text: /*
   *  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 IBM Corp. 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 = extable_fixup(entry) | 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");
  }
  
  static void __used __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;
  }
  