/// <summary>
/// based on <a href="https://github.com/dotnet/coreclr/blob/master/src/gcdump/i386/gcdumpx86.cpp">GCDump::DumpGCTable</a>
/// </summary>
private void SaveCallTransition(byte[] image, ref int offset, uint val, uint curOffs, uint callRegMask, bool callPndTab, uint callPndTabCnt, uint callPndMask, uint lastSkip, ref uint imask)
{
uint iregMask, iargMask;
iregMask = imask & 0xF;
iargMask = imask >> 4;
GcTransitionCall transition = new GcTransitionCall((int)curOffs, Header.EbpFrame, callRegMask, iregMask);
AddNewTransition(transition);
if (callPndTab)
{
for (int i = 0; i < callPndTabCnt; i++)
{
uint pndOffs = NativeReader.DecodeUnsignedGc(image, ref offset);
uint stkOffs = val & ~byref_OFFSET_FLAG;
uint lowBit = val & byref_OFFSET_FLAG;
transition.PtrArgs.Add(new GcTransitionCall.PtrArg(pndOffs, 0));
}
}
else
{
if (callPndMask != 0)
{
transition.ArgMask = callPndMask;
}
if (iargMask != 0)
{
transition.IArgs = iargMask;
}
}
imask = lastSkip = 0;
}
/// <summary>
/// based on <a href="https://github.com/dotnet/coreclr/blob/master/src/gcdump/i386/gcdumpx86.cpp">GCDump::DumpGCTable</a>
/// </summary>
private void GetTransitionsEbpFrame(byte[] image, ref int offset)
{
while (true)
{
uint argMask = 0, byrefArgMask = 0;
uint regMask, byrefRegMask = 0;
uint argCnt = 0;
int argOffset = offset;
uint argTabSize;
uint val, nxt;
uint curOffs = 0;
// Get the next byte and check for a 'special' entry
uint encType = image[offset++];
GcTransitionCall transition = null;
switch (encType)
{
default:
// A tiny or small call entry
val = encType;
if ((val & 0x80) == 0x00)
{
if ((val & 0x0F) != 0)
{
// A tiny call entry
curOffs += (val & 0x0F);
regMask = (val & 0x70) >> 4;
argMask = 0;
}
else
{
Registers reg;
if ((val & 0x10) != 0)
{
reg = Registers.EDI;
}
else if ((val & 0x20) != 0)
{
reg = Registers.ESI;
}
else if ((val & 0x40) != 0)
{
reg = Registers.EBX;
}
else
{
throw new BadImageFormatException("Invalid register");
}
transition = new GcTransitionCall((int)curOffs);
transition.CallRegisters.Add(new GcTransitionCall.CallRegister(reg, false));
AddNewTransition(transition);
continue;
}
}
else
{
// A small call entry
curOffs += (val & 0x7F);
val = image[offset++];
regMask = val >> 5;
argMask = val & 0x1F;
}
break;
case 0xFD: // medium encoding
argMask = image[offset++];
val = image[offset++];
argMask |= (val & 0xF0) << 4;
nxt = image[offset++];
curOffs += (val & 0x0F) + ((nxt & 0x1F) << 4);
regMask = nxt >> 5; // EBX,ESI,EDI
break;
case 0xF9: // medium encoding with byrefs
curOffs += image[offset++];
val = image[offset++];
argMask = val & 0x1F;
regMask = val >> 5;
val = image[offset++];
byrefArgMask = val & 0x1F;
byrefRegMask = val >> 5;
break;
case 0xFE: // large encoding
case 0xFA: // large encoding with byrefs
val = image[offset++];
regMask = val & 0x7;
byrefRegMask = val >> 4;
curOffs += NativeReader.ReadUInt32(image, ref offset);
argMask = NativeReader.ReadUInt32(image, ref offset);
if (encType == 0xFA) // read byrefArgMask
{
byrefArgMask = NativeReader.ReadUInt32(image, ref offset);
}
break;
case 0xFB: // huge encoding
val = image[offset++];
regMask = val & 0x7;
byrefRegMask = val >> 4;
curOffs = NativeReader.ReadUInt32(image, ref offset);
argCnt = NativeReader.ReadUInt32(image, ref offset);
argTabSize = NativeReader.ReadUInt32(image, ref offset);
argOffset = offset;
offset += (int)argTabSize;
break;
case 0xFF:
return;
}
/*
* Here we have the following values:
*
* curOffs ... the code offset of the call
* regMask ... mask of live pointer register variables
* argMask ... bitmask of pushed pointer arguments
* byrefRegMask ... byref qualifier for regMask
* byrefArgMask ... byrer qualifier for argMask
*/
transition = new GcTransitionCall((int)curOffs, Header.EbpFrame, regMask, byrefRegMask);
AddNewTransition(transition);
if (argCnt != 0)
{
do
{
val = NativeReader.DecodeUnsignedGc(image, ref argOffset);
uint stkOffs = val & ~byref_OFFSET_FLAG;
uint lowBit = val & byref_OFFSET_FLAG;
transition.PtrArgs.Add(new GcTransitionCall.PtrArg(stkOffs, lowBit));
}while (--argCnt > 0);
}
else
{
transition.ArgMask = argMask;
if (byrefArgMask != 0)
{
transition.IArgs = byrefArgMask;
}
}
}
}