[net-next-2.6.git] / arch / s390 / kernel / kprobes.c

/*
 *  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, 2006
 *
 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
 */

#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/preempt.h>
#include <linux/stop_machine.h>
#include <linux/kdebug.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/sections.h>
#include <linux/module.h>
#include <linux/slab.h>

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)
{
	/* Make sure the probe isn't going on a difficult instruction */
	if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
		return -EINVAL;

	if ((unsigned long)p->addr & 0x01)
		return -EINVAL;

	/* Use the get_insn_slot() facility for correctness */
	if (!(p->ainsn.insn = get_insn_slot()))
		return -ENOMEM;

	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));

	get_instruction_type(&p->ainsn);
	p->opcode = *p->addr;
	return 0;
}

int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
{
	switch (*(__u8 *) instruction) {
	case 0x0c:	/* bassm */
	case 0x0b:	/* bsm	 */
	case 0x83:	/* diag  */
	case 0x44:	/* ex	 */
	case 0xac:	/* stnsm */
	case 0xad:	/* stosm */
		return -EINVAL;
	}
	switch (*(__u16 *) instruction) {
	case 0x0101:	/* pr	 */
	case 0xb25a:	/* bsa	 */
	case 0xb240:	/* bakr  */
	case 0xb258:	/* bsg	 */
	case 0xb218:	/* pc	 */
	case 0xb228:	/* pt	 */
	case 0xb98d:	/* epsw	 */
		return -EINVAL;
	}
	return 0;
}

void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
{
	/* default fixup method */
	ainsn->fixup = FIXUP_PSW_NORMAL;

	/* save r1 operand */
	ainsn->reg = (*ainsn->insn & 0xf0) >> 4;

	/* save the instruction length (pop 5-5) in bytes */
	switch (*(__u8 *) (ainsn->insn) >> 6) {
	case 0:
		ainsn->ilen = 2;
		break;
	case 1:
	case 2:
		ainsn->ilen = 4;
		break;
	case 3:
		ainsn->ilen = 6;
		break;
	}

	switch (*(__u8 *) ainsn->insn) {
	case 0x05:	/* balr	*/
	case 0x0d:	/* basr */
		ainsn->fixup = FIXUP_RETURN_REGISTER;
		/* if r2 = 0, no branch will be taken */
		if ((*ainsn->insn & 0x0f) == 0)
			ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN;
		break;
	case 0x06:	/* bctr	*/
	case 0x07:	/* bcr	*/
		ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
		break;
	case 0x45:	/* bal	*/
	case 0x4d:	/* bas	*/
		ainsn->fixup = FIXUP_RETURN_REGISTER;
		break;
	case 0x47:	/* bc	*/
	case 0x46:	/* bct	*/
	case 0x86:	/* bxh	*/
	case 0x87:	/* bxle	*/
		ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
		break;
	case 0x82:	/* lpsw	*/
		ainsn->fixup = FIXUP_NOT_REQUIRED;
		break;
	case 0xb2:	/* lpswe */
		if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) {
			ainsn->fixup = FIXUP_NOT_REQUIRED;
		}
		break;
	case 0xa7:	/* bras	*/
		if ((*ainsn->insn & 0x0f) == 0x05) {
			ainsn->fixup |= FIXUP_RETURN_REGISTER;
		}
		break;
	case 0xc0:
		if ((*ainsn->insn & 0x0f) == 0x00  /* larl  */
			|| (*ainsn->insn & 0x0f) == 0x05) /* brasl */
		ainsn->fixup |= FIXUP_RETURN_REGISTER;
		break;
	case 0xeb:
		if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 ||	/* bxhg  */
			*(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */
			ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
		}
		break;
	case 0xe3:	/* bctg	*/
		if (*(((__u8 *) ainsn->insn) + 5) == 0x46) {
			ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
		}
		break;
	}
}

static int __kprobes swap_instruction(void *aref)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	unsigned long status = kcb->kprobe_status;
	struct ins_replace_args *args = aref;
	int rc;

	kcb->kprobe_status = KPROBE_SWAP_INST;
	rc = probe_kernel_write(args->ptr, &args->new, sizeof(args->new));
	kcb->kprobe_status = status;
	return rc;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
	struct ins_replace_args args;

	args.ptr = p->addr;
	args.old = p->opcode;
	args.new = BREAKPOINT_INSTRUCTION;
	stop_machine(swap_instruction, &args, NULL);
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
	struct ins_replace_args args;

	args.ptr = p->addr;
	args.old = BREAKPOINT_INSTRUCTION;
	args.new = p->opcode;
	stop_machine(swap_instruction, &args, NULL);
}

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)
{
	per_cr_bits kprobe_per_regs[1];

	memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
	regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;

	/* Set up the per control reg info, will pass to lctl */
	kprobe_per_regs[0].em_instruction_fetch = 1;
	kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
	kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;

	/* Set the PER control regs, turns on single step for this address */
	__ctl_load(kprobe_per_regs, 9, 11);
	regs->psw.mask |= PSW_MASK_PER;
	regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
}

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.kprobe_saved_imask = kcb->kprobe_saved_imask;
	memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
					sizeof(kcb->kprobe_saved_ctl));
}

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_imask = kcb->prev_kprobe.kprobe_saved_imask;
	memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
					sizeof(kcb->kprobe_saved_ctl));
}

static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
						struct kprobe_ctlblk *kcb)
{
	__get_cpu_var(current_kprobe) = p;
	/* Save the interrupt and per flags */
	kcb->kprobe_saved_imask = regs->psw.mask &
	    (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK);
	/* Save the control regs that govern PER */
	__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
}

void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
					struct pt_regs *regs)
{
	ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];

	/* Replace the return addr with trampoline addr */
	regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
}

static int __kprobes kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *p;
	int ret = 0;
	unsigned long *addr = (unsigned long *)
		((regs->psw.addr & PSW_ADDR_INSN) - 2);
	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) {
			if (kcb->kprobe_status == KPROBE_HIT_SS &&
			    *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
				regs->psw.mask &= ~PSW_MASK_PER;
				regs->psw.mask |= kcb->kprobe_saved_imask;
				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);
			kprobes_inc_nmissed_count(p);
			prepare_singlestep(p, regs);
			kcb->kprobe_status = KPROBE_REENTER;
			return 1;
		} else {
			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)
		/*
		 * No kprobe at this address. The fault has not been
		 * caused by a kprobe breakpoint. The race of breakpoint
		 * vs. kprobe remove does not exist because on s390 we
		 * use stop_machine to arm/disarm the breakpoints.
		 */
		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 (regs->psw.mask & (PSW_MASK_PER | PSW_MASK_IO))
		local_irq_disable();
	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: bcr 0,0\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->psw.addr = orig_ret_address | PSW_ADDR_AMODE;

	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 void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	regs->psw.addr &= PSW_ADDR_INSN;

	if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
		regs->psw.addr = (unsigned long)p->addr +
				((unsigned long)regs->psw.addr -
				 (unsigned long)p->ainsn.insn);

	if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
		if ((unsigned long)regs->psw.addr -
		    (unsigned long)p->ainsn.insn == p->ainsn.ilen)
			regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;

	if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
		regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
						(regs->gprs[p->ainsn.reg] -
						(unsigned long)p->ainsn.insn))
						| PSW_ADDR_AMODE;

	regs->psw.addr |= PSW_ADDR_AMODE;
	/* turn off PER mode */
	regs->psw.mask &= ~PSW_MASK_PER;
	/* Restore the original per control regs */
	__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
	regs->psw.mask |= kcb->kprobe_saved_imask;
}

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;

	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
		kcb->kprobe_status = KPROBE_HIT_SSDONE;
		cur->post_handler(cur, regs, 0);
	}

	resume_execution(cur, regs);

	/*Restore back the original saved kprobes variables and continue. */
	if (kcb->kprobe_status == KPROBE_REENTER) {
		restore_previous_kprobe(kcb);
		goto out;
	}
	reset_current_kprobe();
	if (regs->psw.mask & (PSW_MASK_PER | PSW_MASK_IO))
		local_irq_enable();
out:
	preempt_enable_no_resched();

	/*
	 * if somebody else is singlestepping across a probe point, psw mask
	 * will have PER set, in which case, continue the remaining processing
	 * of do_single_step, as if this is not a probe hit.
	 */
	if (regs->psw.mask & PSW_MASK_PER) {
		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_SWAP_INST:
		/* We are here because the instruction replacement failed */
		return 0;
	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->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
		regs->psw.mask &= ~PSW_MASK_PER;
		regs->psw.mask |= kcb->kprobe_saved_imask;
		if (kcb->kprobe_status == KPROBE_REENTER)
			restore_previous_kprobe(kcb);
		else {
			reset_current_kprobe();
			if (regs->psw.mask & (PSW_MASK_PER | PSW_MASK_IO))
				local_irq_enable();
		}
		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.
		 */
		entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
		if (entry) {
			regs->psw.addr = entry->fixup | PSW_ADDR_AMODE;
			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;

	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_TRAP:
		/* kprobe_running() needs smp_processor_id() */
		preempt_disable();
		if (kprobe_running() &&
		    kprobe_fault_handler(args->regs, args->trapnr))
			ret = NOTIFY_STOP;
		preempt_enable();
		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);
	unsigned long addr;
	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->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;

	/* r14 is the function return address */
	kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
	/* r15 is the stack pointer */
	kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
	addr = (unsigned long)kcb->jprobe_saved_r15;

	memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
	       MIN_STACK_SIZE(addr));
	return 1;
}

void __kprobes jprobe_return(void)
{
	asm volatile(".word 0x0002");
}

void __kprobes jprobe_return_end(void)
{
	asm volatile("bcr 0,0");
}

int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);

	/* Put the regs back */
	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
	/* put the stack back */
	memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
	       MIN_STACK_SIZE(stack_addr));
	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;
}
Commit	Line	Data
4ba069b8 MG	1	/*
	2	* Kernel Probes (KProbes)
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; if not, write to the Free Software
	16	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	17	*
	18	* Copyright (C) IBM Corporation, 2002, 2006
	19	*
	20	* s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
	21	*/
	22
4ba069b8 MG	23	#include <linux/kprobes.h>
	24	#include <linux/ptrace.h>
	25	#include <linux/preempt.h>
	26	#include <linux/stop_machine.h>
1eeb66a1	27	#include <linux/kdebug.h>
a2b53673	28	#include <linux/uaccess.h>
4ba069b8	29	#include <asm/cacheflush.h>
4ba069b8	30	#include <asm/sections.h>
4ba069b8	31	#include <linux/module.h>
5a0e3ad6	32	#include <linux/slab.h>
4ba069b8 MG	33
	34	DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
	35	DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
	36
f438d914 MH	37	struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
f438d914 MH	38
4ba069b8 MG	39	int __kprobes arch_prepare_kprobe(struct kprobe *p)
	40	{
	41	/* Make sure the probe isn't going on a difficult instruction */
	42	if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
	43	return -EINVAL;
	44
5532bd0f	45	if ((unsigned long)p->addr & 0x01)
4ba069b8	46	return -EINVAL;
4ba069b8 MG	47
	48	/* Use the get_insn_slot() facility for correctness */
	49	if (!(p->ainsn.insn = get_insn_slot()))
	50	return -ENOMEM;
	51
	52	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
	53
	54	get_instruction_type(&p->ainsn);
	55	p->opcode = *p->addr;
	56	return 0;
	57	}
	58
	59	int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
	60	{
	61	switch ((__u8 ) instruction) {
	62	case 0x0c: /* bassm */
	63	case 0x0b: /* bsm */
	64	case 0x83: /* diag */
	65	case 0x44: /* ex */
bac9f154 HC	66	case 0xac: /* stnsm */
bac9f154 HC	67	case 0xad: /* stosm */
4ba069b8 MG	68	return -EINVAL;
	69	}
	70	switch ((__u16 ) instruction) {
	71	case 0x0101: /* pr */
	72	case 0xb25a: /* bsa */
	73	case 0xb240: /* bakr */
	74	case 0xb258: /* bsg */
	75	case 0xb218: /* pc */
	76	case 0xb228: /* pt */
bac9f154	77	case 0xb98d: /* epsw */
4ba069b8 MG	78	return -EINVAL;
	79	}
	80	return 0;
	81	}
	82
	83	void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
	84	{
	85	/* default fixup method */
	86	ainsn->fixup = FIXUP_PSW_NORMAL;
	87
	88	/* save r1 operand */
	89	ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
	90
	91	/* save the instruction length (pop 5-5) in bytes */
9c5f225f	92	switch ((__u8 ) (ainsn->insn) >> 6) {
4ba069b8 MG	93	case 0:
	94	ainsn->ilen = 2;
	95	break;
	96	case 1:
	97	case 2:
	98	ainsn->ilen = 4;
	99	break;
	100	case 3:
	101	ainsn->ilen = 6;
	102	break;
	103	}
	104
	105	switch ((__u8 ) ainsn->insn) {
	106	case 0x05: /* balr */
	107	case 0x0d: /* basr */
	108	ainsn->fixup = FIXUP_RETURN_REGISTER;
	109	/* if r2 = 0, no branch will be taken */
	110	if ((*ainsn->insn & 0x0f) == 0)
	111	ainsn->fixup \|= FIXUP_BRANCH_NOT_TAKEN;
	112	break;
	113	case 0x06: /* bctr */
	114	case 0x07: /* bcr */
	115	ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
	116	break;
	117	case 0x45: /* bal */
	118	case 0x4d: /* bas */
	119	ainsn->fixup = FIXUP_RETURN_REGISTER;
	120	break;
	121	case 0x47: /* bc */
	122	case 0x46: /* bct */
	123	case 0x86: /* bxh */
	124	case 0x87: /* bxle */
	125	ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
	126	break;
	127	case 0x82: /* lpsw */
	128	ainsn->fixup = FIXUP_NOT_REQUIRED;
	129	break;
	130	case 0xb2: /* lpswe */
	131	if ((((__u8 ) ainsn->insn) + 1) == 0xb2) {
	132	ainsn->fixup = FIXUP_NOT_REQUIRED;
	133	}
	134	break;
	135	case 0xa7: /* bras */
	136	if ((*ainsn->insn & 0x0f) == 0x05) {
	137	ainsn->fixup \|= FIXUP_RETURN_REGISTER;
	138	}
	139	break;
	140	case 0xc0:
	141	if ((ainsn->insn & 0x0f) == 0x00 / larl */
	142	\|\| (ainsn->insn & 0x0f) == 0x05) / brasl */
	143	ainsn->fixup \|= FIXUP_RETURN_REGISTER;
	144	break;
	145	case 0xeb:
	146	if ((((__u8 ) ainsn->insn) + 5 ) == 0x44 \|\| /* bxhg */
	147	(((__u8 ) ainsn->insn) + 5) == 0x45) {/* bxleg */
	148	ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
	149	}
	150	break;
	151	case 0xe3: /* bctg */
	152	if ((((__u8 ) ainsn->insn) + 5) == 0x46) {
	153	ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
	154	}
	155	break;
	156	}
157	}
158
159	static int __kprobes swap_instruction(void *aref)
160	{
acf01800 HC	161	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
acf01800 HC	162	unsigned long status = kcb->kprobe_status;
4ba069b8	163	struct ins_replace_args *args = aref;
acf01800	164	int rc;
a2b53673	165
acf01800 HC	166	kcb->kprobe_status = KPROBE_SWAP_INST;
	167	rc = probe_kernel_write(args->ptr, &args->new, sizeof(args->new));
	168	kcb->kprobe_status = status;
	169	return rc;
4ba069b8 MG	170	}
	171
	172	void __kprobes arch_arm_kprobe(struct kprobe *p)
	173	{
4ba069b8 MG	174	struct ins_replace_args args;
	175
	176	args.ptr = p->addr;
	177	args.old = p->opcode;
	178	args.new = BREAKPOINT_INSTRUCTION;
9b1a4d38	179	stop_machine(swap_instruction, &args, NULL);
4ba069b8 MG	180	}
	181
	182	void __kprobes arch_disarm_kprobe(struct kprobe *p)
	183	{
4ba069b8 MG	184	struct ins_replace_args args;
	185
	186	args.ptr = p->addr;
	187	args.old = BREAKPOINT_INSTRUCTION;
	188	args.new = p->opcode;
9b1a4d38	189	stop_machine(swap_instruction, &args, NULL);
4ba069b8 MG	190	}
	191
	192	void __kprobes arch_remove_kprobe(struct kprobe *p)
	193	{
12941560 MH	194	if (p->ainsn.insn) {
	195	free_insn_slot(p->ainsn.insn, 0);
	196	p->ainsn.insn = NULL;
	197	}
4ba069b8 MG	198	}
	199
	200	static void __kprobes prepare_singlestep(struct kprobe p, struct pt_regs regs)
	201	{
	202	per_cr_bits kprobe_per_regs[1];
	203
	204	memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
	205	regs->psw.addr = (unsigned long)p->ainsn.insn \| PSW_ADDR_AMODE;
	206
	207	/* Set up the per control reg info, will pass to lctl */
	208	kprobe_per_regs[0].em_instruction_fetch = 1;
	209	kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
	210	kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
	211
	212	/* Set the PER control regs, turns on single step for this address */
	213	__ctl_load(kprobe_per_regs, 9, 11);
	214	regs->psw.mask \|= PSW_MASK_PER;
	215	regs->psw.mask &= ~(PSW_MASK_IO \| PSW_MASK_EXT \| PSW_MASK_MCHECK);
	216	}
	217
	218	static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
	219	{
	220	kcb->prev_kprobe.kp = kprobe_running();
	221	kcb->prev_kprobe.status = kcb->kprobe_status;
	222	kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
	223	memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
	224	sizeof(kcb->kprobe_saved_ctl));
	225	}
	226
	227	static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
	228	{
	229	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
	230	kcb->kprobe_status = kcb->prev_kprobe.status;
	231	kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
	232	memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
	233	sizeof(kcb->kprobe_saved_ctl));
	234	}
	235
	236	static void __kprobes set_current_kprobe(struct kprobe p, struct pt_regs regs,
	237	struct kprobe_ctlblk *kcb)
	238	{
	239	__get_cpu_var(current_kprobe) = p;
	240	/* Save the interrupt and per flags */
	241	kcb->kprobe_saved_imask = regs->psw.mask &
	242	(PSW_MASK_PER \| PSW_MASK_IO \| PSW_MASK_EXT \| PSW_MASK_MCHECK);
	243	/* Save the control regs that govern PER */
	244	__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
	245	}
	246
4c4308cb	247	void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
4ba069b8 MG	248	struct pt_regs *regs)
4ba069b8 MG	249	{
4c4308cb	250	ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
4ba069b8	251
4c4308cb CH	252	/* Replace the return addr with trampoline addr */
4c4308cb CH	253	regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
4ba069b8 MG	254	}
	255
	256	static int __kprobes kprobe_handler(struct pt_regs *regs)
	257	{
	258	struct kprobe *p;
	259	int ret = 0;
	260	unsigned long addr = (unsigned long )
	261	((regs->psw.addr & PSW_ADDR_INSN) - 2);
	262	struct kprobe_ctlblk *kcb;
	263
	264	/*
	265	* We don't want to be preempted for the entire
	266	* duration of kprobe processing
	267	*/
	268	preempt_disable();
	269	kcb = get_kprobe_ctlblk();
	270
	271	/* Check we're not actually recursing */
	272	if (kprobe_running()) {
	273	p = get_kprobe(addr);
	274	if (p) {
	275	if (kcb->kprobe_status == KPROBE_HIT_SS &&
	276	*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
	277	regs->psw.mask &= ~PSW_MASK_PER;
	278	regs->psw.mask \|= kcb->kprobe_saved_imask;
	279	goto no_kprobe;
	280	}
	281	/* We have reentered the kprobe_handler(), since
	282	* another probe was hit while within the handler.
	283	* We here save the original kprobes variables and
	284	* just single step on the instruction of the new probe
	285	* without calling any user handlers.
	286	*/
	287	save_previous_kprobe(kcb);
	288	set_current_kprobe(p, regs, kcb);
	289	kprobes_inc_nmissed_count(p);
	290	prepare_singlestep(p, regs);
	291	kcb->kprobe_status = KPROBE_REENTER;
	292	return 1;
	293	} else {
	294	p = __get_cpu_var(current_kprobe);
	295	if (p->break_handler && p->break_handler(p, regs)) {
	296	goto ss_probe;
	297	}
	298	}
	299	goto no_kprobe;
	300	}
	301
	302	p = get_kprobe(addr);
f794c827 MS	303	if (!p)
	304	/*
	305	* No kprobe at this address. The fault has not been
	306	* caused by a kprobe breakpoint. The race of breakpoint
	307	* vs. kprobe remove does not exist because on s390 we
9b1a4d38	308	* use stop_machine to arm/disarm the breakpoints.
f794c827	309	*/
4ba069b8	310	goto no_kprobe;
4ba069b8 MG	311
	312	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
	313	set_current_kprobe(p, regs, kcb);
	314	if (p->pre_handler && p->pre_handler(p, regs))
	315	/* handler has already set things up, so skip ss setup */
	316	return 1;
	317
	318	ss_probe:
9ec27080 MS	319	if (regs->psw.mask & (PSW_MASK_PER \| PSW_MASK_IO))
9ec27080 MS	320	local_irq_disable();
4ba069b8 MG	321	prepare_singlestep(p, regs);
	322	kcb->kprobe_status = KPROBE_HIT_SS;
	323	return 1;
	324
	325	no_kprobe:
	326	preempt_enable_no_resched();
	327	return ret;
	328	}
	329
	330	/*
	331	* Function return probe trampoline:
	332	* - init_kprobes() establishes a probepoint here
	333	* - When the probed function returns, this probe
	334	* causes the handlers to fire
	335	*/
a806170e	336	static void __used kretprobe_trampoline_holder(void)
4ba069b8 MG	337	{
	338	asm volatile(".global kretprobe_trampoline\n"
	339	"kretprobe_trampoline: bcr 0,0\n");
	340	}
	341
	342	/*
	343	* Called when the probe at kretprobe trampoline is hit
	344	*/
2b67fc46 HC	345	static int __kprobes trampoline_probe_handler(struct kprobe *p,
2b67fc46 HC	346	struct pt_regs *regs)
4ba069b8 MG	347	{
4ba069b8 MG	348	struct kretprobe_instance *ri = NULL;
99219a3f	349	struct hlist_head *head, empty_rp;
4ba069b8 MG	350	struct hlist_node node, tmp;
	351	unsigned long flags, orig_ret_address = 0;
	352	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
	353
99219a3f	354	INIT_HLIST_HEAD(&empty_rp);
ef53d9c5	355	kretprobe_hash_lock(current, &head, &flags);
4ba069b8 MG	356
	357	/*
	358	* It is possible to have multiple instances associated with a given
	359	* task either because an multiple functions in the call path
025dfdaf	360	* have a return probe installed on them, and/or more than one return
4ba069b8 MG	361	* return probe was registered for a target function.
	362	*
	363	* We can handle this because:
	364	* - instances are always inserted at the head of the list
	365	* - when multiple return probes are registered for the same
	366	* function, the first instance's ret_addr will point to the
	367	* real return address, and all the rest will point to
	368	* kretprobe_trampoline
	369	*/
	370	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
	371	if (ri->task != current)
	372	/* another task is sharing our hash bucket */
	373	continue;
	374
	375	if (ri->rp && ri->rp->handler)
	376	ri->rp->handler(ri, regs);
	377
	378	orig_ret_address = (unsigned long)ri->ret_addr;
99219a3f	379	recycle_rp_inst(ri, &empty_rp);
4ba069b8 MG	380
	381	if (orig_ret_address != trampoline_address) {
	382	/*
	383	* This is the real return address. Any other
	384	* instances associated with this task are for
	385	* other calls deeper on the call stack
	386	*/
	387	break;
	388	}
	389	}
a5a60a2b	390	kretprobe_assert(ri, orig_ret_address, trampoline_address);
4ba069b8 MG	391	regs->psw.addr = orig_ret_address \| PSW_ADDR_AMODE;
	392
	393	reset_current_kprobe();
ef53d9c5	394	kretprobe_hash_unlock(current, &flags);
4ba069b8 MG	395	preempt_enable_no_resched();
4ba069b8 MG	396
99219a3f	397	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
	398	hlist_del(&ri->hlist);
	399	kfree(ri);
	400	}
4ba069b8 MG	401	/*
	402	* By returning a non-zero value, we are telling
	403	* kprobe_handler() that we don't want the post_handler
	404	* to run (and have re-enabled preemption)
	405	*/
	406	return 1;
	407	}
	408
	409	/*
	410	* Called after single-stepping. p->addr is the address of the
	411	* instruction whose first byte has been replaced by the "breakpoint"
	412	* instruction. To avoid the SMP problems that can occur when we
	413	* temporarily put back the original opcode to single-step, we
	414	* single-stepped a copy of the instruction. The address of this
	415	* copy is p->ainsn.insn.
	416	*/
	417	static void __kprobes resume_execution(struct kprobe p, struct pt_regs regs)
	418	{
	419	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	420
	421	regs->psw.addr &= PSW_ADDR_INSN;
	422
	423	if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
	424	regs->psw.addr = (unsigned long)p->addr +
	425	((unsigned long)regs->psw.addr -
	426	(unsigned long)p->ainsn.insn);
	427
	428	if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
	429	if ((unsigned long)regs->psw.addr -
	430	(unsigned long)p->ainsn.insn == p->ainsn.ilen)
	431	regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
	432
	433	if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
	434	regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
	435	(regs->gprs[p->ainsn.reg] -
	436	(unsigned long)p->ainsn.insn))
	437	\| PSW_ADDR_AMODE;
	438
	439	regs->psw.addr \|= PSW_ADDR_AMODE;
	440	/* turn off PER mode */
	441	regs->psw.mask &= ~PSW_MASK_PER;
	442	/* Restore the original per control regs */
	443	__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
	444	regs->psw.mask \|= kcb->kprobe_saved_imask;
	445	}
	446
	447	static int __kprobes post_kprobe_handler(struct pt_regs *regs)
	448	{
	449	struct kprobe *cur = kprobe_running();
	450	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	451
	452	if (!cur)
	453	return 0;
	454
	455	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
	456	kcb->kprobe_status = KPROBE_HIT_SSDONE;
	457	cur->post_handler(cur, regs, 0);
	458	}
	459
	460	resume_execution(cur, regs);
	461
	462	/Restore back the original saved kprobes variables and continue. /
	463	if (kcb->kprobe_status == KPROBE_REENTER) {
	464	restore_previous_kprobe(kcb);
465	goto out;
466	}
467	reset_current_kprobe();
9ec27080 MS	468	if (regs->psw.mask & (PSW_MASK_PER \| PSW_MASK_IO))
9ec27080 MS	469	local_irq_enable();
4ba069b8 MG	470	out:
	471	preempt_enable_no_resched();
	472
	473	/*
	474	* if somebody else is singlestepping across a probe point, psw mask
	475	* will have PER set, in which case, continue the remaining processing
	476	* of do_single_step, as if this is not a probe hit.
	477	*/
	478	if (regs->psw.mask & PSW_MASK_PER) {
	479	return 0;
	480	}
	481
	482	return 1;
	483	}
	484
33464e3b	485	int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
4ba069b8 MG	486	{
	487	struct kprobe *cur = kprobe_running();
	488	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	489	const struct exception_table_entry *entry;
	490
	491	switch(kcb->kprobe_status) {
	492	case KPROBE_SWAP_INST:
	493	/* We are here because the instruction replacement failed */
	494	return 0;
	495	case KPROBE_HIT_SS:
	496	case KPROBE_REENTER:
	497	/*
	498	* We are here because the instruction being single
	499	* stepped caused a page fault. We reset the current
	500	* kprobe and the nip points back to the probe address
	501	* and allow the page fault handler to continue as a
	502	* normal page fault.
	503	*/
	504	regs->psw.addr = (unsigned long)cur->addr \| PSW_ADDR_AMODE;
	505	regs->psw.mask &= ~PSW_MASK_PER;
	506	regs->psw.mask \|= kcb->kprobe_saved_imask;
	507	if (kcb->kprobe_status == KPROBE_REENTER)
	508	restore_previous_kprobe(kcb);
9ec27080	509	else {
4ba069b8	510	reset_current_kprobe();
9ec27080 MS	511	if (regs->psw.mask & (PSW_MASK_PER \| PSW_MASK_IO))
	512	local_irq_enable();
	513	}
4ba069b8 MG	514	preempt_enable_no_resched();
	515	break;
	516	case KPROBE_HIT_ACTIVE:
	517	case KPROBE_HIT_SSDONE:
	518	/*
	519	* We increment the nmissed count for accounting,
	520	* we can also use npre/npostfault count for accouting
	521	* these specific fault cases.
	522	*/
	523	kprobes_inc_nmissed_count(cur);
	524
	525	/*
	526	* We come here because instructions in the pre/post
	527	* handler caused the page_fault, this could happen
	528	* if handler tries to access user space by
	529	* copy_from_user(), get_user() etc. Let the
	530	* user-specified handler try to fix it first.
	531	*/
	532	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
	533	return 1;
	534
	535	/*
	536	* In case the user-specified fault handler returned
	537	* zero, try to fix up.
	538	*/
	539	entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
	540	if (entry) {
	541	regs->psw.addr = entry->fixup \| PSW_ADDR_AMODE;
	542	return 1;
	543	}
	544
	545	/*
	546	* fixup_exception() could not handle it,
	547	* Let do_page_fault() fix it.
	548	*/
	549	break;
	550	default:
	551	break;
	552	}
	553	return 0;
	554	}
	555
	556	/*
	557	* Wrapper routine to for handling exceptions.
	558	*/
	559	int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
	560	unsigned long val, void *data)
	561	{
	562	struct die_args args = (struct die_args )data;
	563	int ret = NOTIFY_DONE;
	564
	565	switch (val) {
	566	case DIE_BPT:
	567	if (kprobe_handler(args->regs))
	568	ret = NOTIFY_STOP;
	569	break;
	570	case DIE_SSTEP:
	571	if (post_kprobe_handler(args->regs))
	572	ret = NOTIFY_STOP;
	573	break;
	574	case DIE_TRAP:
4ba069b8 MG	575	/* kprobe_running() needs smp_processor_id() */
	576	preempt_disable();
	577	if (kprobe_running() &&
	578	kprobe_fault_handler(args->regs, args->trapnr))
	579	ret = NOTIFY_STOP;
	580	preempt_enable();
	581	break;
	582	default:
	583	break;
	584	}
	585	return ret;
	586	}
	587
	588	int __kprobes setjmp_pre_handler(struct kprobe p, struct pt_regs regs)
	589	{
	590	struct jprobe *jp = container_of(p, struct jprobe, kp);
	591	unsigned long addr;
	592	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	593
	594	memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
	595
	596	/* setup return addr to the jprobe handler routine */
	597	regs->psw.addr = (unsigned long)(jp->entry) \| PSW_ADDR_AMODE;
	598
	599	/* r14 is the function return address */
	600	kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
	601	/* r15 is the stack pointer */
	602	kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
	603	addr = (unsigned long)kcb->jprobe_saved_r15;
	604
	605	memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
	606	MIN_STACK_SIZE(addr));
	607	return 1;
	608	}
	609
	610	void __kprobes jprobe_return(void)
	611	{
	612	asm volatile(".word 0x0002");
	613	}
	614
	615	void __kprobes jprobe_return_end(void)
	616	{
	617	asm volatile("bcr 0,0");
	618	}
	619
	620	int __kprobes longjmp_break_handler(struct kprobe p, struct pt_regs regs)
	621	{
	622	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	623	unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
	624
	625	/* Put the regs back */
	626	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
	627	/* put the stack back */
	628	memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
	629	MIN_STACK_SIZE(stack_addr));
	630	preempt_enable_no_resched();
	631	return 1;
	632	}
	633
	634	static struct kprobe trampoline_p = {
	635	.addr = (kprobe_opcode_t *) & kretprobe_trampoline,
	636	.pre_handler = trampoline_probe_handler
	637	};
	638
639	int __init arch_init_kprobes(void)
640	{
641	return register_kprobe(&trampoline_p);
642	}
bf8f6e5b AM	643
	644	int __kprobes arch_trampoline_kprobe(struct kprobe *p)
	645	{
	646	if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
	647	return 1;
	648	return 0;
	649	}