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/*
* 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
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