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 (4096) 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 kmem_cache *fgraph_stack_cachep; 176 177 static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE]; 178 static unsigned long fgraph_array_bitmask; 179 180 /* LRU index table for fgraph_array */ 181 static int fgraph_lru_table[FGRAPH_ARRAY_SIZE]; 182 static int fgraph_lru_next; 183 static int fgraph_lru_last; 184 185 /* Initialize fgraph_lru_table with unused index */ 186 static void fgraph_lru_init(void) 187 { 188 int i; 189 190 for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) 191 fgraph_lru_table[i] = i; 192 } 193 194 /* Release the used index to the LRU table */ 195 static int fgraph_lru_release_index(int idx) 196 { 197 if (idx < 0 || idx >= FGRAPH_ARRAY_SIZE || 198 WARN_ON_ONCE(fgraph_lru_table[fgraph_lru_last] != -1)) 199 return -1; 200 201 fgraph_lru_table[fgraph_lru_last] = idx; 202 fgraph_lru_last = (fgraph_lru_last + 1) % FGRAPH_ARRAY_SIZE; 203 204 clear_bit(idx, &fgraph_array_bitmask); 205 return 0; 206 } 207 208 /* Allocate a new index from LRU table */ 209 static int fgraph_lru_alloc_index(void) 210 { 211 int idx = fgraph_lru_table[fgraph_lru_next]; 212 213 /* No id is available */ 214 if (idx == -1) 215 return -1; 216 217 fgraph_lru_table[fgraph_lru_next] = -1; 218 fgraph_lru_next = (fgraph_lru_next + 1) % FGRAPH_ARRAY_SIZE; 219 220 set_bit(idx, &fgraph_array_bitmask); 221 return idx; 222 } 223 224 /* Get the offset to the fgraph frame from a ret_stack value */ 225 static inline int __get_offset(unsigned long val) 226 { 227 return val & FGRAPH_FRAME_OFFSET_MASK; 228 } 229 230 /* Get the type of word from a ret_stack value */ 231 static inline int __get_type(unsigned long val) 232 { 233 return (val >> FGRAPH_TYPE_SHIFT) & FGRAPH_TYPE_MASK; 234 } 235 236 /* Get the data_index for a DATA type ret_stack word */ 237 static inline int __get_data_index(unsigned long val) 238 { 239 return (val >> FGRAPH_DATA_INDEX_SHIFT) & FGRAPH_DATA_INDEX_MASK; 240 } 241 242 /* Get the data_size for a DATA type ret_stack word */ 243 static inline int __get_data_size(unsigned long val) 244 { 245 return ((val >> FGRAPH_DATA_SHIFT) & FGRAPH_DATA_MASK) + 1; 246 } 247 248 /* Get the word from the ret_stack at @offset */ 249 static inline unsigned long get_fgraph_entry(struct task_struct *t, int offset) 250 { 251 return t->ret_stack[offset]; 252 } 253 254 /* Get the FRAME_OFFSET from the word from the @offset on ret_stack */ 255 static inline int get_frame_offset(struct task_struct *t, int offset) 256 { 257 return __get_offset(t->ret_stack[offset]); 258 } 259 260 /* For BITMAP type: get the bitmask from the @offset at ret_stack */ 261 static inline unsigned long 262 get_bitmap_bits(struct task_struct *t, int offset) 263 { 264 return (t->ret_stack[offset] >> FGRAPH_INDEX_SHIFT) & FGRAPH_INDEX_MASK; 265 } 266 267 /* Write the bitmap to the ret_stack at @offset (does index, offset and bitmask) */ 268 static inline void 269 set_bitmap(struct task_struct *t, int offset, unsigned long bitmap) 270 { 271 t->ret_stack[offset] = (bitmap << FGRAPH_INDEX_SHIFT) | 272 (FGRAPH_TYPE_BITMAP << FGRAPH_TYPE_SHIFT) | FGRAPH_FRAME_OFFSET; 273 } 274 275 /* For DATA type: get the data saved under the ret_stack word at @offset */ 276 static inline void *get_data_type_data(struct task_struct *t, int offset) 277 { 278 unsigned long val = t->ret_stack[offset]; 279 280 if (__get_type(val) != FGRAPH_TYPE_DATA) 281 return NULL; 282 offset -= __get_data_size(val); 283 return (void *)&t->ret_stack[offset]; 284 } 285 286 /* Create the ret_stack word for a DATA type */ 287 static inline unsigned long make_data_type_val(int idx, int size, int offset) 288 { 289 return (idx << FGRAPH_DATA_INDEX_SHIFT) | 290 ((size - 1) << FGRAPH_DATA_SHIFT) | 291 (FGRAPH_TYPE_DATA << FGRAPH_TYPE_SHIFT) | offset; 292 } 293 294 /* ftrace_graph_entry set to this to tell some archs to run function graph */ 295 static int entry_run(struct ftrace_graph_ent *trace, struct fgraph_ops *ops) 296 { 297 return 0; 298 } 299 300 /* ftrace_graph_return set to this to tell some archs to run function graph */ 301 static void return_run(struct ftrace_graph_ret *trace, struct fgraph_ops *ops) 302 { 303 } 304 305 static void ret_stack_set_task_var(struct task_struct *t, int idx, long val) 306 { 307 unsigned long *gvals = SHADOW_STACK_TASK_VARS(t->ret_stack); 308 309 gvals[idx] = val; 310 } 311 312 static unsigned long * 313 ret_stack_get_task_var(struct task_struct *t, int idx) 314 { 315 unsigned long *gvals = SHADOW_STACK_TASK_VARS(t->ret_stack); 316 317 return &gvals[idx]; 318 } 319 320 static void ret_stack_init_task_vars(unsigned long *ret_stack) 321 { 322 unsigned long *gvals = SHADOW_STACK_TASK_VARS(ret_stack); 323 324 memset(gvals, 0, sizeof(*gvals) * FGRAPH_ARRAY_SIZE); 325 } 326 327 /** 328 * fgraph_reserve_data - Reserve storage on the task's ret_stack 329 * @idx: The index of fgraph_array 330 * @size_bytes: The size in bytes to reserve 331 * 332 * Reserves space of up to FGRAPH_MAX_DATA_SIZE bytes on the 333 * task's ret_stack shadow stack, for a given fgraph_ops during 334 * the entryfunc() call. If entryfunc() returns zero, the storage 335 * is discarded. An entryfunc() can only call this once per iteration. 336 * The fgraph_ops retfunc() can retrieve this stored data with 337 * fgraph_retrieve_data(). 338 * 339 * Returns: On success, a pointer to the data on the stack. 340 * Otherwise, NULL if there's not enough space left on the 341 * ret_stack for the data, or if fgraph_reserve_data() was called 342 * more than once for a single entryfunc() call. 343 */ 344 void *fgraph_reserve_data(int idx, int size_bytes) 345 { 346 unsigned long val; 347 void *data; 348 int curr_ret_stack = current->curr_ret_stack; 349 int data_size; 350 351 if (size_bytes > FGRAPH_MAX_DATA_SIZE) 352 return NULL; 353 354 /* Convert the data size to number of longs. */ 355 data_size = (size_bytes + sizeof(long) - 1) >> (sizeof(long) == 4 ? 2 : 3); 356 357 val = get_fgraph_entry(current, curr_ret_stack - 1); 358 data = ¤t->ret_stack[curr_ret_stack]; 359 360 curr_ret_stack += data_size + 1; 361 if (unlikely(curr_ret_stack >= SHADOW_STACK_MAX_OFFSET)) 362 return NULL; 363 364 val = make_data_type_val(idx, data_size, __get_offset(val) + data_size + 1); 365 366 /* Set the last word to be reserved */ 367 current->ret_stack[curr_ret_stack - 1] = val; 368 369 /* Make sure interrupts see this */ 370 barrier(); 371 current->curr_ret_stack = curr_ret_stack; 372 /* Again sync with interrupts, and reset reserve */ 373 current->ret_stack[curr_ret_stack - 1] = val; 374 375 return data; 376 } 377 378 /** 379 * fgraph_retrieve_data - Retrieve stored data from fgraph_reserve_data() 380 * @idx: the index of fgraph_array (fgraph_ops::idx) 381 * @size_bytes: pointer to retrieved data size. 382 * 383 * This is to be called by a fgraph_ops retfunc(), to retrieve data that 384 * was stored by the fgraph_ops entryfunc() on the function entry. 385 * That is, this will retrieve the data that was reserved on the 386 * entry of the function that corresponds to the exit of the function 387 * that the fgraph_ops retfunc() is called on. 388 * 389 * Returns: The stored data from fgraph_reserve_data() called by the 390 * matching entryfunc() for the retfunc() this is called from. 391 * Or NULL if there was nothing stored. 392 */ 393 void *fgraph_retrieve_data(int idx, int *size_bytes) 394 { 395 return fgraph_retrieve_parent_data(idx, size_bytes, 0); 396 } 397 398 /** 399 * fgraph_get_task_var - retrieve a task specific state variable 400 * @gops: The ftrace_ops that owns the task specific variable 401 * 402 * Every registered fgraph_ops has a task state variable 403 * reserved on the task's ret_stack. This function returns the 404 * address to that variable. 405 * 406 * Returns the address to the fgraph_ops @gops tasks specific 407 * unsigned long variable. 408 */ 409 unsigned long *fgraph_get_task_var(struct fgraph_ops *gops) 410 { 411 return ret_stack_get_task_var(current, gops->idx); 412 } 413 414 /* 415 * @offset: The offset into @t->ret_stack to find the ret_stack entry 416 * @frame_offset: Where to place the offset into @t->ret_stack of that entry 417 * 418 * Returns a pointer to the previous ret_stack below @offset or NULL 419 * when it reaches the bottom of the stack. 420 * 421 * Calling this with: 422 * 423 * offset = task->curr_ret_stack; 424 * do { 425 * ret_stack = get_ret_stack(task, offset, &offset); 426 * } while (ret_stack); 427 * 428 * Will iterate through all the ret_stack entries from curr_ret_stack 429 * down to the first one. 430 */ 431 static inline struct ftrace_ret_stack * 432 get_ret_stack(struct task_struct *t, int offset, int *frame_offset) 433 { 434 int offs; 435 436 BUILD_BUG_ON(FGRAPH_FRAME_SIZE % sizeof(long)); 437 438 if (unlikely(offset <= 0)) 439 return NULL; 440 441 offs = get_frame_offset(t, --offset); 442 if (WARN_ON_ONCE(offs <= 0 || offs > offset)) 443 return NULL; 444 445 offset -= offs; 446 447 *frame_offset = offset; 448 return RET_STACK(t, offset); 449 } 450 451 /** 452 * fgraph_retrieve_parent_data - get data from a parent function 453 * @idx: The index into the fgraph_array (fgraph_ops::idx) 454 * @size_bytes: A pointer to retrieved data size 455 * @depth: The depth to find the parent (0 is the current function) 456 * 457 * This is similar to fgraph_retrieve_data() but can be used to retrieve 458 * data from a parent caller function. 459 * 460 * Return: a pointer to the specified parent data or NULL if not found 461 */ 462 void *fgraph_retrieve_parent_data(int idx, int *size_bytes, int depth) 463 { 464 struct ftrace_ret_stack *ret_stack = NULL; 465 int offset = current->curr_ret_stack; 466 unsigned long val; 467 468 if (offset <= 0) 469 return NULL; 470 471 for (;;) { 472 int next_offset; 473 474 ret_stack = get_ret_stack(current, offset, &next_offset); 475 if (!ret_stack || --depth < 0) 476 break; 477 offset = next_offset; 478 } 479 480 if (!ret_stack) 481 return NULL; 482 483 offset--; 484 485 val = get_fgraph_entry(current, offset); 486 while (__get_type(val) == FGRAPH_TYPE_DATA) { 487 if (__get_data_index(val) == idx) 488 goto found; 489 offset -= __get_data_size(val) + 1; 490 val = get_fgraph_entry(current, offset); 491 } 492 return NULL; 493 found: 494 if (size_bytes) 495 *size_bytes = __get_data_size(val) * sizeof(long); 496 return get_data_type_data(current, offset); 497 } 498 499 /* Both enabled by default (can be cleared by function_graph tracer flags */ 500 bool fgraph_sleep_time = true; 501 502 #ifdef CONFIG_DYNAMIC_FTRACE 503 /* 504 * archs can override this function if they must do something 505 * to enable hook for graph tracer. 506 */ 507 int __weak ftrace_enable_ftrace_graph_caller(void) 508 { 509 return 0; 510 } 511 512 /* 513 * archs can override this function if they must do something 514 * to disable hook for graph tracer. 515 */ 516 int __weak ftrace_disable_ftrace_graph_caller(void) 517 { 518 return 0; 519 } 520 #endif 521 522 int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace, 523 struct fgraph_ops *gops) 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 unsigned long bitmap = 0; 652 int offset; 653 int i; 654 655 trace.func = func; 656 trace.depth = ++current->curr_ret_depth; 657 658 offset = ftrace_push_return_trace(ret, func, frame_pointer, retp, 0); 659 if (offset < 0) 660 goto out; 661 662 #ifdef CONFIG_HAVE_STATIC_CALL 663 if (static_branch_likely(&fgraph_do_direct)) { 664 int save_curr_ret_stack = current->curr_ret_stack; 665 666 if (static_call(fgraph_func)(&trace, fgraph_direct_gops)) 667 bitmap |= BIT(fgraph_direct_gops->idx); 668 else 669 /* Clear out any saved storage */ 670 current->curr_ret_stack = save_curr_ret_stack; 671 } else 672 #endif 673 { 674 for_each_set_bit(i, &fgraph_array_bitmask, 675 sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) { 676 struct fgraph_ops *gops = READ_ONCE(fgraph_array[i]); 677 int save_curr_ret_stack; 678 679 if (gops == &fgraph_stub) 680 continue; 681 682 save_curr_ret_stack = current->curr_ret_stack; 683 if (ftrace_ops_test(&gops->ops, func, NULL) && 684 gops->entryfunc(&trace, gops)) 685 bitmap |= BIT(i); 686 else 687 /* Clear out any saved storage */ 688 current->curr_ret_stack = save_curr_ret_stack; 689 } 690 } 691 692 if (!bitmap) 693 goto out_ret; 694 695 /* 696 * Since this function uses fgraph_idx = 0 as a tail-call checking 697 * flag, set that bit always. 698 */ 699 set_bitmap(current, offset, bitmap | BIT(0)); 700 701 return 0; 702 out_ret: 703 current->curr_ret_stack -= FGRAPH_FRAME_OFFSET + 1; 704 out: 705 current->curr_ret_depth--; 706 return -EBUSY; 707 } 708 709 /* Retrieve a function return address to the trace stack on thread info.*/ 710 static struct ftrace_ret_stack * 711 ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret, 712 unsigned long frame_pointer, int *offset) 713 { 714 struct ftrace_ret_stack *ret_stack; 715 716 ret_stack = get_ret_stack(current, current->curr_ret_stack, offset); 717 718 if (unlikely(!ret_stack)) { 719 ftrace_graph_stop(); 720 WARN(1, "Bad function graph ret_stack pointer: %d", 721 current->curr_ret_stack); 722 /* Might as well panic, otherwise we have no where to go */ 723 *ret = (unsigned long)panic; 724 return NULL; 725 } 726 727 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST 728 /* 729 * The arch may choose to record the frame pointer used 730 * and check it here to make sure that it is what we expect it 731 * to be. If gcc does not set the place holder of the return 732 * address in the frame pointer, and does a copy instead, then 733 * the function graph trace will fail. This test detects this 734 * case. 735 * 736 * Currently, x86_32 with optimize for size (-Os) makes the latest 737 * gcc do the above. 738 * 739 * Note, -mfentry does not use frame pointers, and this test 740 * is not needed if CC_USING_FENTRY is set. 741 */ 742 if (unlikely(ret_stack->fp != frame_pointer)) { 743 ftrace_graph_stop(); 744 WARN(1, "Bad frame pointer: expected %lx, received %lx\n" 745 " from func %ps return to %lx\n", 746 ret_stack->fp, 747 frame_pointer, 748 (void *)ret_stack->func, 749 ret_stack->ret); 750 *ret = (unsigned long)panic; 751 return NULL; 752 } 753 #endif 754 755 *offset += FGRAPH_FRAME_OFFSET; 756 *ret = ret_stack->ret; 757 trace->func = ret_stack->func; 758 trace->overrun = atomic_read(¤t->trace_overrun); 759 trace->depth = current->curr_ret_depth; 760 /* 761 * We still want to trace interrupts coming in if 762 * max_depth is set to 1. Make sure the decrement is 763 * seen before ftrace_graph_return. 764 */ 765 barrier(); 766 767 return ret_stack; 768 } 769 770 /* 771 * Hibernation protection. 772 * The state of the current task is too much unstable during 773 * suspend/restore to disk. We want to protect against that. 774 */ 775 static int 776 ftrace_suspend_notifier_call(struct notifier_block *bl, unsigned long state, 777 void *unused) 778 { 779 switch (state) { 780 case PM_HIBERNATION_PREPARE: 781 pause_graph_tracing(); 782 break; 783 784 case PM_POST_HIBERNATION: 785 unpause_graph_tracing(); 786 break; 787 } 788 return NOTIFY_DONE; 789 } 790 791 static struct notifier_block ftrace_suspend_notifier = { 792 .notifier_call = ftrace_suspend_notifier_call, 793 }; 794 795 /* fgraph_ret_regs is not defined without CONFIG_FUNCTION_GRAPH_RETVAL */ 796 struct fgraph_ret_regs; 797 798 /* 799 * Send the trace to the ring-buffer. 800 * @return the original return address. 801 */ 802 static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs, 803 unsigned long frame_pointer) 804 { 805 struct ftrace_ret_stack *ret_stack; 806 struct ftrace_graph_ret trace; 807 unsigned long bitmap; 808 unsigned long ret; 809 int offset; 810 int i; 811 812 ret_stack = ftrace_pop_return_trace(&trace, &ret, frame_pointer, &offset); 813 814 if (unlikely(!ret_stack)) { 815 ftrace_graph_stop(); 816 WARN_ON(1); 817 /* Might as well panic. What else to do? */ 818 return (unsigned long)panic; 819 } 820 821 trace.rettime = trace_clock_local(); 822 #ifdef CONFIG_FUNCTION_GRAPH_RETVAL 823 trace.retval = fgraph_ret_regs_return_value(ret_regs); 824 #endif 825 826 bitmap = get_bitmap_bits(current, offset); 827 828 #ifdef CONFIG_HAVE_STATIC_CALL 829 if (static_branch_likely(&fgraph_do_direct)) { 830 if (test_bit(fgraph_direct_gops->idx, &bitmap)) 831 static_call(fgraph_retfunc)(&trace, fgraph_direct_gops); 832 } else 833 #endif 834 { 835 for_each_set_bit(i, &bitmap, sizeof(bitmap) * BITS_PER_BYTE) { 836 struct fgraph_ops *gops = fgraph_array[i]; 837 838 if (gops == &fgraph_stub) 839 continue; 840 841 gops->retfunc(&trace, gops); 842 } 843 } 844 845 /* 846 * The ftrace_graph_return() may still access the current 847 * ret_stack structure, we need to make sure the update of 848 * curr_ret_stack is after that. 849 */ 850 barrier(); 851 current->curr_ret_stack = offset - FGRAPH_FRAME_OFFSET; 852 853 current->curr_ret_depth--; 854 return ret; 855 } 856 857 /* 858 * After all architecures have selected HAVE_FUNCTION_GRAPH_RETVAL, we can 859 * leave only ftrace_return_to_handler(ret_regs). 860 */ 861 #ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL 862 unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs) 863 { 864 return __ftrace_return_to_handler(ret_regs, 865 fgraph_ret_regs_frame_pointer(ret_regs)); 866 } 867 #else 868 unsigned long ftrace_return_to_handler(unsigned long frame_pointer) 869 { 870 return __ftrace_return_to_handler(NULL, frame_pointer); 871 } 872 #endif 873 874 /** 875 * ftrace_graph_get_ret_stack - return the entry of the shadow stack 876 * @task: The task to read the shadow stack from. 877 * @idx: Index down the shadow stack 878 * 879 * Return the ret_struct on the shadow stack of the @task at the 880 * call graph at @idx starting with zero. If @idx is zero, it 881 * will return the last saved ret_stack entry. If it is greater than 882 * zero, it will return the corresponding ret_stack for the depth 883 * of saved return addresses. 884 */ 885 struct ftrace_ret_stack * 886 ftrace_graph_get_ret_stack(struct task_struct *task, int idx) 887 { 888 struct ftrace_ret_stack *ret_stack = NULL; 889 int offset = task->curr_ret_stack; 890 891 if (offset < 0) 892 return NULL; 893 894 do { 895 ret_stack = get_ret_stack(task, offset, &offset); 896 } while (ret_stack && --idx >= 0); 897 898 return ret_stack; 899 } 900 901 /** 902 * ftrace_graph_top_ret_addr - return the top return address in the shadow stack 903 * @task: The task to read the shadow stack from. 904 * 905 * Return the first return address on the shadow stack of the @task, which is 906 * not the fgraph's return_to_handler. 907 */ 908 unsigned long ftrace_graph_top_ret_addr(struct task_struct *task) 909 { 910 unsigned long return_handler = (unsigned long)dereference_kernel_function_descriptor(return_to_handler); 911 struct ftrace_ret_stack *ret_stack = NULL; 912 int offset = task->curr_ret_stack; 913 914 if (offset < 0) 915 return 0; 916 917 do { 918 ret_stack = get_ret_stack(task, offset, &offset); 919 } while (ret_stack && ret_stack->ret == return_handler); 920 921 return ret_stack ? ret_stack->ret : 0; 922 } 923 924 /** 925 * ftrace_graph_ret_addr - return the original value of the return address 926 * @task: The task the unwinder is being executed on 927 * @idx: An initialized pointer to the next stack index to use 928 * @ret: The current return address (likely pointing to return_handler) 929 * @retp: The address on the stack of the current return location 930 * 931 * This function can be called by stack unwinding code to convert a found stack 932 * return address (@ret) to its original value, in case the function graph 933 * tracer has modified it to be 'return_to_handler'. If the address hasn't 934 * been modified, the unchanged value of @ret is returned. 935 * 936 * @idx holds the last index used to know where to start from. It should be 937 * initialized to zero for the first iteration as that will mean to start 938 * at the top of the shadow stack. If the location is found, this pointer 939 * will be assigned that location so that if called again, it will continue 940 * where it left off. 941 * 942 * @retp is a pointer to the return address on the stack. 943 */ 944 unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx, 945 unsigned long ret, unsigned long *retp) 946 { 947 struct ftrace_ret_stack *ret_stack; 948 unsigned long return_handler = (unsigned long)dereference_kernel_function_descriptor(return_to_handler); 949 int i; 950 951 if (ret != return_handler) 952 return ret; 953 954 if (!idx) 955 return ret; 956 957 i = *idx ? : task->curr_ret_stack; 958 while (i > 0) { 959 ret_stack = get_ret_stack(task, i, &i); 960 if (!ret_stack) 961 break; 962 /* 963 * For the tail-call, there would be 2 or more ftrace_ret_stacks on 964 * the ret_stack, which records "return_to_handler" as the return 965 * address except for the last one. 966 * But on the real stack, there should be 1 entry because tail-call 967 * reuses the return address on the stack and jump to the next function. 968 * Thus we will continue to find real return address. 969 */ 970 if (ret_stack->retp == retp && 971 ret_stack->ret != return_handler) { 972 *idx = i; 973 return ret_stack->ret; 974 } 975 } 976 977 return ret; 978 } 979 980 static struct ftrace_ops graph_ops = { 981 .func = ftrace_graph_func, 982 .flags = FTRACE_OPS_GRAPH_STUB, 983 #ifdef FTRACE_GRAPH_TRAMP_ADDR 984 .trampoline = FTRACE_GRAPH_TRAMP_ADDR, 985 /* trampoline_size is only needed for dynamically allocated tramps */ 986 #endif 987 }; 988 989 void fgraph_init_ops(struct ftrace_ops *dst_ops, 990 struct ftrace_ops *src_ops) 991 { 992 dst_ops->flags = FTRACE_OPS_FL_PID | FTRACE_OPS_GRAPH_STUB; 993 994 #ifdef CONFIG_DYNAMIC_FTRACE 995 if (src_ops) { 996 dst_ops->func_hash = &src_ops->local_hash; 997 mutex_init(&dst_ops->local_hash.regex_lock); 998 INIT_LIST_HEAD(&dst_ops->subop_list); 999 dst_ops->flags |= FTRACE_OPS_FL_INITIALIZED; 1000 } 1001 #endif 1002 } 1003 1004 void ftrace_graph_sleep_time_control(bool enable) 1005 { 1006 fgraph_sleep_time = enable; 1007 } 1008 1009 /* 1010 * Simply points to ftrace_stub, but with the proper protocol. 1011 * Defined by the linker script in linux/vmlinux.lds.h 1012 */ 1013 void ftrace_stub_graph(struct ftrace_graph_ret *trace, struct fgraph_ops *gops); 1014 1015 /* The callbacks that hook a function */ 1016 trace_func_graph_ret_t ftrace_graph_return = ftrace_stub_graph; 1017 trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub; 1018 1019 /* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */ 1020 static int alloc_retstack_tasklist(unsigned long **ret_stack_list) 1021 { 1022 int i; 1023 int ret = 0; 1024 int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE; 1025 struct task_struct *g, *t; 1026 1027 if (WARN_ON_ONCE(!fgraph_stack_cachep)) 1028 return -ENOMEM; 1029 1030 for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) { 1031 ret_stack_list[i] = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL); 1032 if (!ret_stack_list[i]) { 1033 start = 0; 1034 end = i; 1035 ret = -ENOMEM; 1036 goto free; 1037 } 1038 } 1039 1040 rcu_read_lock(); 1041 for_each_process_thread(g, t) { 1042 if (start == end) { 1043 ret = -EAGAIN; 1044 goto unlock; 1045 } 1046 1047 if (t->ret_stack == NULL) { 1048 atomic_set(&t->trace_overrun, 0); 1049 ret_stack_init_task_vars(ret_stack_list[start]); 1050 t->curr_ret_stack = 0; 1051 t->curr_ret_depth = -1; 1052 /* Make sure the tasks see the 0 first: */ 1053 smp_wmb(); 1054 t->ret_stack = ret_stack_list[start++]; 1055 } 1056 } 1057 1058 unlock: 1059 rcu_read_unlock(); 1060 free: 1061 for (i = start; i < end; i++) 1062 kmem_cache_free(fgraph_stack_cachep, ret_stack_list[i]); 1063 return ret; 1064 } 1065 1066 static void 1067 ftrace_graph_probe_sched_switch(void *ignore, bool preempt, 1068 struct task_struct *prev, 1069 struct task_struct *next, 1070 unsigned int prev_state) 1071 { 1072 unsigned long long timestamp; 1073 1074 /* 1075 * Does the user want to count the time a function was asleep. 1076 * If so, do not update the time stamps. 1077 */ 1078 if (fgraph_sleep_time) 1079 return; 1080 1081 timestamp = trace_clock_local(); 1082 1083 prev->ftrace_timestamp = timestamp; 1084 1085 /* only process tasks that we timestamped */ 1086 if (!next->ftrace_timestamp) 1087 return; 1088 1089 next->ftrace_sleeptime += timestamp - next->ftrace_timestamp; 1090 } 1091 1092 static DEFINE_PER_CPU(unsigned long *, idle_ret_stack); 1093 1094 static void 1095 graph_init_task(struct task_struct *t, unsigned long *ret_stack) 1096 { 1097 atomic_set(&t->trace_overrun, 0); 1098 ret_stack_init_task_vars(ret_stack); 1099 t->ftrace_timestamp = 0; 1100 t->curr_ret_stack = 0; 1101 t->curr_ret_depth = -1; 1102 /* make curr_ret_stack visible before we add the ret_stack */ 1103 smp_wmb(); 1104 t->ret_stack = ret_stack; 1105 } 1106 1107 /* 1108 * Allocate a return stack for the idle task. May be the first 1109 * time through, or it may be done by CPU hotplug online. 1110 */ 1111 void ftrace_graph_init_idle_task(struct task_struct *t, int cpu) 1112 { 1113 t->curr_ret_stack = 0; 1114 t->curr_ret_depth = -1; 1115 /* 1116 * The idle task has no parent, it either has its own 1117 * stack or no stack at all. 1118 */ 1119 if (t->ret_stack) 1120 WARN_ON(t->ret_stack != per_cpu(idle_ret_stack, cpu)); 1121 1122 if (ftrace_graph_active) { 1123 unsigned long *ret_stack; 1124 1125 if (WARN_ON_ONCE(!fgraph_stack_cachep)) 1126 return; 1127 1128 ret_stack = per_cpu(idle_ret_stack, cpu); 1129 if (!ret_stack) { 1130 ret_stack = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL); 1131 if (!ret_stack) 1132 return; 1133 per_cpu(idle_ret_stack, cpu) = ret_stack; 1134 } 1135 graph_init_task(t, ret_stack); 1136 } 1137 } 1138 1139 /* Allocate a return stack for newly created task */ 1140 void ftrace_graph_init_task(struct task_struct *t) 1141 { 1142 /* Make sure we do not use the parent ret_stack */ 1143 t->ret_stack = NULL; 1144 t->curr_ret_stack = 0; 1145 t->curr_ret_depth = -1; 1146 1147 if (ftrace_graph_active) { 1148 unsigned long *ret_stack; 1149 1150 if (WARN_ON_ONCE(!fgraph_stack_cachep)) 1151 return; 1152 1153 ret_stack = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL); 1154 if (!ret_stack) 1155 return; 1156 graph_init_task(t, ret_stack); 1157 } 1158 } 1159 1160 void ftrace_graph_exit_task(struct task_struct *t) 1161 { 1162 unsigned long *ret_stack = t->ret_stack; 1163 1164 t->ret_stack = NULL; 1165 /* NULL must become visible to IRQs before we free it: */ 1166 barrier(); 1167 1168 if (ret_stack) { 1169 if (WARN_ON_ONCE(!fgraph_stack_cachep)) 1170 return; 1171 kmem_cache_free(fgraph_stack_cachep, ret_stack); 1172 } 1173 } 1174 1175 #ifdef CONFIG_DYNAMIC_FTRACE 1176 static int fgraph_pid_func(struct ftrace_graph_ent *trace, 1177 struct fgraph_ops *gops) 1178 { 1179 struct trace_array *tr = gops->ops.private; 1180 int pid; 1181 1182 if (tr) { 1183 pid = this_cpu_read(tr->array_buffer.data->ftrace_ignore_pid); 1184 if (pid == FTRACE_PID_IGNORE) 1185 return 0; 1186 if (pid != FTRACE_PID_TRACE && 1187 pid != current->pid) 1188 return 0; 1189 } 1190 1191 return gops->saved_func(trace, gops); 1192 } 1193 1194 void fgraph_update_pid_func(void) 1195 { 1196 struct fgraph_ops *gops; 1197 struct ftrace_ops *op; 1198 1199 if (!(graph_ops.flags & FTRACE_OPS_FL_INITIALIZED)) 1200 return; 1201 1202 list_for_each_entry(op, &graph_ops.subop_list, list) { 1203 if (op->flags & FTRACE_OPS_FL_PID) { 1204 gops = container_of(op, struct fgraph_ops, ops); 1205 gops->entryfunc = ftrace_pids_enabled(op) ? 1206 fgraph_pid_func : gops->saved_func; 1207 if (ftrace_graph_active == 1) 1208 static_call_update(fgraph_func, gops->entryfunc); 1209 } 1210 } 1211 } 1212 #endif 1213 1214 /* Allocate a return stack for each task */ 1215 static int start_graph_tracing(void) 1216 { 1217 unsigned long **ret_stack_list; 1218 int ret; 1219 1220 ret_stack_list = kcalloc(FTRACE_RETSTACK_ALLOC_SIZE, 1221 sizeof(*ret_stack_list), GFP_KERNEL); 1222 1223 if (!ret_stack_list) 1224 return -ENOMEM; 1225 1226 do { 1227 ret = alloc_retstack_tasklist(ret_stack_list); 1228 } while (ret == -EAGAIN); 1229 1230 if (!ret) { 1231 ret = register_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL); 1232 if (ret) 1233 pr_info("ftrace_graph: Couldn't activate tracepoint" 1234 " probe to kernel_sched_switch\n"); 1235 } 1236 1237 kfree(ret_stack_list); 1238 return ret; 1239 } 1240 1241 static void init_task_vars(int idx) 1242 { 1243 struct task_struct *g, *t; 1244 int cpu; 1245 1246 for_each_online_cpu(cpu) { 1247 if (idle_task(cpu)->ret_stack) 1248 ret_stack_set_task_var(idle_task(cpu), idx, 0); 1249 } 1250 1251 read_lock(&tasklist_lock); 1252 for_each_process_thread(g, t) { 1253 if (t->ret_stack) 1254 ret_stack_set_task_var(t, idx, 0); 1255 } 1256 read_unlock(&tasklist_lock); 1257 } 1258 1259 static void ftrace_graph_enable_direct(bool enable_branch, struct fgraph_ops *gops) 1260 { 1261 trace_func_graph_ent_t func = NULL; 1262 trace_func_graph_ret_t retfunc = NULL; 1263 int i; 1264 1265 if (gops) { 1266 func = gops->entryfunc; 1267 retfunc = gops->retfunc; 1268 fgraph_direct_gops = gops; 1269 } else { 1270 for_each_set_bit(i, &fgraph_array_bitmask, 1271 sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) { 1272 func = fgraph_array[i]->entryfunc; 1273 retfunc = fgraph_array[i]->retfunc; 1274 fgraph_direct_gops = fgraph_array[i]; 1275 } 1276 } 1277 if (WARN_ON_ONCE(!func)) 1278 return; 1279 1280 static_call_update(fgraph_func, func); 1281 static_call_update(fgraph_retfunc, retfunc); 1282 if (enable_branch) 1283 static_branch_disable(&fgraph_do_direct); 1284 } 1285 1286 static void ftrace_graph_disable_direct(bool disable_branch) 1287 { 1288 if (disable_branch) 1289 static_branch_disable(&fgraph_do_direct); 1290 static_call_update(fgraph_func, ftrace_graph_entry_stub); 1291 static_call_update(fgraph_retfunc, ftrace_graph_ret_stub); 1292 fgraph_direct_gops = &fgraph_stub; 1293 } 1294 1295 /* The cpu_boot init_task->ret_stack will never be freed */ 1296 static int fgraph_cpu_init(unsigned int cpu) 1297 { 1298 if (!idle_task(cpu)->ret_stack) 1299 ftrace_graph_init_idle_task(idle_task(cpu), cpu); 1300 return 0; 1301 } 1302 1303 int register_ftrace_graph(struct fgraph_ops *gops) 1304 { 1305 static bool fgraph_initialized; 1306 int command = 0; 1307 int ret = 0; 1308 int i = -1; 1309 1310 guard(mutex)(&ftrace_lock); 1311 1312 if (!fgraph_stack_cachep) { 1313 fgraph_stack_cachep = kmem_cache_create("fgraph_stack", 1314 SHADOW_STACK_SIZE, 1315 SHADOW_STACK_SIZE, 0, NULL); 1316 if (!fgraph_stack_cachep) 1317 return -ENOMEM; 1318 } 1319 1320 if (!fgraph_initialized) { 1321 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "fgraph:online", 1322 fgraph_cpu_init, NULL); 1323 if (ret < 0) { 1324 pr_warn("fgraph: Error to init cpu hotplug support\n"); 1325 return ret; 1326 } 1327 fgraph_initialized = true; 1328 ret = 0; 1329 } 1330 1331 if (!fgraph_array[0]) { 1332 /* The array must always have real data on it */ 1333 for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) 1334 fgraph_array[i] = &fgraph_stub; 1335 fgraph_lru_init(); 1336 } 1337 1338 i = fgraph_lru_alloc_index(); 1339 if (i < 0 || WARN_ON_ONCE(fgraph_array[i] != &fgraph_stub)) 1340 return -ENOSPC; 1341 gops->idx = i; 1342 1343 ftrace_graph_active++; 1344 1345 if (ftrace_graph_active == 2) 1346 ftrace_graph_disable_direct(true); 1347 1348 if (ftrace_graph_active == 1) { 1349 ftrace_graph_enable_direct(false, gops); 1350 register_pm_notifier(&ftrace_suspend_notifier); 1351 ret = start_graph_tracing(); 1352 if (ret) 1353 goto error; 1354 /* 1355 * Some archs just test to see if these are not 1356 * the default function 1357 */ 1358 ftrace_graph_return = return_run; 1359 ftrace_graph_entry = entry_run; 1360 command = FTRACE_START_FUNC_RET; 1361 } else { 1362 init_task_vars(gops->idx); 1363 } 1364 /* Always save the function, and reset at unregistering */ 1365 gops->saved_func = gops->entryfunc; 1366 1367 ret = ftrace_startup_subops(&graph_ops, &gops->ops, command); 1368 if (!ret) 1369 fgraph_array[i] = gops; 1370 1371 error: 1372 if (ret) { 1373 ftrace_graph_active--; 1374 gops->saved_func = NULL; 1375 fgraph_lru_release_index(i); 1376 } 1377 return ret; 1378 } 1379 1380 void unregister_ftrace_graph(struct fgraph_ops *gops) 1381 { 1382 int command = 0; 1383 1384 guard(mutex)(&ftrace_lock); 1385 1386 if (unlikely(!ftrace_graph_active)) 1387 return; 1388 1389 if (unlikely(gops->idx < 0 || gops->idx >= FGRAPH_ARRAY_SIZE || 1390 fgraph_array[gops->idx] != gops)) 1391 return; 1392 1393 if (fgraph_lru_release_index(gops->idx) < 0) 1394 return; 1395 1396 fgraph_array[gops->idx] = &fgraph_stub; 1397 1398 ftrace_graph_active--; 1399 1400 if (!ftrace_graph_active) 1401 command = FTRACE_STOP_FUNC_RET; 1402 1403 ftrace_shutdown_subops(&graph_ops, &gops->ops, command); 1404 1405 if (ftrace_graph_active == 1) 1406 ftrace_graph_enable_direct(true, NULL); 1407 else if (!ftrace_graph_active) 1408 ftrace_graph_disable_direct(false); 1409 1410 if (!ftrace_graph_active) { 1411 ftrace_graph_return = ftrace_stub_graph; 1412 ftrace_graph_entry = ftrace_graph_entry_stub; 1413 unregister_pm_notifier(&ftrace_suspend_notifier); 1414 unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL); 1415 } 1416 gops->saved_func = NULL; 1417 } 1418