/*
* Kernel Probes (KProbes)
*
* Copyright (C) 2005-2006 Atmel Corporation
*
* Based on arch/ppc64/kernel/kprobes.c
* Copyright (C) IBM Corporation, 2002, 2004
*
* 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.
*/
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <asm/cacheflush.h>
#include <asm/kdebug.h>
#include <asm/ocd.h>
DEFINE_PER_CPU(struct kprobe *, current_kprobe);
static unsigned long kprobe_status;
static struct pt_regs jprobe_saved_regs;
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
int ret = 0;
if ((unsigned long)p->addr & 0x01) {
printk("Attempt to register kprobe at an unaligned address\n");
ret = -EINVAL;
}
/* XXX: Might be a good idea to check if p->addr is a valid
* kernel address as well... */
if (!ret) {
pr_debug("copy kprobe at %p\n", p->addr);
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
p->opcode = *p->addr;
}
return ret;
}
void __kprobes arch_arm_kprobe(struct kprobe *p)
{
pr_debug("arming kprobe at %p\n", p->addr);
*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)
{
pr_debug("disarming kprobe at %p\n", p->addr);
*p->addr = p->opcode;
flush_icache_range((unsigned long)p->addr,
(unsigned long)p->addr + sizeof(kprobe_opcode_t));
}
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
unsigned long dc;
pr_debug("preparing to singlestep over %p (PC=%08lx)\n",
p->addr, regs->pc);
BUG_ON(!(sysreg_read(SR) & SYSREG_BIT(SR_D)));
dc = __mfdr(DBGREG_DC);
dc |= DC_SS;
__mtdr(DBGREG_DC, dc);
/*
* We must run the instruction from its original location
* since it may actually reference PC.
*
* TODO: Do the instruction replacement directly in icache.
*/
*p->addr = p->opcode;
flush_icache_range((unsigned long)p->addr,
(unsigned long)p->addr + sizeof(kprobe_opcode_t));
}
static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
{
unsigned long dc;
pr_debug("resuming execution at PC=%08lx\n", regs->pc);
dc = __mfdr(DBGREG_DC);
dc &= ~DC_SS;
__mtdr(DBGREG_DC, dc);
*p->addr = BREAKPOINT_INSTRUCTION;
flush_icache_range((unsigned long)p->addr,
(unsigned long)p->addr + sizeof(kprobe_opcode_t));
}
static void __kprobes set_current_kprobe(struct kprobe *p)
{
__get_cpu_var(current_kprobe) = p;
}
static int __kprobes kprobe_handler(struct pt_regs *regs)
{
struct kprobe *p;
void *addr = (void *)regs->pc;
int ret = 0;
pr_debug("kprobe_handler: kprobe_running=%d\n",
kprobe_running());
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
*/
preempt_disable();
/* Check that we're not recursing */
if (kprobe_running()) {
p = get_kprobe(addr);
if (p) {
if (kprobe_status == KPROBE_HIT_SS) {
printk("FIXME: kprobe hit while single-stepping!\n");
goto no_kprobe;
}
printk("FIXME: kprobe hit while handling another kprobe\n");
goto no_kprobe;
} else {
p = kprobe_running();
if (p->break_handler && p->break_handler(p, regs))
goto ss_probe;
}
/* If it's not ours, can't be delete race, (we hold lock). */
goto no_kprobe;
}
p = get_kprobe(addr);
if (!p)
goto no_kprobe;
kprobe_status = KPROBE_HIT_ACTIVE;
set_current_kprobe(p);
if (p->pre_handler && p->pre_handler(p, regs))
/* handler has already set things up, so skip ss setup */
return 1;
ss_probe:
prepare_singlestep(p, regs);
kprobe_status = KPROBE_HIT_SS;
return 1;
no_kprobe:
return ret;
}
static int __kprobes post_kprobe_handler(struct pt_regs *regs)
{
struct kprobe *cur = kprobe_running();
pr_debug("post_kprobe_handler, cur=%p\n", cur);
if (!cur)
return 0;
if (cur->post_handler) {
kprobe_status = KPROBE_HIT_SSDONE;
cur->post_handler(cur, regs, 0);
}
resume_execution(cur, regs);
reset_current_kprobe();
preempt_enable_no_resched();
return 1;
}
static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
struct kprobe *cur = kprobe_running();
pr_debug("kprobe_fault_handler: trapnr=%d\n", trapnr);
if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
return 1;
if (kprobe_status & KPROBE_HIT_SS) {
resume_execution(cur, regs);
preempt_enable_no_resched();
}
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;
pr_debug("kprobe_exceptions_notify: val=%lu, data=%p\n",
val, data);
switch (val) {
case DIE_BREAKPOINT:
if (kprobe_handler(args->regs))
ret = NOTIFY_STOP;
break;
case DIE_SSTEP:
if (post_kprobe_handler(args->regs))
ret = NOTIFY_STOP;
break;
case DIE_FAULT:
if (kprobe_running()
&& kprobe_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
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);
memcpy(&jprobe_saved_regs, regs, sizeof(struct pt_regs));
/*
* TODO: We should probably save some of the stack here as
* well, since gcc may pass arguments on the stack for certain
* functions (lots of arguments, large aggregates, varargs)
*/
/* setup return addr to the jprobe handler routine */
regs->pc = (unsigned long)jp->entry;
return 1;
}
void __kprobes jprobe_return(void)
{
asm volatile("breakpoint" ::: "memory");
}
int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
/*
* 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, &jprobe_saved_regs, sizeof(struct pt_regs));
return 1;
}
int __init arch_init_kprobes(void)
{
printk("KPROBES: Enabling monitor mode (MM|DBE)...\n");
__mtdr(DBGREG_DC, DC_MM | DC_DBE);
/* TODO: Register kretprobe trampoline */
return 0;
}
