src/mapi/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  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR 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 "u_compiler.h"
  36 #include "u_thread.h"
  37 #include "u_execmem.h"
  38
  39
  40 #if defined(__linux__) || defined(__OpenBSD__) || defined(_NetBSD__) || defined(__sun)
  41
  42 #include <unistd.h>
  43 #include <sys/mman.h>
  44
  45 #ifdef MESA_SELINUX
  46 #include <selinux/selinux.h>
  47 #endif
  48
  49
  50 #ifndef MAP_ANONYMOUS
  51 #define MAP_ANONYMOUS MAP_ANON
  52 #endif
  53
  54
  55 #define EXEC_MAP_SIZE (4*1024)
  56
  57 u_mutex_declare_static(exec_mutex);
  58
  59 static unsigned int head = 0;
  60
  61 static unsigned char *exec_mem = NULL;
  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 void *
  89 u_execmem_alloc(unsigned int size)
  90 {
  91    void *addr = NULL;
  92
  93    u_mutex_lock(exec_mutex);
  94
  95    if (!init_map())
  96       goto bail;
  97
  98    /* free space check, assumes no integer overflow */
  99    if (head + size > EXEC_MAP_SIZE)
 100       goto bail;
 101
 102    /* allocation, assumes proper addr and size alignement */
 103    addr = exec_mem + head;
 104    head += size;
 105
 106 bail:
 107    u_mutex_unlock(exec_mutex);
 108
 109    return addr;
 110 }
 111
 112
 113 #elif defined(_WIN32)
 114
 115 #include <windows.h>
 116
 117
 118 /*
 119  * Avoid Data Execution Prevention.
 120  */
 121
 122 void *
 123 u_execmem_alloc(unsigned int size)
 124 {
 125    return VirtualAlloc(NULL, size, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
 126 }
 127
 128
 129 #else
 130
 131 void *
 132 u_execmem_alloc(unsigned int size)
 133 {
 134    return malloc(size);
 135 }
 136
 137
 138 #endif