libgo/runtime/mem.c

   1 /* Defining _XOPEN_SOURCE hides the declaration of madvise() on Solaris <
   2    11 and the MADV_DONTNEED definition on IRIX 6.5.  */
   3 #undef _XOPEN_SOURCE
   4
   5 #include <errno.h>
   6 #include <unistd.h>
   7
   8 #include "runtime.h"
   9 #include "arch.h"
  10 #include "malloc.h"
  11
  12 #ifndef MAP_ANON
  13 #ifdef MAP_ANONYMOUS
  14 #define MAP_ANON MAP_ANONYMOUS
  15 #else
  16 #define USE_DEV_ZERO
  17 #define MAP_ANON 0
  18 #endif
  19 #endif
  20
  21 #ifndef MAP_NORESERVE
  22 #define MAP_NORESERVE 0
  23 #endif
  24
  25 #ifdef USE_DEV_ZERO
  26 static int dev_zero = -1;
  27 #endif
  28
  29 static int32
  30 addrspace_free(void *v __attribute__ ((unused)), uintptr n __attribute__ ((unused)))
  31 {
  32 #ifdef HAVE_MINCORE
  33         size_t page_size = getpagesize();
  34         int32 errval;
  35         uintptr chunk;
  36         uintptr off;
  37
  38         // NOTE: vec must be just 1 byte long here.
  39         // Mincore returns ENOMEM if any of the pages are unmapped,
  40         // but we want to know that all of the pages are unmapped.
  41         // To make these the same, we can only ask about one page
  42         // at a time. See golang.org/issue/7476.
  43         static byte vec[1];
  44
  45         errno = 0;
  46         for(off = 0; off < n; off += chunk) {
  47                 chunk = page_size * sizeof vec;
  48                 if(chunk > (n - off))
  49                         chunk = n - off;
  50                 errval = mincore((int8*)v + off, chunk, vec);
  51                 // ENOMEM means unmapped, which is what we want.
  52                 // Anything else we assume means the pages are mapped.
  53                 if(errval == 0 || errno != ENOMEM)
  54                         return 0;
  55         }
  56 #endif
  57         return 1;
  58 }
  59
  60 static void *
  61 mmap_fixed(byte *v, uintptr n, int32 prot, int32 flags, int32 fd, uint32 offset)
  62 {
  63         void *p;
  64
  65         p = runtime_mmap((void *)v, n, prot, flags, fd, offset);
  66         if(p != v && addrspace_free(v, n)) {
  67                 // On some systems, mmap ignores v without
  68                 // MAP_FIXED, so retry if the address space is free.
  69                 if(p != MAP_FAILED)
  70                         runtime_munmap(p, n);
  71                 p = runtime_mmap((void *)v, n, prot, flags|MAP_FIXED, fd, offset);
  72         }
  73         return p;
  74 }
  75
  76 void*
  77 runtime_SysAlloc(uintptr n, uint64 *stat)
  78 {
  79         void *p;
  80         int fd = -1;
  81
  82 #ifdef USE_DEV_ZERO
  83         if (dev_zero == -1) {
  84                 dev_zero = open("/dev/zero", O_RDONLY);
  85                 if (dev_zero < 0) {
  86                         runtime_printf("open /dev/zero: errno=%d\n", errno);
  87                         exit(2);
  88                 }
  89         }
  90         fd = dev_zero;
  91 #endif
  92
  93         p = runtime_mmap(nil, n, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, fd, 0);
  94         if (p == MAP_FAILED) {
  95                 if(errno == EACCES) {
  96                         runtime_printf("runtime: mmap: access denied\n");
  97                         runtime_printf("if you're running SELinux, enable execmem for this process.\n");
  98                         exit(2);
  99                 }
 100                 if(errno == EAGAIN) {
 101                         runtime_printf("runtime: mmap: too much locked memory (check 'ulimit -l').\n");
 102                         runtime_exit(2);
 103                 }
 104                 return nil;
 105         }
 106         runtime_xadd64(stat, n);
 107         return p;
 108 }
 109
 110 void
 111 runtime_SysUnused(void *v __attribute__ ((unused)), uintptr n __attribute__ ((unused)))
 112 {
 113 #ifdef MADV_DONTNEED
 114         runtime_madvise(v, n, MADV_DONTNEED);
 115 #endif
 116 }
 117
 118 void
 119 runtime_SysUsed(void *v, uintptr n)
 120 {
 121         USED(v);
 122         USED(n);
 123 }
 124
 125 void
 126 runtime_SysFree(void *v, uintptr n, uint64 *stat)
 127 {
 128         runtime_xadd64(stat, -(uint64)n);
 129         runtime_munmap(v, n);
 130 }
 131
 132 void
 133 runtime_SysFault(void *v, uintptr n)
 134 {
 135         int fd = -1;
 136
 137 #ifdef USE_DEV_ZERO
 138         if (dev_zero == -1) {
 139                 dev_zero = open("/dev/zero", O_RDONLY);
 140                 if (dev_zero < 0) {
 141                         runtime_printf("open /dev/zero: errno=%d\n", errno);
 142                         exit(2);
 143                 }
 144         }
 145         fd = dev_zero;
 146 #endif
 147
 148         runtime_mmap(v, n, PROT_NONE, MAP_ANON|MAP_PRIVATE|MAP_FIXED, fd, 0);
 149 }
 150
 151 void*
 152 runtime_SysReserve(void *v, uintptr n, bool *reserved)
 153 {
 154         int fd = -1;
 155         void *p;
 156
 157 #ifdef USE_DEV_ZERO
 158         if (dev_zero == -1) {
 159                 dev_zero = open("/dev/zero", O_RDONLY);
 160                 if (dev_zero < 0) {
 161                         runtime_printf("open /dev/zero: errno=%d\n", errno);
 162                         exit(2);
 163                 }
 164         }
 165         fd = dev_zero;
 166 #endif
 167
 168         // On 64-bit, people with ulimit -v set complain if we reserve too
 169         // much address space.  Instead, assume that the reservation is okay
 170         // if we can reserve at least 64K and check the assumption in SysMap.
 171         // Only user-mode Linux (UML) rejects these requests.
 172         if(sizeof(void*) == 8 && (n >> 16) > 1LLU<<16) {
 173                 p = mmap_fixed(v, 64<<10, PROT_NONE, MAP_ANON|MAP_PRIVATE, fd, 0);
 174                 if (p != v) {
 175                         runtime_munmap(p, 64<<10);
 176                         return nil;
 177                 }
 178                 runtime_munmap(p, 64<<10);
 179                 *reserved = false;
 180                 return v;
 181         }
 182
 183         // Use the MAP_NORESERVE mmap() flag here because typically most of
 184         // this reservation will never be used. It does not make sense
 185         // reserve a huge amount of unneeded swap space. This is important on
 186         // systems which do not overcommit memory by default.
 187         p = runtime_mmap(v, n, PROT_NONE, MAP_ANON|MAP_PRIVATE|MAP_NORESERVE, fd, 0);
 188         if(p == MAP_FAILED)
 189                 return nil;
 190         *reserved = true;
 191         return p;
 192 }
 193
 194 void
 195 runtime_SysMap(void *v, uintptr n, bool reserved, uint64 *stat)
 196 {
 197         void *p;
 198         int fd = -1;
 199
 200         runtime_xadd64(stat, n);
 201
 202 #ifdef USE_DEV_ZERO
 203         if (dev_zero == -1) {
 204                 dev_zero = open("/dev/zero", O_RDONLY);
 205                 if (dev_zero < 0) {
 206                         runtime_printf("open /dev/zero: errno=%d\n", errno);
 207                         exit(2);
 208                 }
 209         }
 210         fd = dev_zero;
 211 #endif
 212
 213         // On 64-bit, we don't actually have v reserved, so tread carefully.
 214         if(!reserved) {
 215                 p = mmap_fixed(v, n, PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, fd, 0);
 216                 if(p == MAP_FAILED && errno == ENOMEM)
 217                         runtime_throw("runtime: out of memory");
 218                 if(p != v) {
 219                         runtime_printf("runtime: address space conflict: map(%p) = %p\n", v, p);
 220                         runtime_throw("runtime: address space conflict");
 221                 }
 222                 return;
 223         }
 224
 225         p = runtime_mmap(v, n, PROT_READ|PROT_WRITE, MAP_ANON|MAP_FIXED|MAP_PRIVATE, fd, 0);
 226         if(p == MAP_FAILED && errno == ENOMEM)
 227                 runtime_throw("runtime: out of memory");
 228         if(p != v)
 229                 runtime_throw("runtime: cannot map pages in arena address space");
 230 }