1 /* 2 * Code for replacing ftrace calls with jumps. 3 * 4 * Copyright (C) 2007-2008 Steven Rostedt <[email protected]> 5 * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China 6 * Author: Wu Zhangjin <[email protected]> 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_lui_v1_hi16_mcount __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 /* lui v1, hi16_mcount */ 75 v1 = 3; 76 buf = (u32 *)&insn_lui_v1_hi16_mcount; 77 UASM_i_LA_mostly(&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; 114 115 safe_store_code(new_code1, ip, faulted); 116 if (unlikely(faulted)) 117 return -EFAULT; 118 ip += 4; 119 safe_store_code(new_code2, ip, faulted); 120 if (unlikely(faulted)) 121 return -EFAULT; 122 flush_icache_range(ip, ip + 8); /* original ip + 12 */ 123 return 0; 124 } 125 #endif 126 127 /* 128 * The details about the calling site of mcount on MIPS 129 * 130 * 1. For kernel: 131 * 132 * move at, ra 133 * jal _mcount --> nop 134 * 135 * 2. For modules: 136 * 137 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT 138 * 139 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005) 140 * addiu v1, v1, low_16bit_of_mcount 141 * move at, ra 142 * move $12, ra_address 143 * jalr v1 144 * sub sp, sp, 8 145 * 1: offset = 5 instructions 146 * 2.2 For the Other situations 147 * 148 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004) 149 * addiu v1, v1, low_16bit_of_mcount 150 * move at, ra 151 * jalr v1 152 * nop | move $12, ra_address | sub sp, sp, 8 153 * 1: offset = 4 instructions 154 */ 155 156 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS) 157 158 int ftrace_make_nop(struct module *mod, 159 struct dyn_ftrace *rec, unsigned long addr) 160 { 161 unsigned int new; 162 unsigned long ip = rec->ip; 163 164 /* 165 * If ip is in kernel space, no long call, otherwise, long call is 166 * needed. 167 */ 168 new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F; 169 #ifdef CONFIG_64BIT 170 return ftrace_modify_code(ip, new); 171 #else 172 /* 173 * On 32 bit MIPS platforms, gcc adds a stack adjust 174 * instruction in the delay slot after the branch to 175 * mcount and expects mcount to restore the sp on return. 176 * This is based on a legacy API and does nothing but 177 * waste instructions so it's being removed at runtime. 178 */ 179 return ftrace_modify_code_2(ip, new, INSN_NOP); 180 #endif 181 } 182 183 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 184 { 185 unsigned int new; 186 unsigned long ip = rec->ip; 187 188 new = in_kernel_space(ip) ? insn_jal_ftrace_caller : 189 insn_lui_v1_hi16_mcount; 190 191 return ftrace_modify_code(ip, new); 192 } 193 194 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call)) 195 196 int ftrace_update_ftrace_func(ftrace_func_t func) 197 { 198 unsigned int new; 199 200 new = INSN_JAL((unsigned long)func); 201 202 return ftrace_modify_code(FTRACE_CALL_IP, new); 203 } 204 205 int __init ftrace_dyn_arch_init(void *data) 206 { 207 /* Encode the instructions when booting */ 208 ftrace_dyn_arch_init_insns(); 209 210 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */ 211 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP); 212 213 /* The return code is retured via data */ 214 *(unsigned long *)data = 0; 215 216 return 0; 217 } 218 #endif /* CONFIG_DYNAMIC_FTRACE */ 219 220 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 221 222 #ifdef CONFIG_DYNAMIC_FTRACE 223 224 extern void ftrace_graph_call(void); 225 #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call)) 226 227 int ftrace_enable_ftrace_graph_caller(void) 228 { 229 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, 230 insn_j_ftrace_graph_caller); 231 } 232 233 int ftrace_disable_ftrace_graph_caller(void) 234 { 235 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP); 236 } 237 238 #endif /* CONFIG_DYNAMIC_FTRACE */ 239 240 #ifndef KBUILD_MCOUNT_RA_ADDRESS 241 242 #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */ 243 #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */ 244 #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */ 245 246 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long 247 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp) 248 { 249 unsigned long sp, ip, tmp; 250 unsigned int code; 251 int faulted; 252 253 /* 254 * For module, move the ip from the return address after the 255 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for 256 * kernel, move after the instruction "move ra, at"(offset is 16) 257 */ 258 ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24); 259 260 /* 261 * search the text until finding the non-store instruction or "s{d,w} 262 * ra, offset(sp)" instruction 263 */ 264 do { 265 /* get the code at "ip": code = *(unsigned int *)ip; */ 266 safe_load_code(code, ip, faulted); 267 268 if (unlikely(faulted)) 269 return 0; 270 /* 271 * If we hit the non-store instruction before finding where the 272 * ra is stored, then this is a leaf function and it does not 273 * store the ra on the stack 274 */ 275 if ((code & S_R_SP) != S_R_SP) 276 return parent_ra_addr; 277 278 /* Move to the next instruction */ 279 ip -= 4; 280 } while ((code & S_RA_SP) != S_RA_SP); 281 282 sp = fp + (code & OFFSET_MASK); 283 284 /* tmp = *(unsigned long *)sp; */ 285 safe_load_stack(tmp, sp, faulted); 286 if (unlikely(faulted)) 287 return 0; 288 289 if (tmp == old_parent_ra) 290 return sp; 291 return 0; 292 } 293 294 #endif /* !KBUILD_MCOUNT_RA_ADDRESS */ 295 296 /* 297 * Hook the return address and push it in the stack of return addrs 298 * in current thread info. 299 */ 300 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, 301 unsigned long fp) 302 { 303 unsigned long old_parent_ra; 304 struct ftrace_graph_ent trace; 305 unsigned long return_hooker = (unsigned long) 306 &return_to_handler; 307 int faulted, insns; 308 309 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 310 return; 311 312 /* 313 * "parent_ra_addr" is the stack address saved the return address of 314 * the caller of _mcount. 315 * 316 * if the gcc < 4.5, a leaf function does not save the return address 317 * in the stack address, so, we "emulate" one in _mcount's stack space, 318 * and hijack it directly, but for a non-leaf function, it save the 319 * return address to the its own stack space, we can not hijack it 320 * directly, but need to find the real stack address, 321 * ftrace_get_parent_addr() does it! 322 * 323 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a 324 * non-leaf function, the location of the return address will be saved 325 * to $12 for us, and for a leaf function, only put a zero into $12. we 326 * do it in ftrace_graph_caller of mcount.S. 327 */ 328 329 /* old_parent_ra = *parent_ra_addr; */ 330 safe_load_stack(old_parent_ra, parent_ra_addr, faulted); 331 if (unlikely(faulted)) 332 goto out; 333 #ifndef KBUILD_MCOUNT_RA_ADDRESS 334 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra, 335 old_parent_ra, (unsigned long)parent_ra_addr, fp); 336 /* 337 * If fails when getting the stack address of the non-leaf function's 338 * ra, stop function graph tracer and return 339 */ 340 if (parent_ra_addr == 0) 341 goto out; 342 #endif 343 /* *parent_ra_addr = return_hooker; */ 344 safe_store_stack(return_hooker, parent_ra_addr, faulted); 345 if (unlikely(faulted)) 346 goto out; 347 348 if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp) 349 == -EBUSY) { 350 *parent_ra_addr = old_parent_ra; 351 return; 352 } 353 354 /* 355 * Get the recorded ip of the current mcount calling site in the 356 * __mcount_loc section, which will be used to filter the function 357 * entries configured through the tracing/set_graph_function interface. 358 */ 359 360 insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1; 361 trace.func = self_ra - (MCOUNT_INSN_SIZE * insns); 362 363 /* Only trace if the calling function expects to */ 364 if (!ftrace_graph_entry(&trace)) { 365 current->curr_ret_stack--; 366 *parent_ra_addr = old_parent_ra; 367 } 368 return; 369 out: 370 ftrace_graph_stop(); 371 WARN_ON(1); 372 } 373 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 374 375 #ifdef CONFIG_FTRACE_SYSCALLS 376 377 #ifdef CONFIG_32BIT 378 unsigned long __init arch_syscall_addr(int nr) 379 { 380 return (unsigned long)sys_call_table[nr - __NR_O32_Linux]; 381 } 382 #endif 383 384 #ifdef CONFIG_64BIT 385 386 unsigned long __init arch_syscall_addr(int nr) 387 { 388 #ifdef CONFIG_MIPS32_N32 389 if (nr >= __NR_N32_Linux && nr <= __NR_N32_Linux + __NR_N32_Linux_syscalls) 390 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux]; 391 #endif 392 if (nr >= __NR_64_Linux && nr <= __NR_64_Linux + __NR_64_Linux_syscalls) 393 return (unsigned long)sys_call_table[nr - __NR_64_Linux]; 394 #ifdef CONFIG_MIPS32_O32 395 if (nr >= __NR_O32_Linux && nr <= __NR_O32_Linux + __NR_O32_Linux_syscalls) 396 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux]; 397 #endif 398 399 return (unsigned long) &sys_ni_syscall; 400 } 401 #endif 402 403 #endif /* CONFIG_FTRACE_SYSCALLS */ 404