch/loongarch/mm/fault.c                  |   3 +
>>   samples/kprobes/kprobe_example.c           |   8 +
>>   11 files changed, 687 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
>>

Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

[Masami Hiramatsu]

On Fri, 9 Dec 2022 18:01:44 +0800
Huacai Chen <chenhuacai@kernel.org> wrote:

> Hi, Masami,
> 
> This series looks good to me now, but I'm not familiar with kprobes.
> So, if you have any comments, please let me know.

Sorry I missed this series. Let me add some comments.
BTW, I don't have any board to run the loongarch, so I'll make
comments just about style issues.

Thanks,

> 
> And Jeff,
> 
> As we all know, you are an expert in this domain, so could you please
> help me to test this series?
> 
> If there are no objections, I plan to merge this series in a few days.
> But since the next merge window will be open soon, if there are any
> problems, I will revert the patches to wait for the next cycle.
> 
> Thanks,
> Huacai
> 
> On Fri, Dec 9, 2022 at 4:53 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
> >
> > v10:
> >   -- Remove sign_extend() based on the latest code
> >   -- Rename insns_are_not_supported() to insns_not_supported()
> >   -- Rename insns_are_not_simulated() to insns_not_simulated()
> >   -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
> >   -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()
> >
> > v9:
> >   -- Rename sign_extended() to sign_extend()
> >   -- Modify kprobe_fault_handler() to handle all of kprobe_status
> >
> > v8:
> >   -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
> >   -- Add code comment of preempt_disable()
> >   -- Put kprobe_page_fault() in __do_page_fault()
> >   -- Modify the check condition of break insn in kprobe_breakpoint_handler()
> >
> > v7:
> >   -- Remove stop_machine_cpuslocked() related code
> >
> > v6:
> >   -- Add a new patch to redefine larch_insn_patch_text() with
> >      stop_machine_cpuslocked()
> >   -- Modify kprobe_breakpoint_handler() to consider the original
> >      insn is break and return the correct value
> >   -- Modify do_bp() to refresh bcode when original insn is break
> >
> > 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          |  20 ++
> >  arch/loongarch/include/asm/kprobes.h       |  59 +++++
> >  arch/loongarch/include/asm/ptrace.h        |   1 +
> >  arch/loongarch/kernel/Makefile             |   2 +
> >  arch/loongarch/kernel/inst.c               | 123 ++++++++++
> >  arch/loongarch/kernel/kprobes.c            | 364 +++++++++++++++++++++++++++++
> >  arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
> >  arch/loongarch/kernel/traps.c              |  13 +-
> >  arch/loongarch/mm/fault.c                  |   3 +
> >  samples/kprobes/kprobe_example.c           |   8 +
> >  11 files changed, 687 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
> >


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>

Re: [PATCH v10 2/4] LoongArch: Add kprobe support

[Masami Hiramatsu]

Hi,

On Fri,  9 Dec 2022 16:52:59 +0800
Tiezhu Yang <yangtiezhu@loongson.cn> 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    |  15 ++
>  arch/loongarch/include/asm/kprobes.h |  59 ++++++
>  arch/loongarch/kernel/Makefile       |   2 +
>  arch/loongarch/kernel/kprobes.c      | 340 +++++++++++++++++++++++++++++++++++
>  arch/loongarch/kernel/traps.c        |  13 +-
>  arch/loongarch/mm/fault.c            |   3 +
>  7 files changed, 429 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 16bf1b6..f6fc156 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 e25fd54..a7c85df 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;
> @@ -335,6 +345,11 @@ static inline bool is_branch_ins(union loongarch_instruction *ip)
>  		ip->reg1i21_format.opcode <= bgeu_op;
>  }
>  
> +static inline bool is_break_ins(union loongarch_instruction *ip)
> +{
> +	return ip->reg0i15_format.opcode == break_op;
> +}
> +
>  static inline bool is_ra_save_ins(union loongarch_instruction *ip)
>  {
>  	/* st.d $ra, $sp, offset */
> diff --git a/arch/loongarch/include/asm/kprobes.h b/arch/loongarch/include/asm/kprobes.h
> new file mode 100644
> index 0000000..d3903f3
> --- /dev/null
> +++ b/arch/loongarch/include/asm/kprobes.h
> @@ -0,0 +1,59 @@
> +/* 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;
> +};
> +
> +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; }

bool should return true or false.

> +
> +#endif /* CONFIG_KPROBES */
> +#endif /* __ASM_LOONGARCH_KPROBES_H */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index fcaa024..6fe4a4e 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..546a3c3
> --- /dev/null
> +++ b/arch/loongarch/kernel/kprobes.c
> @@ -0,0 +1,340 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <linux/kprobes.h>
> +#include <linux/kdebug.h>
> +#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_PER_CPU(struct kprobe *, current_kprobe);
> +DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
> +
> +static bool insns_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 and sc instructions are not supported\n");
> +		return true;
> +	}
> +
> +	switch (insn.reg1i21_format.opcode) {
> +	case bceqz_op:
> +		pr_notice("kprobe: bceqz and bcnez instructions are not supported\n");
> +		return true;
> +	}
> +
> +	return false;
> +}
> +NOKPROBE_SYMBOL(insns_not_supported);
> +
> +int arch_prepare_kprobe(struct kprobe *p)
> +{
> +	union loongarch_instruction insn;
> +
> +	insn = p->addr[0];
> +	if (insns_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);
> +
> +/* Install breakpoint in text */
> +void arch_arm_kprobe(struct kprobe *p)
> +{
> +	*p->addr = breakpoint_insn;
> +	flush_insn_slot(p);
> +}
> +NOKPROBE_SYMBOL(arch_arm_kprobe);
> +
> +/* Remove breakpoint from text */
> +void arch_disarm_kprobe(struct kprobe *p)
> +{
> +	*p->addr = p->opcode;
> +	flush_insn_slot(p);
> +}
> +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_not_simulated(struct kprobe *p, struct pt_regs *regs)

I recommend this as "insn_simulate()" and return false if it is NOT
simulated, since this actually simulates the instruction, 

> +{
> +	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_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;
> +	}
> +
> +	regs->csr_prmd &= ~CSR_PRMD_PIE;
> +
> +	if (p->ainsn.insn->word == breakpoint_insn.word) {

Would you mean there is already another kprobe on the same address
and it is copied? The kprobe arch-independent code already checked
that and if you see this when registering new one in the arch
code, it should be rejected.

> +		regs->csr_prmd |= kcb->kprobe_saved_irq;
> +		preempt_enable_no_resched();
> +		return;
> +	}
> +
> +	if (insns_not_simulated(p, regs)) {

if (!insn_simulate(p, regs)) {
	/* fall back to normal single stepping */

> +		kcb->kprobe_status = KPROBE_HIT_SS;

No, if reentered == true, it should be KPROBE_REENTER during the
single stepping.

> +		regs->csr_era = (unsigned long)&p->ainsn.insn[0];
> +	} else {
> +		kcb->kprobe_status = KPROBE_HIT_SSDONE;

You also missed reentering case. If the kprobes hits in another kprobe
handler, it must be in KPROBE_REENTER state and do not call any user
handler.

> +		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_ctlblk *kcb;
> +	struct kprobe *p, *cur_kprobe;
> +	kprobe_opcode_t *addr = (kprobe_opcode_t *)regs->csr_era;
> +
> +	/*
> +	 * We don't want to be preempted for the entire
> +	 * duration of kprobe processing.
> +	 */
> +	preempt_disable();
> +	kcb = get_kprobe_ctlblk();
> +	cur_kprobe = kprobe_running();
> +
> +	p = get_kprobe(addr);
> +	if (p) {
> +		if (cur_kprobe) {
> +			if (reenter_kprobe(p, regs, kcb))
> +				return true;

 even if reenter_kprobe() doesn't return true, this function
eventually 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;

		^Here.

> +	}
> +
> +	if (!is_break_ins(addr)) {
> +		/*
> +		 * 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 true;
> +	}
> +
> +	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 */
> +	if (cur->post_handler) {
> +		kcb->kprobe_status = KPROBE_HIT_SSDONE;
> +		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 *cur = kprobe_running();
> +	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> +
> +	switch (kcb->kprobe_status) {
> +	case KPROBE_HIT_SS:
> +	case KPROBE_REENTER:
> +		/*
> +		 * We are here because the instruction being single
> +		 * stepped caused a page fault. We reset the current
> +		 * kprobe and the ip points back to the probe address
> +		 * and allow the page fault handler to continue as a
> +		 * normal page fault.
> +		 */
> +		regs->csr_era = (unsigned long) cur->addr;
> +		BUG_ON(!instruction_pointer(regs));
> +
> +		if (kcb->kprobe_status == KPROBE_REENTER) {
> +			restore_previous_kprobe(kcb);
> +		} else {
> +			regs->csr_prmd |= kcb->kprobe_saved_irq;
> +			reset_current_kprobe();
> +		}
> +		preempt_enable_no_resched();
> +		break;
> +	case KPROBE_HIT_ACTIVE:
> +	case KPROBE_HIT_SSDONE:

Recently, I removed these cases because this page fault will be finally
handled by the generic pagefault handler.

Thank you,

> +		/*
> +		 * In case the user-specified fault handler returned
> +		 * zero, try to fix up.
> +		 */
> +		if (fixup_exception(regs))
> +			return true;
> +
> +		/*
> +		 * If fixup_exception() could not handle it,
> +		 * let do_page_fault() fix it.
> +		 */
> +		break;
> +	default:
> +		break;
> +	}
> +	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 a19bb32..4d9f775 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;
> @@ -479,6 +477,13 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
>  			break;
>  	}
>  
> +	if (bcode == BRK_KPROBE_BP) {
> +		if (__get_inst(&opcode, (u32 *)era, user))
> +			goto out_sigsegv;
> +
> +		bcode = (opcode & 0x7fff);
> +	}
> +
>  	switch (bcode) {
>  	case BRK_BUG:
>  		bug_handler(regs);
> diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
> index 1ccd536..449087b 100644
> --- a/arch/loongarch/mm/fault.c
> +++ b/arch/loongarch/mm/fault.c
> @@ -135,6 +135,9 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
>  	struct vm_area_struct *vma = NULL;
>  	vm_fault_t fault;
>  
> +	if (kprobe_page_fault(regs, current->thread.trap_nr))
> +		return;
> +
>  	/*
>  	 * We fault-in kernel-space virtual memory on-demand. The
>  	 * 'reference' page table is init_mm.pgd.
> -- 
> 2.1.0
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>

Re: [PATCH v10 2/4] LoongArch: Add kprobe support

[Tiezhu Yang]

On 12/14/2022 03:28 PM, Masami Hiramatsu (Google) wrote:
> Hi,
>
> On Fri,  9 Dec 2022 16:52:59 +0800
> Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
>> Kprobes allows you to trap at almost any kernel address and
>> execute a callback function, this commit adds kprobe support
>> for LoongArch.

...

>> +	case KPROBE_HIT_ACTIVE:
>> +	case KPROBE_HIT_SSDONE:
>
> Recently, I removed these cases because this page fault will be finally
> handled by the generic pagefault handler.
>

Hi Masami,

I have addressed all your comments on my local machine, the code logic
looks much more clear now, thank you very much.

When I test kprobe_example.ko with a C function like "kernel_clone",
it works well, but the kernel hangs [1] when test with an assembler
function like "__memset_fast" [2].

Just did some quick research and it seems the bug is related with
kallsyms_lookup_name(), I'm looking for a solution.

[1] 
https://lore.kernel.org/loongarch/CAEr6+EC2wPAtK8zb3=e1mUiya3gv0UhqF9J_ySYx9p_96pB+tg@mail.gmail.com/
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson.git/tree/arch/loongarch/lib/memset.S?h=loongarch-next#n56

Thanks,
Tiezhu

Re: [PATCH v10 2/4] LoongArch: Add kprobe support

[Huacai Chen]

Hi, all,

This series seems have too many problems, so I will drop it. So Tiezhu
please export the latest patches from
https://github.com/loongson/linux/commits/loongarch-next, and do
modifications on top of them.

Huacai

On Fri, Dec 16, 2022 at 5:33 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
>
>
> On 12/14/2022 03:28 PM, Masami Hiramatsu (Google) wrote:
> > Hi,
> >
> > On Fri,  9 Dec 2022 16:52:59 +0800
> > Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
> >
> >> Kprobes allows you to trap at almost any kernel address and
> >> execute a callback function, this commit adds kprobe support
> >> for LoongArch.
>
> ...
>
> >> +    case KPROBE_HIT_ACTIVE:
> >> +    case KPROBE_HIT_SSDONE:
> >
> > Recently, I removed these cases because this page fault will be finally
> > handled by the generic pagefault handler.
> >
>
> Hi Masami,
>
> I have addressed all your comments on my local machine, the code logic
> looks much more clear now, thank you very much.
>
> When I test kprobe_example.ko with a C function like "kernel_clone",
> it works well, but the kernel hangs [1] when test with an assembler
> function like "__memset_fast" [2].
>
> Just did some quick research and it seems the bug is related with
> kallsyms_lookup_name(), I'm looking for a solution.
>
> [1]
> https://lore.kernel.org/loongarch/CAEr6+EC2wPAtK8zb3=e1mUiya3gv0UhqF9J_ySYx9p_96pB+tg@mail.gmail.com/
> [2]
> https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson.git/tree/arch/loongarch/lib/memset.S?h=loongarch-next#n56
>
> Thanks,
> Tiezhu
>
>

Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

[Huacai Chen]

Hi, Masami,

On Tue, Dec 13, 2022 at 11:10 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> On Fri, 9 Dec 2022 18:01:44 +0800
> Huacai Chen <chenhuacai@kernel.org> wrote:
>
> > Hi, Masami,
> >
> > This series looks good to me now, but I'm not familiar with kprobes.
> > So, if you have any comments, please let me know.
>
> Sorry I missed this series. Let me add some comments.
> BTW, I don't have any board to run the loongarch, so I'll make
> comments just about style issues.
You needn't say sorry, and you can use qemu to run loongarch if needed.

Huacai
>
> Thanks,
>
> >
> > And Jeff,
> >
> > As we all know, you are an expert in this domain, so could you please
> > help me to test this series?
> >
> > If there are no objections, I plan to merge this series in a few days.
> > But since the next merge window will be open soon, if there are any
> > problems, I will revert the patches to wait for the next cycle.
> >
> > Thanks,
> > Huacai
> >
> > On Fri, Dec 9, 2022 at 4:53 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
> > >
> > > v10:
> > >   -- Remove sign_extend() based on the latest code
> > >   -- Rename insns_are_not_supported() to insns_not_supported()
> > >   -- Rename insns_are_not_simulated() to insns_not_simulated()
> > >   -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
> > >   -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()
> > >
> > > v9:
> > >   -- Rename sign_extended() to sign_extend()
> > >   -- Modify kprobe_fault_handler() to handle all of kprobe_status
> > >
> > > v8:
> > >   -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
> > >   -- Add code comment of preempt_disable()
> > >   -- Put kprobe_page_fault() in __do_page_fault()
> > >   -- Modify the check condition of break insn in kprobe_breakpoint_handler()
> > >
> > > v7:
> > >   -- Remove stop_machine_cpuslocked() related code
> > >
> > > v6:
> > >   -- Add a new patch to redefine larch_insn_patch_text() with
> > >      stop_machine_cpuslocked()
> > >   -- Modify kprobe_breakpoint_handler() to consider the original
> > >      insn is break and return the correct value
> > >   -- Modify do_bp() to refresh bcode when original insn is break
> > >
> > > 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          |  20 ++
> > >  arch/loongarch/include/asm/kprobes.h       |  59 +++++
> > >  arch/loongarch/include/asm/ptrace.h        |   1 +
> > >  arch/loongarch/kernel/Makefile             |   2 +
> > >  arch/loongarch/kernel/inst.c               | 123 ++++++++++
> > >  arch/loongarch/kernel/kprobes.c            | 364 +++++++++++++++++++++++++++++
> > >  arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
> > >  arch/loongarch/kernel/traps.c              |  13 +-
> > >  arch/loongarch/mm/fault.c                  |   3 +
> > >  samples/kprobes/kprobe_example.c           |   8 +
> > >  11 files changed, 687 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
> > >
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>

Re: [PATCH v10 1/4] LoongArch: Simulate branch and PC instructions

[Jinyang He]

On 2022-12-09 16:52, Tiezhu Yang wrote:

> 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   |   5 ++
>   arch/loongarch/include/asm/ptrace.h |   1 +
>   arch/loongarch/kernel/inst.c        | 123 ++++++++++++++++++++++++++++++++++++
>   3 files changed, 129 insertions(+)
>
> diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
> index c00e151..e25fd54 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,
>   };
> @@ -367,6 +369,9 @@ 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 bool signed_imm_check(long val, unsigned int bit)
>   {
>   	return -(1L << (bit - 1)) <= val && val < (1L << (bit - 1));
> 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..af48faf 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_extend((imm_h << 16 | imm_l) << 2, 27);


Hi, Tiezhu,


We can use sign_extend64() in linux/bitops.h. Its assembly sequence

is slli.d+srai.d, which is more efficient and clear.


Jinyang


> +		return;
> +	case bl_op:
> +		regs->csr_era = pc + sign_extend((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_extend((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_extend((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_extend(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_extend(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_extend(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_extend(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_extend(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_extend(imm << 2, 17);
> +		else
> +			regs->csr_era = pc + LOONGARCH_INSN_SIZE;
> +		break;
> +	case jirl_op:
> +		regs->csr_era = regs->regs[rj] + sign_extend(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_extend(imm << 2, 21);
> +		break;
> +	case pcaddu12i_op:
> +		regs->regs[rd] = pc + sign_extend(imm << 12, 31);
> +		break;
> +	case pcaddu18i_op:
> +		regs->regs[rd] = pc + sign_extend(imm << 18, 37);
> +		break;
> +	case pcalau12i_op:
> +		regs->regs[rd] = pc + sign_extend(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;
> +}