/* * Kernel Probes (KProbes) * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * 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 void jprobe_return_end(void); DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); #define stack_addr(regs) ((unsigned long *)kernel_stack_pointer(regs)) #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. */ static const 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, 0) , /* 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 void __kprobes __synthesize_relative_insn(void *from, void *to, u8 op) { struct __arch_relative_insn { u8 op; s32 raddr; } __attribute__((packed)) *insn; insn = (struct __arch_relative_insn *)from; insn->raddr = (s32)((long)(to) - ((long)(from) + 5)); insn->op = op; } /* Insert a jump instruction at address 'from', which jumps to address 'to'.*/ static void __kprobes synthesize_reljump(void *from, void *to) { __synthesize_relative_insn(from, to, RELATIVEJUMP_OPCODE); } /* * Skip the prefixes of the instruction. */ static kprobe_opcode_t *__kprobes 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; } /* * Returns non-zero if opcode is boostable. * RIP relative instructions are adjusted at copying time in 64 bits mode */ static int __kprobes can_boost(kprobe_opcode_t *opcodes) { kprobe_opcode_t opcode; kprobe_opcode_t *orig_opcodes = opcodes; if (search_exception_tables((unsigned long)opcodes)) return 0; /* Page fault may occur on this address. */ retry: if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1) return 0; opcode = *(opcodes++); /* 2nd-byte opcode */ if (opcode == 0x0f) { if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1) return 0; return test_bit(*opcodes, (unsigned long *)twobyte_is_boostable); } switch (opcode & 0xf0) { #ifdef CONFIG_X86_64 case 0x40: goto retry; /* REX prefix is boostable */ #endif case 0x60: if (0x63 < opcode && opcode < 0x67) goto retry; /* prefixes */ /* can't boost Address-size override and bound */ return (opcode != 0x62 && opcode != 0x67); case 0x70: return 0; /* can't boost conditional jump */ 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: if ((opcode & 0x0c) == 0 && opcode != 0xf1) goto retry; /* lock/rep(ne) prefix */ /* clear and set flags are boostable */ return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe)); default: /* segment override prefixes are boostable */ if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e) goto retry; /* prefixes */ /* CS override prefix and call are not boostable */ return (opcode != 0x2e && opcode != 0x9a); } } /* Recover the probed instruction at addr for further analysis. */ static int recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr) { struct kprobe *kp; kp = get_kprobe((void *)addr); if (!kp) return -EINVAL; /* * 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, 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. */ memcpy(buf, kp->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); buf[0] = kp->opcode; return 0; } /* Check if paddr is at an instruction boundary */ static int __kprobes can_probe(unsigned long paddr) { int ret; unsigned long 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) { kernel_insn_init(&insn, (void *)addr); insn_get_opcode(&insn); /* * Check if the instruction has been modified by another * kprobe, in which case we replace the breakpoint by the * original instruction in our buffer. */ if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) { ret = recover_probed_instruction(buf, addr); if (ret) /* * Another debugging subsystem might insert * this breakpoint. In that case, we can't * recover it. */ return 0; kernel_insn_init(&insn, buf); } insn_get_length(&insn); addr += insn.length; } return (addr == paddr); } /* * Returns non-zero if opcode modifies the interrupt flag. */ static int __kprobes 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 and adjust the displacement if the instruction * uses the %rip-relative addressing mode. * If it does, Return the address of the 32-bit displacement word. * If not, return null. * Only applicable to 64-bit x86. */ static int __kprobes __copy_instruction(u8 *dest, u8 *src, int recover) { struct insn insn; int ret; kprobe_opcode_t buf[MAX_INSN_SIZE]; kernel_insn_init(&insn, src); if (recover) { insn_get_opcode(&insn); if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) { ret = recover_probed_instruction(buf, (unsigned long)src); if (ret) return 0; kernel_insn_init(&insn, buf); } } insn_get_length(&insn); memcpy(dest, insn.kaddr, insn.length); #ifdef CONFIG_X86_64 if (insn_rip_relative(&insn)) { s64 newdisp; u8 *disp; kernel_insn_init(&insn, dest); insn_get_displacement(&insn); /* * 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 *) dest; BUG_ON((s64) (s32) newdisp != newdisp); /* Sanity check. */ disp = (u8 *) dest + insn_offset_displacement(&insn); *(s32 *) disp = (s32) newdisp; } #endif return insn.length; } static void __kprobes arch_copy_kprobe(struct kprobe *p) { /* * Copy an instruction without recovering int3, because it will be * put by another subsystem. */ __copy_instruction(p->ainsn.insn, p->addr, 0); if (can_boost(p->addr)) p->ainsn.boostable = 0; else p->ainsn.boostable = -1; p->opcode = *p->addr; } int __kprobes arch_prepare_kprobe(struct kprobe *p) { 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; arch_copy_kprobe(p); return 0; } void __kprobes arch_arm_kprobe(struct kprobe *p) { text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1); } void __kprobes arch_disarm_kprobe(struct kprobe *p) { text_poke(p->addr, &p->opcode, 1); } void __kprobes arch_remove_kprobe(struct kprobe *p) { if (p->ainsn.insn) { free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1)); p->ainsn.insn = NULL; } } static void __kprobes 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 void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) { __get_cpu_var(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 void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { __get_cpu_var(current_kprobe) = p; kcb->kprobe_saved_flags = kcb->kprobe_old_flags = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF)); if (is_IF_modifier(p->ainsn.insn)) kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF; } static void __kprobes clear_btf(void) { if (test_thread_flag(TIF_BLOCKSTEP)) { unsigned long debugctl = get_debugctlmsr(); debugctl &= ~DEBUGCTLMSR_BTF; update_debugctlmsr(debugctl); } } static void __kprobes restore_btf(void) { if (test_thread_flag(TIF_BLOCKSTEP)) { unsigned long debugctl = get_debugctlmsr(); debugctl |= DEBUGCTLMSR_BTF; update_debugctlmsr(debugctl); } } void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) { unsigned long *sara = stack_addr(regs); ri->ret_addr = (kprobe_opcode_t *) *sara; /* Replace the return addr with trampoline addr */ *sara = (unsigned long) &kretprobe_trampoline; } #ifdef CONFIG_OPTPROBES static int __kprobes setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter); #else #define setup_detour_execution(p, regs, reenter) (0) #endif static void __kprobes 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 == 1 && !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; preempt_enable_no_resched(); 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; } /* * 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 __kprobes 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: /* 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. */ printk(KERN_WARNING "Unrecoverable kprobe detected at %p.\n", p->addr); dump_kprobe(p); BUG(); default: /* impossible cases */ WARN_ON(1); return 0; } return 1; } /* * Interrupts are disabled on entry as trap3 is an interrupt gate and they * remain disabled throughout this function. */ static int __kprobes kprobe_handler(struct pt_regs *regs) { kprobe_opcode_t *addr; struct kprobe *p; struct kprobe_ctlblk *kcb; addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t)); /* * We don't want to be preempted for the entire * duration of kprobe processing. We conditionally * re-enable preemption at the end of this function, * and also in reenter_kprobe() and setup_singlestep(). */ preempt_disable(); 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, it prepped * for calling the break_handler below on re-entry * for jprobe processing, so get out doing nothing * more here. */ if (!p->pre_handler || !p->pre_handler(p, regs)) setup_singlestep(p, regs, kcb, 0); 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; preempt_enable_no_resched(); return 1; } else if (kprobe_running()) { p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { setup_singlestep(p, regs, kcb, 0); return 1; } } /* else: not a kprobe fault; let the kernel handle it */ preempt_enable_no_resched(); return 0; } #ifdef CONFIG_X86_64 #define SAVE_REGS_STRING \ /* Skip cs, ip, orig_ax. */ \ " subq $24, %rsp\n" \ " pushq %rdi\n" \ " pushq %rsi\n" \ " pushq %rdx\n" \ " pushq %rcx\n" \ " pushq %rax\n" \ " pushq %r8\n" \ " pushq %r9\n" \ " pushq %r10\n" \ " pushq %r11\n" \ " pushq %rbx\n" \ " pushq %rbp\n" \ " pushq %r12\n" \ " pushq %r13\n" \ " pushq %r14\n" \ " pushq %r15\n" #define RESTORE_REGS_STRING \ " popq %r15\n" \ " popq %r14\n" \ " popq %r13\n" \ " popq %r12\n" \ " popq %rbp\n" \ " popq %rbx\n" \ " popq %r11\n" \ " popq %r10\n" \ " popq %r9\n" \ " popq %r8\n" \ " popq %rax\n" \ " popq %rcx\n" \ " popq %rdx\n" \ " popq %rsi\n" \ " popq %rdi\n" \ /* Skip orig_ax, ip, cs */ \ " addq $24, %rsp\n" #else #define SAVE_REGS_STRING \ /* Skip cs, ip, orig_ax and gs. */ \ " subl $16, %esp\n" \ " pushl %fs\n" \ " pushl %es\n" \ " pushl %ds\n" \ " pushl %eax\n" \ " pushl %ebp\n" \ " pushl %edi\n" \ " pushl %esi\n" \ " pushl %edx\n" \ " pushl %ecx\n" \ " pushl %ebx\n" #define RESTORE_REGS_STRING \ " popl %ebx\n" \ " popl %ecx\n" \ " popl %edx\n" \ " popl %esi\n" \ " popl %edi\n" \ " popl %ebp\n" \ " popl %eax\n" \ /* Skip ds, es, fs, gs, orig_ax, and ip. Note: don't pop cs here*/\ " addl $24, %esp\n" #endif /* * When a retprobed function returns, this code saves registers and * calls trampoline_handler() runs, which calls the kretprobe's handler. */ static void __used __kprobes kretprobe_trampoline_holder(void) { asm volatile ( ".global kretprobe_trampoline\n" "kretprobe_trampoline: \n" #ifdef CONFIG_X86_64 /* We don't bother saving the ss register */ " 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, 152(%rsp)\n" RESTORE_REGS_STRING " popfq\n" #else " pushf\n" SAVE_REGS_STRING " movl %esp, %eax\n" " call trampoline_handler\n" /* Move flags to cs */ " movl 56(%esp), %edx\n" " movl %edx, 52(%esp)\n" /* Replace saved flags with true return address. */ " movl %eax, 56(%esp)\n" RESTORE_REGS_STRING " popf\n" #endif " ret\n"); } /* * Called from kretprobe_trampoline */ static __used __kprobes void *trampoline_handler(struct pt_regs *regs) { struct kretprobe_instance *ri = NULL; struct hlist_head *head, empty_rp; struct hlist_node *node, *tmp; unsigned long flags, orig_ret_address = 0; unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline; kprobe_opcode_t *correct_ret_addr = NULL; INIT_HLIST_HEAD(&empty_rp); kretprobe_hash_lock(current, &head, &flags); /* fixup registers */ #ifdef CONFIG_X86_64 regs->cs = __KERNEL_CS; #else regs->cs = __KERNEL_CS | get_kernel_rpl(); regs->gs = 0; #endif 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_safe(ri, node, tmp, head, hlist) { if (ri->task != current) /* another task is sharing our hash bucket */ continue; orig_ret_address = (unsigned long)ri->ret_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, node, tmp, head, hlist) { if (ri->task != current) /* another task is sharing our hash bucket */ continue; orig_ret_address = (unsigned long)ri->ret_addr; if (ri->rp && ri->rp->handler) { __get_cpu_var(current_kprobe) = &ri->rp->kp; get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; ri->ret_addr = correct_ret_addr; ri->rp->handler(ri, regs); __get_cpu_var(current_kprobe) = NULL; } 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); hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { hlist_del(&ri->hlist); kfree(ri); } return (void *)orig_ret_address; } /* * 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 __kprobes 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 = 1; 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 = 1; goto no_change; } default: break; } if (p->ainsn.boostable == 0) { if ((regs->ip > copy_ip) && (regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) { /* * These instructions can be executed directly if it * jumps back to correct address. */ synthesize_reljump((void *)regs->ip, (void *)orig_ip + (regs->ip - copy_ip)); p->ainsn.boostable = 1; } else { p->ainsn.boostable = -1; } } regs->ip += orig_ip - copy_ip; no_change: restore_btf(); } /* * Interrupts are disabled on entry as trap1 is an interrupt gate and they * remain disabled throughout this function. */ static int __kprobes post_kprobe_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: preempt_enable_no_resched(); /* * 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; } int __kprobes 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->ip = (unsigned long)cur->addr; regs->flags |= kcb->kprobe_old_flags; if (kcb->kprobe_status == KPROBE_REENTER) restore_previous_kprobe(kcb); else reset_current_kprobe(); preempt_enable_no_resched(); break; case KPROBE_HIT_ACTIVE: case 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; /* * In case the user-specified fault handler returned * zero, try to fix up. */ if (fixup_exception(regs)) return 1; /* * fixup routine could not handle it, * Let do_page_fault() fix it. */ break; default: break; } return 0; } /* * Wrapper routine for handling exceptions. */ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data) { struct die_args *args = data; int ret = NOTIFY_DONE; if (args->regs && user_mode_vm(args->regs)) return ret; switch (val) { case DIE_INT3: if (kprobe_handler(args->regs)) ret = NOTIFY_STOP; break; case DIE_DEBUG: if (post_kprobe_handler(args->regs)) { /* * Reset the BS bit in dr6 (pointed by args->err) to * denote completion of processing */ (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP; ret = NOTIFY_STOP; } break; case DIE_GPF: /* * To be potentially processing a kprobe fault and to * trust the result from kprobe_running(), we have * be non-preemptible. */ if (!preemptible() && kprobe_running() && kprobe_fault_handler(args->regs, args->trapnr)) ret = NOTIFY_STOP; break; default: break; } return ret; } int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) { struct jprobe *jp = container_of(p, struct jprobe, kp); unsigned long addr; struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); kcb->jprobe_saved_regs = *regs; kcb->jprobe_saved_sp = stack_addr(regs); addr = (unsigned long)(kcb->jprobe_saved_sp); /* * As Linus pointed out, gcc assumes that the callee * owns the argument space and could overwrite it, e.g. * tailcall optimization. So, to be absolutely safe * we also save and restore enough stack bytes to cover * the argument area. */ memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr, MIN_STACK_SIZE(addr)); regs->flags &= ~X86_EFLAGS_IF; trace_hardirqs_off(); regs->ip = (unsigned long)(jp->entry); return 1; } void __kprobes jprobe_return(void) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); asm volatile ( #ifdef CONFIG_X86_64 " xchg %%rbx,%%rsp \n" #else " xchgl %%ebx,%%esp \n" #endif " int3 \n" " .globl jprobe_return_end\n" " jprobe_return_end: \n" " nop \n"::"b" (kcb->jprobe_saved_sp):"memory"); } int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); u8 *addr = (u8 *) (regs->ip - 1); struct jprobe *jp = container_of(p, struct jprobe, kp); if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) { if (stack_addr(regs) != kcb->jprobe_saved_sp) { struct pt_regs *saved_regs = &kcb->jprobe_saved_regs; printk(KERN_ERR "current sp %p does not match saved sp %p\n", stack_addr(regs), kcb->jprobe_saved_sp); printk(KERN_ERR "Saved registers for jprobe %p\n", jp); show_registers(saved_regs); printk(KERN_ERR "Current registers\n"); show_registers(regs); BUG(); } *regs = kcb->jprobe_saved_regs; memcpy((kprobe_opcode_t *)(kcb->jprobe_saved_sp), kcb->jprobes_stack, MIN_STACK_SIZE(kcb->jprobe_saved_sp)); preempt_enable_no_resched(); return 1; } return 0; } #ifdef CONFIG_OPTPROBES /* Insert a call instruction at address 'from', which calls address 'to'.*/ static void __kprobes synthesize_relcall(void *from, void *to) { __synthesize_relative_insn(from, to, RELATIVECALL_OPCODE); } /* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */ static void __kprobes synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val) { #ifdef CONFIG_X86_64 *addr++ = 0x48; *addr++ = 0xbf; #else *addr++ = 0xb8; #endif *(unsigned long *)addr = val; } static void __used __kprobes kprobes_optinsn_template_holder(void) { asm volatile ( ".global optprobe_template_entry\n" "optprobe_template_entry: \n" #ifdef CONFIG_X86_64 /* We don't bother saving the ss register */ " pushq %rsp\n" " pushfq\n" SAVE_REGS_STRING " movq %rsp, %rsi\n" ".global optprobe_template_val\n" "optprobe_template_val: \n" ASM_NOP5 ASM_NOP5 ".global optprobe_template_call\n" "optprobe_template_call: \n" ASM_NOP5 /* Move flags to rsp */ " movq 144(%rsp), %rdx\n" " movq %rdx, 152(%rsp)\n" RESTORE_REGS_STRING /* Skip flags entry */ " addq $8, %rsp\n" " popfq\n" #else /* CONFIG_X86_32 */ " pushf\n" SAVE_REGS_STRING " movl %esp, %edx\n" ".global optprobe_template_val\n" "optprobe_template_val: \n" ASM_NOP5 ".global optprobe_template_call\n" "optprobe_template_call: \n" ASM_NOP5 RESTORE_REGS_STRING " addl $4, %esp\n" /* skip cs */ " popf\n" #endif ".global optprobe_template_end\n" "optprobe_template_end: \n"); } #define TMPL_MOVE_IDX \ ((long)&optprobe_template_val - (long)&optprobe_template_entry) #define TMPL_CALL_IDX \ ((long)&optprobe_template_call - (long)&optprobe_template_entry) #define TMPL_END_IDX \ ((long)&optprobe_template_end - (long)&optprobe_template_entry) #define INT3_SIZE sizeof(kprobe_opcode_t) /* Optimized kprobe call back function: called from optinsn */ static void __kprobes optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); /* This is possible if op is under delayed unoptimizing */ if (kprobe_disabled(&op->kp)) return; preempt_disable(); if (kprobe_running()) { kprobes_inc_nmissed_count(&op->kp); } else { /* Save skipped registers */ #ifdef CONFIG_X86_64 regs->cs = __KERNEL_CS; #else regs->cs = __KERNEL_CS | get_kernel_rpl(); regs->gs = 0; #endif regs->ip = (unsigned long)op->kp.addr + INT3_SIZE; regs->orig_ax = ~0UL; __get_cpu_var(current_kprobe) = &op->kp; kcb->kprobe_status = KPROBE_HIT_ACTIVE; opt_pre_handler(&op->kp, regs); __get_cpu_var(current_kprobe) = NULL; } preempt_enable_no_resched(); } static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src) { int len = 0, ret; while (len < RELATIVEJUMP_SIZE) { ret = __copy_instruction(dest + len, src + len, 1); if (!ret || !can_boost(dest + len)) return -EINVAL; len += ret; } /* Check whether the address range is reserved */ if (ftrace_text_reserved(src, src + len - 1) || alternatives_text_reserved(src, src + len - 1) || jump_label_text_reserved(src, src + len - 1)) return -EBUSY; return len; } /* Check whether insn is indirect jump */ static int __kprobes insn_is_indirect_jump(struct insn *insn) { return ((insn->opcode.bytes[0] == 0xff && (X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */ insn->opcode.bytes[0] == 0xea); /* Segment based jump */ } /* Check whether insn jumps into specified address range */ static int insn_jump_into_range(struct insn *insn, unsigned long start, int len) { unsigned long target = 0; switch (insn->opcode.bytes[0]) { case 0xe0: /* loopne */ case 0xe1: /* loope */ case 0xe2: /* loop */ case 0xe3: /* jcxz */ case 0xe9: /* near relative jump */ case 0xeb: /* short relative jump */ break; case 0x0f: if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */ break; return 0; default: if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */ break; return 0; } target = (unsigned long)insn->next_byte + insn->immediate.value; return (start <= target && target <= start + len); } /* Decode whole function to ensure any instructions don't jump into target */ static int __kprobes can_optimize(unsigned long paddr) { int ret; unsigned long addr, size = 0, offset = 0; struct insn insn; kprobe_opcode_t buf[MAX_INSN_SIZE]; /* Lookup symbol including addr */ if (!kallsyms_lookup_size_offset(paddr, &size, &offset)) return 0; /* Check there is enough space for a relative jump. */ if (size - offset < RELATIVEJUMP_SIZE) return 0; /* Decode instructions */ addr = paddr - offset; while (addr < paddr - offset + size) { /* Decode until function end */ if (search_exception_tables(addr)) /* * Since some fixup code will jumps into this function, * we can't optimize kprobe in this function. */ return 0; kernel_insn_init(&insn, (void *)addr); insn_get_opcode(&insn); if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION) { ret = recover_probed_instruction(buf, addr); if (ret) return 0; kernel_insn_init(&insn, buf); } insn_get_length(&insn); /* Recover address */ insn.kaddr = (void *)addr; insn.next_byte = (void *)(addr + insn.length); /* Check any instructions don't jump into target */ if (insn_is_indirect_jump(&insn) || insn_jump_into_range(&insn, paddr + INT3_SIZE, RELATIVE_ADDR_SIZE)) return 0; addr += insn.length; } return 1; } /* Check optimized_kprobe can actually be optimized. */ int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op) { int i; struct kprobe *p; for (i = 1; i < op->optinsn.size; i++) { p = get_kprobe(op->kp.addr + i); if (p && !kprobe_disabled(p)) return -EEXIST; } return 0; } /* Check the addr is within the optimized instructions. */ int __kprobes arch_within_optimized_kprobe(struct optimized_kprobe *op, unsigned long addr) { return ((unsigned long)op->kp.addr <= addr && (unsigned long)op->kp.addr + op->optinsn.size > addr); } /* Free optimized instruction slot */ static __kprobes void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty) { if (op->optinsn.insn) { free_optinsn_slot(op->optinsn.insn, dirty); op->optinsn.insn = NULL; op->optinsn.size = 0; } } void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op) { __arch_remove_optimized_kprobe(op, 1); } /* * Copy replacing target instructions * Target instructions MUST be relocatable (checked inside) */ int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op) { u8 *buf; int ret; long rel; if (!can_optimize((unsigned long)op->kp.addr)) return -EILSEQ; op->optinsn.insn = get_optinsn_slot(); if (!op->optinsn.insn) return -ENOMEM; /* * Verify if the address gap is in 2GB range, because this uses * a relative jump. */ rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE; if (abs(rel) > 0x7fffffff) return -ERANGE; buf = (u8 *)op->optinsn.insn; /* Copy instructions into the out-of-line buffer */ ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr); if (ret < 0) { __arch_remove_optimized_kprobe(op, 0); return ret; } op->optinsn.size = ret; /* Copy arch-dep-instance from template */ memcpy(buf, &optprobe_template_entry, TMPL_END_IDX); /* Set probe information */ synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op); /* Set probe function call */ synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback); /* Set returning jmp instruction at the tail of out-of-line buffer */ synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size, (u8 *)op->kp.addr + op->optinsn.size); flush_icache_range((unsigned long) buf, (unsigned long) buf + TMPL_END_IDX + op->optinsn.size + RELATIVEJUMP_SIZE); return 0; } #define MAX_OPTIMIZE_PROBES 256 static struct text_poke_param *jump_poke_params; static struct jump_poke_buffer { u8 buf[RELATIVEJUMP_SIZE]; } *jump_poke_bufs; static void __kprobes setup_optimize_kprobe(struct text_poke_param *tprm, u8 *insn_buf, struct optimized_kprobe *op) { s32 rel = (s32)((long)op->optinsn.insn - ((long)op->kp.addr + RELATIVEJUMP_SIZE)); /* Backup instructions which will be replaced by jump address */ memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE, RELATIVE_ADDR_SIZE); insn_buf[0] = RELATIVEJUMP_OPCODE; *(s32 *)(&insn_buf[1]) = rel; tprm->addr = op->kp.addr; tprm->opcode = insn_buf; tprm->len = RELATIVEJUMP_SIZE; } /* * Replace breakpoints (int3) with relative jumps. * Caller must call with locking kprobe_mutex and text_mutex. */ void __kprobes arch_optimize_kprobes(struct list_head *oplist) { struct optimized_kprobe *op, *tmp; int c = 0; list_for_each_entry_safe(op, tmp, oplist, list) { WARN_ON(kprobe_disabled(&op->kp)); /* Setup param */ setup_optimize_kprobe(&jump_poke_params[c], jump_poke_bufs[c].buf, op); list_del_init(&op->list); if (++c >= MAX_OPTIMIZE_PROBES) break; } /* * text_poke_smp doesn't support NMI/MCE code modifying. * However, since kprobes itself also doesn't support NMI/MCE * code probing, it's not a problem. */ text_poke_smp_batch(jump_poke_params, c); } static void __kprobes setup_unoptimize_kprobe(struct text_poke_param *tprm, u8 *insn_buf, struct optimized_kprobe *op) { /* Set int3 to first byte for kprobes */ insn_buf[0] = BREAKPOINT_INSTRUCTION; memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE); tprm->addr = op->kp.addr; tprm->opcode = insn_buf; tprm->len = RELATIVEJUMP_SIZE; } /* * Recover original instructions and breakpoints from relative jumps. * Caller must call with locking kprobe_mutex. */ extern void arch_unoptimize_kprobes(struct list_head *oplist, struct list_head *done_list) { struct optimized_kprobe *op, *tmp; int c = 0; list_for_each_entry_safe(op, tmp, oplist, list) { /* Setup param */ setup_unoptimize_kprobe(&jump_poke_params[c], jump_poke_bufs[c].buf, op); list_move(&op->list, done_list); if (++c >= MAX_OPTIMIZE_PROBES) break; } /* * text_poke_smp doesn't support NMI/MCE code modifying. * However, since kprobes itself also doesn't support NMI/MCE * code probing, it's not a problem. */ text_poke_smp_batch(jump_poke_params, c); } /* Replace a relative jump with a breakpoint (int3). */ void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op) { u8 buf[RELATIVEJUMP_SIZE]; /* Set int3 to first byte for kprobes */ buf[0] = BREAKPOINT_INSTRUCTION; memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE); text_poke_smp(op->kp.addr, buf, RELATIVEJUMP_SIZE); } static int __kprobes setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter) { struct optimized_kprobe *op; if (p->flags & KPROBE_FLAG_OPTIMIZED) { /* This kprobe is really able to run optimized path. */ op = container_of(p, struct optimized_kprobe, kp); /* Detour through copied instructions */ regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX; if (!reenter) reset_current_kprobe(); preempt_enable_no_resched(); return 1; } return 0; } static int __kprobes init_poke_params(void) { /* Allocate code buffer and parameter array */ jump_poke_bufs = kmalloc(sizeof(struct jump_poke_buffer) * MAX_OPTIMIZE_PROBES, GFP_KERNEL); if (!jump_poke_bufs) return -ENOMEM; jump_poke_params = kmalloc(sizeof(struct text_poke_param) * MAX_OPTIMIZE_PROBES, GFP_KERNEL); if (!jump_poke_params) { kfree(jump_poke_bufs); jump_poke_bufs = NULL; return -ENOMEM; } return 0; } #else /* !CONFIG_OPTPROBES */ static int __kprobes init_poke_params(void) { return 0; } #endif int __init arch_init_kprobes(void) { return init_poke_params(); } int __kprobes arch_trampoline_kprobe(struct kprobe *p) { return 0; }