aboutsummaryrefslogtreecommitdiff
path: root/libffi/src/closures.c
blob: fecbc4ae2c9e7056e84c2561f6537e453ea7efc7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
/* -----------------------------------------------------------------------
   closures.c - Copyright (c) 2007, 2009, 2010  Red Hat, Inc.
                Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc
                Copyright (c) 2011 Plausible Labs Cooperative, Inc.

   Code to allocate and deallocate memory for closures.

   Permission is hereby granted, free of charge, to any person obtaining
   a copy of this software and associated documentation files (the
   ``Software''), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be included
   in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
   DEALINGS IN THE SOFTWARE.
   ----------------------------------------------------------------------- */

#if defined __linux__ && !defined _GNU_SOURCE
#define _GNU_SOURCE 1
#endif

#include <ffi.h>
#include <ffi_common.h>

#if !FFI_MMAP_EXEC_WRIT && !FFI_EXEC_TRAMPOLINE_TABLE
# if __gnu_linux__
/* This macro indicates it may be forbidden to map anonymous memory
   with both write and execute permission.  Code compiled when this
   option is defined will attempt to map such pages once, but if it
   fails, it falls back to creating a temporary file in a writable and
   executable filesystem and mapping pages from it into separate
   locations in the virtual memory space, one location writable and
   another executable.  */
#  define FFI_MMAP_EXEC_WRIT 1
#  define HAVE_MNTENT 1
# endif
# if defined(X86_WIN32) || defined(X86_WIN64) || defined(__OS2__)
/* Windows systems may have Data Execution Protection (DEP) enabled, 
   which requires the use of VirtualMalloc/VirtualFree to alloc/free
   executable memory. */
#  define FFI_MMAP_EXEC_WRIT 1
# endif
#endif

#if FFI_MMAP_EXEC_WRIT && !defined FFI_MMAP_EXEC_SELINUX
# ifdef __linux__
/* When defined to 1 check for SELinux and if SELinux is active,
   don't attempt PROT_EXEC|PROT_WRITE mapping at all, as that
   might cause audit messages.  */
#  define FFI_MMAP_EXEC_SELINUX 1
# endif
#endif

#if FFI_CLOSURES

# if FFI_EXEC_TRAMPOLINE_TABLE

// Per-target implementation; It's unclear what can reasonable be shared between two OS/architecture implementations.

# elif FFI_MMAP_EXEC_WRIT /* !FFI_EXEC_TRAMPOLINE_TABLE */

#define USE_LOCKS 1
#define USE_DL_PREFIX 1
#ifdef __GNUC__
#ifndef USE_BUILTIN_FFS
#define USE_BUILTIN_FFS 1
#endif
#endif

/* We need to use mmap, not sbrk.  */
#define HAVE_MORECORE 0

/* We could, in theory, support mremap, but it wouldn't buy us anything.  */
#define HAVE_MREMAP 0

/* We have no use for this, so save some code and data.  */
#define NO_MALLINFO 1

/* We need all allocations to be in regular segments, otherwise we
   lose track of the corresponding code address.  */
#define DEFAULT_MMAP_THRESHOLD MAX_SIZE_T

/* Don't allocate more than a page unless needed.  */
#define DEFAULT_GRANULARITY ((size_t)malloc_getpagesize)

#if FFI_CLOSURE_TEST
/* Don't release single pages, to avoid a worst-case scenario of
   continuously allocating and releasing single pages, but release
   pairs of pages, which should do just as well given that allocations
   are likely to be small.  */
#define DEFAULT_TRIM_THRESHOLD ((size_t)malloc_getpagesize)
#endif

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#ifndef _MSC_VER
#include <unistd.h>
#endif
#include <string.h>
#include <stdio.h>
#if !defined(X86_WIN32) && !defined(X86_WIN64)
#ifdef HAVE_MNTENT
#include <mntent.h>
#endif /* HAVE_MNTENT */
#include <sys/param.h>
#include <pthread.h>

/* We don't want sys/mman.h to be included after we redefine mmap and
   dlmunmap.  */
#include <sys/mman.h>
#define LACKS_SYS_MMAN_H 1

#if FFI_MMAP_EXEC_SELINUX
#include <sys/statfs.h>
#include <stdlib.h>

static int selinux_enabled = -1;

static int
selinux_enabled_check (void)
{
  struct statfs sfs;
  FILE *f;
  char *buf = NULL;
  size_t len = 0;

  if (statfs ("/selinux", &sfs) >= 0
      && (unsigned int) sfs.f_type == 0xf97cff8cU)
    return 1;
  f = fopen ("/proc/mounts", "r");
  if (f == NULL)
    return 0;
  while (getline (&buf, &len, f) >= 0)
    {
      char *p = strchr (buf, ' ');
      if (p == NULL)
        break;
      p = strchr (p + 1, ' ');
      if (p == NULL)
        break;
      if (strncmp (p + 1, "selinuxfs ", 10) == 0)
        {
          free (buf);
          fclose (f);
          return 1;
        }
    }
  free (buf);
  fclose (f);
  return 0;
}

#define is_selinux_enabled() (selinux_enabled >= 0 ? selinux_enabled \
			      : (selinux_enabled = selinux_enabled_check ()))

#else

#define is_selinux_enabled() 0

#endif /* !FFI_MMAP_EXEC_SELINUX */

/* On PaX enable kernels that have MPROTECT enable we can't use PROT_EXEC. */
#ifdef FFI_MMAP_EXEC_EMUTRAMP_PAX
#include <stdlib.h>

static int emutramp_enabled = -1;

static int
emutramp_enabled_check (void)
{
  if (getenv ("FFI_DISABLE_EMUTRAMP") == NULL)
    return 1;
  else
    return 0;
}

#define is_emutramp_enabled() (emutramp_enabled >= 0 ? emutramp_enabled \
                               : (emutramp_enabled = emutramp_enabled_check ()))
#else
#define is_emutramp_enabled() 0
#endif /* FFI_MMAP_EXEC_EMUTRAMP_PAX */

#elif defined (__CYGWIN__) || defined(__INTERIX)

#include <sys/mman.h>

/* Cygwin is Linux-like, but not quite that Linux-like.  */
#define is_selinux_enabled() 0

#endif /* !defined(X86_WIN32) && !defined(X86_WIN64) */

/* Declare all functions defined in dlmalloc.c as static.  */
static void *dlmalloc(size_t);
static void dlfree(void*);
static void *dlcalloc(size_t, size_t) MAYBE_UNUSED;
static void *dlrealloc(void *, size_t) MAYBE_UNUSED;
static void *dlmemalign(size_t, size_t) MAYBE_UNUSED;
static void *dlvalloc(size_t) MAYBE_UNUSED;
static int dlmallopt(int, int) MAYBE_UNUSED;
static size_t dlmalloc_footprint(void) MAYBE_UNUSED;
static size_t dlmalloc_max_footprint(void) MAYBE_UNUSED;
static void** dlindependent_calloc(size_t, size_t, void**) MAYBE_UNUSED;
static void** dlindependent_comalloc(size_t, size_t*, void**) MAYBE_UNUSED;
static void *dlpvalloc(size_t) MAYBE_UNUSED;
static int dlmalloc_trim(size_t) MAYBE_UNUSED;
static size_t dlmalloc_usable_size(void*) MAYBE_UNUSED;
static void dlmalloc_stats(void) MAYBE_UNUSED;

#if !(defined(X86_WIN32) || defined(X86_WIN64) || defined(__OS2__)) || defined (__CYGWIN__) || defined(__INTERIX)
/* Use these for mmap and munmap within dlmalloc.c.  */
static void *dlmmap(void *, size_t, int, int, int, off_t);
static int dlmunmap(void *, size_t);
#endif /* !(defined(X86_WIN32) || defined(X86_WIN64) || defined(__OS2__)) || defined (__CYGWIN__) || defined(__INTERIX) */

#define mmap dlmmap
#define munmap dlmunmap

#include "dlmalloc.c"

#undef mmap
#undef munmap

#if !(defined(X86_WIN32) || defined(X86_WIN64) || defined(__OS2__)) || defined (__CYGWIN__) || defined(__INTERIX)

/* A mutex used to synchronize access to *exec* variables in this file.  */
static pthread_mutex_t open_temp_exec_file_mutex = PTHREAD_MUTEX_INITIALIZER;

/* A file descriptor of a temporary file from which we'll map
   executable pages.  */
static int execfd = -1;

/* The amount of space already allocated from the temporary file.  */
static size_t execsize = 0;

/* Open a temporary file name, and immediately unlink it.  */
static int
open_temp_exec_file_name (char *name)
{
  int fd = mkstemp (name);

  if (fd != -1)
    unlink (name);

  return fd;
}

/* Open a temporary file in the named directory.  */
static int
open_temp_exec_file_dir (const char *dir)
{
  static const char suffix[] = "/ffiXXXXXX";
  int lendir = strlen (dir);
  char *tempname = __builtin_alloca (lendir + sizeof (suffix));

  if (!tempname)
    return -1;

  memcpy (tempname, dir, lendir);
  memcpy (tempname + lendir, suffix, sizeof (suffix));

  return open_temp_exec_file_name (tempname);
}

/* Open a temporary file in the directory in the named environment
   variable.  */
static int
open_temp_exec_file_env (const char *envvar)
{
  const char *value = getenv (envvar);

  if (!value)
    return -1;

  return open_temp_exec_file_dir (value);
}

#ifdef HAVE_MNTENT
/* Open a temporary file in an executable and writable mount point
   listed in the mounts file.  Subsequent calls with the same mounts
   keep searching for mount points in the same file.  Providing NULL
   as the mounts file closes the file.  */
static int
open_temp_exec_file_mnt (const char *mounts)
{
  static const char *last_mounts;
  static FILE *last_mntent;

  if (mounts != last_mounts)
    {
      if (last_mntent)
	endmntent (last_mntent);

      last_mounts = mounts;

      if (mounts)
	last_mntent = setmntent (mounts, "r");
      else
	last_mntent = NULL;
    }

  if (!last_mntent)
    return -1;

  for (;;)
    {
      int fd;
      struct mntent mnt;
      char buf[MAXPATHLEN * 3];

      if (getmntent_r (last_mntent, &mnt, buf, sizeof (buf)) == NULL)
	return -1;

      if (hasmntopt (&mnt, "ro")
	  || hasmntopt (&mnt, "noexec")
	  || access (mnt.mnt_dir, W_OK))
	continue;

      fd = open_temp_exec_file_dir (mnt.mnt_dir);

      if (fd != -1)
	return fd;
    }
}
#endif /* HAVE_MNTENT */

/* Instructions to look for a location to hold a temporary file that
   can be mapped in for execution.  */
static struct
{
  int (*func)(const char *);
  const char *arg;
  int repeat;
} open_temp_exec_file_opts[] = {
  { open_temp_exec_file_env, "TMPDIR", 0 },
  { open_temp_exec_file_dir, "/tmp", 0 },
  { open_temp_exec_file_dir, "/var/tmp", 0 },
  { open_temp_exec_file_dir, "/dev/shm", 0 },
  { open_temp_exec_file_env, "HOME", 0 },
#ifdef HAVE_MNTENT
  { open_temp_exec_file_mnt, "/etc/mtab", 1 },
  { open_temp_exec_file_mnt, "/proc/mounts", 1 },
#endif /* HAVE_MNTENT */
};

/* Current index into open_temp_exec_file_opts.  */
static int open_temp_exec_file_opts_idx = 0;

/* Reset a current multi-call func, then advances to the next entry.
   If we're at the last, go back to the first and return nonzero,
   otherwise return zero.  */
static int
open_temp_exec_file_opts_next (void)
{
  if (open_temp_exec_file_opts[open_temp_exec_file_opts_idx].repeat)
    open_temp_exec_file_opts[open_temp_exec_file_opts_idx].func (NULL);

  open_temp_exec_file_opts_idx++;
  if (open_temp_exec_file_opts_idx
      == (sizeof (open_temp_exec_file_opts)
	  / sizeof (*open_temp_exec_file_opts)))
    {
      open_temp_exec_file_opts_idx = 0;
      return 1;
    }

  return 0;
}

/* Return a file descriptor of a temporary zero-sized file in a
   writable and exexutable filesystem.  */
static int
open_temp_exec_file (void)
{
  int fd;

  do
    {
      fd = open_temp_exec_file_opts[open_temp_exec_file_opts_idx].func
	(open_temp_exec_file_opts[open_temp_exec_file_opts_idx].arg);

      if (!open_temp_exec_file_opts[open_temp_exec_file_opts_idx].repeat
	  || fd == -1)
	{
	  if (open_temp_exec_file_opts_next ())
	    break;
	}
    }
  while (fd == -1);

  return fd;
}

/* Map in a chunk of memory from the temporary exec file into separate
   locations in the virtual memory address space, one writable and one
   executable.  Returns the address of the writable portion, after
   storing an offset to the corresponding executable portion at the
   last word of the requested chunk.  */
static void *
dlmmap_locked (void *start, size_t length, int prot, int flags, off_t offset)
{
  void *ptr;

  if (execfd == -1)
    {
      open_temp_exec_file_opts_idx = 0;
    retry_open:
      execfd = open_temp_exec_file ();
      if (execfd == -1)
	return MFAIL;
    }

  offset = execsize;

  if (ftruncate (execfd, offset + length))
    return MFAIL;

  flags &= ~(MAP_PRIVATE | MAP_ANONYMOUS);
  flags |= MAP_SHARED;

  ptr = mmap (NULL, length, (prot & ~PROT_WRITE) | PROT_EXEC,
	      flags, execfd, offset);
  if (ptr == MFAIL)
    {
      if (!offset)
	{
	  close (execfd);
	  goto retry_open;
	}
      ftruncate (execfd, offset);
      return MFAIL;
    }
  else if (!offset
	   && open_temp_exec_file_opts[open_temp_exec_file_opts_idx].repeat)
    open_temp_exec_file_opts_next ();

  start = mmap (start, length, prot, flags, execfd, offset);

  if (start == MFAIL)
    {
      munmap (ptr, length);
      ftruncate (execfd, offset);
      return start;
    }

  mmap_exec_offset ((char *)start, length) = (char*)ptr - (char*)start;

  execsize += length;

  return start;
}

/* Map in a writable and executable chunk of memory if possible.
   Failing that, fall back to dlmmap_locked.  */
static void *
dlmmap (void *start, size_t length, int prot,
	int flags, int fd, off_t offset)
{
  void *ptr;

  assert (start == NULL && length % malloc_getpagesize == 0
	  && prot == (PROT_READ | PROT_WRITE)
	  && flags == (MAP_PRIVATE | MAP_ANONYMOUS)
	  && fd == -1 && offset == 0);

#if FFI_CLOSURE_TEST
  printf ("mapping in %zi\n", length);
#endif

  if (execfd == -1 && is_emutramp_enabled ())
    {
      ptr = mmap (start, length, prot & ~PROT_EXEC, flags, fd, offset);
      return ptr;
    }

  if (execfd == -1 && !is_selinux_enabled ())
    {
      ptr = mmap (start, length, prot | PROT_EXEC, flags, fd, offset);

      if (ptr != MFAIL || (errno != EPERM && errno != EACCES))
	/* Cool, no need to mess with separate segments.  */
	return ptr;

      /* If MREMAP_DUP is ever introduced and implemented, try mmap
	 with ((prot & ~PROT_WRITE) | PROT_EXEC) and mremap with
	 MREMAP_DUP and prot at this point.  */
    }

  if (execsize == 0 || execfd == -1)
    {
      pthread_mutex_lock (&open_temp_exec_file_mutex);
      ptr = dlmmap_locked (start, length, prot, flags, offset);
      pthread_mutex_unlock (&open_temp_exec_file_mutex);

      return ptr;
    }

  return dlmmap_locked (start, length, prot, flags, offset);
}

/* Release memory at the given address, as well as the corresponding
   executable page if it's separate.  */
static int
dlmunmap (void *start, size_t length)
{
  /* We don't bother decreasing execsize or truncating the file, since
     we can't quite tell whether we're unmapping the end of the file.
     We don't expect frequent deallocation anyway.  If we did, we
     could locate pages in the file by writing to the pages being
     deallocated and checking that the file contents change.
     Yuck.  */
  msegmentptr seg = segment_holding (gm, start);
  void *code;

#if FFI_CLOSURE_TEST
  printf ("unmapping %zi\n", length);
#endif

  if (seg && (code = add_segment_exec_offset (start, seg)) != start)
    {
      int ret = munmap (code, length);
      if (ret)
	return ret;
    }

  return munmap (start, length);
}

#if FFI_CLOSURE_FREE_CODE
/* Return segment holding given code address.  */
static msegmentptr
segment_holding_code (mstate m, char* addr)
{
  msegmentptr sp = &m->seg;
  for (;;) {
    if (addr >= add_segment_exec_offset (sp->base, sp)
	&& addr < add_segment_exec_offset (sp->base, sp) + sp->size)
      return sp;
    if ((sp = sp->next) == 0)
      return 0;
  }
}
#endif

#endif /* !(defined(X86_WIN32) || defined(X86_WIN64) || defined(__OS2__)) || defined (__CYGWIN__) || defined(__INTERIX) */

/* Allocate a chunk of memory with the given size.  Returns a pointer
   to the writable address, and sets *CODE to the executable
   corresponding virtual address.  */
void *
ffi_closure_alloc (size_t size, void **code)
{
  void *ptr;

  if (!code)
    return NULL;

  ptr = dlmalloc (size);

  if (ptr)
    {
      msegmentptr seg = segment_holding (gm, ptr);

      *code = add_segment_exec_offset (ptr, seg);
    }

  return ptr;
}

/* Release a chunk of memory allocated with ffi_closure_alloc.  If
   FFI_CLOSURE_FREE_CODE is nonzero, the given address can be the
   writable or the executable address given.  Otherwise, only the
   writable address can be provided here.  */
void
ffi_closure_free (void *ptr)
{
#if FFI_CLOSURE_FREE_CODE
  msegmentptr seg = segment_holding_code (gm, ptr);

  if (seg)
    ptr = sub_segment_exec_offset (ptr, seg);
#endif

  dlfree (ptr);
}


#if FFI_CLOSURE_TEST
/* Do some internal sanity testing to make sure allocation and
   deallocation of pages are working as intended.  */
int main ()
{
  void *p[3];
#define GET(idx, len) do { p[idx] = dlmalloc (len); printf ("allocated %zi for p[%i]\n", (len), (idx)); } while (0)
#define PUT(idx) do { printf ("freeing p[%i]\n", (idx)); dlfree (p[idx]); } while (0)
  GET (0, malloc_getpagesize / 2);
  GET (1, 2 * malloc_getpagesize - 64 * sizeof (void*));
  PUT (1);
  GET (1, 2 * malloc_getpagesize);
  GET (2, malloc_getpagesize / 2);
  PUT (1);
  PUT (0);
  PUT (2);
  return 0;
}
#endif /* FFI_CLOSURE_TEST */
# else /* ! FFI_MMAP_EXEC_WRIT */

/* On many systems, memory returned by malloc is writable and
   executable, so just use it.  */

#include <stdlib.h>

void *
ffi_closure_alloc (size_t size, void **code)
{
  if (!code)
    return NULL;

  return *code = malloc (size);
}

void
ffi_closure_free (void *ptr)
{
  free (ptr);
}

# endif /* ! FFI_MMAP_EXEC_WRIT */
#endif /* FFI_CLOSURES */