1 /* 2 * Dynamic function tracing support. 3 * 4 * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com> 5 * Copyright (C) 2010 Rabin Vincent <rabin@rab.in> 6 * 7 * For licencing details, see COPYING. 8 * 9 * Defines low-level handling of mcount calls when the kernel 10 * is compiled with the -pg flag. When using dynamic ftrace, the 11 * mcount call-sites get patched with NOP till they are enabled. 12 * All code mutation routines here are called under stop_machine(). 13 */ 14 15 #include <linux/ftrace.h> 16 #include <linux/uaccess.h> 17 #include <linux/module.h> 18 #include <linux/stop_machine.h> 19 20 #include <asm/cacheflush.h> 21 #include <asm/opcodes.h> 22 #include <asm/ftrace.h> 23 #include <asm/insn.h> 24 #include <asm/set_memory.h> 25 #include <asm/patch.h> 26 27 #ifdef CONFIG_THUMB2_KERNEL 28 #define NOP 0xf85deb04 /* pop.w {lr} */ 29 #else 30 #define NOP 0xe8bd4000 /* pop {lr} */ 31 #endif 32 33 #ifdef CONFIG_DYNAMIC_FTRACE 34 35 static int __ftrace_modify_code(void *data) 36 { 37 int *command = data; 38 39 ftrace_modify_all_code(*command); 40 41 return 0; 42 } 43 44 void arch_ftrace_update_code(int command) 45 { 46 stop_machine(__ftrace_modify_code, &command, NULL); 47 } 48 49 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) 50 { 51 return NOP; 52 } 53 54 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr) 55 { 56 return addr; 57 } 58 59 int ftrace_arch_code_modify_prepare(void) 60 { 61 return 0; 62 } 63 64 int ftrace_arch_code_modify_post_process(void) 65 { 66 /* Make sure any TLB misses during machine stop are cleared. */ 67 flush_tlb_all(); 68 return 0; 69 } 70 71 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr, 72 bool warn) 73 { 74 return arm_gen_branch_link(pc, addr, warn); 75 } 76 77 static int ftrace_modify_code(unsigned long pc, unsigned long old, 78 unsigned long new, bool validate) 79 { 80 unsigned long replaced; 81 82 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) 83 old = __opcode_to_mem_thumb32(old); 84 else 85 old = __opcode_to_mem_arm(old); 86 87 if (validate) { 88 if (copy_from_kernel_nofault(&replaced, (void *)pc, 89 MCOUNT_INSN_SIZE)) 90 return -EFAULT; 91 92 if (replaced != old) 93 return -EINVAL; 94 } 95 96 __patch_text((void *)pc, new); 97 98 return 0; 99 } 100 101 int ftrace_update_ftrace_func(ftrace_func_t func) 102 { 103 unsigned long pc; 104 unsigned long new; 105 int ret; 106 107 pc = (unsigned long)&ftrace_call; 108 new = ftrace_call_replace(pc, (unsigned long)func, true); 109 110 ret = ftrace_modify_code(pc, 0, new, false); 111 112 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS 113 if (!ret) { 114 pc = (unsigned long)&ftrace_regs_call; 115 new = ftrace_call_replace(pc, (unsigned long)func, true); 116 117 ret = ftrace_modify_code(pc, 0, new, false); 118 } 119 #endif 120 121 return ret; 122 } 123 124 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 125 { 126 unsigned long new, old; 127 unsigned long ip = rec->ip; 128 unsigned long aaddr = adjust_address(rec, addr); 129 struct module *mod = NULL; 130 131 #ifdef CONFIG_ARM_MODULE_PLTS 132 mod = rec->arch.mod; 133 #endif 134 135 old = ftrace_nop_replace(rec); 136 137 new = ftrace_call_replace(ip, aaddr, !mod); 138 #ifdef CONFIG_ARM_MODULE_PLTS 139 if (!new && mod) { 140 aaddr = get_module_plt(mod, ip, aaddr); 141 new = ftrace_call_replace(ip, aaddr, true); 142 } 143 #endif 144 145 return ftrace_modify_code(rec->ip, old, new, true); 146 } 147 148 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS 149 150 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, 151 unsigned long addr) 152 { 153 unsigned long new, old; 154 unsigned long ip = rec->ip; 155 156 old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true); 157 158 new = ftrace_call_replace(ip, adjust_address(rec, addr), true); 159 160 return ftrace_modify_code(rec->ip, old, new, true); 161 } 162 163 #endif 164 165 int ftrace_make_nop(struct module *mod, 166 struct dyn_ftrace *rec, unsigned long addr) 167 { 168 unsigned long aaddr = adjust_address(rec, addr); 169 unsigned long ip = rec->ip; 170 unsigned long old; 171 unsigned long new; 172 int ret; 173 174 #ifdef CONFIG_ARM_MODULE_PLTS 175 /* mod is only supplied during module loading */ 176 if (!mod) 177 mod = rec->arch.mod; 178 else 179 rec->arch.mod = mod; 180 #endif 181 182 old = ftrace_call_replace(ip, aaddr, 183 !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod); 184 #ifdef CONFIG_ARM_MODULE_PLTS 185 if (!old && mod) { 186 aaddr = get_module_plt(mod, ip, aaddr); 187 old = ftrace_call_replace(ip, aaddr, true); 188 } 189 #endif 190 191 new = ftrace_nop_replace(rec); 192 ret = ftrace_modify_code(ip, old, new, true); 193 194 return ret; 195 } 196 #endif /* CONFIG_DYNAMIC_FTRACE */ 197 198 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 199 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 200 unsigned long frame_pointer) 201 { 202 unsigned long return_hooker = (unsigned long) &return_to_handler; 203 unsigned long old; 204 205 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 206 return; 207 208 old = *parent; 209 *parent = return_hooker; 210 211 if (function_graph_enter(old, self_addr, frame_pointer, NULL)) 212 *parent = old; 213 } 214 215 #ifdef CONFIG_DYNAMIC_FTRACE 216 extern unsigned long ftrace_graph_call; 217 extern unsigned long ftrace_graph_call_old; 218 extern void ftrace_graph_caller_old(void); 219 extern unsigned long ftrace_graph_regs_call; 220 extern void ftrace_graph_regs_caller(void); 221 222 static int __ftrace_modify_caller(unsigned long *callsite, 223 void (*func) (void), bool enable) 224 { 225 unsigned long caller_fn = (unsigned long) func; 226 unsigned long pc = (unsigned long) callsite; 227 unsigned long branch = arm_gen_branch(pc, caller_fn); 228 unsigned long nop = 0xe1a00000; /* mov r0, r0 */ 229 unsigned long old = enable ? nop : branch; 230 unsigned long new = enable ? branch : nop; 231 232 return ftrace_modify_code(pc, old, new, true); 233 } 234 235 static int ftrace_modify_graph_caller(bool enable) 236 { 237 int ret; 238 239 ret = __ftrace_modify_caller(&ftrace_graph_call, 240 ftrace_graph_caller, 241 enable); 242 243 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS 244 if (!ret) 245 ret = __ftrace_modify_caller(&ftrace_graph_regs_call, 246 ftrace_graph_regs_caller, 247 enable); 248 #endif 249 250 251 return ret; 252 } 253 254 int ftrace_enable_ftrace_graph_caller(void) 255 { 256 return ftrace_modify_graph_caller(true); 257 } 258 259 int ftrace_disable_ftrace_graph_caller(void) 260 { 261 return ftrace_modify_graph_caller(false); 262 } 263 #endif /* CONFIG_DYNAMIC_FTRACE */ 264 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 265