/* * 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. * 2005-May Hien Nguyen , Jim Keniston * and Prasanna S Panchamukhi * added function-return probes. */ #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); 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); /* insert a jmp code */ static __always_inline void set_jmp_op(void *from, void *to) { struct __arch_jmp_op { char op; long raddr; } __attribute__((packed)) *jop; jop = (struct __arch_jmp_op *)from; jop->raddr = (long)(to) - ((long)(from) + 5); jop->op = RELATIVEJUMP_INSTRUCTION; } /* * returns non-zero if opcodes can be boosted. */ static __always_inline int can_boost(kprobe_opcode_t *opcodes) { #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 be boost. */ static const unsigned long 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 kprobe_opcode_t opcode; kprobe_opcode_t *orig_opcodes = opcodes; 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, twobyte_is_boostable); } switch (opcode & 0xf0) { 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 can be boost */ return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe)); default: if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e) goto retry; /* prefixes */ /* can't boost CS override and call */ return (opcode != 0x2e && opcode != 0x9a); } } /* * returns non-zero if opcode modifies the interrupt flag. */ static int __kprobes is_IF_modifier(kprobe_opcode_t opcode) { switch (opcode) { case 0xfa: /* cli */ case 0xfb: /* sti */ case 0xcf: /* iret/iretd */ case 0x9d: /* popf/popfd */ return 1; } return 0; } int __kprobes arch_prepare_kprobe(struct kprobe *p) { /* insn: must be on special executable page on i386. */ p->ainsn.insn = get_insn_slot(); if (!p->ainsn.insn) return -ENOMEM; memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); p->opcode = *p->addr; if (can_boost(p->addr)) { p->ainsn.boostable = 0; } else { p->ainsn.boostable = -1; } 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) { mutex_lock(&kprobe_mutex); free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1)); mutex_unlock(&kprobe_mutex); } 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_eflags = kcb->kprobe_old_eflags; kcb->prev_kprobe.saved_eflags = kcb->kprobe_saved_eflags; } 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_eflags = kcb->prev_kprobe.old_eflags; kcb->kprobe_saved_eflags = kcb->prev_kprobe.saved_eflags; } 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_eflags = kcb->kprobe_old_eflags = (regs->flags & (TF_MASK | IF_MASK)); if (is_IF_modifier(p->opcode)) kcb->kprobe_saved_eflags &= ~IF_MASK; } static __always_inline void clear_btf(void) { if (test_thread_flag(TIF_DEBUGCTLMSR)) wrmsr(MSR_IA32_DEBUGCTLMSR, 0, 0); } static __always_inline void restore_btf(void) { if (test_thread_flag(TIF_DEBUGCTLMSR)) wrmsr(MSR_IA32_DEBUGCTLMSR, current->thread.debugctlmsr, 0); } static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) { clear_btf(); regs->flags |= TF_MASK; regs->flags &= ~IF_MASK; /*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; } /* Called with kretprobe_lock held */ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) { unsigned long *sara = (unsigned long *)®s->sp; ri->ret_addr = (kprobe_opcode_t *) *sara; /* Replace the return addr with trampoline addr */ *sara = (unsigned long) &kretprobe_trampoline; } /* * Interrupts are disabled on entry as trap3 is an interrupt gate and they * remain disabled thorough out this function. */ static int __kprobes kprobe_handler(struct pt_regs *regs) { struct kprobe *p; int ret = 0; kprobe_opcode_t *addr; 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 */ preempt_disable(); kcb = get_kprobe_ctlblk(); /* Check we're not actually recursing */ if (kprobe_running()) { p = get_kprobe(addr); if (p) { if (kcb->kprobe_status == KPROBE_HIT_SS && *p->ainsn.insn == BREAKPOINT_INSTRUCTION) { regs->flags &= ~TF_MASK; regs->flags |= kcb->kprobe_saved_eflags; goto no_kprobe; } /* We have reentered the kprobe_handler(), since * another probe was hit while within the handler. * We here save the original kprobes variables and * just single step on the instruction of the new probe * without calling any user handlers. */ save_previous_kprobe(kcb); set_current_kprobe(p, regs, kcb); kprobes_inc_nmissed_count(p); prepare_singlestep(p, regs); kcb->kprobe_status = KPROBE_REENTER; return 1; } else { if (*addr != BREAKPOINT_INSTRUCTION) { /* The breakpoint instruction was removed by * another cpu right after we hit, no further * handling of this interrupt is appropriate */ regs->ip -= sizeof(kprobe_opcode_t); ret = 1; goto no_kprobe; } p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { goto ss_probe; } } goto no_kprobe; } p = get_kprobe(addr); if (!p) { 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 -= sizeof(kprobe_opcode_t); ret = 1; } /* Not one of ours: let kernel handle it */ goto no_kprobe; } set_current_kprobe(p, regs, kcb); kcb->kprobe_status = KPROBE_HIT_ACTIVE; if (p->pre_handler && p->pre_handler(p, regs)) /* handler has already set things up, so skip ss setup */ return 1; ss_probe: #if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM) if (p->ainsn.boostable == 1 && !p->post_handler){ /* Boost up -- we can execute copied instructions directly */ reset_current_kprobe(); regs->ip = (unsigned long)p->ainsn.insn; preempt_enable_no_resched(); return 1; } #endif prepare_singlestep(p, regs); kcb->kprobe_status = KPROBE_HIT_SS; return 1; no_kprobe: preempt_enable_no_resched(); return ret; } /* * For function-return probes, init_kprobes() establishes a probepoint * here. When a retprobed function returns, this probe is hit and * trampoline_probe_handler() runs, calling the kretprobe's handler. */ void __kprobes kretprobe_trampoline_holder(void) { asm volatile ( ".global kretprobe_trampoline\n" "kretprobe_trampoline: \n" " pushf\n" /* skip cs, ip, orig_ax */ " subl $12, %esp\n" " pushl %fs\n" " pushl %ds\n" " pushl %es\n" " pushl %eax\n" " pushl %ebp\n" " pushl %edi\n" " pushl %esi\n" " pushl %edx\n" " pushl %ecx\n" " pushl %ebx\n" " movl %esp, %eax\n" " call trampoline_handler\n" /* move flags to cs */ " movl 52(%esp), %edx\n" " movl %edx, 48(%esp)\n" /* save true return address on flags */ " movl %eax, 52(%esp)\n" " popl %ebx\n" " popl %ecx\n" " popl %edx\n" " popl %esi\n" " popl %edi\n" " popl %ebp\n" " popl %eax\n" /* skip ip, orig_ax, es, ds, fs */ " addl $20, %esp\n" " popf\n" " ret\n"); } /* * Called from kretprobe_trampoline */ void *__kprobes 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; INIT_HLIST_HEAD(&empty_rp); spin_lock_irqsave(&kretprobe_lock, flags); head = kretprobe_inst_table_head(current); /* fixup registers */ regs->cs = __KERNEL_CS | get_kernel_rpl(); regs->ip = trampoline_address; regs->orig_ax = 0xffffffff; /* * It is possible to have multiple instances associated with a given * task either because an multiple functions in the call path * have a return probe installed on them, and/or more then one return * return probe was registered for a target function. * * We can handle this because: * - instances are always inserted at the head of the list * - when multiple return probes are registered for the same * function, the first instance's ret_addr will point to 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; if (ri->rp && ri->rp->handler){ __get_cpu_var(current_kprobe) = &ri->rp->kp; get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; ri->rp->handler(ri, regs); __get_cpu_var(current_kprobe) = NULL; } orig_ret_address = (unsigned long)ri->ret_addr; 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_assert(ri, orig_ret_address, trampoline_address); spin_unlock_irqrestore(&kretprobe_lock, 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. * * This function also checks instruction size for preparing direct execution. */ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb) { unsigned long *tos = (unsigned long *)®s->sp; unsigned long copy_eip = (unsigned long)p->ainsn.insn; unsigned long orig_eip = (unsigned long)p->addr; regs->flags &= ~TF_MASK; switch (p->ainsn.insn[0]) { case 0x9c: /* pushfl */ *tos &= ~(TF_MASK | IF_MASK); *tos |= kcb->kprobe_old_eflags; 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_eip + (*tos - copy_eip); break; case 0x9a: /* call absolute -- same as call absolute, indirect */ *tos = orig_eip + (*tos - copy_eip); goto no_change; case 0xff: if ((p->ainsn.insn[1] & 0x30) == 0x10) { /* * call absolute, indirect * Fix return addr; ip is correct. * But this is not boostable */ *tos = orig_eip + (*tos - copy_eip); goto no_change; } else if (((p->ainsn.insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */ ((p->ainsn.insn[1] & 0x31) == 0x21)) { /* jmp 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_eip) && (regs->ip - copy_eip) + 5 < MAX_INSN_SIZE) { /* * These instructions can be executed directly if it * jumps back to correct address. */ set_jmp_op((void *)regs->ip, (void *)orig_eip + (regs->ip - copy_eip)); p->ainsn.boostable = 1; } else { p->ainsn.boostable = -1; } } regs->ip = orig_eip + (regs->ip - copy_eip); no_change: restore_btf(); return; } /* * Interrupts are disabled on entry as trap1 is an interrupt gate and they * remain disabled thoroughout 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; if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { kcb->kprobe_status = KPROBE_HIT_SSDONE; cur->post_handler(cur, regs, 0); } resume_execution(cur, regs, kcb); regs->flags |= kcb->kprobe_saved_eflags; trace_hardirqs_fixup_flags(regs->flags); /*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 & TF_MASK) 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_eflags; 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 accouting * 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_exception() could not handle it, * Let do_page_fault() fix it. */ break; default: break; } return 0; } /* * Wrapper routine to for handling exceptions. */ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data) { struct die_args *args = (struct die_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)) ret = NOTIFY_STOP; break; case DIE_GPF: /* kprobe_running() needs smp_processor_id() */ preempt_disable(); if (kprobe_running() && kprobe_fault_handler(args->regs, args->trapnr)) ret = NOTIFY_STOP; preempt_enable(); 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_esp = ®s->sp; addr = (unsigned long)(kcb->jprobe_saved_esp); /* * TBD: 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 &= ~IF_MASK; 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 (" xchgl %%ebx,%%esp \n" " int3 \n" " .globl jprobe_return_end \n" " jprobe_return_end: \n" " nop \n"::"b" (kcb->jprobe_saved_esp):"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); unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_esp); struct jprobe *jp = container_of(p, struct jprobe, kp); if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) { if (®s->sp != kcb->jprobe_saved_esp) { struct pt_regs *saved_regs = &kcb->jprobe_saved_regs; printk("current sp %p does not match saved sp %p\n", ®s->sp, kcb->jprobe_saved_esp); printk("Saved registers for jprobe %p\n", jp); show_registers(saved_regs); printk("Current registers\n"); show_registers(regs); BUG(); } *regs = kcb->jprobe_saved_regs; memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack, MIN_STACK_SIZE(stack_addr)); preempt_enable_no_resched(); return 1; } return 0; } int __kprobes arch_trampoline_kprobe(struct kprobe *p) { return 0; } int __init arch_init_kprobes(void) { return 0; }