v3:
-- Rebase on the latest code
-- Check the alignment of PC in simu_branch() and simu_pc()
-- Add ibar in flush_insn_slot()
-- Rename kprobe_{pre,post}_handler() to {post_}kprobe_handler
-- Add preempt_disable() and preempt_enable_no_resched()
-- Remove r0 save/restore and do some minor changes
in kprobes_trampoline.S
-- Do not enable CONFIG_KPROBES by default
v2:
-- Split simu_branch() and simu_pc() into a single patch
-- Call kprobe_page_fault() in do_page_fault()
-- Add kprobes_trampoline.S for kretprobe
Tiezhu Yang (4):
LoongArch: Simulate branch and PC instructions
LoongArch: Add kprobe support
LoongArch: Add kretprobe support
samples/kprobes: Add LoongArch support
arch/loongarch/Kconfig | 2 +
arch/loongarch/include/asm/inst.h | 22 ++
arch/loongarch/include/asm/kprobes.h | 52 +++++
arch/loongarch/include/asm/ptrace.h | 1 +
arch/loongarch/kernel/Makefile | 2 +
arch/loongarch/kernel/inst.c | 123 ++++++++++
arch/loongarch/kernel/kprobes.c | 348 +++++++++++++++++++++++++++++
arch/loongarch/kernel/kprobes_trampoline.S | 96 ++++++++
arch/loongarch/mm/fault.c | 4 +
samples/kprobes/kprobe_example.c | 8 +
10 files changed, 658 insertions(+)
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
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 <[email protected]>
---
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/inst.h | 10 ++
arch/loongarch/include/asm/kprobes.h | 52 ++++++
arch/loongarch/kernel/Makefile | 2 +
arch/loongarch/kernel/kprobes.c | 324 +++++++++++++++++++++++++++++++++++
arch/loongarch/mm/fault.c | 4 +
6 files changed, 393 insertions(+)
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 1943f84..cd71a86 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -95,6 +95,7 @@ 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 dea85e7..3e2f870 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -22,6 +22,10 @@
#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,
@@ -178,6 +182,11 @@ 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;
@@ -263,6 +272,7 @@ struct reg3sa2_format {
union loongarch_instruction {
unsigned int word;
+ struct reg0i15_format reg0i15_format;
struct reg0i26_format reg0i26_format;
struct reg1i20_format reg1i20_format;
struct reg1i21_format reg1i21_format;
diff --git a/arch/loongarch/include/asm/kprobes.h b/arch/loongarch/include/asm/kprobes.h
new file mode 100644
index 0000000..4579885
--- /dev/null
+++ b/arch/loongarch/include/asm/kprobes.h
@@ -0,0 +1,52 @@
+/* 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);
+
+#endif /* CONFIG_KPROBES */
+#endif /* __ASM_LOONGARCH_KPROBES_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 8674453..ac77eb7 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -34,4 +34,6 @@ 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..a6858f9
--- /dev/null
+++ b/arch/loongarch/kernel/kprobes.c
@@ -0,0 +1,324 @@
+// 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_are_not_supported(union loongarch_instruction insn)
+{
+ switch (insn.reg2i14_format.opcode) {
+ case llw_op:
+ case lld_op:
+ case scw_op:
+ case scd_op:
+ pr_notice("kprobe: ll or sc instructions are not supported\n");
+ return true;
+ }
+
+ switch (insn.reg1i21_format.opcode) {
+ case bceqz_op:
+ pr_notice("kprobe: bceqz or bcnez instructions are not supported\n");
+ return true;
+ }
+
+ return false;
+}
+NOKPROBE_SYMBOL(insns_are_not_supported);
+
+int arch_prepare_kprobe(struct kprobe *p)
+{
+ union loongarch_instruction insn;
+
+ insn = p->addr[0];
+ if (insns_are_not_supported(insn))
+ return -EINVAL;
+
+ p->ainsn.insn = get_insn_slot();
+ if (!p->ainsn.insn)
+ return -ENOMEM;
+
+ p->ainsn.insn[0] = *p->addr;
+ p->ainsn.insn[1] = singlestep_insn;
+
+ p->opcode = *p->addr;
+
+ return 0;
+}
+NOKPROBE_SYMBOL(arch_prepare_kprobe);
+
+/* 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_are_not_simulated(struct kprobe *p, struct pt_regs *regs)
+{
+ if (is_branch_ins(&p->opcode)) {
+ simu_branch(regs, p->opcode);
+ return false;
+ } else if (is_pc_ins(&p->opcode)) {
+ simu_pc(regs, p->opcode);
+ return false;
+ } else {
+ return true;
+ }
+}
+NOKPROBE_SYMBOL(insns_are_not_simulated);
+
+static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb, int reenter)
+{
+ if (reenter) {
+ save_previous_kprobe(kcb);
+ set_current_kprobe(p, regs, kcb);
+ kcb->kprobe_status = KPROBE_REENTER;
+ } else {
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ }
+
+ if (p->ainsn.insn->word == breakpoint_insn.word) {
+ regs->csr_prmd &= ~CSR_PRMD_PIE;
+ regs->csr_prmd |= kcb->kprobe_saved_irq;
+ preempt_enable_no_resched();
+ return;
+ }
+
+ regs->csr_prmd &= ~CSR_PRMD_PIE;
+
+ if (insns_are_not_simulated(p, regs)) {
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ regs->csr_era = (unsigned long)&p->ainsn.insn[0];
+ } else {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ if (p->post_handler)
+ p->post_handler(p, regs, 0);
+ reset_current_kprobe();
+ preempt_enable_no_resched();
+ }
+}
+NOKPROBE_SYMBOL(setup_singlestep);
+
+static bool reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb)
+{
+ switch (kcb->kprobe_status) {
+ case KPROBE_HIT_SSDONE:
+ case KPROBE_HIT_ACTIVE:
+ kprobes_inc_nmissed_count(p);
+ setup_singlestep(p, regs, kcb, 1);
+ break;
+ case KPROBE_HIT_SS:
+ case KPROBE_REENTER:
+ pr_warn("Failed to recover from reentered kprobes.\n");
+ dump_kprobe(p);
+ BUG();
+ break;
+ default:
+ WARN_ON(1);
+ return false;
+ }
+
+ return true;
+}
+NOKPROBE_SYMBOL(reenter_kprobe);
+
+static bool kprobe_handler(struct pt_regs *regs)
+{
+ struct kprobe *p, *cur_kprobe;
+ struct kprobe_ctlblk *kcb;
+ unsigned long addr = instruction_pointer(regs);
+
+ preempt_disable();
+ kcb = get_kprobe_ctlblk();
+ cur_kprobe = kprobe_running();
+
+ p = get_kprobe((kprobe_opcode_t *) addr);
+ if (p) {
+ if (cur_kprobe) {
+ if (reenter_kprobe(p, regs, kcb))
+ return true;
+ } else {
+ /* Probe hit */
+ set_current_kprobe(p, regs, kcb);
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+ /*
+ * If we have no pre-handler or it returned 0, we
+ * continue with normal processing. If we have a
+ * pre-handler and it returned non-zero, it will
+ * modify the execution path and no need to single
+ * stepping. Let's just reset current kprobe and exit.
+ *
+ * pre_handler can hit a breakpoint and can step thru
+ * before return.
+ */
+ if (!p->pre_handler || !p->pre_handler(p, regs)) {
+ setup_singlestep(p, regs, kcb, 0);
+ } else {
+ reset_current_kprobe();
+ preempt_enable_no_resched();
+ }
+ }
+ return true;
+ }
+
+ /*
+ * The breakpoint instruction was removed right
+ * after we hit it. Another cpu has removed
+ * either a probepoint or a debugger breakpoint
+ * at this address. In either case, no further
+ * handling of this interrupt is appropriate.
+ * Return back to original instruction, and continue.
+ */
+ preempt_enable_no_resched();
+ return false;
+}
+NOKPROBE_SYMBOL(kprobe_handler);
+
+static bool post_kprobe_handler(struct pt_regs *regs)
+{
+ struct kprobe *cur = kprobe_running();
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+ if (!cur)
+ return false;
+
+ /* Restore back the original saved kprobes variables and continue */
+ if (kcb->kprobe_status == KPROBE_REENTER) {
+ restore_previous_kprobe(kcb);
+ goto out;
+ }
+
+ /* Call post handler */
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ if (cur->post_handler)
+ cur->post_handler(cur, regs, 0);
+
+ regs->csr_era = kcb->kprobe_saved_era + LOONGARCH_INSN_SIZE;
+ regs->csr_prmd |= kcb->kprobe_saved_irq;
+
+ reset_current_kprobe();
+out:
+ preempt_enable_no_resched();
+
+ return true;
+}
+NOKPROBE_SYMBOL(post_kprobe_handler);
+
+bool kprobe_fault_handler(struct pt_regs *regs, int trapnr)
+{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+ if (kcb->kprobe_status & KPROBE_HIT_SS) {
+ regs->csr_era = kcb->kprobe_saved_era + LOONGARCH_INSN_SIZE;
+ regs->csr_prmd |= kcb->kprobe_saved_irq;
+
+ reset_current_kprobe();
+ preempt_enable_no_resched();
+ }
+
+ return false;
+}
+NOKPROBE_SYMBOL(kprobe_fault_handler);
+
+int kprobe_exceptions_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct die_args *args = (struct die_args *)data;
+ int ret = NOTIFY_DONE;
+
+ switch (val) {
+ case DIE_BREAK:
+ if (kprobe_handler(args->regs))
+ ret = NOTIFY_STOP;
+ break;
+ case DIE_SSTEPBP:
+ if (post_kprobe_handler(args->regs))
+ ret = NOTIFY_STOP;
+ break;
+ default:
+ break;
+ }
+
+ return ret;
+}
+NOKPROBE_SYMBOL(kprobe_exceptions_notify);
+
+/*
+ * 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/mm/fault.c b/arch/loongarch/mm/fault.c
index 1ccd536..fc9225a 100644
--- a/arch/loongarch/mm/fault.c
+++ b/arch/loongarch/mm/fault.c
@@ -253,12 +253,16 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
{
irqentry_state_t state = irqentry_enter(regs);
+ if (kprobe_page_fault(regs, current->thread.trap_nr))
+ goto out;
+
/* Enable interrupt if enabled in parent context */
if (likely(regs->csr_prmd & CSR_PRMD_PIE))
local_irq_enable();
__do_page_fault(regs, write, address);
+out:
local_irq_disable();
irqentry_exit(regs, state);
--
2.1.0
Add LoongArch specific info in handler_pre() and handler_post().
Signed-off-by: Tiezhu Yang <[email protected]>
---
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
Hi, tiezhu
On 2022/11/16 上午10:36, Tiezhu Yang wrote:
> Kprobes allows you to trap at almost any kernel address and
> execute a callback function, this commit adds kprobe support
> for LoongArch.
>
> Signed-off-by: Tiezhu Yang <[email protected]>
> ---
> arch/loongarch/Kconfig | 1 +
> arch/loongarch/include/asm/inst.h | 10 ++
> arch/loongarch/include/asm/kprobes.h | 52 ++++++
> arch/loongarch/kernel/Makefile | 2 +
> arch/loongarch/kernel/kprobes.c | 324 +++++++++++++++++++++++++++++++++++
> arch/loongarch/mm/fault.c | 4 +
> 6 files changed, 393 insertions(+)
> 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 1943f84..cd71a86 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -95,6 +95,7 @@ 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 dea85e7..3e2f870 100644
> --- a/arch/loongarch/include/asm/inst.h
> +++ b/arch/loongarch/include/asm/inst.h
> @@ -22,6 +22,10 @@
>
> #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,
> @@ -178,6 +182,11 @@ 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;
> @@ -263,6 +272,7 @@ struct reg3sa2_format {
>
> union loongarch_instruction {
> unsigned int word;
> + struct reg0i15_format reg0i15_format;
> struct reg0i26_format reg0i26_format;
> struct reg1i20_format reg1i20_format;
> struct reg1i21_format reg1i21_format;
> diff --git a/arch/loongarch/include/asm/kprobes.h b/arch/loongarch/include/asm/kprobes.h
> new file mode 100644
> index 0000000..4579885
> --- /dev/null
> +++ b/arch/loongarch/include/asm/kprobes.h
> @@ -0,0 +1,52 @@
> +/* 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);
> +
> +#endif /* CONFIG_KPROBES */
> +#endif /* __ASM_LOONGARCH_KPROBES_H */
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 8674453..ac77eb7 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -34,4 +34,6 @@ 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..a6858f9
> --- /dev/null
> +++ b/arch/loongarch/kernel/kprobes.c
> @@ -0,0 +1,324 @@
> +// 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_are_not_supported(union loongarch_instruction insn)
> +{
> + switch (insn.reg2i14_format.opcode) {
> + case llw_op:
> + case lld_op:
> + case scw_op:
> + case scd_op:
> + pr_notice("kprobe: ll or sc instructions are not supported\n");
> + return true;
> + }
> +
> + switch (insn.reg1i21_format.opcode) {
> + case bceqz_op:
> + pr_notice("kprobe: bceqz or bcnez instructions are not supported\n");
> + return true;
> + }
> +
> + return false;
> +}
> +NOKPROBE_SYMBOL(insns_are_not_supported);
> +
> +int arch_prepare_kprobe(struct kprobe *p)
> +{
> + union loongarch_instruction insn;
> +
> + insn = p->addr[0];
> + if (insns_are_not_supported(insn))
> + return -EINVAL;
> +
> + p->ainsn.insn = get_insn_slot();
> + if (!p->ainsn.insn)
> + return -ENOMEM;
> +
> + p->ainsn.insn[0] = *p->addr;
> + p->ainsn.insn[1] = singlestep_insn;
> +
> + p->opcode = *p->addr;
> +
> + return 0;
> +}
> +NOKPROBE_SYMBOL(arch_prepare_kprobe);
> +
> +/* 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_are_not_simulated(struct kprobe *p, struct pt_regs *regs)
> +{
> + if (is_branch_ins(&p->opcode)) {
> + simu_branch(regs, p->opcode);
> + return false;
> + } else if (is_pc_ins(&p->opcode)) {
> + simu_pc(regs, p->opcode);
> + return false;
> + } else {
> + return true;
> + }
> +}
> +NOKPROBE_SYMBOL(insns_are_not_simulated);
> +
> +static void setup_singlestep(struct kprobe *p, struct pt_regs *regs,
> + struct kprobe_ctlblk *kcb, int reenter)
> +{
> + if (reenter) {
> + save_previous_kprobe(kcb);
> + set_current_kprobe(p, regs, kcb);
> + kcb->kprobe_status = KPROBE_REENTER;
> + } else {
> + kcb->kprobe_status = KPROBE_HIT_SS;
> + }
> +
> + if (p->ainsn.insn->word == breakpoint_insn.word) {
> + regs->csr_prmd &= ~CSR_PRMD_PIE;
> + regs->csr_prmd |= kcb->kprobe_saved_irq;
> + preempt_enable_no_resched();
> + return;
> + }
> +
> + regs->csr_prmd &= ~CSR_PRMD_PIE;
> +
> + if (insns_are_not_simulated(p, regs)) {
> + kcb->kprobe_status = KPROBE_HIT_SS;
> + regs->csr_era = (unsigned long)&p->ainsn.insn[0];
> + } else {
> + kcb->kprobe_status = KPROBE_HIT_SSDONE;
> + if (p->post_handler)
> + p->post_handler(p, regs, 0);
> + reset_current_kprobe();
> + preempt_enable_no_resched();
> + }
> +}
> +NOKPROBE_SYMBOL(setup_singlestep);
> +
> +static bool reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
> + struct kprobe_ctlblk *kcb)
> +{
> + switch (kcb->kprobe_status) {
> + case KPROBE_HIT_SSDONE:
> + case KPROBE_HIT_ACTIVE:
> + kprobes_inc_nmissed_count(p);
> + setup_singlestep(p, regs, kcb, 1);
> + break;
> + case KPROBE_HIT_SS:
> + case KPROBE_REENTER:
> + pr_warn("Failed to recover from reentered kprobes.\n");
> + dump_kprobe(p);
> + BUG();
> + break;
> + default:
> + WARN_ON(1);
> + return false;
> + }
> +
> + return true;
> +}
> +NOKPROBE_SYMBOL(reenter_kprobe);
> +
> +static bool kprobe_handler(struct pt_regs *regs)
> +{
> + struct kprobe *p, *cur_kprobe;
> + struct kprobe_ctlblk *kcb;
> + unsigned long addr = instruction_pointer(regs);
> +
> + preempt_disable();
> + kcb = get_kprobe_ctlblk();
> + cur_kprobe = kprobe_running();
> +
> + p = get_kprobe((kprobe_opcode_t *) addr);
> + if (p) {
> + if (cur_kprobe) {
> + if (reenter_kprobe(p, regs, kcb))
> + return true;
> + } else {
> + /* Probe hit */
> + set_current_kprobe(p, regs, kcb);
> + kcb->kprobe_status = KPROBE_HIT_ACTIVE;
> +
> + /*
> + * If we have no pre-handler or it returned 0, we
> + * continue with normal processing. If we have a
> + * pre-handler and it returned non-zero, it will
> + * modify the execution path and no need to single
> + * stepping. Let's just reset current kprobe and exit.
> + *
> + * pre_handler can hit a breakpoint and can step thru
> + * before return.
> + */
> + if (!p->pre_handler || !p->pre_handler(p, regs)) {
> + setup_singlestep(p, regs, kcb, 0);
> + } else {
> + reset_current_kprobe();
> + preempt_enable_no_resched();
> + }
> + }
> + return true;
> + }
> +
> + /*
> + * The breakpoint instruction was removed right
> + * after we hit it. Another cpu has removed
> + * either a probepoint or a debugger breakpoint
> + * at this address. In either case, no further
> + * handling of this interrupt is appropriate.
> + * Return back to original instruction, and continue.
> + */
> + preempt_enable_no_resched();
> + return false;
> +}
> +NOKPROBE_SYMBOL(kprobe_handler);
> +
> +static bool post_kprobe_handler(struct pt_regs *regs)
> +{
> + struct kprobe *cur = kprobe_running();
> + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> +
> + if (!cur)
> + return false;
> +
> + /* Restore back the original saved kprobes variables and continue */
> + if (kcb->kprobe_status == KPROBE_REENTER) {
> + restore_previous_kprobe(kcb);
> + goto out;
> + }
> +
> + /* Call post handler */
> + kcb->kprobe_status = KPROBE_HIT_SSDONE;
> + if (cur->post_handler)
> + cur->post_handler(cur, regs, 0);
> +
> + regs->csr_era = kcb->kprobe_saved_era + LOONGARCH_INSN_SIZE;
> + regs->csr_prmd |= kcb->kprobe_saved_irq;
> +
> + reset_current_kprobe();
> +out:
> + preempt_enable_no_resched();
> +
> + return true;
> +}
> +NOKPROBE_SYMBOL(post_kprobe_handler);
> +
> +bool kprobe_fault_handler(struct pt_regs *regs, int trapnr)
> +{
> + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> +
> + if (kcb->kprobe_status & KPROBE_HIT_SS) {
> + regs->csr_era = kcb->kprobe_saved_era + LOONGARCH_INSN_SIZE;
> + regs->csr_prmd |= kcb->kprobe_saved_irq;
> +
> + reset_current_kprobe();
> + preempt_enable_no_resched();
> + }
> +
> + return false;
> +}
> +NOKPROBE_SYMBOL(kprobe_fault_handler);
> +
> +int kprobe_exceptions_notify(struct notifier_block *self,
> + unsigned long val, void *data)
> +{
We should delete kprobe_exceptions_notify,
Call kprobe_handler directly inside the do_bp function, just like any
other mainstream architecture handler that simulates breakpoints.
I'm doing this with the hardware breakpoint framework, and I hope the
software breakpoints will do the same.
Thanks
-Qing
> + struct die_args *args = (struct die_args *)data;
> + int ret = NOTIFY_DONE;
> +
> + switch (val) {
> + case DIE_BREAK:
> + if (kprobe_handler(args->regs))
> + ret = NOTIFY_STOP;
> + break;
> + case DIE_SSTEPBP:
> + if (post_kprobe_handler(args->regs))
> + ret = NOTIFY_STOP;
> + break;
> + default:
> + break;
> + }
> +
> + return ret;
> +}
> +NOKPROBE_SYMBOL(kprobe_exceptions_notify);
> +
> +/*
> + * 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/mm/fault.c b/arch/loongarch/mm/fault.c
> index 1ccd536..fc9225a 100644
> --- a/arch/loongarch/mm/fault.c
> +++ b/arch/loongarch/mm/fault.c
> @@ -253,12 +253,16 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
> {
> irqentry_state_t state = irqentry_enter(regs);
>
> + if (kprobe_page_fault(regs, current->thread.trap_nr))
> + goto out;
> +
> /* Enable interrupt if enabled in parent context */
> if (likely(regs->csr_prmd & CSR_PRMD_PIE))
> local_irq_enable();
>
> __do_page_fault(regs, write, address);
>
> +out:
> local_irq_disable();
>
> irqentry_exit(regs, state);
>