--- /dev/null
+/*
+ * arch/arm/kernel/kprobes.c
+ *
+ * Kprobes on ARM
+ *
+ * Abhishek Sagar <sagar.abhishek@gmail.com>
+ * Copyright (C) 2006, 2007 Motorola Inc.
+ *
+ * Nicolas Pitre <nico@marvell.com>
+ * Copyright (C) 2007 Marvell Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+#include <linux/module.h>
+#include <linux/stringify.h>
+#include <asm/traps.h>
+#include <asm/cacheflush.h>
+
+/*
+ * This undefined instruction must be unique and
+ * reserved solely for kprobes' use.
+ */
+#define KPROBE_BREAKPOINT_INSTRUCTION 0xe7f001f8
+
+#define MIN_STACK_SIZE(addr) \
+ min((unsigned long)MAX_STACK_SIZE, \
+ (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
+
+#define flush_insns(addr, cnt) \
+ flush_icache_range((unsigned long)(addr), \
+ (unsigned long)(addr) + \
+ sizeof(kprobe_opcode_t) * (cnt))
+
+/* Used as a marker in ARM_pc to note when we're in a jprobe. */
+#define JPROBE_MAGIC_ADDR 0xffffffff
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+ kprobe_opcode_t insn;
+ kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
+ unsigned long addr = (unsigned long)p->addr;
+ int is;
+
+ if (addr & 0x3)
+ return -EINVAL;
+
+ insn = *p->addr;
+ p->opcode = insn;
+ p->ainsn.insn = tmp_insn;
+
+ switch (arm_kprobe_decode_insn(insn, &p->ainsn)) {
+ case INSN_REJECTED: /* not supported */
+ return -EINVAL;
+
+ case INSN_GOOD: /* instruction uses slot */
+ p->ainsn.insn = get_insn_slot();
+ if (!p->ainsn.insn)
+ return -ENOMEM;
+ for (is = 0; is < MAX_INSN_SIZE; ++is)
+ p->ainsn.insn[is] = tmp_insn[is];
+ flush_insns(&p->ainsn.insn, MAX_INSN_SIZE);
+ break;
+
+ case INSN_GOOD_NO_SLOT: /* instruction doesn't need insn slot */
+ p->ainsn.insn = NULL;
+ break;
+ }
+
+ return 0;
+}
+
+void __kprobes arch_arm_kprobe(struct kprobe *p)
+{
+ *p->addr = KPROBE_BREAKPOINT_INSTRUCTION;
+ flush_insns(p->addr, 1);
+}
+
+void __kprobes arch_disarm_kprobe(struct kprobe *p)
+{
+ *p->addr = p->opcode;
+ flush_insns(p->addr, 1);
+}
+
+void __kprobes arch_remove_kprobe(struct kprobe *p)
+{
+ if (p->ainsn.insn) {
+ mutex_lock(&kprobe_mutex);
+ free_insn_slot(p->ainsn.insn, 0);
+ mutex_unlock(&kprobe_mutex);
+ 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;
+}
+
+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;
+}
+
+static void __kprobes set_current_kprobe(struct kprobe *p)
+{
+ __get_cpu_var(current_kprobe) = p;
+}
+
+static void __kprobes singlestep(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb)
+{
+ regs->ARM_pc += 4;
+ p->ainsn.insn_handler(p, regs);
+}
+
+/*
+ * Called with IRQs disabled. IRQs must remain disabled from that point
+ * all the way until processing this kprobe is complete. The current
+ * kprobes implementation cannot process more than one nested level of
+ * kprobe, and that level is reserved for user kprobe handlers, so we can't
+ * risk encountering a new kprobe in an interrupt handler.
+ */
+void __kprobes kprobe_handler(struct pt_regs *regs)
+{
+ struct kprobe *p, *cur;
+ struct kprobe_ctlblk *kcb;
+ kprobe_opcode_t *addr = (kprobe_opcode_t *)regs->ARM_pc;
+
+ kcb = get_kprobe_ctlblk();
+ cur = kprobe_running();
+ p = get_kprobe(addr);
+
+ if (p) {
+ if (cur) {
+ /* Kprobe is pending, so we're recursing. */
+ switch (kcb->kprobe_status) {
+ case KPROBE_HIT_ACTIVE:
+ case KPROBE_HIT_SSDONE:
+ /* A pre- or post-handler probe got us here. */
+ kprobes_inc_nmissed_count(p);
+ save_previous_kprobe(kcb);
+ set_current_kprobe(p);
+ kcb->kprobe_status = KPROBE_REENTER;
+ singlestep(p, regs, kcb);
+ restore_previous_kprobe(kcb);
+ break;
+ default:
+ /* impossible cases */
+ BUG();
+ }
+ } else {
+ set_current_kprobe(p);
+ 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,
+ * so get out doing nothing more here.
+ */
+ if (!p->pre_handler || !p->pre_handler(p, regs)) {
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ singlestep(p, regs, kcb);
+ if (p->post_handler) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ p->post_handler(p, regs, 0);
+ }
+ reset_current_kprobe();
+ }
+ }
+ } else if (cur) {
+ /* We probably hit a jprobe. Call its break handler. */
+ if (cur->break_handler && cur->break_handler(cur, regs)) {
+ kcb->kprobe_status = KPROBE_HIT_SS;
+ singlestep(cur, regs, kcb);
+ if (cur->post_handler) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ cur->post_handler(cur, regs, 0);
+ }
+ }
+ reset_current_kprobe();
+ } else {
+ /*
+ * The probe was removed and a race is in progress.
+ * There is nothing we can do about it. Let's restart
+ * the instruction. By the time we can restart, the
+ * real instruction will be there.
+ */
+ }
+}
+
+static int kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
+{
+ kprobe_handler(regs);
+ return 0;
+}
+
+int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr)
+{
+ 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 PC to point back to the probe address
+ * and allow the page fault handler to continue as a
+ * normal page fault.
+ */
+ regs->ARM_pc = (long)cur->addr;
+ if (kcb->kprobe_status == KPROBE_REENTER) {
+ restore_previous_kprobe(kcb);
+ } else {
+ reset_current_kprobe();
+ }
+ 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.
+ */
+ if (cur->fault_handler && cur->fault_handler(cur, regs, fsr))
+ return 1;
+ break;
+
+ default:
+ break;
+ }
+
+ return 0;
+}
+
+int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ /*
+ * notify_die() is currently never called on ARM,
+ * so this callback is currently empty.
+ */
+ return NOTIFY_DONE;
+}
+
+/*
+ * When a retprobed function returns, trampoline_handler() is called,
+ * calling the kretprobe's handler. We construct a struct pt_regs to
+ * give a view of registers r0-r11 to the user return-handler. This is
+ * not a complete pt_regs structure, but that should be plenty sufficient
+ * for kretprobe handlers which should normally be interested in r0 only
+ * anyway.
+ */
+static void __attribute__((naked)) __kprobes kretprobe_trampoline(void)
+{
+ __asm__ __volatile__ (
+ "stmdb sp!, {r0 - r11} \n\t"
+ "mov r0, sp \n\t"
+ "bl trampoline_handler \n\t"
+ "mov lr, r0 \n\t"
+ "ldmia sp!, {r0 - r11} \n\t"
+ "mov pc, lr \n\t"
+ : : : "memory");
+}
+
+/* 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;
+
+ INIT_HLIST_HEAD(&empty_rp);
+ spin_lock_irqsave(&kretprobe_lock, flags);
+ head = kretprobe_inst_table_head(current);
+
+ /*
+ * It is possible to have multiple instances associated with a given
+ * task either because multiple functions in the call path have
+ * a return probe installed on them, and/or more than one 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 with kretprobe_lock held. */
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
+ struct pt_regs *regs)
+{
+ ri->ret_addr = (kprobe_opcode_t *)regs->ARM_lr;
+
+ /* Replace the return addr with trampoline addr. */
+ regs->ARM_lr = (unsigned long)&kretprobe_trampoline;
+}
+
+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();
+ long sp_addr = regs->ARM_sp;
+
+ kcb->jprobe_saved_regs = *regs;
+ memcpy(kcb->jprobes_stack, (void *)sp_addr, MIN_STACK_SIZE(sp_addr));
+ regs->ARM_pc = (long)jp->entry;
+ regs->ARM_cpsr |= PSR_I_BIT;
+ preempt_disable();
+ return 1;
+}
+
+void __kprobes jprobe_return(void)
+{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+ __asm__ __volatile__ (
+ /*
+ * Setup an empty pt_regs. Fill SP and PC fields as
+ * they're needed by longjmp_break_handler.
+ */
+ "sub sp, %0, %1 \n\t"
+ "ldr r0, ="__stringify(JPROBE_MAGIC_ADDR)"\n\t"
+ "str %0, [sp, %2] \n\t"
+ "str r0, [sp, %3] \n\t"
+ "mov r0, sp \n\t"
+ "bl kprobe_handler \n\t"
+
+ /*
+ * Return to the context saved by setjmp_pre_handler
+ * and restored by longjmp_break_handler.
+ */
+ "ldr r0, [sp, %4] \n\t"
+ "msr cpsr_cxsf, r0 \n\t"
+ "ldmia sp, {r0 - pc} \n\t"
+ :
+ : "r" (kcb->jprobe_saved_regs.ARM_sp),
+ "I" (sizeof(struct pt_regs)),
+ "J" (offsetof(struct pt_regs, ARM_sp)),
+ "J" (offsetof(struct pt_regs, ARM_pc)),
+ "J" (offsetof(struct pt_regs, ARM_cpsr))
+ : "memory", "cc");
+}
+
+int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+ long stack_addr = kcb->jprobe_saved_regs.ARM_sp;
+ long orig_sp = regs->ARM_sp;
+ struct jprobe *jp = container_of(p, struct jprobe, kp);
+
+ if (regs->ARM_pc == JPROBE_MAGIC_ADDR) {
+ if (orig_sp != stack_addr) {
+ struct pt_regs *saved_regs =
+ (struct pt_regs *)kcb->jprobe_saved_regs.ARM_sp;
+ printk("current sp %lx does not match saved sp %lx\n",
+ orig_sp, stack_addr);
+ printk("Saved registers for jprobe %p\n", jp);
+ show_regs(saved_regs);
+ printk("Current registers\n");
+ show_regs(regs);
+ BUG();
+ }
+ *regs = kcb->jprobe_saved_regs;
+ memcpy((void *)stack_addr, kcb->jprobes_stack,
+ MIN_STACK_SIZE(stack_addr));
+ preempt_enable_no_resched();
+ return 1;
+ }
+ return 0;
+}
+
+static struct undef_hook kprobes_break_hook = {
+ .instr_mask = 0xffffffff,
+ .instr_val = KPROBE_BREAKPOINT_INSTRUCTION,
+ .cpsr_mask = MODE_MASK,
+ .cpsr_val = SVC_MODE,
+ .fn = kprobe_trap_handler,
+};
+
+int __init arch_init_kprobes()
+{
+ arm_kprobe_decode_init();
+ register_undef_hook(&kprobes_break_hook);
+ return 0;
+}
projects / linux-beck.git / commitdiff