1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Code for replacing ftrace calls with jumps. 4 * 5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> 6 * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China 7 * Author: Wu Zhangjin <wuzhangjin@gmail.com> 8 * 9 * Thanks goes to Steven Rostedt for writing the original x86 version. 10 */ 11 12 #include <linux/uaccess.h> 13 #include <linux/init.h> 14 #include <linux/ftrace.h> 15 #include <linux/syscalls.h> 16 17 #include <asm/asm.h> 18 #include <asm/asm-offsets.h> 19 #include <asm/cacheflush.h> 20 #include <asm/syscall.h> 21 #include <asm/uasm.h> 22 #include <asm/unistd.h> 23 24 #include <asm-generic/sections.h> 25 26 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT) 27 #define MCOUNT_OFFSET_INSNS 5 28 #else 29 #define MCOUNT_OFFSET_INSNS 4 30 #endif 31 32 #ifdef CONFIG_DYNAMIC_FTRACE 33 34 /* Arch override because MIPS doesn't need to run this from stop_machine() */ 35 void arch_ftrace_update_code(int command) 36 { 37 ftrace_modify_all_code(command); 38 } 39 40 #endif 41 42 #ifdef CONFIG_DYNAMIC_FTRACE 43 44 #define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */ 45 #define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */ 46 #define JUMP_RANGE_MASK ((1UL << 28) - 1) 47 48 #define INSN_NOP 0x00000000 /* nop */ 49 #define INSN_JAL(addr) \ 50 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK))) 51 52 static unsigned int insn_jal_ftrace_caller __read_mostly; 53 static unsigned int insn_la_mcount[2] __read_mostly; 54 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly; 55 56 static inline void ftrace_dyn_arch_init_insns(void) 57 { 58 u32 *buf; 59 unsigned int v1; 60 61 /* la v1, _mcount */ 62 v1 = 3; 63 buf = (u32 *)&insn_la_mcount[0]; 64 UASM_i_LA(&buf, v1, MCOUNT_ADDR); 65 66 /* jal (ftrace_caller + 8), jump over the first two instruction */ 67 buf = (u32 *)&insn_jal_ftrace_caller; 68 uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK); 69 70 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 71 /* j ftrace_graph_caller */ 72 buf = (u32 *)&insn_j_ftrace_graph_caller; 73 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK); 74 #endif 75 } 76 77 static int ftrace_modify_code(unsigned long ip, unsigned int new_code) 78 { 79 int faulted; 80 mm_segment_t old_fs; 81 82 /* *(unsigned int *)ip = new_code; */ 83 safe_store_code(new_code, ip, faulted); 84 85 if (unlikely(faulted)) 86 return -EFAULT; 87 88 old_fs = get_fs(); 89 set_fs(KERNEL_DS); 90 flush_icache_range(ip, ip + 8); 91 set_fs(old_fs); 92 93 return 0; 94 } 95 96 #ifndef CONFIG_64BIT 97 static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1, 98 unsigned int new_code2) 99 { 100 int faulted; 101 mm_segment_t old_fs; 102 103 safe_store_code(new_code1, ip, faulted); 104 if (unlikely(faulted)) 105 return -EFAULT; 106 107 ip += 4; 108 safe_store_code(new_code2, ip, faulted); 109 if (unlikely(faulted)) 110 return -EFAULT; 111 112 ip -= 4; 113 old_fs = get_fs(); 114 set_fs(KERNEL_DS); 115 flush_icache_range(ip, ip + 8); 116 set_fs(old_fs); 117 118 return 0; 119 } 120 121 static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1, 122 unsigned int new_code2) 123 { 124 int faulted; 125 mm_segment_t old_fs; 126 127 ip += 4; 128 safe_store_code(new_code2, ip, faulted); 129 if (unlikely(faulted)) 130 return -EFAULT; 131 132 ip -= 4; 133 safe_store_code(new_code1, ip, faulted); 134 if (unlikely(faulted)) 135 return -EFAULT; 136 137 old_fs = get_fs(); 138 set_fs(KERNEL_DS); 139 flush_icache_range(ip, ip + 8); 140 set_fs(old_fs); 141 142 return 0; 143 } 144 #endif 145 146 /* 147 * The details about the calling site of mcount on MIPS 148 * 149 * 1. For kernel: 150 * 151 * move at, ra 152 * jal _mcount --> nop 153 * sub sp, sp, 8 --> nop (CONFIG_32BIT) 154 * 155 * 2. For modules: 156 * 157 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT 158 * 159 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005) 160 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT) 161 * move at, ra 162 * move $12, ra_address 163 * jalr v1 164 * sub sp, sp, 8 165 * 1: offset = 5 instructions 166 * 2.2 For the Other situations 167 * 168 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004) 169 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT) 170 * move at, ra 171 * jalr v1 172 * nop | move $12, ra_address | sub sp, sp, 8 173 * 1: offset = 4 instructions 174 */ 175 176 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS) 177 178 int ftrace_make_nop(struct module *mod, 179 struct dyn_ftrace *rec, unsigned long addr) 180 { 181 unsigned int new; 182 unsigned long ip = rec->ip; 183 184 /* 185 * If ip is in kernel space, no long call, otherwise, long call is 186 * needed. 187 */ 188 new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F; 189 #ifdef CONFIG_64BIT 190 return ftrace_modify_code(ip, new); 191 #else 192 /* 193 * On 32 bit MIPS platforms, gcc adds a stack adjust 194 * instruction in the delay slot after the branch to 195 * mcount and expects mcount to restore the sp on return. 196 * This is based on a legacy API and does nothing but 197 * waste instructions so it's being removed at runtime. 198 */ 199 return ftrace_modify_code_2(ip, new, INSN_NOP); 200 #endif 201 } 202 203 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 204 { 205 unsigned int new; 206 unsigned long ip = rec->ip; 207 208 new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0]; 209 210 #ifdef CONFIG_64BIT 211 return ftrace_modify_code(ip, new); 212 #else 213 return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ? 214 INSN_NOP : insn_la_mcount[1]); 215 #endif 216 } 217 218 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call)) 219 220 int ftrace_update_ftrace_func(ftrace_func_t func) 221 { 222 unsigned int new; 223 224 new = INSN_JAL((unsigned long)func); 225 226 return ftrace_modify_code(FTRACE_CALL_IP, new); 227 } 228 229 int __init ftrace_dyn_arch_init(void) 230 { 231 /* Encode the instructions when booting */ 232 ftrace_dyn_arch_init_insns(); 233 234 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */ 235 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP); 236 237 return 0; 238 } 239 #endif /* CONFIG_DYNAMIC_FTRACE */ 240 241 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 242 243 #ifdef CONFIG_DYNAMIC_FTRACE 244 245 extern void ftrace_graph_call(void); 246 #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call)) 247 248 int ftrace_enable_ftrace_graph_caller(void) 249 { 250 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, 251 insn_j_ftrace_graph_caller); 252 } 253 254 int ftrace_disable_ftrace_graph_caller(void) 255 { 256 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP); 257 } 258 259 #endif /* CONFIG_DYNAMIC_FTRACE */ 260 261 #ifndef KBUILD_MCOUNT_RA_ADDRESS 262 263 #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */ 264 #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */ 265 #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */ 266 267 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long 268 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp) 269 { 270 unsigned long sp, ip, tmp; 271 unsigned int code; 272 int faulted; 273 274 /* 275 * For module, move the ip from the return address after the 276 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for 277 * kernel, move after the instruction "move ra, at"(offset is 16) 278 */ 279 ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24); 280 281 /* 282 * search the text until finding the non-store instruction or "s{d,w} 283 * ra, offset(sp)" instruction 284 */ 285 do { 286 /* get the code at "ip": code = *(unsigned int *)ip; */ 287 safe_load_code(code, ip, faulted); 288 289 if (unlikely(faulted)) 290 return 0; 291 /* 292 * If we hit the non-store instruction before finding where the 293 * ra is stored, then this is a leaf function and it does not 294 * store the ra on the stack 295 */ 296 if ((code & S_R_SP) != S_R_SP) 297 return parent_ra_addr; 298 299 /* Move to the next instruction */ 300 ip -= 4; 301 } while ((code & S_RA_SP) != S_RA_SP); 302 303 sp = fp + (code & OFFSET_MASK); 304 305 /* tmp = *(unsigned long *)sp; */ 306 safe_load_stack(tmp, sp, faulted); 307 if (unlikely(faulted)) 308 return 0; 309 310 if (tmp == old_parent_ra) 311 return sp; 312 return 0; 313 } 314 315 #endif /* !KBUILD_MCOUNT_RA_ADDRESS */ 316 317 /* 318 * Hook the return address and push it in the stack of return addrs 319 * in current thread info. 320 */ 321 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, 322 unsigned long fp) 323 { 324 unsigned long old_parent_ra; 325 unsigned long return_hooker = (unsigned long) 326 &return_to_handler; 327 int faulted, insns; 328 329 if (unlikely(ftrace_graph_is_dead())) 330 return; 331 332 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 333 return; 334 335 /* 336 * "parent_ra_addr" is the stack address where the return address of 337 * the caller of _mcount is saved. 338 * 339 * If gcc < 4.5, a leaf function does not save the return address 340 * in the stack address, so we "emulate" one in _mcount's stack space, 341 * and hijack it directly. 342 * For a non-leaf function, it does save the return address to its own 343 * stack space, so we can not hijack it directly, but need to find the 344 * real stack address, which is done by ftrace_get_parent_addr(). 345 * 346 * If gcc >= 4.5, with the new -mmcount-ra-address option, for a 347 * non-leaf function, the location of the return address will be saved 348 * to $12 for us. 349 * For a leaf function, it just puts a zero into $12, so we handle 350 * it in ftrace_graph_caller() of mcount.S. 351 */ 352 353 /* old_parent_ra = *parent_ra_addr; */ 354 safe_load_stack(old_parent_ra, parent_ra_addr, faulted); 355 if (unlikely(faulted)) 356 goto out; 357 #ifndef KBUILD_MCOUNT_RA_ADDRESS 358 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra, 359 old_parent_ra, (unsigned long)parent_ra_addr, fp); 360 /* 361 * If fails when getting the stack address of the non-leaf function's 362 * ra, stop function graph tracer and return 363 */ 364 if (parent_ra_addr == NULL) 365 goto out; 366 #endif 367 /* *parent_ra_addr = return_hooker; */ 368 safe_store_stack(return_hooker, parent_ra_addr, faulted); 369 if (unlikely(faulted)) 370 goto out; 371 372 /* 373 * Get the recorded ip of the current mcount calling site in the 374 * __mcount_loc section, which will be used to filter the function 375 * entries configured through the tracing/set_graph_function interface. 376 */ 377 378 insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1; 379 self_ra -= (MCOUNT_INSN_SIZE * insns); 380 381 if (function_graph_enter(old_parent_ra, self_ra, fp, NULL)) 382 *parent_ra_addr = old_parent_ra; 383 return; 384 out: 385 ftrace_graph_stop(); 386 WARN_ON(1); 387 } 388 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 389 390 #ifdef CONFIG_FTRACE_SYSCALLS 391 392 #ifdef CONFIG_32BIT 393 unsigned long __init arch_syscall_addr(int nr) 394 { 395 return (unsigned long)sys_call_table[nr - __NR_O32_Linux]; 396 } 397 #endif 398 399 #ifdef CONFIG_64BIT 400 401 unsigned long __init arch_syscall_addr(int nr) 402 { 403 #ifdef CONFIG_MIPS32_N32 404 if (nr >= __NR_N32_Linux && nr < __NR_N32_Linux + __NR_N32_Linux_syscalls) 405 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux]; 406 #endif 407 if (nr >= __NR_64_Linux && nr < __NR_64_Linux + __NR_64_Linux_syscalls) 408 return (unsigned long)sys_call_table[nr - __NR_64_Linux]; 409 #ifdef CONFIG_MIPS32_O32 410 if (nr >= __NR_O32_Linux && nr < __NR_O32_Linux + __NR_O32_Linux_syscalls) 411 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux]; 412 #endif 413 414 return (unsigned long) &sys_ni_syscall; 415 } 416 #endif 417 418 #endif /* CONFIG_FTRACE_SYSCALLS */ 419