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

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  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 int raw_patch_instruction(unsigned int *addr, unsigned int instr);
 35 
 36 int instr_is_relative_branch(unsigned int instr);
 37 int instr_is_relative_link_branch(unsigned int instr);
 38 int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr);
 39 unsigned long branch_target(const unsigned int *instr);
 40 unsigned int translate_branch(const unsigned int *dest,
 41                               const unsigned int *src);
 42 extern bool is_conditional_branch(unsigned int instr);
 43 #ifdef CONFIG_PPC_BOOK3E_64
 44 void __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 
 56 static 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 
 95 static 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  */
111 static 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 

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