/* * Kernel Probes (KProbes) * kernel/kprobes.c * * 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 <vamsi_krishna@in.ibm.com> Kernel * Probes initial implementation (includes suggestions from * Rusty Russell). * 2004-Aug Updated by Prasanna S Panchamukhi <prasanna@in.ibm.com> with * hlists and exceptions notifier as suggested by Andi Kleen. * 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes * interface to access function arguments. * 2004-Sep Prasanna S Panchamukhi <prasanna@in.ibm.com> Changed Kprobes * exceptions notifier to be first on the priority list. */ #include <linux/kprobes.h> #include <linux/spinlock.h> #include <linux/hash.h> #include <linux/init.h> #include <linux/module.h> #include <asm/cacheflush.h> #include <asm/errno.h> #include <asm/kdebug.h> #define KPROBE_HASH_BITS 6 #define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE]; unsigned int kprobe_cpu = NR_CPUS; static DEFINE_SPINLOCK(kprobe_lock); static struct kprobe *curr_kprobe; /* Locks kprobe: irqs must be disabled */ void lock_kprobes(void) { spin_lock(&kprobe_lock); kprobe_cpu = smp_processor_id(); } void unlock_kprobes(void) { kprobe_cpu = NR_CPUS; spin_unlock(&kprobe_lock); } /* You have to be holding the kprobe_lock */ struct kprobe *get_kprobe(void *addr) { struct hlist_head *head; struct hlist_node *node; head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)]; hlist_for_each(node, head) { struct kprobe *p = hlist_entry(node, struct kprobe, hlist); if (p->addr == addr) return p; } return NULL; } /* * Aggregate handlers for multiple kprobes support - these handlers * take care of invoking the individual kprobe handlers on p->list */ int aggr_pre_handler(struct kprobe *p, struct pt_regs *regs) { struct kprobe *kp; list_for_each_entry(kp, &p->list, list) { if (kp->pre_handler) { curr_kprobe = kp; kp->pre_handler(kp, regs); curr_kprobe = NULL; } } return 0; } void aggr_post_handler(struct kprobe *p, struct pt_regs *regs, unsigned long flags) { struct kprobe *kp; list_for_each_entry(kp, &p->list, list) { if (kp->post_handler) { curr_kprobe = kp; kp->post_handler(kp, regs, flags); curr_kprobe = NULL; } } return; } int aggr_fault_handler(struct kprobe *p, struct pt_regs *regs, int trapnr) { /* * if we faulted "during" the execution of a user specified * probe handler, invoke just that probe's fault handler */ if (curr_kprobe && curr_kprobe->fault_handler) { if (curr_kprobe->fault_handler(curr_kprobe, regs, trapnr)) return 1; } return 0; } /* * Fill in the required fields of the "manager kprobe". Replace the * earlier kprobe in the hlist with the manager kprobe */ static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p) { ap->addr = p->addr; ap->opcode = p->opcode; memcpy(&ap->ainsn, &p->ainsn, sizeof(struct arch_specific_insn)); ap->pre_handler = aggr_pre_handler; ap->post_handler = aggr_post_handler; ap->fault_handler = aggr_fault_handler; INIT_LIST_HEAD(&ap->list); list_add(&p->list, &ap->list); INIT_HLIST_NODE(&ap->hlist); hlist_del(&p->hlist); hlist_add_head(&ap->hlist, &kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]); } /* * This is the second or subsequent kprobe at the address - handle * the intricacies * TODO: Move kcalloc outside the spinlock */ static int register_aggr_kprobe(struct kprobe *old_p, struct kprobe *p) { int ret = 0; struct kprobe *ap; if (old_p->break_handler || p->break_handler) { ret = -EEXIST; /* kprobe and jprobe can't (yet) coexist */ } else if (old_p->pre_handler == aggr_pre_handler) { list_add(&p->list, &old_p->list); } else { ap = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC); if (!ap) return -ENOMEM; add_aggr_kprobe(ap, old_p); list_add(&p->list, &ap->list); } return ret; } /* kprobe removal house-keeping routines */ static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags) { *p->addr = p->opcode; hlist_del(&p->hlist); flush_icache_range((unsigned long) p->addr, (unsigned long) p->addr + sizeof(kprobe_opcode_t)); spin_unlock_irqrestore(&kprobe_lock, flags); arch_remove_kprobe(p); } static inline void cleanup_aggr_kprobe(struct kprobe *old_p, struct kprobe *p, unsigned long flags) { list_del(&p->list); if (list_empty(&old_p->list)) { cleanup_kprobe(old_p, flags); kfree(old_p); } else spin_unlock_irqrestore(&kprobe_lock, flags); } int register_kprobe(struct kprobe *p) { int ret = 0; unsigned long flags = 0; struct kprobe *old_p; if ((ret = arch_prepare_kprobe(p)) != 0) { goto rm_kprobe; } spin_lock_irqsave(&kprobe_lock, flags); old_p = get_kprobe(p->addr); if (old_p) { ret = register_aggr_kprobe(old_p, p); goto out; } arch_copy_kprobe(p); INIT_HLIST_NODE(&p->hlist); hlist_add_head(&p->hlist, &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]); p->opcode = *p->addr; *p->addr = BREAKPOINT_INSTRUCTION; flush_icache_range((unsigned long) p->addr, (unsigned long) p->addr + sizeof(kprobe_opcode_t)); out: spin_unlock_irqrestore(&kprobe_lock, flags); rm_kprobe: if (ret == -EEXIST) arch_remove_kprobe(p); return ret; } void unregister_kprobe(struct kprobe *p) { unsigned long flags; struct kprobe *old_p; spin_lock_irqsave(&kprobe_lock, flags); old_p = get_kprobe(p->addr); if (old_p) { if (old_p->pre_handler == aggr_pre_handler) cleanup_aggr_kprobe(old_p, p, flags); else cleanup_kprobe(p, flags); } else spin_unlock_irqrestore(&kprobe_lock, flags); } static struct notifier_block kprobe_exceptions_nb = { .notifier_call = kprobe_exceptions_notify, .priority = 0x7fffffff /* we need to notified first */ }; int register_jprobe(struct jprobe *jp) { /* Todo: Verify probepoint is a function entry point */ jp->kp.pre_handler = setjmp_pre_handler; jp->kp.break_handler = longjmp_break_handler; return register_kprobe(&jp->kp); } void unregister_jprobe(struct jprobe *jp) { unregister_kprobe(&jp->kp); } static int __init init_kprobes(void) { int i, err = 0; /* FIXME allocate the probe table, currently defined statically */ /* initialize all list heads */ for (i = 0; i < KPROBE_TABLE_SIZE; i++) INIT_HLIST_HEAD(&kprobe_table[i]); err = register_die_notifier(&kprobe_exceptions_nb); return err; } __initcall(init_kprobes); EXPORT_SYMBOL_GPL(register_kprobe); EXPORT_SYMBOL_GPL(unregister_kprobe); EXPORT_SYMBOL_GPL(register_jprobe); EXPORT_SYMBOL_GPL(unregister_jprobe); EXPORT_SYMBOL_GPL(jprobe_return);