src/mapi/u_execmem.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5
   4  *
   5  * Copyright (C) 1999-2005  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  21  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  22  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  23  * OTHER DEALINGS IN THE SOFTWARE.
  24  */
  25
  26
  27 /**
  28  * \file glapi_execmem.c
  29  *
  30  * Function for allocating executable memory for dispatch stubs.
  31  *
  32  * Copied from main/execmem.c and simplified for dispatch stubs.
  33  */
  34
  35
  36 #include "u_compiler.h"
  37 #include "u_thread.h"
  38 #include "u_execmem.h"
  39
  40
  41 #define EXEC_MAP_SIZE (4*1024)
  42
  43 u_mutex_declare_static(exec_mutex);
  44
  45 static unsigned int head = 0;
  46
  47 static unsigned char *exec_mem = (unsigned char *)0;
  48
  49
  50 #if defined(__linux__) || defined(__OpenBSD__) || defined(_NetBSD__) || defined(__sun)
  51
  52 #include <unistd.h>
  53 #include <sys/mman.h>
  54
  55 #ifdef MESA_SELINUX
  56 #include <selinux/selinux.h>
  57 #endif
  58
  59
  60 #ifndef MAP_ANONYMOUS
  61 #define MAP_ANONYMOUS MAP_ANON
  62 #endif
  63
  64
  65 /*
  66  * Dispatch stubs are of fixed size and never freed. Thus, we do not need to
  67  * overlay a heap, we just mmap a page and manage through an index.
  68  */
  69
  70 static int
  71 init_map(void)
  72 {
  73 #ifdef MESA_SELINUX
  74    if (is_selinux_enabled()) {
  75       if (!security_get_boolean_active("allow_execmem") ||
  76           !security_get_boolean_pending("allow_execmem"))
  77          return 0;
  78    }
  79 #endif
  80
  81    if (!exec_mem)
  82       exec_mem = mmap(NULL, EXEC_MAP_SIZE, PROT_EXEC | PROT_READ | PROT_WRITE,
  83                       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  84
  85    return (exec_mem != MAP_FAILED);
  86 }
  87
  88
  89 #elif defined(_WIN32)
  90
  91 #include <windows.h>
  92
  93
  94 /*
  95  * Avoid Data Execution Prevention.
  96  */
  97
  98 static int
  99 init_map(void)
 100 {
 101    exec_mem = VirtualAlloc(NULL, EXEC_MAP_SIZE, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
 102
 103    return (exec_mem != NULL);
 104 }
 105
 106
 107 #else
 108
 109 #include <stdlib.h>
 110
 111 static int
 112 init_map(void)
 113 {
 114    exec_mem = malloc(EXEC_MAP_SIZE);
 115
 116    return (exec_mem != NULL);
 117 }
 118
 119
 120 #endif
 121
 122 void *
 123 u_execmem_alloc(unsigned int size)
 124 {
 125    void *addr = NULL;
 126
 127    u_mutex_lock(exec_mutex);
 128
 129    if (!init_map())
 130       goto bail;
 131
 132    /* free space check, assumes no integer overflow */
 133    if (head + size > EXEC_MAP_SIZE)
 134       goto bail;
 135
 136    /* allocation, assumes proper addr and size alignement */
 137    addr = exec_mem + head;
 138    head += size;
 139
 140 bail:
 141    u_mutex_unlock(exec_mutex);
 142
 143    return addr;
 144 }
 145
 146