libgo/runtime/mem.c

   1 #include <errno.h>
   2 #include <unistd.h>
   3
   4 #include "runtime.h"
   5 #include "arch.h"
   6 #include "malloc.h"
   7
   8 #ifndef MAP_ANON
   9 #ifdef MAP_ANONYMOUS
  10 #define MAP_ANON MAP_ANONYMOUS
  11 #else
  12 #define USE_DEV_ZERO
  13 #define MAP_ANON 0
  14 #endif
  15 #endif
  16
  17 #ifdef USE_DEV_ZERO
  18 static int dev_zero = -1;
  19 #endif
  20
  21 static _Bool
  22 addrspace_free(void *v __attribute__ ((unused)), uintptr n __attribute__ ((unused)))
  23 {
  24 #ifdef HAVE_MINCORE
  25         size_t page_size = getpagesize();
  26         size_t off;
  27         char one_byte;
  28
  29         errno = 0;
  30         for(off = 0; off < n; off += page_size)
  31                 if(mincore((char *)v + off, page_size, (void *)&one_byte) != -1
  32                    || errno != ENOMEM)
  33                         return 0;
  34 #endif
  35         return 1;
  36 }
  37
  38 void*
  39 runtime_SysAlloc(uintptr n)
  40 {
  41         void *p;
  42         int fd = -1;
  43
  44         mstats.sys += n;
  45
  46 #ifdef USE_DEV_ZERO
  47         if (dev_zero == -1) {
  48                 dev_zero = open("/dev/zero", O_RDONLY);
  49                 if (dev_zero < 0) {
  50                         printf("open /dev/zero: errno=%d\n", errno);
  51                         exit(2);
  52                 }
  53         }
  54         fd = dev_zero;
  55 #endif
  56
  57         p = runtime_mmap(nil, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, fd, 0);
  58         if (p == MAP_FAILED) {
  59                 if(errno == EACCES) {
  60                         printf("runtime: mmap: access denied\n");
  61                         printf("if you're running SELinux, enable execmem for this process.\n");
  62                         exit(2);
  63                 }
  64                 return nil;
  65         }
  66         return p;
  67 }
  68
  69 void
  70 runtime_SysUnused(void *v, uintptr n)
  71 {
  72         USED(v);
  73         USED(n);
  74         // TODO(rsc): call madvise MADV_DONTNEED
  75 }
  76
  77 void
  78 runtime_SysFree(void *v, uintptr n)
  79 {
  80         mstats.sys -= n;
  81         runtime_munmap(v, n);
  82 }
  83
  84 void*
  85 runtime_SysReserve(void *v, uintptr n)
  86 {
  87         int fd = -1;
  88         void *p;
  89
  90         // On 64-bit, people with ulimit -v set complain if we reserve too
  91         // much address space.  Instead, assume that the reservation is okay
  92         // and check the assumption in SysMap.
  93         if(sizeof(void*) == 8)
  94                 return v;
  95
  96 #ifdef USE_DEV_ZERO
  97         if (dev_zero == -1) {
  98                 dev_zero = open("/dev/zero", O_RDONLY);
  99                 if (dev_zero < 0) {
 100                         printf("open /dev/zero: errno=%d\n", errno);
 101                         exit(2);
 102                 }
 103         }
 104         fd = dev_zero;
 105 #endif
 106
 107         p = runtime_mmap(v, n, PROT_NONE, MAP_ANON|MAP_PRIVATE, fd, 0);
 108         if((uintptr)p < 4096 || -(uintptr)p < 4096) {
 109                 return nil;
 110         }
 111         return p;
 112 }
 113
 114 void
 115 runtime_SysMap(void *v, uintptr n)
 116 {
 117         void *p;
 118         int fd = -1;
 119
 120         mstats.sys += n;
 121
 122 #ifdef USE_DEV_ZERO
 123         if (dev_zero == -1) {
 124                 dev_zero = open("/dev/zero", O_RDONLY);
 125                 if (dev_zero < 0) {
 126                         printf("open /dev/zero: errno=%d\n", errno);
 127                         exit(2);
 128                 }
 129         }
 130         fd = dev_zero;
 131 #endif
 132
 133         // On 64-bit, we don't actually have v reserved, so tread carefully.
 134         if(sizeof(void*) == 8) {
 135                 p = runtime_mmap(v, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, fd, 0);
 136                 if(p != v && addrspace_free(v, n)) {
 137                         // On some systems, mmap ignores v without
 138                         // MAP_FIXED, so retry if the address space is free.
 139                         p = runtime_mmap(v, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_FIXED|MAP_PRIVATE, fd, 0);
 140                 }
 141                 if(p != v) {
 142                         runtime_printf("runtime: address space conflict: map(%p) = %p\n", v, p);
 143                         runtime_throw("runtime: address space conflict");
 144                 }
 145                 return;
 146         }
 147
 148         p = runtime_mmap(v, n, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_FIXED|MAP_PRIVATE, fd, 0);
 149         if(p != v)
 150                 runtime_throw("runtime: cannot map pages in arena address space");
 151 }