arch/s390/kernel/kprobes.c - third_party/linux - Git at Google

 /*
  *  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 <asm/cacheflush.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);

 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) {
 		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) >> 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 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 *)((unsigned long)args->ptr & -4UL);
 	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_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_run 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:
 	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);
 	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;
 		}
 	}
 	kretprobe_assert(ri, 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;
 }

 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:
 		/* 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;
 }
	/*
	* 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 <asm/cacheflush.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);

	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) {
	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) >> 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 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 *)((unsigned long)args->ptr & -4UL);
	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_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_run 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:
	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);
	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;
	}
	}
	kretprobe_assert(ri, 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;
	}

	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:
	/* 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;
	}