/*
* Kernel Probes (KProbes)
* arch/ppc64/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 contributions from
* Rusty Russell).
* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
* interface to access function arguments.
* 2004-Nov Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
* for PPC64
*/
#include <linux/config.h>
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/spinlock.h>
#include <linux/preempt.h>
#include <asm/cacheflush.h>
#include <asm/kdebug.h>
#include <asm/sstep.h>
static DECLARE_MUTEX(kprobe_mutex);
static struct kprobe *current_kprobe;
static unsigned long kprobe_status, kprobe_saved_msr;
static struct kprobe *kprobe_prev;
static unsigned long kprobe_status_prev, kprobe_saved_msr_prev;
static struct pt_regs jprobe_saved_regs;
int 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)) {
printk("Cannot register a kprobe on rfid or mtmsrd\n");
ret = -EINVAL;
}
/* insn must be on a special executable page on ppc64 */
if (!ret) {
up(&kprobe_mutex);
p->ainsn.insn = get_insn_slot();
down(&kprobe_mutex);
if (!p->ainsn.insn)
ret = -ENOMEM;
}
return ret;
}
void arch_copy_kprobe(struct kprobe *p)
{
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
p->opcode = *p->addr;
}
void 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 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 arch_remove_kprobe(struct kprobe *p)
{
up(&kprobe_mutex);
free_insn_slot(p->ainsn.insn);
down(&kprobe_mutex);
}
static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = *p->ainsn.insn;
regs->msr |= MSR_SE;
/* single step inline if it is a trap variant */
if (IS_TW(insn) || IS_TD(insn) || IS_TWI(insn) || IS_TDI(insn))
regs->nip = (unsigned long)p->addr;
else
regs->nip = (unsigned long)p->ainsn.insn;
}
static inline void save_previous_kprobe(void)
{
kprobe_prev = current_kprobe;
kprobe_status_prev = kprobe_status;
kprobe_saved_msr_prev = kprobe_saved_msr;
}
static inline void restore_previous_kprobe(void)
{
current_kprobe = kprobe_prev;
kprobe_status = kprobe_status_prev;
kprobe_saved_msr = kprobe_saved_msr_prev;
}
static inline int kprobe_handler(struct pt_regs *regs)
{
struct kprobe *p;
int ret = 0;
unsigned int *addr = (unsigned int *)regs->nip;
/* Check we're not actually recursing */
if (kprobe_running()) {
/* We *are* holding lock here, so this is safe.
Disarm the probe we just hit, and ignore it. */
p = get_kprobe(addr);
if (p) {
if (kprobe_status == KPROBE_HIT_SS) {
regs->msr &= ~MSR_SE;
regs->msr |= kprobe_saved_msr;
unlock_kprobes();
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();
current_kprobe = p;
kprobe_saved_msr = regs->msr;
p->nmissed++;
prepare_singlestep(p, regs);
kprobe_status = KPROBE_REENTER;
return 1;
} else {
p = current_kprobe;
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;
}
lock_kprobes();
p = get_kprobe(addr);
if (!p) {
unlock_kprobes();
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_TW(cur_insn) || IS_TD(cur_insn) ||
IS_TWI(cur_insn) || IS_TDI(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;
}
kprobe_status = KPROBE_HIT_ACTIVE;
current_kprobe = p;
kprobe_saved_msr = regs->msr;
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;
/*
* This preempt_disable() matches the preempt_enable_no_resched()
* in post_kprobe_handler().
*/
preempt_disable();
return 1;
no_kprobe:
return ret;
}
/*
* 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 resume_execution(struct kprobe *p, struct pt_regs *regs)
{
int ret;
unsigned int insn = *p->ainsn.insn;
regs->nip = (unsigned long)p->addr;
ret = emulate_step(regs, insn);
if (ret == 0)
regs->nip = (unsigned long)p->addr + 4;
}
static inline int post_kprobe_handler(struct pt_regs *regs)
{
if (!kprobe_running())
return 0;
if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
kprobe_status = KPROBE_HIT_SSDONE;
current_kprobe->post_handler(current_kprobe, regs, 0);
}
resume_execution(current_kprobe, regs);
regs->msr |= kprobe_saved_msr;
/*Restore back the original saved kprobes variables and continue. */
if (kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe();
goto out;
}
unlock_kprobes();
out:
preempt_enable_no_resched();
/*
* if somebody else is singlestepping across a probe point, msr
* will have SE set, in which case, continue the remaining processing
* of do_debug, as if this is not a probe hit.
*/
if (regs->msr & MSR_SE)
return 0;
return 1;
}
/* Interrupts disabled, kprobe_lock held. */
static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
if (current_kprobe->fault_handler
&& current_kprobe->fault_handler(current_kprobe, regs, trapnr))
return 1;
if (kprobe_status & KPROBE_HIT_SS) {
resume_execution(current_kprobe, regs);
regs->msr &= ~MSR_SE;
regs->msr |= kprobe_saved_msr;
unlock_kprobes();
preempt_enable_no_resched();
}
return 0;
}
/*
* Wrapper routine to for handling exceptions.
*/
int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
void *data)
{
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
/*
* Interrupts are not disabled here. We need to disable
* preemption, because kprobe_running() uses smp_processor_id().
*/
preempt_disable();
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;
case DIE_GPF:
case DIE_PAGE_FAULT:
if (kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
break;
default:
break;
}
preempt_enable();
return ret;
}
int 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));
/* setup return addr to the jprobe handler routine */
regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);
return 1;
}
void jprobe_return(void)
{
asm volatile("trap" ::: "memory");
}
void jprobe_return_end(void)
{
};
int 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;
}
