src/st-system.c

   1
   2
   3 #include "st-system.h"
   4 #include "st-utils.h"
   5
   6 #include <unistd.h>
   7 #include <sys/mman.h>
   8 #include <errno.h>
   9 #include <stdio.h>
  10 #include <string.h>
  11
  12 static st_pointer
  13 st_mmap_anon (st_pointer address, st_uint length,
  14               int protect, int flags)
  15 {
  16     /* Wrapper for mmap(), with the default flags as MAP_PRIVATE | MAP_ANONYMOUS.
  17      * Returns NULL on failure.
  18      */
  19     st_pointer result;
  20
  21     result = mmap (address, length, protect,
  22                    flags | MAP_PRIVATE | MAP_ANONYMOUS,
  23                    0, 0);
  24
  25     if (result == (st_pointer) -1) {
  26         fprintf (stderr, "panda: error: %s\n", strerror (errno));
  27         return NULL;
  28     }
  29
  30     return result;
  31 }
  32
  33 st_pointer
  34 st_system_reserve_memory (st_pointer addr, st_uint size)
  35 {
  36     /* Reserves a virtual memory region without actually allocating any
  37      * storage in physical memory or swap space.
  38      */
  39     int flags = 0;
  40
  41     flags = MAP_NORESERVE;
  42     if (addr)
  43         flags |= MAP_FIXED;
  44
  45     return st_mmap_anon (addr, size, PROT_NONE, flags);
  46 }
  47
  48 st_pointer
  49 st_system_commit_memory  (st_pointer addr, st_uint size)
  50 {
  51     /* Allocates storage in physical memory or swap space.
  52      */
  53     int flags = 0;
  54
  55     if (munmap (addr, size) < 0) {
  56         fprintf (stderr, "panda: error: %s\n", strerror (errno));
  57         return false;
  58     }
  59
  60     if (addr)
  61         flags |= MAP_FIXED;
  62
  63     return st_mmap_anon (addr, size, PROT_READ | PROT_WRITE, flags);
  64 }
  65
  66 st_pointer
  67 st_system_decommit_memory  (st_pointer addr, st_uint size)
  68 {
  69     /* Deallocates any storage but ensures that the given region is still reserved
  70      */
  71     int flags = 0;
  72
  73     st_assert (addr != NULL);
  74     if (munmap (addr, size) < 0) {
  75         fprintf (stderr, "panda: error: %s\n", strerror (errno));
  76         return false;
  77     }
  78
  79     flags = MAP_NORESERVE;
  80     if (addr)
  81         flags |= MAP_FIXED;
  82
  83     return st_mmap_anon (addr, size, PROT_NONE, flags);
  84 }
  85
  86 void
  87 st_system_release_memory (st_pointer addr, st_uint size)
  88 {
  89     /* destroys any virtual memory mappings within the given region
  90      */
  91     st_assert (addr != NULL);
  92     if (munmap (addr, size) < 0) {
  93         fprintf (stderr, "panda: error: %s\n", strerror (errno));
  94         st_assert_not_reached ();
  95     }
  96 }
  97
  98 st_uint
  99 st_system_pagesize (void)
 100 {
 101     return getpagesize ();
 102 }