include/qemu/osdep.h

   1 /*
   2  * OS includes and handling of OS dependencies
   3  *
   4  * This header exists to pull in some common system headers that
   5  * most code in QEMU will want, and to fix up some possible issues with
   6  * it (missing defines, Windows weirdness, and so on).
   7  *
   8  * To avoid getting into possible circular include dependencies, this
   9  * file should not include any other QEMU headers, with the exceptions
  10  * of config-host.h, config-target.h, qemu/compiler.h,
  11  * sysemu/os-posix.h, sysemu/os-win32.h, glib-compat.h and
  12  * qemu/typedefs.h, all of which are doing a similar job to this file
  13  * and are under similar constraints.
  14  *
  15  * This header also contains prototypes for functions defined in
  16  * os-*.c and util/oslib-*.c; those would probably be better split
  17  * out into separate header files.
  18  *
  19  * In an ideal world this header would contain only:
  20  *  (1) things which everybody needs
  21  *  (2) things without which code would work on most platforms but
  22  *      fail to compile or misbehave on a minority of host OSes
  23  *
  24  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  25  * See the COPYING file in the top-level directory.
  26  */
  27 #ifndef QEMU_OSDEP_H
  28 #define QEMU_OSDEP_H
  29
  30 #include "config-host.h"
  31 #ifdef NEED_CPU_H
  32 #include CONFIG_TARGET
  33 #else
  34 #include "exec/poison.h"
  35 #endif
  36
  37 #include "qemu/compiler.h"
  38
  39 /* Older versions of C++ don't get definitions of various macros from
  40  * stdlib.h unless we define these macros before first inclusion of
  41  * that system header.
  42  */
  43 #ifndef __STDC_CONSTANT_MACROS
  44 #define __STDC_CONSTANT_MACROS
  45 #endif
  46 #ifndef __STDC_LIMIT_MACROS
  47 #define __STDC_LIMIT_MACROS
  48 #endif
  49 #ifndef __STDC_FORMAT_MACROS
  50 #define __STDC_FORMAT_MACROS
  51 #endif
  52
  53 /* The following block of code temporarily renames the daemon() function so the
  54  * compiler does not see the warning associated with it in stdlib.h on OSX
  55  */
  56 #ifdef __APPLE__
  57 #define daemon qemu_fake_daemon_function
  58 #include <stdlib.h>
  59 #undef daemon
  60 QEMU_EXTERN_C int daemon(int, int);
  61 #endif
  62
  63 #ifdef _WIN32
  64 /* as defined in sdkddkver.h */
  65 #ifndef _WIN32_WINNT
  66 #define _WIN32_WINNT 0x0600 /* Vista */
  67 #endif
  68 /* reduces the number of implicitly included headers */
  69 #ifndef WIN32_LEAN_AND_MEAN
  70 #define WIN32_LEAN_AND_MEAN
  71 #endif
  72 #endif
  73
  74 /* enable C99/POSIX format strings (needs mingw32-runtime 3.15 or later) */
  75 #ifdef __MINGW32__
  76 #define __USE_MINGW_ANSI_STDIO 1
  77 #endif
  78
  79 #include <stdarg.h>
  80 #include <stddef.h>
  81 #include <stdbool.h>
  82 #include <stdint.h>
  83 #include <sys/types.h>
  84 #include <stdlib.h>
  85 #include <stdio.h>
  86
  87 #include <string.h>
  88 #include <strings.h>
  89 #include <inttypes.h>
  90 #include <limits.h>
  91 /* Put unistd.h before time.h as that triggers localtime_r/gmtime_r
  92  * function availability on recentish Mingw-w64 platforms. */
  93 #include <unistd.h>
  94 #include <time.h>
  95 #include <ctype.h>
  96 #include <errno.h>
  97 #include <fcntl.h>
  98 #include <getopt.h>
  99 #include <sys/stat.h>
 100 #include <sys/time.h>
 101 #include <assert.h>
 102 /* setjmp must be declared before sysemu/os-win32.h
 103  * because it is redefined there. */
 104 #include <setjmp.h>
 105 #include <signal.h>
 106
 107 #ifdef CONFIG_IOVEC
 108 #include <sys/uio.h>
 109 #endif
 110
 111 #if defined(__linux__) && defined(__sparc__)
 112 /* The SPARC definition of QEMU_VMALLOC_ALIGN needs SHMLBA */
 113 #include <sys/shm.h>
 114 #endif
 115
 116 #ifndef _WIN32
 117 #include <sys/wait.h>
 118 #else
 119 #define WIFEXITED(x)   1
 120 #define WEXITSTATUS(x) (x)
 121 #endif
 122
 123 #ifdef __APPLE__
 124 #include <AvailabilityMacros.h>
 125 #endif
 126
 127 /*
 128  * This is somewhat like a system header; it must be outside any extern "C"
 129  * block because it includes system headers itself, including glib.h,
 130  * which will not compile if inside an extern "C" block.
 131  */
 132 #include "glib-compat.h"
 133
 134 #ifdef _WIN32
 135 #include "sysemu/os-win32.h"
 136 #endif
 137
 138 #ifdef CONFIG_POSIX
 139 #include "sysemu/os-posix.h"
 140 #endif
 141
 142 #ifdef __cplusplus
 143 extern "C" {
 144 #endif
 145
 146 #include "qemu/typedefs.h"
 147
 148 /*
 149  * For mingw, as of v6.0.0, the function implementing the assert macro is
 150  * not marked as noreturn, so the compiler cannot delete code following an
 151  * assert(false) as unused.  We rely on this within the code base to delete
 152  * code that is unreachable when features are disabled.
 153  * All supported versions of Glib's g_assert() satisfy this requirement.
 154  */
 155 #ifdef __MINGW32__
 156 #undef assert
 157 #define assert(x)  g_assert(x)
 158 #endif
 159
 160 /*
 161  * According to waitpid man page:
 162  * WCOREDUMP
 163  *  This  macro  is  not  specified  in POSIX.1-2001 and is not
 164  *  available on some UNIX implementations (e.g., AIX, SunOS).
 165  *  Therefore, enclose its use inside #ifdef WCOREDUMP ... #endif.
 166  */
 167 #ifndef WCOREDUMP
 168 #define WCOREDUMP(status) 0
 169 #endif
 170 /*
 171  * We have a lot of unaudited code that may fail in strange ways, or
 172  * even be a security risk during migration, if you disable assertions
 173  * at compile-time.  You may comment out these safety checks if you
 174  * absolutely want to disable assertion overhead, but it is not
 175  * supported upstream so the risk is all yours.  Meanwhile, please
 176  * submit patches to remove any side-effects inside an assertion, or
 177  * fixing error handling that should use Error instead of assert.
 178  */
 179 #ifdef NDEBUG
 180 #error building with NDEBUG is not supported
 181 #endif
 182 #ifdef G_DISABLE_ASSERT
 183 #error building with G_DISABLE_ASSERT is not supported
 184 #endif
 185
 186 #ifndef O_LARGEFILE
 187 #define O_LARGEFILE 0
 188 #endif
 189 #ifndef O_BINARY
 190 #define O_BINARY 0
 191 #endif
 192 #ifndef MAP_ANONYMOUS
 193 #define MAP_ANONYMOUS MAP_ANON
 194 #endif
 195 #ifndef MAP_FIXED_NOREPLACE
 196 #define MAP_FIXED_NOREPLACE 0
 197 #endif
 198 #ifndef MAP_NORESERVE
 199 #define MAP_NORESERVE 0
 200 #endif
 201 #ifndef ENOMEDIUM
 202 #define ENOMEDIUM ENODEV
 203 #endif
 204 #if !defined(ENOTSUP)
 205 #define ENOTSUP 4096
 206 #endif
 207 #if !defined(ECANCELED)
 208 #define ECANCELED 4097
 209 #endif
 210 #if !defined(EMEDIUMTYPE)
 211 #define EMEDIUMTYPE 4098
 212 #endif
 213 #if !defined(ESHUTDOWN)
 214 #define ESHUTDOWN 4099
 215 #endif
 216
 217 /* time_t may be either 32 or 64 bits depending on the host OS, and
 218  * can be either signed or unsigned, so we can't just hardcode a
 219  * specific maximum value. This is not a C preprocessor constant,
 220  * so you can't use TIME_MAX in an #ifdef, but for our purposes
 221  * this isn't a problem.
 222  */
 223
 224 /* The macros TYPE_SIGNED, TYPE_WIDTH, and TYPE_MAXIMUM are from
 225  * Gnulib, and are under the LGPL v2.1 or (at your option) any
 226  * later version.
 227  */
 228
 229 /* True if the real type T is signed.  */
 230 #define TYPE_SIGNED(t) (!((t)0 < (t)-1))
 231
 232 /* The width in bits of the integer type or expression T.
 233  * Padding bits are not supported.
 234  */
 235 #define TYPE_WIDTH(t) (sizeof(t) * CHAR_BIT)
 236
 237 /* The maximum and minimum values for the integer type T.  */
 238 #define TYPE_MAXIMUM(t)                                                \
 239   ((t) (!TYPE_SIGNED(t)                                                \
 240         ? (t)-1                                                        \
 241         : ((((t)1 << (TYPE_WIDTH(t) - 2)) - 1) * 2 + 1)))
 242
 243 #ifndef TIME_MAX
 244 #define TIME_MAX TYPE_MAXIMUM(time_t)
 245 #endif
 246
 247 /* HOST_LONG_BITS is the size of a native pointer in bits. */
 248 #if UINTPTR_MAX == UINT32_MAX
 249 # define HOST_LONG_BITS 32
 250 #elif UINTPTR_MAX == UINT64_MAX
 251 # define HOST_LONG_BITS 64
 252 #else
 253 # error Unknown pointer size
 254 #endif
 255
 256 /* Mac OSX has a <stdint.h> bug that incorrectly defines SIZE_MAX with
 257  * the wrong type. Our replacement isn't usable in preprocessor
 258  * expressions, but it is sufficient for our needs. */
 259 #ifdef HAVE_BROKEN_SIZE_MAX
 260 #undef SIZE_MAX
 261 #define SIZE_MAX ((size_t)-1)
 262 #endif
 263
 264 /*
 265  * Two variations of MIN/MAX macros. The first is for runtime use, and
 266  * evaluates arguments only once (so it is safe even with side
 267  * effects), but will not work in constant contexts (such as array
 268  * size declarations) because of the '{}'.  The second is for constant
 269  * expression use, where evaluating arguments twice is safe because
 270  * the result is going to be constant anyway, but will not work in a
 271  * runtime context because of a void expression where a value is
 272  * expected.  Thus, both gcc and clang will fail to compile if you use
 273  * the wrong macro (even if the error may seem a bit cryptic).
 274  *
 275  * Note that neither form is usable as an #if condition; if you truly
 276  * need to write conditional code that depends on a minimum or maximum
 277  * determined by the pre-processor instead of the compiler, you'll
 278  * have to open-code it.  Sadly, Coverity is severely confused by the
 279  * constant variants, so we have to dumb things down there.
 280  */
 281 #undef MIN
 282 #define MIN(a, b)                                       \
 283     ({                                                  \
 284         typeof(1 ? (a) : (b)) _a = (a), _b = (b);       \
 285         _a < _b ? _a : _b;                              \
 286     })
 287 #undef MAX
 288 #define MAX(a, b)                                       \
 289     ({                                                  \
 290         typeof(1 ? (a) : (b)) _a = (a), _b = (b);       \
 291         _a > _b ? _a : _b;                              \
 292     })
 293
 294 #ifdef __COVERITY__
 295 # define MIN_CONST(a, b) ((a) < (b) ? (a) : (b))
 296 # define MAX_CONST(a, b) ((a) > (b) ? (a) : (b))
 297 #else
 298 # define MIN_CONST(a, b)                                        \
 299     __builtin_choose_expr(                                      \
 300         __builtin_constant_p(a) && __builtin_constant_p(b),     \
 301         (a) < (b) ? (a) : (b),                                  \
 302         ((void)0))
 303 # define MAX_CONST(a, b)                                        \
 304     __builtin_choose_expr(                                      \
 305         __builtin_constant_p(a) && __builtin_constant_p(b),     \
 306         (a) > (b) ? (a) : (b),                                  \
 307         ((void)0))
 308 #endif
 309
 310 /*
 311  * Minimum function that returns zero only if both values are zero.
 312  * Intended for use with unsigned values only.
 313  */
 314 #ifndef MIN_NON_ZERO
 315 #define MIN_NON_ZERO(a, b)                              \
 316     ({                                                  \
 317         typeof(1 ? (a) : (b)) _a = (a), _b = (b);       \
 318         _a == 0 ? _b : (_b == 0 || _b > _a) ? _a : _b;  \
 319     })
 320 #endif
 321
 322 /*
 323  * Round number down to multiple. Safe when m is not a power of 2 (see
 324  * ROUND_DOWN for a faster version when a power of 2 is guaranteed).
 325  */
 326 #define QEMU_ALIGN_DOWN(n, m) ((n) / (m) * (m))
 327
 328 /*
 329  * Round number up to multiple. Safe when m is not a power of 2 (see
 330  * ROUND_UP for a faster version when a power of 2 is guaranteed).
 331  */
 332 #define QEMU_ALIGN_UP(n, m) QEMU_ALIGN_DOWN((n) + (m) - 1, (m))
 333
 334 /* Check if n is a multiple of m */
 335 #define QEMU_IS_ALIGNED(n, m) (((n) % (m)) == 0)
 336
 337 /* n-byte align pointer down */
 338 #define QEMU_ALIGN_PTR_DOWN(p, n) \
 339     ((typeof(p))QEMU_ALIGN_DOWN((uintptr_t)(p), (n)))
 340
 341 /* n-byte align pointer up */
 342 #define QEMU_ALIGN_PTR_UP(p, n) \
 343     ((typeof(p))QEMU_ALIGN_UP((uintptr_t)(p), (n)))
 344
 345 /* Check if pointer p is n-bytes aligned */
 346 #define QEMU_PTR_IS_ALIGNED(p, n) QEMU_IS_ALIGNED((uintptr_t)(p), (n))
 347
 348 /*
 349  * Round number down to multiple. Requires that d be a power of 2 (see
 350  * QEMU_ALIGN_UP for a safer but slower version on arbitrary
 351  * numbers); works even if d is a smaller type than n.
 352  */
 353 #ifndef ROUND_DOWN
 354 #define ROUND_DOWN(n, d) ((n) & -(0 ? (n) : (d)))
 355 #endif
 356
 357 /*
 358  * Round number up to multiple. Requires that d be a power of 2 (see
 359  * QEMU_ALIGN_UP for a safer but slower version on arbitrary
 360  * numbers); works even if d is a smaller type than n.
 361  */
 362 #ifndef ROUND_UP
 363 #define ROUND_UP(n, d) ROUND_DOWN((n) + (d) - 1, (d))
 364 #endif
 365
 366 #ifndef DIV_ROUND_UP
 367 #define DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
 368 #endif
 369
 370 /*
 371  * &(x)[0] is always a pointer - if it's same type as x then the argument is a
 372  * pointer, not an array.
 373  */
 374 #define QEMU_IS_ARRAY(x) (!__builtin_types_compatible_p(typeof(x), \
 375                                                         typeof(&(x)[0])))
 376 #ifndef ARRAY_SIZE
 377 #define ARRAY_SIZE(x) ((sizeof(x) / sizeof((x)[0])) + \
 378                        QEMU_BUILD_BUG_ON_ZERO(!QEMU_IS_ARRAY(x)))
 379 #endif
 380
 381 int qemu_daemon(int nochdir, int noclose);
 382 void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared,
 383                           bool noreserve);
 384 void qemu_anon_ram_free(void *ptr, size_t size);
 385
 386 #ifdef _WIN32
 387 #define HAVE_CHARDEV_SERIAL 1
 388 #elif defined(__linux__) || defined(__sun__) || defined(__FreeBSD__)    \
 389     || defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) \
 390     || defined(__GLIBC__) || defined(__APPLE__)
 391 #define HAVE_CHARDEV_SERIAL 1
 392 #endif
 393
 394 #if defined(__linux__) || defined(__FreeBSD__) ||               \
 395     defined(__FreeBSD_kernel__) || defined(__DragonFly__)
 396 #define HAVE_CHARDEV_PARPORT 1
 397 #endif
 398
 399 #if defined(__HAIKU__)
 400 #define SIGIO SIGPOLL
 401 #endif
 402
 403 #if defined(CONFIG_LINUX)
 404 #ifndef BUS_MCEERR_AR
 405 #define BUS_MCEERR_AR 4
 406 #endif
 407 #ifndef BUS_MCEERR_AO
 408 #define BUS_MCEERR_AO 5
 409 #endif
 410 #endif
 411
 412 #if defined(__linux__) && \
 413     (defined(__x86_64__) || defined(__arm__) || defined(__aarch64__) \
 414      || defined(__powerpc64__))
 415    /* Use 2 MiB alignment so transparent hugepages can be used by KVM.
 416       Valgrind does not support alignments larger than 1 MiB,
 417       therefore we need special code which handles running on Valgrind. */
 418 #  define QEMU_VMALLOC_ALIGN (512 * 4096)
 419 #elif defined(__linux__) && defined(__s390x__)
 420    /* Use 1 MiB (segment size) alignment so gmap can be used by KVM. */
 421 #  define QEMU_VMALLOC_ALIGN (256 * 4096)
 422 #elif defined(__linux__) && defined(__sparc__)
 423 #  define QEMU_VMALLOC_ALIGN MAX(qemu_real_host_page_size, SHMLBA)
 424 #else
 425 #  define QEMU_VMALLOC_ALIGN qemu_real_host_page_size
 426 #endif
 427
 428 #ifdef CONFIG_POSIX
 429 struct qemu_signalfd_siginfo {
 430     uint32_t ssi_signo;   /* Signal number */
 431     int32_t  ssi_errno;   /* Error number (unused) */
 432     int32_t  ssi_code;    /* Signal code */
 433     uint32_t ssi_pid;     /* PID of sender */
 434     uint32_t ssi_uid;     /* Real UID of sender */
 435     int32_t  ssi_fd;      /* File descriptor (SIGIO) */
 436     uint32_t ssi_tid;     /* Kernel timer ID (POSIX timers) */
 437     uint32_t ssi_band;    /* Band event (SIGIO) */
 438     uint32_t ssi_overrun; /* POSIX timer overrun count */
 439     uint32_t ssi_trapno;  /* Trap number that caused signal */
 440     int32_t  ssi_status;  /* Exit status or signal (SIGCHLD) */
 441     int32_t  ssi_int;     /* Integer sent by sigqueue(2) */
 442     uint64_t ssi_ptr;     /* Pointer sent by sigqueue(2) */
 443     uint64_t ssi_utime;   /* User CPU time consumed (SIGCHLD) */
 444     uint64_t ssi_stime;   /* System CPU time consumed (SIGCHLD) */
 445     uint64_t ssi_addr;    /* Address that generated signal
 446                              (for hardware-generated signals) */
 447     uint8_t  pad[48];     /* Pad size to 128 bytes (allow for
 448                              additional fields in the future) */
 449 };
 450
 451 int qemu_signalfd(const sigset_t *mask);
 452 void sigaction_invoke(struct sigaction *action,
 453                       struct qemu_signalfd_siginfo *info);
 454 #endif
 455
 456 /*
 457  * Don't introduce new usage of this function, prefer the following
 458  * qemu_open/qemu_create that take an "Error **errp"
 459  */
 460 int qemu_open_old(const char *name, int flags, ...);
 461 int qemu_open(const char *name, int flags, Error **errp);
 462 int qemu_create(const char *name, int flags, mode_t mode, Error **errp);
 463 int qemu_close(int fd);
 464 int qemu_unlink(const char *name);
 465 #ifndef _WIN32
 466 int qemu_dup_flags(int fd, int flags);
 467 int qemu_dup(int fd);
 468 int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive);
 469 int qemu_unlock_fd(int fd, int64_t start, int64_t len);
 470 int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive);
 471 bool qemu_has_ofd_lock(void);
 472 #endif
 473
 474 #if defined(__HAIKU__) && defined(__i386__)
 475 #define FMT_pid "%ld"
 476 #elif defined(WIN64)
 477 #define FMT_pid "%" PRId64
 478 #else
 479 #define FMT_pid "%d"
 480 #endif
 481
 482 bool qemu_write_pidfile(const char *pidfile, Error **errp);
 483
 484 int qemu_get_thread_id(void);
 485
 486 #ifndef CONFIG_IOVEC
 487 struct iovec {
 488     void *iov_base;
 489     size_t iov_len;
 490 };
 491 /*
 492  * Use the same value as Linux for now.
 493  */
 494 #define IOV_MAX 1024
 495
 496 ssize_t readv(int fd, const struct iovec *iov, int iov_cnt);
 497 ssize_t writev(int fd, const struct iovec *iov, int iov_cnt);
 498 #endif
 499
 500 #ifdef _WIN32
 501 static inline void qemu_timersub(const struct timeval *val1,
 502                                  const struct timeval *val2,
 503                                  struct timeval *res)
 504 {
 505     res->tv_sec = val1->tv_sec - val2->tv_sec;
 506     if (val1->tv_usec < val2->tv_usec) {
 507         res->tv_sec--;
 508         res->tv_usec = val1->tv_usec - val2->tv_usec + 1000 * 1000;
 509     } else {
 510         res->tv_usec = val1->tv_usec - val2->tv_usec;
 511     }
 512 }
 513 #else
 514 #define qemu_timersub timersub
 515 #endif
 516
 517 void qemu_set_cloexec(int fd);
 518
 519 void fips_set_state(bool requested);
 520 bool fips_get_state(void);
 521
 522 /* Return a dynamically allocated pathname denoting a file or directory that is
 523  * appropriate for storing local state.
 524  *
 525  * @relative_pathname need not start with a directory separator; one will be
 526  * added automatically.
 527  *
 528  * The caller is responsible for releasing the value returned with g_free()
 529  * after use.
 530  */
 531 char *qemu_get_local_state_pathname(const char *relative_pathname);
 532
 533 /* Find program directory, and save it for later usage with
 534  * qemu_get_exec_dir().
 535  * Try OS specific API first, if not working, parse from argv0. */
 536 void qemu_init_exec_dir(const char *argv0);
 537
 538 /* Get the saved exec dir.  */
 539 const char *qemu_get_exec_dir(void);
 540
 541 /**
 542  * qemu_getauxval:
 543  * @type: the auxiliary vector key to lookup
 544  *
 545  * Search the auxiliary vector for @type, returning the value
 546  * or 0 if @type is not present.
 547  */
 548 unsigned long qemu_getauxval(unsigned long type);
 549
 550 void qemu_set_tty_echo(int fd, bool echo);
 551
 552 void os_mem_prealloc(int fd, char *area, size_t sz, int smp_cpus,
 553                      Error **errp);
 554
 555 /**
 556  * qemu_get_pid_name:
 557  * @pid: pid of a process
 558  *
 559  * For given @pid fetch its name. Caller is responsible for
 560  * freeing the string when no longer needed.
 561  * Returns allocated string on success, NULL on failure.
 562  */
 563 char *qemu_get_pid_name(pid_t pid);
 564
 565 /**
 566  * qemu_fork:
 567  *
 568  * A version of fork that avoids signal handler race
 569  * conditions that can lead to child process getting
 570  * signals that are otherwise only expected by the
 571  * parent. It also resets all signal handlers to the
 572  * default settings.
 573  *
 574  * Returns 0 to child process, pid number to parent
 575  * or -1 on failure.
 576  */
 577 pid_t qemu_fork(Error **errp);
 578
 579 /* Using intptr_t ensures that qemu_*_page_mask is sign-extended even
 580  * when intptr_t is 32-bit and we are aligning a long long.
 581  */
 582 extern uintptr_t qemu_real_host_page_size;
 583 extern intptr_t qemu_real_host_page_mask;
 584
 585 /*
 586  * After using getopt or getopt_long, if you need to parse another set
 587  * of options, then you must reset optind.  Unfortunately the way to
 588  * do this varies between implementations of getopt.
 589  */
 590 static inline void qemu_reset_optind(void)
 591 {
 592 #ifdef HAVE_OPTRESET
 593     optind = 1;
 594     optreset = 1;
 595 #else
 596     optind = 0;
 597 #endif
 598 }
 599
 600 /**
 601  * qemu_get_host_name:
 602  * @errp: Error object
 603  *
 604  * Operating system agnostic way of querying host name.
 605  *
 606  * Returns allocated hostname (caller should free), NULL on failure.
 607  */
 608 char *qemu_get_host_name(Error **errp);
 609
 610 /**
 611  * qemu_get_host_physmem:
 612  *
 613  * Operating system agnostic way of querying host memory.
 614  *
 615  * Returns amount of physical memory on the system. This is purely
 616  * advisery and may return 0 if we can't work it out. At the other
 617  * end we saturate to SIZE_MAX if you are lucky enough to have that
 618  * much memory.
 619  */
 620 size_t qemu_get_host_physmem(void);
 621
 622 /*
 623  * Toggle write/execute on the pages marked MAP_JIT
 624  * for the current thread.
 625  */
 626 #if defined(MAC_OS_VERSION_11_0) && \
 627     MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_VERSION_11_0
 628 static inline void qemu_thread_jit_execute(void)
 629 {
 630     if (__builtin_available(macOS 11.0, *)) {
 631         pthread_jit_write_protect_np(true);
 632     }
 633 }
 634
 635 static inline void qemu_thread_jit_write(void)
 636 {
 637     if (__builtin_available(macOS 11.0, *)) {
 638         pthread_jit_write_protect_np(false);
 639     }
 640 }
 641 #else
 642 static inline void qemu_thread_jit_write(void) {}
 643 static inline void qemu_thread_jit_execute(void) {}
 644 #endif
 645
 646 /**
 647  * Platforms which do not support system() return ENOSYS
 648  */
 649 #ifndef HAVE_SYSTEM_FUNCTION
 650 #define system platform_does_not_support_system
 651 static inline int platform_does_not_support_system(const char *command)
 652 {
 653     errno = ENOSYS;
 654     return -1;
 655 }
 656 #endif /* !HAVE_SYSTEM_FUNCTION */
 657
 658 #ifdef __cplusplus
 659 }
 660 #endif
 661
 662 #endif