Messages in this thread Patch in this message | | | From | Tiezhu Yang <> | Subject | [PATCH v2 2/5] LoongArch: Add kprobe support | Date | Wed, 28 Sep 2022 08:50:06 +0800 |
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Kprobes allows you to trap at almost any kernel address and execute a callback function, this commit adds kprobe support for LoongArch.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> --- arch/loongarch/Kconfig | 1 + arch/loongarch/include/asm/inst.h | 12 ++ arch/loongarch/include/asm/kprobes.h | 44 +++++ arch/loongarch/kernel/Makefile | 2 + arch/loongarch/kernel/kprobes.c | 312 +++++++++++++++++++++++++++++++++++ arch/loongarch/mm/fault.c | 3 + 6 files changed, 374 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 be8389f..8debd70 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -94,6 +94,7 @@ 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 93d5cd4..fc8879b 100644 --- a/arch/loongarch/include/asm/inst.h +++ b/arch/loongarch/include/asm/inst.h @@ -21,6 +21,10 @@ #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, @@ -38,6 +42,8 @@ enum reg1i20_op { enum reg1i21_op { beqz_op = 0x10, bnez_op = 0x11, + bceqz_op = 0x48000000, + bcnez_op = 0x48000100, }; enum reg2_op { @@ -167,6 +173,11 @@ 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; @@ -252,6 +263,7 @@ 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..afcf254 --- /dev/null +++ b/arch/loongarch/include/asm/kprobes.h @@ -0,0 +1,44 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#ifndef __ASM_LOONGARCH_KPROBES_H +#define __ASM_LOONGARCH_KPROBES_H + +#include <asm-generic/kprobes.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 { } 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 5358144..ff98d8a 100644 --- a/arch/loongarch/kernel/Makefile +++ b/arch/loongarch/kernel/Makefile @@ -33,4 +33,6 @@ 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..c11f6e0 --- /dev/null +++ b/arch/loongarch/kernel/kprobes.c @@ -0,0 +1,312 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/kprobes.h> +#include <linux/kdebug.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: + case bcnez_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; +} +NOKPROBE_SYMBOL(arch_arm_kprobe); + +/* Remove breakpoint from text */ +void arch_disarm_kprobe(struct kprobe *p) +{ + *p->addr = p->opcode; +} +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; + 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(); + } +} +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_pre_handler(struct pt_regs *regs) +{ + struct kprobe *p, *cur_kprobe; + struct kprobe_ctlblk *kcb; + unsigned long addr = instruction_pointer(regs); + + 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(); + } + 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. + */ + return false; +} +NOKPROBE_SYMBOL(kprobe_pre_handler); + +static bool kprobe_post_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); + return true; + } + + /* 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(); + + return true; +} +NOKPROBE_SYMBOL(kprobe_post_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(); + } + + 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_pre_handler(args->regs)) + ret = NOTIFY_STOP; + break; + case DIE_SSTEPBP: + if (kprobe_post_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..5882f17 100644 --- a/arch/loongarch/mm/fault.c +++ b/arch/loongarch/mm/fault.c @@ -253,6 +253,9 @@ 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)) + return; + /* Enable interrupt if enabled in parent context */ if (likely(regs->csr_prmd & CSR_PRMD_PIE)) local_irq_enable(); -- 2.1.0
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