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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Dynamic function tracing support.
4 *
5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
6 *
7 * Thanks goes to Ingo Molnar, for suggesting the idea.
8 * Mathieu Desnoyers, for suggesting postponing the modifications.
9 * Arjan van de Ven, for keeping me straight, and explaining to me
10 * the dangers of modifying code on the run.
11 */
12
13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/spinlock.h>
16#include <linux/hardirq.h>
17#include <linux/uaccess.h>
18#include <linux/ftrace.h>
19#include <linux/percpu.h>
20#include <linux/sched.h>
21#include <linux/slab.h>
22#include <linux/init.h>
23#include <linux/list.h>
24#include <linux/module.h>
25#include <linux/memory.h>
26#include <linux/vmalloc.h>
27#include <linux/set_memory.h>
28#include <linux/execmem.h>
29
30#include <trace/syscall.h>
31
32#include <asm/kprobes.h>
33#include <asm/ftrace.h>
34#include <asm/nops.h>
35#include <asm/text-patching.h>
36
37#ifdef CONFIG_DYNAMIC_FTRACE
38
39static int ftrace_poke_late = 0;
40
41void ftrace_arch_code_modify_prepare(void)
42 __acquires(&text_mutex)
43{
44 /*
45 * Need to grab text_mutex to prevent a race from module loading
46 * and live kernel patching from changing the text permissions while
47 * ftrace has it set to "read/write".
48 */
49 mutex_lock(&text_mutex);
50 ftrace_poke_late = 1;
51}
52
53void ftrace_arch_code_modify_post_process(void)
54 __releases(&text_mutex)
55{
56 /*
57 * ftrace_make_{call,nop}() may be called during
58 * module load, and we need to finish the text_poke_queue()
59 * that they do, here.
60 */
61 text_poke_finish();
62 ftrace_poke_late = 0;
63 mutex_unlock(&text_mutex);
64}
65
66static const char *ftrace_nop_replace(void)
67{
68 return x86_nops[5];
69}
70
71static const char *ftrace_call_replace(unsigned long ip, unsigned long addr)
72{
73 /*
74 * No need to translate into a callthunk. The trampoline does
75 * the depth accounting itself.
76 */
77 return text_gen_insn(CALL_INSN_OPCODE, (void *)ip, (void *)addr);
78}
79
80static int ftrace_verify_code(unsigned long ip, const char *old_code)
81{
82 char cur_code[MCOUNT_INSN_SIZE];
83
84 /*
85 * Note:
86 * We are paranoid about modifying text, as if a bug was to happen, it
87 * could cause us to read or write to someplace that could cause harm.
88 * Carefully read and modify the code with probe_kernel_*(), and make
89 * sure what we read is what we expected it to be before modifying it.
90 */
91 /* read the text we want to modify */
92 if (copy_from_kernel_nofault(cur_code, (void *)ip, MCOUNT_INSN_SIZE)) {
93 WARN_ON(1);
94 return -EFAULT;
95 }
96
97 /* Make sure it is what we expect it to be */
98 if (memcmp(cur_code, old_code, MCOUNT_INSN_SIZE) != 0) {
99 ftrace_expected = old_code;
100 WARN_ON(1);
101 return -EINVAL;
102 }
103
104 return 0;
105}
106
107/*
108 * Marked __ref because it calls text_poke_early() which is .init.text. That is
109 * ok because that call will happen early, during boot, when .init sections are
110 * still present.
111 */
112static int __ref
113ftrace_modify_code_direct(unsigned long ip, const char *old_code,
114 const char *new_code)
115{
116 int ret = ftrace_verify_code(ip, old_code);
117 if (ret)
118 return ret;
119
120 /* replace the text with the new text */
121 if (ftrace_poke_late) {
122 text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
123 } else {
124 mutex_lock(&text_mutex);
125 text_poke((void *)ip, new_code, MCOUNT_INSN_SIZE);
126 mutex_unlock(&text_mutex);
127 }
128 return 0;
129}
130
131int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
132{
133 unsigned long ip = rec->ip;
134 const char *new, *old;
135
136 old = ftrace_call_replace(ip, addr);
137 new = ftrace_nop_replace();
138
139 /*
140 * On boot up, and when modules are loaded, the MCOUNT_ADDR
141 * is converted to a nop, and will never become MCOUNT_ADDR
142 * again. This code is either running before SMP (on boot up)
143 * or before the code will ever be executed (module load).
144 * We do not want to use the breakpoint version in this case,
145 * just modify the code directly.
146 */
147 if (addr == MCOUNT_ADDR)
148 return ftrace_modify_code_direct(ip, old, new);
149
150 /*
151 * x86 overrides ftrace_replace_code -- this function will never be used
152 * in this case.
153 */
154 WARN_ONCE(1, "invalid use of ftrace_make_nop");
155 return -EINVAL;
156}
157
158int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
159{
160 unsigned long ip = rec->ip;
161 const char *new, *old;
162
163 old = ftrace_nop_replace();
164 new = ftrace_call_replace(ip, addr);
165
166 /* Should only be called when module is loaded */
167 return ftrace_modify_code_direct(rec->ip, old, new);
168}
169
170/*
171 * Should never be called:
172 * As it is only called by __ftrace_replace_code() which is called by
173 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
174 * which is called to turn mcount into nops or nops into function calls
175 * but not to convert a function from not using regs to one that uses
176 * regs, which ftrace_modify_call() is for.
177 */
178int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
179 unsigned long addr)
180{
181 WARN_ON(1);
182 return -EINVAL;
183}
184
185int ftrace_update_ftrace_func(ftrace_func_t func)
186{
187 unsigned long ip;
188 const char *new;
189
190 ip = (unsigned long)(&ftrace_call);
191 new = ftrace_call_replace(ip, (unsigned long)func);
192 text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
193
194 ip = (unsigned long)(&ftrace_regs_call);
195 new = ftrace_call_replace(ip, (unsigned long)func);
196 text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
197
198 return 0;
199}
200
201void ftrace_replace_code(int enable)
202{
203 struct ftrace_rec_iter *iter;
204 struct dyn_ftrace *rec;
205 const char *new, *old;
206 int ret;
207
208 for_ftrace_rec_iter(iter) {
209 rec = ftrace_rec_iter_record(iter);
210
211 switch (ftrace_test_record(rec, enable)) {
212 case FTRACE_UPDATE_IGNORE:
213 default:
214 continue;
215
216 case FTRACE_UPDATE_MAKE_CALL:
217 old = ftrace_nop_replace();
218 break;
219
220 case FTRACE_UPDATE_MODIFY_CALL:
221 case FTRACE_UPDATE_MAKE_NOP:
222 old = ftrace_call_replace(rec->ip, ftrace_get_addr_curr(rec));
223 break;
224 }
225
226 ret = ftrace_verify_code(rec->ip, old);
227 if (ret) {
228 ftrace_expected = old;
229 ftrace_bug(ret, rec);
230 ftrace_expected = NULL;
231 return;
232 }
233 }
234
235 for_ftrace_rec_iter(iter) {
236 rec = ftrace_rec_iter_record(iter);
237
238 switch (ftrace_test_record(rec, enable)) {
239 case FTRACE_UPDATE_IGNORE:
240 default:
241 continue;
242
243 case FTRACE_UPDATE_MAKE_CALL:
244 case FTRACE_UPDATE_MODIFY_CALL:
245 new = ftrace_call_replace(rec->ip, ftrace_get_addr_new(rec));
246 break;
247
248 case FTRACE_UPDATE_MAKE_NOP:
249 new = ftrace_nop_replace();
250 break;
251 }
252
253 text_poke_queue((void *)rec->ip, new, MCOUNT_INSN_SIZE, NULL);
254 ftrace_update_record(rec, enable);
255 }
256 text_poke_finish();
257}
258
259void arch_ftrace_update_code(int command)
260{
261 ftrace_modify_all_code(command);
262}
263
264/* Currently only x86_64 supports dynamic trampolines */
265#ifdef CONFIG_X86_64
266
267static inline void *alloc_tramp(unsigned long size)
268{
269 return execmem_alloc(EXECMEM_FTRACE, size);
270}
271static inline void tramp_free(void *tramp)
272{
273 execmem_free(tramp);
274}
275
276/* Defined as markers to the end of the ftrace default trampolines */
277extern void ftrace_regs_caller_end(void);
278extern void ftrace_caller_end(void);
279extern void ftrace_caller_op_ptr(void);
280extern void ftrace_regs_caller_op_ptr(void);
281extern void ftrace_regs_caller_jmp(void);
282
283/* movq function_trace_op(%rip), %rdx */
284/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
285#define OP_REF_SIZE 7
286
287/*
288 * The ftrace_ops is passed to the function callback. Since the
289 * trampoline only services a single ftrace_ops, we can pass in
290 * that ops directly.
291 *
292 * The ftrace_op_code_union is used to create a pointer to the
293 * ftrace_ops that will be passed to the callback function.
294 */
295union ftrace_op_code_union {
296 char code[OP_REF_SIZE];
297 struct {
298 char op[3];
299 int offset;
300 } __attribute__((packed));
301};
302
303#define RET_SIZE \
304 (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_MITIGATION_SLS))
305
306static unsigned long
307create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
308{
309 unsigned long start_offset;
310 unsigned long end_offset;
311 unsigned long op_offset;
312 unsigned long call_offset;
313 unsigned long jmp_offset;
314 unsigned long offset;
315 unsigned long npages;
316 unsigned long size;
317 unsigned long *ptr;
318 void *trampoline;
319 void *ip, *dest;
320 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
321 unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
322 unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE };
323 union ftrace_op_code_union op_ptr;
324 void *ret;
325
326 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
327 start_offset = (unsigned long)ftrace_regs_caller;
328 end_offset = (unsigned long)ftrace_regs_caller_end;
329 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
330 call_offset = (unsigned long)ftrace_regs_call;
331 jmp_offset = (unsigned long)ftrace_regs_caller_jmp;
332 } else {
333 start_offset = (unsigned long)ftrace_caller;
334 end_offset = (unsigned long)ftrace_caller_end;
335 op_offset = (unsigned long)ftrace_caller_op_ptr;
336 call_offset = (unsigned long)ftrace_call;
337 jmp_offset = 0;
338 }
339
340 size = end_offset - start_offset;
341
342 /*
343 * Allocate enough size to store the ftrace_caller code,
344 * the iret , as well as the address of the ftrace_ops this
345 * trampoline is used for.
346 */
347 trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
348 if (!trampoline)
349 return 0;
350
351 *tramp_size = size + RET_SIZE + sizeof(void *);
352 npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
353
354 /* Copy ftrace_caller onto the trampoline memory */
355 ret = text_poke_copy(trampoline, (void *)start_offset, size);
356 if (WARN_ON(!ret))
357 goto fail;
358
359 ip = trampoline + size;
360 if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
361 __text_gen_insn(ip, JMP32_INSN_OPCODE, ip, x86_return_thunk, JMP32_INSN_SIZE);
362 else
363 text_poke_copy(ip, retq, sizeof(retq));
364
365 /* No need to test direct calls on created trampolines */
366 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
367 /* NOP the jnz 1f; but make sure it's a 2 byte jnz */
368 ip = trampoline + (jmp_offset - start_offset);
369 if (WARN_ON(*(char *)ip != 0x75))
370 goto fail;
371 if (!text_poke_copy(ip, x86_nops[2], 2))
372 goto fail;
373 }
374
375 /*
376 * The address of the ftrace_ops that is used for this trampoline
377 * is stored at the end of the trampoline. This will be used to
378 * load the third parameter for the callback. Basically, that
379 * location at the end of the trampoline takes the place of
380 * the global function_trace_op variable.
381 */
382
383 ptr = (unsigned long *)(trampoline + size + RET_SIZE);
384 text_poke_copy(ptr, &ops, sizeof(unsigned long));
385
386 op_offset -= start_offset;
387 memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
388
389 /* Are we pointing to the reference? */
390 if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
391 goto fail;
392
393 /* Load the contents of ptr into the callback parameter */
394 offset = (unsigned long)ptr;
395 offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
396
397 op_ptr.offset = offset;
398
399 /* put in the new offset to the ftrace_ops */
400 text_poke_copy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
401
402 /* put in the call to the function */
403 mutex_lock(&text_mutex);
404 call_offset -= start_offset;
405 /*
406 * No need to translate into a callthunk. The trampoline does
407 * the depth accounting before the call already.
408 */
409 dest = ftrace_ops_get_func(ops);
410 text_poke_copy_locked(trampoline + call_offset,
411 text_gen_insn(CALL_INSN_OPCODE, trampoline + call_offset, dest),
412 CALL_INSN_SIZE, false);
413 mutex_unlock(&text_mutex);
414
415 /* ALLOC_TRAMP flags lets us know we created it */
416 ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
417
418 set_memory_rox((unsigned long)trampoline, npages);
419 return (unsigned long)trampoline;
420fail:
421 tramp_free(trampoline);
422 return 0;
423}
424
425void set_ftrace_ops_ro(void)
426{
427 struct ftrace_ops *ops;
428 unsigned long start_offset;
429 unsigned long end_offset;
430 unsigned long npages;
431 unsigned long size;
432
433 do_for_each_ftrace_op(ops, ftrace_ops_list) {
434 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
435 continue;
436
437 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
438 start_offset = (unsigned long)ftrace_regs_caller;
439 end_offset = (unsigned long)ftrace_regs_caller_end;
440 } else {
441 start_offset = (unsigned long)ftrace_caller;
442 end_offset = (unsigned long)ftrace_caller_end;
443 }
444 size = end_offset - start_offset;
445 size = size + RET_SIZE + sizeof(void *);
446 npages = DIV_ROUND_UP(size, PAGE_SIZE);
447 set_memory_ro((unsigned long)ops->trampoline, npages);
448 } while_for_each_ftrace_op(ops);
449}
450
451static unsigned long calc_trampoline_call_offset(bool save_regs)
452{
453 unsigned long start_offset;
454 unsigned long call_offset;
455
456 if (save_regs) {
457 start_offset = (unsigned long)ftrace_regs_caller;
458 call_offset = (unsigned long)ftrace_regs_call;
459 } else {
460 start_offset = (unsigned long)ftrace_caller;
461 call_offset = (unsigned long)ftrace_call;
462 }
463
464 return call_offset - start_offset;
465}
466
467void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
468{
469 ftrace_func_t func;
470 unsigned long offset;
471 unsigned long ip;
472 unsigned int size;
473 const char *new;
474
475 if (!ops->trampoline) {
476 ops->trampoline = create_trampoline(ops, &size);
477 if (!ops->trampoline)
478 return;
479 ops->trampoline_size = size;
480 return;
481 }
482
483 /*
484 * The ftrace_ops caller may set up its own trampoline.
485 * In such a case, this code must not modify it.
486 */
487 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
488 return;
489
490 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
491 ip = ops->trampoline + offset;
492 func = ftrace_ops_get_func(ops);
493
494 mutex_lock(&text_mutex);
495 /* Do a safe modify in case the trampoline is executing */
496 new = ftrace_call_replace(ip, (unsigned long)func);
497 text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
498 mutex_unlock(&text_mutex);
499}
500
501/* Return the address of the function the trampoline calls */
502static void *addr_from_call(void *ptr)
503{
504 union text_poke_insn call;
505 int ret;
506
507 ret = copy_from_kernel_nofault(&call, ptr, CALL_INSN_SIZE);
508 if (WARN_ON_ONCE(ret < 0))
509 return NULL;
510
511 /* Make sure this is a call */
512 if (WARN_ON_ONCE(call.opcode != CALL_INSN_OPCODE)) {
513 pr_warn("Expected E8, got %x\n", call.opcode);
514 return NULL;
515 }
516
517 return ptr + CALL_INSN_SIZE + call.disp;
518}
519
520/*
521 * If the ops->trampoline was not allocated, then it probably
522 * has a static trampoline func, or is the ftrace caller itself.
523 */
524static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
525{
526 unsigned long offset;
527 bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
528 void *ptr;
529
530 if (ops && ops->trampoline) {
531#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) && \
532 defined(CONFIG_FUNCTION_GRAPH_TRACER)
533 /*
534 * We only know about function graph tracer setting as static
535 * trampoline.
536 */
537 if (ops->trampoline == FTRACE_GRAPH_ADDR)
538 return (void *)prepare_ftrace_return;
539#endif
540 return NULL;
541 }
542
543 offset = calc_trampoline_call_offset(save_regs);
544
545 if (save_regs)
546 ptr = (void *)FTRACE_REGS_ADDR + offset;
547 else
548 ptr = (void *)FTRACE_ADDR + offset;
549
550 return addr_from_call(ptr);
551}
552
553void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
554{
555 unsigned long offset;
556
557 /* If we didn't allocate this trampoline, consider it static */
558 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
559 return static_tramp_func(ops, rec);
560
561 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
562 return addr_from_call((void *)ops->trampoline + offset);
563}
564
565void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
566{
567 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
568 return;
569
570 tramp_free((void *)ops->trampoline);
571 ops->trampoline = 0;
572}
573
574#endif /* CONFIG_X86_64 */
575#endif /* CONFIG_DYNAMIC_FTRACE */
576
577#ifdef CONFIG_FUNCTION_GRAPH_TRACER
578
579#if defined(CONFIG_DYNAMIC_FTRACE) && !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS)
580extern void ftrace_graph_call(void);
581static const char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
582{
583 return text_gen_insn(JMP32_INSN_OPCODE, (void *)ip, (void *)addr);
584}
585
586static int ftrace_mod_jmp(unsigned long ip, void *func)
587{
588 const char *new;
589
590 new = ftrace_jmp_replace(ip, (unsigned long)func);
591 text_poke_bp((void *)ip, new, MCOUNT_INSN_SIZE, NULL);
592 return 0;
593}
594
595int ftrace_enable_ftrace_graph_caller(void)
596{
597 unsigned long ip = (unsigned long)(&ftrace_graph_call);
598
599 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
600}
601
602int ftrace_disable_ftrace_graph_caller(void)
603{
604 unsigned long ip = (unsigned long)(&ftrace_graph_call);
605
606 return ftrace_mod_jmp(ip, &ftrace_stub);
607}
608#endif /* CONFIG_DYNAMIC_FTRACE && !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
609
610/*
611 * Hook the return address and push it in the stack of return addrs
612 * in current thread info.
613 */
614void prepare_ftrace_return(unsigned long ip, unsigned long *parent,
615 unsigned long frame_pointer)
616{
617 unsigned long return_hooker = (unsigned long)&return_to_handler;
618 int bit;
619
620 /*
621 * When resuming from suspend-to-ram, this function can be indirectly
622 * called from early CPU startup code while the CPU is in real mode,
623 * which would fail miserably. Make sure the stack pointer is a
624 * virtual address.
625 *
626 * This check isn't as accurate as virt_addr_valid(), but it should be
627 * good enough for this purpose, and it's fast.
628 */
629 if (unlikely((long)__builtin_frame_address(0) >= 0))
630 return;
631
632 if (unlikely(ftrace_graph_is_dead()))
633 return;
634
635 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
636 return;
637
638 bit = ftrace_test_recursion_trylock(ip, *parent);
639 if (bit < 0)
640 return;
641
642 if (!function_graph_enter(*parent, ip, frame_pointer, parent))
643 *parent = return_hooker;
644
645 ftrace_test_recursion_unlock(bit);
646}
647
648#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
649void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
650 struct ftrace_ops *op, struct ftrace_regs *fregs)
651{
652 struct pt_regs *regs = &arch_ftrace_regs(fregs)->regs;
653 unsigned long *stack = (unsigned long *)kernel_stack_pointer(regs);
654
655 prepare_ftrace_return(ip, (unsigned long *)stack, 0);
656}
657#endif
658
659#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Dynamic function tracing support.
4 *
5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
6 *
7 * Thanks goes to Ingo Molnar, for suggesting the idea.
8 * Mathieu Desnoyers, for suggesting postponing the modifications.
9 * Arjan van de Ven, for keeping me straight, and explaining to me
10 * the dangers of modifying code on the run.
11 */
12
13#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
14
15#include <linux/spinlock.h>
16#include <linux/hardirq.h>
17#include <linux/uaccess.h>
18#include <linux/ftrace.h>
19#include <linux/percpu.h>
20#include <linux/sched.h>
21#include <linux/slab.h>
22#include <linux/init.h>
23#include <linux/list.h>
24#include <linux/module.h>
25#include <linux/memory.h>
26
27#include <trace/syscall.h>
28
29#include <asm/set_memory.h>
30#include <asm/kprobes.h>
31#include <asm/ftrace.h>
32#include <asm/nops.h>
33#include <asm/text-patching.h>
34
35#ifdef CONFIG_DYNAMIC_FTRACE
36
37int ftrace_arch_code_modify_prepare(void)
38 __acquires(&text_mutex)
39{
40 /*
41 * Need to grab text_mutex to prevent a race from module loading
42 * and live kernel patching from changing the text permissions while
43 * ftrace has it set to "read/write".
44 */
45 mutex_lock(&text_mutex);
46 set_kernel_text_rw();
47 set_all_modules_text_rw();
48 return 0;
49}
50
51int ftrace_arch_code_modify_post_process(void)
52 __releases(&text_mutex)
53{
54 set_all_modules_text_ro();
55 set_kernel_text_ro();
56 mutex_unlock(&text_mutex);
57 return 0;
58}
59
60union ftrace_code_union {
61 char code[MCOUNT_INSN_SIZE];
62 struct {
63 unsigned char op;
64 int offset;
65 } __attribute__((packed));
66};
67
68static int ftrace_calc_offset(long ip, long addr)
69{
70 return (int)(addr - ip);
71}
72
73static unsigned char *
74ftrace_text_replace(unsigned char op, unsigned long ip, unsigned long addr)
75{
76 static union ftrace_code_union calc;
77
78 calc.op = op;
79 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
80
81 return calc.code;
82}
83
84static unsigned char *
85ftrace_call_replace(unsigned long ip, unsigned long addr)
86{
87 return ftrace_text_replace(0xe8, ip, addr);
88}
89
90static inline int
91within(unsigned long addr, unsigned long start, unsigned long end)
92{
93 return addr >= start && addr < end;
94}
95
96static unsigned long text_ip_addr(unsigned long ip)
97{
98 /*
99 * On x86_64, kernel text mappings are mapped read-only, so we use
100 * the kernel identity mapping instead of the kernel text mapping
101 * to modify the kernel text.
102 *
103 * For 32bit kernels, these mappings are same and we can use
104 * kernel identity mapping to modify code.
105 */
106 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
107 ip = (unsigned long)__va(__pa_symbol(ip));
108
109 return ip;
110}
111
112static const unsigned char *ftrace_nop_replace(void)
113{
114 return ideal_nops[NOP_ATOMIC5];
115}
116
117static int
118ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
119 unsigned const char *new_code)
120{
121 unsigned char replaced[MCOUNT_INSN_SIZE];
122
123 ftrace_expected = old_code;
124
125 /*
126 * Note:
127 * We are paranoid about modifying text, as if a bug was to happen, it
128 * could cause us to read or write to someplace that could cause harm.
129 * Carefully read and modify the code with probe_kernel_*(), and make
130 * sure what we read is what we expected it to be before modifying it.
131 */
132
133 /* read the text we want to modify */
134 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
135 return -EFAULT;
136
137 /* Make sure it is what we expect it to be */
138 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
139 return -EINVAL;
140
141 ip = text_ip_addr(ip);
142
143 /* replace the text with the new text */
144 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
145 return -EPERM;
146
147 sync_core();
148
149 return 0;
150}
151
152int ftrace_make_nop(struct module *mod,
153 struct dyn_ftrace *rec, unsigned long addr)
154{
155 unsigned const char *new, *old;
156 unsigned long ip = rec->ip;
157
158 old = ftrace_call_replace(ip, addr);
159 new = ftrace_nop_replace();
160
161 /*
162 * On boot up, and when modules are loaded, the MCOUNT_ADDR
163 * is converted to a nop, and will never become MCOUNT_ADDR
164 * again. This code is either running before SMP (on boot up)
165 * or before the code will ever be executed (module load).
166 * We do not want to use the breakpoint version in this case,
167 * just modify the code directly.
168 */
169 if (addr == MCOUNT_ADDR)
170 return ftrace_modify_code_direct(rec->ip, old, new);
171
172 ftrace_expected = NULL;
173
174 /* Normal cases use add_brk_on_nop */
175 WARN_ONCE(1, "invalid use of ftrace_make_nop");
176 return -EINVAL;
177}
178
179int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
180{
181 unsigned const char *new, *old;
182 unsigned long ip = rec->ip;
183
184 old = ftrace_nop_replace();
185 new = ftrace_call_replace(ip, addr);
186
187 /* Should only be called when module is loaded */
188 return ftrace_modify_code_direct(rec->ip, old, new);
189}
190
191/*
192 * The modifying_ftrace_code is used to tell the breakpoint
193 * handler to call ftrace_int3_handler(). If it fails to
194 * call this handler for a breakpoint added by ftrace, then
195 * the kernel may crash.
196 *
197 * As atomic_writes on x86 do not need a barrier, we do not
198 * need to add smp_mb()s for this to work. It is also considered
199 * that we can not read the modifying_ftrace_code before
200 * executing the breakpoint. That would be quite remarkable if
201 * it could do that. Here's the flow that is required:
202 *
203 * CPU-0 CPU-1
204 *
205 * atomic_inc(mfc);
206 * write int3s
207 * <trap-int3> // implicit (r)mb
208 * if (atomic_read(mfc))
209 * call ftrace_int3_handler()
210 *
211 * Then when we are finished:
212 *
213 * atomic_dec(mfc);
214 *
215 * If we hit a breakpoint that was not set by ftrace, it does not
216 * matter if ftrace_int3_handler() is called or not. It will
217 * simply be ignored. But it is crucial that a ftrace nop/caller
218 * breakpoint is handled. No other user should ever place a
219 * breakpoint on an ftrace nop/caller location. It must only
220 * be done by this code.
221 */
222atomic_t modifying_ftrace_code __read_mostly;
223
224static int
225ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
226 unsigned const char *new_code);
227
228/*
229 * Should never be called:
230 * As it is only called by __ftrace_replace_code() which is called by
231 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
232 * which is called to turn mcount into nops or nops into function calls
233 * but not to convert a function from not using regs to one that uses
234 * regs, which ftrace_modify_call() is for.
235 */
236int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
237 unsigned long addr)
238{
239 WARN_ON(1);
240 ftrace_expected = NULL;
241 return -EINVAL;
242}
243
244static unsigned long ftrace_update_func;
245static unsigned long ftrace_update_func_call;
246
247static int update_ftrace_func(unsigned long ip, void *new)
248{
249 unsigned char old[MCOUNT_INSN_SIZE];
250 int ret;
251
252 memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
253
254 ftrace_update_func = ip;
255 /* Make sure the breakpoints see the ftrace_update_func update */
256 smp_wmb();
257
258 /* See comment above by declaration of modifying_ftrace_code */
259 atomic_inc(&modifying_ftrace_code);
260
261 ret = ftrace_modify_code(ip, old, new);
262
263 atomic_dec(&modifying_ftrace_code);
264
265 return ret;
266}
267
268int ftrace_update_ftrace_func(ftrace_func_t func)
269{
270 unsigned long ip = (unsigned long)(&ftrace_call);
271 unsigned char *new;
272 int ret;
273
274 ftrace_update_func_call = (unsigned long)func;
275
276 new = ftrace_call_replace(ip, (unsigned long)func);
277 ret = update_ftrace_func(ip, new);
278
279 /* Also update the regs callback function */
280 if (!ret) {
281 ip = (unsigned long)(&ftrace_regs_call);
282 new = ftrace_call_replace(ip, (unsigned long)func);
283 ret = update_ftrace_func(ip, new);
284 }
285
286 return ret;
287}
288
289static nokprobe_inline int is_ftrace_caller(unsigned long ip)
290{
291 if (ip == ftrace_update_func)
292 return 1;
293
294 return 0;
295}
296
297/*
298 * A breakpoint was added to the code address we are about to
299 * modify, and this is the handle that will just skip over it.
300 * We are either changing a nop into a trace call, or a trace
301 * call to a nop. While the change is taking place, we treat
302 * it just like it was a nop.
303 */
304int ftrace_int3_handler(struct pt_regs *regs)
305{
306 unsigned long ip;
307
308 if (WARN_ON_ONCE(!regs))
309 return 0;
310
311 ip = regs->ip - INT3_INSN_SIZE;
312
313 if (ftrace_location(ip)) {
314 int3_emulate_call(regs, (unsigned long)ftrace_regs_caller);
315 return 1;
316 } else if (is_ftrace_caller(ip)) {
317 if (!ftrace_update_func_call) {
318 int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);
319 return 1;
320 }
321 int3_emulate_call(regs, ftrace_update_func_call);
322 return 1;
323 }
324
325 return 0;
326}
327NOKPROBE_SYMBOL(ftrace_int3_handler);
328
329static int ftrace_write(unsigned long ip, const char *val, int size)
330{
331 ip = text_ip_addr(ip);
332
333 if (probe_kernel_write((void *)ip, val, size))
334 return -EPERM;
335
336 return 0;
337}
338
339static int add_break(unsigned long ip, const char *old)
340{
341 unsigned char replaced[MCOUNT_INSN_SIZE];
342 unsigned char brk = BREAKPOINT_INSTRUCTION;
343
344 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
345 return -EFAULT;
346
347 ftrace_expected = old;
348
349 /* Make sure it is what we expect it to be */
350 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
351 return -EINVAL;
352
353 return ftrace_write(ip, &brk, 1);
354}
355
356static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
357{
358 unsigned const char *old;
359 unsigned long ip = rec->ip;
360
361 old = ftrace_call_replace(ip, addr);
362
363 return add_break(rec->ip, old);
364}
365
366
367static int add_brk_on_nop(struct dyn_ftrace *rec)
368{
369 unsigned const char *old;
370
371 old = ftrace_nop_replace();
372
373 return add_break(rec->ip, old);
374}
375
376static int add_breakpoints(struct dyn_ftrace *rec, bool enable)
377{
378 unsigned long ftrace_addr;
379 int ret;
380
381 ftrace_addr = ftrace_get_addr_curr(rec);
382
383 ret = ftrace_test_record(rec, enable);
384
385 switch (ret) {
386 case FTRACE_UPDATE_IGNORE:
387 return 0;
388
389 case FTRACE_UPDATE_MAKE_CALL:
390 /* converting nop to call */
391 return add_brk_on_nop(rec);
392
393 case FTRACE_UPDATE_MODIFY_CALL:
394 case FTRACE_UPDATE_MAKE_NOP:
395 /* converting a call to a nop */
396 return add_brk_on_call(rec, ftrace_addr);
397 }
398 return 0;
399}
400
401/*
402 * On error, we need to remove breakpoints. This needs to
403 * be done caefully. If the address does not currently have a
404 * breakpoint, we know we are done. Otherwise, we look at the
405 * remaining 4 bytes of the instruction. If it matches a nop
406 * we replace the breakpoint with the nop. Otherwise we replace
407 * it with the call instruction.
408 */
409static int remove_breakpoint(struct dyn_ftrace *rec)
410{
411 unsigned char ins[MCOUNT_INSN_SIZE];
412 unsigned char brk = BREAKPOINT_INSTRUCTION;
413 const unsigned char *nop;
414 unsigned long ftrace_addr;
415 unsigned long ip = rec->ip;
416
417 /* If we fail the read, just give up */
418 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
419 return -EFAULT;
420
421 /* If this does not have a breakpoint, we are done */
422 if (ins[0] != brk)
423 return 0;
424
425 nop = ftrace_nop_replace();
426
427 /*
428 * If the last 4 bytes of the instruction do not match
429 * a nop, then we assume that this is a call to ftrace_addr.
430 */
431 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
432 /*
433 * For extra paranoidism, we check if the breakpoint is on
434 * a call that would actually jump to the ftrace_addr.
435 * If not, don't touch the breakpoint, we make just create
436 * a disaster.
437 */
438 ftrace_addr = ftrace_get_addr_new(rec);
439 nop = ftrace_call_replace(ip, ftrace_addr);
440
441 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
442 goto update;
443
444 /* Check both ftrace_addr and ftrace_old_addr */
445 ftrace_addr = ftrace_get_addr_curr(rec);
446 nop = ftrace_call_replace(ip, ftrace_addr);
447
448 ftrace_expected = nop;
449
450 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
451 return -EINVAL;
452 }
453
454 update:
455 return ftrace_write(ip, nop, 1);
456}
457
458static int add_update_code(unsigned long ip, unsigned const char *new)
459{
460 /* skip breakpoint */
461 ip++;
462 new++;
463 return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
464}
465
466static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
467{
468 unsigned long ip = rec->ip;
469 unsigned const char *new;
470
471 new = ftrace_call_replace(ip, addr);
472 return add_update_code(ip, new);
473}
474
475static int add_update_nop(struct dyn_ftrace *rec)
476{
477 unsigned long ip = rec->ip;
478 unsigned const char *new;
479
480 new = ftrace_nop_replace();
481 return add_update_code(ip, new);
482}
483
484static int add_update(struct dyn_ftrace *rec, bool enable)
485{
486 unsigned long ftrace_addr;
487 int ret;
488
489 ret = ftrace_test_record(rec, enable);
490
491 ftrace_addr = ftrace_get_addr_new(rec);
492
493 switch (ret) {
494 case FTRACE_UPDATE_IGNORE:
495 return 0;
496
497 case FTRACE_UPDATE_MODIFY_CALL:
498 case FTRACE_UPDATE_MAKE_CALL:
499 /* converting nop to call */
500 return add_update_call(rec, ftrace_addr);
501
502 case FTRACE_UPDATE_MAKE_NOP:
503 /* converting a call to a nop */
504 return add_update_nop(rec);
505 }
506
507 return 0;
508}
509
510static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
511{
512 unsigned long ip = rec->ip;
513 unsigned const char *new;
514
515 new = ftrace_call_replace(ip, addr);
516
517 return ftrace_write(ip, new, 1);
518}
519
520static int finish_update_nop(struct dyn_ftrace *rec)
521{
522 unsigned long ip = rec->ip;
523 unsigned const char *new;
524
525 new = ftrace_nop_replace();
526
527 return ftrace_write(ip, new, 1);
528}
529
530static int finish_update(struct dyn_ftrace *rec, bool enable)
531{
532 unsigned long ftrace_addr;
533 int ret;
534
535 ret = ftrace_update_record(rec, enable);
536
537 ftrace_addr = ftrace_get_addr_new(rec);
538
539 switch (ret) {
540 case FTRACE_UPDATE_IGNORE:
541 return 0;
542
543 case FTRACE_UPDATE_MODIFY_CALL:
544 case FTRACE_UPDATE_MAKE_CALL:
545 /* converting nop to call */
546 return finish_update_call(rec, ftrace_addr);
547
548 case FTRACE_UPDATE_MAKE_NOP:
549 /* converting a call to a nop */
550 return finish_update_nop(rec);
551 }
552
553 return 0;
554}
555
556static void do_sync_core(void *data)
557{
558 sync_core();
559}
560
561static void run_sync(void)
562{
563 int enable_irqs;
564
565 /* No need to sync if there's only one CPU */
566 if (num_online_cpus() == 1)
567 return;
568
569 enable_irqs = irqs_disabled();
570
571 /* We may be called with interrupts disabled (on bootup). */
572 if (enable_irqs)
573 local_irq_enable();
574 on_each_cpu(do_sync_core, NULL, 1);
575 if (enable_irqs)
576 local_irq_disable();
577}
578
579void ftrace_replace_code(int enable)
580{
581 struct ftrace_rec_iter *iter;
582 struct dyn_ftrace *rec;
583 const char *report = "adding breakpoints";
584 int count = 0;
585 int ret;
586
587 for_ftrace_rec_iter(iter) {
588 rec = ftrace_rec_iter_record(iter);
589
590 ret = add_breakpoints(rec, enable);
591 if (ret)
592 goto remove_breakpoints;
593 count++;
594 }
595
596 run_sync();
597
598 report = "updating code";
599 count = 0;
600
601 for_ftrace_rec_iter(iter) {
602 rec = ftrace_rec_iter_record(iter);
603
604 ret = add_update(rec, enable);
605 if (ret)
606 goto remove_breakpoints;
607 count++;
608 }
609
610 run_sync();
611
612 report = "removing breakpoints";
613 count = 0;
614
615 for_ftrace_rec_iter(iter) {
616 rec = ftrace_rec_iter_record(iter);
617
618 ret = finish_update(rec, enable);
619 if (ret)
620 goto remove_breakpoints;
621 count++;
622 }
623
624 run_sync();
625
626 return;
627
628 remove_breakpoints:
629 pr_warn("Failed on %s (%d):\n", report, count);
630 ftrace_bug(ret, rec);
631 for_ftrace_rec_iter(iter) {
632 rec = ftrace_rec_iter_record(iter);
633 /*
634 * Breakpoints are handled only when this function is in
635 * progress. The system could not work with them.
636 */
637 if (remove_breakpoint(rec))
638 BUG();
639 }
640 run_sync();
641}
642
643static int
644ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
645 unsigned const char *new_code)
646{
647 int ret;
648
649 ret = add_break(ip, old_code);
650 if (ret)
651 goto out;
652
653 run_sync();
654
655 ret = add_update_code(ip, new_code);
656 if (ret)
657 goto fail_update;
658
659 run_sync();
660
661 ret = ftrace_write(ip, new_code, 1);
662 /*
663 * The breakpoint is handled only when this function is in progress.
664 * The system could not work if we could not remove it.
665 */
666 BUG_ON(ret);
667 out:
668 run_sync();
669 return ret;
670
671 fail_update:
672 /* Also here the system could not work with the breakpoint */
673 if (ftrace_write(ip, old_code, 1))
674 BUG();
675 goto out;
676}
677
678void arch_ftrace_update_code(int command)
679{
680 /* See comment above by declaration of modifying_ftrace_code */
681 atomic_inc(&modifying_ftrace_code);
682
683 ftrace_modify_all_code(command);
684
685 atomic_dec(&modifying_ftrace_code);
686}
687
688int __init ftrace_dyn_arch_init(void)
689{
690 return 0;
691}
692
693/* Currently only x86_64 supports dynamic trampolines */
694#ifdef CONFIG_X86_64
695
696#ifdef CONFIG_MODULES
697#include <linux/moduleloader.h>
698/* Module allocation simplifies allocating memory for code */
699static inline void *alloc_tramp(unsigned long size)
700{
701 return module_alloc(size);
702}
703static inline void tramp_free(void *tramp)
704{
705 module_memfree(tramp);
706}
707#else
708/* Trampolines can only be created if modules are supported */
709static inline void *alloc_tramp(unsigned long size)
710{
711 return NULL;
712}
713static inline void tramp_free(void *tramp) { }
714#endif
715
716/* Defined as markers to the end of the ftrace default trampolines */
717extern void ftrace_regs_caller_end(void);
718extern void ftrace_epilogue(void);
719extern void ftrace_caller_op_ptr(void);
720extern void ftrace_regs_caller_op_ptr(void);
721
722/* movq function_trace_op(%rip), %rdx */
723/* 0x48 0x8b 0x15 <offset-to-ftrace_trace_op (4 bytes)> */
724#define OP_REF_SIZE 7
725
726/*
727 * The ftrace_ops is passed to the function callback. Since the
728 * trampoline only services a single ftrace_ops, we can pass in
729 * that ops directly.
730 *
731 * The ftrace_op_code_union is used to create a pointer to the
732 * ftrace_ops that will be passed to the callback function.
733 */
734union ftrace_op_code_union {
735 char code[OP_REF_SIZE];
736 struct {
737 char op[3];
738 int offset;
739 } __attribute__((packed));
740};
741
742#define RET_SIZE 1
743
744static unsigned long
745create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
746{
747 unsigned long start_offset;
748 unsigned long end_offset;
749 unsigned long op_offset;
750 unsigned long offset;
751 unsigned long npages;
752 unsigned long size;
753 unsigned long retq;
754 unsigned long *ptr;
755 void *trampoline;
756 void *ip;
757 /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */
758 unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 };
759 union ftrace_op_code_union op_ptr;
760 int ret;
761
762 if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
763 start_offset = (unsigned long)ftrace_regs_caller;
764 end_offset = (unsigned long)ftrace_regs_caller_end;
765 op_offset = (unsigned long)ftrace_regs_caller_op_ptr;
766 } else {
767 start_offset = (unsigned long)ftrace_caller;
768 end_offset = (unsigned long)ftrace_epilogue;
769 op_offset = (unsigned long)ftrace_caller_op_ptr;
770 }
771
772 size = end_offset - start_offset;
773
774 /*
775 * Allocate enough size to store the ftrace_caller code,
776 * the iret , as well as the address of the ftrace_ops this
777 * trampoline is used for.
778 */
779 trampoline = alloc_tramp(size + RET_SIZE + sizeof(void *));
780 if (!trampoline)
781 return 0;
782
783 *tramp_size = size + RET_SIZE + sizeof(void *);
784 npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
785
786 /* Copy ftrace_caller onto the trampoline memory */
787 ret = probe_kernel_read(trampoline, (void *)start_offset, size);
788 if (WARN_ON(ret < 0))
789 goto fail;
790
791 ip = trampoline + size;
792
793 /* The trampoline ends with ret(q) */
794 retq = (unsigned long)ftrace_stub;
795 ret = probe_kernel_read(ip, (void *)retq, RET_SIZE);
796 if (WARN_ON(ret < 0))
797 goto fail;
798
799 /*
800 * The address of the ftrace_ops that is used for this trampoline
801 * is stored at the end of the trampoline. This will be used to
802 * load the third parameter for the callback. Basically, that
803 * location at the end of the trampoline takes the place of
804 * the global function_trace_op variable.
805 */
806
807 ptr = (unsigned long *)(trampoline + size + RET_SIZE);
808 *ptr = (unsigned long)ops;
809
810 op_offset -= start_offset;
811 memcpy(&op_ptr, trampoline + op_offset, OP_REF_SIZE);
812
813 /* Are we pointing to the reference? */
814 if (WARN_ON(memcmp(op_ptr.op, op_ref, 3) != 0))
815 goto fail;
816
817 /* Load the contents of ptr into the callback parameter */
818 offset = (unsigned long)ptr;
819 offset -= (unsigned long)trampoline + op_offset + OP_REF_SIZE;
820
821 op_ptr.offset = offset;
822
823 /* put in the new offset to the ftrace_ops */
824 memcpy(trampoline + op_offset, &op_ptr, OP_REF_SIZE);
825
826 /* ALLOC_TRAMP flags lets us know we created it */
827 ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
828
829 set_vm_flush_reset_perms(trampoline);
830
831 /*
832 * Module allocation needs to be completed by making the page
833 * executable. The page is still writable, which is a security hazard,
834 * but anyhow ftrace breaks W^X completely.
835 */
836 set_memory_x((unsigned long)trampoline, npages);
837 return (unsigned long)trampoline;
838fail:
839 tramp_free(trampoline);
840 return 0;
841}
842
843static unsigned long calc_trampoline_call_offset(bool save_regs)
844{
845 unsigned long start_offset;
846 unsigned long call_offset;
847
848 if (save_regs) {
849 start_offset = (unsigned long)ftrace_regs_caller;
850 call_offset = (unsigned long)ftrace_regs_call;
851 } else {
852 start_offset = (unsigned long)ftrace_caller;
853 call_offset = (unsigned long)ftrace_call;
854 }
855
856 return call_offset - start_offset;
857}
858
859void arch_ftrace_update_trampoline(struct ftrace_ops *ops)
860{
861 ftrace_func_t func;
862 unsigned char *new;
863 unsigned long offset;
864 unsigned long ip;
865 unsigned int size;
866 int ret, npages;
867
868 if (ops->trampoline) {
869 /*
870 * The ftrace_ops caller may set up its own trampoline.
871 * In such a case, this code must not modify it.
872 */
873 if (!(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
874 return;
875 npages = PAGE_ALIGN(ops->trampoline_size) >> PAGE_SHIFT;
876 set_memory_rw(ops->trampoline, npages);
877 } else {
878 ops->trampoline = create_trampoline(ops, &size);
879 if (!ops->trampoline)
880 return;
881 ops->trampoline_size = size;
882 npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
883 }
884
885 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
886 ip = ops->trampoline + offset;
887
888 func = ftrace_ops_get_func(ops);
889
890 ftrace_update_func_call = (unsigned long)func;
891
892 /* Do a safe modify in case the trampoline is executing */
893 new = ftrace_call_replace(ip, (unsigned long)func);
894 ret = update_ftrace_func(ip, new);
895 set_memory_ro(ops->trampoline, npages);
896
897 /* The update should never fail */
898 WARN_ON(ret);
899}
900
901/* Return the address of the function the trampoline calls */
902static void *addr_from_call(void *ptr)
903{
904 union ftrace_code_union calc;
905 int ret;
906
907 ret = probe_kernel_read(&calc, ptr, MCOUNT_INSN_SIZE);
908 if (WARN_ON_ONCE(ret < 0))
909 return NULL;
910
911 /* Make sure this is a call */
912 if (WARN_ON_ONCE(calc.op != 0xe8)) {
913 pr_warn("Expected e8, got %x\n", calc.op);
914 return NULL;
915 }
916
917 return ptr + MCOUNT_INSN_SIZE + calc.offset;
918}
919
920void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
921 unsigned long frame_pointer);
922
923/*
924 * If the ops->trampoline was not allocated, then it probably
925 * has a static trampoline func, or is the ftrace caller itself.
926 */
927static void *static_tramp_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
928{
929 unsigned long offset;
930 bool save_regs = rec->flags & FTRACE_FL_REGS_EN;
931 void *ptr;
932
933 if (ops && ops->trampoline) {
934#ifdef CONFIG_FUNCTION_GRAPH_TRACER
935 /*
936 * We only know about function graph tracer setting as static
937 * trampoline.
938 */
939 if (ops->trampoline == FTRACE_GRAPH_ADDR)
940 return (void *)prepare_ftrace_return;
941#endif
942 return NULL;
943 }
944
945 offset = calc_trampoline_call_offset(save_regs);
946
947 if (save_regs)
948 ptr = (void *)FTRACE_REGS_ADDR + offset;
949 else
950 ptr = (void *)FTRACE_ADDR + offset;
951
952 return addr_from_call(ptr);
953}
954
955void *arch_ftrace_trampoline_func(struct ftrace_ops *ops, struct dyn_ftrace *rec)
956{
957 unsigned long offset;
958
959 /* If we didn't allocate this trampoline, consider it static */
960 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
961 return static_tramp_func(ops, rec);
962
963 offset = calc_trampoline_call_offset(ops->flags & FTRACE_OPS_FL_SAVE_REGS);
964 return addr_from_call((void *)ops->trampoline + offset);
965}
966
967void arch_ftrace_trampoline_free(struct ftrace_ops *ops)
968{
969 if (!ops || !(ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP))
970 return;
971
972 tramp_free((void *)ops->trampoline);
973 ops->trampoline = 0;
974}
975
976#endif /* CONFIG_X86_64 */
977#endif /* CONFIG_DYNAMIC_FTRACE */
978
979#ifdef CONFIG_FUNCTION_GRAPH_TRACER
980
981#ifdef CONFIG_DYNAMIC_FTRACE
982extern void ftrace_graph_call(void);
983
984static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
985{
986 return ftrace_text_replace(0xe9, ip, addr);
987}
988
989static int ftrace_mod_jmp(unsigned long ip, void *func)
990{
991 unsigned char *new;
992
993 ftrace_update_func_call = 0UL;
994 new = ftrace_jmp_replace(ip, (unsigned long)func);
995
996 return update_ftrace_func(ip, new);
997}
998
999int ftrace_enable_ftrace_graph_caller(void)
1000{
1001 unsigned long ip = (unsigned long)(&ftrace_graph_call);
1002
1003 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
1004}
1005
1006int ftrace_disable_ftrace_graph_caller(void)
1007{
1008 unsigned long ip = (unsigned long)(&ftrace_graph_call);
1009
1010 return ftrace_mod_jmp(ip, &ftrace_stub);
1011}
1012
1013#endif /* !CONFIG_DYNAMIC_FTRACE */
1014
1015/*
1016 * Hook the return address and push it in the stack of return addrs
1017 * in current thread info.
1018 */
1019void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
1020 unsigned long frame_pointer)
1021{
1022 unsigned long old;
1023 int faulted;
1024 unsigned long return_hooker = (unsigned long)
1025 &return_to_handler;
1026
1027 /*
1028 * When resuming from suspend-to-ram, this function can be indirectly
1029 * called from early CPU startup code while the CPU is in real mode,
1030 * which would fail miserably. Make sure the stack pointer is a
1031 * virtual address.
1032 *
1033 * This check isn't as accurate as virt_addr_valid(), but it should be
1034 * good enough for this purpose, and it's fast.
1035 */
1036 if (unlikely((long)__builtin_frame_address(0) >= 0))
1037 return;
1038
1039 if (unlikely(ftrace_graph_is_dead()))
1040 return;
1041
1042 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
1043 return;
1044
1045 /*
1046 * Protect against fault, even if it shouldn't
1047 * happen. This tool is too much intrusive to
1048 * ignore such a protection.
1049 */
1050 asm volatile(
1051 "1: " _ASM_MOV " (%[parent]), %[old]\n"
1052 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
1053 " movl $0, %[faulted]\n"
1054 "3:\n"
1055
1056 ".section .fixup, \"ax\"\n"
1057 "4: movl $1, %[faulted]\n"
1058 " jmp 3b\n"
1059 ".previous\n"
1060
1061 _ASM_EXTABLE(1b, 4b)
1062 _ASM_EXTABLE(2b, 4b)
1063
1064 : [old] "=&r" (old), [faulted] "=r" (faulted)
1065 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
1066 : "memory"
1067 );
1068
1069 if (unlikely(faulted)) {
1070 ftrace_graph_stop();
1071 WARN_ON(1);
1072 return;
1073 }
1074
1075 if (function_graph_enter(old, self_addr, frame_pointer, parent))
1076 *parent = old;
1077}
1078#endif /* CONFIG_FUNCTION_GRAPH_TRACER */