/*
* Copyright (C) Igor Sysoev
* Copyright (C) Nginx, Inc.
*/
#include <ngx_config.h>
#include <ngx_core.h>
/*
* Base addresses selected by system for shared memory mappings are likely
* to be different on Windows Vista and later versions due to address space
* layout randomization. This is however incompatible with storing absolute
* addresses within the shared memory.
*
* To make it possible to store absolute addresses we create mappings
* at the same address in all processes by starting mappings at predefined
* addresses. The addresses were selected somewhat randomly in order to
* minimize the probability that some other library doing something similar
* conflicts with us. The addresses are from the following typically free
* blocks:
*
* - 0x10000000 .. 0x70000000 (about 1.5 GB in total) on 32-bit platforms
* - 0x000000007fff0000 .. 0x000007f68e8b0000 (about 8 TB) on 64-bit platforms
*
* Additionally, we allow to change the mapping address once it was detected
* to be different from one originally used. This is needed to support
* reconfiguration.
*/
#ifdef _WIN64
#define NGX_SHMEM_BASE 0x0000047047e00000
#else
#define NGX_SHMEM_BASE 0x2efe0000
#endif
ngx_uint_t ngx_allocation_granularity;
ngx_int_t
ngx_shm_alloc(ngx_shm_t *shm)
{
u_char *name;
uint64_t size;
static u_char *base = (u_char *) NGX_SHMEM_BASE;
name = ngx_alloc(shm->name.len + 2 + NGX_INT32_LEN, shm->log);
if (name == NULL) {
return NGX_ERROR;
}
(void) ngx_sprintf(name, "%V_%s%Z", &shm->name, ngx_unique);
ngx_set_errno(0);
size = shm->size;
shm->handle = CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE,
(u_long) (size >> 32),
(u_long) (size & 0xffffffff),
(char *) name);
if (shm->handle == NULL) {
ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
"CreateFileMapping(%uz, %s) failed",
shm->size, name);
ngx_free(name);
return NGX_ERROR;
}
ngx_free(name);
if (ngx_errno == ERROR_ALREADY_EXISTS) {
shm->exists = 1;
}
shm->addr = MapViewOfFileEx(shm->handle, FILE_MAP_WRITE, 0, 0, 0, base);
if (shm->addr != NULL) {
base += ngx_align(size, ngx_allocation_granularity);
return NGX_OK;
}
ngx_log_debug3(NGX_LOG_DEBUG_CORE, shm->log, ngx_errno,
"MapViewOfFileEx(%uz, %p) of file mapping \"%V\" failed, "
"retry without a base address",
shm->size, base, &shm->name);
/*
* Order of shared memory zones may be different in the master process
* and worker processes after reconfiguration. As a result, the above
* may fail due to a conflict with a previously created mapping remapped
* to a different address. Additionally, there may be a conflict with
* some other uses of the memory. In this case we retry without a base
* address to let the system assign the address itself.
*/
shm->addr = MapViewOfFile(shm->handle, FILE_MAP_WRITE, 0, 0, 0);
if (shm->addr != NULL) {
return NGX_OK;
}
ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
"MapViewOfFile(%uz) of file mapping \"%V\" failed",
shm->size, &shm->name);
if (CloseHandle(shm->handle) == 0) {
ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
"CloseHandle() of file mapping \"%V\" failed",
&shm->name);
}
return NGX_ERROR;
}
ngx_int_t
ngx_shm_remap(ngx_shm_t *shm, u_char *addr)
{
if (UnmapViewOfFile(shm->addr) == 0) {
ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
"UnmapViewOfFile(%p) of file mapping \"%V\" failed",
shm->addr, &shm->name);
return NGX_ERROR;
}
shm->addr = MapViewOfFileEx(shm->handle, FILE_MAP_WRITE, 0, 0, 0, addr);
if (shm->addr != NULL) {
return NGX_OK;
}
ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
"MapViewOfFileEx(%uz, %p) of file mapping \"%V\" failed",
shm->size, addr, &shm->name);
return NGX_ERROR;
}
void
ngx_shm_free(ngx_shm_t *shm)
{
if (UnmapViewOfFile(shm->addr) == 0) {
ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
"UnmapViewOfFile(%p) of file mapping \"%V\" failed",
shm->addr, &shm->name);
}
if (CloseHandle(shm->handle) == 0) {
ngx_log_error(NGX_LOG_ALERT, shm->log, ngx_errno,
"CloseHandle() of file mapping \"%V\" failed",
&shm->name);
}
}
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