1 /* 2 * Code for replacing ftrace calls with jumps. 3 * 4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> 5 * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China 6 * Author: Wu Zhangjin <wuzhangjin@gmail.com> 7 * 8 * Thanks goes to Steven Rostedt for writing the original x86 version. 9 */ 10 11 #include <linux/uaccess.h> 12 #include <linux/init.h> 13 #include <linux/ftrace.h> 14 15 #include <asm/asm.h> 16 #include <asm/asm-offsets.h> 17 #include <asm/cacheflush.h> 18 #include <asm/uasm.h> 19 20 #include <asm-generic/sections.h> 21 22 #ifdef CONFIG_DYNAMIC_FTRACE 23 24 #define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */ 25 #define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */ 26 27 #define INSN_NOP 0x00000000 /* nop */ 28 #define INSN_JAL(addr) \ 29 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK))) 30 31 static unsigned int insn_jal_ftrace_caller __read_mostly; 32 static unsigned int insn_lui_v1_hi16_mcount __read_mostly; 33 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly; 34 35 static inline void ftrace_dyn_arch_init_insns(void) 36 { 37 u32 *buf; 38 unsigned int v1; 39 40 /* lui v1, hi16_mcount */ 41 v1 = 3; 42 buf = (u32 *)&insn_lui_v1_hi16_mcount; 43 UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR); 44 45 /* jal (ftrace_caller + 8), jump over the first two instruction */ 46 buf = (u32 *)&insn_jal_ftrace_caller; 47 uasm_i_jal(&buf, (FTRACE_ADDR + 8)); 48 49 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 50 /* j ftrace_graph_caller */ 51 buf = (u32 *)&insn_j_ftrace_graph_caller; 52 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller); 53 #endif 54 } 55 56 /* 57 * Check if the address is in kernel space 58 * 59 * Clone core_kernel_text() from kernel/extable.c, but doesn't call 60 * init_kernel_text() for Ftrace doesn't trace functions in init sections. 61 */ 62 static inline int in_kernel_space(unsigned long ip) 63 { 64 if (ip >= (unsigned long)_stext && 65 ip <= (unsigned long)_etext) 66 return 1; 67 return 0; 68 } 69 70 static int ftrace_modify_code(unsigned long ip, unsigned int new_code) 71 { 72 int faulted; 73 74 /* *(unsigned int *)ip = new_code; */ 75 safe_store_code(new_code, ip, faulted); 76 77 if (unlikely(faulted)) 78 return -EFAULT; 79 80 flush_icache_range(ip, ip + 8); 81 82 return 0; 83 } 84 85 /* 86 * The details about the calling site of mcount on MIPS 87 * 88 * 1. For kernel: 89 * 90 * move at, ra 91 * jal _mcount --> nop 92 * 93 * 2. For modules: 94 * 95 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT 96 * 97 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005) 98 * addiu v1, v1, low_16bit_of_mcount 99 * move at, ra 100 * move $12, ra_address 101 * jalr v1 102 * sub sp, sp, 8 103 * 1: offset = 5 instructions 104 * 2.2 For the Other situations 105 * 106 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004) 107 * addiu v1, v1, low_16bit_of_mcount 108 * move at, ra 109 * jalr v1 110 * nop | move $12, ra_address | sub sp, sp, 8 111 * 1: offset = 4 instructions 112 */ 113 114 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT) 115 #define MCOUNT_OFFSET_INSNS 5 116 #else 117 #define MCOUNT_OFFSET_INSNS 4 118 #endif 119 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS) 120 121 int ftrace_make_nop(struct module *mod, 122 struct dyn_ftrace *rec, unsigned long addr) 123 { 124 unsigned int new; 125 unsigned long ip = rec->ip; 126 127 /* 128 * If ip is in kernel space, no long call, otherwise, long call is 129 * needed. 130 */ 131 new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F; 132 133 return ftrace_modify_code(ip, new); 134 } 135 136 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 137 { 138 unsigned int new; 139 unsigned long ip = rec->ip; 140 141 new = in_kernel_space(ip) ? insn_jal_ftrace_caller : 142 insn_lui_v1_hi16_mcount; 143 144 return ftrace_modify_code(ip, new); 145 } 146 147 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call)) 148 149 int ftrace_update_ftrace_func(ftrace_func_t func) 150 { 151 unsigned int new; 152 153 new = INSN_JAL((unsigned long)func); 154 155 return ftrace_modify_code(FTRACE_CALL_IP, new); 156 } 157 158 int __init ftrace_dyn_arch_init(void *data) 159 { 160 /* Encode the instructions when booting */ 161 ftrace_dyn_arch_init_insns(); 162 163 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */ 164 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP); 165 166 /* The return code is retured via data */ 167 *(unsigned long *)data = 0; 168 169 return 0; 170 } 171 #endif /* CONFIG_DYNAMIC_FTRACE */ 172 173 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 174 175 #ifdef CONFIG_DYNAMIC_FTRACE 176 177 extern void ftrace_graph_call(void); 178 #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call)) 179 180 int ftrace_enable_ftrace_graph_caller(void) 181 { 182 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, 183 insn_j_ftrace_graph_caller); 184 } 185 186 int ftrace_disable_ftrace_graph_caller(void) 187 { 188 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP); 189 } 190 191 #endif /* CONFIG_DYNAMIC_FTRACE */ 192 193 #ifndef KBUILD_MCOUNT_RA_ADDRESS 194 195 #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */ 196 #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */ 197 #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */ 198 199 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long 200 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp) 201 { 202 unsigned long sp, ip, tmp; 203 unsigned int code; 204 int faulted; 205 206 /* 207 * For module, move the ip from the return address after the 208 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for 209 * kernel, move after the instruction "move ra, at"(offset is 16) 210 */ 211 ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24); 212 213 /* 214 * search the text until finding the non-store instruction or "s{d,w} 215 * ra, offset(sp)" instruction 216 */ 217 do { 218 /* get the code at "ip": code = *(unsigned int *)ip; */ 219 safe_load_code(code, ip, faulted); 220 221 if (unlikely(faulted)) 222 return 0; 223 /* 224 * If we hit the non-store instruction before finding where the 225 * ra is stored, then this is a leaf function and it does not 226 * store the ra on the stack 227 */ 228 if ((code & S_R_SP) != S_R_SP) 229 return parent_ra_addr; 230 231 /* Move to the next instruction */ 232 ip -= 4; 233 } while ((code & S_RA_SP) != S_RA_SP); 234 235 sp = fp + (code & OFFSET_MASK); 236 237 /* tmp = *(unsigned long *)sp; */ 238 safe_load_stack(tmp, sp, faulted); 239 if (unlikely(faulted)) 240 return 0; 241 242 if (tmp == old_parent_ra) 243 return sp; 244 return 0; 245 } 246 247 #endif /* !KBUILD_MCOUNT_RA_ADDRESS */ 248 249 /* 250 * Hook the return address and push it in the stack of return addrs 251 * in current thread info. 252 */ 253 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, 254 unsigned long fp) 255 { 256 unsigned long old_parent_ra; 257 struct ftrace_graph_ent trace; 258 unsigned long return_hooker = (unsigned long) 259 &return_to_handler; 260 int faulted, insns; 261 262 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 263 return; 264 265 /* 266 * "parent_ra_addr" is the stack address saved the return address of 267 * the caller of _mcount. 268 * 269 * if the gcc < 4.5, a leaf function does not save the return address 270 * in the stack address, so, we "emulate" one in _mcount's stack space, 271 * and hijack it directly, but for a non-leaf function, it save the 272 * return address to the its own stack space, we can not hijack it 273 * directly, but need to find the real stack address, 274 * ftrace_get_parent_addr() does it! 275 * 276 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a 277 * non-leaf function, the location of the return address will be saved 278 * to $12 for us, and for a leaf function, only put a zero into $12. we 279 * do it in ftrace_graph_caller of mcount.S. 280 */ 281 282 /* old_parent_ra = *parent_ra_addr; */ 283 safe_load_stack(old_parent_ra, parent_ra_addr, faulted); 284 if (unlikely(faulted)) 285 goto out; 286 #ifndef KBUILD_MCOUNT_RA_ADDRESS 287 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra, 288 old_parent_ra, (unsigned long)parent_ra_addr, fp); 289 /* 290 * If fails when getting the stack address of the non-leaf function's 291 * ra, stop function graph tracer and return 292 */ 293 if (parent_ra_addr == 0) 294 goto out; 295 #endif 296 /* *parent_ra_addr = return_hooker; */ 297 safe_store_stack(return_hooker, parent_ra_addr, faulted); 298 if (unlikely(faulted)) 299 goto out; 300 301 if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp) 302 == -EBUSY) { 303 *parent_ra_addr = old_parent_ra; 304 return; 305 } 306 307 /* 308 * Get the recorded ip of the current mcount calling site in the 309 * __mcount_loc section, which will be used to filter the function 310 * entries configured through the tracing/set_graph_function interface. 311 */ 312 313 insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1; 314 trace.func = self_ra - (MCOUNT_INSN_SIZE * insns); 315 316 /* Only trace if the calling function expects to */ 317 if (!ftrace_graph_entry(&trace)) { 318 current->curr_ret_stack--; 319 *parent_ra_addr = old_parent_ra; 320 } 321 return; 322 out: 323 ftrace_graph_stop(); 324 WARN_ON(1); 325 } 326 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 327