[GitHub/mt8127/android_kernel_alcatel_ttab.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 <asm/cacheflush.h>
#include <asm/kdebug.h>
#include <asm/sections.h>
#include <asm/uaccess.h>
#include <linux/module.h>

DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

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) {
		printk("Attempt to register kprobe at an unaligned address\n");
		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	 */
		return -EINVAL;
	}
	switch (*(__u16 *) instruction) {
	case 0x0101:	/* pr	 */
	case 0xb25a:	/* bsa	 */
	case 0xb240:	/* bakr  */
	case 0xb258:	/* bsg	 */
	case 0xb218:	/* pc	 */
	case 0xb228:	/* pt	 */
		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) >> 4) {
	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 ins_replace_args *args = aref;
	u32 *addr;
	u32 instr;
	int err = -EFAULT;

	/*
	 * Text segment is read-only, hence we use stura to bypass dynamic
	 * address translation to exchange the instruction. Since stura
	 * always operates on four bytes, but we only want to exchange two
	 * bytes do some calculations to get things right. In addition we
	 * shall not cross any page boundaries (vmalloc area!) when writing
	 * the new instruction.
	 */
	addr = (u32 *)ALIGN((unsigned long)args->ptr, 4);
	if ((unsigned long)args->ptr & 2)
		instr = ((*addr) & 0xffff0000) | args->new;
	else
		instr = ((*addr) & 0x0000ffff) | args->new << 16;

	asm volatile(
		"	lra	%1,0(%1)\n"
		"0:	stura	%2,%1\n"
		"1:	la	%0,0\n"
		"2:\n"
		EX_TABLE(0b,2b)
		: "+d" (err)
		: "a" (addr), "d" (instr)
		: "memory", "cc");

	return err;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	unsigned long status = kcb->kprobe_status;
	struct ins_replace_args args;

	args.ptr = p->addr;
	args.old = p->opcode;
	args.new = BREAKPOINT_INSTRUCTION;

	kcb->kprobe_status = KPROBE_SWAP_INST;
	stop_machine_run(swap_instruction, &args, NR_CPUS);
	kcb->kprobe_status = status;
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	unsigned long status = kcb->kprobe_status;
	struct ins_replace_args args;

	args.ptr = p->addr;
	args.old = BREAKPOINT_INSTRUCTION;
	args.new = p->opcode;

	kcb->kprobe_status = KPROBE_SWAP_INST;
	stop_machine_run(swap_instruction, &args, NR_CPUS);
	kcb->kprobe_status = status;
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
{
	mutex_lock(&kprobe_mutex);
	free_insn_slot(p->ainsn.insn, 0);
	mutex_unlock(&kprobe_mutex);
}

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);
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
					struct pt_regs *regs)
{
	struct kretprobe_instance *ri;

	if ((ri = get_free_rp_inst(rp)) != NULL) {
		ri->rp = rp;
		ri->task = current;
		ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];

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

		add_rp_inst(ri);
	} else {
		rp->nmissed++;
	}
}

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) {
		if (*addr != BREAKPOINT_INSTRUCTION) {
			/*
			 * 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;
	}

	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:
	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
 */
void 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);
	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 an multiple functions in the call path
	 * have a return probe installed on them, and/or more then 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;
		}
	}
	BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
	regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;

	reset_current_kprobe();
	spin_unlock_irqrestore(&kretprobe_lock, 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();
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;
}

static 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();
		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:
	case DIE_PAGE_FAULT:
		/* 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);
}
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>
	27	#include <asm/cacheflush.h>
	28	#include <asm/kdebug.h>
	29	#include <asm/sections.h>
	30	#include <asm/uaccess.h>
	31	#include <linux/module.h>
	32
	33	DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
	34	DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
	35
	36	int __kprobes arch_prepare_kprobe(struct kprobe *p)
	37	{
	38	/* Make sure the probe isn't going on a difficult instruction */
	39	if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
	40	return -EINVAL;
	41
	42	if ((unsigned long)p->addr & 0x01) {
	43	printk("Attempt to register kprobe at an unaligned address\n");
	44	return -EINVAL;
	45	}
	46
	47	/* Use the get_insn_slot() facility for correctness */
	48	if (!(p->ainsn.insn = get_insn_slot()))
	49	return -ENOMEM;
	50
	51	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
	52
	53	get_instruction_type(&p->ainsn);
	54	p->opcode = *p->addr;
	55	return 0;
	56	}
	57
	58	int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
	59	{
	60	switch ((__u8 ) instruction) {
	61	case 0x0c: /* bassm */
	62	case 0x0b: /* bsm */
	63	case 0x83: /* diag */
	64	case 0x44: /* ex */
	65	return -EINVAL;
	66	}
	67	switch ((__u16 ) instruction) {
	68	case 0x0101: /* pr */
	69	case 0xb25a: /* bsa */
	70	case 0xb240: /* bakr */
	71	case 0xb258: /* bsg */
	72	case 0xb218: /* pc */
	73	case 0xb228: /* pt */
	74	return -EINVAL;
	75	}
	76	return 0;
	77	}
	78
	79	void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
	80	{
	81	/* default fixup method */
	82	ainsn->fixup = FIXUP_PSW_NORMAL;
	83
	84	/* save r1 operand */
	85	ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
	86
87	/* save the instruction length (pop 5-5) in bytes */
88	switch ((__u8 ) (ainsn->insn) >> 4) {
89	case 0:
90	ainsn->ilen = 2;
91	break;
92	case 1:
93	case 2:
94	ainsn->ilen = 4;
95	break;
96	case 3:
97	ainsn->ilen = 6;
98	break;
99	}
100
101	switch ((__u8 ) ainsn->insn) {
102	case 0x05: /* balr */
103	case 0x0d: /* basr */
104	ainsn->fixup = FIXUP_RETURN_REGISTER;
105	/* if r2 = 0, no branch will be taken */
106	if ((*ainsn->insn & 0x0f) == 0)
107	ainsn->fixup \|= FIXUP_BRANCH_NOT_TAKEN;
108	break;
109	case 0x06: /* bctr */
110	case 0x07: /* bcr */
111	ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
112	break;
113	case 0x45: /* bal */
114	case 0x4d: /* bas */
115	ainsn->fixup = FIXUP_RETURN_REGISTER;
116	break;
117	case 0x47: /* bc */
118	case 0x46: /* bct */
119	case 0x86: /* bxh */
120	case 0x87: /* bxle */
121	ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
122	break;
123	case 0x82: /* lpsw */
124	ainsn->fixup = FIXUP_NOT_REQUIRED;
125	break;
126	case 0xb2: /* lpswe */
127	if ((((__u8 ) ainsn->insn) + 1) == 0xb2) {
128	ainsn->fixup = FIXUP_NOT_REQUIRED;
129	}
130	break;
131	case 0xa7: /* bras */
132	if ((*ainsn->insn & 0x0f) == 0x05) {
133	ainsn->fixup \|= FIXUP_RETURN_REGISTER;
134	}
135	break;
136	case 0xc0:
137	if ((ainsn->insn & 0x0f) == 0x00 / larl */
138	\|\| (ainsn->insn & 0x0f) == 0x05) / brasl */
139	ainsn->fixup \|= FIXUP_RETURN_REGISTER;
140	break;
141	case 0xeb:
142	if ((((__u8 ) ainsn->insn) + 5 ) == 0x44 \|\| /* bxhg */
143	(((__u8 ) ainsn->insn) + 5) == 0x45) {/* bxleg */
144	ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
145	}
146	break;
147	case 0xe3: /* bctg */
148	if ((((__u8 ) ainsn->insn) + 5) == 0x46) {
149	ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
150	}
151	break;
152	}
153	}
154
155	static int __kprobes swap_instruction(void *aref)
156	{
157	struct ins_replace_args *args = aref;
162e006e HC	158	u32 *addr;
162e006e HC	159	u32 instr;
4ba069b8 MG	160	int err = -EFAULT;
4ba069b8 MG	161
162e006e HC	162	/*
	163	* Text segment is read-only, hence we use stura to bypass dynamic
	164	* address translation to exchange the instruction. Since stura
	165	* always operates on four bytes, but we only want to exchange two
	166	* bytes do some calculations to get things right. In addition we
	167	* shall not cross any page boundaries (vmalloc area!) when writing
	168	* the new instruction.
	169	*/
	170	addr = (u32 *)ALIGN((unsigned long)args->ptr, 4);
	171	if ((unsigned long)args->ptr & 2)
	172	instr = ((*addr) & 0xffff0000) \| args->new;
	173	else
	174	instr = ((*addr) & 0x0000ffff) \| args->new << 16;
	175
4ba069b8	176	asm volatile(
162e006e HC	177	" lra %1,0(%1)\n"
	178	"0: stura %2,%1\n"
	179	"1: la %0,0\n"
4ba069b8 MG	180	"2:\n"
4ba069b8 MG	181	EX_TABLE(0b,2b)
162e006e HC	182	: "+d" (err)
	183	: "a" (addr), "d" (instr)
	184	: "memory", "cc");
	185
4ba069b8 MG	186	return err;
	187	}
	188
	189	void __kprobes arch_arm_kprobe(struct kprobe *p)
	190	{
	191	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	192	unsigned long status = kcb->kprobe_status;
	193	struct ins_replace_args args;
	194
	195	args.ptr = p->addr;
	196	args.old = p->opcode;
	197	args.new = BREAKPOINT_INSTRUCTION;
	198
	199	kcb->kprobe_status = KPROBE_SWAP_INST;
	200	stop_machine_run(swap_instruction, &args, NR_CPUS);
	201	kcb->kprobe_status = status;
	202	}
	203
	204	void __kprobes arch_disarm_kprobe(struct kprobe *p)
	205	{
	206	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	207	unsigned long status = kcb->kprobe_status;
	208	struct ins_replace_args args;
	209
	210	args.ptr = p->addr;
	211	args.old = BREAKPOINT_INSTRUCTION;
	212	args.new = p->opcode;
	213
	214	kcb->kprobe_status = KPROBE_SWAP_INST;
	215	stop_machine_run(swap_instruction, &args, NR_CPUS);
	216	kcb->kprobe_status = status;
	217	}
	218
	219	void __kprobes arch_remove_kprobe(struct kprobe *p)
	220	{
	221	mutex_lock(&kprobe_mutex);
b4c6c34a	222	free_insn_slot(p->ainsn.insn, 0);
4ba069b8 MG	223	mutex_unlock(&kprobe_mutex);
	224	}
	225
	226	static void __kprobes prepare_singlestep(struct kprobe p, struct pt_regs regs)
	227	{
	228	per_cr_bits kprobe_per_regs[1];
	229
	230	memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
	231	regs->psw.addr = (unsigned long)p->ainsn.insn \| PSW_ADDR_AMODE;
	232
	233	/* Set up the per control reg info, will pass to lctl */
	234	kprobe_per_regs[0].em_instruction_fetch = 1;
	235	kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
	236	kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
	237
	238	/* Set the PER control regs, turns on single step for this address */
	239	__ctl_load(kprobe_per_regs, 9, 11);
	240	regs->psw.mask \|= PSW_MASK_PER;
	241	regs->psw.mask &= ~(PSW_MASK_IO \| PSW_MASK_EXT \| PSW_MASK_MCHECK);
	242	}
	243
	244	static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
	245	{
	246	kcb->prev_kprobe.kp = kprobe_running();
	247	kcb->prev_kprobe.status = kcb->kprobe_status;
	248	kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
	249	memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
	250	sizeof(kcb->kprobe_saved_ctl));
	251	}
	252
	253	static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
	254	{
	255	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
	256	kcb->kprobe_status = kcb->prev_kprobe.status;
	257	kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
	258	memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
	259	sizeof(kcb->kprobe_saved_ctl));
	260	}
	261
	262	static void __kprobes set_current_kprobe(struct kprobe p, struct pt_regs regs,
	263	struct kprobe_ctlblk *kcb)
	264	{
	265	__get_cpu_var(current_kprobe) = p;
	266	/* Save the interrupt and per flags */
	267	kcb->kprobe_saved_imask = regs->psw.mask &
	268	(PSW_MASK_PER \| PSW_MASK_IO \| PSW_MASK_EXT \| PSW_MASK_MCHECK);
	269	/* Save the control regs that govern PER */
	270	__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
	271	}
	272
	273	/* Called with kretprobe_lock held */
	274	void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
	275	struct pt_regs *regs)
	276	{
	277	struct kretprobe_instance *ri;
	278
	279	if ((ri = get_free_rp_inst(rp)) != NULL) {
	280	ri->rp = rp;
	281	ri->task = current;
	282	ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
	283
	284	/* Replace the return addr with trampoline addr */
	285	regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
	286
287	add_rp_inst(ri);
288	} else {
289	rp->nmissed++;
290	}
291	}
292
293	static int __kprobes kprobe_handler(struct pt_regs *regs)
294	{
295	struct kprobe *p;
296	int ret = 0;
297	unsigned long addr = (unsigned long )
298	((regs->psw.addr & PSW_ADDR_INSN) - 2);
299	struct kprobe_ctlblk *kcb;
300
301	/*
302	* We don't want to be preempted for the entire
303	* duration of kprobe processing
304	*/
305	preempt_disable();
306	kcb = get_kprobe_ctlblk();
307
308	/* Check we're not actually recursing */
309	if (kprobe_running()) {
310	p = get_kprobe(addr);
311	if (p) {
312	if (kcb->kprobe_status == KPROBE_HIT_SS &&
313	*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
314	regs->psw.mask &= ~PSW_MASK_PER;
315	regs->psw.mask \|= kcb->kprobe_saved_imask;
316	goto no_kprobe;
317	}
318	/* We have reentered the kprobe_handler(), since
319	* another probe was hit while within the handler.
320	* We here save the original kprobes variables and
321	* just single step on the instruction of the new probe
322	* without calling any user handlers.
323	*/
324	save_previous_kprobe(kcb);
325	set_current_kprobe(p, regs, kcb);
326	kprobes_inc_nmissed_count(p);
327	prepare_singlestep(p, regs);
328	kcb->kprobe_status = KPROBE_REENTER;
329	return 1;
330	} else {
331	p = __get_cpu_var(current_kprobe);
332	if (p->break_handler && p->break_handler(p, regs)) {
333	goto ss_probe;
334	}
335	}
336	goto no_kprobe;
337	}
338
339	p = get_kprobe(addr);
340	if (!p) {
341	if (*addr != BREAKPOINT_INSTRUCTION) {
342	/*
343	* The breakpoint instruction was removed right
344	* after we hit it. Another cpu has removed
345	* either a probepoint or a debugger breakpoint
346	* at this address. In either case, no further
347	* handling of this interrupt is appropriate.
348	*
349	*/
350	ret = 1;
351	}
352	/* Not one of ours: let kernel handle it */
353	goto no_kprobe;
354	}
355
356	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
357	set_current_kprobe(p, regs, kcb);
358	if (p->pre_handler && p->pre_handler(p, regs))
359	/* handler has already set things up, so skip ss setup */
360	return 1;
361
362	ss_probe:
363	prepare_singlestep(p, regs);
364	kcb->kprobe_status = KPROBE_HIT_SS;
365	return 1;
366
367	no_kprobe:
368	preempt_enable_no_resched();
369	return ret;
370	}
371
372	/*
373	* Function return probe trampoline:
374	* - init_kprobes() establishes a probepoint here
375	* - When the probed function returns, this probe
376	* causes the handlers to fire
377	*/
d42335a3	378	void kretprobe_trampoline_holder(void)
4ba069b8 MG	379	{
	380	asm volatile(".global kretprobe_trampoline\n"
	381	"kretprobe_trampoline: bcr 0,0\n");
	382	}
	383
	384	/*
	385	* Called when the probe at kretprobe trampoline is hit
	386	*/
2b67fc46 HC	387	static int __kprobes trampoline_probe_handler(struct kprobe *p,
2b67fc46 HC	388	struct pt_regs *regs)
4ba069b8 MG	389	{
4ba069b8 MG	390	struct kretprobe_instance *ri = NULL;
99219a3f	391	struct hlist_head *head, empty_rp;
4ba069b8 MG	392	struct hlist_node node, tmp;
	393	unsigned long flags, orig_ret_address = 0;
	394	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
	395
99219a3f	396	INIT_HLIST_HEAD(&empty_rp);
4ba069b8 MG	397	spin_lock_irqsave(&kretprobe_lock, flags);
	398	head = kretprobe_inst_table_head(current);
	399
	400	/*
	401	* It is possible to have multiple instances associated with a given
	402	* task either because an multiple functions in the call path
	403	* have a return probe installed on them, and/or more then one return
	404	* return probe was registered for a target function.
	405	*
	406	* We can handle this because:
	407	* - instances are always inserted at the head of the list
	408	* - when multiple return probes are registered for the same
	409	* function, the first instance's ret_addr will point to the
	410	* real return address, and all the rest will point to
	411	* kretprobe_trampoline
	412	*/
	413	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
	414	if (ri->task != current)
	415	/* another task is sharing our hash bucket */
	416	continue;
	417
	418	if (ri->rp && ri->rp->handler)
	419	ri->rp->handler(ri, regs);
	420
	421	orig_ret_address = (unsigned long)ri->ret_addr;
99219a3f	422	recycle_rp_inst(ri, &empty_rp);
4ba069b8 MG	423
	424	if (orig_ret_address != trampoline_address) {
	425	/*
	426	* This is the real return address. Any other
	427	* instances associated with this task are for
	428	* other calls deeper on the call stack
	429	*/
	430	break;
	431	}
	432	}
	433	BUG_ON(!orig_ret_address \|\| (orig_ret_address == trampoline_address));
	434	regs->psw.addr = orig_ret_address \| PSW_ADDR_AMODE;
	435
	436	reset_current_kprobe();
	437	spin_unlock_irqrestore(&kretprobe_lock, flags);
	438	preempt_enable_no_resched();
	439
99219a3f	440	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
	441	hlist_del(&ri->hlist);
	442	kfree(ri);
	443	}
4ba069b8 MG	444	/*
	445	* By returning a non-zero value, we are telling
	446	* kprobe_handler() that we don't want the post_handler
	447	* to run (and have re-enabled preemption)
	448	*/
	449	return 1;
	450	}
	451
	452	/*
	453	* Called after single-stepping. p->addr is the address of the
	454	* instruction whose first byte has been replaced by the "breakpoint"
	455	* instruction. To avoid the SMP problems that can occur when we
	456	* temporarily put back the original opcode to single-step, we
	457	* single-stepped a copy of the instruction. The address of this
	458	* copy is p->ainsn.insn.
	459	*/
	460	static void __kprobes resume_execution(struct kprobe p, struct pt_regs regs)
	461	{
	462	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	463
	464	regs->psw.addr &= PSW_ADDR_INSN;
	465
	466	if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
	467	regs->psw.addr = (unsigned long)p->addr +
	468	((unsigned long)regs->psw.addr -
	469	(unsigned long)p->ainsn.insn);
	470
	471	if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
	472	if ((unsigned long)regs->psw.addr -
	473	(unsigned long)p->ainsn.insn == p->ainsn.ilen)
	474	regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
	475
	476	if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
	477	regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
	478	(regs->gprs[p->ainsn.reg] -
	479	(unsigned long)p->ainsn.insn))
	480	\| PSW_ADDR_AMODE;
	481
	482	regs->psw.addr \|= PSW_ADDR_AMODE;
	483	/* turn off PER mode */
	484	regs->psw.mask &= ~PSW_MASK_PER;
	485	/* Restore the original per control regs */
	486	__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
	487	regs->psw.mask \|= kcb->kprobe_saved_imask;
	488	}
	489
	490	static int __kprobes post_kprobe_handler(struct pt_regs *regs)
	491	{
	492	struct kprobe *cur = kprobe_running();
	493	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	494
	495	if (!cur)
	496	return 0;
	497
	498	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
	499	kcb->kprobe_status = KPROBE_HIT_SSDONE;
	500	cur->post_handler(cur, regs, 0);
	501	}
	502
	503	resume_execution(cur, regs);
	504
	505	/Restore back the original saved kprobes variables and continue. /
	506	if (kcb->kprobe_status == KPROBE_REENTER) {
	507	restore_previous_kprobe(kcb);
508	goto out;
509	}
510	reset_current_kprobe();
511	out:
512	preempt_enable_no_resched();
513
514	/*
515	* if somebody else is singlestepping across a probe point, psw mask
516	* will have PER set, in which case, continue the remaining processing
517	* of do_single_step, as if this is not a probe hit.
518	*/
519	if (regs->psw.mask & PSW_MASK_PER) {
520	return 0;
521	}
522
523	return 1;
524	}
525
526	static int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
527	{
528	struct kprobe *cur = kprobe_running();
529	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
530	const struct exception_table_entry *entry;
531
532	switch(kcb->kprobe_status) {
533	case KPROBE_SWAP_INST:
534	/* We are here because the instruction replacement failed */
535	return 0;
536	case KPROBE_HIT_SS:
537	case KPROBE_REENTER:
538	/*
539	* We are here because the instruction being single
540	* stepped caused a page fault. We reset the current
541	* kprobe and the nip points back to the probe address
542	* and allow the page fault handler to continue as a
543	* normal page fault.
544	*/
545	regs->psw.addr = (unsigned long)cur->addr \| PSW_ADDR_AMODE;
546	regs->psw.mask &= ~PSW_MASK_PER;
547	regs->psw.mask \|= kcb->kprobe_saved_imask;
548	if (kcb->kprobe_status == KPROBE_REENTER)
549	restore_previous_kprobe(kcb);
550	else
551	reset_current_kprobe();
552	preempt_enable_no_resched();
553	break;
554	case KPROBE_HIT_ACTIVE:
555	case KPROBE_HIT_SSDONE:
556	/*
557	* We increment the nmissed count for accounting,
558	* we can also use npre/npostfault count for accouting
559	* these specific fault cases.
560	*/
561	kprobes_inc_nmissed_count(cur);
562
563	/*
564	* We come here because instructions in the pre/post
565	* handler caused the page_fault, this could happen
566	* if handler tries to access user space by
567	* copy_from_user(), get_user() etc. Let the
568	* user-specified handler try to fix it first.
569	*/
570	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
571	return 1;
572
573	/*
574	* In case the user-specified fault handler returned
575	* zero, try to fix up.
576	*/
577	entry = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
578	if (entry) {
579	regs->psw.addr = entry->fixup \| PSW_ADDR_AMODE;
580	return 1;
581	}
582
583	/*
584	* fixup_exception() could not handle it,
585	* Let do_page_fault() fix it.
586	*/
587	break;
588	default:
589	break;
590	}
591	return 0;
592	}
593
594	/*
595	* Wrapper routine to for handling exceptions.
596	*/
597	int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
598	unsigned long val, void *data)
599	{
600	struct die_args args = (struct die_args )data;
601	int ret = NOTIFY_DONE;
602
603	switch (val) {
604	case DIE_BPT:
605	if (kprobe_handler(args->regs))
606	ret = NOTIFY_STOP;
607	break;
608	case DIE_SSTEP:
609	if (post_kprobe_handler(args->regs))
610	ret = NOTIFY_STOP;
611	break;
612	case DIE_TRAP:
613	case DIE_PAGE_FAULT:
614	/* kprobe_running() needs smp_processor_id() */
615	preempt_disable();
616	if (kprobe_running() &&
617	kprobe_fault_handler(args->regs, args->trapnr))
618	ret = NOTIFY_STOP;
619	preempt_enable();
620	break;
621	default:
622	break;
623	}
624	return ret;
625	}
626
627	int __kprobes setjmp_pre_handler(struct kprobe p, struct pt_regs regs)
628	{
629	struct jprobe *jp = container_of(p, struct jprobe, kp);
630	unsigned long addr;
631	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
632
633	memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
634
635	/* setup return addr to the jprobe handler routine */
636	regs->psw.addr = (unsigned long)(jp->entry) \| PSW_ADDR_AMODE;
637
638	/* r14 is the function return address */
639	kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
640	/* r15 is the stack pointer */
641	kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
642	addr = (unsigned long)kcb->jprobe_saved_r15;
643
644	memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
645	MIN_STACK_SIZE(addr));
646	return 1;
647	}
648
649	void __kprobes jprobe_return(void)
650	{
651	asm volatile(".word 0x0002");
652	}
653
654	void __kprobes jprobe_return_end(void)
655	{
656	asm volatile("bcr 0,0");
657	}
658
659	int __kprobes longjmp_break_handler(struct kprobe p, struct pt_regs regs)
660	{
661	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
662	unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
663
664	/* Put the regs back */
665	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
666	/* put the stack back */
667	memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
668	MIN_STACK_SIZE(stack_addr));
669	preempt_enable_no_resched();
670	return 1;
671	}
672
673	static struct kprobe trampoline_p = {
674	.addr = (kprobe_opcode_t *) & kretprobe_trampoline,
675	.pre_handler = trampoline_probe_handler
676	};
677
678	int __init arch_init_kprobes(void)
679	{
680	return register_kprobe(&trampoline_p);
681	}