src/drm-shim/drm_shim.c

   1 /*
   2  * Copyright © 2018 Broadcom
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 /**
  25  * @file
  26  *
  27  * Implements wrappers of libc functions to fake having a DRM device that
  28  * isn't actually present in the kernel.
  29  */
  30
  31 /* Prevent glibc from defining open64 when we want to alias it. */
  32 #undef _FILE_OFFSET_BITS
  33 #define _LARGEFILE64_SOURCE
  34
  35 #include <stdbool.h>
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40 #include <sys/ioctl.h>
  41 #include <sys/mman.h>
  42 #include <sys/stat.h>
  43 #include <sys/sysmacros.h>
  44 #include <stdarg.h>
  45 #include <fcntl.h>
  46 #include <dlfcn.h>
  47 #include <dirent.h>
  48 #include <c11/threads.h>
  49 #include <drm-uapi/drm.h>
  50
  51 #include "util/set.h"
  52 #include "util/u_debug.h"
  53 #include "drm_shim.h"
  54
  55 #define REAL_FUNCTION_POINTER(x) typeof(x) *real_##x
  56
  57 static mtx_t shim_lock = _MTX_INITIALIZER_NP;
  58 struct set *opendir_set;
  59 bool drm_shim_debug;
  60
  61 /* If /dev/dri doesn't exist, we'll need an arbitrary pointer that wouldn't be
  62  * returned by any other opendir() call so we can return just our fake node.
  63  */
  64 DIR *fake_dev_dri = (void *)&opendir_set;
  65
  66 /* XXX: implement REAL_FUNCTION_POINTER(close); */
  67 REAL_FUNCTION_POINTER(closedir);
  68 REAL_FUNCTION_POINTER(dup);
  69 REAL_FUNCTION_POINTER(fcntl);
  70 REAL_FUNCTION_POINTER(fopen);
  71 REAL_FUNCTION_POINTER(ioctl);
  72 REAL_FUNCTION_POINTER(mmap);
  73 REAL_FUNCTION_POINTER(open);
  74 REAL_FUNCTION_POINTER(opendir);
  75 REAL_FUNCTION_POINTER(readdir);
  76 REAL_FUNCTION_POINTER(readdir64);
  77 REAL_FUNCTION_POINTER(readlink);
  78 REAL_FUNCTION_POINTER(__xstat);
  79 REAL_FUNCTION_POINTER(__xstat64);
  80 REAL_FUNCTION_POINTER(__fxstat);
  81 REAL_FUNCTION_POINTER(__fxstat64);
  82
  83 /* Full path of /dev/dri/renderD* */
  84 static char *render_node_path;
  85 /* renderD* */
  86 static char *render_node_dirent_name;
  87 /* /sys/dev/char/major:minor/device/subsystem */
  88 static char *subsystem_path;
  89 int render_node_minor = -1;
  90
  91 struct file_override {
  92    const char *path;
  93    char *contents;
  94 };
  95 static struct file_override file_overrides[10];
  96 static int file_overrides_count;
  97
  98 /* Come up with a filename for a render node that doesn't actually exist on
  99  * the system.
 100  */
 101 static void
 102 get_dri_render_node_minor(void)
 103 {
 104    for (int i = 0; i < 10; i++) {
 105       int minor = 128 + i;
 106       asprintf(&render_node_dirent_name, "renderD%d", minor);
 107       asprintf(&render_node_path, "/dev/dri/%s",
 108                render_node_dirent_name);
 109       struct stat st;
 110       if (stat(render_node_path, &st) == -1) {
 111
 112          render_node_minor = minor;
 113          return;
 114       }
 115    }
 116
 117    fprintf(stderr, "Couldn't find a spare render node slot\n");
 118 }
 119
 120 static void *get_function_pointer(const char *name)
 121 {
 122    void *func = dlsym(RTLD_NEXT, name);
 123    if (!func) {
 124       fprintf(stderr, "Failed to resolve %s\n", name);
 125       abort();
 126    }
 127    return func;
 128 }
 129
 130 #define GET_FUNCTION_POINTER(x) real_##x = get_function_pointer(#x)
 131
 132 void
 133 drm_shim_override_file(const char *contents, const char *path_format, ...)
 134 {
 135    assert(file_overrides_count < ARRAY_SIZE(file_overrides));
 136
 137    char *path;
 138    va_list ap;
 139    va_start(ap, path_format);
 140    vasprintf(&path, path_format, ap);
 141    va_end(ap);
 142
 143    struct file_override *override = &file_overrides[file_overrides_count++];
 144    override->path = path;
 145    override->contents = strdup(contents);
 146 }
 147
 148 static void
 149 destroy_shim(void)
 150 {
 151    _mesa_set_destroy(opendir_set, NULL);
 152    free(render_node_path);
 153    free(render_node_dirent_name);
 154    free(subsystem_path);
 155 }
 156
 157 /* Initialization, which will be called from the first general library call
 158  * that might need to be wrapped with the shim.
 159  */
 160 static void
 161 init_shim(void)
 162 {
 163    static bool inited = false;
 164    drm_shim_debug = debug_get_bool_option("DRM_SHIM_DEBUG", false);
 165
 166    /* We can't lock this, because we recurse during initialization. */
 167    if (inited)
 168       return;
 169
 170    /* This comes first (and we're locked), to make sure we don't recurse
 171     * during initialization.
 172     */
 173    inited = true;
 174
 175    opendir_set = _mesa_set_create(NULL,
 176                                   _mesa_hash_string,
 177                                   _mesa_key_string_equal);
 178
 179    GET_FUNCTION_POINTER(closedir);
 180    GET_FUNCTION_POINTER(dup);
 181    GET_FUNCTION_POINTER(fcntl);
 182    GET_FUNCTION_POINTER(fopen);
 183    GET_FUNCTION_POINTER(ioctl);
 184    GET_FUNCTION_POINTER(mmap);
 185    GET_FUNCTION_POINTER(open);
 186    GET_FUNCTION_POINTER(opendir);
 187    GET_FUNCTION_POINTER(readdir);
 188    GET_FUNCTION_POINTER(readdir64);
 189    GET_FUNCTION_POINTER(readlink);
 190    GET_FUNCTION_POINTER(__xstat);
 191    GET_FUNCTION_POINTER(__xstat64);
 192    GET_FUNCTION_POINTER(__fxstat);
 193    GET_FUNCTION_POINTER(__fxstat64);
 194
 195    get_dri_render_node_minor();
 196
 197    if (drm_shim_debug) {
 198       fprintf(stderr, "Initializing DRM shim on %s\n",
 199               render_node_path);
 200    }
 201
 202    asprintf(&subsystem_path,
 203             "/sys/dev/char/%d:%d/device/subsystem",
 204             DRM_MAJOR, render_node_minor);
 205
 206    drm_shim_device_init();
 207
 208    atexit(destroy_shim);
 209 }
 210
 211 /* Override libdrm's reading of various sysfs files for device enumeration. */
 212 PUBLIC FILE *fopen(const char *path, const char *mode)
 213 {
 214    init_shim();
 215
 216    for (int i = 0; i < file_overrides_count; i++) {
 217       if (strcmp(file_overrides[i].path, path) == 0) {
 218          int fds[2];
 219          pipe(fds);
 220          write(fds[1], file_overrides[i].contents,
 221                strlen(file_overrides[i].contents));
 222          return fdopen(fds[0], "r");
 223       }
 224    }
 225
 226    return real_fopen(path, mode);
 227 }
 228 PUBLIC FILE *fopen64(const char *path, const char *mode)
 229    __attribute__((alias("fopen")));
 230
 231 /* Intercepts open(render_node_path) to redirect it to the simulator. */
 232 PUBLIC int open(const char *path, int flags, ...)
 233 {
 234    init_shim();
 235
 236    va_list ap;
 237    va_start(ap, flags);
 238    mode_t mode = va_arg(ap, mode_t);
 239    va_end(ap);
 240
 241    if (strcmp(path, render_node_path) != 0)
 242       return real_open(path, flags, mode);
 243
 244    int fd = real_open("/dev/null", O_RDWR, 0);
 245
 246    drm_shim_fd_register(fd, NULL);
 247
 248    return fd;
 249 }
 250 PUBLIC int open64(const char*, int, ...) __attribute__((alias("open")));
 251
 252 /* Fakes stat to return character device stuff for our fake render node. */
 253 PUBLIC int __xstat(int ver, const char *path, struct stat *st)
 254 {
 255    init_shim();
 256
 257    /* Note: call real stat if we're in the process of probing for a free
 258     * render node!
 259     */
 260    if (render_node_minor == -1)
 261       return real___xstat(ver, path, st);
 262
 263    /* Fool libdrm's probe of whether the /sys dir for this char dev is
 264     * there.
 265     */
 266    char *sys_dev_drm_dir;
 267    asprintf(&sys_dev_drm_dir, "/sys/dev/char/%d:%d/device/drm",
 268             DRM_MAJOR, render_node_minor);
 269    if (strcmp(path, sys_dev_drm_dir) == 0) {
 270       free(sys_dev_drm_dir);
 271       return 0;
 272    }
 273    free(sys_dev_drm_dir);
 274
 275    if (strcmp(path, render_node_path) != 0)
 276       return real___xstat(ver, path, st);
 277
 278    memset(st, 0, sizeof(*st));
 279    st->st_rdev = makedev(DRM_MAJOR, render_node_minor);
 280    st->st_mode = S_IFCHR;
 281
 282    return 0;
 283 }
 284
 285 /* Fakes stat to return character device stuff for our fake render node. */
 286 PUBLIC int __xstat64(int ver, const char *path, struct stat64 *st)
 287 {
 288    init_shim();
 289
 290    /* Note: call real stat if we're in the process of probing for a free
 291     * render node!
 292     */
 293    if (render_node_minor == -1)
 294       return real___xstat64(ver, path, st);
 295
 296    /* Fool libdrm's probe of whether the /sys dir for this char dev is
 297     * there.
 298     */
 299    char *sys_dev_drm_dir;
 300    asprintf(&sys_dev_drm_dir, "/sys/dev/char/%d:%d/device/drm",
 301             DRM_MAJOR, render_node_minor);
 302    if (strcmp(path, sys_dev_drm_dir) == 0) {
 303       free(sys_dev_drm_dir);
 304       return 0;
 305    }
 306    free(sys_dev_drm_dir);
 307
 308    if (strcmp(path, render_node_path) != 0)
 309       return real___xstat64(ver, path, st);
 310
 311    memset(st, 0, sizeof(*st));
 312    st->st_rdev = makedev(DRM_MAJOR, render_node_minor);
 313    st->st_mode = S_IFCHR;
 314
 315    return 0;
 316 }
 317
 318 /* Fakes fstat to return character device stuff for our fake render node. */
 319 PUBLIC int __fxstat(int ver, int fd, struct stat *st)
 320 {
 321    init_shim();
 322
 323    struct shim_fd *shim_fd = drm_shim_fd_lookup(fd);
 324
 325    if (!shim_fd)
 326       return real___fxstat(ver, fd, st);
 327
 328    memset(st, 0, sizeof(*st));
 329    st->st_rdev = makedev(DRM_MAJOR, render_node_minor);
 330    st->st_mode = S_IFCHR;
 331
 332    return 0;
 333 }
 334
 335 PUBLIC int __fxstat64(int ver, int fd, struct stat64 *st)
 336 {
 337    init_shim();
 338
 339    struct shim_fd *shim_fd = drm_shim_fd_lookup(fd);
 340
 341    if (!shim_fd)
 342       return real___fxstat64(ver, fd, st);
 343
 344    memset(st, 0, sizeof(*st));
 345    st->st_rdev = makedev(DRM_MAJOR, render_node_minor);
 346    st->st_mode = S_IFCHR;
 347
 348    return 0;
 349 }
 350
 351 /* Tracks if the opendir was on /dev/dri. */
 352 PUBLIC DIR *
 353 opendir(const char *name)
 354 {
 355    init_shim();
 356
 357    DIR *dir = real_opendir(name);
 358    if (strcmp(name, "/dev/dri") == 0) {
 359       if (!dir) {
 360          /* If /dev/dri didn't exist, we still want to be able to return our
 361           * fake /dev/dri/render* even though we probably can't
 362           * mkdir("/dev/dri").  Return a fake DIR pointer for that.
 363           */
 364          dir = fake_dev_dri;
 365       }
 366
 367       mtx_lock(&shim_lock);
 368       _mesa_set_add(opendir_set, dir);
 369       mtx_unlock(&shim_lock);
 370    }
 371
 372    return dir;
 373 }
 374
 375 /* If we've reached the end of the real directory list and we're
 376  * looking at /dev/dri, add our render node to the list.
 377  */
 378 PUBLIC struct dirent *
 379 readdir(DIR *dir)
 380 {
 381    init_shim();
 382
 383    struct dirent *ent = NULL;
 384
 385    if (dir != fake_dev_dri)
 386       ent = real_readdir(dir);
 387    static struct dirent render_node_dirent = { 0 };
 388
 389    if (!ent) {
 390       mtx_lock(&shim_lock);
 391       if (_mesa_set_search(opendir_set, dir)) {
 392          strcpy(render_node_dirent.d_name,
 393                 render_node_dirent_name);
 394          ent = &render_node_dirent;
 395          _mesa_set_remove_key(opendir_set, dir);
 396       }
 397       mtx_unlock(&shim_lock);
 398    }
 399
 400    return ent;
 401 }
 402
 403 /* If we've reached the end of the real directory list and we're
 404  * looking at /dev/dri, add our render node to the list.
 405  */
 406 PUBLIC struct dirent64 *
 407 readdir64(DIR *dir)
 408 {
 409    init_shim();
 410
 411    struct dirent64 *ent = NULL;
 412    if (dir != fake_dev_dri)
 413       ent = real_readdir64(dir);
 414    static struct dirent64 render_node_dirent = { 0 };
 415
 416    if (!ent) {
 417       mtx_lock(&shim_lock);
 418       if (_mesa_set_search(opendir_set, dir)) {
 419          strcpy(render_node_dirent.d_name,
 420                 render_node_dirent_name);
 421          ent = &render_node_dirent;
 422          _mesa_set_remove_key(opendir_set, dir);
 423       }
 424       mtx_unlock(&shim_lock);
 425    }
 426
 427    return ent;
 428 }
 429
 430 /* Cleans up tracking of opendir("/dev/dri") */
 431 PUBLIC int
 432 closedir(DIR *dir)
 433 {
 434    init_shim();
 435
 436    mtx_lock(&shim_lock);
 437    _mesa_set_remove_key(opendir_set, dir);
 438    mtx_unlock(&shim_lock);
 439
 440    if (dir != fake_dev_dri)
 441       return real_closedir(dir);
 442    else
 443       return 0;
 444 }
 445
 446 /* Handles libdrm's readlink to figure out what kind of device we have. */
 447 PUBLIC ssize_t
 448 readlink(const char *path, char *buf, size_t size)
 449 {
 450    init_shim();
 451
 452    if (strcmp(path, subsystem_path) != 0)
 453       return real_readlink(path, buf, size);
 454    strncpy(buf, "/platform", size);
 455    buf[size - 1] = 0;
 456
 457    return strlen(buf) + 1;
 458 }
 459
 460 /* Main entrypoint to DRM drivers: the ioctl syscall.  We send all ioctls on
 461  * our DRM fd to drm_shim_ioctl().
 462  */
 463 PUBLIC int
 464 ioctl(int fd, unsigned long request, ...)
 465 {
 466    init_shim();
 467
 468    va_list ap;
 469    va_start(ap, request);
 470    void *arg = va_arg(ap, void *);
 471    va_end(ap);
 472
 473    struct shim_fd *shim_fd = drm_shim_fd_lookup(fd);
 474    if (!shim_fd)
 475       return real_ioctl(fd, request, arg);
 476
 477    return drm_shim_ioctl(fd, request, arg);
 478 }
 479
 480 /* Gallium uses this to dup the incoming fd on gbm screen creation */
 481 PUBLIC int
 482 fcntl(int fd, int cmd, ...)
 483 {
 484    init_shim();
 485
 486    struct shim_fd *shim_fd = drm_shim_fd_lookup(fd);
 487
 488    va_list ap;
 489    va_start(ap, cmd);
 490    void *arg = va_arg(ap, void *);
 491    va_end(ap);
 492
 493    int ret = real_fcntl(fd, cmd, arg);
 494
 495    if (shim_fd && (cmd == F_DUPFD || cmd == F_DUPFD_CLOEXEC))
 496       drm_shim_fd_register(ret, shim_fd);
 497
 498    return ret;
 499 }
 500 PUBLIC int fcntl64(int, int, ...)
 501    __attribute__((alias("fcntl")));
 502
 503 /* I wrote this when trying to fix gallium screen creation, leaving it around
 504  * since it's probably good to have.
 505  */
 506 PUBLIC int
 507 dup(int fd)
 508 {
 509    init_shim();
 510
 511    int ret = real_dup(fd);
 512
 513    struct shim_fd *shim_fd = drm_shim_fd_lookup(fd);
 514    if (shim_fd && ret >= 0)
 515       drm_shim_fd_register(ret, shim_fd);
 516
 517    return ret;
 518 }
 519
 520 PUBLIC void *
 521 mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
 522 {
 523    init_shim();
 524
 525    struct shim_fd *shim_fd = drm_shim_fd_lookup(fd);
 526    if (shim_fd)
 527       return drm_shim_mmap(shim_fd, length, prot, flags, fd, offset);
 528
 529    return real_mmap(addr, length, prot, flags, fd, offset);
 530 }
 531 PUBLIC void *mmap64(void*, size_t, int, int, int, off_t)
 532    __attribute__((alias("mmap")));