/* * 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, 2006 * * s390 port, used ppc64 as template. Mike Grundy */ #include #include #include #include #include #include #include #include #include #include #include DEFINE_PER_CPU(struct kprobe *, current_kprobe); DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); struct kretprobe_blackpoint kretprobe_blacklist[] = { }; static int __kprobes is_prohibited_opcode(kprobe_opcode_t *insn) { switch (insn[0] >> 8) { case 0x0c: /* bassm */ case 0x0b: /* bsm */ case 0x83: /* diag */ case 0x44: /* ex */ case 0xac: /* stnsm */ case 0xad: /* stosm */ return -EINVAL; } switch (insn[0]) { case 0x0101: /* pr */ case 0xb25a: /* bsa */ case 0xb240: /* bakr */ case 0xb258: /* bsg */ case 0xb218: /* pc */ case 0xb228: /* pt */ case 0xb98d: /* epsw */ return -EINVAL; } return 0; } static int __kprobes get_fixup_type(kprobe_opcode_t *insn) { /* default fixup method */ int fixup = FIXUP_PSW_NORMAL; switch (insn[0] >> 8) { case 0x05: /* balr */ case 0x0d: /* basr */ fixup = FIXUP_RETURN_REGISTER; /* if r2 = 0, no branch will be taken */ if ((insn[0] & 0x0f) == 0) fixup |= FIXUP_BRANCH_NOT_TAKEN; break; case 0x06: /* bctr */ case 0x07: /* bcr */ fixup = FIXUP_BRANCH_NOT_TAKEN; break; case 0x45: /* bal */ case 0x4d: /* bas */ fixup = FIXUP_RETURN_REGISTER; break; case 0x47: /* bc */ case 0x46: /* bct */ case 0x86: /* bxh */ case 0x87: /* bxle */ fixup = FIXUP_BRANCH_NOT_TAKEN; break; case 0x82: /* lpsw */ fixup = FIXUP_NOT_REQUIRED; break; case 0xb2: /* lpswe */ if ((insn[0] & 0xff) == 0xb2) fixup = FIXUP_NOT_REQUIRED; break; case 0xa7: /* bras */ if ((insn[0] & 0x0f) == 0x05) fixup |= FIXUP_RETURN_REGISTER; break; case 0xc0: if ((insn[0] & 0x0f) == 0x00 || /* larl */ (insn[0] & 0x0f) == 0x05) /* brasl */ fixup |= FIXUP_RETURN_REGISTER; break; case 0xeb: if ((insn[2] & 0xff) == 0x44 || /* bxhg */ (insn[2] & 0xff) == 0x45) /* bxleg */ fixup = FIXUP_BRANCH_NOT_TAKEN; break; case 0xe3: /* bctg */ if ((insn[2] & 0xff) == 0x46) fixup = FIXUP_BRANCH_NOT_TAKEN; break; } return fixup; } int __kprobes arch_prepare_kprobe(struct kprobe *p) { if ((unsigned long) p->addr & 0x01) return -EINVAL; /* Make sure the probe isn't going on a difficult instruction */ if (is_prohibited_opcode(p->addr)) return -EINVAL; p->opcode = *p->addr; memcpy(p->ainsn.insn, p->addr, ((p->opcode >> 14) + 3) & -2); return 0; } struct ins_replace_args { kprobe_opcode_t *ptr; kprobe_opcode_t opcode; }; static int __kprobes swap_instruction(void *aref) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long status = kcb->kprobe_status; struct ins_replace_args *args = aref; kcb->kprobe_status = KPROBE_SWAP_INST; probe_kernel_write(args->ptr, &args->opcode, sizeof(args->opcode)); kcb->kprobe_status = status; return 0; } void __kprobes arch_arm_kprobe(struct kprobe *p) { struct ins_replace_args args; args.ptr = p->addr; args.opcode = BREAKPOINT_INSTRUCTION; stop_machine(swap_instruction, &args, NULL); } void __kprobes arch_disarm_kprobe(struct kprobe *p) { struct ins_replace_args args; args.ptr = p->addr; args.opcode = p->opcode; stop_machine(swap_instruction, &args, NULL); } void __kprobes arch_remove_kprobe(struct kprobe *p) { } static void __kprobes enable_singlestep(struct kprobe_ctlblk *kcb, struct pt_regs *regs, unsigned long ip) { struct per_regs per_kprobe; /* Set up the PER control registers %cr9-%cr11 */ per_kprobe.control = PER_EVENT_IFETCH; per_kprobe.start = ip; per_kprobe.end = ip; /* Save control regs and psw mask */ __ctl_store(kcb->kprobe_saved_ctl, 9, 11); kcb->kprobe_saved_imask = regs->psw.mask & (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT); /* Set PER control regs, turns on single step for the given address */ __ctl_load(per_kprobe, 9, 11); regs->psw.mask |= PSW_MASK_PER; regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT); regs->psw.addr = ip | PSW_ADDR_AMODE; } static void __kprobes disable_singlestep(struct kprobe_ctlblk *kcb, struct pt_regs *regs, unsigned long ip) { /* Restore control regs and psw mask, set new psw address */ __ctl_load(kcb->kprobe_saved_ctl, 9, 11); regs->psw.mask &= ~PSW_MASK_PER; regs->psw.mask |= kcb->kprobe_saved_imask; regs->psw.addr = ip | PSW_ADDR_AMODE; } /* * Activate a kprobe by storing its pointer to current_kprobe. The * previous kprobe is stored in kcb->prev_kprobe. A stack of up to * two kprobes can be active, see KPROBE_REENTER. */ static void __kprobes push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p) { kcb->prev_kprobe.kp = __get_cpu_var(current_kprobe); kcb->prev_kprobe.status = kcb->kprobe_status; __get_cpu_var(current_kprobe) = p; } /* * Deactivate a kprobe by backing up to the previous state. If the * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL, * for any other state prev_kprobe.kp will be NULL. */ static void __kprobes pop_kprobe(struct kprobe_ctlblk *kcb) { __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; kcb->kprobe_status = kcb->prev_kprobe.status; } void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) { ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14]; /* Replace the return addr with trampoline addr */ regs->gprs[14] = (unsigned long) &kretprobe_trampoline; } static void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p) { switch (kcb->kprobe_status) { case KPROBE_HIT_SSDONE: case KPROBE_HIT_ACTIVE: kprobes_inc_nmissed_count(p); break; case KPROBE_HIT_SS: case KPROBE_REENTER: default: /* * A kprobe on the code path to single step an instruction * is a BUG. The code path resides in the .kprobes.text * section and is executed with interrupts disabled. */ printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr); dump_kprobe(p); BUG(); } } static int __kprobes kprobe_handler(struct pt_regs *regs) { struct kprobe_ctlblk *kcb; struct kprobe *p; /* * We want to disable preemption for the entire duration of kprobe * processing. That includes the calls to the pre/post handlers * and single stepping the kprobe instruction. */ preempt_disable(); kcb = get_kprobe_ctlblk(); p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2)); if (p) { if (kprobe_running()) { /* * We have hit a kprobe while another is still * active. This can happen in the pre and post * handler. Single step the instruction of the * new probe but do not call any handler function * of this secondary kprobe. * push_kprobe and pop_kprobe saves and restores * the currently active kprobe. */ kprobe_reenter_check(kcb, p); push_kprobe(kcb, p); kcb->kprobe_status = KPROBE_REENTER; } else { /* * If we have no pre-handler or it returned 0, we * continue with single stepping. 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. */ push_kprobe(kcb, p); kcb->kprobe_status = KPROBE_HIT_ACTIVE; if (p->pre_handler && p->pre_handler(p, regs)) return 1; kcb->kprobe_status = KPROBE_HIT_SS; } enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn); return 1; } else if (kprobe_running()) { p = __get_cpu_var(current_kprobe); if (p->break_handler && p->break_handler(p, regs)) { /* * Continuation after the jprobe completed and * caused the jprobe_return trap. The jprobe * break_handler "returns" to the original * function that still has the kprobe breakpoint * installed. We continue with single stepping. */ kcb->kprobe_status = KPROBE_HIT_SS; enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn); return 1; } /* else: * No kprobe at this address and the current kprobe * has no break handler (no jprobe!). The kernel just * exploded, let the standard trap handler pick up the * pieces. */ } /* else: * No kprobe at this address and no active kprobe. The trap has * not been caused by a kprobe breakpoint. The race of breakpoint * vs. kprobe remove does not exist because on s390 as we use * stop_machine to arm/disarm the breakpoints. */ preempt_enable_no_resched(); return 0; } /* * Function return probe trampoline: * - init_kprobes() establishes a probepoint here * - When the probed function returns, this probe * causes the handlers to fire */ static void __used kretprobe_trampoline_holder(void) { asm volatile(".global kretprobe_trampoline\n" "kretprobe_trampoline: bcr 0,0\n"); } /* * Called when the probe at kretprobe trampoline is hit */ static int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) { struct kretprobe_instance *ri; struct hlist_head *head, empty_rp; struct hlist_node *node, *tmp; unsigned long flags, orig_ret_address; unsigned long trampoline_address; kprobe_opcode_t *correct_ret_addr; INIT_HLIST_HEAD(&empty_rp); kretprobe_hash_lock(current, &head, &flags); /* * 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 than 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 */ ri = NULL; orig_ret_address = 0; correct_ret_addr = NULL; trampoline_address = (unsigned long) &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) { ri->ret_addr = correct_ret_addr; ri->rp->handler(ri, regs); } 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; } regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE; pop_kprobe(get_kprobe_ctlblk()); kretprobe_hash_unlock(current, &flags); preempt_enable_no_resched(); hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { hlist_del(&ri->hlist); kfree(ri); } /* * By returning a non-zero value, we are telling * kprobe_handler() that we don't want the post_handler * to run (and have re-enabled preemption) */ return 1; } /* * Called after single-stepping. p->addr is the address of the * instruction whose first byte has been replaced by the "breakpoint" * 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. */ static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long ip = regs->psw.addr & PSW_ADDR_INSN; int fixup = get_fixup_type(p->ainsn.insn); if (fixup & FIXUP_PSW_NORMAL) ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn; if (fixup & FIXUP_BRANCH_NOT_TAKEN) { int ilen = ((p->ainsn.insn[0] >> 14) + 3) & -2; if (ip - (unsigned long) p->ainsn.insn == ilen) ip = (unsigned long) p->addr + ilen; } if (fixup & FIXUP_RETURN_REGISTER) { int reg = (p->ainsn.insn[0] & 0xf0) >> 4; regs->gprs[reg] += (unsigned long) p->addr - (unsigned long) p->ainsn.insn; } disable_singlestep(kcb, regs, ip); } static int __kprobes post_kprobe_handler(struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); struct kprobe *p = kprobe_running(); if (!p) return 0; if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) { kcb->kprobe_status = KPROBE_HIT_SSDONE; p->post_handler(p, regs, 0); } resume_execution(p, regs); pop_kprobe(kcb); preempt_enable_no_resched(); /* * if somebody else is singlestepping across a probe point, psw mask * will have PER set, in which case, continue the remaining processing * of do_single_step, as if this is not a probe hit. */ if (regs->psw.mask & PSW_MASK_PER) return 0; return 1; } static int __kprobes kprobe_trap_handler(struct pt_regs *regs, int trapnr) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); struct kprobe *p = kprobe_running(); const struct exception_table_entry *entry; switch(kcb->kprobe_status) { case KPROBE_SWAP_INST: /* We are here because the instruction replacement failed */ return 0; 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 nip points back to the probe address * and allow the page fault handler to continue as a * normal page fault. */ disable_singlestep(kcb, regs, (unsigned long) p->addr); pop_kprobe(kcb); 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(p); /* * 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 (p->fault_handler && p->fault_handler(p, regs, trapnr)) return 1; /* * In case the user-specified fault handler returned * zero, try to fix up. */ entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN); if (entry) { regs->psw.addr = entry->fixup | PSW_ADDR_AMODE; return 1; } /* * fixup_exception() could not handle it, * Let do_page_fault() fix it. */ break; default: break; } return 0; } int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) { int ret; if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) local_irq_disable(); ret = kprobe_trap_handler(regs, trapnr); if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) local_irq_restore(regs->psw.mask & ~PSW_MASK_PER); return ret; } /* * 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; struct pt_regs *regs = args->regs; int ret = NOTIFY_DONE; if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) local_irq_disable(); switch (val) { case DIE_BPT: if (kprobe_handler(regs)) ret = NOTIFY_STOP; break; case DIE_SSTEP: if (post_kprobe_handler(regs)) ret = NOTIFY_STOP; break; case DIE_TRAP: if (!preemptible() && kprobe_running() && kprobe_trap_handler(regs, args->trapnr)) ret = NOTIFY_STOP; break; default: break; } if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT)) local_irq_restore(regs->psw.mask & ~PSW_MASK_PER); return ret; } int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) { struct jprobe *jp = container_of(p, struct jprobe, kp); struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long stack; memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs)); /* setup return addr to the jprobe handler routine */ regs->psw.addr = (unsigned long) jp->entry | PSW_ADDR_AMODE; regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT); /* r15 is the stack pointer */ stack = (unsigned long) regs->gprs[15]; memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack)); return 1; } void __kprobes jprobe_return(void) { asm volatile(".word 0x0002"); } void __kprobes jprobe_return_end(void) { asm volatile("bcr 0,0"); } int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long stack; stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15]; /* Put the regs back */ memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs)); /* put the stack back */ memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack)); preempt_enable_no_resched(); return 1; } static struct kprobe trampoline = { .addr = (kprobe_opcode_t *) &kretprobe_trampoline, .pre_handler = trampoline_probe_handler }; int __init arch_init_kprobes(void) { return register_kprobe(&trampoline); } int __kprobes arch_trampoline_kprobe(struct kprobe *p) { return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline; }