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 18 #include <asm/cacheflush.h> 19 #include <asm/opcodes.h> 20 #include <asm/ftrace.h> 21 22 #include "insn.h" 23 24 #ifdef CONFIG_THUMB2_KERNEL 25 #define NOP 0xf85deb04 /* pop.w {lr} */ 26 #else 27 #define NOP 0xe8bd4000 /* pop {lr} */ 28 #endif 29 30 #ifdef CONFIG_DYNAMIC_FTRACE 31 #ifdef CONFIG_OLD_MCOUNT 32 #define OLD_MCOUNT_ADDR ((unsigned long) mcount) 33 #define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) 34 35 #define OLD_NOP 0xe1a00000 /* mov r0, r0 */ 36 37 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) 38 { 39 return rec->arch.old_mcount ? OLD_NOP : NOP; 40 } 41 42 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr) 43 { 44 if (!rec->arch.old_mcount) 45 return addr; 46 47 if (addr == MCOUNT_ADDR) 48 addr = OLD_MCOUNT_ADDR; 49 else if (addr == FTRACE_ADDR) 50 addr = OLD_FTRACE_ADDR; 51 52 return addr; 53 } 54 #else 55 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) 56 { 57 return NOP; 58 } 59 60 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr) 61 { 62 return addr; 63 } 64 #endif 65 66 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) 67 { 68 return arm_gen_branch_link(pc, addr); 69 } 70 71 static int ftrace_modify_code(unsigned long pc, unsigned long old, 72 unsigned long new, bool validate) 73 { 74 unsigned long replaced; 75 76 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) { 77 old = __opcode_to_mem_thumb32(old); 78 new = __opcode_to_mem_thumb32(new); 79 } else { 80 old = __opcode_to_mem_arm(old); 81 new = __opcode_to_mem_arm(new); 82 } 83 84 if (validate) { 85 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE)) 86 return -EFAULT; 87 88 if (replaced != old) 89 return -EINVAL; 90 } 91 92 if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE)) 93 return -EPERM; 94 95 flush_icache_range(pc, pc + MCOUNT_INSN_SIZE); 96 97 return 0; 98 } 99 100 int ftrace_update_ftrace_func(ftrace_func_t func) 101 { 102 unsigned long pc; 103 unsigned long new; 104 int ret; 105 106 pc = (unsigned long)&ftrace_call; 107 new = ftrace_call_replace(pc, (unsigned long)func); 108 109 ret = ftrace_modify_code(pc, 0, new, false); 110 111 #ifdef CONFIG_OLD_MCOUNT 112 if (!ret) { 113 pc = (unsigned long)&ftrace_call_old; 114 new = ftrace_call_replace(pc, (unsigned long)func); 115 116 ret = ftrace_modify_code(pc, 0, new, false); 117 } 118 #endif 119 120 return ret; 121 } 122 123 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 124 { 125 unsigned long new, old; 126 unsigned long ip = rec->ip; 127 128 old = ftrace_nop_replace(rec); 129 new = ftrace_call_replace(ip, adjust_address(rec, addr)); 130 131 return ftrace_modify_code(rec->ip, old, new, true); 132 } 133 134 int ftrace_make_nop(struct module *mod, 135 struct dyn_ftrace *rec, unsigned long addr) 136 { 137 unsigned long ip = rec->ip; 138 unsigned long old; 139 unsigned long new; 140 int ret; 141 142 old = ftrace_call_replace(ip, adjust_address(rec, addr)); 143 new = ftrace_nop_replace(rec); 144 ret = ftrace_modify_code(ip, old, new, true); 145 146 #ifdef CONFIG_OLD_MCOUNT 147 if (ret == -EINVAL && addr == MCOUNT_ADDR) { 148 rec->arch.old_mcount = true; 149 150 old = ftrace_call_replace(ip, adjust_address(rec, addr)); 151 new = ftrace_nop_replace(rec); 152 ret = ftrace_modify_code(ip, old, new, true); 153 } 154 #endif 155 156 return ret; 157 } 158 159 int __init ftrace_dyn_arch_init(void) 160 { 161 return 0; 162 } 163 #endif /* CONFIG_DYNAMIC_FTRACE */ 164 165 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 166 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 167 unsigned long frame_pointer) 168 { 169 unsigned long return_hooker = (unsigned long) &return_to_handler; 170 struct ftrace_graph_ent trace; 171 unsigned long old; 172 int err; 173 174 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 175 return; 176 177 old = *parent; 178 *parent = return_hooker; 179 180 trace.func = self_addr; 181 trace.depth = current->curr_ret_stack + 1; 182 183 /* Only trace if the calling function expects to */ 184 if (!ftrace_graph_entry(&trace)) { 185 *parent = old; 186 return; 187 } 188 189 err = ftrace_push_return_trace(old, self_addr, &trace.depth, 190 frame_pointer); 191 if (err == -EBUSY) { 192 *parent = old; 193 return; 194 } 195 } 196 197 #ifdef CONFIG_DYNAMIC_FTRACE 198 extern unsigned long ftrace_graph_call; 199 extern unsigned long ftrace_graph_call_old; 200 extern void ftrace_graph_caller_old(void); 201 202 static int __ftrace_modify_caller(unsigned long *callsite, 203 void (*func) (void), bool enable) 204 { 205 unsigned long caller_fn = (unsigned long) func; 206 unsigned long pc = (unsigned long) callsite; 207 unsigned long branch = arm_gen_branch(pc, caller_fn); 208 unsigned long nop = 0xe1a00000; /* mov r0, r0 */ 209 unsigned long old = enable ? nop : branch; 210 unsigned long new = enable ? branch : nop; 211 212 return ftrace_modify_code(pc, old, new, true); 213 } 214 215 static int ftrace_modify_graph_caller(bool enable) 216 { 217 int ret; 218 219 ret = __ftrace_modify_caller(&ftrace_graph_call, 220 ftrace_graph_caller, 221 enable); 222 223 #ifdef CONFIG_OLD_MCOUNT 224 if (!ret) 225 ret = __ftrace_modify_caller(&ftrace_graph_call_old, 226 ftrace_graph_caller_old, 227 enable); 228 #endif 229 230 return ret; 231 } 232 233 int ftrace_enable_ftrace_graph_caller(void) 234 { 235 return ftrace_modify_graph_caller(true); 236 } 237 238 int ftrace_disable_ftrace_graph_caller(void) 239 { 240 return ftrace_modify_graph_caller(false); 241 } 242 #endif /* CONFIG_DYNAMIC_FTRACE */ 243 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 244