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src/os/win32/ngx_shmem.c - nginx source code

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Functions defined

Macros defined

Source code


  2. /*
  3. * Copyright (C) Igor Sysoev
  4. * Copyright (C) Nginx, Inc.
  5. */


  8. #include <ngx_config.h>
  9. #include <ngx_core.h>


  12. /*
  13. * Base addresses selected by system for shared memory mappings are likely
  14. * to be different on Windows Vista and later versions due to address space
  15. * layout randomization.  This is however incompatible with storing absolute
  16. * addresses within the shared memory.
  17. *
  18. * To make it possible to store absolute addresses we create mappings
  19. * at the same address in all processes by starting mappings at predefined
  20. * addresses.  The addresses were selected somewhat randomly in order to
  21. * minimize the probability that some other library doing something similar
  22. * conflicts with us.  The addresses are from the following typically free
  23. * blocks:
  24. *
  25. * - 0x10000000 .. 0x70000000 (about 1.5 GB in total) on 32-bit platforms
  26. * - 0x000000007fff0000 .. 0x000007f68e8b0000 (about 8 TB) on 64-bit platforms
  27. *
  28. * Additionally, we allow to change the mapping address once it was detected
  29. * to be different from one originally used.  This is needed to support
  30. * reconfiguration.
  31. */


  34. #ifdef _WIN64
  35. ‌#define NGX_SHMEM_BASE  0x0000047047e00000
  36. #else
  37. ‌#define NGX_SHMEM_BASE  0x2efe0000
  38. #endif


  41. ‌ngx_uint_t  ngx_allocation_granularity;


  44. ngx_int_t
  45. ‌ngx_shm_alloc(ngx_shm_t *shm)
  46. {
  47.     u_char         *name;
  48.     uint64_t        size;
  49.     static u_char  *base = (u_char *) NGX_SHMEM_BASE;

  51.     name = ngx_alloc(shm->name.len + 2 + NGX_INT32_LEN, shm->log);
  52.     if (name == NULL) {
  53.         return NGX_ERROR;
  54.     }

  56.     (void) ngx_sprintf(name, "%V_%s%Z", &shm->name, ngx_unique);

  58.     ngx_set_errno(0);

  60.     size = shm->size;

  62.     shm->handle = CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE,
  63.                                     (u_long) (size >> 32),
  64.                                     (u_long) (size & 0xffffffff),
  65.                                     (char *) name);

  67.     if (shm->handle == NULL) {
  68.         ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
  69.                       "CreateFileMapping(%uz, %s) failed",
  70.                       shm->size, name);
  71.         ngx_free(name);

  73.         return NGX_ERROR;
  74.     }

  76.     ngx_free(name);

  78.     if (ngx_errno == ERROR_ALREADY_EXISTS) {
  79.         shm->exists = 1;
  80.     }

  82.     shm->addr = MapViewOfFileEx(shm->handle, FILE_MAP_WRITE, 0, 0, 0, base);

  84.     if (shm->addr != NULL) {
  85.         base += ngx_align(size, ngx_allocation_granularity);
  86.         return NGX_OK;
  87.     }

  89.     ngx_log_debug3(NGX_LOG_DEBUG_CORE, shm->log, ngx_errno,
  90.                    "MapViewOfFileEx(%uz, %p) of file mapping \"%V\" failed, "
  91.                    "retry without a base address",
  92.                    shm->size, base, &shm->name);

  94.     /*
  95.      * Order of shared memory zones may be different in the master process
  96.      * and worker processes after reconfiguration.  As a result, the above
  97.      * may fail due to a conflict with a previously created mapping remapped
  98.      * to a different address.  Additionally, there may be a conflict with
  99.      * some other uses of the memory.  In this case we retry without a base
  100.      * address to let the system assign the address itself.
  101.      */

  103.     shm->addr = MapViewOfFile(shm->handle, FILE_MAP_WRITE, 0, 0, 0);

  105.     if (shm->addr != NULL) {
  106.         return NGX_OK;
  107.     }

  109.     ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
  110.                   "MapViewOfFile(%uz) of file mapping \"%V\" failed",
  111.                   shm->size, &shm->name);

  113.     if (CloseHandle(shm->handle) == 0) {
  114.         ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
  115.                       "CloseHandle() of file mapping \"%V\" failed",
  116.                       &shm->name);
  117.     }

  119.     return NGX_ERROR;
  120. }


  123. ngx_int_t
  124. ‌ngx_shm_remap(ngx_shm_t *shm, u_char *addr)
  125. {
  126.     if (UnmapViewOfFile(shm->addr) == 0) {
  127.         ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
  128.                       "UnmapViewOfFile(%p) of file mapping \"%V\" failed",
  129.                       shm->addr, &shm->name);
  130.         return NGX_ERROR;
  131.     }

  133.     shm->addr = MapViewOfFileEx(shm->handle, FILE_MAP_WRITE, 0, 0, 0, addr);

  135.     if (shm->addr != NULL) {
  136.         return NGX_OK;
  137.     }

  139.     ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
  140.                   "MapViewOfFileEx(%uz, %p) of file mapping \"%V\" failed",
  141.                   shm->size, addr, &shm->name);

  143.     return NGX_ERROR;
  144. }


  147. void
  148. ‌ngx_shm_free(ngx_shm_t *shm)
  149. {
  150.     if (UnmapViewOfFile(shm->addr) == 0) {
  151.         ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
  152.                       "UnmapViewOfFile(%p) of file mapping \"%V\" failed",
  153.                       shm->addr, &shm->name);
  154.     }

  156.     if (CloseHandle(shm->handle) == 0) {
  157.         ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
  158.                       "CloseHandle() of file mapping \"%V\" failed",
  159.                       &shm->name);
  160.     }
  161. }

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