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 #include <linux/syscalls.h> 15 16 #include <asm/asm.h> 17 #include <asm/asm-offsets.h> 18 #include <asm/cacheflush.h> 19 #include <asm/syscall.h> 20 #include <asm/uasm.h> 21 #include <asm/unistd.h> 22 23 #include <asm-generic/sections.h> 24 25 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT) 26 #define MCOUNT_OFFSET_INSNS 5 27 #else 28 #define MCOUNT_OFFSET_INSNS 4 29 #endif 30 31 #ifdef CONFIG_DYNAMIC_FTRACE 32 33 /* Arch override because MIPS doesn't need to run this from stop_machine() */ 34 void arch_ftrace_update_code(int command) 35 { 36 ftrace_modify_all_code(command); 37 } 38 39 #endif 40 41 /* 42 * Check if the address is in kernel space 43 * 44 * Clone core_kernel_text() from kernel/extable.c, but doesn't call 45 * init_kernel_text() for Ftrace doesn't trace functions in init sections. 46 */ 47 static inline int in_kernel_space(unsigned long ip) 48 { 49 if (ip >= (unsigned long)_stext && 50 ip <= (unsigned long)_etext) 51 return 1; 52 return 0; 53 } 54 55 #ifdef CONFIG_DYNAMIC_FTRACE 56 57 #define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */ 58 #define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */ 59 #define JUMP_RANGE_MASK ((1UL << 28) - 1) 60 61 #define INSN_NOP 0x00000000 /* nop */ 62 #define INSN_JAL(addr) \ 63 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK))) 64 65 static unsigned int insn_jal_ftrace_caller __read_mostly; 66 static unsigned int insn_la_mcount[2] __read_mostly; 67 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly; 68 69 static inline void ftrace_dyn_arch_init_insns(void) 70 { 71 u32 *buf; 72 unsigned int v1; 73 74 /* la v1, _mcount */ 75 v1 = 3; 76 buf = (u32 *)&insn_la_mcount[0]; 77 UASM_i_LA(&buf, v1, MCOUNT_ADDR); 78 79 /* jal (ftrace_caller + 8), jump over the first two instruction */ 80 buf = (u32 *)&insn_jal_ftrace_caller; 81 uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK); 82 83 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 84 /* j ftrace_graph_caller */ 85 buf = (u32 *)&insn_j_ftrace_graph_caller; 86 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK); 87 #endif 88 } 89 90 static int ftrace_modify_code(unsigned long ip, unsigned int new_code) 91 { 92 int faulted; 93 mm_segment_t old_fs; 94 95 /* *(unsigned int *)ip = new_code; */ 96 safe_store_code(new_code, ip, faulted); 97 98 if (unlikely(faulted)) 99 return -EFAULT; 100 101 old_fs = get_fs(); 102 set_fs(get_ds()); 103 flush_icache_range(ip, ip + 8); 104 set_fs(old_fs); 105 106 return 0; 107 } 108 109 #ifndef CONFIG_64BIT 110 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1, 111 unsigned int new_code2) 112 { 113 int faulted; 114 mm_segment_t old_fs; 115 116 safe_store_code(new_code1, ip, faulted); 117 if (unlikely(faulted)) 118 return -EFAULT; 119 120 ip += 4; 121 safe_store_code(new_code2, ip, faulted); 122 if (unlikely(faulted)) 123 return -EFAULT; 124 125 ip -= 4; 126 old_fs = get_fs(); 127 set_fs(get_ds()); 128 flush_icache_range(ip, ip + 8); 129 set_fs(old_fs); 130 131 return 0; 132 } 133 134 static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1, 135 unsigned int new_code2) 136 { 137 int faulted; 138 mm_segment_t old_fs; 139 140 ip += 4; 141 safe_store_code(new_code2, ip, faulted); 142 if (unlikely(faulted)) 143 return -EFAULT; 144 145 ip -= 4; 146 safe_store_code(new_code1, ip, faulted); 147 if (unlikely(faulted)) 148 return -EFAULT; 149 150 old_fs = get_fs(); 151 set_fs(get_ds()); 152 flush_icache_range(ip, ip + 8); 153 set_fs(old_fs); 154 155 return 0; 156 } 157 #endif 158 159 /* 160 * The details about the calling site of mcount on MIPS 161 * 162 * 1. For kernel: 163 * 164 * move at, ra 165 * jal _mcount --> nop 166 * sub sp, sp, 8 --> nop (CONFIG_32BIT) 167 * 168 * 2. For modules: 169 * 170 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT 171 * 172 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005) 173 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT) 174 * move at, ra 175 * move $12, ra_address 176 * jalr v1 177 * sub sp, sp, 8 178 * 1: offset = 5 instructions 179 * 2.2 For the Other situations 180 * 181 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004) 182 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT) 183 * move at, ra 184 * jalr v1 185 * nop | move $12, ra_address | sub sp, sp, 8 186 * 1: offset = 4 instructions 187 */ 188 189 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS) 190 191 int ftrace_make_nop(struct module *mod, 192 struct dyn_ftrace *rec, unsigned long addr) 193 { 194 unsigned int new; 195 unsigned long ip = rec->ip; 196 197 /* 198 * If ip is in kernel space, no long call, otherwise, long call is 199 * needed. 200 */ 201 new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F; 202 #ifdef CONFIG_64BIT 203 return ftrace_modify_code(ip, new); 204 #else 205 /* 206 * On 32 bit MIPS platforms, gcc adds a stack adjust 207 * instruction in the delay slot after the branch to 208 * mcount and expects mcount to restore the sp on return. 209 * This is based on a legacy API and does nothing but 210 * waste instructions so it's being removed at runtime. 211 */ 212 return ftrace_modify_code_2(ip, new, INSN_NOP); 213 #endif 214 } 215 216 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 217 { 218 unsigned int new; 219 unsigned long ip = rec->ip; 220 221 new = in_kernel_space(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0]; 222 223 #ifdef CONFIG_64BIT 224 return ftrace_modify_code(ip, new); 225 #else 226 return ftrace_modify_code_2r(ip, new, in_kernel_space(ip) ? 227 INSN_NOP : insn_la_mcount[1]); 228 #endif 229 } 230 231 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call)) 232 233 int ftrace_update_ftrace_func(ftrace_func_t func) 234 { 235 unsigned int new; 236 237 new = INSN_JAL((unsigned long)func); 238 239 return ftrace_modify_code(FTRACE_CALL_IP, new); 240 } 241 242 int __init ftrace_dyn_arch_init(void) 243 { 244 /* Encode the instructions when booting */ 245 ftrace_dyn_arch_init_insns(); 246 247 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */ 248 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP); 249 250 return 0; 251 } 252 #endif /* CONFIG_DYNAMIC_FTRACE */ 253 254 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 255 256 #ifdef CONFIG_DYNAMIC_FTRACE 257 258 extern void ftrace_graph_call(void); 259 #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call)) 260 261 int ftrace_enable_ftrace_graph_caller(void) 262 { 263 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, 264 insn_j_ftrace_graph_caller); 265 } 266 267 int ftrace_disable_ftrace_graph_caller(void) 268 { 269 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP); 270 } 271 272 #endif /* CONFIG_DYNAMIC_FTRACE */ 273 274 #ifndef KBUILD_MCOUNT_RA_ADDRESS 275 276 #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */ 277 #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */ 278 #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */ 279 280 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long 281 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp) 282 { 283 unsigned long sp, ip, tmp; 284 unsigned int code; 285 int faulted; 286 287 /* 288 * For module, move the ip from the return address after the 289 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for 290 * kernel, move after the instruction "move ra, at"(offset is 16) 291 */ 292 ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24); 293 294 /* 295 * search the text until finding the non-store instruction or "s{d,w} 296 * ra, offset(sp)" instruction 297 */ 298 do { 299 /* get the code at "ip": code = *(unsigned int *)ip; */ 300 safe_load_code(code, ip, faulted); 301 302 if (unlikely(faulted)) 303 return 0; 304 /* 305 * If we hit the non-store instruction before finding where the 306 * ra is stored, then this is a leaf function and it does not 307 * store the ra on the stack 308 */ 309 if ((code & S_R_SP) != S_R_SP) 310 return parent_ra_addr; 311 312 /* Move to the next instruction */ 313 ip -= 4; 314 } while ((code & S_RA_SP) != S_RA_SP); 315 316 sp = fp + (code & OFFSET_MASK); 317 318 /* tmp = *(unsigned long *)sp; */ 319 safe_load_stack(tmp, sp, faulted); 320 if (unlikely(faulted)) 321 return 0; 322 323 if (tmp == old_parent_ra) 324 return sp; 325 return 0; 326 } 327 328 #endif /* !KBUILD_MCOUNT_RA_ADDRESS */ 329 330 /* 331 * Hook the return address and push it in the stack of return addrs 332 * in current thread info. 333 */ 334 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, 335 unsigned long fp) 336 { 337 unsigned long old_parent_ra; 338 struct ftrace_graph_ent trace; 339 unsigned long return_hooker = (unsigned long) 340 &return_to_handler; 341 int faulted, insns; 342 343 if (unlikely(ftrace_graph_is_dead())) 344 return; 345 346 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 347 return; 348 349 /* 350 * "parent_ra_addr" is the stack address saved the return address of 351 * the caller of _mcount. 352 * 353 * if the gcc < 4.5, a leaf function does not save the return address 354 * in the stack address, so, we "emulate" one in _mcount's stack space, 355 * and hijack it directly, but for a non-leaf function, it save the 356 * return address to the its own stack space, we can not hijack it 357 * directly, but need to find the real stack address, 358 * ftrace_get_parent_addr() does it! 359 * 360 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a 361 * non-leaf function, the location of the return address will be saved 362 * to $12 for us, and for a leaf function, only put a zero into $12. we 363 * do it in ftrace_graph_caller of mcount.S. 364 */ 365 366 /* old_parent_ra = *parent_ra_addr; */ 367 safe_load_stack(old_parent_ra, parent_ra_addr, faulted); 368 if (unlikely(faulted)) 369 goto out; 370 #ifndef KBUILD_MCOUNT_RA_ADDRESS 371 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra, 372 old_parent_ra, (unsigned long)parent_ra_addr, fp); 373 /* 374 * If fails when getting the stack address of the non-leaf function's 375 * ra, stop function graph tracer and return 376 */ 377 if (parent_ra_addr == 0) 378 goto out; 379 #endif 380 /* *parent_ra_addr = return_hooker; */ 381 safe_store_stack(return_hooker, parent_ra_addr, faulted); 382 if (unlikely(faulted)) 383 goto out; 384 385 if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp) 386 == -EBUSY) { 387 *parent_ra_addr = old_parent_ra; 388 return; 389 } 390 391 /* 392 * Get the recorded ip of the current mcount calling site in the 393 * __mcount_loc section, which will be used to filter the function 394 * entries configured through the tracing/set_graph_function interface. 395 */ 396 397 insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1; 398 trace.func = self_ra - (MCOUNT_INSN_SIZE * insns); 399 400 /* Only trace if the calling function expects to */ 401 if (!ftrace_graph_entry(&trace)) { 402 current->curr_ret_stack--; 403 *parent_ra_addr = old_parent_ra; 404 } 405 return; 406 out: 407 ftrace_graph_stop(); 408 WARN_ON(1); 409 } 410 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 411 412 #ifdef CONFIG_FTRACE_SYSCALLS 413 414 #ifdef CONFIG_32BIT 415 unsigned long __init arch_syscall_addr(int nr) 416 { 417 return (unsigned long)sys_call_table[nr - __NR_O32_Linux]; 418 } 419 #endif 420 421 #ifdef CONFIG_64BIT 422 423 unsigned long __init arch_syscall_addr(int nr) 424 { 425 #ifdef CONFIG_MIPS32_N32 426 if (nr >= __NR_N32_Linux && nr <= __NR_N32_Linux + __NR_N32_Linux_syscalls) 427 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux]; 428 #endif 429 if (nr >= __NR_64_Linux && nr <= __NR_64_Linux + __NR_64_Linux_syscalls) 430 return (unsigned long)sys_call_table[nr - __NR_64_Linux]; 431 #ifdef CONFIG_MIPS32_O32 432 if (nr >= __NR_O32_Linux && nr <= __NR_O32_Linux + __NR_O32_Linux_syscalls) 433 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux]; 434 #endif 435 436 return (unsigned long) &sys_ni_syscall; 437 } 438 #endif 439 440 #endif /* CONFIG_FTRACE_SYSCALLS */ 441