~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/arch/x86/kernel/ftrace.c

Version: ~ [ linux-5.4-rc7 ] ~ [ linux-5.3.10 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.83 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.153 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.200 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.200 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.76 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Code for replacing ftrace calls with jumps.
  3  *
  4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
  5  *
  6  * Thanks goes to Ingo Molnar, for suggesting the idea.
  7  * Mathieu Desnoyers, for suggesting postponing the modifications.
  8  * Arjan van de Ven, for keeping me straight, and explaining to me
  9  * the dangers of modifying code on the run.
 10  */
 11 
 12 #include <linux/spinlock.h>
 13 #include <linux/hardirq.h>
 14 #include <linux/uaccess.h>
 15 #include <linux/ftrace.h>
 16 #include <linux/percpu.h>
 17 #include <linux/sched.h>
 18 #include <linux/init.h>
 19 #include <linux/list.h>
 20 
 21 #include <trace/syscall.h>
 22 
 23 #include <asm/cacheflush.h>
 24 #include <asm/ftrace.h>
 25 #include <asm/nops.h>
 26 #include <asm/nmi.h>
 27 
 28 
 29 #ifdef CONFIG_DYNAMIC_FTRACE
 30 
 31 int ftrace_arch_code_modify_prepare(void)
 32 {
 33         set_kernel_text_rw();
 34         return 0;
 35 }
 36 
 37 int ftrace_arch_code_modify_post_process(void)
 38 {
 39         set_kernel_text_ro();
 40         return 0;
 41 }
 42 
 43 union ftrace_code_union {
 44         char code[MCOUNT_INSN_SIZE];
 45         struct {
 46                 char e8;
 47                 int offset;
 48         } __attribute__((packed));
 49 };
 50 
 51 static int ftrace_calc_offset(long ip, long addr)
 52 {
 53         return (int)(addr - ip);
 54 }
 55 
 56 static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
 57 {
 58         static union ftrace_code_union calc;
 59 
 60         calc.e8         = 0xe8;
 61         calc.offset     = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
 62 
 63         /*
 64          * No locking needed, this must be called via kstop_machine
 65          * which in essence is like running on a uniprocessor machine.
 66          */
 67         return calc.code;
 68 }
 69 
 70 /*
 71  * Modifying code must take extra care. On an SMP machine, if
 72  * the code being modified is also being executed on another CPU
 73  * that CPU will have undefined results and possibly take a GPF.
 74  * We use kstop_machine to stop other CPUS from exectuing code.
 75  * But this does not stop NMIs from happening. We still need
 76  * to protect against that. We separate out the modification of
 77  * the code to take care of this.
 78  *
 79  * Two buffers are added: An IP buffer and a "code" buffer.
 80  *
 81  * 1) Put the instruction pointer into the IP buffer
 82  *    and the new code into the "code" buffer.
 83  * 2) Wait for any running NMIs to finish and set a flag that says
 84  *    we are modifying code, it is done in an atomic operation.
 85  * 3) Write the code
 86  * 4) clear the flag.
 87  * 5) Wait for any running NMIs to finish.
 88  *
 89  * If an NMI is executed, the first thing it does is to call
 90  * "ftrace_nmi_enter". This will check if the flag is set to write
 91  * and if it is, it will write what is in the IP and "code" buffers.
 92  *
 93  * The trick is, it does not matter if everyone is writing the same
 94  * content to the code location. Also, if a CPU is executing code
 95  * it is OK to write to that code location if the contents being written
 96  * are the same as what exists.
 97  */
 98 
 99 #define MOD_CODE_WRITE_FLAG (1 << 31)   /* set when NMI should do the write */
100 static atomic_t nmi_running = ATOMIC_INIT(0);
101 static int mod_code_status;             /* holds return value of text write */
102 static void *mod_code_ip;               /* holds the IP to write to */
103 static void *mod_code_newcode;          /* holds the text to write to the IP */
104 
105 static unsigned nmi_wait_count;
106 static atomic_t nmi_update_count = ATOMIC_INIT(0);
107 
108 int ftrace_arch_read_dyn_info(char *buf, int size)
109 {
110         int r;
111 
112         r = snprintf(buf, size, "%u %u",
113                      nmi_wait_count,
114                      atomic_read(&nmi_update_count));
115         return r;
116 }
117 
118 static void clear_mod_flag(void)
119 {
120         int old = atomic_read(&nmi_running);
121 
122         for (;;) {
123                 int new = old & ~MOD_CODE_WRITE_FLAG;
124 
125                 if (old == new)
126                         break;
127 
128                 old = atomic_cmpxchg(&nmi_running, old, new);
129         }
130 }
131 
132 static void ftrace_mod_code(void)
133 {
134         /*
135          * Yes, more than one CPU process can be writing to mod_code_status.
136          *    (and the code itself)
137          * But if one were to fail, then they all should, and if one were
138          * to succeed, then they all should.
139          */
140         mod_code_status = probe_kernel_write(mod_code_ip, mod_code_newcode,
141                                              MCOUNT_INSN_SIZE);
142 
143         /* if we fail, then kill any new writers */
144         if (mod_code_status)
145                 clear_mod_flag();
146 }
147 
148 void ftrace_nmi_enter(void)
149 {
150         if (atomic_inc_return(&nmi_running) & MOD_CODE_WRITE_FLAG) {
151                 smp_rmb();
152                 ftrace_mod_code();
153                 atomic_inc(&nmi_update_count);
154         }
155         /* Must have previous changes seen before executions */
156         smp_mb();
157 }
158 
159 void ftrace_nmi_exit(void)
160 {
161         /* Finish all executions before clearing nmi_running */
162         smp_mb();
163         atomic_dec(&nmi_running);
164 }
165 
166 static void wait_for_nmi_and_set_mod_flag(void)
167 {
168         if (!atomic_cmpxchg(&nmi_running, 0, MOD_CODE_WRITE_FLAG))
169                 return;
170 
171         do {
172                 cpu_relax();
173         } while (atomic_cmpxchg(&nmi_running, 0, MOD_CODE_WRITE_FLAG));
174 
175         nmi_wait_count++;
176 }
177 
178 static void wait_for_nmi(void)
179 {
180         if (!atomic_read(&nmi_running))
181                 return;
182 
183         do {
184                 cpu_relax();
185         } while (atomic_read(&nmi_running));
186 
187         nmi_wait_count++;
188 }
189 
190 static int
191 do_ftrace_mod_code(unsigned long ip, void *new_code)
192 {
193         mod_code_ip = (void *)ip;
194         mod_code_newcode = new_code;
195 
196         /* The buffers need to be visible before we let NMIs write them */
197         smp_mb();
198 
199         wait_for_nmi_and_set_mod_flag();
200 
201         /* Make sure all running NMIs have finished before we write the code */
202         smp_mb();
203 
204         ftrace_mod_code();
205 
206         /* Make sure the write happens before clearing the bit */
207         smp_mb();
208 
209         clear_mod_flag();
210         wait_for_nmi();
211 
212         return mod_code_status;
213 }
214 
215 
216 
217 
218 static unsigned char ftrace_nop[MCOUNT_INSN_SIZE];
219 
220 static unsigned char *ftrace_nop_replace(void)
221 {
222         return ftrace_nop;
223 }
224 
225 static int
226 ftrace_modify_code(unsigned long ip, unsigned char *old_code,
227                    unsigned char *new_code)
228 {
229         unsigned char replaced[MCOUNT_INSN_SIZE];
230 
231         /*
232          * Note: Due to modules and __init, code can
233          *  disappear and change, we need to protect against faulting
234          *  as well as code changing. We do this by using the
235          *  probe_kernel_* functions.
236          *
237          * No real locking needed, this code is run through
238          * kstop_machine, or before SMP starts.
239          */
240 
241         /* read the text we want to modify */
242         if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
243                 return -EFAULT;
244 
245         /* Make sure it is what we expect it to be */
246         if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
247                 return -EINVAL;
248 
249         /* replace the text with the new text */
250         if (do_ftrace_mod_code(ip, new_code))
251                 return -EPERM;
252 
253         sync_core();
254 
255         return 0;
256 }
257 
258 int ftrace_make_nop(struct module *mod,
259                     struct dyn_ftrace *rec, unsigned long addr)
260 {
261         unsigned char *new, *old;
262         unsigned long ip = rec->ip;
263 
264         old = ftrace_call_replace(ip, addr);
265         new = ftrace_nop_replace();
266 
267         return ftrace_modify_code(rec->ip, old, new);
268 }
269 
270 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
271 {
272         unsigned char *new, *old;
273         unsigned long ip = rec->ip;
274 
275         old = ftrace_nop_replace();
276         new = ftrace_call_replace(ip, addr);
277 
278         return ftrace_modify_code(rec->ip, old, new);
279 }
280 
281 int ftrace_update_ftrace_func(ftrace_func_t func)
282 {
283         unsigned long ip = (unsigned long)(&ftrace_call);
284         unsigned char old[MCOUNT_INSN_SIZE], *new;
285         int ret;
286 
287         memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
288         new = ftrace_call_replace(ip, (unsigned long)func);
289         ret = ftrace_modify_code(ip, old, new);
290 
291         return ret;
292 }
293 
294 int __init ftrace_dyn_arch_init(void *data)
295 {
296         extern const unsigned char ftrace_test_p6nop[];
297         extern const unsigned char ftrace_test_nop5[];
298         extern const unsigned char ftrace_test_jmp[];
299         int faulted = 0;
300 
301         /*
302          * There is no good nop for all x86 archs.
303          * We will default to using the P6_NOP5, but first we
304          * will test to make sure that the nop will actually
305          * work on this CPU. If it faults, we will then
306          * go to a lesser efficient 5 byte nop. If that fails
307          * we then just use a jmp as our nop. This isn't the most
308          * efficient nop, but we can not use a multi part nop
309          * since we would then risk being preempted in the middle
310          * of that nop, and if we enabled tracing then, it might
311          * cause a system crash.
312          *
313          * TODO: check the cpuid to determine the best nop.
314          */
315         asm volatile (
316                 "ftrace_test_jmp:"
317                 "jmp ftrace_test_p6nop\n"
318                 "nop\n"
319                 "nop\n"
320                 "nop\n"  /* 2 byte jmp + 3 bytes */
321                 "ftrace_test_p6nop:"
322                 P6_NOP5
323                 "jmp 1f\n"
324                 "ftrace_test_nop5:"
325                 ".byte 0x66,0x66,0x66,0x66,0x90\n"
326                 "1:"
327                 ".section .fixup, \"ax\"\n"
328                 "2:     movl $1, %0\n"
329                 "       jmp ftrace_test_nop5\n"
330                 "3:     movl $2, %0\n"
331                 "       jmp 1b\n"
332                 ".previous\n"
333                 _ASM_EXTABLE(ftrace_test_p6nop, 2b)
334                 _ASM_EXTABLE(ftrace_test_nop5, 3b)
335                 : "=r"(faulted) : "" (faulted));
336 
337         switch (faulted) {
338         case 0:
339                 pr_info("ftrace: converting mcount calls to 0f 1f 44 00 00\n");
340                 memcpy(ftrace_nop, ftrace_test_p6nop, MCOUNT_INSN_SIZE);
341                 break;
342         case 1:
343                 pr_info("ftrace: converting mcount calls to 66 66 66 66 90\n");
344                 memcpy(ftrace_nop, ftrace_test_nop5, MCOUNT_INSN_SIZE);
345                 break;
346         case 2:
347                 pr_info("ftrace: converting mcount calls to jmp . + 5\n");
348                 memcpy(ftrace_nop, ftrace_test_jmp, MCOUNT_INSN_SIZE);
349                 break;
350         }
351 
352         /* The return code is retured via data */
353         *(unsigned long *)data = 0;
354 
355         return 0;
356 }
357 #endif
358 
359 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
360 
361 #ifdef CONFIG_DYNAMIC_FTRACE
362 extern void ftrace_graph_call(void);
363 
364 static int ftrace_mod_jmp(unsigned long ip,
365                           int old_offset, int new_offset)
366 {
367         unsigned char code[MCOUNT_INSN_SIZE];
368 
369         if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
370                 return -EFAULT;
371 
372         if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))
373                 return -EINVAL;
374 
375         *(int *)(&code[1]) = new_offset;
376 
377         if (do_ftrace_mod_code(ip, &code))
378                 return -EPERM;
379 
380         return 0;
381 }
382 
383 int ftrace_enable_ftrace_graph_caller(void)
384 {
385         unsigned long ip = (unsigned long)(&ftrace_graph_call);
386         int old_offset, new_offset;
387 
388         old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
389         new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
390 
391         return ftrace_mod_jmp(ip, old_offset, new_offset);
392 }
393 
394 int ftrace_disable_ftrace_graph_caller(void)
395 {
396         unsigned long ip = (unsigned long)(&ftrace_graph_call);
397         int old_offset, new_offset;
398 
399         old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
400         new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
401 
402         return ftrace_mod_jmp(ip, old_offset, new_offset);
403 }
404 
405 #endif /* !CONFIG_DYNAMIC_FTRACE */
406 
407 /*
408  * Hook the return address and push it in the stack of return addrs
409  * in current thread info.
410  */
411 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
412                            unsigned long frame_pointer)
413 {
414         unsigned long old;
415         int faulted;
416         struct ftrace_graph_ent trace;
417         unsigned long return_hooker = (unsigned long)
418                                 &return_to_handler;
419 
420         if (unlikely(atomic_read(&current->tracing_graph_pause)))
421                 return;
422 
423         /*
424          * Protect against fault, even if it shouldn't
425          * happen. This tool is too much intrusive to
426          * ignore such a protection.
427          */
428         asm volatile(
429                 "1: " _ASM_MOV " (%[parent]), %[old]\n"
430                 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
431                 "   movl $0, %[faulted]\n"
432                 "3:\n"
433 
434                 ".section .fixup, \"ax\"\n"
435                 "4: movl $1, %[faulted]\n"
436                 "   jmp 3b\n"
437                 ".previous\n"
438 
439                 _ASM_EXTABLE(1b, 4b)
440                 _ASM_EXTABLE(2b, 4b)
441 
442                 : [old] "=&r" (old), [faulted] "=r" (faulted)
443                 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
444                 : "memory"
445         );
446 
447         if (unlikely(faulted)) {
448                 ftrace_graph_stop();
449                 WARN_ON(1);
450                 return;
451         }
452 
453         if (ftrace_push_return_trace(old, self_addr, &trace.depth,
454                     frame_pointer) == -EBUSY) {
455                 *parent = old;
456                 return;
457         }
458 
459         trace.func = self_addr;
460 
461         /* Only trace if the calling function expects to */
462         if (!ftrace_graph_entry(&trace)) {
463                 current->curr_ret_stack--;
464                 *parent = old;
465         }
466 }
467 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
468 
469 #ifdef CONFIG_FTRACE_SYSCALLS
470 
471 extern unsigned long __start_syscalls_metadata[];
472 extern unsigned long __stop_syscalls_metadata[];
473 extern unsigned long *sys_call_table;
474 
475 static struct syscall_metadata **syscalls_metadata;
476 
477 static struct syscall_metadata *find_syscall_meta(unsigned long *syscall)
478 {
479         struct syscall_metadata *start;
480         struct syscall_metadata *stop;
481         char str[KSYM_SYMBOL_LEN];
482 
483 
484         start = (struct syscall_metadata *)__start_syscalls_metadata;
485         stop = (struct syscall_metadata *)__stop_syscalls_metadata;
486         kallsyms_lookup((unsigned long) syscall, NULL, NULL, NULL, str);
487 
488         for ( ; start < stop; start++) {
489                 if (start->name && !strcmp(start->name, str))
490                         return start;
491         }
492         return NULL;
493 }
494 
495 struct syscall_metadata *syscall_nr_to_meta(int nr)
496 {
497         if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
498                 return NULL;
499 
500         return syscalls_metadata[nr];
501 }
502 
503 int syscall_name_to_nr(char *name)
504 {
505         int i;
506 
507         if (!syscalls_metadata)
508                 return -1;
509 
510         for (i = 0; i < NR_syscalls; i++) {
511                 if (syscalls_metadata[i]) {
512                         if (!strcmp(syscalls_metadata[i]->name, name))
513                                 return i;
514                 }
515         }
516         return -1;
517 }
518 
519 void set_syscall_enter_id(int num, int id)
520 {
521         syscalls_metadata[num]->enter_id = id;
522 }
523 
524 void set_syscall_exit_id(int num, int id)
525 {
526         syscalls_metadata[num]->exit_id = id;
527 }
528 
529 static int __init arch_init_ftrace_syscalls(void)
530 {
531         int i;
532         struct syscall_metadata *meta;
533         unsigned long **psys_syscall_table = &sys_call_table;
534 
535         syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
536                                         NR_syscalls, GFP_KERNEL);
537         if (!syscalls_metadata) {
538                 WARN_ON(1);
539                 return -ENOMEM;
540         }
541 
542         for (i = 0; i < NR_syscalls; i++) {
543                 meta = find_syscall_meta(psys_syscall_table[i]);
544                 syscalls_metadata[i] = meta;
545         }
546         return 0;
547 }
548 arch_initcall(arch_init_ftrace_syscalls);
549 #endif
550 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp