root/arch/powerpc/include/asm/code-patching.h

INCLUDED FROM

DEFINITIONS

1. patch_site_addr
2. patch_instruction_site
3. patch_branch_site
4. modify_instruction
5. modify_instruction_site
6. ppc_function_entry
7. ppc_global_function_entry
8. ppc_kallsyms_lookup_name

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 #ifndef _ASM_POWERPC_CODE_PATCHING_H
   3 #define _ASM_POWERPC_CODE_PATCHING_H
   4 
   5 /*
   6  * Copyright 2008, Michael Ellerman, IBM Corporation.
   7  */
   8 
   9 #include <asm/types.h>
  10 #include <asm/ppc-opcode.h>
  11 #include <linux/string.h>
  12 #include <linux/kallsyms.h>
  13 #include <asm/asm-compat.h>
  14 
  15 /* Flags for create_branch:
  16  * "b"   == create_branch(addr, target, 0);
  17  * "ba"  == create_branch(addr, target, BRANCH_ABSOLUTE);
  18  * "bl"  == create_branch(addr, target, BRANCH_SET_LINK);
  19  * "bla" == create_branch(addr, target, BRANCH_ABSOLUTE | BRANCH_SET_LINK);
  20  */
  21 #define BRANCH_SET_LINK 0x1
  22 #define BRANCH_ABSOLUTE 0x2
  23 
  24 bool is_offset_in_branch_range(long offset);
  25 unsigned int create_branch(const unsigned int *addr,
  26                            unsigned long target, int flags);
  27 unsigned int create_cond_branch(const unsigned int *addr,
  28                                 unsigned long target, int flags);
  29 int patch_branch(unsigned int *addr, unsigned long target, int flags);
  30 int patch_instruction(unsigned int *addr, unsigned int instr);
  31 int raw_patch_instruction(unsigned int *addr, unsigned int instr);
  32 
  33 static inline unsigned long patch_site_addr(s32 *site)
  34 {
  35         return (unsigned long)site + *site;
  36 }
  37 
  38 static inline int patch_instruction_site(s32 *site, unsigned int instr)
  39 {
  40         return patch_instruction((unsigned int *)patch_site_addr(site), instr);
  41 }
  42 
  43 static inline int patch_branch_site(s32 *site, unsigned long target, int flags)
  44 {
  45         return patch_branch((unsigned int *)patch_site_addr(site), target, flags);
  46 }
  47 
  48 static inline int modify_instruction(unsigned int *addr, unsigned int clr,
  49                                      unsigned int set)
  50 {
  51         return patch_instruction(addr, (*addr & ~clr) | set);
  52 }
  53 
  54 static inline int modify_instruction_site(s32 *site, unsigned int clr, unsigned int set)
  55 {
  56         return modify_instruction((unsigned int *)patch_site_addr(site), clr, set);
  57 }
  58 
  59 int instr_is_relative_branch(unsigned int instr);
  60 int instr_is_relative_link_branch(unsigned int instr);
  61 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr);
  62 unsigned long branch_target(const unsigned int *instr);
  63 unsigned int translate_branch(const unsigned int *dest,
  64                               const unsigned int *src);
  65 extern bool is_conditional_branch(unsigned int instr);
  66 #ifdef CONFIG_PPC_BOOK3E_64
  67 void __patch_exception(int exc, unsigned long addr);
  68 #define patch_exception(exc, name) do { \
  69         extern unsigned int name; \
  70         __patch_exception((exc), (unsigned long)&name); \
  71 } while (0)
  72 #endif
  73 
  74 #define OP_RT_RA_MASK   0xffff0000UL
  75 #define LIS_R2          0x3c020000UL
  76 #define ADDIS_R2_R12    0x3c4c0000UL
  77 #define ADDI_R2_R2      0x38420000UL
  78 
  79 static inline unsigned long ppc_function_entry(void *func)
  80 {
  81 #ifdef PPC64_ELF_ABI_v2
  82         u32 *insn = func;
  83 
  84         /*
  85          * A PPC64 ABIv2 function may have a local and a global entry
  86          * point. We need to use the local entry point when patching
  87          * functions, so identify and step over the global entry point
  88          * sequence.
  89          *
  90          * The global entry point sequence is always of the form:
  91          *
  92          * addis r2,r12,XXXX
  93          * addi  r2,r2,XXXX
  94          *
  95          * A linker optimisation may convert the addis to lis:
  96          *
  97          * lis   r2,XXXX
  98          * addi  r2,r2,XXXX
  99          */
 100         if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) ||
 101              ((*insn & OP_RT_RA_MASK) == LIS_R2)) &&
 102             ((*(insn+1) & OP_RT_RA_MASK) == ADDI_R2_R2))
 103                 return (unsigned long)(insn + 2);
 104         else
 105                 return (unsigned long)func;
 106 #elif defined(PPC64_ELF_ABI_v1)
 107         /*
 108          * On PPC64 ABIv1 the function pointer actually points to the
 109          * function's descriptor. The first entry in the descriptor is the
 110          * address of the function text.
 111          */
 112         return ((func_descr_t *)func)->entry;
 113 #else
 114         return (unsigned long)func;
 115 #endif
 116 }
 117 
 118 static inline unsigned long ppc_global_function_entry(void *func)
 119 {
 120 #ifdef PPC64_ELF_ABI_v2
 121         /* PPC64 ABIv2 the global entry point is at the address */
 122         return (unsigned long)func;
 123 #else
 124         /* All other cases there is no change vs ppc_function_entry() */
 125         return ppc_function_entry(func);
 126 #endif
 127 }
 128 
 129 /*
 130  * Wrapper around kallsyms_lookup() to return function entry address:
 131  * - For ABIv1, we lookup the dot variant.
 132  * - For ABIv2, we return the local entry point.
 133  */
 134 static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
 135 {
 136         unsigned long addr;
 137 #ifdef PPC64_ELF_ABI_v1
 138         /* check for dot variant */
 139         char dot_name[1 + KSYM_NAME_LEN];
 140         bool dot_appended = false;
 141 
 142         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
 143                 return 0;
 144 
 145         if (name[0] != '.') {
 146                 dot_name[0] = '.';
 147                 dot_name[1] = '\0';
 148                 strlcat(dot_name, name, sizeof(dot_name));
 149                 dot_appended = true;
 150         } else {
 151                 dot_name[0] = '\0';
 152                 strlcat(dot_name, name, sizeof(dot_name));
 153         }
 154         addr = kallsyms_lookup_name(dot_name);
 155         if (!addr && dot_appended)
 156                 /* Let's try the original non-dot symbol lookup */
 157                 addr = kallsyms_lookup_name(name);
 158 #elif defined(PPC64_ELF_ABI_v2)
 159         addr = kallsyms_lookup_name(name);
 160         if (addr)
 161                 addr = ppc_function_entry((void *)addr);
 162 #else
 163         addr = kallsyms_lookup_name(name);
 164 #endif
 165         return addr;
 166 }
 167 
 168 #ifdef CONFIG_PPC64
 169 /*
 170  * Some instruction encodings commonly used in dynamic ftracing
 171  * and function live patching.
 172  */
 173 
 174 /* This must match the definition of STK_GOT in <asm/ppc_asm.h> */
 175 #ifdef PPC64_ELF_ABI_v2
 176 #define R2_STACK_OFFSET         24
 177 #else
 178 #define R2_STACK_OFFSET         40
 179 #endif
 180 
 181 #define PPC_INST_LD_TOC         (PPC_INST_LD  | ___PPC_RT(__REG_R2) | \
 182                                  ___PPC_RA(__REG_R1) | R2_STACK_OFFSET)
 183 
 184 /* usually preceded by a mflr r0 */
 185 #define PPC_INST_STD_LR         (PPC_INST_STD | ___PPC_RS(__REG_R0) | \
 186                                  ___PPC_RA(__REG_R1) | PPC_LR_STKOFF)
 187 #endif /* CONFIG_PPC64 */
 188 
 189 #endif /* _ASM_POWERPC_CODE_PATCHING_H */