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 { 73 return arm_gen_branch_link(pc, addr); 74 } 75 76 static int ftrace_modify_code(unsigned long pc, unsigned long old, 77 unsigned long new, bool validate) 78 { 79 unsigned long replaced; 80 81 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) 82 old = __opcode_to_mem_thumb32(old); 83 else 84 old = __opcode_to_mem_arm(old); 85 86 if (validate) { 87 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE)) 88 return -EFAULT; 89 90 if (replaced != old) 91 return -EINVAL; 92 } 93 94 __patch_text((void *)pc, new); 95 96 return 0; 97 } 98 99 int ftrace_update_ftrace_func(ftrace_func_t func) 100 { 101 unsigned long pc; 102 unsigned long new; 103 int ret; 104 105 pc = (unsigned long)&ftrace_call; 106 new = ftrace_call_replace(pc, (unsigned long)func); 107 108 ret = ftrace_modify_code(pc, 0, new, false); 109 110 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS 111 if (!ret) { 112 pc = (unsigned long)&ftrace_regs_call; 113 new = ftrace_call_replace(pc, (unsigned long)func); 114 115 ret = ftrace_modify_code(pc, 0, new, false); 116 } 117 #endif 118 119 return ret; 120 } 121 122 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 123 { 124 unsigned long new, old; 125 unsigned long ip = rec->ip; 126 127 old = ftrace_nop_replace(rec); 128 129 new = ftrace_call_replace(ip, adjust_address(rec, addr)); 130 131 return ftrace_modify_code(rec->ip, old, new, true); 132 } 133 134 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS 135 136 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, 137 unsigned long addr) 138 { 139 unsigned long new, old; 140 unsigned long ip = rec->ip; 141 142 old = ftrace_call_replace(ip, adjust_address(rec, old_addr)); 143 144 new = ftrace_call_replace(ip, adjust_address(rec, addr)); 145 146 return ftrace_modify_code(rec->ip, old, new, true); 147 } 148 149 #endif 150 151 int ftrace_make_nop(struct module *mod, 152 struct dyn_ftrace *rec, unsigned long addr) 153 { 154 unsigned long ip = rec->ip; 155 unsigned long old; 156 unsigned long new; 157 int ret; 158 159 old = ftrace_call_replace(ip, adjust_address(rec, addr)); 160 new = ftrace_nop_replace(rec); 161 ret = ftrace_modify_code(ip, old, new, true); 162 163 return ret; 164 } 165 166 int __init ftrace_dyn_arch_init(void) 167 { 168 return 0; 169 } 170 #endif /* CONFIG_DYNAMIC_FTRACE */ 171 172 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 173 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 174 unsigned long frame_pointer) 175 { 176 unsigned long return_hooker = (unsigned long) &return_to_handler; 177 unsigned long old; 178 179 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 180 return; 181 182 old = *parent; 183 *parent = return_hooker; 184 185 if (function_graph_enter(old, self_addr, frame_pointer, NULL)) 186 *parent = old; 187 } 188 189 #ifdef CONFIG_DYNAMIC_FTRACE 190 extern unsigned long ftrace_graph_call; 191 extern unsigned long ftrace_graph_call_old; 192 extern void ftrace_graph_caller_old(void); 193 extern unsigned long ftrace_graph_regs_call; 194 extern void ftrace_graph_regs_caller(void); 195 196 static int __ftrace_modify_caller(unsigned long *callsite, 197 void (*func) (void), bool enable) 198 { 199 unsigned long caller_fn = (unsigned long) func; 200 unsigned long pc = (unsigned long) callsite; 201 unsigned long branch = arm_gen_branch(pc, caller_fn); 202 unsigned long nop = 0xe1a00000; /* mov r0, r0 */ 203 unsigned long old = enable ? nop : branch; 204 unsigned long new = enable ? branch : nop; 205 206 return ftrace_modify_code(pc, old, new, true); 207 } 208 209 static int ftrace_modify_graph_caller(bool enable) 210 { 211 int ret; 212 213 ret = __ftrace_modify_caller(&ftrace_graph_call, 214 ftrace_graph_caller, 215 enable); 216 217 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS 218 if (!ret) 219 ret = __ftrace_modify_caller(&ftrace_graph_regs_call, 220 ftrace_graph_regs_caller, 221 enable); 222 #endif 223 224 225 return ret; 226 } 227 228 int ftrace_enable_ftrace_graph_caller(void) 229 { 230 return ftrace_modify_graph_caller(true); 231 } 232 233 int ftrace_disable_ftrace_graph_caller(void) 234 { 235 return ftrace_modify_graph_caller(false); 236 } 237 #endif /* CONFIG_DYNAMIC_FTRACE */ 238 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 239