1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Infrastructure to took into function calls and returns. 4 * Copyright (c) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com> 5 * Mostly borrowed from function tracer which 6 * is Copyright (c) Steven Rostedt <srostedt@redhat.com> 7 * 8 * Highly modified by Steven Rostedt (VMware). 9 */ 10 #include <linux/bits.h> 11 #include <linux/jump_label.h> 12 #include <linux/suspend.h> 13 #include <linux/ftrace.h> 14 #include <linux/static_call.h> 15 #include <linux/slab.h> 16 17 #include <trace/events/sched.h> 18 19 #include "ftrace_internal.h" 20 #include "trace.h" 21 22 /* 23 * FGRAPH_FRAME_SIZE: Size in bytes of the meta data on the shadow stack 24 * FGRAPH_FRAME_OFFSET: Size in long words of the meta data frame 25 */ 26 #define FGRAPH_FRAME_SIZE sizeof(struct ftrace_ret_stack) 27 #define FGRAPH_FRAME_OFFSET DIV_ROUND_UP(FGRAPH_FRAME_SIZE, sizeof(long)) 28 29 /* 30 * On entry to a function (via function_graph_enter()), a new fgraph frame 31 * (ftrace_ret_stack) is pushed onto the stack as well as a word that 32 * holds a bitmask and a type (called "bitmap"). The bitmap is defined as: 33 * 34 * bits: 0 - 9 offset in words from the previous ftrace_ret_stack 35 * 36 * bits: 10 - 11 Type of storage 37 * 0 - reserved 38 * 1 - bitmap of fgraph_array index 39 * 2 - reserved data 40 * 41 * For type with "bitmap of fgraph_array index" (FGRAPH_TYPE_BITMAP): 42 * bits: 12 - 27 The bitmap of fgraph_ops fgraph_array index 43 * That is, it's a bitmask of 0-15 (16 bits) 44 * where if a corresponding ops in the fgraph_array[] 45 * expects a callback from the return of the function 46 * it's corresponding bit will be set. 47 * 48 * 49 * The top of the ret_stack (when not empty) will always have a reference 50 * word that points to the last fgraph frame that was saved. 51 * 52 * For reserved data: 53 * bits: 12 - 17 The size in words that is stored 54 * bits: 18 - 23 The index of fgraph_array, which shows who is stored 55 * 56 * That is, at the end of function_graph_enter, if the first and forth 57 * fgraph_ops on the fgraph_array[] (index 0 and 3) needs their retfunc called 58 * on the return of the function being traced, and the forth fgraph_ops 59 * stored two words of data, this is what will be on the task's shadow 60 * ret_stack: (the stack grows upward) 61 * 62 * ret_stack[SHADOW_STACK_OFFSET] 63 * | SHADOW_STACK_TASK_VARS(ret_stack)[15] | 64 * ... 65 * | SHADOW_STACK_TASK_VARS(ret_stack)[0] | 66 * ret_stack[SHADOW_STACK_MAX_OFFSET] 67 * ... 68 * | | <- task->curr_ret_stack 69 * +--------------------------------------------+ 70 * | (3 << 12) | (3 << 10) | FGRAPH_FRAME_OFFSET| 71 * | *or put another way* | 72 * | (3 << FGRAPH_DATA_INDEX_SHIFT)| \ | This is for fgraph_ops[3]. 73 * | ((2 - 1) << FGRAPH_DATA_SHIFT)| \ | The data size is 2 words. 74 * | (FGRAPH_TYPE_DATA << FGRAPH_TYPE_SHIFT)| \ | 75 * | (offset2:FGRAPH_FRAME_OFFSET+3) | <- the offset2 is from here 76 * +--------------------------------------------+ ( It is 4 words from the ret_stack) 77 * | STORED DATA WORD 2 | 78 * | STORED DATA WORD 1 | 79 * +--------------------------------------------+ 80 * | (9 << 12) | (1 << 10) | FGRAPH_FRAME_OFFSET| 81 * | *or put another way* | 82 * | (BIT(3)|BIT(0)) << FGRAPH_INDEX_SHIFT | \ | 83 * | FGRAPH_TYPE_BITMAP << FGRAPH_TYPE_SHIFT| \ | 84 * | (offset1:FGRAPH_FRAME_OFFSET) | <- the offset1 is from here 85 * +--------------------------------------------+ 86 * | struct ftrace_ret_stack | 87 * | (stores the saved ret pointer) | <- the offset points here 88 * +--------------------------------------------+ 89 * | (X) | (N) | ( N words away from 90 * | | previous ret_stack) 91 * ... 92 * ret_stack[0] 93 * 94 * If a backtrace is required, and the real return pointer needs to be 95 * fetched, then it looks at the task's curr_ret_stack offset, if it 96 * is greater than zero (reserved, or right before popped), it would mask 97 * the value by FGRAPH_FRAME_OFFSET_MASK to get the offset of the 98 * ftrace_ret_stack structure stored on the shadow stack. 99 */ 100 101 /* 102 * The following is for the top word on the stack: 103 * 104 * FGRAPH_FRAME_OFFSET (0-9) holds the offset delta to the fgraph frame 105 * FGRAPH_TYPE (10-11) holds the type of word this is. 106 * (RESERVED or BITMAP) 107 */ 108 #define FGRAPH_FRAME_OFFSET_BITS 10 109 #define FGRAPH_FRAME_OFFSET_MASK GENMASK(FGRAPH_FRAME_OFFSET_BITS - 1, 0) 110 111 #define FGRAPH_TYPE_BITS 2 112 #define FGRAPH_TYPE_MASK GENMASK(FGRAPH_TYPE_BITS - 1, 0) 113 #define FGRAPH_TYPE_SHIFT FGRAPH_FRAME_OFFSET_BITS 114 115 enum { 116 FGRAPH_TYPE_RESERVED = 0, 117 FGRAPH_TYPE_BITMAP = 1, 118 FGRAPH_TYPE_DATA = 2, 119 }; 120 121 /* 122 * For BITMAP type: 123 * FGRAPH_INDEX (12-27) bits holding the gops index wanting return callback called 124 */ 125 #define FGRAPH_INDEX_BITS 16 126 #define FGRAPH_INDEX_MASK GENMASK(FGRAPH_INDEX_BITS - 1, 0) 127 #define FGRAPH_INDEX_SHIFT (FGRAPH_TYPE_SHIFT + FGRAPH_TYPE_BITS) 128 129 /* 130 * For DATA type: 131 * FGRAPH_DATA (12-17) bits hold the size of data (in words) 132 * FGRAPH_INDEX (18-23) bits hold the index for which gops->idx the data is for 133 * 134 * Note: 135 * data_size == 0 means 1 word, and 31 (=2^5 - 1) means 32 words. 136 */ 137 #define FGRAPH_DATA_BITS 5 138 #define FGRAPH_DATA_MASK GENMASK(FGRAPH_DATA_BITS - 1, 0) 139 #define FGRAPH_DATA_SHIFT (FGRAPH_TYPE_SHIFT + FGRAPH_TYPE_BITS) 140 #define FGRAPH_MAX_DATA_SIZE (sizeof(long) * (1 << FGRAPH_DATA_BITS)) 141 142 #define FGRAPH_DATA_INDEX_BITS 4 143 #define FGRAPH_DATA_INDEX_MASK GENMASK(FGRAPH_DATA_INDEX_BITS - 1, 0) 144 #define FGRAPH_DATA_INDEX_SHIFT (FGRAPH_DATA_SHIFT + FGRAPH_DATA_BITS) 145 146 #define FGRAPH_MAX_INDEX \ 147 ((FGRAPH_INDEX_SIZE << FGRAPH_DATA_BITS) + FGRAPH_RET_INDEX) 148 149 #define FGRAPH_ARRAY_SIZE FGRAPH_INDEX_BITS 150 151 /* 152 * SHADOW_STACK_SIZE: The size in bytes of the entire shadow stack 153 * SHADOW_STACK_OFFSET: The size in long words of the shadow stack 154 * SHADOW_STACK_MAX_OFFSET: The max offset of the stack for a new frame to be added 155 */ 156 #define SHADOW_STACK_SIZE (PAGE_SIZE) 157 #define SHADOW_STACK_OFFSET (SHADOW_STACK_SIZE / sizeof(long)) 158 /* Leave on a buffer at the end */ 159 #define SHADOW_STACK_MAX_OFFSET \ 160 (SHADOW_STACK_OFFSET - (FGRAPH_FRAME_OFFSET + 1 + FGRAPH_ARRAY_SIZE)) 161 162 /* RET_STACK(): Return the frame from a given @offset from task @t */ 163 #define RET_STACK(t, offset) ((struct ftrace_ret_stack *)(&(t)->ret_stack[offset])) 164 165 /* 166 * Each fgraph_ops has a reservered unsigned long at the end (top) of the 167 * ret_stack to store task specific state. 168 */ 169 #define SHADOW_STACK_TASK_VARS(ret_stack) \ 170 ((unsigned long *)(&(ret_stack)[SHADOW_STACK_OFFSET - FGRAPH_ARRAY_SIZE])) 171 172 DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph); 173 int ftrace_graph_active; 174 175 static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE]; 176 static unsigned long fgraph_array_bitmask; 177 178 /* LRU index table for fgraph_array */ 179 static int fgraph_lru_table[FGRAPH_ARRAY_SIZE]; 180 static int fgraph_lru_next; 181 static int fgraph_lru_last; 182 183 /* Initialize fgraph_lru_table with unused index */ 184 static void fgraph_lru_init(void) 185 { 186 int i; 187 188 for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) 189 fgraph_lru_table[i] = i; 190 } 191 192 /* Release the used index to the LRU table */ 193 static int fgraph_lru_release_index(int idx) 194 { 195 if (idx < 0 || idx >= FGRAPH_ARRAY_SIZE || 196 WARN_ON_ONCE(fgraph_lru_table[fgraph_lru_last] != -1)) 197 return -1; 198 199 fgraph_lru_table[fgraph_lru_last] = idx; 200 fgraph_lru_last = (fgraph_lru_last + 1) % FGRAPH_ARRAY_SIZE; 201 202 clear_bit(idx, &fgraph_array_bitmask); 203 return 0; 204 } 205 206 /* Allocate a new index from LRU table */ 207 static int fgraph_lru_alloc_index(void) 208 { 209 int idx = fgraph_lru_table[fgraph_lru_next]; 210 211 /* No id is available */ 212 if (idx == -1) 213 return -1; 214 215 fgraph_lru_table[fgraph_lru_next] = -1; 216 fgraph_lru_next = (fgraph_lru_next + 1) % FGRAPH_ARRAY_SIZE; 217 218 set_bit(idx, &fgraph_array_bitmask); 219 return idx; 220 } 221 222 /* Get the offset to the fgraph frame from a ret_stack value */ 223 static inline int __get_offset(unsigned long val) 224 { 225 return val & FGRAPH_FRAME_OFFSET_MASK; 226 } 227 228 /* Get the type of word from a ret_stack value */ 229 static inline int __get_type(unsigned long val) 230 { 231 return (val >> FGRAPH_TYPE_SHIFT) & FGRAPH_TYPE_MASK; 232 } 233 234 /* Get the data_index for a DATA type ret_stack word */ 235 static inline int __get_data_index(unsigned long val) 236 { 237 return (val >> FGRAPH_DATA_INDEX_SHIFT) & FGRAPH_DATA_INDEX_MASK; 238 } 239 240 /* Get the data_size for a DATA type ret_stack word */ 241 static inline int __get_data_size(unsigned long val) 242 { 243 return ((val >> FGRAPH_DATA_SHIFT) & FGRAPH_DATA_MASK) + 1; 244 } 245 246 /* Get the word from the ret_stack at @offset */ 247 static inline unsigned long get_fgraph_entry(struct task_struct *t, int offset) 248 { 249 return t->ret_stack[offset]; 250 } 251 252 /* Get the FRAME_OFFSET from the word from the @offset on ret_stack */ 253 static inline int get_frame_offset(struct task_struct *t, int offset) 254 { 255 return __get_offset(t->ret_stack[offset]); 256 } 257 258 /* For BITMAP type: get the bitmask from the @offset at ret_stack */ 259 static inline unsigned long 260 get_bitmap_bits(struct task_struct *t, int offset) 261 { 262 return (t->ret_stack[offset] >> FGRAPH_INDEX_SHIFT) & FGRAPH_INDEX_MASK; 263 } 264 265 /* Write the bitmap to the ret_stack at @offset (does index, offset and bitmask) */ 266 static inline void 267 set_bitmap(struct task_struct *t, int offset, unsigned long bitmap) 268 { 269 t->ret_stack[offset] = (bitmap << FGRAPH_INDEX_SHIFT) | 270 (FGRAPH_TYPE_BITMAP << FGRAPH_TYPE_SHIFT) | FGRAPH_FRAME_OFFSET; 271 } 272 273 /* For DATA type: get the data saved under the ret_stack word at @offset */ 274 static inline void *get_data_type_data(struct task_struct *t, int offset) 275 { 276 unsigned long val = t->ret_stack[offset]; 277 278 if (__get_type(val) != FGRAPH_TYPE_DATA) 279 return NULL; 280 offset -= __get_data_size(val); 281 return (void *)&t->ret_stack[offset]; 282 } 283 284 /* Create the ret_stack word for a DATA type */ 285 static inline unsigned long make_data_type_val(int idx, int size, int offset) 286 { 287 return (idx << FGRAPH_DATA_INDEX_SHIFT) | 288 ((size - 1) << FGRAPH_DATA_SHIFT) | 289 (FGRAPH_TYPE_DATA << FGRAPH_TYPE_SHIFT) | offset; 290 } 291 292 /* ftrace_graph_entry set to this to tell some archs to run function graph */ 293 static int entry_run(struct ftrace_graph_ent *trace, struct fgraph_ops *ops) 294 { 295 return 0; 296 } 297 298 /* ftrace_graph_return set to this to tell some archs to run function graph */ 299 static void return_run(struct ftrace_graph_ret *trace, struct fgraph_ops *ops) 300 { 301 } 302 303 static void ret_stack_set_task_var(struct task_struct *t, int idx, long val) 304 { 305 unsigned long *gvals = SHADOW_STACK_TASK_VARS(t->ret_stack); 306 307 gvals[idx] = val; 308 } 309 310 static unsigned long * 311 ret_stack_get_task_var(struct task_struct *t, int idx) 312 { 313 unsigned long *gvals = SHADOW_STACK_TASK_VARS(t->ret_stack); 314 315 return &gvals[idx]; 316 } 317 318 static void ret_stack_init_task_vars(unsigned long *ret_stack) 319 { 320 unsigned long *gvals = SHADOW_STACK_TASK_VARS(ret_stack); 321 322 memset(gvals, 0, sizeof(*gvals) * FGRAPH_ARRAY_SIZE); 323 } 324 325 /** 326 * fgraph_reserve_data - Reserve storage on the task's ret_stack 327 * @idx: The index of fgraph_array 328 * @size_bytes: The size in bytes to reserve 329 * 330 * Reserves space of up to FGRAPH_MAX_DATA_SIZE bytes on the 331 * task's ret_stack shadow stack, for a given fgraph_ops during 332 * the entryfunc() call. If entryfunc() returns zero, the storage 333 * is discarded. An entryfunc() can only call this once per iteration. 334 * The fgraph_ops retfunc() can retrieve this stored data with 335 * fgraph_retrieve_data(). 336 * 337 * Returns: On success, a pointer to the data on the stack. 338 * Otherwise, NULL if there's not enough space left on the 339 * ret_stack for the data, or if fgraph_reserve_data() was called 340 * more than once for a single entryfunc() call. 341 */ 342 void *fgraph_reserve_data(int idx, int size_bytes) 343 { 344 unsigned long val; 345 void *data; 346 int curr_ret_stack = current->curr_ret_stack; 347 int data_size; 348 349 if (size_bytes > FGRAPH_MAX_DATA_SIZE) 350 return NULL; 351 352 /* Convert the data size to number of longs. */ 353 data_size = (size_bytes + sizeof(long) - 1) >> (sizeof(long) == 4 ? 2 : 3); 354 355 val = get_fgraph_entry(current, curr_ret_stack - 1); 356 data = ¤t->ret_stack[curr_ret_stack]; 357 358 curr_ret_stack += data_size + 1; 359 if (unlikely(curr_ret_stack >= SHADOW_STACK_MAX_OFFSET)) 360 return NULL; 361 362 val = make_data_type_val(idx, data_size, __get_offset(val) + data_size + 1); 363 364 /* Set the last word to be reserved */ 365 current->ret_stack[curr_ret_stack - 1] = val; 366 367 /* Make sure interrupts see this */ 368 barrier(); 369 current->curr_ret_stack = curr_ret_stack; 370 /* Again sync with interrupts, and reset reserve */ 371 current->ret_stack[curr_ret_stack - 1] = val; 372 373 return data; 374 } 375 376 /** 377 * fgraph_retrieve_data - Retrieve stored data from fgraph_reserve_data() 378 * @idx: the index of fgraph_array (fgraph_ops::idx) 379 * @size_bytes: pointer to retrieved data size. 380 * 381 * This is to be called by a fgraph_ops retfunc(), to retrieve data that 382 * was stored by the fgraph_ops entryfunc() on the function entry. 383 * That is, this will retrieve the data that was reserved on the 384 * entry of the function that corresponds to the exit of the function 385 * that the fgraph_ops retfunc() is called on. 386 * 387 * Returns: The stored data from fgraph_reserve_data() called by the 388 * matching entryfunc() for the retfunc() this is called from. 389 * Or NULL if there was nothing stored. 390 */ 391 void *fgraph_retrieve_data(int idx, int *size_bytes) 392 { 393 int offset = current->curr_ret_stack - 1; 394 unsigned long val; 395 396 val = get_fgraph_entry(current, offset); 397 while (__get_type(val) == FGRAPH_TYPE_DATA) { 398 if (__get_data_index(val) == idx) 399 goto found; 400 offset -= __get_data_size(val) + 1; 401 val = get_fgraph_entry(current, offset); 402 } 403 return NULL; 404 found: 405 if (size_bytes) 406 *size_bytes = __get_data_size(val) * sizeof(long); 407 return get_data_type_data(current, offset); 408 } 409 410 /** 411 * fgraph_get_task_var - retrieve a task specific state variable 412 * @gops: The ftrace_ops that owns the task specific variable 413 * 414 * Every registered fgraph_ops has a task state variable 415 * reserved on the task's ret_stack. This function returns the 416 * address to that variable. 417 * 418 * Returns the address to the fgraph_ops @gops tasks specific 419 * unsigned long variable. 420 */ 421 unsigned long *fgraph_get_task_var(struct fgraph_ops *gops) 422 { 423 return ret_stack_get_task_var(current, gops->idx); 424 } 425 426 /* 427 * @offset: The offset into @t->ret_stack to find the ret_stack entry 428 * @frame_offset: Where to place the offset into @t->ret_stack of that entry 429 * 430 * Returns a pointer to the previous ret_stack below @offset or NULL 431 * when it reaches the bottom of the stack. 432 * 433 * Calling this with: 434 * 435 * offset = task->curr_ret_stack; 436 * do { 437 * ret_stack = get_ret_stack(task, offset, &offset); 438 * } while (ret_stack); 439 * 440 * Will iterate through all the ret_stack entries from curr_ret_stack 441 * down to the first one. 442 */ 443 static inline struct ftrace_ret_stack * 444 get_ret_stack(struct task_struct *t, int offset, int *frame_offset) 445 { 446 int offs; 447 448 BUILD_BUG_ON(FGRAPH_FRAME_SIZE % sizeof(long)); 449 450 if (unlikely(offset <= 0)) 451 return NULL; 452 453 offs = get_frame_offset(t, --offset); 454 if (WARN_ON_ONCE(offs <= 0 || offs > offset)) 455 return NULL; 456 457 offset -= offs; 458 459 *frame_offset = offset; 460 return RET_STACK(t, offset); 461 } 462 463 /* Both enabled by default (can be cleared by function_graph tracer flags */ 464 static bool fgraph_sleep_time = true; 465 466 #ifdef CONFIG_DYNAMIC_FTRACE 467 /* 468 * archs can override this function if they must do something 469 * to enable hook for graph tracer. 470 */ 471 int __weak ftrace_enable_ftrace_graph_caller(void) 472 { 473 return 0; 474 } 475 476 /* 477 * archs can override this function if they must do something 478 * to disable hook for graph tracer. 479 */ 480 int __weak ftrace_disable_ftrace_graph_caller(void) 481 { 482 return 0; 483 } 484 #endif 485 486 int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace, 487 struct fgraph_ops *gops) 488 { 489 return 0; 490 } 491 492 static void ftrace_graph_ret_stub(struct ftrace_graph_ret *trace, 493 struct fgraph_ops *gops) 494 { 495 } 496 497 static struct fgraph_ops fgraph_stub = { 498 .entryfunc = ftrace_graph_entry_stub, 499 .retfunc = ftrace_graph_ret_stub, 500 }; 501 502 static struct fgraph_ops *fgraph_direct_gops = &fgraph_stub; 503 DEFINE_STATIC_CALL(fgraph_func, ftrace_graph_entry_stub); 504 DEFINE_STATIC_CALL(fgraph_retfunc, ftrace_graph_ret_stub); 505 static DEFINE_STATIC_KEY_TRUE(fgraph_do_direct); 506 507 /** 508 * ftrace_graph_stop - set to permanently disable function graph tracing 509 * 510 * In case of an error int function graph tracing, this is called 511 * to try to keep function graph tracing from causing any more harm. 512 * Usually this is pretty severe and this is called to try to at least 513 * get a warning out to the user. 514 */ 515 void ftrace_graph_stop(void) 516 { 517 static_branch_enable(&kill_ftrace_graph); 518 } 519 520 /* Add a function return address to the trace stack on thread info.*/ 521 static int 522 ftrace_push_return_trace(unsigned long ret, unsigned long func, 523 unsigned long frame_pointer, unsigned long *retp, 524 int fgraph_idx) 525 { 526 struct ftrace_ret_stack *ret_stack; 527 unsigned long long calltime; 528 unsigned long val; 529 int offset; 530 531 if (unlikely(ftrace_graph_is_dead())) 532 return -EBUSY; 533 534 if (!current->ret_stack) 535 return -EBUSY; 536 537 BUILD_BUG_ON(SHADOW_STACK_SIZE % sizeof(long)); 538 539 /* Set val to "reserved" with the delta to the new fgraph frame */ 540 val = (FGRAPH_TYPE_RESERVED << FGRAPH_TYPE_SHIFT) | FGRAPH_FRAME_OFFSET; 541 542 /* 543 * We must make sure the ret_stack is tested before we read 544 * anything else. 545 */ 546 smp_rmb(); 547 548 /* 549 * Check if there's room on the shadow stack to fit a fraph frame 550 * and a bitmap word. 551 */ 552 if (current->curr_ret_stack + FGRAPH_FRAME_OFFSET + 1 >= SHADOW_STACK_MAX_OFFSET) { 553 atomic_inc(¤t->trace_overrun); 554 return -EBUSY; 555 } 556 557 calltime = trace_clock_local(); 558 559 offset = READ_ONCE(current->curr_ret_stack); 560 ret_stack = RET_STACK(current, offset); 561 offset += FGRAPH_FRAME_OFFSET; 562 563 /* ret offset = FGRAPH_FRAME_OFFSET ; type = reserved */ 564 current->ret_stack[offset] = val; 565 ret_stack->ret = ret; 566 /* 567 * The unwinders expect curr_ret_stack to point to either zero 568 * or an offset where to find the next ret_stack. Even though the 569 * ret stack might be bogus, we want to write the ret and the 570 * offset to find the ret_stack before we increment the stack point. 571 * If an interrupt comes in now before we increment the curr_ret_stack 572 * it may blow away what we wrote. But that's fine, because the 573 * offset will still be correct (even though the 'ret' won't be). 574 * What we worry about is the offset being correct after we increment 575 * the curr_ret_stack and before we update that offset, as if an 576 * interrupt comes in and does an unwind stack dump, it will need 577 * at least a correct offset! 578 */ 579 barrier(); 580 WRITE_ONCE(current->curr_ret_stack, offset + 1); 581 /* 582 * This next barrier is to ensure that an interrupt coming in 583 * will not corrupt what we are about to write. 584 */ 585 barrier(); 586 587 /* Still keep it reserved even if an interrupt came in */ 588 current->ret_stack[offset] = val; 589 590 ret_stack->ret = ret; 591 ret_stack->func = func; 592 ret_stack->calltime = calltime; 593 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST 594 ret_stack->fp = frame_pointer; 595 #endif 596 ret_stack->retp = retp; 597 return offset; 598 } 599 600 /* 601 * Not all archs define MCOUNT_INSN_SIZE which is used to look for direct 602 * functions. But those archs currently don't support direct functions 603 * anyway, and ftrace_find_rec_direct() is just a stub for them. 604 * Define MCOUNT_INSN_SIZE to keep those archs compiling. 605 */ 606 #ifndef MCOUNT_INSN_SIZE 607 /* Make sure this only works without direct calls */ 608 # ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS 609 # error MCOUNT_INSN_SIZE not defined with direct calls enabled 610 # endif 611 # define MCOUNT_INSN_SIZE 0 612 #endif 613 614 /* If the caller does not use ftrace, call this function. */ 615 int function_graph_enter(unsigned long ret, unsigned long func, 616 unsigned long frame_pointer, unsigned long *retp) 617 { 618 struct ftrace_graph_ent trace; 619 unsigned long bitmap = 0; 620 int offset; 621 int i; 622 623 trace.func = func; 624 trace.depth = ++current->curr_ret_depth; 625 626 offset = ftrace_push_return_trace(ret, func, frame_pointer, retp, 0); 627 if (offset < 0) 628 goto out; 629 630 #ifdef CONFIG_HAVE_STATIC_CALL 631 if (static_branch_likely(&fgraph_do_direct)) { 632 int save_curr_ret_stack = current->curr_ret_stack; 633 634 if (static_call(fgraph_func)(&trace, fgraph_direct_gops)) 635 bitmap |= BIT(fgraph_direct_gops->idx); 636 else 637 /* Clear out any saved storage */ 638 current->curr_ret_stack = save_curr_ret_stack; 639 } else 640 #endif 641 { 642 for_each_set_bit(i, &fgraph_array_bitmask, 643 sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) { 644 struct fgraph_ops *gops = READ_ONCE(fgraph_array[i]); 645 int save_curr_ret_stack; 646 647 if (gops == &fgraph_stub) 648 continue; 649 650 save_curr_ret_stack = current->curr_ret_stack; 651 if (ftrace_ops_test(&gops->ops, func, NULL) && 652 gops->entryfunc(&trace, gops)) 653 bitmap |= BIT(i); 654 else 655 /* Clear out any saved storage */ 656 current->curr_ret_stack = save_curr_ret_stack; 657 } 658 } 659 660 if (!bitmap) 661 goto out_ret; 662 663 /* 664 * Since this function uses fgraph_idx = 0 as a tail-call checking 665 * flag, set that bit always. 666 */ 667 set_bitmap(current, offset, bitmap | BIT(0)); 668 669 return 0; 670 out_ret: 671 current->curr_ret_stack -= FGRAPH_FRAME_OFFSET + 1; 672 out: 673 current->curr_ret_depth--; 674 return -EBUSY; 675 } 676 677 /* Retrieve a function return address to the trace stack on thread info.*/ 678 static struct ftrace_ret_stack * 679 ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret, 680 unsigned long frame_pointer, int *offset) 681 { 682 struct ftrace_ret_stack *ret_stack; 683 684 ret_stack = get_ret_stack(current, current->curr_ret_stack, offset); 685 686 if (unlikely(!ret_stack)) { 687 ftrace_graph_stop(); 688 WARN(1, "Bad function graph ret_stack pointer: %d", 689 current->curr_ret_stack); 690 /* Might as well panic, otherwise we have no where to go */ 691 *ret = (unsigned long)panic; 692 return NULL; 693 } 694 695 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST 696 /* 697 * The arch may choose to record the frame pointer used 698 * and check it here to make sure that it is what we expect it 699 * to be. If gcc does not set the place holder of the return 700 * address in the frame pointer, and does a copy instead, then 701 * the function graph trace will fail. This test detects this 702 * case. 703 * 704 * Currently, x86_32 with optimize for size (-Os) makes the latest 705 * gcc do the above. 706 * 707 * Note, -mfentry does not use frame pointers, and this test 708 * is not needed if CC_USING_FENTRY is set. 709 */ 710 if (unlikely(ret_stack->fp != frame_pointer)) { 711 ftrace_graph_stop(); 712 WARN(1, "Bad frame pointer: expected %lx, received %lx\n" 713 " from func %ps return to %lx\n", 714 ret_stack->fp, 715 frame_pointer, 716 (void *)ret_stack->func, 717 ret_stack->ret); 718 *ret = (unsigned long)panic; 719 return NULL; 720 } 721 #endif 722 723 *offset += FGRAPH_FRAME_OFFSET; 724 *ret = ret_stack->ret; 725 trace->func = ret_stack->func; 726 trace->calltime = ret_stack->calltime; 727 trace->overrun = atomic_read(¤t->trace_overrun); 728 trace->depth = current->curr_ret_depth; 729 /* 730 * We still want to trace interrupts coming in if 731 * max_depth is set to 1. Make sure the decrement is 732 * seen before ftrace_graph_return. 733 */ 734 barrier(); 735 736 return ret_stack; 737 } 738 739 /* 740 * Hibernation protection. 741 * The state of the current task is too much unstable during 742 * suspend/restore to disk. We want to protect against that. 743 */ 744 static int 745 ftrace_suspend_notifier_call(struct notifier_block *bl, unsigned long state, 746 void *unused) 747 { 748 switch (state) { 749 case PM_HIBERNATION_PREPARE: 750 pause_graph_tracing(); 751 break; 752 753 case PM_POST_HIBERNATION: 754 unpause_graph_tracing(); 755 break; 756 } 757 return NOTIFY_DONE; 758 } 759 760 static struct notifier_block ftrace_suspend_notifier = { 761 .notifier_call = ftrace_suspend_notifier_call, 762 }; 763 764 /* fgraph_ret_regs is not defined without CONFIG_FUNCTION_GRAPH_RETVAL */ 765 struct fgraph_ret_regs; 766 767 /* 768 * Send the trace to the ring-buffer. 769 * @return the original return address. 770 */ 771 static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs, 772 unsigned long frame_pointer) 773 { 774 struct ftrace_ret_stack *ret_stack; 775 struct ftrace_graph_ret trace; 776 unsigned long bitmap; 777 unsigned long ret; 778 int offset; 779 int i; 780 781 ret_stack = ftrace_pop_return_trace(&trace, &ret, frame_pointer, &offset); 782 783 if (unlikely(!ret_stack)) { 784 ftrace_graph_stop(); 785 WARN_ON(1); 786 /* Might as well panic. What else to do? */ 787 return (unsigned long)panic; 788 } 789 790 trace.rettime = trace_clock_local(); 791 #ifdef CONFIG_FUNCTION_GRAPH_RETVAL 792 trace.retval = fgraph_ret_regs_return_value(ret_regs); 793 #endif 794 795 bitmap = get_bitmap_bits(current, offset); 796 797 #ifdef CONFIG_HAVE_STATIC_CALL 798 if (static_branch_likely(&fgraph_do_direct)) { 799 if (test_bit(fgraph_direct_gops->idx, &bitmap)) 800 static_call(fgraph_retfunc)(&trace, fgraph_direct_gops); 801 } else 802 #endif 803 { 804 for_each_set_bit(i, &bitmap, sizeof(bitmap) * BITS_PER_BYTE) { 805 struct fgraph_ops *gops = fgraph_array[i]; 806 807 if (gops == &fgraph_stub) 808 continue; 809 810 gops->retfunc(&trace, gops); 811 } 812 } 813 814 /* 815 * The ftrace_graph_return() may still access the current 816 * ret_stack structure, we need to make sure the update of 817 * curr_ret_stack is after that. 818 */ 819 barrier(); 820 current->curr_ret_stack = offset - FGRAPH_FRAME_OFFSET; 821 822 current->curr_ret_depth--; 823 return ret; 824 } 825 826 /* 827 * After all architecures have selected HAVE_FUNCTION_GRAPH_RETVAL, we can 828 * leave only ftrace_return_to_handler(ret_regs). 829 */ 830 #ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL 831 unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs) 832 { 833 return __ftrace_return_to_handler(ret_regs, 834 fgraph_ret_regs_frame_pointer(ret_regs)); 835 } 836 #else 837 unsigned long ftrace_return_to_handler(unsigned long frame_pointer) 838 { 839 return __ftrace_return_to_handler(NULL, frame_pointer); 840 } 841 #endif 842 843 /** 844 * ftrace_graph_get_ret_stack - return the entry of the shadow stack 845 * @task: The task to read the shadow stack from. 846 * @idx: Index down the shadow stack 847 * 848 * Return the ret_struct on the shadow stack of the @task at the 849 * call graph at @idx starting with zero. If @idx is zero, it 850 * will return the last saved ret_stack entry. If it is greater than 851 * zero, it will return the corresponding ret_stack for the depth 852 * of saved return addresses. 853 */ 854 struct ftrace_ret_stack * 855 ftrace_graph_get_ret_stack(struct task_struct *task, int idx) 856 { 857 struct ftrace_ret_stack *ret_stack = NULL; 858 int offset = task->curr_ret_stack; 859 860 if (offset < 0) 861 return NULL; 862 863 do { 864 ret_stack = get_ret_stack(task, offset, &offset); 865 } while (ret_stack && --idx >= 0); 866 867 return ret_stack; 868 } 869 870 /** 871 * ftrace_graph_ret_addr - return the original value of the return address 872 * @task: The task the unwinder is being executed on 873 * @idx: An initialized pointer to the next stack index to use 874 * @ret: The current return address (likely pointing to return_handler) 875 * @retp: The address on the stack of the current return location 876 * 877 * This function can be called by stack unwinding code to convert a found stack 878 * return address (@ret) to its original value, in case the function graph 879 * tracer has modified it to be 'return_to_handler'. If the address hasn't 880 * been modified, the unchanged value of @ret is returned. 881 * 882 * @idx holds the last index used to know where to start from. It should be 883 * initialized to zero for the first iteration as that will mean to start 884 * at the top of the shadow stack. If the location is found, this pointer 885 * will be assigned that location so that if called again, it will continue 886 * where it left off. 887 * 888 * @retp is a pointer to the return address on the stack. 889 */ 890 unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx, 891 unsigned long ret, unsigned long *retp) 892 { 893 struct ftrace_ret_stack *ret_stack; 894 unsigned long return_handler = (unsigned long)dereference_kernel_function_descriptor(return_to_handler); 895 int i = task->curr_ret_stack; 896 897 if (ret != return_handler) 898 return ret; 899 900 if (!idx) 901 return ret; 902 903 i = *idx ? : task->curr_ret_stack; 904 while (i > 0) { 905 ret_stack = get_ret_stack(task, i, &i); 906 if (!ret_stack) 907 break; 908 /* 909 * For the tail-call, there would be 2 or more ftrace_ret_stacks on 910 * the ret_stack, which records "return_to_handler" as the return 911 * address except for the last one. 912 * But on the real stack, there should be 1 entry because tail-call 913 * reuses the return address on the stack and jump to the next function. 914 * Thus we will continue to find real return address. 915 */ 916 if (ret_stack->retp == retp && 917 ret_stack->ret != return_handler) { 918 *idx = i; 919 return ret_stack->ret; 920 } 921 } 922 923 return ret; 924 } 925 926 static struct ftrace_ops graph_ops = { 927 .func = ftrace_graph_func, 928 .flags = FTRACE_OPS_GRAPH_STUB, 929 #ifdef FTRACE_GRAPH_TRAMP_ADDR 930 .trampoline = FTRACE_GRAPH_TRAMP_ADDR, 931 /* trampoline_size is only needed for dynamically allocated tramps */ 932 #endif 933 }; 934 935 void fgraph_init_ops(struct ftrace_ops *dst_ops, 936 struct ftrace_ops *src_ops) 937 { 938 dst_ops->flags = FTRACE_OPS_FL_PID | FTRACE_OPS_GRAPH_STUB; 939 940 #ifdef CONFIG_DYNAMIC_FTRACE 941 if (src_ops) { 942 dst_ops->func_hash = &src_ops->local_hash; 943 mutex_init(&dst_ops->local_hash.regex_lock); 944 INIT_LIST_HEAD(&dst_ops->subop_list); 945 dst_ops->flags |= FTRACE_OPS_FL_INITIALIZED; 946 } 947 #endif 948 } 949 950 void ftrace_graph_sleep_time_control(bool enable) 951 { 952 fgraph_sleep_time = enable; 953 } 954 955 /* 956 * Simply points to ftrace_stub, but with the proper protocol. 957 * Defined by the linker script in linux/vmlinux.lds.h 958 */ 959 void ftrace_stub_graph(struct ftrace_graph_ret *trace, struct fgraph_ops *gops); 960 961 /* The callbacks that hook a function */ 962 trace_func_graph_ret_t ftrace_graph_return = ftrace_stub_graph; 963 trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub; 964 965 /* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */ 966 static int alloc_retstack_tasklist(unsigned long **ret_stack_list) 967 { 968 int i; 969 int ret = 0; 970 int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE; 971 struct task_struct *g, *t; 972 973 for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) { 974 ret_stack_list[i] = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL); 975 if (!ret_stack_list[i]) { 976 start = 0; 977 end = i; 978 ret = -ENOMEM; 979 goto free; 980 } 981 } 982 983 rcu_read_lock(); 984 for_each_process_thread(g, t) { 985 if (start == end) { 986 ret = -EAGAIN; 987 goto unlock; 988 } 989 990 if (t->ret_stack == NULL) { 991 atomic_set(&t->trace_overrun, 0); 992 ret_stack_init_task_vars(ret_stack_list[start]); 993 t->curr_ret_stack = 0; 994 t->curr_ret_depth = -1; 995 /* Make sure the tasks see the 0 first: */ 996 smp_wmb(); 997 t->ret_stack = ret_stack_list[start++]; 998 } 999 } 1000 1001 unlock: 1002 rcu_read_unlock(); 1003 free: 1004 for (i = start; i < end; i++) 1005 kfree(ret_stack_list[i]); 1006 return ret; 1007 } 1008 1009 static void 1010 ftrace_graph_probe_sched_switch(void *ignore, bool preempt, 1011 struct task_struct *prev, 1012 struct task_struct *next, 1013 unsigned int prev_state) 1014 { 1015 struct ftrace_ret_stack *ret_stack; 1016 unsigned long long timestamp; 1017 int offset; 1018 1019 /* 1020 * Does the user want to count the time a function was asleep. 1021 * If so, do not update the time stamps. 1022 */ 1023 if (fgraph_sleep_time) 1024 return; 1025 1026 timestamp = trace_clock_local(); 1027 1028 prev->ftrace_timestamp = timestamp; 1029 1030 /* only process tasks that we timestamped */ 1031 if (!next->ftrace_timestamp) 1032 return; 1033 1034 /* 1035 * Update all the counters in next to make up for the 1036 * time next was sleeping. 1037 */ 1038 timestamp -= next->ftrace_timestamp; 1039 1040 for (offset = next->curr_ret_stack; offset > 0; ) { 1041 ret_stack = get_ret_stack(next, offset, &offset); 1042 if (ret_stack) 1043 ret_stack->calltime += timestamp; 1044 } 1045 } 1046 1047 static DEFINE_PER_CPU(unsigned long *, idle_ret_stack); 1048 1049 static void 1050 graph_init_task(struct task_struct *t, unsigned long *ret_stack) 1051 { 1052 atomic_set(&t->trace_overrun, 0); 1053 ret_stack_init_task_vars(ret_stack); 1054 t->ftrace_timestamp = 0; 1055 t->curr_ret_stack = 0; 1056 t->curr_ret_depth = -1; 1057 /* make curr_ret_stack visible before we add the ret_stack */ 1058 smp_wmb(); 1059 t->ret_stack = ret_stack; 1060 } 1061 1062 /* 1063 * Allocate a return stack for the idle task. May be the first 1064 * time through, or it may be done by CPU hotplug online. 1065 */ 1066 void ftrace_graph_init_idle_task(struct task_struct *t, int cpu) 1067 { 1068 t->curr_ret_stack = 0; 1069 t->curr_ret_depth = -1; 1070 /* 1071 * The idle task has no parent, it either has its own 1072 * stack or no stack at all. 1073 */ 1074 if (t->ret_stack) 1075 WARN_ON(t->ret_stack != per_cpu(idle_ret_stack, cpu)); 1076 1077 if (ftrace_graph_active) { 1078 unsigned long *ret_stack; 1079 1080 ret_stack = per_cpu(idle_ret_stack, cpu); 1081 if (!ret_stack) { 1082 ret_stack = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL); 1083 if (!ret_stack) 1084 return; 1085 per_cpu(idle_ret_stack, cpu) = ret_stack; 1086 } 1087 graph_init_task(t, ret_stack); 1088 } 1089 } 1090 1091 /* Allocate a return stack for newly created task */ 1092 void ftrace_graph_init_task(struct task_struct *t) 1093 { 1094 /* Make sure we do not use the parent ret_stack */ 1095 t->ret_stack = NULL; 1096 t->curr_ret_stack = 0; 1097 t->curr_ret_depth = -1; 1098 1099 if (ftrace_graph_active) { 1100 unsigned long *ret_stack; 1101 1102 ret_stack = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL); 1103 if (!ret_stack) 1104 return; 1105 graph_init_task(t, ret_stack); 1106 } 1107 } 1108 1109 void ftrace_graph_exit_task(struct task_struct *t) 1110 { 1111 unsigned long *ret_stack = t->ret_stack; 1112 1113 t->ret_stack = NULL; 1114 /* NULL must become visible to IRQs before we free it: */ 1115 barrier(); 1116 1117 kfree(ret_stack); 1118 } 1119 1120 #ifdef CONFIG_DYNAMIC_FTRACE 1121 static int fgraph_pid_func(struct ftrace_graph_ent *trace, 1122 struct fgraph_ops *gops) 1123 { 1124 struct trace_array *tr = gops->ops.private; 1125 int pid; 1126 1127 if (tr) { 1128 pid = this_cpu_read(tr->array_buffer.data->ftrace_ignore_pid); 1129 if (pid == FTRACE_PID_IGNORE) 1130 return 0; 1131 if (pid != FTRACE_PID_TRACE && 1132 pid != current->pid) 1133 return 0; 1134 } 1135 1136 return gops->saved_func(trace, gops); 1137 } 1138 1139 void fgraph_update_pid_func(void) 1140 { 1141 struct fgraph_ops *gops; 1142 struct ftrace_ops *op; 1143 1144 if (!(graph_ops.flags & FTRACE_OPS_FL_INITIALIZED)) 1145 return; 1146 1147 list_for_each_entry(op, &graph_ops.subop_list, list) { 1148 if (op->flags & FTRACE_OPS_FL_PID) { 1149 gops = container_of(op, struct fgraph_ops, ops); 1150 gops->entryfunc = ftrace_pids_enabled(op) ? 1151 fgraph_pid_func : gops->saved_func; 1152 if (ftrace_graph_active == 1) 1153 static_call_update(fgraph_func, gops->entryfunc); 1154 } 1155 } 1156 } 1157 #endif 1158 1159 /* Allocate a return stack for each task */ 1160 static int start_graph_tracing(void) 1161 { 1162 unsigned long **ret_stack_list; 1163 int ret; 1164 1165 ret_stack_list = kcalloc(FTRACE_RETSTACK_ALLOC_SIZE, 1166 sizeof(*ret_stack_list), GFP_KERNEL); 1167 1168 if (!ret_stack_list) 1169 return -ENOMEM; 1170 1171 do { 1172 ret = alloc_retstack_tasklist(ret_stack_list); 1173 } while (ret == -EAGAIN); 1174 1175 if (!ret) { 1176 ret = register_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL); 1177 if (ret) 1178 pr_info("ftrace_graph: Couldn't activate tracepoint" 1179 " probe to kernel_sched_switch\n"); 1180 } 1181 1182 kfree(ret_stack_list); 1183 return ret; 1184 } 1185 1186 static void init_task_vars(int idx) 1187 { 1188 struct task_struct *g, *t; 1189 int cpu; 1190 1191 for_each_online_cpu(cpu) { 1192 if (idle_task(cpu)->ret_stack) 1193 ret_stack_set_task_var(idle_task(cpu), idx, 0); 1194 } 1195 1196 read_lock(&tasklist_lock); 1197 for_each_process_thread(g, t) { 1198 if (t->ret_stack) 1199 ret_stack_set_task_var(t, idx, 0); 1200 } 1201 read_unlock(&tasklist_lock); 1202 } 1203 1204 static void ftrace_graph_enable_direct(bool enable_branch, struct fgraph_ops *gops) 1205 { 1206 trace_func_graph_ent_t func = NULL; 1207 trace_func_graph_ret_t retfunc = NULL; 1208 int i; 1209 1210 if (gops) { 1211 func = gops->entryfunc; 1212 retfunc = gops->retfunc; 1213 fgraph_direct_gops = gops; 1214 } else { 1215 for_each_set_bit(i, &fgraph_array_bitmask, 1216 sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) { 1217 func = fgraph_array[i]->entryfunc; 1218 retfunc = fgraph_array[i]->retfunc; 1219 fgraph_direct_gops = fgraph_array[i]; 1220 } 1221 } 1222 if (WARN_ON_ONCE(!func)) 1223 return; 1224 1225 static_call_update(fgraph_func, func); 1226 static_call_update(fgraph_retfunc, retfunc); 1227 if (enable_branch) 1228 static_branch_disable(&fgraph_do_direct); 1229 } 1230 1231 static void ftrace_graph_disable_direct(bool disable_branch) 1232 { 1233 if (disable_branch) 1234 static_branch_disable(&fgraph_do_direct); 1235 static_call_update(fgraph_func, ftrace_graph_entry_stub); 1236 static_call_update(fgraph_retfunc, ftrace_graph_ret_stub); 1237 fgraph_direct_gops = &fgraph_stub; 1238 } 1239 1240 /* The cpu_boot init_task->ret_stack will never be freed */ 1241 static int fgraph_cpu_init(unsigned int cpu) 1242 { 1243 if (!idle_task(cpu)->ret_stack) 1244 ftrace_graph_init_idle_task(idle_task(cpu), cpu); 1245 return 0; 1246 } 1247 1248 int register_ftrace_graph(struct fgraph_ops *gops) 1249 { 1250 static bool fgraph_initialized; 1251 int command = 0; 1252 int ret = 0; 1253 int i = -1; 1254 1255 guard(mutex)(&ftrace_lock); 1256 1257 if (!fgraph_initialized) { 1258 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "fgraph:online", 1259 fgraph_cpu_init, NULL); 1260 if (ret < 0) { 1261 pr_warn("fgraph: Error to init cpu hotplug support\n"); 1262 return ret; 1263 } 1264 fgraph_initialized = true; 1265 ret = 0; 1266 } 1267 1268 if (!fgraph_array[0]) { 1269 /* The array must always have real data on it */ 1270 for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) 1271 fgraph_array[i] = &fgraph_stub; 1272 fgraph_lru_init(); 1273 } 1274 1275 i = fgraph_lru_alloc_index(); 1276 if (i < 0 || WARN_ON_ONCE(fgraph_array[i] != &fgraph_stub)) 1277 return -ENOSPC; 1278 gops->idx = i; 1279 1280 ftrace_graph_active++; 1281 1282 if (ftrace_graph_active == 2) 1283 ftrace_graph_disable_direct(true); 1284 1285 if (ftrace_graph_active == 1) { 1286 ftrace_graph_enable_direct(false, gops); 1287 register_pm_notifier(&ftrace_suspend_notifier); 1288 ret = start_graph_tracing(); 1289 if (ret) 1290 goto error; 1291 /* 1292 * Some archs just test to see if these are not 1293 * the default function 1294 */ 1295 ftrace_graph_return = return_run; 1296 ftrace_graph_entry = entry_run; 1297 command = FTRACE_START_FUNC_RET; 1298 } else { 1299 init_task_vars(gops->idx); 1300 } 1301 /* Always save the function, and reset at unregistering */ 1302 gops->saved_func = gops->entryfunc; 1303 1304 ret = ftrace_startup_subops(&graph_ops, &gops->ops, command); 1305 if (!ret) 1306 fgraph_array[i] = gops; 1307 1308 error: 1309 if (ret) { 1310 ftrace_graph_active--; 1311 gops->saved_func = NULL; 1312 fgraph_lru_release_index(i); 1313 } 1314 return ret; 1315 } 1316 1317 void unregister_ftrace_graph(struct fgraph_ops *gops) 1318 { 1319 int command = 0; 1320 1321 mutex_lock(&ftrace_lock); 1322 1323 if (unlikely(!ftrace_graph_active)) 1324 goto out; 1325 1326 if (unlikely(gops->idx < 0 || gops->idx >= FGRAPH_ARRAY_SIZE || 1327 fgraph_array[gops->idx] != gops)) 1328 goto out; 1329 1330 if (fgraph_lru_release_index(gops->idx) < 0) 1331 goto out; 1332 1333 fgraph_array[gops->idx] = &fgraph_stub; 1334 1335 ftrace_graph_active--; 1336 1337 if (!ftrace_graph_active) 1338 command = FTRACE_STOP_FUNC_RET; 1339 1340 ftrace_shutdown_subops(&graph_ops, &gops->ops, command); 1341 1342 if (ftrace_graph_active == 1) 1343 ftrace_graph_enable_direct(true, NULL); 1344 else if (!ftrace_graph_active) 1345 ftrace_graph_disable_direct(false); 1346 1347 if (!ftrace_graph_active) { 1348 ftrace_graph_return = ftrace_stub_graph; 1349 ftrace_graph_entry = ftrace_graph_entry_stub; 1350 unregister_pm_notifier(&ftrace_suspend_notifier); 1351 unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL); 1352 } 1353 out: 1354 gops->saved_func = NULL; 1355 mutex_unlock(&ftrace_lock); 1356 } 1357