LXR linux/arch/powerpc/include/asm/code-patching.h

   1#ifndef _ASM_POWERPC_CODE_PATCHING_H
   2#define _ASM_POWERPC_CODE_PATCHING_H
   3
   4/*
   5 * Copyright 2008, Michael Ellerman, IBM Corporation.
   6 *
   7 * This program is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public License
   9 * as published by the Free Software Foundation; either version
  10 * 2 of the License, or (at your option) any later version.
  11 */
  12
  13#include <asm/types.h>
  14#include <asm/ppc-opcode.h>
  15#include <linux/string.h>
  16#include <linux/kallsyms.h>
  17
  18/* Flags for create_branch:
  19 * "b"   == create_branch(addr, target, 0);
  20 * "ba"  == create_branch(addr, target, BRANCH_ABSOLUTE);
  21 * "bl"  == create_branch(addr, target, BRANCH_SET_LINK);
  22 * "bla" == create_branch(addr, target, BRANCH_ABSOLUTE | BRANCH_SET_LINK);
  23 */
  24#define BRANCH_SET_LINK 0x1
  25#define BRANCH_ABSOLUTE 0x2
  26
  27bool is_offset_in_branch_range(long offset);
  28unsigned int create_branch(const unsigned int *addr,
  29                           unsigned long target, int flags);
  30unsigned int create_cond_branch(const unsigned int *addr,
  31                                unsigned long target, int flags);
  32int patch_branch(unsigned int *addr, unsigned long target, int flags);
  33int patch_instruction(unsigned int *addr, unsigned int instr);
  34int raw_patch_instruction(unsigned int *addr, unsigned int instr);
  35
  36int instr_is_relative_branch(unsigned int instr);
  37int instr_is_relative_link_branch(unsigned int instr);
  38int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr);
  39unsigned long branch_target(const unsigned int *instr);
  40unsigned int translate_branch(const unsigned int *dest,
  41                              const unsigned int *src);
  42extern bool is_conditional_branch(unsigned int instr);
  43#ifdef CONFIG_PPC_BOOK3E_64
  44void __patch_exception(int exc, unsigned long addr);
  45#define patch_exception(exc, name) do { \
  46        extern unsigned int name; \
  47        __patch_exception((exc), (unsigned long)&name); \
  48} while (0)
  49#endif
  50
  51#define OP_RT_RA_MASK   0xffff0000UL
  52#define LIS_R2          0x3c020000UL
  53#define ADDIS_R2_R12    0x3c4c0000UL
  54#define ADDI_R2_R2      0x38420000UL
  55
  56static inline unsigned long ppc_function_entry(void *func)
  57{
  58#ifdef PPC64_ELF_ABI_v2
  59        u32 *insn = func;
  60
  61        /*
  62         * A PPC64 ABIv2 function may have a local and a global entry
  63         * point. We need to use the local entry point when patching
  64         * functions, so identify and step over the global entry point
  65         * sequence.
  66         *
  67         * The global entry point sequence is always of the form:
  68         *
  69         * addis r2,r12,XXXX
  70         * addi  r2,r2,XXXX
  71         *
  72         * A linker optimisation may convert the addis to lis:
  73         *
  74         * lis   r2,XXXX
  75         * addi  r2,r2,XXXX
  76         */
  77        if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) ||
  78             ((*insn & OP_RT_RA_MASK) == LIS_R2)) &&
  79            ((*(insn+1) & OP_RT_RA_MASK) == ADDI_R2_R2))
  80                return (unsigned long)(insn + 2);
  81        else
  82                return (unsigned long)func;
  83#elif defined(PPC64_ELF_ABI_v1)
  84        /*
  85         * On PPC64 ABIv1 the function pointer actually points to the
  86         * function's descriptor. The first entry in the descriptor is the
  87         * address of the function text.
  88         */
  89        return ((func_descr_t *)func)->entry;
  90#else
  91        return (unsigned long)func;
  92#endif
  93}
  94
  95static inline unsigned long ppc_global_function_entry(void *func)
  96{
  97#ifdef PPC64_ELF_ABI_v2
  98        /* PPC64 ABIv2 the global entry point is at the address */
  99        return (unsigned long)func;
 100#else
 101        /* All other cases there is no change vs ppc_function_entry() */
 102        return ppc_function_entry(func);
 103#endif
 104}
 105
 106/*
 107 * Wrapper around kallsyms_lookup() to return function entry address:
 108 * - For ABIv1, we lookup the dot variant.
 109 * - For ABIv2, we return the local entry point.
 110 */
 111static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
 112{
 113        unsigned long addr;
 114#ifdef PPC64_ELF_ABI_v1
 115        /* check for dot variant */
 116        char dot_name[1 + KSYM_NAME_LEN];
 117        bool dot_appended = false;
 118
 119        if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
 120                return 0;
 121
 122        if (name[0] != '.') {
 123                dot_name[0] = '.';
 124                dot_name[1] = '\0';
 125                strlcat(dot_name, name, sizeof(dot_name));
 126                dot_appended = true;
 127        } else {
 128                dot_name[0] = '\0';
 129                strlcat(dot_name, name, sizeof(dot_name));
 130        }
 131        addr = kallsyms_lookup_name(dot_name);
 132        if (!addr && dot_appended)
 133                /* Let's try the original non-dot symbol lookup */
 134                addr = kallsyms_lookup_name(name);
 135#elif defined(PPC64_ELF_ABI_v2)
 136        addr = kallsyms_lookup_name(name);
 137        if (addr)
 138                addr = ppc_function_entry((void *)addr);
 139#else
 140        addr = kallsyms_lookup_name(name);
 141#endif
 142        return addr;
 143}
 144
 145#ifdef CONFIG_PPC64
 146/*
 147 * Some instruction encodings commonly used in dynamic ftracing
 148 * and function live patching.
 149 */
 150
 151/* This must match the definition of STK_GOT in <asm/ppc_asm.h> */
 152#ifdef PPC64_ELF_ABI_v2
 153#define R2_STACK_OFFSET         24
 154#else
 155#define R2_STACK_OFFSET         40
 156#endif
 157
 158#define PPC_INST_LD_TOC         (PPC_INST_LD  | ___PPC_RT(__REG_R2) | \
 159                                 ___PPC_RA(__REG_R1) | R2_STACK_OFFSET)
 160
 161/* usually preceded by a mflr r0 */
 162#define PPC_INST_STD_LR         (PPC_INST_STD | ___PPC_RS(__REG_R0) | \
 163                                 ___PPC_RA(__REG_R1) | PPC_LR_STKOFF)
 164#endif /* CONFIG_PPC64 */
 165
 166#endif /* _ASM_POWERPC_CODE_PATCHING_H */
 167