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 | 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
Hi,
On Fri, 9 Dec 2022 16:52:59 +0800
Tiezhu Yang <[email protected]> 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 | 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) <[email protected]>
On 12/14/2022 03:28 PM, Masami Hiramatsu (Google) wrote:
> Hi,
>
> On Fri, 9 Dec 2022 16:52:59 +0800
> Tiezhu Yang <[email protected]> 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
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 <[email protected]> wrote:
>
>
>
> On 12/14/2022 03:28 PM, Masami Hiramatsu (Google) wrote:
> > Hi,
> >
> > On Fri, 9 Dec 2022 16:52:59 +0800
> > Tiezhu Yang <[email protected]> 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
>
>