// SPDX-License-Identifier: GPL-2.0-or-later /* * Kernel Probes (KProbes) * * Copyright (C) IBM Corporation, 2002, 2004 * * 2002-Oct Created by Vamsi Krishna S Kernel * Probes initial implementation ( includes contributions from * Rusty Russell). * 2004-July Suparna Bhattacharya added jumper probes * interface to access function arguments. * 2004-Oct Jim Keniston and Prasanna S Panchamukhi * adapted for x86_64 from i386. * 2005-Mar Roland McGrath * Fixed to handle %rip-relative addressing mode correctly. * 2005-May Hien Nguyen , Jim Keniston * and Prasanna S Panchamukhi * added function-return probes. * 2005-May Rusty Lynch * Added function return probes functionality * 2006-Feb Masami Hiramatsu added * kprobe-booster and kretprobe-booster for i386. * 2007-Dec Masami Hiramatsu added kprobe-booster * and kretprobe-booster for x86-64 * 2007-Dec Masami Hiramatsu , Arjan van de Ven * and Jim Keniston * unified x86 kprobes code. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "common.h" DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); #define stack_addr(regs) ((unsigned long *)regs->sp) #define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\ (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \ (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \ (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \ (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \ << (row % 32)) /* * Undefined/reserved opcodes, conditional jump, Opcode Extension * Groups, and some special opcodes can not boost. * This is non-const and volatile to keep gcc from statically * optimizing it out, as variable_test_bit makes gcc think only * *(unsigned long*) is used. */ static volatile u32 twobyte_is_boostable[256 / 32] = { /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ /* ---------------------------------------------- */ W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */ W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1) , /* 10 */ W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */ W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */ W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */ W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */ W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */ W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */ W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */ W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */ W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */ W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */ W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */ W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */ W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */ W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */ /* ----------------------------------------------- */ /* 0 1 2 3 4 5 6 7 8 9 a b c d e f */ }; #undef W struct kretprobe_blackpoint kretprobe_blacklist[] = { {"__switch_to", }, /* This function switches only current task, but doesn't switch kernel stack.*/ {NULL, NULL} /* Terminator */ }; const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist); static nokprobe_inline void __synthesize_relative_insn(void *dest, void *from, void *to, u8 op) { struct __arch_relative_insn { u8 op; s32 raddr; } __packed *insn; insn = (struct __arch_relative_insn *)dest; insn->raddr = (s32)((long)(to) - ((long)(from) + 5)); insn->op = op; } /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/ void synthesize_reljump(void *dest, void *from, void *to) { __synthesize_relative_insn(dest, from, to, RELATIVEJUMP_OPCODE); } NOKPROBE_SYMBOL(synthesize_reljump); /* Insert a call instruction at address 'from', which calls address 'to'.*/ void synthesize_relcall(void *dest, void *from, void *to) { __synthesize_relative_insn(dest, from, to, RELATIVECALL_OPCODE); } NOKPROBE_SYMBOL(synthesize_relcall); /* * Skip the prefixes of the instruction. */ static kprobe_opcode_t *skip_prefixes(kprobe_opcode_t *insn) { insn_attr_t attr; attr = inat_get_opcode_attribute((insn_byte_t)*insn); while (inat_is_legacy_prefix(attr)) { insn++; attr = inat_get_opcode_attribute((insn_byte_t)*insn); } #ifdef CONFIG_X86_64 if (inat_is_rex_prefix(attr)) insn++; #endif return insn; } NOKPROBE_SYMBOL(skip_prefixes); /* * Returns non-zero if INSN is boostable. * RIP relative instructions are adjusted at copying time in 64 bits mode */ int can_boost(struct insn *insn, void *addr) { kprobe_opcode_t opcode; if (search_exception_tables((unsigned long)addr)) return 0; /* Page fault may occur on this address. */ /* 2nd-byte opcode */ if (insn->opcode.nbytes == 2) return test_bit(insn->opcode.bytes[1], (unsigned long *)twobyte_is_boostable); if (insn->opcode.nbytes != 1) return 0; /* Can't boost Address-size override prefix */ if (unlikely(inat_is_address_size_prefix(insn->attr))) return 0; opcode = insn->opcode.bytes[0]; switch (opcode & 0xf0) { case 0x60: /* can't boost "bound" */ return (opcode != 0x62); case 0x70: return 0; /* can't boost conditional jump */ case 0x90: return opcode != 0x9a; /* can't boost call far */ case 0xc0: /* can't boost software-interruptions */ return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf; case 0xd0: /* can boost AA* and XLAT */ return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7); case 0xe0: /* can boost in/out and absolute jmps */ return ((opcode & 0x04) || opcode == 0xea); case 0xf0: /* clear and set flags are boostable */ return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe)); default: /* CS override prefix and call are not boostable */ return (opcode != 0x2e && opcode != 0x9a); } } static unsigned long __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr) { struct kprobe *kp; unsigned long faddr; kp = get_kprobe((void *)addr); faddr = ftrace_location(addr); /* * Addresses inside the ftrace location are refused by * arch_check_ftrace_location(). Something went terribly wrong * if such an address is checked here. */ if (WARN_ON(faddr && faddr != addr)) return 0UL; /* * Use the current code if it is not modified by Kprobe * and it cannot be modified by ftrace. */ if (!kp && !faddr) return addr; /* * Basically, kp->ainsn.insn has an original instruction. * However, RIP-relative instruction can not do single-stepping * at different place, __copy_instruction() tweaks the displacement of * that instruction. In that case, we can't recover the instruction * from the kp->ainsn.insn. * * On the other hand, in case on normal Kprobe, kp->opcode has a copy * of the first byte of the probed instruction, which is overwritten * by int3. And the instruction at kp->addr is not modified by kprobes * except for the first byte, we can recover the original instruction * from it and kp->opcode. * * In case of Kprobes using ftrace, we do not have a copy of * the original instruction. In fact, the ftrace location might * be modified at anytime and even could be in an inconsistent state. * Fortunately, we know that the original code is the ideal 5-byte * long NOP. */ if (probe_kernel_read(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t))) return 0UL; if (faddr) memcpy(buf, ideal_nops[NOP_ATOMIC5], 5); else buf[0] = kp->opcode; return (unsigned long)buf; } /* * Recover the probed instruction at addr for further analysis. * Caller must lock kprobes by kprobe_mutex, or disable preemption * for preventing to release referencing kprobes. * Returns zero if the instruction can not get recovered (or access failed). */ unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr) { unsigned long __addr; __addr = __recover_optprobed_insn(buf, addr); if (__addr != addr) return __addr; return __recover_probed_insn(buf, addr); } /* Check if paddr is at an instruction boundary */ static int can_probe(unsigned long paddr) { unsigned long addr, __addr, offset = 0; struct insn insn; kprobe_opcode_t buf[MAX_INSN_SIZE]; if (!kallsyms_lookup_size_offset(paddr, NULL, &offset)) return 0; /* Decode instructions */ addr = paddr - offset; while (addr < paddr) { /* * Check if the instruction has been modified by another * kprobe, in which case we replace the breakpoint by the * original instruction in our buffer. * Also, jump optimization will change the breakpoint to * relative-jump. Since the relative-jump itself is * normally used, we just go through if there is no kprobe. */ __addr = recover_probed_instruction(buf, addr); if (!__addr) return 0; kernel_insn_init(&insn, (void *)__addr, MAX_INSN_SIZE); insn_get_length(&insn); /* * Another debugging subsystem might insert this breakpoint. * In that case, we can't recover it. */ if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) return 0; addr += insn.length; } return (addr == paddr); } /* * Returns non-zero if opcode modifies the interrupt flag. */ static int is_IF_modifier(kprobe_opcode_t *insn) { /* Skip prefixes */ insn = skip_prefixes(insn); switch (*insn) { case 0xfa: /* cli */ case 0xfb: /* sti */ case 0xcf: /* iret/iretd */ case 0x9d: /* popf/popfd */ return 1; } return 0; } /* * Copy an instruction with recovering modified instruction by kprobes * and adjust the displacement if the instruction uses the %rip-relative * addressing mode. Note that since @real will be the final place of copied * instruction, displacement must be adjust by @real, not @dest. * This returns the length of copied instruction, or 0 if it has an error. */ int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn) { kprobe_opcode_t buf[MAX_INSN_SIZE]; unsigned long recovered_insn = recover_probed_instruction(buf, (unsigned long)src); if (!recovered_insn || !insn) return 0; /* This can access kernel text if given address is not recovered */ if (probe_kernel_read(dest, (void *)recovered_insn, MAX_INSN_SIZE)) return 0; kernel_insn_init(insn, dest, MAX_INSN_SIZE); insn_get_length(insn); /* Another subsystem puts a breakpoint, failed to recover */ if (insn->opcode.bytes[0] == BREAKPOINT_INSTRUCTION) return 0; /* We should not singlestep on the exception masking instructions */ if (insn_masking_exception(insn)) return 0; #ifdef CONFIG_X86_64 /* Only x86_64 has RIP relative instructions */ if (insn_rip_relative(insn)) { s64 newdisp; u8 *disp; /* * The copied instruction uses the %rip-relative addressing * mode. Adjust the displacement for the difference between * the original location of this instruction and the location * of the copy that will actually be run. The tricky bit here * is making sure that the sign extension happens correctly in * this calculation, since we need a signed 32-bit result to * be sign-extended to 64 bits when it's added to the %rip * value and yield the same 64-bit result that the sign- * extension of the original signed 32-bit displacement would * have given. */ newdisp = (u8 *) src + (s64) insn->displacement.value - (u8 *) real; if ((s64) (s32) newdisp != newdisp) { pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp); return 0; } disp = (u8 *) dest + insn_offset_displacement(insn); *(s32 *) disp = (s32) newdisp; } #endif return insn->length; } /* Prepare reljump right after instruction to boost */ static int prepare_boost(kprobe_opcode_t *buf, struct kprobe *p, struct insn *insn) { int len = insn->length; if (can_boost(insn, p->addr) && MAX_INSN_SIZE - len >= RELATIVEJUMP_SIZE) { /* * These instructions can be executed directly if it * jumps back to correct address. */ synthesize_reljump(buf + len, p->ainsn.insn + len, p->addr + insn->length); len += RELATIVEJUMP_SIZE; p->ainsn.boostable = true; } else { p->ainsn.boostable = false; } return len; } /* Make page to RO mode when allocate it */ void *alloc_insn_page(void) { void *page; page = module_alloc(PAGE_SIZE); if (!page) return NULL; set_vm_flush_reset_perms(page); /* * First make the page read-only, and only then make it executable to * prevent it from being W+X in between. */ set_memory_ro((unsigned long)page, 1); /* * TODO: Once additional kernel code protection mechanisms are set, ensure * that the page was not maliciously altered and it is still zeroed. */ set_memory_x((unsigned long)page, 1); return page; } /* Recover page to RW mode before releasing it */ void free_insn_page(void *page) { module_memfree(page); } static int arch_copy_kprobe(struct kprobe *p) { struct insn insn; kprobe_opcode_t buf[MAX_INSN_SIZE]; int len; /* Copy an instruction with recovering if other optprobe modifies it.*/ len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn); if (!len) return -EINVAL; /* * __copy_instruction can modify the displacement of the instruction, * but it doesn't affect boostable check. */ len = prepare_boost(buf, p, &insn); /* Check whether the instruction modifies Interrupt Flag or not */ p->ainsn.if_modifier = is_IF_modifier(buf); /* Also, displacement change doesn't affect the first byte */ p->opcode = buf[0]; /* OK, write back the instruction(s) into ROX insn buffer */ text_poke(p->ainsn.insn, buf, len); return 0; } int arch_prepare_kprobe(struct kprobe *p) { int ret; if (alternatives_text_reserved(p->addr, p->addr)) return -EINVAL; if (!can_probe((unsigned long)p->addr)) return -EILSEQ; /* insn: must be on special executable page on x86. */ p->ainsn.insn = get_insn_slot(); if (!p->ainsn.insn) return -ENOMEM; ret = arch_copy_kprobe(p); if (ret) { free_insn_slot(p->ainsn.insn, 0); p->ainsn.insn = NULL; } return ret; } void arch_arm_kprobe(struct kprobe *p) { text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1); } void arch_disarm_kprobe(struct kprobe *p) { text_poke(p->addr, &p->opcode, 1); } void arch_remove_kprobe(struct kprobe *p) { if (p->ainsn.insn) { free_insn_slot(p->ainsn.insn, p->ainsn.boostable); p->ainsn.insn = NULL; } } static nokprobe_inline void save_previous_kprobe(struct kprobe_ctlblk *kcb) { kcb->prev_kprobe.kp = kprobe_running(); kcb->prev_kprobe.status = kcb->kprobe_status; kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags; kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags; } static nokprobe_inline 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_old_flags = kcb->prev_kprobe.old_flags; kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags; } static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { __this_cpu_write(current_kprobe, p); kcb->kprobe_saved_flags = kcb->kprobe_old_flags = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF)); if (p->ainsn.if_modifier) kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF; } static nokprobe_inline void clear_btf(void) { if (test_thread_flag(TIF_BLOCKSTEP)) { unsigned long debugctl = get_debugctlmsr(); debugctl &= ~DEBUGCTLMSR_BTF; update_debugctlmsr(debugctl); } } static nokprobe_inline void restore_btf(void) { if (test_thread_flag(TIF_BLOCKSTEP)) { unsigned long debugctl = get_debugctlmsr(); debugctl |= DEBUGCTLMSR_BTF; update_debugctlmsr(debugctl); } } void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) { unsigned long *sara = stack_addr(regs); ri->ret_addr = (kprobe_opcode_t *) *sara; ri->fp = sara; /* Replace the return addr with trampoline addr */ *sara = (unsigned long) &kretprobe_trampoline; } NOKPROBE_SYMBOL(arch_prepare_kretprobe); static void setup_singlestep(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb, int reenter) { if (setup_detour_execution(p, regs, reenter)) return; #if !defined(CONFIG_PREEMPT) if (p->ainsn.boostable && !p->post_handler) { /* Boost up -- we can execute copied instructions directly */ if (!reenter) reset_current_kprobe(); /* * Reentering boosted probe doesn't reset current_kprobe, * nor set current_kprobe, because it doesn't use single * stepping. */ regs->ip = (unsigned long)p->ainsn.insn; return; } #endif if (reenter) { save_previous_kprobe(kcb); set_current_kprobe(p, regs, kcb); kcb->kprobe_status = KPROBE_REENTER; } else kcb->kprobe_status = KPROBE_HIT_SS; /* Prepare real single stepping */ clear_btf(); regs->flags |= X86_EFLAGS_TF; regs->flags &= ~X86_EFLAGS_IF; /* single step inline if the instruction is an int3 */ if (p->opcode == BREAKPOINT_INSTRUCTION) regs->ip = (unsigned long)p->addr; else regs->ip = (unsigned long)p->ainsn.insn; } NOKPROBE_SYMBOL(setup_singlestep); /* * We have reentered the kprobe_handler(), since another probe was hit while * within the handler. We save the original kprobes variables and just single * step on the instruction of the new probe without calling any user handlers. */ static int 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: case KPROBE_HIT_SS: kprobes_inc_nmissed_count(p); setup_singlestep(p, regs, kcb, 1); break; case KPROBE_REENTER: /* A probe has been hit in the codepath leading up to, or just * after, single-stepping of a probed instruction. This entire * codepath should strictly reside in .kprobes.text section. * Raise a BUG or we'll continue in an endless reentering loop * and eventually a stack overflow. */ pr_err("Unrecoverable kprobe detected.\n"); dump_kprobe(p); BUG(); default: /* impossible cases */ WARN_ON(1); return 0; } return 1; } NOKPROBE_SYMBOL(reenter_kprobe); /* * Interrupts are disabled on entry as trap3 is an interrupt gate and they * remain disabled throughout this function. */ int kprobe_int3_handler(struct pt_regs *regs) { kprobe_opcode_t *addr; struct kprobe *p; struct kprobe_ctlblk *kcb; if (user_mode(regs)) return 0; addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t)); /* * We don't want to be preempted for the entire duration of kprobe * processing. Since int3 and debug trap disables irqs and we clear * IF while singlestepping, it must be no preemptible. */ kcb = get_kprobe_ctlblk(); p = get_kprobe(addr); if (p) { if (kprobe_running()) { if (reenter_kprobe(p, regs, kcb)) return 1; } else { 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, that means * user handler setup registers to exit to another * instruction, we must skip the single stepping. */ if (!p->pre_handler || !p->pre_handler(p, regs)) setup_singlestep(p, regs, kcb, 0); else reset_current_kprobe(); return 1; } } else if (*addr != BREAKPOINT_INSTRUCTION) { /* * 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. * Back up over the (now missing) int3 and run * the original instruction. */ regs->ip = (unsigned long)addr; return 1; } /* else: not a kprobe fault; let the kernel handle it */ return 0; } NOKPROBE_SYMBOL(kprobe_int3_handler); /* * When a retprobed function returns, this code saves registers and * calls trampoline_handler() runs, which calls the kretprobe's handler. */ asm( ".text\n" ".global kretprobe_trampoline\n" ".type kretprobe_trampoline, @function\n" "kretprobe_trampoline:\n" /* We don't bother saving the ss register */ #ifdef CONFIG_X86_64 " pushq %rsp\n" " pushfq\n" SAVE_REGS_STRING " movq %rsp, %rdi\n" " call trampoline_handler\n" /* Replace saved sp with true return address. */ " movq %rax, 19*8(%rsp)\n" RESTORE_REGS_STRING " popfq\n" #else " pushl %esp\n" " pushfl\n" SAVE_REGS_STRING " movl %esp, %eax\n" " call trampoline_handler\n" /* Replace saved sp with true return address. */ " movl %eax, 15*4(%esp)\n" RESTORE_REGS_STRING " popfl\n" #endif " ret\n" ".size kretprobe_trampoline, .-kretprobe_trampoline\n" ); NOKPROBE_SYMBOL(kretprobe_trampoline); STACK_FRAME_NON_STANDARD(kretprobe_trampoline); static struct kprobe kretprobe_kprobe = { .addr = (void *)kretprobe_trampoline, }; /* * Called from kretprobe_trampoline */ __used __visible void *trampoline_handler(struct pt_regs *regs) { struct kprobe_ctlblk *kcb; struct kretprobe_instance *ri = NULL; struct hlist_head *head, empty_rp; struct hlist_node *tmp; unsigned long flags, orig_ret_address = 0; unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline; kprobe_opcode_t *correct_ret_addr = NULL; void *frame_pointer; bool skipped = false; preempt_disable(); /* * Set a dummy kprobe for avoiding kretprobe recursion. * Since kretprobe never run in kprobe handler, kprobe must not * be running at this point. */ kcb = get_kprobe_ctlblk(); __this_cpu_write(current_kprobe, &kretprobe_kprobe); kcb->kprobe_status = KPROBE_HIT_ACTIVE; INIT_HLIST_HEAD(&empty_rp); kretprobe_hash_lock(current, &head, &flags); /* fixup registers */ regs->cs = __KERNEL_CS; #ifdef CONFIG_X86_32 regs->cs |= get_kernel_rpl(); regs->gs = 0; #endif /* We use pt_regs->sp for return address holder. */ frame_pointer = ®s->sp; regs->ip = trampoline_address; regs->orig_ax = ~0UL; /* * It is possible to have multiple instances associated with a given * task either because multiple functions in the call path have * return probes installed on them, and/or more than one * return probe was registered for a target function. * * We can handle this because: * - instances are always pushed into the head of the list * - when multiple return probes are registered for the same * function, the (chronologically) first instance's ret_addr * will be the real return address, and all the rest will * point to kretprobe_trampoline. */ hlist_for_each_entry(ri, head, hlist) { if (ri->task != current) /* another task is sharing our hash bucket */ continue; /* * Return probes must be pushed on this hash list correct * order (same as return order) so that it can be popped * correctly. However, if we find it is pushed it incorrect * order, this means we find a function which should not be * probed, because the wrong order entry is pushed on the * path of processing other kretprobe itself. */ if (ri->fp != frame_pointer) { if (!skipped) pr_warn("kretprobe is stacked incorrectly. Trying to fixup.\n"); skipped = true; continue; } orig_ret_address = (unsigned long)ri->ret_addr; if (skipped) pr_warn("%ps must be blacklisted because of incorrect kretprobe order\n", ri->rp->kp.addr); if (orig_ret_address != trampoline_address) /* * This is the real return address. Any other * instances associated with this task are for * other calls deeper on the call stack */ break; } kretprobe_assert(ri, orig_ret_address, trampoline_address); correct_ret_addr = ri->ret_addr; hlist_for_each_entry_safe(ri, tmp, head, hlist) { if (ri->task != current) /* another task is sharing our hash bucket */ continue; if (ri->fp != frame_pointer) continue; orig_ret_address = (unsigned long)ri->ret_addr; if (ri->rp && ri->rp->handler) { __this_cpu_write(current_kprobe, &ri->rp->kp); ri->ret_addr = correct_ret_addr; ri->rp->handler(ri, regs); __this_cpu_write(current_kprobe, &kretprobe_kprobe); } recycle_rp_inst(ri, &empty_rp); if (orig_ret_address != trampoline_address) /* * This is the real return address. Any other * instances associated with this task are for * other calls deeper on the call stack */ break; } kretprobe_hash_unlock(current, &flags); __this_cpu_write(current_kprobe, NULL); preempt_enable(); hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { hlist_del(&ri->hlist); kfree(ri); } return (void *)orig_ret_address; } NOKPROBE_SYMBOL(trampoline_handler); /* * Called after single-stepping. p->addr is the address of the * instruction whose first byte has been replaced by the "int 3" * instruction. To avoid the SMP problems that can occur when we * temporarily put back the original opcode to single-step, we * single-stepped a copy of the instruction. The address of this * copy is p->ainsn.insn. * * This function prepares to return from the post-single-step * interrupt. We have to fix up the stack as follows: * * 0) Except in the case of absolute or indirect jump or call instructions, * the new ip is relative to the copied instruction. We need to make * it relative to the original instruction. * * 1) If the single-stepped instruction was pushfl, then the TF and IF * flags are set in the just-pushed flags, and may need to be cleared. * * 2) If the single-stepped instruction was a call, the return address * that is atop the stack is the address following the copied instruction. * We need to make it the address following the original instruction. * * If this is the first time we've single-stepped the instruction at * this probepoint, and the instruction is boostable, boost it: add a * jump instruction after the copied instruction, that jumps to the next * instruction after the probepoint. */ static void resume_execution(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { unsigned long *tos = stack_addr(regs); unsigned long copy_ip = (unsigned long)p->ainsn.insn; unsigned long orig_ip = (unsigned long)p->addr; kprobe_opcode_t *insn = p->ainsn.insn; /* Skip prefixes */ insn = skip_prefixes(insn); regs->flags &= ~X86_EFLAGS_TF; switch (*insn) { case 0x9c: /* pushfl */ *tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF); *tos |= kcb->kprobe_old_flags; break; case 0xc2: /* iret/ret/lret */ case 0xc3: case 0xca: case 0xcb: case 0xcf: case 0xea: /* jmp absolute -- ip is correct */ /* ip is already adjusted, no more changes required */ p->ainsn.boostable = true; goto no_change; case 0xe8: /* call relative - Fix return addr */ *tos = orig_ip + (*tos - copy_ip); break; #ifdef CONFIG_X86_32 case 0x9a: /* call absolute -- same as call absolute, indirect */ *tos = orig_ip + (*tos - copy_ip); goto no_change; #endif case 0xff: if ((insn[1] & 0x30) == 0x10) { /* * call absolute, indirect * Fix return addr; ip is correct. * But this is not boostable */ *tos = orig_ip + (*tos - copy_ip); goto no_change; } else if (((insn[1] & 0x31) == 0x20) || ((insn[1] & 0x31) == 0x21)) { /* * jmp near and far, absolute indirect * ip is correct. And this is boostable */ p->ainsn.boostable = true; goto no_change; } default: break; } regs->ip += orig_ip - copy_ip; no_change: restore_btf(); } NOKPROBE_SYMBOL(resume_execution); /* * Interrupts are disabled on entry as trap1 is an interrupt gate and they * remain disabled throughout this function. */ int kprobe_debug_handler(struct pt_regs *regs) { struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); if (!cur) return 0; resume_execution(cur, regs, kcb); regs->flags |= kcb->kprobe_saved_flags; if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { kcb->kprobe_status = KPROBE_HIT_SSDONE; cur->post_handler(cur, regs, 0); } /* Restore back the original saved kprobes variables and continue. */ if (kcb->kprobe_status == KPROBE_REENTER) { restore_previous_kprobe(kcb); goto out; } reset_current_kprobe(); out: /* * if somebody else is singlestepping across a probe point, flags * will have TF set, in which case, continue the remaining processing * of do_debug, as if this is not a probe hit. */ if (regs->flags & X86_EFLAGS_TF) return 0; return 1; } NOKPROBE_SYMBOL(kprobe_debug_handler); int kprobe_fault_handler(struct pt_regs *regs, int trapnr) { struct kprobe *cur = kprobe_running(); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) { /* This must happen on single-stepping */ WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS && kcb->kprobe_status != 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->ip = (unsigned long)cur->addr; /* * Trap flag (TF) has been set here because this fault * happened where the single stepping will be done. * So clear it by resetting the current kprobe: */ regs->flags &= ~X86_EFLAGS_TF; /* * If the TF flag was set before the kprobe hit, * don't touch it: */ regs->flags |= kcb->kprobe_old_flags; if (kcb->kprobe_status == KPROBE_REENTER) restore_previous_kprobe(kcb); else reset_current_kprobe(); } else if (kcb->kprobe_status == KPROBE_HIT_ACTIVE || kcb->kprobe_status == KPROBE_HIT_SSDONE) { /* * We increment the nmissed count for accounting, * we can also use npre/npostfault count for accounting * these specific fault cases. */ kprobes_inc_nmissed_count(cur); /* * We come here because instructions in the pre/post * handler caused the page_fault, this could happen * if handler tries to access user space by * copy_from_user(), get_user() etc. Let the * user-specified handler try to fix it first. */ if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) return 1; } return 0; } NOKPROBE_SYMBOL(kprobe_fault_handler); int __init arch_populate_kprobe_blacklist(void) { int ret; ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start, (unsigned long)__irqentry_text_end); if (ret) return ret; return kprobe_add_area_blacklist((unsigned long)__entry_text_start, (unsigned long)__entry_text_end); } int __init arch_init_kprobes(void) { return 0; } int arch_trampoline_kprobe(struct kprobe *p) { return 0; }