[PATCH v2 0/4] Add uprobes support for LoongArch

[PATCH v2 0/4] Add uprobes support for LoongArch

[Tiezhu Yang]

v2:
  -- Move the functions to inst.c in patch #1
  -- Pass around union for insns_not_supported(),
     insns_need_simulation() and arch_simulate_insn()

v1:
  -- Split the RFC patch #2 into two patches
  -- Use larch_insn_gen_break() to generate break insns
     for kprobes and uprobes
  -- Pass around instruction word instead of union for
     insns_not_supported(), insns_need_simulation() and
     arch_simulate_insn() to avoid type conversion for callers
  -- Add a simple test case for uprobes in the commit message

Tiezhu Yang (4):
  LoongArch: Move three functions from kprobes.c to inst.c
  LoongArch: Add larch_insn_gen_break() to generate break insns
  LoongArch: Use larch_insn_gen_break() for kprobes
  LoongArch: Add uprobes support

 arch/loongarch/Kconfig               |   3 +
 arch/loongarch/include/asm/inst.h    |  16 ++++
 arch/loongarch/include/asm/kprobes.h |   2 +-
 arch/loongarch/include/asm/uprobes.h |  36 +++++++++
 arch/loongarch/kernel/Makefile       |   1 +
 arch/loongarch/kernel/inst.c         |  48 ++++++++++++
 arch/loongarch/kernel/kprobes.c      |  75 ++++--------------
 arch/loongarch/kernel/traps.c        |   9 +--
 arch/loongarch/kernel/uprobes.c      | 142 +++++++++++++++++++++++++++++++++++
 9 files changed, 265 insertions(+), 67 deletions(-)
 create mode 100644 arch/loongarch/include/asm/uprobes.h
 create mode 100644 arch/loongarch/kernel/uprobes.c

-- 
2.1.0

[PATCH v2 1/4] LoongArch: Move three functions from kprobes.c to inst.c

[Tiezhu Yang]

The functions insns_not_supported(), insns_need_simulation()
and arch_simulate_insn() will be used for uprobes, move them
from kprobes.c to inst.c, this is preparation for later patch,
no functionality change.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/include/asm/inst.h |  4 ++++
 arch/loongarch/kernel/inst.c      | 39 +++++++++++++++++++++++++++++++++
 arch/loongarch/kernel/kprobes.c   | 46 ++-------------------------------------
 3 files changed, 45 insertions(+), 44 deletions(-)

diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
index a04fe75..9ea485b 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -409,6 +409,10 @@ static inline bool is_self_loop_ins(union loongarch_instruction *ip, struct pt_r
 void simu_pc(struct pt_regs *regs, union loongarch_instruction insn);
 void simu_branch(struct pt_regs *regs, union loongarch_instruction insn);
 
+bool insns_not_supported(union loongarch_instruction insn);
+bool insns_need_simulation(union loongarch_instruction insn);
+void arch_simulate_insn(union loongarch_instruction insn, struct pt_regs *regs);
+
 int larch_insn_read(void *addr, u32 *insnp);
 int larch_insn_write(void *addr, u32 insn);
 int larch_insn_patch_text(void *addr, u32 insn);
diff --git a/arch/loongarch/kernel/inst.c b/arch/loongarch/kernel/inst.c
index 258ef26..95219e0 100644
--- a/arch/loongarch/kernel/inst.c
+++ b/arch/loongarch/kernel/inst.c
@@ -133,6 +133,45 @@ void simu_branch(struct pt_regs *regs, union loongarch_instruction insn)
 	}
 }
 
+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;
+}
+
+bool insns_need_simulation(union loongarch_instruction insn)
+{
+	if (is_pc_ins(&insn))
+		return true;
+
+	if (is_branch_ins(&insn))
+		return true;
+
+	return false;
+}
+
+void arch_simulate_insn(union loongarch_instruction insn, struct pt_regs *regs)
+{
+	if (is_pc_ins(&insn))
+		simu_pc(regs, insn);
+	else if (is_branch_ins(&insn))
+		simu_branch(regs, insn);
+}
+
 int larch_insn_read(void *addr, u32 *insnp)
 {
 	int ret;
diff --git a/arch/loongarch/kernel/kprobes.c b/arch/loongarch/kernel/kprobes.c
index 56c8c4b..08c78d2 100644
--- a/arch/loongarch/kernel/kprobes.c
+++ b/arch/loongarch/kernel/kprobes.c
@@ -21,48 +21,6 @@ static const union loongarch_instruction singlestep_insn = {
 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);
-
-static bool insns_need_simulation(struct kprobe *p)
-{
-	if (is_pc_ins(&p->opcode))
-		return true;
-
-	if (is_branch_ins(&p->opcode))
-		return true;
-
-	return false;
-}
-NOKPROBE_SYMBOL(insns_need_simulation);
-
-static void arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
-{
-	if (is_pc_ins(&p->opcode))
-		simu_pc(regs, p->opcode);
-	else if (is_branch_ins(&p->opcode))
-		simu_branch(regs, p->opcode);
-}
-NOKPROBE_SYMBOL(arch_simulate_insn);
-
 static void arch_prepare_ss_slot(struct kprobe *p)
 {
 	p->ainsn.insn[0] = *p->addr;
@@ -89,7 +47,7 @@ int arch_prepare_kprobe(struct kprobe *p)
 	if (insns_not_supported(p->opcode))
 		return -EINVAL;
 
-	if (insns_need_simulation(p)) {
+	if (insns_need_simulation(p->opcode)) {
 		p->ainsn.insn = NULL;
 	} else {
 		p->ainsn.insn = get_insn_slot();
@@ -220,7 +178,7 @@ static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
 		regs->csr_era = (unsigned long)p->ainsn.insn;
 	} else {
 		/* simulate single steping */
-		arch_simulate_insn(p, regs);
+		arch_simulate_insn(p->opcode, regs);
 		/* now go for post processing */
 		post_kprobe_handler(p, kcb, regs);
 	}
-- 
2.1.0

[PATCH v2 2/4] LoongArch: Add larch_insn_gen_break() to generate break insns

[Tiezhu Yang]

There exist various break insns such as BRK_KPROBE_BP, BRK_KPROBE_SSTEPBP,
BRK_UPROBE_BP and BRK_UPROBE_XOLBP, add larch_insn_gen_break() to generate
break insns simpler, this is preparation for later patch.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/include/asm/inst.h | 12 ++++++++++++
 arch/loongarch/kernel/inst.c      |  9 +++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
index 9ea485b..061c0ea 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -421,6 +421,8 @@ u32 larch_insn_gen_nop(void);
 u32 larch_insn_gen_b(unsigned long pc, unsigned long dest);
 u32 larch_insn_gen_bl(unsigned long pc, unsigned long dest);
 
+u32 larch_insn_gen_break(int imm);
+
 u32 larch_insn_gen_or(enum loongarch_gpr rd, enum loongarch_gpr rj, enum loongarch_gpr rk);
 u32 larch_insn_gen_move(enum loongarch_gpr rd, enum loongarch_gpr rj);
 
@@ -439,6 +441,16 @@ static inline bool unsigned_imm_check(unsigned long val, unsigned int bit)
 	return val < (1UL << bit);
 }
 
+#define DEF_EMIT_REG0I15_FORMAT(NAME, OP)				\
+static inline void emit_##NAME(union loongarch_instruction *insn,	\
+			       int imm)					\
+{									\
+	insn->reg0i15_format.opcode = OP;				\
+	insn->reg0i15_format.immediate = imm;				\
+}
+
+DEF_EMIT_REG0I15_FORMAT(break, break_op)
+
 #define DEF_EMIT_REG0I26_FORMAT(NAME, OP)				\
 static inline void emit_##NAME(union loongarch_instruction *insn,	\
 			       int offset)				\
diff --git a/arch/loongarch/kernel/inst.c b/arch/loongarch/kernel/inst.c
index 95219e0..0bdcd46 100644
--- a/arch/loongarch/kernel/inst.c
+++ b/arch/loongarch/kernel/inst.c
@@ -247,6 +247,15 @@ u32 larch_insn_gen_bl(unsigned long pc, unsigned long dest)
 	return insn.word;
 }
 
+u32 larch_insn_gen_break(int imm)
+{
+	union loongarch_instruction insn;
+
+	emit_break(&insn, imm);
+
+	return insn.word;
+}
+
 u32 larch_insn_gen_or(enum loongarch_gpr rd, enum loongarch_gpr rj, enum loongarch_gpr rk)
 {
 	union loongarch_instruction insn;
-- 
2.1.0

[PATCH v2 3/4] LoongArch: Use larch_insn_gen_break() for kprobes

[Tiezhu Yang]

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

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

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

[PATCH v2 4/4] LoongArch: Add uprobes support

[Tiezhu Yang]

Uprobes is the user-space counterpart to kprobes, this commit
adds uprobes support for LoongArch.

Here is a simple example with CONFIG_UPROBE_EVENTS=y:

  # cat test.c
  #include <stdio.h>

  int add(int a, int b)
  {
  	  return a + b;
  }

  int main()
  {
	  return add(2, 7);
  }
  # gcc test.c -o /tmp/test
  # nm /tmp/test | grep add
  0000000120004194 T add
  # cd /sys/kernel/debug/tracing
  # echo > uprobe_events
  # echo "p:myuprobe /tmp/test:0x4194 %r4 %r5" > uprobe_events
  # echo "r:myuretprobe /tmp/test:0x4194 %r4" >> uprobe_events
  # echo 1 > events/uprobes/enable
  # echo 1 > tracing_on
  # /tmp/test
  # cat trace
  ...
  #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
  #              | |         |   |||||     |         |
              test-1060    [001] DNZff  1015.770620: myuprobe: (0x120004194) arg1=0x2 arg2=0x7
              test-1060    [001] DNZff  1015.770930: myuretprobe: (0x1200041f0 <- 0x120004194) arg1=0x9

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/loongarch/Kconfig               |   3 +
 arch/loongarch/include/asm/uprobes.h |  36 +++++++++
 arch/loongarch/kernel/Makefile       |   1 +
 arch/loongarch/kernel/traps.c        |   9 +--
 arch/loongarch/kernel/uprobes.c      | 142 +++++++++++++++++++++++++++++++++++
 5 files changed, 186 insertions(+), 5 deletions(-)
 create mode 100644 arch/loongarch/include/asm/uprobes.h
 create mode 100644 arch/loongarch/kernel/uprobes.c

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 7fd5125..ab66ad2 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -574,6 +574,9 @@ config ARCH_MMAP_RND_BITS_MIN
 config ARCH_MMAP_RND_BITS_MAX
 	default 18
 
+config ARCH_SUPPORTS_UPROBES
+	def_bool y
+
 menu "Power management options"
 
 config ARCH_SUSPEND_POSSIBLE
diff --git a/arch/loongarch/include/asm/uprobes.h b/arch/loongarch/include/asm/uprobes.h
new file mode 100644
index 0000000..c6ffcb7
--- /dev/null
+++ b/arch/loongarch/include/asm/uprobes.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_LOONGARCH_UPROBES_H
+#define __ASM_LOONGARCH_UPROBES_H
+
+#include <asm/inst.h>
+
+typedef u32 uprobe_opcode_t;
+
+#define MAX_UINSN_BYTES		LOONGARCH_INSN_SIZE
+#define UPROBE_XOL_SLOT_BYTES	MAX_UINSN_BYTES
+
+#define UPROBE_XOLBP_INSN	larch_insn_gen_break(BRK_UPROBE_XOLBP)
+#define UPROBE_SWBP_INSN	larch_insn_gen_break(BRK_UPROBE_BP)
+#define UPROBE_SWBP_INSN_SIZE	LOONGARCH_INSN_SIZE
+
+struct arch_uprobe {
+	union {
+		u32 insn[MAX_UINSN_BYTES];
+		u32 ixol[MAX_UINSN_BYTES];
+	};
+	bool simulate;
+};
+
+struct arch_uprobe_task {
+	unsigned long saved_trap_nr;
+};
+
+#ifdef CONFIG_UPROBES
+bool uprobe_breakpoint_handler(struct pt_regs *regs);
+bool uprobe_singlestep_handler(struct pt_regs *regs);
+#else /* !CONFIG_UPROBES */
+static inline bool uprobe_breakpoint_handler(struct pt_regs *regs) { return false; }
+static inline bool uprobe_singlestep_handler(struct pt_regs *regs) { return false; }
+#endif /* CONFIG_UPROBES */
+
+#endif /* __ASM_LOONGARCH_UPROBES_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 78d4e33..67b9c26 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -53,5 +53,6 @@ obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_regs.o
 obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
 
 obj-$(CONFIG_KPROBES)		+= kprobes.o kprobes_trampoline.o
+obj-$(CONFIG_UPROBES)		+= uprobes.o
 
 CPPFLAGS_vmlinux.lds		:= $(KBUILD_CFLAGS)
diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index de8ebe2..cfc2e0c 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -45,6 +45,7 @@
 #include <asm/tlb.h>
 #include <asm/types.h>
 #include <asm/unwind.h>
+#include <asm/uprobes.h>
 
 #include "access-helper.h"
 
@@ -440,7 +441,6 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
 	if (regs->csr_prmd & CSR_PRMD_PIE)
 		local_irq_enable();
 
-	current->thread.trap_nr = read_csr_excode();
 	if (__get_inst(&opcode, (u32 *)era, user))
 		goto out_sigsegv;
 
@@ -462,18 +462,17 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
 		else
 			break;
 	case BRK_UPROBE_BP:
-		if (notify_die(DIE_UPROBE, "Uprobe", regs, bcode,
-			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
+		if (uprobe_breakpoint_handler(regs))
 			goto out;
 		else
 			break;
 	case BRK_UPROBE_XOLBP:
-		if (notify_die(DIE_UPROBE_XOL, "Uprobe_XOL", regs, bcode,
-			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
+		if (uprobe_singlestep_handler(regs))
 			goto out;
 		else
 			break;
 	default:
+		current->thread.trap_nr = read_csr_excode();
 		if (notify_die(DIE_TRAP, "Break", regs, bcode,
 			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
 			goto out;
diff --git a/arch/loongarch/kernel/uprobes.c b/arch/loongarch/kernel/uprobes.c
new file mode 100644
index 0000000..628c39d
--- /dev/null
+++ b/arch/loongarch/kernel/uprobes.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/highmem.h>
+#include <linux/ptrace.h>
+#include <linux/uprobes.h>
+#include <linux/sched.h>
+#include <asm/cacheflush.h>
+
+#define UPROBE_TRAP_NR	UINT_MAX
+
+int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
+			     struct mm_struct *mm, unsigned long addr)
+{
+	union loongarch_instruction insn;
+
+	if (addr & 0x3)
+		return -EILSEQ;
+
+	insn.word = auprobe->insn[0];
+
+	if (insns_not_supported(insn))
+		return -EINVAL;
+
+	if (insns_need_simulation(insn)) {
+		auprobe->ixol[0] = larch_insn_gen_nop();
+		auprobe->simulate = true;
+	} else {
+		auprobe->ixol[0] = auprobe->insn[0];
+		auprobe->simulate = false;
+	}
+
+	auprobe->ixol[1] = UPROBE_XOLBP_INSN;
+
+	return 0;
+}
+
+int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct uprobe_task *utask = current->utask;
+
+	utask->autask.saved_trap_nr = current->thread.trap_nr;
+	current->thread.trap_nr = UPROBE_TRAP_NR;
+	instruction_pointer_set(regs, utask->xol_vaddr);
+
+	return 0;
+}
+
+int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct uprobe_task *utask = current->utask;
+
+	WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
+	current->thread.trap_nr = utask->autask.saved_trap_nr;
+	instruction_pointer_set(regs, utask->vaddr + LOONGARCH_INSN_SIZE);
+
+	return 0;
+}
+
+void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct uprobe_task *utask = current->utask;
+
+	current->thread.trap_nr = utask->autask.saved_trap_nr;
+	instruction_pointer_set(regs, utask->vaddr);
+}
+
+bool arch_uprobe_xol_was_trapped(struct task_struct *t)
+{
+	if (t->thread.trap_nr != UPROBE_TRAP_NR)
+		return true;
+
+	return false;
+}
+
+bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	union loongarch_instruction insn;
+
+	if (!auprobe->simulate)
+		return false;
+
+	insn.word = auprobe->insn[0];
+	arch_simulate_insn(insn, regs);
+
+	return true;
+}
+
+unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
+						struct pt_regs *regs)
+{
+	unsigned long ra = regs->regs[1];
+
+	regs->regs[1] = trampoline_vaddr;
+
+	return ra;
+}
+
+bool arch_uretprobe_is_alive(struct return_instance *ret,
+			     enum rp_check ctx, struct pt_regs *regs)
+{
+	if (ctx == RP_CHECK_CHAIN_CALL)
+		return regs->regs[3] <= ret->stack;
+	else
+		return regs->regs[3] < ret->stack;
+}
+
+int arch_uprobe_exception_notify(struct notifier_block *self,
+				 unsigned long val, void *data)
+{
+	return NOTIFY_DONE;
+}
+
+bool uprobe_breakpoint_handler(struct pt_regs *regs)
+{
+	if (uprobe_pre_sstep_notifier(regs))
+		return true;
+
+	return false;
+}
+
+bool uprobe_singlestep_handler(struct pt_regs *regs)
+{
+	if (uprobe_post_sstep_notifier(regs))
+		return true;
+
+	return false;
+}
+
+unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
+{
+	return instruction_pointer(regs);
+}
+
+void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
+			   void *src, unsigned long len)
+{
+	void *kaddr = kmap_local_page(page);
+	void *dst = kaddr + (vaddr & ~PAGE_MASK);
+
+	memcpy(dst, src, len);
+	flush_icache_range((unsigned long)dst, (unsigned long)dst + len);
+	kunmap_local(kaddr);
+}
-- 
2.1.0

Re: [PATCH v2 4/4] LoongArch: Add uprobes support

[Youling Tang]

Hi, Tiezhu

On 04/14/2023 05:33 PM, Tiezhu Yang wrote:

/* snip */

> diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
> index de8ebe2..cfc2e0c 100644
> --- a/arch/loongarch/kernel/traps.c
> +++ b/arch/loongarch/kernel/traps.c
> @@ -45,6 +45,7 @@
>  #include <asm/tlb.h>
>  #include <asm/types.h>
>  #include <asm/unwind.h>
> +#include <asm/uprobes.h>
>
>  #include "access-helper.h"
>
> @@ -440,7 +441,6 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
>  	if (regs->csr_prmd & CSR_PRMD_PIE)
>  		local_irq_enable();
>
> -	current->thread.trap_nr = read_csr_excode();
>  	if (__get_inst(&opcode, (u32 *)era, user))
>  		goto out_sigsegv;
>
> @@ -462,18 +462,17 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
>  		else
>  			break;
>  	case BRK_UPROBE_BP:
> -		if (notify_die(DIE_UPROBE, "Uprobe", regs, bcode,
> -			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
> +		if (uprobe_breakpoint_handler(regs))
>  			goto out;
>  		else
>  			break;
>  	case BRK_UPROBE_XOLBP:
> -		if (notify_die(DIE_UPROBE_XOL, "Uprobe_XOL", regs, bcode,
> -			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
> +		if (uprobe_singlestep_handler(regs))

After the above modification, we should remove the DIE_UPROBE and
DIE_UPROBE_XOL definitions in arch/loongarch/include/asm/kdebug.h.

At the same time DIE_BREAK, DIE_SSTEPBP and DIE_PAGE_FAULT also need to
be removed after 6d4cc40fb5f581 ("LoongArch: Add kprobes support").

Thanks,
Youling
>  			goto out;
>  		else
>  			break;
>  	default:
> +		current->thread.trap_nr = read_csr_excode();
>  		if (notify_die(DIE_TRAP, "Break", regs, bcode,
>  			       current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
>  			goto out;

Re: [PATCH v2 0/4] Add uprobes support for LoongArch

[Hengqi Chen]

Hi Tiezhu:

On 2023/4/14 17:32, Tiezhu Yang wrote:
> v2:
>   -- Move the functions to inst.c in patch #1
>   -- Pass around union for insns_not_supported(),
>      insns_need_simulation() and arch_simulate_insn()
> 
> v1:
>   -- Split the RFC patch #2 into two patches
>   -- Use larch_insn_gen_break() to generate break insns
>      for kprobes and uprobes
>   -- Pass around instruction word instead of union for
>      insns_not_supported(), insns_need_simulation() and
>      arch_simulate_insn() to avoid type conversion for callers
>   -- Add a simple test case for uprobes in the commit message
> 
> Tiezhu Yang (4):
>   LoongArch: Move three functions from kprobes.c to inst.c
>   LoongArch: Add larch_insn_gen_break() to generate break insns
>   LoongArch: Use larch_insn_gen_break() for kprobes
>   LoongArch: Add uprobes support
> 
>  arch/loongarch/Kconfig               |   3 +
>  arch/loongarch/include/asm/inst.h    |  16 ++++
>  arch/loongarch/include/asm/kprobes.h |   2 +-
>  arch/loongarch/include/asm/uprobes.h |  36 +++++++++
>  arch/loongarch/kernel/Makefile       |   1 +
>  arch/loongarch/kernel/inst.c         |  48 ++++++++++++
>  arch/loongarch/kernel/kprobes.c      |  75 ++++--------------
>  arch/loongarch/kernel/traps.c        |   9 +--
>  arch/loongarch/kernel/uprobes.c      | 142 +++++++++++++++++++++++++++++++++++
>  9 files changed, 265 insertions(+), 67 deletions(-)
>  create mode 100644 arch/loongarch/include/asm/uprobes.h
>  create mode 100644 arch/loongarch/kernel/uprobes.c
> 

I've test this series and found one corner case:

#include <pthread.h>
#include <stdio.h>
#include <thread>

static pthread_spinlock_t lock;
static int count = 0;
static const int n = 10000;

int main()
{
	int ret;

	ret = pthread_spin_init(&lock, PTHREAD_PROCESS_PRIVATE);
	if (ret)
		return -1;

	auto t1 = std::thread([&](){
		for (auto i = 0; i < n; i++) {
			pthread_spin_lock(&lock);
			count++;
			pthread_spin_unlock(&lock);
		}
	});

	auto t2 = std::thread([&](){
		for (auto i = 0; i < n; i++) {
			pthread_spin_lock(&lock);
			count++;
			pthread_spin_unlock(&lock);
		}
	});

	auto t3 = std::thread([&](){
		for (auto i = 0; i < n; i++) {
			pthread_spin_lock(&lock);
			count++;
			pthread_spin_unlock(&lock);
		}
	});

	t1.join();
	t2.join();
	t3.join();

	pthread_spin_destroy(&lock);

	printf("%d\n", count);
	return 0;
}

When I try to uprobe the pthread_spin_lock calls, the application core dumped.
On X86, this will return -EINVAL instead of crashing the userspace application.
Probably, we should add more opcode to insns_not_supported().

Cheers,
---
Hengqi

Re: [PATCH v2 4/4] LoongArch: Add uprobes support

[Tiezhu Yang]

On 04/17/2023 10:04 AM, Youling Tang wrote:
> Hi, Tiezhu
>
> On 04/14/2023 05:33 PM, Tiezhu Yang wrote:
>
> /* snip */
>
>> diff --git a/arch/loongarch/kernel/traps.c
>> b/arch/loongarch/kernel/traps.c
>> index de8ebe2..cfc2e0c 100644
>> --- a/arch/loongarch/kernel/traps.c
>> +++ b/arch/loongarch/kernel/traps.c
>> @@ -45,6 +45,7 @@
>>  #include <asm/tlb.h>
>>  #include <asm/types.h>
>>  #include <asm/unwind.h>
>> +#include <asm/uprobes.h>
>>
>>  #include "access-helper.h"
>>
>> @@ -440,7 +441,6 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
>>      if (regs->csr_prmd & CSR_PRMD_PIE)
>>          local_irq_enable();
>>
>> -    current->thread.trap_nr = read_csr_excode();
>>      if (__get_inst(&opcode, (u32 *)era, user))
>>          goto out_sigsegv;
>>
>> @@ -462,18 +462,17 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
>>          else
>>              break;
>>      case BRK_UPROBE_BP:
>> -        if (notify_die(DIE_UPROBE, "Uprobe", regs, bcode,
>> -                   current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
>> +        if (uprobe_breakpoint_handler(regs))
>>              goto out;
>>          else
>>              break;
>>      case BRK_UPROBE_XOLBP:
>> -        if (notify_die(DIE_UPROBE_XOL, "Uprobe_XOL", regs, bcode,
>> -                   current->thread.trap_nr, SIGTRAP) == NOTIFY_STOP)
>> +        if (uprobe_singlestep_handler(regs))
>
> After the above modification, we should remove the DIE_UPROBE and
> DIE_UPROBE_XOL definitions in arch/loongarch/include/asm/kdebug.h.
>
> At the same time DIE_BREAK, DIE_SSTEPBP and DIE_PAGE_FAULT also need to
> be removed after 6d4cc40fb5f581 ("LoongArch: Add kprobes support").
>

OK, thank you, will do it.

Thanks,
Tiezhu

Re: [PATCH v2 0/4] Add uprobes support for LoongArch

[Tiezhu Yang]

On 04/17/2023 11:17 AM, Hengqi Chen wrote:
> Hi Tiezhu:
>

...

>
> When I try to uprobe the pthread_spin_lock calls, the application core dumped.
> On X86, this will return -EINVAL instead of crashing the userspace application.
> Probably, we should add more opcode to insns_not_supported().
>

Yes, the atomic memory access instructions such as amswap_db.w
should not be supported, like llsc instructions, let me add them
in insns_not_supported(), thank you.

Thanks,
Tiezhu