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Message-ID: <039cf92d-ec36-1d4c-e191-1d31a7d11bd3@loongson.cn>
Date: Fri, 9 Dec 2022 11:44:58 +0800
From: Youling Tang <tangyouling@...ngson.cn>
To: Jinyang He <hejinyang@...ngson.cn>,
Huacai Chen <chenhuacai@...nel.org>,
Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: WANG Xuerui <kernel@...0n.name>,
Masami Hiramatsu <mhiramat@...nel.org>,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 2/4] LoongArch: Add kprobe support
Hi, Jinyang
On 12/09/2022 11:31 AM, Jinyang He wrote:
> On 2022-12-09 10:22, Huacai Chen wrote:
>
>> cas
>>
>> On Thu, Dec 8, 2022 at 9:41 PM Tiezhu Yang <yangtiezhu@...ngson.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@...ngson.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 | 332
>>> +++++++++++++++++++++++++++++++++++
>>> arch/loongarch/kernel/traps.c | 13 +-
>>> arch/loongarch/mm/fault.c | 3 +
>>> 7 files changed, 421 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 19cf692..e3f2378 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..aadfc9ae
>>> --- /dev/null
>>> +++ b/arch/loongarch/kernel/kprobes.c
>>> @@ -0,0 +1,332 @@
>>> +// 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)
>> Use insns_not_supported for short.
>>
>>> +{
>>> + 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_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)
>> Use insns_not_simulated for short.
>>> +{
>>> + 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;
>>> + }
>>> +
>>> + 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_are_not_simulated(p, regs)) {
>>> + kcb->kprobe_status = KPROBE_HIT_SS;
>>> + regs->csr_era = (unsigned long)&p->ainsn.insn[0];
>>> + } else {
>>> + kcb->kprobe_status = KPROBE_HIT_SSDONE;
>>> + if (p->post_handler)
>>> + p->post_handler(p, regs, 0);
>>> + reset_current_kprobe();
>>> + preempt_enable_no_resched();
>>> + }
>>> +}
>>> +NOKPROBE_SYMBOL(setup_singlestep);
>>> +
>>> +static bool reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
>>> + struct kprobe_ctlblk *kcb)
>>> +{
>>> + switch (kcb->kprobe_status) {
>>> + case KPROBE_HIT_SSDONE:
>>> + case KPROBE_HIT_ACTIVE:
>>> + kprobes_inc_nmissed_count(p);
>>> + setup_singlestep(p, regs, kcb, 1);
>>> + break;
>>> + case KPROBE_HIT_SS:
>>> + case KPROBE_REENTER:
>>> + pr_warn("Failed to recover from reentered kprobes.\n");
>>> + dump_kprobe(p);
>>> + BUG();
>>> + break;
>>> + default:
>>> + WARN_ON(1);
>>> + return false;
>>> + }
>>> +
>>> + return true;
>>> +}
>>> +NOKPROBE_SYMBOL(reenter_kprobe);
>>> +
>>> +bool kprobe_breakpoint_handler(struct pt_regs *regs)
>>> +{
>>> + struct kprobe_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 */
>>> + kcb->kprobe_status = KPROBE_HIT_SSDONE;
>>> + if (cur->post_handler)
>>> + cur->post_handler(cur, regs, 0);
>> I'm not very familiar, but I think you should set KPROBE_HIT_SSDONE
>> only when post_handler is not NULL.
>>
>>> +
>>> + 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();
>>> + }
>> I think the KPROBE_REENTER case also needs to enable preemption.
>>
>>> +
>>> + 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;
>> Does here need to enable preemption too?
>>
>>> + }
>>> + 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);
>>> + }
>>> +
>> Why? we already got bcode at the beginning.
>
> Hi, Huacai,
>
>
> I think it is because kprobe_breakpoint_handler() may deal with that
> case other cpu may remove its breakpoint. In that case, normally we can
> exit this break exception and go on. But if
> the orignal instruction is_break_ins(), we will trigger trap aggain. So
> it is better to avoid double traps and let it go ahead when
> kprobe_breakpoint_handler() returns.
Perhaps it is not described here as avoiding the trap twice, but rather
that if we don't re-fetch the bcode when the original instruction
`break` will go to the default branch regardless of what the bcode of
the original instruction is (since the bcode is BRK_KPROBE_BP at this
point). IMHO, so we re-get the bcode to get the original instruction
`break` is the correct bcode to ensure that it goes to the appropriate
case branch.
Thanks,
Youling.
> Differnt from many other archs, e.g. riscv, we switch bcode to decide
> which handlers should go on. Thus, we need get bcode again.
>
> Thanks,
>
> Jinyang
>
>
>>> 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
>>>
>>>
>
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