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Align stack on 16 byte boundary in hamsandwich trampolines.

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This commit is contained in:
Scott Ehlert 2014-05-31 05:33:50 -05:00
parent 3987085572
commit 423eb0499b
1 changed files with 62 additions and 1 deletions
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63
dlls/hamsandwich/Trampolines.h
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@ -57,6 +57,7 @@
#include <stdlib.h> // memalign
#include <stdio.h>
#include <am-utility.h>
namespace Trampolines
{
@ -79,6 +80,26 @@ namespace Trampolines
0x89, 0xE5, // mov ebp, esp
};
/**
* Align stack on 16 byte boundary
*/
const unsigned char codeAlignStack16[] = {
0x83, 0xE4, 0xF0, // and esp, 0xFFFFFFF0
};
/**
* Allocate stack space (8-bit) by adding to ESP
*/
const unsigned char codeAllocStack[] = {
0x83, 0xEC, 0xFF, // sub esp, 0xFF
};
/**
* Offset of codeAllocStack to modify at runtime
* to contain amount of stack space to allocate.
*/
const unsigned int codeAllocStackReplace = 2;
/**
* Takes a paramter from the trampoline's stack
* and pushes it onto the target's stack.
@ -154,14 +175,16 @@ namespace Trampolines
* Epilogue of a simple function
*/
const unsigned char codeEpilogue[] = {
0x89, 0xEC, // mov esp, ebp
0x5D, // pop ebp
0xC3 // ret
};
const unsigned char codeEpilogueN[] = {
0x89, 0xEC, // mov esp, ebp
0x5D, // pop ebp
0xC2, 0xCD, 0xAB // retn 0xABCD
};
const int codeEpilogueNReplace = 2;
const int codeEpilogueNReplace = 4;
const unsigned char codeBreakpoint[] = {
0xCC // int 3
@ -300,6 +323,42 @@ namespace Trampolines
Append(&code[0],sizeof(::Trampolines::Bytecode::codeEpilogueN));
};
/**
* Aligns stack on 16 byte boundary for functions that use aligned SSE instructions.
* This also allocates extra stack space to allow the specified number of slots to be used
* for function paramaters that will be pushed onto the stack.
*/
void AlignStack16(int slots)
{
const size_t stackNeeded = slots * sizeof(void *);
const size_t stackReserve = ke::Align(stackNeeded, 16);
const size_t stackExtra = stackReserve - stackNeeded;
// Stack space should fit in a byte
assert(stackExtra <= 0xFF);
const size_t codeAlignStackSize = sizeof(::Trampolines::Bytecode::codeAlignStack16);
const size_t codeAllocStackSize = sizeof(::Trampolines::Bytecode::codeAllocStack);
unsigned char code[codeAlignStackSize + codeAllocStackSize];
memcpy(&code[0], &::Trampolines::Bytecode::codeAlignStack16[0], codeAlignStackSize);
if (stackExtra > 0)
{
unsigned char *c = &code[codeAlignStackSize];
memcpy(c, &::Trampolines::Bytecode::codeAllocStack[0], codeAllocStackSize);
c += ::Trampolines::Bytecode::codeAllocStackReplace;
*c = (unsigned char)stackExtra;
Append(&code[0], codeAlignStackSize + codeAllocStackSize);
}
else
{
Append(&code[0], codeAlignStackSize);
}
}
/**
* Pushes the "this" pointer onto the callee stack. Pushes ECX for MSVC, and param0 on GCC.
*/
@ -552,10 +611,12 @@ inline void *CreateGenericTrampoline(bool thiscall, bool voidcall, bool retbuf,
if (thiscall)
{
tramp.ThisPrologue();
tramp.AlignStack16(paramcount + 2); // Param count + this ptr + extra ptr
}
else
{
tramp.Prologue();
tramp.AlignStack16(paramcount + 1); // Param count + extra ptr
}
while (paramcount)