src/mapi/u_execmem.c

   1 /*
   2  * Mesa 3-D graphics library
   3  *
   4  * Copyright (C) 1999-2005  Brian Paul   All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the "Software"),
   8  * to deal in the Software without restriction, including without limitation
   9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  10  * and/or sell copies of the Software, and to permit persons to whom the
  11  * Software is furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included
  14  * in all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  17  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  22  * OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 /**
  27  * \file glapi_execmem.c
  28  *
  29  * Function for allocating executable memory for dispatch stubs.
  30  *
  31  * Copied from main/execmem.c and simplified for dispatch stubs.
  32  */
  33
  34
  35 #include "c99_compat.h"
  36 #include "c11/threads.h"
  37 #include "u_execmem.h"
  38
  39
  40 #define EXEC_MAP_SIZE (4*1024)
  41
  42 static mtx_t exec_mutex = _MTX_INITIALIZER_NP;
  43
  44 static unsigned int head = 0;
  45
  46 static unsigned char *exec_mem = (unsigned char *)0;
  47
  48
  49 #if defined(__linux__) || defined(__OpenBSD__) || defined(_NetBSD__) || defined(__sun) || defined(__HAIKU__)
  50
  51 #include <unistd.h>
  52 #include <sys/mman.h>
  53
  54 #ifdef MESA_SELINUX
  55 #include <selinux/selinux.h>
  56 #endif
  57
  58
  59 #ifndef MAP_ANONYMOUS
  60 #define MAP_ANONYMOUS MAP_ANON
  61 #endif
  62
  63
  64 /*
  65  * Dispatch stubs are of fixed size and never freed. Thus, we do not need to
  66  * overlay a heap, we just mmap a page and manage through an index.
  67  */
  68
  69 static int
  70 init_map(void)
  71 {
  72 #ifdef MESA_SELINUX
  73    if (is_selinux_enabled()) {
  74       if (!security_get_boolean_active("allow_execmem") ||
  75           !security_get_boolean_pending("allow_execmem"))
  76          return 0;
  77    }
  78 #endif
  79
  80    if (!exec_mem)
  81       exec_mem = mmap(NULL, EXEC_MAP_SIZE, PROT_EXEC | PROT_READ | PROT_WRITE,
  82                       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  83
  84    return (exec_mem != MAP_FAILED);
  85 }
  86
  87
  88 #elif defined(_WIN32)
  89
  90 #include <windows.h>
  91
  92
  93 /*
  94  * Avoid Data Execution Prevention.
  95  */
  96
  97 static int
  98 init_map(void)
  99 {
 100    exec_mem = VirtualAlloc(NULL, EXEC_MAP_SIZE, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
 101
 102    return (exec_mem != NULL);
 103 }
 104
 105
 106 #else
 107
 108 #include <stdlib.h>
 109
 110 static int
 111 init_map(void)
 112 {
 113    exec_mem = malloc(EXEC_MAP_SIZE);
 114
 115    return (exec_mem != NULL);
 116 }
 117
 118
 119 #endif
 120
 121 void *
 122 u_execmem_alloc(unsigned int size)
 123 {
 124    void *addr = NULL;
 125
 126    mtx_lock(&exec_mutex);
 127
 128    if (!init_map())
 129       goto bail;
 130
 131    /* free space check, assumes no integer overflow */
 132    if (head + size > EXEC_MAP_SIZE)
 133       goto bail;
 134
 135    /* allocation, assumes proper addr and size alignement */
 136    addr = exec_mem + head;
 137    head += size;
 138
 139 bail:
 140    mtx_unlock(&exec_mutex);
 141
 142    return addr;
 143 }
 144
 145