arch/sparc/kernel/uprobes.c - linux - Git at Google

 /*
  * User-space Probes (UProbes) for sparc
  *
  * Copyright (C) 2013 Oracle Inc.
  *
  * 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, see <http://www.gnu.org/licenses/>.
  *
  * Authors:
  *	Jose E. Marchesi <jose.marchesi@oracle.com>
  *	Eric Saint Etienne <eric.saint.etienne@oracle.com>
  */

 #include <linux/kernel.h>
 #include <linux/highmem.h>
 #include <linux/uprobes.h>
 #include <linux/uaccess.h>
 #include <linux/sched.h> /* For struct task_struct */
 #include <linux/kdebug.h>

 #include <asm/cacheflush.h>

 /* Compute the address of the breakpoint instruction and return it.
  *
  * Note that uprobe_get_swbp_addr is defined as a weak symbol in
  * kernel/events/uprobe.c.
  */
 unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
 {
 	return instruction_pointer(regs);
 }

 static void copy_to_page(struct page *page, unsigned long vaddr,
 			 const void *src, int len)
 {
 	void *kaddr = kmap_atomic(page);

 	memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
 	kunmap_atomic(kaddr);
 }

 /* Fill in the xol area with the probed instruction followed by the
  * single-step trap.  Some fixups in the copied instruction are
  * performed at this point.
  *
  * Note that uprobe_xol_copy is defined as a weak symbol in
  * kernel/events/uprobe.c.
  */
 void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
 			   void *src, unsigned long len)
 {
 	const u32 stp_insn = UPROBE_STP_INSN;
 	u32 insn = *(u32 *) src;

 	/* Branches annulling their delay slot must be fixed to not do
 	 * so.  Clearing the annul bit on these instructions we can be
 	 * sure the single-step breakpoint in the XOL slot will be
 	 * executed.
 	 */

 	u32 op = (insn >> 30) & 0x3;
 	u32 op2 = (insn >> 22) & 0x7;

 	if (op == 0 &&
 	    (op2 == 1 || op2 == 2 || op2 == 3 || op2 == 5 || op2 == 6) &&
 	    (insn & ANNUL_BIT) == ANNUL_BIT)
 		insn &= ~ANNUL_BIT;

 	copy_to_page(page, vaddr, &insn, len);
 	copy_to_page(page, vaddr+len, &stp_insn, 4);
 }


 /* Instruction analysis/validity.
  *
  * This function returns 0 on success or a -ve number on error.
  */
 int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
 			     struct mm_struct *mm, unsigned long addr)
 {
 	/* Any unsupported instruction?  Then return -EINVAL  */
 	return 0;
 }

 /* If INSN is a relative control transfer instruction, return the
  * corrected branch destination value.
  *
  * Note that regs->tpc and regs->tnpc still hold the values of the
  * program counters at the time of the single-step trap due to the
  * execution of the UPROBE_STP_INSN at utask->xol_vaddr + 4.
  *
  */
 static unsigned long relbranch_fixup(u32 insn, struct uprobe_task *utask,
 				     struct pt_regs *regs)
 {
 	/* Branch not taken, no mods necessary.  */
 	if (regs->tnpc == regs->tpc + 0x4UL)
 		return utask->autask.saved_tnpc + 0x4UL;

 	/* The three cases are call, branch w/prediction,
 	 * and traditional branch.
 	 */
 	if ((insn & 0xc0000000) == 0x40000000 ||
 	    (insn & 0xc1c00000) == 0x00400000 ||
 	    (insn & 0xc1c00000) == 0x00800000) {
 		unsigned long real_pc = (unsigned long) utask->vaddr;
 		unsigned long ixol_addr = utask->xol_vaddr;

 		/* The instruction did all the work for us
 		 * already, just apply the offset to the correct
 		 * instruction location.
 		 */
 		return (real_pc + (regs->tnpc - ixol_addr));
 	}

 	/* It is jmpl or some other absolute PC modification instruction,
 	 * leave NPC as-is.
 	 */
 	return regs->tnpc;
 }

 /* If INSN is an instruction which writes its PC location
  * into a destination register, fix that up.
  */
 static int retpc_fixup(struct pt_regs *regs, u32 insn,
 		       unsigned long real_pc)
 {
 	unsigned long *slot = NULL;
 	int rc = 0;

 	/* Simplest case is 'call', which always uses %o7 */
 	if ((insn & 0xc0000000) == 0x40000000)
 		slot = &regs->u_regs[UREG_I7];

 	/* 'jmpl' encodes the register inside of the opcode */
 	if ((insn & 0xc1f80000) == 0x81c00000) {
 		unsigned long rd = ((insn >> 25) & 0x1f);

 		if (rd <= 15) {
 			slot = &regs->u_regs[rd];
 		} else {
 			unsigned long fp = regs->u_regs[UREG_FP];
 			/* Hard case, it goes onto the stack. */
 			flushw_all();

 			rd -= 16;
 			if (test_thread_64bit_stack(fp)) {
 				unsigned long __user *uslot =
 			(unsigned long __user *) (fp + STACK_BIAS) + rd;
 				rc = __put_user(real_pc, uslot);
 			} else {
 				unsigned int __user *uslot = (unsigned int
 						__user *) fp + rd;
 				rc = __put_user((u32) real_pc, uslot);
 			}
 		}
 	}
 	if (slot != NULL)
 		*slot = real_pc;
 	return rc;
 }

 /* Single-stepping can be avoided for certain instructions: NOPs and
  * instructions that can be emulated.  This function determines
  * whether the instruction where the uprobe is installed falls in one
  * of these cases and emulates it.
  *
  * This function returns true if the single-stepping can be skipped,
  * false otherwise.
  */
 bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 {
 	/* We currently only emulate NOP instructions.
 	 */

 	if (auprobe->ixol == (1 << 24)) {
 		regs->tnpc += 4;
 		regs->tpc += 4;
 		return true;
 	}

 	return false;
 }

 /* Prepare to execute out of line.  At this point
  * current->utask->xol_vaddr points to an allocated XOL slot properly
  * initialized with the original instruction and the single-stepping
  * trap instruction.
  *
  * This function returns 0 on success, any other number on error.
  */
 int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 {
 	struct uprobe_task *utask = current->utask;
 	struct arch_uprobe_task *autask = &current->utask->autask;

 	/* Save the current program counters so they can be restored
 	 * later.
 	 */
 	autask->saved_tpc = regs->tpc;
 	autask->saved_tnpc = regs->tnpc;

 	/* Adjust PC and NPC so the first instruction in the XOL slot
 	 * will be executed by the user task.
 	 */
 	instruction_pointer_set(regs, utask->xol_vaddr);

 	return 0;
 }

 /* Prepare to resume execution after the single-step.  Called after
  * single-stepping. 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.
  *
  * This function returns 0 on success, any other number on error.
  */
 int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 {
 	struct uprobe_task *utask = current->utask;
 	struct arch_uprobe_task *autask = &utask->autask;
 	u32 insn = auprobe->ixol;
 	int rc = 0;

 	if (utask->state == UTASK_SSTEP_ACK) {
 		regs->tnpc = relbranch_fixup(insn, utask, regs);
 		regs->tpc = autask->saved_tnpc;
 		rc =  retpc_fixup(regs, insn, (unsigned long) utask->vaddr);
 	} else {
 		regs->tnpc = utask->vaddr+4;
 		regs->tpc = autask->saved_tnpc+4;
 	}
 	return rc;
 }

 /* Handler for uprobe traps.  This is called from the traps table and
  * triggers the proper die notification.
  */
 asmlinkage void uprobe_trap(struct pt_regs *regs,
 			    unsigned long trap_level)
 {
 	BUG_ON(trap_level != 0x173 && trap_level != 0x174);

 	/* We are only interested in user-mode code.  Uprobe traps
 	 * shall not be present in kernel code.
 	 */
 	if (!user_mode(regs)) {
 		local_irq_enable();
 		bad_trap(regs, trap_level);
 		return;
 	}

 	/* trap_level == 0x173 --> ta 0x73
 	 * trap_level == 0x174 --> ta 0x74
 	 */
 	if (notify_die((trap_level == 0x173) ? DIE_BPT : DIE_SSTEP,
 				(trap_level == 0x173) ? "bpt" : "sstep",
 				regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
 		bad_trap(regs, trap_level);
 }

 /* Callback routine for handling die notifications.
 */
 int arch_uprobe_exception_notify(struct notifier_block *self,
 				 unsigned long val, void *data)
 {
 	int ret = NOTIFY_DONE;
 	struct die_args *args = (struct die_args *)data;

 	/* We are only interested in userspace traps */
 	if (args->regs && !user_mode(args->regs))
 		return NOTIFY_DONE;

 	switch (val) {
 	case DIE_BPT:
 		if (uprobe_pre_sstep_notifier(args->regs))
 			ret = NOTIFY_STOP;
 		break;

 	case DIE_SSTEP:
 		if (uprobe_post_sstep_notifier(args->regs))
 			ret = NOTIFY_STOP;

 	default:
 		break;
 	}

 	return ret;
 }

 /* This function gets called when a XOL instruction either gets
  * trapped or the thread has a fatal signal, so reset the instruction
  * pointer to its probed address.
  */
 void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 {
 	struct uprobe_task *utask = current->utask;

 	instruction_pointer_set(regs, utask->vaddr);
 }

 /* If xol insn itself traps and generates a signal(Say,
  * SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
  * instruction jumps back to its own address.
  */
 bool arch_uprobe_xol_was_trapped(struct task_struct *t)
 {
 	return false;
 }

 unsigned long
 arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
 				  struct pt_regs *regs)
 {
 	unsigned long orig_ret_vaddr = regs->u_regs[UREG_I7];

 	regs->u_regs[UREG_I7] = trampoline_vaddr-8;

 	return orig_ret_vaddr + 8;
 }
	/*
	* User-space Probes (UProbes) for sparc
	*
	* Copyright (C) 2013 Oracle Inc.
	*
	* 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, see <http://www.gnu.org/licenses/>.
	*
	* Authors:
	* Jose E. Marchesi <jose.marchesi@oracle.com>
	* Eric Saint Etienne <eric.saint.etienne@oracle.com>
	*/

	#include <linux/kernel.h>
	#include <linux/highmem.h>
	#include <linux/uprobes.h>
	#include <linux/uaccess.h>
	#include <linux/sched.h> /* For struct task_struct */
	#include <linux/kdebug.h>

	#include <asm/cacheflush.h>

	/* Compute the address of the breakpoint instruction and return it.
	*
	* Note that uprobe_get_swbp_addr is defined as a weak symbol in
	* kernel/events/uprobe.c.
	*/
	unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
	{
	return instruction_pointer(regs);
	}

	static void copy_to_page(struct page *page, unsigned long vaddr,
	const void *src, int len)
	{
	void *kaddr = kmap_atomic(page);

	memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
	kunmap_atomic(kaddr);
	}

	/* Fill in the xol area with the probed instruction followed by the
	* single-step trap. Some fixups in the copied instruction are
	* performed at this point.
	*
	* Note that uprobe_xol_copy is defined as a weak symbol in
	* kernel/events/uprobe.c.
	*/
	void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
	void *src, unsigned long len)
	{
	const u32 stp_insn = UPROBE_STP_INSN;
	u32 insn = (u32 ) src;

	/* Branches annulling their delay slot must be fixed to not do
	* so. Clearing the annul bit on these instructions we can be
	* sure the single-step breakpoint in the XOL slot will be
	* executed.
	*/

	u32 op = (insn >> 30) & 0x3;
	u32 op2 = (insn >> 22) & 0x7;

	if (op == 0 &&
	(op2 == 1 \|\| op2 == 2 \|\| op2 == 3 \|\| op2 == 5 \|\| op2 == 6) &&
	(insn & ANNUL_BIT) == ANNUL_BIT)
	insn &= ~ANNUL_BIT;

	copy_to_page(page, vaddr, &insn, len);
	copy_to_page(page, vaddr+len, &stp_insn, 4);
	}


	/* Instruction analysis/validity.
	*
	* This function returns 0 on success or a -ve number on error.
	*/
	int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
	struct mm_struct *mm, unsigned long addr)
	{
	/* Any unsupported instruction? Then return -EINVAL */
	return 0;
	}

	/* If INSN is a relative control transfer instruction, return the
	* corrected branch destination value.
	*
	* Note that regs->tpc and regs->tnpc still hold the values of the
	* program counters at the time of the single-step trap due to the
	* execution of the UPROBE_STP_INSN at utask->xol_vaddr + 4.
	*
	*/
	static unsigned long relbranch_fixup(u32 insn, struct uprobe_task *utask,
	struct pt_regs *regs)
	{
	/* Branch not taken, no mods necessary. */
	if (regs->tnpc == regs->tpc + 0x4UL)
	return utask->autask.saved_tnpc + 0x4UL;

	/* The three cases are call, branch w/prediction,
	* and traditional branch.
	*/
	if ((insn & 0xc0000000) == 0x40000000 \|\|
	(insn & 0xc1c00000) == 0x00400000 \|\|
	(insn & 0xc1c00000) == 0x00800000) {
	unsigned long real_pc = (unsigned long) utask->vaddr;
	unsigned long ixol_addr = utask->xol_vaddr;

	/* The instruction did all the work for us
	* already, just apply the offset to the correct
	* instruction location.
	*/
	return (real_pc + (regs->tnpc - ixol_addr));
	}

	/* It is jmpl or some other absolute PC modification instruction,
	* leave NPC as-is.
	*/
	return regs->tnpc;
	}

	/* If INSN is an instruction which writes its PC location
	* into a destination register, fix that up.
	*/
	static int retpc_fixup(struct pt_regs *regs, u32 insn,
	unsigned long real_pc)
	{
	unsigned long *slot = NULL;
	int rc = 0;

	/* Simplest case is 'call', which always uses %o7 */
	if ((insn & 0xc0000000) == 0x40000000)
	slot = &regs->u_regs[UREG_I7];

	/* 'jmpl' encodes the register inside of the opcode */
	if ((insn & 0xc1f80000) == 0x81c00000) {
	unsigned long rd = ((insn >> 25) & 0x1f);

	if (rd <= 15) {
	slot = &regs->u_regs[rd];
	} else {
	unsigned long fp = regs->u_regs[UREG_FP];
	/* Hard case, it goes onto the stack. */
	flushw_all();

	rd -= 16;
	if (test_thread_64bit_stack(fp)) {
	unsigned long __user *uslot =
	(unsigned long __user *) (fp + STACK_BIAS) + rd;
	rc = __put_user(real_pc, uslot);
	} else {
	unsigned int __user *uslot = (unsigned int
	__user *) fp + rd;
	rc = __put_user((u32) real_pc, uslot);
	}
	}
	}
	if (slot != NULL)
	*slot = real_pc;
	return rc;
	}

	/* Single-stepping can be avoided for certain instructions: NOPs and
	* instructions that can be emulated. This function determines
	* whether the instruction where the uprobe is installed falls in one
	* of these cases and emulates it.
	*
	* This function returns true if the single-stepping can be skipped,
	* false otherwise.
	*/
	bool arch_uprobe_skip_sstep(struct arch_uprobe auprobe, struct pt_regs regs)
	{
	/* We currently only emulate NOP instructions.
	*/

	if (auprobe->ixol == (1 << 24)) {
	regs->tnpc += 4;
	regs->tpc += 4;
	return true;
	}

	return false;
	}

	/* Prepare to execute out of line. At this point
	* current->utask->xol_vaddr points to an allocated XOL slot properly
	* initialized with the original instruction and the single-stepping
	* trap instruction.
	*
	* This function returns 0 on success, any other number on error.
	*/
	int arch_uprobe_pre_xol(struct arch_uprobe auprobe, struct pt_regs regs)
	{
	struct uprobe_task *utask = current->utask;
	struct arch_uprobe_task *autask = &current->utask->autask;

	/* Save the current program counters so they can be restored
	* later.
	*/
	autask->saved_tpc = regs->tpc;
	autask->saved_tnpc = regs->tnpc;

	/* Adjust PC and NPC so the first instruction in the XOL slot
	* will be executed by the user task.
	*/
	instruction_pointer_set(regs, utask->xol_vaddr);

	return 0;
	}

	/* Prepare to resume execution after the single-step. Called after
	* single-stepping. 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.
	*
	* This function returns 0 on success, any other number on error.
	*/
	int arch_uprobe_post_xol(struct arch_uprobe auprobe, struct pt_regs regs)
	{
	struct uprobe_task *utask = current->utask;
	struct arch_uprobe_task *autask = &utask->autask;
	u32 insn = auprobe->ixol;
	int rc = 0;

	if (utask->state == UTASK_SSTEP_ACK) {
	regs->tnpc = relbranch_fixup(insn, utask, regs);
	regs->tpc = autask->saved_tnpc;
	rc = retpc_fixup(regs, insn, (unsigned long) utask->vaddr);
	} else {
	regs->tnpc = utask->vaddr+4;
	regs->tpc = autask->saved_tnpc+4;
	}
	return rc;
	}

	/* Handler for uprobe traps. This is called from the traps table and
	* triggers the proper die notification.
	*/
	asmlinkage void uprobe_trap(struct pt_regs *regs,
	unsigned long trap_level)
	{
	BUG_ON(trap_level != 0x173 && trap_level != 0x174);

	/* We are only interested in user-mode code. Uprobe traps
	* shall not be present in kernel code.
	*/
	if (!user_mode(regs)) {
	local_irq_enable();
	bad_trap(regs, trap_level);
	return;
	}

	/* trap_level == 0x173 --> ta 0x73
	* trap_level == 0x174 --> ta 0x74
	*/
	if (notify_die((trap_level == 0x173) ? DIE_BPT : DIE_SSTEP,
	(trap_level == 0x173) ? "bpt" : "sstep",
	regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP)
	bad_trap(regs, trap_level);
	}

	/* Callback routine for handling die notifications.
	*/
	int arch_uprobe_exception_notify(struct notifier_block *self,
	unsigned long val, void *data)
	{
	int ret = NOTIFY_DONE;
	struct die_args args = (struct die_args )data;

	/* We are only interested in userspace traps */
	if (args->regs && !user_mode(args->regs))
	return NOTIFY_DONE;

	switch (val) {
	case DIE_BPT:
	if (uprobe_pre_sstep_notifier(args->regs))
	ret = NOTIFY_STOP;
	break;

	case DIE_SSTEP:
	if (uprobe_post_sstep_notifier(args->regs))
	ret = NOTIFY_STOP;

	default:
	break;
	}

	return ret;
	}

	/* This function gets called when a XOL instruction either gets
	* trapped or the thread has a fatal signal, so reset the instruction
	* pointer to its probed address.
	*/
	void arch_uprobe_abort_xol(struct arch_uprobe auprobe, struct pt_regs regs)
	{
	struct uprobe_task *utask = current->utask;

	instruction_pointer_set(regs, utask->vaddr);
	}

	/* If xol insn itself traps and generates a signal(Say,
	* SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
	* instruction jumps back to its own address.
	*/
	bool arch_uprobe_xol_was_trapped(struct task_struct *t)
	{
	return false;
	}

	unsigned long
	arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
	struct pt_regs *regs)
	{
	unsigned long orig_ret_vaddr = regs->u_regs[UREG_I7];

	regs->u_regs[UREG_I7] = trampoline_vaddr-8;

	return orig_ret_vaddr + 8;
	}