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Member "src/Boot/Windows/BootMemory.cpp" (10 Oct 2018, 1918 Bytes) of package /windows/misc/VeraCrypt_1.23-Hotfix-2_Source.zip:


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    1 /*
    2  Derived from source code of TrueCrypt 7.1a, which is
    3  Copyright (c) 2008-2012 TrueCrypt Developers Association and which is governed
    4  by the TrueCrypt License 3.0.
    5 
    6  Modifications and additions to the original source code (contained in this file)
    7  and all other portions of this file are Copyright (c) 2013-2017 IDRIX
    8  and are governed by the Apache License 2.0 the full text of which is
    9  contained in the file License.txt included in VeraCrypt binary and source
   10  code distribution packages.
   11 */
   12 
   13 #include "BootDefs.h"
   14 #include "BootMemory.h"
   15 
   16 static uint32 MemoryMapContValue;
   17 
   18 static bool GetMemoryMapEntry (BiosMemoryMapEntry &entry)
   19 {
   20     static const uint32 function = 0x0000E820UL;
   21     static const uint32 magic = 0x534D4150UL;
   22     static const uint32 bufferSize = sizeof (BiosMemoryMapEntry);
   23 
   24     bool carry = false;
   25     uint32 resultMagic;
   26     uint32 resultSize;
   27 
   28     __asm
   29     {
   30         push es
   31 
   32         lea di, function
   33         TC_ASM_MOV_EAX_DI
   34         lea di, MemoryMapContValue
   35         TC_ASM_MOV_EBX_DI
   36         lea di, bufferSize
   37         TC_ASM_MOV_ECX_DI
   38         lea di, magic
   39         TC_ASM_MOV_EDX_DI
   40         lea di, MemoryMapContValue
   41         TC_ASM_MOV_DI_ECX
   42 
   43         // Use alternative segment to prevent memory corruption caused by buggy BIOSes
   44         push TC_BOOT_LOADER_ALT_SEGMENT
   45         pop es
   46         mov di, 0
   47 
   48         int 0x15
   49         jnc no_carry
   50         mov carry, true
   51     no_carry:
   52 
   53         lea di, resultMagic
   54         TC_ASM_MOV_DI_EAX
   55         lea di, MemoryMapContValue
   56         TC_ASM_MOV_DI_EBX
   57         lea di, resultSize
   58         TC_ASM_MOV_DI_ECX
   59 
   60         pop es
   61     }
   62 
   63     CopyMemory (TC_BOOT_LOADER_ALT_SEGMENT, 0, &entry, sizeof (entry));
   64 
   65     // BIOS may set CF at the end of the list
   66     if (carry)
   67         MemoryMapContValue = 0;
   68 
   69     return resultMagic == magic && resultSize == bufferSize;
   70 }
   71 
   72 
   73 bool GetFirstBiosMemoryMapEntry (BiosMemoryMapEntry &entry)
   74 {
   75     MemoryMapContValue = 0;
   76     return GetMemoryMapEntry (entry);
   77 }
   78 
   79 
   80 bool GetNextBiosMemoryMapEntry (BiosMemoryMapEntry &entry)
   81 {
   82     if (MemoryMapContValue == 0)
   83         return false;
   84 
   85     return GetMemoryMapEntry (entry);
   86 }