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