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(&current->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 */