arch/s390/kernel/kprobes.c - kernel/msm-4.9 - Gitiles

 /*
  *  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>
 #include <linux/hardirq.h>

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

 struct kretprobe_blackpoint kretprobe_blacklist[] = { };

 static int __kprobes is_prohibited_opcode(kprobe_opcode_t *insn)
 {
 	switch (insn[0] >> 8) {
 	case 0x0c:	/* bassm */
 	case 0x0b:	/* bsm	 */
 	case 0x83:	/* diag  */
 	case 0x44:	/* ex	 */
 	case 0xac:	/* stnsm */
 	case 0xad:	/* stosm */
 		return -EINVAL;
 	}
 	switch (insn[0]) {
 	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;
 }

 static int __kprobes get_fixup_type(kprobe_opcode_t *insn)
 {
 	/* default fixup method */
 	int fixup = FIXUP_PSW_NORMAL;

 	switch (insn[0] >> 8) {
 	case 0x05:	/* balr	*/
 	case 0x0d:	/* basr */
 		fixup = FIXUP_RETURN_REGISTER;
 		/* if r2 = 0, no branch will be taken */
 		if ((insn[0] & 0x0f) == 0)
 			fixup |= FIXUP_BRANCH_NOT_TAKEN;
 		break;
 	case 0x06:	/* bctr	*/
 	case 0x07:	/* bcr	*/
 		fixup = FIXUP_BRANCH_NOT_TAKEN;
 		break;
 	case 0x45:	/* bal	*/
 	case 0x4d:	/* bas	*/
 		fixup = FIXUP_RETURN_REGISTER;
 		break;
 	case 0x47:	/* bc	*/
 	case 0x46:	/* bct	*/
 	case 0x86:	/* bxh	*/
 	case 0x87:	/* bxle	*/
 		fixup = FIXUP_BRANCH_NOT_TAKEN;
 		break;
 	case 0x82:	/* lpsw	*/
 		fixup = FIXUP_NOT_REQUIRED;
 		break;
 	case 0xb2:	/* lpswe */
 		if ((insn[0] & 0xff) == 0xb2)
 			fixup = FIXUP_NOT_REQUIRED;
 		break;
 	case 0xa7:	/* bras	*/
 		if ((insn[0] & 0x0f) == 0x05)
 			fixup |= FIXUP_RETURN_REGISTER;
 		break;
 	case 0xc0:
 		if ((insn[0] & 0x0f) == 0x00 ||	/* larl  */
 		    (insn[0] & 0x0f) == 0x05)	/* brasl */
 		fixup |= FIXUP_RETURN_REGISTER;
 		break;
 	case 0xeb:
 		if ((insn[2] & 0xff) == 0x44 ||	/* bxhg  */
 		    (insn[2] & 0xff) == 0x45)	/* bxleg */
 			fixup = FIXUP_BRANCH_NOT_TAKEN;
 		break;
 	case 0xe3:	/* bctg	*/
 		if ((insn[2] & 0xff) == 0x46)
 			fixup = FIXUP_BRANCH_NOT_TAKEN;
 		break;
 	}
 	return fixup;
 }

 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
 	if ((unsigned long) p->addr & 0x01)
 		return -EINVAL;

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

 	p->opcode = *p->addr;
 	memcpy(p->ainsn.insn, p->addr, ((p->opcode >> 14) + 3) & -2);

 	return 0;
 }

 struct ins_replace_args {
 	kprobe_opcode_t *ptr;
 	kprobe_opcode_t opcode;
 };

 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;

 	kcb->kprobe_status = KPROBE_SWAP_INST;
 	probe_kernel_write(args->ptr, &args->opcode, sizeof(args->opcode));
 	kcb->kprobe_status = status;
 	return 0;
 }

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

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

 void __kprobes arch_remove_kprobe(struct kprobe *p)
 {
 }

 static void __kprobes enable_singlestep(struct kprobe_ctlblk *kcb,
 					struct pt_regs *regs,
 					unsigned long ip)
 {
 	struct per_regs per_kprobe;

 	/* Set up the PER control registers %cr9-%cr11 */
 	per_kprobe.control = PER_EVENT_IFETCH;
 	per_kprobe.start = ip;
 	per_kprobe.end = ip;

 	/* Save control regs and psw mask */
 	__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 	kcb->kprobe_saved_imask = regs->psw.mask &
 		(PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);

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

 static void __kprobes disable_singlestep(struct kprobe_ctlblk *kcb,
 					 struct pt_regs *regs,
 					 unsigned long ip)
 {
 	/* Restore control regs and psw mask, set new psw address */
 	__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 	regs->psw.mask &= ~PSW_MASK_PER;
 	regs->psw.mask |= kcb->kprobe_saved_imask;
 	regs->psw.addr = ip | PSW_ADDR_AMODE;
 }

 /*
  * Activate a kprobe by storing its pointer to current_kprobe. The
  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
  * two kprobes can be active, see KPROBE_REENTER.
  */
 static void __kprobes push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 {
 	kcb->prev_kprobe.kp = __get_cpu_var(current_kprobe);
 	kcb->prev_kprobe.status = kcb->kprobe_status;
 	__get_cpu_var(current_kprobe) = p;
 }

 /*
  * Deactivate a kprobe by backing up to the previous state. If the
  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
  * for any other state prev_kprobe.kp will be NULL.
  */
 static void __kprobes pop_kprobe(struct kprobe_ctlblk *kcb)
 {
 	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
 	kcb->kprobe_status = kcb->prev_kprobe.status;
 }

 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 void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb,
 					   struct kprobe *p)
 {
 	switch (kcb->kprobe_status) {
 	case KPROBE_HIT_SSDONE:
 	case KPROBE_HIT_ACTIVE:
 		kprobes_inc_nmissed_count(p);
 		break;
 	case KPROBE_HIT_SS:
 	case KPROBE_REENTER:
 	default:
 		/*
 		 * A kprobe on the code path to single step an instruction
 		 * is a BUG. The code path resides in the .kprobes.text
 		 * section and is executed with interrupts disabled.
 		 */
 		printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
 		dump_kprobe(p);
 		BUG();
 	}
 }

 static int __kprobes kprobe_handler(struct pt_regs *regs)
 {
 	struct kprobe_ctlblk *kcb;
 	struct kprobe *p;

 	/*
 	 * We want to disable preemption for the entire duration of kprobe
 	 * processing. That includes the calls to the pre/post handlers
 	 * and single stepping the kprobe instruction.
 	 */
 	preempt_disable();
 	kcb = get_kprobe_ctlblk();
 	p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2));

 	if (p) {
 		if (kprobe_running()) {
 			/*
 			 * We have hit a kprobe while another is still
 			 * active. This can happen in the pre and post
 			 * handler. Single step the instruction of the
 			 * new probe but do not call any handler function
 			 * of this secondary kprobe.
 			 * push_kprobe and pop_kprobe saves and restores
 			 * the currently active kprobe.
 			 */
 			kprobe_reenter_check(kcb, p);
 			push_kprobe(kcb, p);
 			kcb->kprobe_status = KPROBE_REENTER;
 		} else {
 			/*
 			 * If we have no pre-handler or it returned 0, we
 			 * continue with single stepping. If we have a
 			 * pre-handler and it returned non-zero, it prepped
 			 * for calling the break_handler below on re-entry
 			 * for jprobe processing, so get out doing nothing
 			 * more here.
 			 */
 			push_kprobe(kcb, p);
 			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 			if (p->pre_handler && p->pre_handler(p, regs))
 				return 1;
 			kcb->kprobe_status = KPROBE_HIT_SS;
 		}
 		enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
 		return 1;
 	} else if (kprobe_running()) {
 		p = __get_cpu_var(current_kprobe);
 		if (p->break_handler && p->break_handler(p, regs)) {
 			/*
 			 * Continuation after the jprobe completed and
 			 * caused the jprobe_return trap. The jprobe
 			 * break_handler "returns" to the original
 			 * function that still has the kprobe breakpoint
 			 * installed. We continue with single stepping.
 			 */
 			kcb->kprobe_status = KPROBE_HIT_SS;
 			enable_singlestep(kcb, regs,
 					  (unsigned long) p->ainsn.insn);
 			return 1;
 		} /* else:
 		   * No kprobe at this address and the current kprobe
 		   * has no break handler (no jprobe!). The kernel just
 		   * exploded, let the standard trap handler pick up the
 		   * pieces.
 		   */
 	} /* else:
 	   * No kprobe at this address and no active kprobe. The trap has
 	   * not been caused by a kprobe breakpoint. The race of breakpoint
 	   * vs. kprobe remove does not exist because on s390 as we use
 	   * stop_machine to arm/disarm the breakpoints.
 	   */
 	preempt_enable_no_resched();
 	return 0;
 }

 /*
  * 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;
 	struct hlist_head *head, empty_rp;
 	struct hlist_node *node, *tmp;
 	unsigned long flags, orig_ret_address;
 	unsigned long trampoline_address;
 	kprobe_opcode_t *correct_ret_addr;

 	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
 	 */
 	ri = NULL;
 	orig_ret_address = 0;
 	correct_ret_addr = NULL;
 	trampoline_address = (unsigned long) &kretprobe_trampoline;
 	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 		if (ri->task != current)
 			/* another task is sharing our hash bucket */
 			continue;

 		orig_ret_address = (unsigned long) ri->ret_addr;

 		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);

 	correct_ret_addr = ri->ret_addr;
 	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 		if (ri->task != current)
 			/* another task is sharing our hash bucket */
 			continue;

 		orig_ret_address = (unsigned long) ri->ret_addr;

 		if (ri->rp && ri->rp->handler) {
 			ri->ret_addr = correct_ret_addr;
 			ri->rp->handler(ri, regs);
 		}

 		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;
 	}

 	regs->psw.addr = orig_ret_address | PSW_ADDR_AMODE;

 	pop_kprobe(get_kprobe_ctlblk());
 	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();
 	unsigned long ip = regs->psw.addr & PSW_ADDR_INSN;
 	int fixup = get_fixup_type(p->ainsn.insn);

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

 	if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
 		int ilen = ((p->ainsn.insn[0] >> 14) + 3) & -2;
 		if (ip - (unsigned long) p->ainsn.insn == ilen)
 			ip = (unsigned long) p->addr + ilen;
 	}

 	if (fixup & FIXUP_RETURN_REGISTER) {
 		int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
 		regs->gprs[reg] += (unsigned long) p->addr -
 				   (unsigned long) p->ainsn.insn;
 	}

 	disable_singlestep(kcb, regs, ip);
 }

 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 {
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 	struct kprobe *p = kprobe_running();

 	if (!p)
 		return 0;

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

 	resume_execution(p, regs);
 	pop_kprobe(kcb);
 	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_trap_handler(struct pt_regs *regs, int trapnr)
 {
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 	struct kprobe *p = kprobe_running();
 	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.
 		 */
 		disable_singlestep(kcb, regs, (unsigned long) p->addr);
 		pop_kprobe(kcb);
 		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(p);

 		/*
 		 * 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 (p->fault_handler && p->fault_handler(p, 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;
 }

 int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 {
 	int ret;

 	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 		local_irq_disable();
 	ret = kprobe_trap_handler(regs, trapnr);
 	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 		local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 	return ret;
 }

 /*
  * 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;
 	struct pt_regs *regs = args->regs;
 	int ret = NOTIFY_DONE;

 	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 		local_irq_disable();

 	switch (val) {
 	case DIE_BPT:
 		if (kprobe_handler(regs))
 			ret = NOTIFY_STOP;
 		break;
 	case DIE_SSTEP:
 		if (post_kprobe_handler(regs))
 			ret = NOTIFY_STOP;
 		break;
 	case DIE_TRAP:
 		if (!preemptible() && kprobe_running() &&
 		    kprobe_trap_handler(regs, args->trapnr))
 			ret = NOTIFY_STOP;
 		break;
 	default:
 		break;
 	}

 	if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 		local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);

 	return ret;
 }

 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 {
 	struct jprobe *jp = container_of(p, struct jprobe, kp);
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 	unsigned long stack;

 	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;
 	regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);

 	/* r15 is the stack pointer */
 	stack = (unsigned long) regs->gprs[15];

 	memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
 	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;

 	stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];

 	/* Put the regs back */
 	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
 	/* put the stack back */
 	memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
 	preempt_enable_no_resched();
 	return 1;
 }

 static struct kprobe trampoline = {
 	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 	.pre_handler = trampoline_probe_handler
 };

 int __init arch_init_kprobes(void)
 {
 	return register_kprobe(&trampoline);
 }

 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 {
 	return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 }
	/*
	* 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>
	#include <linux/hardirq.h>

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

	struct kretprobe_blackpoint kretprobe_blacklist[] = { };

	static int __kprobes is_prohibited_opcode(kprobe_opcode_t *insn)
	{
	switch (insn[0] >> 8) {
	case 0x0c: /* bassm */
	case 0x0b: /* bsm */
	case 0x83: /* diag */
	case 0x44: /* ex */
	case 0xac: /* stnsm */
	case 0xad: /* stosm */
	return -EINVAL;
	}
	switch (insn[0]) {
	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;
	}

	static int __kprobes get_fixup_type(kprobe_opcode_t *insn)
	{
	/* default fixup method */
	int fixup = FIXUP_PSW_NORMAL;

	switch (insn[0] >> 8) {
	case 0x05: /* balr */
	case 0x0d: /* basr */
	fixup = FIXUP_RETURN_REGISTER;
	/* if r2 = 0, no branch will be taken */
	if ((insn[0] & 0x0f) == 0)
	fixup \|= FIXUP_BRANCH_NOT_TAKEN;
	break;
	case 0x06: /* bctr */
	case 0x07: /* bcr */
	fixup = FIXUP_BRANCH_NOT_TAKEN;
	break;
	case 0x45: /* bal */
	case 0x4d: /* bas */
	fixup = FIXUP_RETURN_REGISTER;
	break;
	case 0x47: /* bc */
	case 0x46: /* bct */
	case 0x86: /* bxh */
	case 0x87: /* bxle */
	fixup = FIXUP_BRANCH_NOT_TAKEN;
	break;
	case 0x82: /* lpsw */
	fixup = FIXUP_NOT_REQUIRED;
	break;
	case 0xb2: /* lpswe */
	if ((insn[0] & 0xff) == 0xb2)
	fixup = FIXUP_NOT_REQUIRED;
	break;
	case 0xa7: /* bras */
	if ((insn[0] & 0x0f) == 0x05)
	fixup \|= FIXUP_RETURN_REGISTER;
	break;
	case 0xc0:
	if ((insn[0] & 0x0f) == 0x00 \|\| /* larl */
	(insn[0] & 0x0f) == 0x05) /* brasl */
	fixup \|= FIXUP_RETURN_REGISTER;
	break;
	case 0xeb:
	if ((insn[2] & 0xff) == 0x44 \|\| /* bxhg */
	(insn[2] & 0xff) == 0x45) /* bxleg */
	fixup = FIXUP_BRANCH_NOT_TAKEN;
	break;
	case 0xe3: /* bctg */
	if ((insn[2] & 0xff) == 0x46)
	fixup = FIXUP_BRANCH_NOT_TAKEN;
	break;
	}
	return fixup;
	}

	int __kprobes arch_prepare_kprobe(struct kprobe *p)
	{
	if ((unsigned long) p->addr & 0x01)
	return -EINVAL;

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

	p->opcode = *p->addr;
	memcpy(p->ainsn.insn, p->addr, ((p->opcode >> 14) + 3) & -2);

	return 0;
	}

	struct ins_replace_args {
	kprobe_opcode_t *ptr;
	kprobe_opcode_t opcode;
	};

	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;

	kcb->kprobe_status = KPROBE_SWAP_INST;
	probe_kernel_write(args->ptr, &args->opcode, sizeof(args->opcode));
	kcb->kprobe_status = status;
	return 0;
	}

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

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

	void __kprobes arch_remove_kprobe(struct kprobe *p)
	{
	}

	static void __kprobes enable_singlestep(struct kprobe_ctlblk *kcb,
	struct pt_regs *regs,
	unsigned long ip)
	{
	struct per_regs per_kprobe;

	/* Set up the PER control registers %cr9-%cr11 */
	per_kprobe.control = PER_EVENT_IFETCH;
	per_kprobe.start = ip;
	per_kprobe.end = ip;

	/* Save control regs and psw mask */
	__ctl_store(kcb->kprobe_saved_ctl, 9, 11);
	kcb->kprobe_saved_imask = regs->psw.mask &
	(PSW_MASK_PER \| PSW_MASK_IO \| PSW_MASK_EXT);

	/* Set PER control regs, turns on single step for the given address */
	__ctl_load(per_kprobe, 9, 11);
	regs->psw.mask \|= PSW_MASK_PER;
	regs->psw.mask &= ~(PSW_MASK_IO \| PSW_MASK_EXT);
	regs->psw.addr = ip \| PSW_ADDR_AMODE;
	}

	static void __kprobes disable_singlestep(struct kprobe_ctlblk *kcb,
	struct pt_regs *regs,
	unsigned long ip)
	{
	/* Restore control regs and psw mask, set new psw address */
	__ctl_load(kcb->kprobe_saved_ctl, 9, 11);
	regs->psw.mask &= ~PSW_MASK_PER;
	regs->psw.mask \|= kcb->kprobe_saved_imask;
	regs->psw.addr = ip \| PSW_ADDR_AMODE;
	}

	/*
	* Activate a kprobe by storing its pointer to current_kprobe. The
	* previous kprobe is stored in kcb->prev_kprobe. A stack of up to
	* two kprobes can be active, see KPROBE_REENTER.
	*/
	static void __kprobes push_kprobe(struct kprobe_ctlblk kcb, struct kprobe p)
	{
	kcb->prev_kprobe.kp = __get_cpu_var(current_kprobe);
	kcb->prev_kprobe.status = kcb->kprobe_status;
	__get_cpu_var(current_kprobe) = p;
	}

	/*
	* Deactivate a kprobe by backing up to the previous state. If the
	* current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
	* for any other state prev_kprobe.kp will be NULL.
	*/
	static void __kprobes pop_kprobe(struct kprobe_ctlblk *kcb)
	{
	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
	kcb->kprobe_status = kcb->prev_kprobe.status;
	}

	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 void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb,
	struct kprobe *p)
	{
	switch (kcb->kprobe_status) {
	case KPROBE_HIT_SSDONE:
	case KPROBE_HIT_ACTIVE:
	kprobes_inc_nmissed_count(p);
	break;
	case KPROBE_HIT_SS:
	case KPROBE_REENTER:
	default:
	/*
	* A kprobe on the code path to single step an instruction
	* is a BUG. The code path resides in the .kprobes.text
	* section and is executed with interrupts disabled.
	*/
	printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
	dump_kprobe(p);
	BUG();
	}
	}

	static int __kprobes kprobe_handler(struct pt_regs *regs)
	{
	struct kprobe_ctlblk *kcb;
	struct kprobe *p;

	/*
	* We want to disable preemption for the entire duration of kprobe
	* processing. That includes the calls to the pre/post handlers
	* and single stepping the kprobe instruction.
	*/
	preempt_disable();
	kcb = get_kprobe_ctlblk();
	p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2));

	if (p) {
	if (kprobe_running()) {
	/*
	* We have hit a kprobe while another is still
	* active. This can happen in the pre and post
	* handler. Single step the instruction of the
	* new probe but do not call any handler function
	* of this secondary kprobe.
	* push_kprobe and pop_kprobe saves and restores
	* the currently active kprobe.
	*/
	kprobe_reenter_check(kcb, p);
	push_kprobe(kcb, p);
	kcb->kprobe_status = KPROBE_REENTER;
	} else {
	/*
	* If we have no pre-handler or it returned 0, we
	* continue with single stepping. If we have a
	* pre-handler and it returned non-zero, it prepped
	* for calling the break_handler below on re-entry
	* for jprobe processing, so get out doing nothing
	* more here.
	*/
	push_kprobe(kcb, p);
	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
	if (p->pre_handler && p->pre_handler(p, regs))
	return 1;
	kcb->kprobe_status = KPROBE_HIT_SS;
	}
	enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
	return 1;
	} else if (kprobe_running()) {
	p = __get_cpu_var(current_kprobe);
	if (p->break_handler && p->break_handler(p, regs)) {
	/*
	* Continuation after the jprobe completed and
	* caused the jprobe_return trap. The jprobe
	* break_handler "returns" to the original
	* function that still has the kprobe breakpoint
	* installed. We continue with single stepping.
	*/
	kcb->kprobe_status = KPROBE_HIT_SS;
	enable_singlestep(kcb, regs,
	(unsigned long) p->ainsn.insn);
	return 1;
	} /* else:
	* No kprobe at this address and the current kprobe
	* has no break handler (no jprobe!). The kernel just
	* exploded, let the standard trap handler pick up the
	* pieces.
	*/
	} /* else:
	* No kprobe at this address and no active kprobe. The trap has
	* not been caused by a kprobe breakpoint. The race of breakpoint
	* vs. kprobe remove does not exist because on s390 as we use
	* stop_machine to arm/disarm the breakpoints.
	*/
	preempt_enable_no_resched();
	return 0;
	}

	/*
	* 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;
	struct hlist_head *head, empty_rp;
	struct hlist_node node, tmp;
	unsigned long flags, orig_ret_address;
	unsigned long trampoline_address;
	kprobe_opcode_t *correct_ret_addr;

	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
	*/
	ri = NULL;
	orig_ret_address = 0;
	correct_ret_addr = NULL;
	trampoline_address = (unsigned long) &kretprobe_trampoline;
	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
	if (ri->task != current)
	/* another task is sharing our hash bucket */
	continue;

	orig_ret_address = (unsigned long) ri->ret_addr;

	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);

	correct_ret_addr = ri->ret_addr;
	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
	if (ri->task != current)
	/* another task is sharing our hash bucket */
	continue;

	orig_ret_address = (unsigned long) ri->ret_addr;

	if (ri->rp && ri->rp->handler) {
	ri->ret_addr = correct_ret_addr;
	ri->rp->handler(ri, regs);
	}

	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;
	}

	regs->psw.addr = orig_ret_address \| PSW_ADDR_AMODE;

	pop_kprobe(get_kprobe_ctlblk());
	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();
	unsigned long ip = regs->psw.addr & PSW_ADDR_INSN;
	int fixup = get_fixup_type(p->ainsn.insn);

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

	if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
	int ilen = ((p->ainsn.insn[0] >> 14) + 3) & -2;
	if (ip - (unsigned long) p->ainsn.insn == ilen)
	ip = (unsigned long) p->addr + ilen;
	}

	if (fixup & FIXUP_RETURN_REGISTER) {
	int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
	regs->gprs[reg] += (unsigned long) p->addr -
	(unsigned long) p->ainsn.insn;
	}

	disable_singlestep(kcb, regs, ip);
	}

	static int __kprobes post_kprobe_handler(struct pt_regs *regs)
	{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	struct kprobe *p = kprobe_running();

	if (!p)
	return 0;

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

	resume_execution(p, regs);
	pop_kprobe(kcb);
	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_trap_handler(struct pt_regs *regs, int trapnr)
	{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	struct kprobe *p = kprobe_running();
	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.
	*/
	disable_singlestep(kcb, regs, (unsigned long) p->addr);
	pop_kprobe(kcb);
	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(p);

	/*
	* 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 (p->fault_handler && p->fault_handler(p, 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;
	}

	int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
	{
	int ret;

	if (regs->psw.mask & (PSW_MASK_IO \| PSW_MASK_EXT))
	local_irq_disable();
	ret = kprobe_trap_handler(regs, trapnr);
	if (regs->psw.mask & (PSW_MASK_IO \| PSW_MASK_EXT))
	local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
	return ret;
	}

	/*
	* 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;
	struct pt_regs *regs = args->regs;
	int ret = NOTIFY_DONE;

	if (regs->psw.mask & (PSW_MASK_IO \| PSW_MASK_EXT))
	local_irq_disable();

	switch (val) {
	case DIE_BPT:
	if (kprobe_handler(regs))
	ret = NOTIFY_STOP;
	break;
	case DIE_SSTEP:
	if (post_kprobe_handler(regs))
	ret = NOTIFY_STOP;
	break;
	case DIE_TRAP:
	if (!preemptible() && kprobe_running() &&
	kprobe_trap_handler(regs, args->trapnr))
	ret = NOTIFY_STOP;
	break;
	default:
	break;
	}

	if (regs->psw.mask & (PSW_MASK_IO \| PSW_MASK_EXT))
	local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);

	return ret;
	}

	int __kprobes setjmp_pre_handler(struct kprobe p, struct pt_regs regs)
	{
	struct jprobe *jp = container_of(p, struct jprobe, kp);
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	unsigned long stack;

	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;
	regs->psw.mask &= ~(PSW_MASK_IO \| PSW_MASK_EXT);

	/* r15 is the stack pointer */
	stack = (unsigned long) regs->gprs[15];

	memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
	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;

	stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];

	/* Put the regs back */
	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
	/* put the stack back */
	memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
	preempt_enable_no_resched();
	return 1;
	}

	static struct kprobe trampoline = {
	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
	.pre_handler = trampoline_probe_handler
	};

	int __init arch_init_kprobes(void)
	{
	return register_kprobe(&trampoline);
	}

	int __kprobes arch_trampoline_kprobe(struct kprobe *p)
	{
	return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
	}