/* * 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-Nov Ananth N Mavinakayanahalli kprobes port * for PPC64 */ #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_PPC_ADV_DEBUG_REGS #define MSR_SINGLESTEP (MSR_DE) #else #define MSR_SINGLESTEP (MSR_SE) #endif DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}}; int __kprobes arch_prepare_kprobe(struct kprobe *p) { int ret = 0; kprobe_opcode_t insn = *p->addr; if ((unsigned long)p->addr & 0x03) { printk("Attempt to register kprobe at an unaligned address\n"); ret = -EINVAL; } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) { printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n"); ret = -EINVAL; } /* insn must be on a special executable page on ppc64. This is * not explicitly required on ppc32 (right now), but it doesn't hurt */ if (!ret) { p->ainsn.insn = get_insn_slot(); if (!p->ainsn.insn) ret = -ENOMEM; } if (!ret) { memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t)); p->opcode = *p->addr; flush_icache_range((unsigned long)p->ainsn.insn, (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t)); } p->ainsn.boostable = 0; return ret; } void __kprobes arch_arm_kprobe(struct kprobe *p) { *p->addr = BREAKPOINT_INSTRUCTION; flush_icache_range((unsigned long) p->addr, (unsigned long) p->addr + sizeof(kprobe_opcode_t)); } void __kprobes arch_disarm_kprobe(struct kprobe *p) { *p->addr = p->opcode; flush_icache_range((unsigned long) p->addr, (unsigned long) p->addr + sizeof(kprobe_opcode_t)); } void __kprobes arch_remove_kprobe(struct kprobe *p) { if (p->ainsn.insn) { free_insn_slot(p->ainsn.insn, 0); p->ainsn.insn = NULL; } } static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) { /* We turn off async exceptions to ensure that the single step will * be for the instruction we have the kprobe on, if we dont its * possible we'd get the single step reported for an exception handler * like Decrementer or External Interrupt */ regs->msr &= ~MSR_EE; regs->msr |= MSR_SINGLESTEP; #ifdef CONFIG_PPC_ADV_DEBUG_REGS regs->msr &= ~MSR_CE; mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM); #ifdef CONFIG_PPC_47x isync(); #endif #endif /* * On powerpc we should single step on the original * instruction even if the probed insn is a trap * variant as values in regs could play a part in * if the trap is taken or not */ regs->nip = (unsigned long)p->ainsn.insn; } 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.saved_msr = kcb->kprobe_saved_msr; } 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_saved_msr = kcb->prev_kprobe.saved_msr; } 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_msr = regs->msr; } void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs) { ri->ret_addr = (kprobe_opcode_t *)regs->link; /* Replace the return addr with trampoline addr */ regs->link = (unsigned long)kretprobe_trampoline; } static int __kprobes kprobe_handler(struct pt_regs *regs) { struct kprobe *p; int ret = 0; unsigned int *addr = (unsigned int *)regs->nip; struct kprobe_ctlblk *kcb; /* * 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) { kprobe_opcode_t insn = *p->ainsn.insn; if (kcb->kprobe_status == KPROBE_HIT_SS && is_trap(insn)) { /* Turn off 'trace' bits */ regs->msr &= ~MSR_SINGLESTEP; regs->msr |= kcb->kprobe_saved_msr; 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); kcb->kprobe_saved_msr = regs->msr; kprobes_inc_nmissed_count(p); prepare_singlestep(p, regs); kcb->kprobe_status = KPROBE_REENTER; return 1; } else { if (*addr != BREAKPOINT_INSTRUCTION) { /* If trap variant, then it belongs not to us */ kprobe_opcode_t cur_insn = *addr; if (is_trap(cur_insn)) goto no_kprobe; /* The breakpoint instruction was removed by * another cpu right after we hit, no further * handling of this interrupt is appropriate */ 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) { /* * PowerPC has multiple variants of the "trap" * instruction. If the current instruction is a * trap variant, it could belong to someone else */ kprobe_opcode_t cur_insn = *addr; if (is_trap(cur_insn)) goto no_kprobe; /* * 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. */ ret = 1; } /* Not one of ours: let kernel handle it */ goto no_kprobe; } kcb->kprobe_status = KPROBE_HIT_ACTIVE; set_current_kprobe(p, regs, kcb); if (p->pre_handler && p->pre_handler(p, regs)) /* handler has already set things up, so skip ss setup */ return 1; ss_probe: if (p->ainsn.boostable >= 0) { unsigned int insn = *p->ainsn.insn; /* regs->nip is also adjusted if emulate_step returns 1 */ ret = emulate_step(regs, insn); if (ret > 0) { /* * Once this instruction has been boosted * successfully, set the boostable flag */ if (unlikely(p->ainsn.boostable == 0)) p->ainsn.boostable = 1; if (p->post_handler) p->post_handler(p, regs, 0); kcb->kprobe_status = KPROBE_HIT_SSDONE; reset_current_kprobe(); preempt_enable_no_resched(); return 1; } else if (ret < 0) { /* * We don't allow kprobes on mtmsr(d)/rfi(d), etc. * So, we should never get here... but, its still * good to catch them, just in case... */ printk("Can't step on instruction %x\n", insn); BUG(); } else if (ret == 0) /* This instruction can't be boosted */ p->ainsn.boostable = -1; } prepare_singlestep(p, regs); kcb->kprobe_status = KPROBE_HIT_SS; return 1; no_kprobe: preempt_enable_no_resched(); return ret; } /* * 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:\n" "nop\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 = 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); 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 */ 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) ri->rp->handler(ri, regs); 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); regs->nip = orig_ret_address; reset_current_kprobe(); 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 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; /* make sure we got here for instruction we have a kprobe on */ if (((unsigned long)cur->ainsn.insn + 4) != regs->nip) return 0; if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { kcb->kprobe_status = KPROBE_HIT_SSDONE; cur->post_handler(cur, regs, 0); } /* Adjust nip to after the single-stepped instruction */ regs->nip = (unsigned long)cur->addr + 4; regs->msr |= kcb->kprobe_saved_msr; /*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, msr * will have DE/SE set, in which case, continue the remaining processing * of do_debug, as if this is not a probe hit. */ if (regs->msr & MSR_SINGLESTEP) 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(); const struct exception_table_entry *entry; 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 nip points back to the probe address * and allow the page fault handler to continue as a * normal page fault. */ regs->nip = (unsigned long)cur->addr; regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */ regs->msr |= kcb->kprobe_saved_msr; 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 ((entry = search_exception_tables(regs->nip)) != NULL) { regs->nip = entry->fixup; 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(args->regs)) return ret; switch (val) { case DIE_BPT: if (kprobe_handler(args->regs)) ret = NOTIFY_STOP; break; case DIE_SSTEP: if (post_kprobe_handler(args->regs)) ret = NOTIFY_STOP; break; default: break; } return ret; } #ifdef CONFIG_PPC64 unsigned long arch_deref_entry_point(void *entry) { return ((func_descr_t *)entry)->entry; } #endif 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(); memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs)); /* setup return addr to the jprobe handler routine */ regs->nip = arch_deref_entry_point(jp->entry); #ifdef CONFIG_PPC64 regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc); #endif return 1; } void __used __kprobes jprobe_return(void) { asm volatile("trap" ::: "memory"); } static void __used __kprobes jprobe_return_end(void) { }; int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); /* * FIXME - we should ideally be validating that we got here 'cos * of the "trap" in jprobe_return() above, before restoring the * saved regs... */ memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs)); preempt_enable_no_resched(); return 1; } static struct kprobe trampoline_p = { .addr = (kprobe_opcode_t *) &kretprobe_trampoline, .pre_handler = trampoline_probe_handler }; int __init arch_init_kprobes(void) { return register_kprobe(&trampoline_p); } int __kprobes arch_trampoline_kprobe(struct kprobe *p) { if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline) return 1; return 0; }