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/***************************************************************************************************
Zyan Disassembler Library (Zydis)
Original Author : Joel Hoener
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
***************************************************************************************************/
/**
* @file
*
* Example on assembling a basic function returning `0x1337` in `rax`.
*/
#include <Zydis/Zydis.h>
#include <Zycore/LibC.h>
#include <Zycore/API/Memory.h>
#include <inttypes.h>
/* ============================================================================================== */
/* Entry point */
/* ============================================================================================== */
static void ExpectSuccess(ZyanStatus status)
{
if (ZYAN_FAILED(status))
{
fprintf(stderr, "Something failed: 0x%08X\n", status);
exit(EXIT_FAILURE);
}
}
static void AppendInstruction(const ZydisEncoderRequest* req, ZyanU8** buffer,
ZyanUSize* buffer_length)
{
assert(req);
assert(buffer);
assert(buffer_length);
ZyanUSize instr_length = *buffer_length;
ExpectSuccess(ZydisEncoderEncodeInstruction(req, *buffer, &instr_length));
*buffer += instr_length;
*buffer_length -= instr_length;
}
static ZyanUSize AssembleCode(ZyanU8* buffer, ZyanUSize buffer_length)
{
assert(buffer);
assert(buffer_length);
ZyanU8* write_ptr = buffer;
ZyanUSize remaining_length = buffer_length;
// Assemble `mov rax, 0x1337`.
ZydisEncoderRequest req;
memset(&req, 0, sizeof(req));
req.mnemonic = ZYDIS_MNEMONIC_MOV;
req.machine_mode = ZYDIS_MACHINE_MODE_LONG_64;
req.operand_count = 2;
req.operands[0].type = ZYDIS_OPERAND_TYPE_REGISTER;
req.operands[0].reg.value = ZYDIS_REGISTER_RAX;
req.operands[1].type = ZYDIS_OPERAND_TYPE_IMMEDIATE;
req.operands[1].imm.u = 0x1337;
AppendInstruction(&req, &write_ptr, &remaining_length);
// Assemble `ret`.
memset(&req, 0, sizeof(req));
req.mnemonic = ZYDIS_MNEMONIC_RET;
req.machine_mode = ZYDIS_MACHINE_MODE_LONG_64;
AppendInstruction(&req, &write_ptr, &remaining_length);
return buffer_length - remaining_length;
}
int main(void)
{
// Allocate 2 pages of memory. We won't need nearly as much, but it simplifies
// re-protecting the memory to RWX later.
const ZyanUSize page_size = 0x1000;
const ZyanUSize alloc_size = page_size * 2;
ZyanU8* buffer = malloc(alloc_size);
// Assemble our function.
const ZyanUSize length = AssembleCode(buffer, alloc_size);
// Print a hex-dump of the assembled code.
puts("Created byte-code:");
for (ZyanUSize i = 0; i < length; ++i)
{
printf("%02X ", buffer[i]);
}
puts("");
#ifdef ZYAN_X64
// Align pointer to typical page size.
void* aligned = (void*)((ZyanUPointer)buffer & ~(page_size-1));
// Re-protect the heap region as RWX. Don't do this at home, kids!
ExpectSuccess(ZyanMemoryVirtualProtect(aligned, alloc_size, ZYAN_PAGE_EXECUTE_READWRITE));
// Create a function pointer for our buffer.
typedef ZyanU64(*FnPtr)(void);
const FnPtr func_ptr = (FnPtr)(uintptr_t)buffer;
// Call the function!
const ZyanU64 result = func_ptr();
printf("Return value of JITed code: 0x%016" PRIx64 "\n", result);
#endif
}
/* ============================================================================================== */
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