1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Infrastructure to took into function calls and returns. 4 * Copyright (c) 2008-2009 Frederic Weisbecker <[email protected]> 5 * Mostly borrowed from function tracer which 6 * is Copyright (c) Steven Rostedt <[email protected]> 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 struct fgraph_extras *extras) 295 { 296 return 0; 297 } 298 299 /* ftrace_graph_return set to this to tell some archs to run function graph */ 300 static void return_run(struct ftrace_graph_ret *trace, struct fgraph_ops *ops) 301 { 302 } 303 304 static void ret_stack_set_task_var(struct task_struct *t, int idx, long val) 305 { 306 unsigned long *gvals = SHADOW_STACK_TASK_VARS(t->ret_stack); 307 308 gvals[idx] = val; 309 } 310 311 static unsigned long * 312 ret_stack_get_task_var(struct task_struct *t, int idx) 313 { 314 unsigned long *gvals = SHADOW_STACK_TASK_VARS(t->ret_stack); 315 316 return &gvals[idx]; 317 } 318 319 static void ret_stack_init_task_vars(unsigned long *ret_stack) 320 { 321 unsigned long *gvals = SHADOW_STACK_TASK_VARS(ret_stack); 322 323 memset(gvals, 0, sizeof(*gvals) * FGRAPH_ARRAY_SIZE); 324 } 325 326 /** 327 * fgraph_reserve_data - Reserve storage on the task's ret_stack 328 * @idx: The index of fgraph_array 329 * @size_bytes: The size in bytes to reserve 330 * 331 * Reserves space of up to FGRAPH_MAX_DATA_SIZE bytes on the 332 * task's ret_stack shadow stack, for a given fgraph_ops during 333 * the entryfunc() call. If entryfunc() returns zero, the storage 334 * is discarded. An entryfunc() can only call this once per iteration. 335 * The fgraph_ops retfunc() can retrieve this stored data with 336 * fgraph_retrieve_data(). 337 * 338 * Returns: On success, a pointer to the data on the stack. 339 * Otherwise, NULL if there's not enough space left on the 340 * ret_stack for the data, or if fgraph_reserve_data() was called 341 * more than once for a single entryfunc() call. 342 */ 343 void *fgraph_reserve_data(int idx, int size_bytes) 344 { 345 unsigned long val; 346 void *data; 347 int curr_ret_stack = current->curr_ret_stack; 348 int data_size; 349 350 if (size_bytes > FGRAPH_MAX_DATA_SIZE) 351 return NULL; 352 353 /* Convert the data size to number of longs. */ 354 data_size = (size_bytes + sizeof(long) - 1) >> (sizeof(long) == 4 ? 2 : 3); 355 356 val = get_fgraph_entry(current, curr_ret_stack - 1); 357 data = ¤t->ret_stack[curr_ret_stack]; 358 359 curr_ret_stack += data_size + 1; 360 if (unlikely(curr_ret_stack >= SHADOW_STACK_MAX_OFFSET)) 361 return NULL; 362 363 val = make_data_type_val(idx, data_size, __get_offset(val) + data_size + 1); 364 365 /* Set the last word to be reserved */ 366 current->ret_stack[curr_ret_stack - 1] = val; 367 368 /* Make sure interrupts see this */ 369 barrier(); 370 current->curr_ret_stack = curr_ret_stack; 371 /* Again sync with interrupts, and reset reserve */ 372 current->ret_stack[curr_ret_stack - 1] = val; 373 374 return data; 375 } 376 377 /** 378 * fgraph_retrieve_data - Retrieve stored data from fgraph_reserve_data() 379 * @idx: the index of fgraph_array (fgraph_ops::idx) 380 * @size_bytes: pointer to retrieved data size. 381 * 382 * This is to be called by a fgraph_ops retfunc(), to retrieve data that 383 * was stored by the fgraph_ops entryfunc() on the function entry. 384 * That is, this will retrieve the data that was reserved on the 385 * entry of the function that corresponds to the exit of the function 386 * that the fgraph_ops retfunc() is called on. 387 * 388 * Returns: The stored data from fgraph_reserve_data() called by the 389 * matching entryfunc() for the retfunc() this is called from. 390 * Or NULL if there was nothing stored. 391 */ 392 void *fgraph_retrieve_data(int idx, int *size_bytes) 393 { 394 return fgraph_retrieve_parent_data(idx, size_bytes, 0); 395 } 396 397 /** 398 * fgraph_get_task_var - retrieve a task specific state variable 399 * @gops: The ftrace_ops that owns the task specific variable 400 * 401 * Every registered fgraph_ops has a task state variable 402 * reserved on the task's ret_stack. This function returns the 403 * address to that variable. 404 * 405 * Returns the address to the fgraph_ops @gops tasks specific 406 * unsigned long variable. 407 */ 408 unsigned long *fgraph_get_task_var(struct fgraph_ops *gops) 409 { 410 return ret_stack_get_task_var(current, gops->idx); 411 } 412 413 /* 414 * @offset: The offset into @t->ret_stack to find the ret_stack entry 415 * @frame_offset: Where to place the offset into @t->ret_stack of that entry 416 * 417 * Returns a pointer to the previous ret_stack below @offset or NULL 418 * when it reaches the bottom of the stack. 419 * 420 * Calling this with: 421 * 422 * offset = task->curr_ret_stack; 423 * do { 424 * ret_stack = get_ret_stack(task, offset, &offset); 425 * } while (ret_stack); 426 * 427 * Will iterate through all the ret_stack entries from curr_ret_stack 428 * down to the first one. 429 */ 430 static inline struct ftrace_ret_stack * 431 get_ret_stack(struct task_struct *t, int offset, int *frame_offset) 432 { 433 int offs; 434 435 BUILD_BUG_ON(FGRAPH_FRAME_SIZE % sizeof(long)); 436 437 if (unlikely(offset <= 0)) 438 return NULL; 439 440 offs = get_frame_offset(t, --offset); 441 if (WARN_ON_ONCE(offs <= 0 || offs > offset)) 442 return NULL; 443 444 offset -= offs; 445 446 *frame_offset = offset; 447 return RET_STACK(t, offset); 448 } 449 450 /** 451 * fgraph_retrieve_parent_data - get data from a parent function 452 * @idx: The index into the fgraph_array (fgraph_ops::idx) 453 * @size_bytes: A pointer to retrieved data size 454 * @depth: The depth to find the parent (0 is the current function) 455 * 456 * This is similar to fgraph_retrieve_data() but can be used to retrieve 457 * data from a parent caller function. 458 * 459 * Return: a pointer to the specified parent data or NULL if not found 460 */ 461 void *fgraph_retrieve_parent_data(int idx, int *size_bytes, int depth) 462 { 463 struct ftrace_ret_stack *ret_stack = NULL; 464 int offset = current->curr_ret_stack; 465 unsigned long val; 466 467 if (offset <= 0) 468 return NULL; 469 470 for (;;) { 471 int next_offset; 472 473 ret_stack = get_ret_stack(current, offset, &next_offset); 474 if (!ret_stack || --depth < 0) 475 break; 476 offset = next_offset; 477 } 478 479 if (!ret_stack) 480 return NULL; 481 482 offset--; 483 484 val = get_fgraph_entry(current, offset); 485 while (__get_type(val) == FGRAPH_TYPE_DATA) { 486 if (__get_data_index(val) == idx) 487 goto found; 488 offset -= __get_data_size(val) + 1; 489 val = get_fgraph_entry(current, offset); 490 } 491 return NULL; 492 found: 493 if (size_bytes) 494 *size_bytes = __get_data_size(val) * sizeof(long); 495 return get_data_type_data(current, offset); 496 } 497 498 /* Both enabled by default (can be cleared by function_graph tracer flags */ 499 bool fgraph_sleep_time = true; 500 501 #ifdef CONFIG_DYNAMIC_FTRACE 502 /* 503 * archs can override this function if they must do something 504 * to enable hook for graph tracer. 505 */ 506 int __weak ftrace_enable_ftrace_graph_caller(void) 507 { 508 return 0; 509 } 510 511 /* 512 * archs can override this function if they must do something 513 * to disable hook for graph tracer. 514 */ 515 int __weak ftrace_disable_ftrace_graph_caller(void) 516 { 517 return 0; 518 } 519 #endif 520 521 int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace, 522 struct fgraph_ops *gops, 523 struct fgraph_extras *extras) 524 { 525 return 0; 526 } 527 528 static void ftrace_graph_ret_stub(struct ftrace_graph_ret *trace, 529 struct fgraph_ops *gops) 530 { 531 } 532 533 static struct fgraph_ops fgraph_stub = { 534 .entryfunc = ftrace_graph_entry_stub, 535 .retfunc = ftrace_graph_ret_stub, 536 }; 537 538 static struct fgraph_ops *fgraph_direct_gops = &fgraph_stub; 539 DEFINE_STATIC_CALL(fgraph_func, ftrace_graph_entry_stub); 540 DEFINE_STATIC_CALL(fgraph_retfunc, ftrace_graph_ret_stub); 541 static DEFINE_STATIC_KEY_TRUE(fgraph_do_direct); 542 543 /** 544 * ftrace_graph_stop - set to permanently disable function graph tracing 545 * 546 * In case of an error int function graph tracing, this is called 547 * to try to keep function graph tracing from causing any more harm. 548 * Usually this is pretty severe and this is called to try to at least 549 * get a warning out to the user. 550 */ 551 void ftrace_graph_stop(void) 552 { 553 static_branch_enable(&kill_ftrace_graph); 554 } 555 556 /* Add a function return address to the trace stack on thread info.*/ 557 static int 558 ftrace_push_return_trace(unsigned long ret, unsigned long func, 559 unsigned long frame_pointer, unsigned long *retp, 560 int fgraph_idx) 561 { 562 struct ftrace_ret_stack *ret_stack; 563 unsigned long val; 564 int offset; 565 566 if (unlikely(ftrace_graph_is_dead())) 567 return -EBUSY; 568 569 if (!current->ret_stack) 570 return -EBUSY; 571 572 BUILD_BUG_ON(SHADOW_STACK_SIZE % sizeof(long)); 573 574 /* Set val to "reserved" with the delta to the new fgraph frame */ 575 val = (FGRAPH_TYPE_RESERVED << FGRAPH_TYPE_SHIFT) | FGRAPH_FRAME_OFFSET; 576 577 /* 578 * We must make sure the ret_stack is tested before we read 579 * anything else. 580 */ 581 smp_rmb(); 582 583 /* 584 * Check if there's room on the shadow stack to fit a fraph frame 585 * and a bitmap word. 586 */ 587 if (current->curr_ret_stack + FGRAPH_FRAME_OFFSET + 1 >= SHADOW_STACK_MAX_OFFSET) { 588 atomic_inc(¤t->trace_overrun); 589 return -EBUSY; 590 } 591 592 offset = READ_ONCE(current->curr_ret_stack); 593 ret_stack = RET_STACK(current, offset); 594 offset += FGRAPH_FRAME_OFFSET; 595 596 /* ret offset = FGRAPH_FRAME_OFFSET ; type = reserved */ 597 current->ret_stack[offset] = val; 598 ret_stack->ret = ret; 599 /* 600 * The unwinders expect curr_ret_stack to point to either zero 601 * or an offset where to find the next ret_stack. Even though the 602 * ret stack might be bogus, we want to write the ret and the 603 * offset to find the ret_stack before we increment the stack point. 604 * If an interrupt comes in now before we increment the curr_ret_stack 605 * it may blow away what we wrote. But that's fine, because the 606 * offset will still be correct (even though the 'ret' won't be). 607 * What we worry about is the offset being correct after we increment 608 * the curr_ret_stack and before we update that offset, as if an 609 * interrupt comes in and does an unwind stack dump, it will need 610 * at least a correct offset! 611 */ 612 barrier(); 613 WRITE_ONCE(current->curr_ret_stack, offset + 1); 614 /* 615 * This next barrier is to ensure that an interrupt coming in 616 * will not corrupt what we are about to write. 617 */ 618 barrier(); 619 620 /* Still keep it reserved even if an interrupt came in */ 621 current->ret_stack[offset] = val; 622 623 ret_stack->ret = ret; 624 ret_stack->func = func; 625 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST 626 ret_stack->fp = frame_pointer; 627 #endif 628 ret_stack->retp = retp; 629 return offset; 630 } 631 632 /* 633 * Not all archs define MCOUNT_INSN_SIZE which is used to look for direct 634 * functions. But those archs currently don't support direct functions 635 * anyway, and ftrace_find_rec_direct() is just a stub for them. 636 * Define MCOUNT_INSN_SIZE to keep those archs compiling. 637 */ 638 #ifndef MCOUNT_INSN_SIZE 639 /* Make sure this only works without direct calls */ 640 # ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS 641 # error MCOUNT_INSN_SIZE not defined with direct calls enabled 642 # endif 643 # define MCOUNT_INSN_SIZE 0 644 #endif 645 646 /* If the caller does not use ftrace, call this function. */ 647 int function_graph_enter(unsigned long ret, unsigned long func, 648 unsigned long frame_pointer, unsigned long *retp) 649 { 650 struct ftrace_graph_ent trace; 651 struct fgraph_extras extras; 652 unsigned long bitmap = 0; 653 int offset; 654 int i; 655 int idx = 0; 656 657 trace.func = func; 658 trace.depth = ++current->curr_ret_depth; 659 660 extras.flags = graph_tracer_flags_get(TRACE_GRAPH_PRINT_RETADDR); 661 if (IS_ENABLED(CONFIG_FUNCTION_GRAPH_RETADDR) 662 && extras.flags & TRACE_GRAPH_PRINT_RETADDR) 663 extras.retaddr = ftrace_graph_ret_addr(current, &idx, ret, retp); 664 665 offset = ftrace_push_return_trace(ret, func, frame_pointer, retp, 0); 666 if (offset < 0) 667 goto out; 668 669 #ifdef CONFIG_HAVE_STATIC_CALL 670 if (static_branch_likely(&fgraph_do_direct)) { 671 int save_curr_ret_stack = current->curr_ret_stack; 672 673 if (static_call(fgraph_func)(&trace, fgraph_direct_gops, &extras)) 674 bitmap |= BIT(fgraph_direct_gops->idx); 675 else 676 /* Clear out any saved storage */ 677 current->curr_ret_stack = save_curr_ret_stack; 678 } else 679 #endif 680 { 681 for_each_set_bit(i, &fgraph_array_bitmask, 682 sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) { 683 struct fgraph_ops *gops = READ_ONCE(fgraph_array[i]); 684 int save_curr_ret_stack; 685 686 if (gops == &fgraph_stub) 687 continue; 688 689 save_curr_ret_stack = current->curr_ret_stack; 690 if (ftrace_ops_test(&gops->ops, func, NULL) && 691 gops->entryfunc(&trace, gops, &extras)) 692 bitmap |= BIT(i); 693 else 694 /* Clear out any saved storage */ 695 current->curr_ret_stack = save_curr_ret_stack; 696 } 697 } 698 699 if (!bitmap) 700 goto out_ret; 701 702 /* 703 * Since this function uses fgraph_idx = 0 as a tail-call checking 704 * flag, set that bit always. 705 */ 706 set_bitmap(current, offset, bitmap | BIT(0)); 707 708 return 0; 709 out_ret: 710 current->curr_ret_stack -= FGRAPH_FRAME_OFFSET + 1; 711 out: 712 current->curr_ret_depth--; 713 return -EBUSY; 714 } 715 716 /* Retrieve a function return address to the trace stack on thread info.*/ 717 static struct ftrace_ret_stack * 718 ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret, 719 unsigned long frame_pointer, int *offset) 720 { 721 struct ftrace_ret_stack *ret_stack; 722 723 ret_stack = get_ret_stack(current, current->curr_ret_stack, offset); 724 725 if (unlikely(!ret_stack)) { 726 ftrace_graph_stop(); 727 WARN(1, "Bad function graph ret_stack pointer: %d", 728 current->curr_ret_stack); 729 /* Might as well panic, otherwise we have no where to go */ 730 *ret = (unsigned long)panic; 731 return NULL; 732 } 733 734 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST 735 /* 736 * The arch may choose to record the frame pointer used 737 * and check it here to make sure that it is what we expect it 738 * to be. If gcc does not set the place holder of the return 739 * address in the frame pointer, and does a copy instead, then 740 * the function graph trace will fail. This test detects this 741 * case. 742 * 743 * Currently, x86_32 with optimize for size (-Os) makes the latest 744 * gcc do the above. 745 * 746 * Note, -mfentry does not use frame pointers, and this test 747 * is not needed if CC_USING_FENTRY is set. 748 */ 749 if (unlikely(ret_stack->fp != frame_pointer)) { 750 ftrace_graph_stop(); 751 WARN(1, "Bad frame pointer: expected %lx, received %lx\n" 752 " from func %ps return to %lx\n", 753 ret_stack->fp, 754 frame_pointer, 755 (void *)ret_stack->func, 756 ret_stack->ret); 757 *ret = (unsigned long)panic; 758 return NULL; 759 } 760 #endif 761 762 *offset += FGRAPH_FRAME_OFFSET; 763 *ret = ret_stack->ret; 764 trace->func = ret_stack->func; 765 trace->overrun = atomic_read(¤t->trace_overrun); 766 trace->depth = current->curr_ret_depth; 767 /* 768 * We still want to trace interrupts coming in if 769 * max_depth is set to 1. Make sure the decrement is 770 * seen before ftrace_graph_return. 771 */ 772 barrier(); 773 774 return ret_stack; 775 } 776 777 /* 778 * Hibernation protection. 779 * The state of the current task is too much unstable during 780 * suspend/restore to disk. We want to protect against that. 781 */ 782 static int 783 ftrace_suspend_notifier_call(struct notifier_block *bl, unsigned long state, 784 void *unused) 785 { 786 switch (state) { 787 case PM_HIBERNATION_PREPARE: 788 pause_graph_tracing(); 789 break; 790 791 case PM_POST_HIBERNATION: 792 unpause_graph_tracing(); 793 break; 794 } 795 return NOTIFY_DONE; 796 } 797 798 static struct notifier_block ftrace_suspend_notifier = { 799 .notifier_call = ftrace_suspend_notifier_call, 800 }; 801 802 /* fgraph_ret_regs is not defined without CONFIG_FUNCTION_GRAPH_RETVAL */ 803 struct fgraph_ret_regs; 804 805 /* 806 * Send the trace to the ring-buffer. 807 * @return the original return address. 808 */ 809 static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs, 810 unsigned long frame_pointer) 811 { 812 struct ftrace_ret_stack *ret_stack; 813 struct ftrace_graph_ret trace; 814 unsigned long bitmap; 815 unsigned long ret; 816 int offset; 817 int i; 818 819 ret_stack = ftrace_pop_return_trace(&trace, &ret, frame_pointer, &offset); 820 821 if (unlikely(!ret_stack)) { 822 ftrace_graph_stop(); 823 WARN_ON(1); 824 /* Might as well panic. What else to do? */ 825 return (unsigned long)panic; 826 } 827 828 trace.rettime = trace_clock_local(); 829 #ifdef CONFIG_FUNCTION_GRAPH_RETVAL 830 trace.retval = fgraph_ret_regs_return_value(ret_regs); 831 #endif 832 833 bitmap = get_bitmap_bits(current, offset); 834 835 #ifdef CONFIG_HAVE_STATIC_CALL 836 if (static_branch_likely(&fgraph_do_direct)) { 837 if (test_bit(fgraph_direct_gops->idx, &bitmap)) 838 static_call(fgraph_retfunc)(&trace, fgraph_direct_gops); 839 } else 840 #endif 841 { 842 for_each_set_bit(i, &bitmap, sizeof(bitmap) * BITS_PER_BYTE) { 843 struct fgraph_ops *gops = fgraph_array[i]; 844 845 if (gops == &fgraph_stub) 846 continue; 847 848 gops->retfunc(&trace, gops); 849 } 850 } 851 852 /* 853 * The ftrace_graph_return() may still access the current 854 * ret_stack structure, we need to make sure the update of 855 * curr_ret_stack is after that. 856 */ 857 barrier(); 858 current->curr_ret_stack = offset - FGRAPH_FRAME_OFFSET; 859 860 current->curr_ret_depth--; 861 return ret; 862 } 863 864 /* 865 * After all architecures have selected HAVE_FUNCTION_GRAPH_RETVAL, we can 866 * leave only ftrace_return_to_handler(ret_regs). 867 */ 868 #ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL 869 unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs) 870 { 871 return __ftrace_return_to_handler(ret_regs, 872 fgraph_ret_regs_frame_pointer(ret_regs)); 873 } 874 #else 875 unsigned long ftrace_return_to_handler(unsigned long frame_pointer) 876 { 877 return __ftrace_return_to_handler(NULL, frame_pointer); 878 } 879 #endif 880 881 /** 882 * ftrace_graph_get_ret_stack - return the entry of the shadow stack 883 * @task: The task to read the shadow stack from. 884 * @idx: Index down the shadow stack 885 * 886 * Return the ret_struct on the shadow stack of the @task at the 887 * call graph at @idx starting with zero. If @idx is zero, it 888 * will return the last saved ret_stack entry. If it is greater than 889 * zero, it will return the corresponding ret_stack for the depth 890 * of saved return addresses. 891 */ 892 struct ftrace_ret_stack * 893 ftrace_graph_get_ret_stack(struct task_struct *task, int idx) 894 { 895 struct ftrace_ret_stack *ret_stack = NULL; 896 int offset = task->curr_ret_stack; 897 898 if (offset < 0) 899 return NULL; 900 901 do { 902 ret_stack = get_ret_stack(task, offset, &offset); 903 } while (ret_stack && --idx >= 0); 904 905 return ret_stack; 906 } 907 908 /** 909 * ftrace_graph_ret_addr - return the original value of the return address 910 * @task: The task the unwinder is being executed on 911 * @idx: An initialized pointer to the next stack index to use 912 * @ret: The current return address (likely pointing to return_handler) 913 * @retp: The address on the stack of the current return location 914 * 915 * This function can be called by stack unwinding code to convert a found stack 916 * return address (@ret) to its original value, in case the function graph 917 * tracer has modified it to be 'return_to_handler'. If the address hasn't 918 * been modified, the unchanged value of @ret is returned. 919 * 920 * @idx holds the last index used to know where to start from. It should be 921 * initialized to zero for the first iteration as that will mean to start 922 * at the top of the shadow stack. If the location is found, this pointer 923 * will be assigned that location so that if called again, it will continue 924 * where it left off. 925 * 926 * @retp is a pointer to the return address on the stack. 927 */ 928 unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx, 929 unsigned long ret, unsigned long *retp) 930 { 931 struct ftrace_ret_stack *ret_stack; 932 unsigned long return_handler = (unsigned long)dereference_kernel_function_descriptor(return_to_handler); 933 int i; 934 935 if (ret != return_handler) 936 return ret; 937 938 if (!idx) 939 return ret; 940 941 i = *idx ? : task->curr_ret_stack; 942 while (i > 0) { 943 ret_stack = get_ret_stack(task, i, &i); 944 if (!ret_stack) 945 break; 946 /* 947 * For the tail-call, there would be 2 or more ftrace_ret_stacks on 948 * the ret_stack, which records "return_to_handler" as the return 949 * address except for the last one. 950 * But on the real stack, there should be 1 entry because tail-call 951 * reuses the return address on the stack and jump to the next function. 952 * Thus we will continue to find real return address. 953 */ 954 if (ret_stack->retp == retp && 955 ret_stack->ret != return_handler) { 956 *idx = i; 957 return ret_stack->ret; 958 } 959 } 960 961 return ret; 962 } 963 964 static struct ftrace_ops graph_ops = { 965 .func = ftrace_graph_func, 966 .flags = FTRACE_OPS_GRAPH_STUB, 967 #ifdef FTRACE_GRAPH_TRAMP_ADDR 968 .trampoline = FTRACE_GRAPH_TRAMP_ADDR, 969 /* trampoline_size is only needed for dynamically allocated tramps */ 970 #endif 971 }; 972 973 void fgraph_init_ops(struct ftrace_ops *dst_ops, 974 struct ftrace_ops *src_ops) 975 { 976 dst_ops->flags = FTRACE_OPS_FL_PID | FTRACE_OPS_GRAPH_STUB; 977 978 #ifdef CONFIG_DYNAMIC_FTRACE 979 if (src_ops) { 980 dst_ops->func_hash = &src_ops->local_hash; 981 mutex_init(&dst_ops->local_hash.regex_lock); 982 INIT_LIST_HEAD(&dst_ops->subop_list); 983 dst_ops->flags |= FTRACE_OPS_FL_INITIALIZED; 984 } 985 #endif 986 } 987 988 void ftrace_graph_sleep_time_control(bool enable) 989 { 990 fgraph_sleep_time = enable; 991 } 992 993 /* 994 * Simply points to ftrace_stub, but with the proper protocol. 995 * Defined by the linker script in linux/vmlinux.lds.h 996 */ 997 void ftrace_stub_graph(struct ftrace_graph_ret *trace, struct fgraph_ops *gops); 998 999 /* The callbacks that hook a function */ 1000 trace_func_graph_ret_t ftrace_graph_return = ftrace_stub_graph; 1001 trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub; 1002 1003 /* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */ 1004 static int alloc_retstack_tasklist(unsigned long **ret_stack_list) 1005 { 1006 int i; 1007 int ret = 0; 1008 int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE; 1009 struct task_struct *g, *t; 1010 1011 for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) { 1012 ret_stack_list[i] = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL); 1013 if (!ret_stack_list[i]) { 1014 start = 0; 1015 end = i; 1016 ret = -ENOMEM; 1017 goto free; 1018 } 1019 } 1020 1021 rcu_read_lock(); 1022 for_each_process_thread(g, t) { 1023 if (start == end) { 1024 ret = -EAGAIN; 1025 goto unlock; 1026 } 1027 1028 if (t->ret_stack == NULL) { 1029 atomic_set(&t->trace_overrun, 0); 1030 ret_stack_init_task_vars(ret_stack_list[start]); 1031 t->curr_ret_stack = 0; 1032 t->curr_ret_depth = -1; 1033 /* Make sure the tasks see the 0 first: */ 1034 smp_wmb(); 1035 t->ret_stack = ret_stack_list[start++]; 1036 } 1037 } 1038 1039 unlock: 1040 rcu_read_unlock(); 1041 free: 1042 for (i = start; i < end; i++) 1043 kfree(ret_stack_list[i]); 1044 return ret; 1045 } 1046 1047 static void 1048 ftrace_graph_probe_sched_switch(void *ignore, bool preempt, 1049 struct task_struct *prev, 1050 struct task_struct *next, 1051 unsigned int prev_state) 1052 { 1053 unsigned long long timestamp; 1054 1055 /* 1056 * Does the user want to count the time a function was asleep. 1057 * If so, do not update the time stamps. 1058 */ 1059 if (fgraph_sleep_time) 1060 return; 1061 1062 timestamp = trace_clock_local(); 1063 1064 prev->ftrace_timestamp = timestamp; 1065 1066 /* only process tasks that we timestamped */ 1067 if (!next->ftrace_timestamp) 1068 return; 1069 1070 next->ftrace_sleeptime += timestamp - next->ftrace_timestamp; 1071 } 1072 1073 static DEFINE_PER_CPU(unsigned long *, idle_ret_stack); 1074 1075 static void 1076 graph_init_task(struct task_struct *t, unsigned long *ret_stack) 1077 { 1078 atomic_set(&t->trace_overrun, 0); 1079 ret_stack_init_task_vars(ret_stack); 1080 t->ftrace_timestamp = 0; 1081 t->curr_ret_stack = 0; 1082 t->curr_ret_depth = -1; 1083 /* make curr_ret_stack visible before we add the ret_stack */ 1084 smp_wmb(); 1085 t->ret_stack = ret_stack; 1086 } 1087 1088 /* 1089 * Allocate a return stack for the idle task. May be the first 1090 * time through, or it may be done by CPU hotplug online. 1091 */ 1092 void ftrace_graph_init_idle_task(struct task_struct *t, int cpu) 1093 { 1094 t->curr_ret_stack = 0; 1095 t->curr_ret_depth = -1; 1096 /* 1097 * The idle task has no parent, it either has its own 1098 * stack or no stack at all. 1099 */ 1100 if (t->ret_stack) 1101 WARN_ON(t->ret_stack != per_cpu(idle_ret_stack, cpu)); 1102 1103 if (ftrace_graph_active) { 1104 unsigned long *ret_stack; 1105 1106 ret_stack = per_cpu(idle_ret_stack, cpu); 1107 if (!ret_stack) { 1108 ret_stack = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL); 1109 if (!ret_stack) 1110 return; 1111 per_cpu(idle_ret_stack, cpu) = ret_stack; 1112 } 1113 graph_init_task(t, ret_stack); 1114 } 1115 } 1116 1117 /* Allocate a return stack for newly created task */ 1118 void ftrace_graph_init_task(struct task_struct *t) 1119 { 1120 /* Make sure we do not use the parent ret_stack */ 1121 t->ret_stack = NULL; 1122 t->curr_ret_stack = 0; 1123 t->curr_ret_depth = -1; 1124 1125 if (ftrace_graph_active) { 1126 unsigned long *ret_stack; 1127 1128 ret_stack = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL); 1129 if (!ret_stack) 1130 return; 1131 graph_init_task(t, ret_stack); 1132 } 1133 } 1134 1135 void ftrace_graph_exit_task(struct task_struct *t) 1136 { 1137 unsigned long *ret_stack = t->ret_stack; 1138 1139 t->ret_stack = NULL; 1140 /* NULL must become visible to IRQs before we free it: */ 1141 barrier(); 1142 1143 kfree(ret_stack); 1144 } 1145 1146 #ifdef CONFIG_DYNAMIC_FTRACE 1147 static int fgraph_pid_func(struct ftrace_graph_ent *trace, 1148 struct fgraph_ops *gops, 1149 struct fgraph_extras *extras) 1150 { 1151 struct trace_array *tr = gops->ops.private; 1152 int pid; 1153 1154 if (tr) { 1155 pid = this_cpu_read(tr->array_buffer.data->ftrace_ignore_pid); 1156 if (pid == FTRACE_PID_IGNORE) 1157 return 0; 1158 if (pid != FTRACE_PID_TRACE && 1159 pid != current->pid) 1160 return 0; 1161 } 1162 1163 return gops->saved_func(trace, gops, NULL); 1164 } 1165 1166 void fgraph_update_pid_func(void) 1167 { 1168 struct fgraph_ops *gops; 1169 struct ftrace_ops *op; 1170 1171 if (!(graph_ops.flags & FTRACE_OPS_FL_INITIALIZED)) 1172 return; 1173 1174 list_for_each_entry(op, &graph_ops.subop_list, list) { 1175 if (op->flags & FTRACE_OPS_FL_PID) { 1176 gops = container_of(op, struct fgraph_ops, ops); 1177 gops->entryfunc = ftrace_pids_enabled(op) ? 1178 fgraph_pid_func : gops->saved_func; 1179 if (ftrace_graph_active == 1) 1180 static_call_update(fgraph_func, gops->entryfunc); 1181 } 1182 } 1183 } 1184 #endif 1185 1186 /* Allocate a return stack for each task */ 1187 static int start_graph_tracing(void) 1188 { 1189 unsigned long **ret_stack_list; 1190 int ret, cpu; 1191 1192 ret_stack_list = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL); 1193 1194 if (!ret_stack_list) 1195 return -ENOMEM; 1196 1197 /* The cpu_boot init_task->ret_stack will never be freed */ 1198 for_each_online_cpu(cpu) { 1199 if (!idle_task(cpu)->ret_stack) 1200 ftrace_graph_init_idle_task(idle_task(cpu), cpu); 1201 } 1202 1203 do { 1204 ret = alloc_retstack_tasklist(ret_stack_list); 1205 } while (ret == -EAGAIN); 1206 1207 if (!ret) { 1208 ret = register_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL); 1209 if (ret) 1210 pr_info("ftrace_graph: Couldn't activate tracepoint" 1211 " probe to kernel_sched_switch\n"); 1212 } 1213 1214 kfree(ret_stack_list); 1215 return ret; 1216 } 1217 1218 static void init_task_vars(int idx) 1219 { 1220 struct task_struct *g, *t; 1221 int cpu; 1222 1223 for_each_online_cpu(cpu) { 1224 if (idle_task(cpu)->ret_stack) 1225 ret_stack_set_task_var(idle_task(cpu), idx, 0); 1226 } 1227 1228 read_lock(&tasklist_lock); 1229 for_each_process_thread(g, t) { 1230 if (t->ret_stack) 1231 ret_stack_set_task_var(t, idx, 0); 1232 } 1233 read_unlock(&tasklist_lock); 1234 } 1235 1236 static void ftrace_graph_enable_direct(bool enable_branch, struct fgraph_ops *gops) 1237 { 1238 trace_func_graph_ent_t func = NULL; 1239 trace_func_graph_ret_t retfunc = NULL; 1240 int i; 1241 1242 if (gops) { 1243 func = gops->entryfunc; 1244 retfunc = gops->retfunc; 1245 fgraph_direct_gops = gops; 1246 } else { 1247 for_each_set_bit(i, &fgraph_array_bitmask, 1248 sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) { 1249 func = fgraph_array[i]->entryfunc; 1250 retfunc = fgraph_array[i]->retfunc; 1251 fgraph_direct_gops = fgraph_array[i]; 1252 } 1253 } 1254 if (WARN_ON_ONCE(!func)) 1255 return; 1256 1257 static_call_update(fgraph_func, func); 1258 static_call_update(fgraph_retfunc, retfunc); 1259 if (enable_branch) 1260 static_branch_disable(&fgraph_do_direct); 1261 } 1262 1263 static void ftrace_graph_disable_direct(bool disable_branch) 1264 { 1265 if (disable_branch) 1266 static_branch_disable(&fgraph_do_direct); 1267 static_call_update(fgraph_func, ftrace_graph_entry_stub); 1268 static_call_update(fgraph_retfunc, ftrace_graph_ret_stub); 1269 fgraph_direct_gops = &fgraph_stub; 1270 } 1271 1272 int register_ftrace_graph(struct fgraph_ops *gops) 1273 { 1274 int command = 0; 1275 int ret = 0; 1276 int i = -1; 1277 1278 mutex_lock(&ftrace_lock); 1279 1280 if (!fgraph_array[0]) { 1281 /* The array must always have real data on it */ 1282 for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) 1283 fgraph_array[i] = &fgraph_stub; 1284 fgraph_lru_init(); 1285 } 1286 1287 i = fgraph_lru_alloc_index(); 1288 if (i < 0 || WARN_ON_ONCE(fgraph_array[i] != &fgraph_stub)) { 1289 ret = -ENOSPC; 1290 goto out; 1291 } 1292 gops->idx = i; 1293 1294 ftrace_graph_active++; 1295 1296 if (ftrace_graph_active == 2) 1297 ftrace_graph_disable_direct(true); 1298 1299 if (ftrace_graph_active == 1) { 1300 ftrace_graph_enable_direct(false, gops); 1301 register_pm_notifier(&ftrace_suspend_notifier); 1302 ret = start_graph_tracing(); 1303 if (ret) 1304 goto error; 1305 /* 1306 * Some archs just test to see if these are not 1307 * the default function 1308 */ 1309 ftrace_graph_return = return_run; 1310 ftrace_graph_entry = entry_run; 1311 command = FTRACE_START_FUNC_RET; 1312 } else { 1313 init_task_vars(gops->idx); 1314 } 1315 /* Always save the function, and reset at unregistering */ 1316 gops->saved_func = gops->entryfunc; 1317 1318 ret = ftrace_startup_subops(&graph_ops, &gops->ops, command); 1319 if (!ret) 1320 fgraph_array[i] = gops; 1321 1322 error: 1323 if (ret) { 1324 ftrace_graph_active--; 1325 gops->saved_func = NULL; 1326 fgraph_lru_release_index(i); 1327 } 1328 out: 1329 mutex_unlock(&ftrace_lock); 1330 return ret; 1331 } 1332 1333 void unregister_ftrace_graph(struct fgraph_ops *gops) 1334 { 1335 int command = 0; 1336 1337 mutex_lock(&ftrace_lock); 1338 1339 if (unlikely(!ftrace_graph_active)) 1340 goto out; 1341 1342 if (unlikely(gops->idx < 0 || gops->idx >= FGRAPH_ARRAY_SIZE || 1343 fgraph_array[gops->idx] != gops)) 1344 goto out; 1345 1346 if (fgraph_lru_release_index(gops->idx) < 0) 1347 goto out; 1348 1349 fgraph_array[gops->idx] = &fgraph_stub; 1350 1351 ftrace_graph_active--; 1352 1353 if (!ftrace_graph_active) 1354 command = FTRACE_STOP_FUNC_RET; 1355 1356 ftrace_shutdown_subops(&graph_ops, &gops->ops, command); 1357 1358 if (ftrace_graph_active == 1) 1359 ftrace_graph_enable_direct(true, NULL); 1360 else if (!ftrace_graph_active) 1361 ftrace_graph_disable_direct(false); 1362 1363 if (!ftrace_graph_active) { 1364 ftrace_graph_return = ftrace_stub_graph; 1365 ftrace_graph_entry = ftrace_graph_entry_stub; 1366 unregister_pm_notifier(&ftrace_suspend_notifier); 1367 unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL); 1368 } 1369 out: 1370 gops->saved_func = NULL; 1371 mutex_unlock(&ftrace_lock); 1372 } 1373