mirror of https://gitee.com/openkylin/linux.git
515 lines
14 KiB
C
515 lines
14 KiB
C
/*
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* Copyright 2008 Michael Ellerman, IBM Corporation.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/kernel.h>
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#include <linux/vmalloc.h>
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#include <linux/init.h>
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#include <linux/mm.h>
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#include <asm/page.h>
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#include <asm/code-patching.h>
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#include <linux/uaccess.h>
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#include <linux/kprobes.h>
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int patch_instruction(unsigned int *addr, unsigned int instr)
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{
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int err;
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__put_user_size(instr, addr, 4, err);
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if (err)
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return err;
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asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
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return 0;
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}
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int patch_branch(unsigned int *addr, unsigned long target, int flags)
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{
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return patch_instruction(addr, create_branch(addr, target, flags));
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}
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bool is_offset_in_branch_range(long offset)
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{
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/*
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* Powerpc branch instruction is :
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*
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* 0 6 30 31
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* +---------+----------------+---+---+
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* | opcode | LI |AA |LK |
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* +---------+----------------+---+---+
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* Where AA = 0 and LK = 0
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*
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* LI is a signed 24 bits integer. The real branch offset is computed
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* by: imm32 = SignExtend(LI:'0b00', 32);
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*
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* So the maximum forward branch should be:
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* (0x007fffff << 2) = 0x01fffffc = 0x1fffffc
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* The maximum backward branch should be:
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* (0xff800000 << 2) = 0xfe000000 = -0x2000000
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*/
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return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
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}
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/*
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* Helper to check if a given instruction is a conditional branch
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* Derived from the conditional checks in analyse_instr()
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*/
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bool __kprobes is_conditional_branch(unsigned int instr)
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{
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unsigned int opcode = instr >> 26;
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if (opcode == 16) /* bc, bca, bcl, bcla */
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return true;
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if (opcode == 19) {
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switch ((instr >> 1) & 0x3ff) {
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case 16: /* bclr, bclrl */
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case 528: /* bcctr, bcctrl */
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case 560: /* bctar, bctarl */
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return true;
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}
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}
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return false;
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}
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unsigned int create_branch(const unsigned int *addr,
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unsigned long target, int flags)
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{
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unsigned int instruction;
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long offset;
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offset = target;
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if (! (flags & BRANCH_ABSOLUTE))
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offset = offset - (unsigned long)addr;
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/* Check we can represent the target in the instruction format */
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if (!is_offset_in_branch_range(offset))
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return 0;
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/* Mask out the flags and target, so they don't step on each other. */
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instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
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return instruction;
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}
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unsigned int create_cond_branch(const unsigned int *addr,
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unsigned long target, int flags)
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{
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unsigned int instruction;
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long offset;
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offset = target;
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if (! (flags & BRANCH_ABSOLUTE))
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offset = offset - (unsigned long)addr;
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/* Check we can represent the target in the instruction format */
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if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
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return 0;
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/* Mask out the flags and target, so they don't step on each other. */
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instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
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return instruction;
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}
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static unsigned int branch_opcode(unsigned int instr)
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{
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return (instr >> 26) & 0x3F;
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}
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static int instr_is_branch_iform(unsigned int instr)
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{
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return branch_opcode(instr) == 18;
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}
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static int instr_is_branch_bform(unsigned int instr)
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{
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return branch_opcode(instr) == 16;
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}
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int instr_is_relative_branch(unsigned int instr)
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{
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if (instr & BRANCH_ABSOLUTE)
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return 0;
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return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
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}
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static unsigned long branch_iform_target(const unsigned int *instr)
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{
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signed long imm;
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imm = *instr & 0x3FFFFFC;
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/* If the top bit of the immediate value is set this is negative */
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if (imm & 0x2000000)
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imm -= 0x4000000;
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if ((*instr & BRANCH_ABSOLUTE) == 0)
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imm += (unsigned long)instr;
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return (unsigned long)imm;
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}
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static unsigned long branch_bform_target(const unsigned int *instr)
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{
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signed long imm;
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imm = *instr & 0xFFFC;
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/* If the top bit of the immediate value is set this is negative */
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if (imm & 0x8000)
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imm -= 0x10000;
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if ((*instr & BRANCH_ABSOLUTE) == 0)
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imm += (unsigned long)instr;
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return (unsigned long)imm;
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}
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unsigned long branch_target(const unsigned int *instr)
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{
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if (instr_is_branch_iform(*instr))
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return branch_iform_target(instr);
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else if (instr_is_branch_bform(*instr))
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return branch_bform_target(instr);
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return 0;
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}
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int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
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{
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if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
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return branch_target(instr) == addr;
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return 0;
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}
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unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
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{
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unsigned long target;
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target = branch_target(src);
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if (instr_is_branch_iform(*src))
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return create_branch(dest, target, *src);
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else if (instr_is_branch_bform(*src))
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return create_cond_branch(dest, target, *src);
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return 0;
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}
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#ifdef CONFIG_PPC_BOOK3E_64
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void __patch_exception(int exc, unsigned long addr)
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{
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extern unsigned int interrupt_base_book3e;
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unsigned int *ibase = &interrupt_base_book3e;
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/* Our exceptions vectors start with a NOP and -then- a branch
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* to deal with single stepping from userspace which stops on
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* the second instruction. Thus we need to patch the second
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* instruction of the exception, not the first one
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*/
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patch_branch(ibase + (exc / 4) + 1, addr, 0);
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}
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#endif
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#ifdef CONFIG_CODE_PATCHING_SELFTEST
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static void __init test_trampoline(void)
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{
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asm ("nop;\n");
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}
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#define check(x) \
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if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
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static void __init test_branch_iform(void)
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{
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unsigned int instr;
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unsigned long addr;
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addr = (unsigned long)&instr;
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/* The simplest case, branch to self, no flags */
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check(instr_is_branch_iform(0x48000000));
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/* All bits of target set, and flags */
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check(instr_is_branch_iform(0x4bffffff));
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/* High bit of opcode set, which is wrong */
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check(!instr_is_branch_iform(0xcbffffff));
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/* Middle bits of opcode set, which is wrong */
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check(!instr_is_branch_iform(0x7bffffff));
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/* Simplest case, branch to self with link */
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check(instr_is_branch_iform(0x48000001));
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/* All bits of targets set */
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check(instr_is_branch_iform(0x4bfffffd));
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/* Some bits of targets set */
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check(instr_is_branch_iform(0x4bff00fd));
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/* Must be a valid branch to start with */
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check(!instr_is_branch_iform(0x7bfffffd));
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/* Absolute branch to 0x100 */
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instr = 0x48000103;
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check(instr_is_branch_to_addr(&instr, 0x100));
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/* Absolute branch to 0x420fc */
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instr = 0x480420ff;
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check(instr_is_branch_to_addr(&instr, 0x420fc));
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/* Maximum positive relative branch, + 20MB - 4B */
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instr = 0x49fffffc;
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check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
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/* Smallest negative relative branch, - 4B */
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instr = 0x4bfffffc;
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check(instr_is_branch_to_addr(&instr, addr - 4));
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/* Largest negative relative branch, - 32 MB */
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instr = 0x4a000000;
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check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
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/* Branch to self, with link */
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instr = create_branch(&instr, addr, BRANCH_SET_LINK);
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check(instr_is_branch_to_addr(&instr, addr));
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/* Branch to self - 0x100, with link */
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instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
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check(instr_is_branch_to_addr(&instr, addr - 0x100));
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/* Branch to self + 0x100, no link */
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instr = create_branch(&instr, addr + 0x100, 0);
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check(instr_is_branch_to_addr(&instr, addr + 0x100));
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/* Maximum relative negative offset, - 32 MB */
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instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
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check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
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/* Out of range relative negative offset, - 32 MB + 4*/
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instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
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check(instr == 0);
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/* Out of range relative positive offset, + 32 MB */
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instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
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check(instr == 0);
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/* Unaligned target */
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instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
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check(instr == 0);
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/* Check flags are masked correctly */
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instr = create_branch(&instr, addr, 0xFFFFFFFC);
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check(instr_is_branch_to_addr(&instr, addr));
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check(instr == 0x48000000);
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}
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static void __init test_create_function_call(void)
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{
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unsigned int *iptr;
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unsigned long dest;
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/* Check we can create a function call */
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iptr = (unsigned int *)ppc_function_entry(test_trampoline);
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dest = ppc_function_entry(test_create_function_call);
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patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
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check(instr_is_branch_to_addr(iptr, dest));
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}
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static void __init test_branch_bform(void)
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{
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unsigned long addr;
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unsigned int *iptr, instr, flags;
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iptr = &instr;
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addr = (unsigned long)iptr;
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/* The simplest case, branch to self, no flags */
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check(instr_is_branch_bform(0x40000000));
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/* All bits of target set, and flags */
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check(instr_is_branch_bform(0x43ffffff));
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/* High bit of opcode set, which is wrong */
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check(!instr_is_branch_bform(0xc3ffffff));
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/* Middle bits of opcode set, which is wrong */
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check(!instr_is_branch_bform(0x7bffffff));
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/* Absolute conditional branch to 0x100 */
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instr = 0x43ff0103;
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check(instr_is_branch_to_addr(&instr, 0x100));
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/* Absolute conditional branch to 0x20fc */
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instr = 0x43ff20ff;
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check(instr_is_branch_to_addr(&instr, 0x20fc));
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/* Maximum positive relative conditional branch, + 32 KB - 4B */
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instr = 0x43ff7ffc;
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check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
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/* Smallest negative relative conditional branch, - 4B */
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instr = 0x43fffffc;
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check(instr_is_branch_to_addr(&instr, addr - 4));
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/* Largest negative relative conditional branch, - 32 KB */
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instr = 0x43ff8000;
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check(instr_is_branch_to_addr(&instr, addr - 0x8000));
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/* All condition code bits set & link */
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flags = 0x3ff000 | BRANCH_SET_LINK;
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/* Branch to self */
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instr = create_cond_branch(iptr, addr, flags);
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check(instr_is_branch_to_addr(&instr, addr));
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/* Branch to self - 0x100 */
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instr = create_cond_branch(iptr, addr - 0x100, flags);
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check(instr_is_branch_to_addr(&instr, addr - 0x100));
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/* Branch to self + 0x100 */
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instr = create_cond_branch(iptr, addr + 0x100, flags);
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check(instr_is_branch_to_addr(&instr, addr + 0x100));
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/* Maximum relative negative offset, - 32 KB */
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instr = create_cond_branch(iptr, addr - 0x8000, flags);
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check(instr_is_branch_to_addr(&instr, addr - 0x8000));
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/* Out of range relative negative offset, - 32 KB + 4*/
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instr = create_cond_branch(iptr, addr - 0x8004, flags);
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check(instr == 0);
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/* Out of range relative positive offset, + 32 KB */
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instr = create_cond_branch(iptr, addr + 0x8000, flags);
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check(instr == 0);
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/* Unaligned target */
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instr = create_cond_branch(iptr, addr + 3, flags);
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check(instr == 0);
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/* Check flags are masked correctly */
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instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
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check(instr_is_branch_to_addr(&instr, addr));
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check(instr == 0x43FF0000);
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}
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static void __init test_translate_branch(void)
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{
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unsigned long addr;
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unsigned int *p, *q;
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void *buf;
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buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
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check(buf);
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if (!buf)
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return;
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/* Simple case, branch to self moved a little */
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p = buf;
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addr = (unsigned long)p;
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patch_branch(p, addr, 0);
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check(instr_is_branch_to_addr(p, addr));
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q = p + 1;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(q, addr));
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/* Maximum negative case, move b . to addr + 32 MB */
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p = buf;
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addr = (unsigned long)p;
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patch_branch(p, addr, 0);
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q = buf + 0x2000000;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(p, addr));
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check(instr_is_branch_to_addr(q, addr));
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check(*q == 0x4a000000);
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/* Maximum positive case, move x to x - 32 MB + 4 */
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p = buf + 0x2000000;
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addr = (unsigned long)p;
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patch_branch(p, addr, 0);
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q = buf + 4;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(p, addr));
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check(instr_is_branch_to_addr(q, addr));
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check(*q == 0x49fffffc);
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/* Jump to x + 16 MB moved to x + 20 MB */
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p = buf;
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addr = 0x1000000 + (unsigned long)buf;
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patch_branch(p, addr, BRANCH_SET_LINK);
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q = buf + 0x1400000;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(p, addr));
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check(instr_is_branch_to_addr(q, addr));
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/* Jump to x + 16 MB moved to x - 16 MB + 4 */
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p = buf + 0x1000000;
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addr = 0x2000000 + (unsigned long)buf;
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patch_branch(p, addr, 0);
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q = buf + 4;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(p, addr));
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check(instr_is_branch_to_addr(q, addr));
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/* Conditional branch tests */
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/* Simple case, branch to self moved a little */
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p = buf;
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addr = (unsigned long)p;
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patch_instruction(p, create_cond_branch(p, addr, 0));
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check(instr_is_branch_to_addr(p, addr));
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q = p + 1;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(q, addr));
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/* Maximum negative case, move b . to addr + 32 KB */
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p = buf;
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addr = (unsigned long)p;
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patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
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q = buf + 0x8000;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(p, addr));
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check(instr_is_branch_to_addr(q, addr));
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check(*q == 0x43ff8000);
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/* Maximum positive case, move x to x - 32 KB + 4 */
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p = buf + 0x8000;
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addr = (unsigned long)p;
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patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
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q = buf + 4;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(p, addr));
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check(instr_is_branch_to_addr(q, addr));
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check(*q == 0x43ff7ffc);
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/* Jump to x + 12 KB moved to x + 20 KB */
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p = buf;
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addr = 0x3000 + (unsigned long)buf;
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patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
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q = buf + 0x5000;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(p, addr));
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check(instr_is_branch_to_addr(q, addr));
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/* Jump to x + 8 KB moved to x - 8 KB + 4 */
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p = buf + 0x2000;
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addr = 0x4000 + (unsigned long)buf;
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patch_instruction(p, create_cond_branch(p, addr, 0));
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q = buf + 4;
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patch_instruction(q, translate_branch(q, p));
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check(instr_is_branch_to_addr(p, addr));
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check(instr_is_branch_to_addr(q, addr));
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/* Free the buffer we were using */
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vfree(buf);
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}
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static int __init test_code_patching(void)
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{
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printk(KERN_DEBUG "Running code patching self-tests ...\n");
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test_branch_iform();
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test_branch_bform();
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test_create_function_call();
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test_translate_branch();
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return 0;
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}
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late_initcall(test_code_patching);
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#endif /* CONFIG_CODE_PATCHING_SELFTEST */
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