arch/powerpc/lib/code-patching.c - linux - Git at Google

 /*
  *  Copyright 2008 Michael Ellerman, IBM Corporation.
  *
  *  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.
  */

 #include <linux/kernel.h>
 #include <linux/vmalloc.h>
 #include <linux/init.h>
 #include <linux/mm.h>
 #include <asm/page.h>
 #include <asm/code-patching.h>
 #include <asm/uaccess.h>


 int patch_instruction(unsigned int *addr, unsigned int instr)
 {
 	int err;

 	err = __put_user(instr, addr);
 	if (err)
 		return err;
 	asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
 	return 0;
 }

 int patch_branch(unsigned int *addr, unsigned long target, int flags)
 {
 	return patch_instruction(addr, create_branch(addr, target, flags));
 }

 unsigned int create_branch(const unsigned int *addr,
 			   unsigned long target, int flags)
 {
 	unsigned int instruction;
 	long offset;

 	offset = target;
 	if (! (flags & BRANCH_ABSOLUTE))
 		offset = offset - (unsigned long)addr;

 	/* Check we can represent the target in the instruction format */
 	if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
 		return 0;

 	/* Mask out the flags and target, so they don't step on each other. */
 	instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);

 	return instruction;
 }

 unsigned int create_cond_branch(const unsigned int *addr,
 				unsigned long target, int flags)
 {
 	unsigned int instruction;
 	long offset;

 	offset = target;
 	if (! (flags & BRANCH_ABSOLUTE))
 		offset = offset - (unsigned long)addr;

 	/* Check we can represent the target in the instruction format */
 	if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
 		return 0;

 	/* Mask out the flags and target, so they don't step on each other. */
 	instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);

 	return instruction;
 }

 static unsigned int branch_opcode(unsigned int instr)
 {
 	return (instr >> 26) & 0x3F;
 }

 static int instr_is_branch_iform(unsigned int instr)
 {
 	return branch_opcode(instr) == 18;
 }

 static int instr_is_branch_bform(unsigned int instr)
 {
 	return branch_opcode(instr) == 16;
 }

 int instr_is_relative_branch(unsigned int instr)
 {
 	if (instr & BRANCH_ABSOLUTE)
 		return 0;

 	return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
 }

 static unsigned long branch_iform_target(const unsigned int *instr)
 {
 	signed long imm;

 	imm = *instr & 0x3FFFFFC;

 	/* If the top bit of the immediate value is set this is negative */
 	if (imm & 0x2000000)
 		imm -= 0x4000000;

 	if ((*instr & BRANCH_ABSOLUTE) == 0)
 		imm += (unsigned long)instr;

 	return (unsigned long)imm;
 }

 static unsigned long branch_bform_target(const unsigned int *instr)
 {
 	signed long imm;

 	imm = *instr & 0xFFFC;

 	/* If the top bit of the immediate value is set this is negative */
 	if (imm & 0x8000)
 		imm -= 0x10000;

 	if ((*instr & BRANCH_ABSOLUTE) == 0)
 		imm += (unsigned long)instr;

 	return (unsigned long)imm;
 }

 unsigned long branch_target(const unsigned int *instr)
 {
 	if (instr_is_branch_iform(*instr))
 		return branch_iform_target(instr);
 	else if (instr_is_branch_bform(*instr))
 		return branch_bform_target(instr);

 	return 0;
 }

 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
 {
 	if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
 		return branch_target(instr) == addr;

 	return 0;
 }

 unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
 {
 	unsigned long target;

 	target = branch_target(src);

 	if (instr_is_branch_iform(*src))
 		return create_branch(dest, target, *src);
 	else if (instr_is_branch_bform(*src))
 		return create_cond_branch(dest, target, *src);

 	return 0;
 }


 #ifdef CONFIG_CODE_PATCHING_SELFTEST

 static void __init test_trampoline(void)
 {
 	asm ("nop;\n");
 }

 #define check(x)	\
 	if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);

 static void __init test_branch_iform(void)
 {
 	unsigned int instr;
 	unsigned long addr;

 	addr = (unsigned long)&instr;

 	/* The simplest case, branch to self, no flags */
 	check(instr_is_branch_iform(0x48000000));
 	/* All bits of target set, and flags */
 	check(instr_is_branch_iform(0x4bffffff));
 	/* High bit of opcode set, which is wrong */
 	check(!instr_is_branch_iform(0xcbffffff));
 	/* Middle bits of opcode set, which is wrong */
 	check(!instr_is_branch_iform(0x7bffffff));

 	/* Simplest case, branch to self with link */
 	check(instr_is_branch_iform(0x48000001));
 	/* All bits of targets set */
 	check(instr_is_branch_iform(0x4bfffffd));
 	/* Some bits of targets set */
 	check(instr_is_branch_iform(0x4bff00fd));
 	/* Must be a valid branch to start with */
 	check(!instr_is_branch_iform(0x7bfffffd));

 	/* Absolute branch to 0x100 */
 	instr = 0x48000103;
 	check(instr_is_branch_to_addr(&instr, 0x100));
 	/* Absolute branch to 0x420fc */
 	instr = 0x480420ff;
 	check(instr_is_branch_to_addr(&instr, 0x420fc));
 	/* Maximum positive relative branch, + 20MB - 4B */
 	instr = 0x49fffffc;
 	check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
 	/* Smallest negative relative branch, - 4B */
 	instr = 0x4bfffffc;
 	check(instr_is_branch_to_addr(&instr, addr - 4));
 	/* Largest negative relative branch, - 32 MB */
 	instr = 0x4a000000;
 	check(instr_is_branch_to_addr(&instr, addr - 0x2000000));

 	/* Branch to self, with link */
 	instr = create_branch(&instr, addr, BRANCH_SET_LINK);
 	check(instr_is_branch_to_addr(&instr, addr));

 	/* Branch to self - 0x100, with link */
 	instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
 	check(instr_is_branch_to_addr(&instr, addr - 0x100));

 	/* Branch to self + 0x100, no link */
 	instr = create_branch(&instr, addr + 0x100, 0);
 	check(instr_is_branch_to_addr(&instr, addr + 0x100));

 	/* Maximum relative negative offset, - 32 MB */
 	instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
 	check(instr_is_branch_to_addr(&instr, addr - 0x2000000));

 	/* Out of range relative negative offset, - 32 MB + 4*/
 	instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
 	check(instr == 0);

 	/* Out of range relative positive offset, + 32 MB */
 	instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
 	check(instr == 0);

 	/* Unaligned target */
 	instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
 	check(instr == 0);

 	/* Check flags are masked correctly */
 	instr = create_branch(&instr, addr, 0xFFFFFFFC);
 	check(instr_is_branch_to_addr(&instr, addr));
 	check(instr == 0x48000000);
 }

 static void __init test_create_function_call(void)
 {
 	unsigned int *iptr;
 	unsigned long dest;

 	/* Check we can create a function call */
 	iptr = (unsigned int *)ppc_function_entry(test_trampoline);
 	dest = ppc_function_entry(test_create_function_call);
 	patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
 	check(instr_is_branch_to_addr(iptr, dest));
 }

 static void __init test_branch_bform(void)
 {
 	unsigned long addr;
 	unsigned int *iptr, instr, flags;

 	iptr = &instr;
 	addr = (unsigned long)iptr;

 	/* The simplest case, branch to self, no flags */
 	check(instr_is_branch_bform(0x40000000));
 	/* All bits of target set, and flags */
 	check(instr_is_branch_bform(0x43ffffff));
 	/* High bit of opcode set, which is wrong */
 	check(!instr_is_branch_bform(0xc3ffffff));
 	/* Middle bits of opcode set, which is wrong */
 	check(!instr_is_branch_bform(0x7bffffff));

 	/* Absolute conditional branch to 0x100 */
 	instr = 0x43ff0103;
 	check(instr_is_branch_to_addr(&instr, 0x100));
 	/* Absolute conditional branch to 0x20fc */
 	instr = 0x43ff20ff;
 	check(instr_is_branch_to_addr(&instr, 0x20fc));
 	/* Maximum positive relative conditional branch, + 32 KB - 4B */
 	instr = 0x43ff7ffc;
 	check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
 	/* Smallest negative relative conditional branch, - 4B */
 	instr = 0x43fffffc;
 	check(instr_is_branch_to_addr(&instr, addr - 4));
 	/* Largest negative relative conditional branch, - 32 KB */
 	instr = 0x43ff8000;
 	check(instr_is_branch_to_addr(&instr, addr - 0x8000));

 	/* All condition code bits set & link */
 	flags = 0x3ff000 | BRANCH_SET_LINK;

 	/* Branch to self */
 	instr = create_cond_branch(iptr, addr, flags);
 	check(instr_is_branch_to_addr(&instr, addr));

 	/* Branch to self - 0x100 */
 	instr = create_cond_branch(iptr, addr - 0x100, flags);
 	check(instr_is_branch_to_addr(&instr, addr - 0x100));

 	/* Branch to self + 0x100 */
 	instr = create_cond_branch(iptr, addr + 0x100, flags);
 	check(instr_is_branch_to_addr(&instr, addr + 0x100));

 	/* Maximum relative negative offset, - 32 KB */
 	instr = create_cond_branch(iptr, addr - 0x8000, flags);
 	check(instr_is_branch_to_addr(&instr, addr - 0x8000));

 	/* Out of range relative negative offset, - 32 KB + 4*/
 	instr = create_cond_branch(iptr, addr - 0x8004, flags);
 	check(instr == 0);

 	/* Out of range relative positive offset, + 32 KB */
 	instr = create_cond_branch(iptr, addr + 0x8000, flags);
 	check(instr == 0);

 	/* Unaligned target */
 	instr = create_cond_branch(iptr, addr + 3, flags);
 	check(instr == 0);

 	/* Check flags are masked correctly */
 	instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
 	check(instr_is_branch_to_addr(&instr, addr));
 	check(instr == 0x43FF0000);
 }

 static void __init test_translate_branch(void)
 {
 	unsigned long addr;
 	unsigned int *p, *q;
 	void *buf;

 	buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
 	check(buf);
 	if (!buf)
 		return;

 	/* Simple case, branch to self moved a little */
 	p = buf;
 	addr = (unsigned long)p;
 	patch_branch(p, addr, 0);
 	check(instr_is_branch_to_addr(p, addr));
 	q = p + 1;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(q, addr));

 	/* Maximum negative case, move b . to addr + 32 MB */
 	p = buf;
 	addr = (unsigned long)p;
 	patch_branch(p, addr, 0);
 	q = buf + 0x2000000;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));
 	check(*q == 0x4a000000);

 	/* Maximum positive case, move x to x - 32 MB + 4 */
 	p = buf + 0x2000000;
 	addr = (unsigned long)p;
 	patch_branch(p, addr, 0);
 	q = buf + 4;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));
 	check(*q == 0x49fffffc);

 	/* Jump to x + 16 MB moved to x + 20 MB */
 	p = buf;
 	addr = 0x1000000 + (unsigned long)buf;
 	patch_branch(p, addr, BRANCH_SET_LINK);
 	q = buf + 0x1400000;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));

 	/* Jump to x + 16 MB moved to x - 16 MB + 4 */
 	p = buf + 0x1000000;
 	addr = 0x2000000 + (unsigned long)buf;
 	patch_branch(p, addr, 0);
 	q = buf + 4;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));


 	/* Conditional branch tests */

 	/* Simple case, branch to self moved a little */
 	p = buf;
 	addr = (unsigned long)p;
 	patch_instruction(p, create_cond_branch(p, addr, 0));
 	check(instr_is_branch_to_addr(p, addr));
 	q = p + 1;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(q, addr));

 	/* Maximum negative case, move b . to addr + 32 KB */
 	p = buf;
 	addr = (unsigned long)p;
 	patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 	q = buf + 0x8000;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));
 	check(*q == 0x43ff8000);

 	/* Maximum positive case, move x to x - 32 KB + 4 */
 	p = buf + 0x8000;
 	addr = (unsigned long)p;
 	patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
 	q = buf + 4;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));
 	check(*q == 0x43ff7ffc);

 	/* Jump to x + 12 KB moved to x + 20 KB */
 	p = buf;
 	addr = 0x3000 + (unsigned long)buf;
 	patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
 	q = buf + 0x5000;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));

 	/* Jump to x + 8 KB moved to x - 8 KB + 4 */
 	p = buf + 0x2000;
 	addr = 0x4000 + (unsigned long)buf;
 	patch_instruction(p, create_cond_branch(p, addr, 0));
 	q = buf + 4;
 	patch_instruction(q, translate_branch(q, p));
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));

 	/* Free the buffer we were using */
 	vfree(buf);
 }

 static int __init test_code_patching(void)
 {
 	printk(KERN_DEBUG "Running code patching self-tests ...\n");

 	test_branch_iform();
 	test_branch_bform();
 	test_create_function_call();
 	test_translate_branch();

 	return 0;
 }
 late_initcall(test_code_patching);

 #endif /* CONFIG_CODE_PATCHING_SELFTEST */
	/*
	* Copyright 2008 Michael Ellerman, IBM Corporation.
	*
	* 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.
	*/

	#include <linux/kernel.h>
	#include <linux/vmalloc.h>
	#include <linux/init.h>
	#include <linux/mm.h>
	#include <asm/page.h>
	#include <asm/code-patching.h>
	#include <asm/uaccess.h>


	int patch_instruction(unsigned int *addr, unsigned int instr)
	{
	int err;

	err = __put_user(instr, addr);
	if (err)
	return err;
	asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
	return 0;
	}

	int patch_branch(unsigned int *addr, unsigned long target, int flags)
	{
	return patch_instruction(addr, create_branch(addr, target, flags));
	}

	unsigned int create_branch(const unsigned int *addr,
	unsigned long target, int flags)
	{
	unsigned int instruction;
	long offset;

	offset = target;
	if (! (flags & BRANCH_ABSOLUTE))
	offset = offset - (unsigned long)addr;

	/* Check we can represent the target in the instruction format */
	if (offset < -0x2000000 \|\| offset > 0x1fffffc \|\| offset & 0x3)
	return 0;

	/* Mask out the flags and target, so they don't step on each other. */
	instruction = 0x48000000 \| (flags & 0x3) \| (offset & 0x03FFFFFC);

	return instruction;
	}

	unsigned int create_cond_branch(const unsigned int *addr,
	unsigned long target, int flags)
	{
	unsigned int instruction;
	long offset;

	offset = target;
	if (! (flags & BRANCH_ABSOLUTE))
	offset = offset - (unsigned long)addr;

	/* Check we can represent the target in the instruction format */
	if (offset < -0x8000 \|\| offset > 0x7FFF \|\| offset & 0x3)
	return 0;

	/* Mask out the flags and target, so they don't step on each other. */
	instruction = 0x40000000 \| (flags & 0x3FF0003) \| (offset & 0xFFFC);

	return instruction;
	}

	static unsigned int branch_opcode(unsigned int instr)
	{
	return (instr >> 26) & 0x3F;
	}

	static int instr_is_branch_iform(unsigned int instr)
	{
	return branch_opcode(instr) == 18;
	}

	static int instr_is_branch_bform(unsigned int instr)
	{
	return branch_opcode(instr) == 16;
	}

	int instr_is_relative_branch(unsigned int instr)
	{
	if (instr & BRANCH_ABSOLUTE)
	return 0;

	return instr_is_branch_iform(instr) \|\| instr_is_branch_bform(instr);
	}

	static unsigned long branch_iform_target(const unsigned int *instr)
	{
	signed long imm;

	imm = *instr & 0x3FFFFFC;

	/* If the top bit of the immediate value is set this is negative */
	if (imm & 0x2000000)
	imm -= 0x4000000;

	if ((*instr & BRANCH_ABSOLUTE) == 0)
	imm += (unsigned long)instr;

	return (unsigned long)imm;
	}

	static unsigned long branch_bform_target(const unsigned int *instr)
	{
	signed long imm;

	imm = *instr & 0xFFFC;

	/* If the top bit of the immediate value is set this is negative */
	if (imm & 0x8000)
	imm -= 0x10000;

	if ((*instr & BRANCH_ABSOLUTE) == 0)
	imm += (unsigned long)instr;

	return (unsigned long)imm;
	}

	unsigned long branch_target(const unsigned int *instr)
	{
	if (instr_is_branch_iform(*instr))
	return branch_iform_target(instr);
	else if (instr_is_branch_bform(*instr))
	return branch_bform_target(instr);

	return 0;
	}

	int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
	{
	if (instr_is_branch_iform(instr) \|\| instr_is_branch_bform(instr))
	return branch_target(instr) == addr;

	return 0;
	}

	unsigned int translate_branch(const unsigned int dest, const unsigned int src)
	{
	unsigned long target;

	target = branch_target(src);

	if (instr_is_branch_iform(*src))
	return create_branch(dest, target, *src);
	else if (instr_is_branch_bform(*src))
	return create_cond_branch(dest, target, *src);

	return 0;
	}


	#ifdef CONFIG_CODE_PATCHING_SELFTEST

	static void __init test_trampoline(void)
	{
	asm ("nop;\n");
	}

	#define check(x) \
	if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);

	static void __init test_branch_iform(void)
	{
	unsigned int instr;
	unsigned long addr;

	addr = (unsigned long)&instr;

	/* The simplest case, branch to self, no flags */
	check(instr_is_branch_iform(0x48000000));
	/* All bits of target set, and flags */
	check(instr_is_branch_iform(0x4bffffff));
	/* High bit of opcode set, which is wrong */
	check(!instr_is_branch_iform(0xcbffffff));
	/* Middle bits of opcode set, which is wrong */
	check(!instr_is_branch_iform(0x7bffffff));

	/* Simplest case, branch to self with link */
	check(instr_is_branch_iform(0x48000001));
	/* All bits of targets set */
	check(instr_is_branch_iform(0x4bfffffd));
	/* Some bits of targets set */
	check(instr_is_branch_iform(0x4bff00fd));
	/* Must be a valid branch to start with */
	check(!instr_is_branch_iform(0x7bfffffd));

	/* Absolute branch to 0x100 */
	instr = 0x48000103;
	check(instr_is_branch_to_addr(&instr, 0x100));
	/* Absolute branch to 0x420fc */
	instr = 0x480420ff;
	check(instr_is_branch_to_addr(&instr, 0x420fc));
	/* Maximum positive relative branch, + 20MB - 4B */
	instr = 0x49fffffc;
	check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
	/* Smallest negative relative branch, - 4B */
	instr = 0x4bfffffc;
	check(instr_is_branch_to_addr(&instr, addr - 4));
	/* Largest negative relative branch, - 32 MB */
	instr = 0x4a000000;
	check(instr_is_branch_to_addr(&instr, addr - 0x2000000));

	/* Branch to self, with link */
	instr = create_branch(&instr, addr, BRANCH_SET_LINK);
	check(instr_is_branch_to_addr(&instr, addr));

	/* Branch to self - 0x100, with link */
	instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
	check(instr_is_branch_to_addr(&instr, addr - 0x100));

	/* Branch to self + 0x100, no link */
	instr = create_branch(&instr, addr + 0x100, 0);
	check(instr_is_branch_to_addr(&instr, addr + 0x100));

	/* Maximum relative negative offset, - 32 MB */
	instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
	check(instr_is_branch_to_addr(&instr, addr - 0x2000000));

	/* Out of range relative negative offset, - 32 MB + 4*/
	instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
	check(instr == 0);

	/* Out of range relative positive offset, + 32 MB */
	instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
	check(instr == 0);

	/* Unaligned target */
	instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
	check(instr == 0);

	/* Check flags are masked correctly */
	instr = create_branch(&instr, addr, 0xFFFFFFFC);
	check(instr_is_branch_to_addr(&instr, addr));
	check(instr == 0x48000000);
	}

	static void __init test_create_function_call(void)
	{
	unsigned int *iptr;
	unsigned long dest;

	/* Check we can create a function call */
	iptr = (unsigned int *)ppc_function_entry(test_trampoline);
	dest = ppc_function_entry(test_create_function_call);
	patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
	check(instr_is_branch_to_addr(iptr, dest));
	}

	static void __init test_branch_bform(void)
	{
	unsigned long addr;
	unsigned int *iptr, instr, flags;

	iptr = &instr;
	addr = (unsigned long)iptr;

	/* The simplest case, branch to self, no flags */
	check(instr_is_branch_bform(0x40000000));
	/* All bits of target set, and flags */
	check(instr_is_branch_bform(0x43ffffff));
	/* High bit of opcode set, which is wrong */
	check(!instr_is_branch_bform(0xc3ffffff));
	/* Middle bits of opcode set, which is wrong */
	check(!instr_is_branch_bform(0x7bffffff));

	/* Absolute conditional branch to 0x100 */
	instr = 0x43ff0103;
	check(instr_is_branch_to_addr(&instr, 0x100));
	/* Absolute conditional branch to 0x20fc */
	instr = 0x43ff20ff;
	check(instr_is_branch_to_addr(&instr, 0x20fc));
	/* Maximum positive relative conditional branch, + 32 KB - 4B */
	instr = 0x43ff7ffc;
	check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
	/* Smallest negative relative conditional branch, - 4B */
	instr = 0x43fffffc;
	check(instr_is_branch_to_addr(&instr, addr - 4));
	/* Largest negative relative conditional branch, - 32 KB */
	instr = 0x43ff8000;
	check(instr_is_branch_to_addr(&instr, addr - 0x8000));

	/* All condition code bits set & link */
	flags = 0x3ff000 \| BRANCH_SET_LINK;

	/* Branch to self */
	instr = create_cond_branch(iptr, addr, flags);
	check(instr_is_branch_to_addr(&instr, addr));

	/* Branch to self - 0x100 */
	instr = create_cond_branch(iptr, addr - 0x100, flags);
	check(instr_is_branch_to_addr(&instr, addr - 0x100));

	/* Branch to self + 0x100 */
	instr = create_cond_branch(iptr, addr + 0x100, flags);
	check(instr_is_branch_to_addr(&instr, addr + 0x100));

	/* Maximum relative negative offset, - 32 KB */
	instr = create_cond_branch(iptr, addr - 0x8000, flags);
	check(instr_is_branch_to_addr(&instr, addr - 0x8000));

	/* Out of range relative negative offset, - 32 KB + 4*/
	instr = create_cond_branch(iptr, addr - 0x8004, flags);
	check(instr == 0);

	/* Out of range relative positive offset, + 32 KB */
	instr = create_cond_branch(iptr, addr + 0x8000, flags);
	check(instr == 0);

	/* Unaligned target */
	instr = create_cond_branch(iptr, addr + 3, flags);
	check(instr == 0);

	/* Check flags are masked correctly */
	instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
	check(instr_is_branch_to_addr(&instr, addr));
	check(instr == 0x43FF0000);
	}

	static void __init test_translate_branch(void)
	{
	unsigned long addr;
	unsigned int p, q;
	void *buf;

	buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
	check(buf);
	if (!buf)
	return;

	/* Simple case, branch to self moved a little */
	p = buf;
	addr = (unsigned long)p;
	patch_branch(p, addr, 0);
	check(instr_is_branch_to_addr(p, addr));
	q = p + 1;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(q, addr));

	/* Maximum negative case, move b . to addr + 32 MB */
	p = buf;
	addr = (unsigned long)p;
	patch_branch(p, addr, 0);
	q = buf + 0x2000000;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));
	check(*q == 0x4a000000);

	/* Maximum positive case, move x to x - 32 MB + 4 */
	p = buf + 0x2000000;
	addr = (unsigned long)p;
	patch_branch(p, addr, 0);
	q = buf + 4;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));
	check(*q == 0x49fffffc);

	/* Jump to x + 16 MB moved to x + 20 MB */
	p = buf;
	addr = 0x1000000 + (unsigned long)buf;
	patch_branch(p, addr, BRANCH_SET_LINK);
	q = buf + 0x1400000;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));

	/* Jump to x + 16 MB moved to x - 16 MB + 4 */
	p = buf + 0x1000000;
	addr = 0x2000000 + (unsigned long)buf;
	patch_branch(p, addr, 0);
	q = buf + 4;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));


	/* Conditional branch tests */

	/* Simple case, branch to self moved a little */
	p = buf;
	addr = (unsigned long)p;
	patch_instruction(p, create_cond_branch(p, addr, 0));
	check(instr_is_branch_to_addr(p, addr));
	q = p + 1;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(q, addr));

	/* Maximum negative case, move b . to addr + 32 KB */
	p = buf;
	addr = (unsigned long)p;
	patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
	q = buf + 0x8000;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));
	check(*q == 0x43ff8000);

	/* Maximum positive case, move x to x - 32 KB + 4 */
	p = buf + 0x8000;
	addr = (unsigned long)p;
	patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
	q = buf + 4;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));
	check(*q == 0x43ff7ffc);

	/* Jump to x + 12 KB moved to x + 20 KB */
	p = buf;
	addr = 0x3000 + (unsigned long)buf;
	patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
	q = buf + 0x5000;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));

	/* Jump to x + 8 KB moved to x - 8 KB + 4 */
	p = buf + 0x2000;
	addr = 0x4000 + (unsigned long)buf;
	patch_instruction(p, create_cond_branch(p, addr, 0));
	q = buf + 4;
	patch_instruction(q, translate_branch(q, p));
	check(instr_is_branch_to_addr(p, addr));
	check(instr_is_branch_to_addr(q, addr));

	/* Free the buffer we were using */
	vfree(buf);
	}

	static int __init test_code_patching(void)
	{
	printk(KERN_DEBUG "Running code patching self-tests ...\n");

	test_branch_iform();
	test_branch_bform();
	test_create_function_call();
	test_translate_branch();

	return 0;
	}
	late_initcall(test_code_patching);

	#endif /* CONFIG_CODE_PATCHING_SELFTEST */