| // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- |
| /* Copyright (c) 2007, Google Inc. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| * --- |
| * Author: Joi Sigurdsson |
| * Author: Scott Francis |
| * |
| * Implementation of PreamblePatcher |
| */ |
| |
| #include "preamble_patcher.h" |
| |
| #include "mini_disassembler.h" |
| |
| // compatibility shims |
| #include "base/logging.h" |
| |
| // Definitions of assembly statements we need |
| #define ASM_JMP32REL 0xE9 |
| #define ASM_INT3 0xCC |
| #define ASM_JMP32ABS_0 0xFF |
| #define ASM_JMP32ABS_1 0x25 |
| #define ASM_JMP8REL 0xEB |
| #define ASM_JCC32REL_0 0x0F |
| #define ASM_JCC32REL_1_MASK 0x80 |
| #define ASM_NOP 0x90 |
| // X64 opcodes |
| #define ASM_REXW 0x48 |
| #define ASM_MOVRAX_IMM 0xB8 |
| #define ASM_JMP 0xFF |
| #define ASM_JMP_RAX 0xE0 |
| |
| namespace sidestep { |
| |
| PreamblePatcher::PreamblePage* PreamblePatcher::preamble_pages_ = NULL; |
| long PreamblePatcher::granularity_ = 0; |
| long PreamblePatcher::pagesize_ = 0; |
| bool PreamblePatcher::initialized_ = false; |
| |
| static const unsigned int kPreamblePageMagic = 0x4347414D; // "MAGC" |
| |
| // Handle a special case that we see with functions that point into an |
| // IAT table (including functions linked statically into the |
| // application): these function already starts with ASM_JMP32*. For |
| // instance, malloc() might be implemented as a JMP to __malloc(). |
| // This function follows the initial JMPs for us, until we get to the |
| // place where the actual code is defined. If we get to STOP_BEFORE, |
| // we return the address before stop_before. The stop_before_trampoline |
| // flag is used in 64-bit mode. If true, we will return the address |
| // before a trampoline is detected. Trampolines are defined as: |
| // |
| // nop |
| // mov rax, <replacement_function> |
| // jmp rax |
| // |
| // See PreamblePatcher::RawPatchWithStub for more information. |
| void* PreamblePatcher::ResolveTargetImpl(unsigned char* target, |
| unsigned char* stop_before, |
| bool stop_before_trampoline) { |
| if (target == NULL) |
| return NULL; |
| while (1) { |
| unsigned char* new_target; |
| if (target[0] == ASM_JMP32REL) { |
| // target[1-4] holds the place the jmp goes to, but it's |
| // relative to the next instruction. |
| int relative_offset; // Windows guarantees int is 4 bytes |
| SIDESTEP_ASSERT(sizeof(relative_offset) == 4); |
| memcpy(reinterpret_cast<void*>(&relative_offset), |
| reinterpret_cast<void*>(target + 1), 4); |
| new_target = target + 5 + relative_offset; |
| } else if (target[0] == ASM_JMP8REL) { |
| // Visual Studio 7.1 implements new[] as an 8 bit jump to new |
| signed char relative_offset; |
| memcpy(reinterpret_cast<void*>(&relative_offset), |
| reinterpret_cast<void*>(target + 1), 1); |
| new_target = target + 2 + relative_offset; |
| } else if (target[0] == ASM_JMP32ABS_0 && |
| target[1] == ASM_JMP32ABS_1) { |
| jmp32rel: |
| // Visual studio seems to sometimes do it this way instead of the |
| // previous way. Not sure what the rules are, but it was happening |
| // with operator new in some binaries. |
| void** new_target_v; |
| if (kIs64BitBinary) { |
| // In 64-bit mode JMPs are RIP-relative, not absolute |
| int target_offset; |
| memcpy(reinterpret_cast<void*>(&target_offset), |
| reinterpret_cast<void*>(target + 2), 4); |
| new_target_v = reinterpret_cast<void**>(target + target_offset + 6); |
| } else { |
| SIDESTEP_ASSERT(sizeof(new_target) == 4); |
| memcpy(&new_target_v, reinterpret_cast<void*>(target + 2), 4); |
| } |
| new_target = reinterpret_cast<unsigned char*>(*new_target_v); |
| } else if (kIs64BitBinary && target[0] == ASM_REXW |
| && target[1] == ASM_JMP32ABS_0 |
| && target[2] == ASM_JMP32ABS_1) { |
| // in Visual Studio 2012 we're seeing jump like that: |
| // rex.W jmpq *0x11d019(%rip) |
| // |
| // according to docs I have, rex prefix is actually unneeded and |
| // can be ignored. I.e. docs say for jumps like that operand |
| // already defaults to 64-bit. But clearly it breaks abs. jump |
| // detection above and we just skip rex |
| target++; |
| goto jmp32rel; |
| } else { |
| break; |
| } |
| if (new_target == stop_before) |
| break; |
| if (stop_before_trampoline && *new_target == ASM_NOP |
| && new_target[1] == ASM_REXW && new_target[2] == ASM_MOVRAX_IMM) |
| break; |
| target = new_target; |
| } |
| return target; |
| } |
| |
| // Special case scoped_ptr to avoid dependency on scoped_ptr below. |
| class DeleteUnsignedCharArray { |
| public: |
| DeleteUnsignedCharArray(unsigned char* array) : array_(array) { |
| } |
| |
| ~DeleteUnsignedCharArray() { |
| if (array_) { |
| PreamblePatcher::FreePreambleBlock(array_); |
| } |
| } |
| |
| unsigned char* Release() { |
| unsigned char* temp = array_; |
| array_ = NULL; |
| return temp; |
| } |
| |
| private: |
| unsigned char* array_; |
| }; |
| |
| SideStepError PreamblePatcher::RawPatchWithStubAndProtections( |
| void* target_function, void *replacement_function, |
| unsigned char* preamble_stub, unsigned long stub_size, |
| unsigned long* bytes_needed) { |
| // We need to be able to write to a process-local copy of the first |
| // MAX_PREAMBLE_STUB_SIZE bytes of target_function |
| DWORD old_target_function_protect = 0; |
| BOOL succeeded = ::VirtualProtect(reinterpret_cast<void*>(target_function), |
| MAX_PREAMBLE_STUB_SIZE, |
| PAGE_EXECUTE_READWRITE, |
| &old_target_function_protect); |
| if (!succeeded) { |
| SIDESTEP_ASSERT(false && "Failed to make page containing target function " |
| "copy-on-write."); |
| return SIDESTEP_ACCESS_DENIED; |
| } |
| |
| SideStepError error_code = RawPatchWithStub(target_function, |
| replacement_function, |
| preamble_stub, |
| stub_size, |
| bytes_needed); |
| |
| // Restore the protection of the first MAX_PREAMBLE_STUB_SIZE bytes of |
| // pTargetFunction to what they were before we started goofing around. |
| // We do this regardless of whether the patch succeeded or not. |
| succeeded = ::VirtualProtect(reinterpret_cast<void*>(target_function), |
| MAX_PREAMBLE_STUB_SIZE, |
| old_target_function_protect, |
| &old_target_function_protect); |
| if (!succeeded) { |
| SIDESTEP_ASSERT(false && |
| "Failed to restore protection to target function."); |
| // We must not return an error here because the function has |
| // likely actually been patched, and returning an error might |
| // cause our client code not to unpatch it. So we just keep |
| // going. |
| } |
| |
| if (SIDESTEP_SUCCESS != error_code) { // Testing RawPatchWithStub, above |
| SIDESTEP_ASSERT(false); |
| return error_code; |
| } |
| |
| // Flush the instruction cache to make sure the processor doesn't execute the |
| // old version of the instructions (before our patch). |
| // |
| // FlushInstructionCache is actually a no-op at least on |
| // single-processor XP machines. I'm not sure why this is so, but |
| // it is, yet I want to keep the call to the API here for |
| // correctness in case there is a difference in some variants of |
| // Windows/hardware. |
| succeeded = ::FlushInstructionCache(::GetCurrentProcess(), |
| target_function, |
| MAX_PREAMBLE_STUB_SIZE); |
| if (!succeeded) { |
| SIDESTEP_ASSERT(false && "Failed to flush instruction cache."); |
| // We must not return an error here because the function has actually |
| // been patched, and returning an error would likely cause our client |
| // code not to unpatch it. So we just keep going. |
| } |
| |
| return SIDESTEP_SUCCESS; |
| } |
| |
| SideStepError PreamblePatcher::RawPatch(void* target_function, |
| void* replacement_function, |
| void** original_function_stub) { |
| if (!target_function || !replacement_function || !original_function_stub || |
| (*original_function_stub) || target_function == replacement_function) { |
| SIDESTEP_ASSERT(false && "Preconditions not met"); |
| return SIDESTEP_INVALID_PARAMETER; |
| } |
| |
| BOOL succeeded = FALSE; |
| |
| // First, deal with a special case that we see with functions that |
| // point into an IAT table (including functions linked statically |
| // into the application): these function already starts with |
| // ASM_JMP32REL. For instance, malloc() might be implemented as a |
| // JMP to __malloc(). In that case, we replace the destination of |
| // the JMP (__malloc), rather than the JMP itself (malloc). This |
| // way we get the correct behavior no matter how malloc gets called. |
| void* new_target = ResolveTarget(target_function); |
| if (new_target != target_function) { |
| target_function = new_target; |
| } |
| |
| // In 64-bit mode, preamble_stub must be within 2GB of target function |
| // so that if target contains a jump, we can translate it. |
| unsigned char* preamble_stub = AllocPreambleBlockNear(target_function); |
| if (!preamble_stub) { |
| SIDESTEP_ASSERT(false && "Unable to allocate preamble-stub."); |
| return SIDESTEP_INSUFFICIENT_BUFFER; |
| } |
| |
| // Frees the array at end of scope. |
| DeleteUnsignedCharArray guard_preamble_stub(preamble_stub); |
| |
| SideStepError error_code = RawPatchWithStubAndProtections( |
| target_function, replacement_function, preamble_stub, |
| MAX_PREAMBLE_STUB_SIZE, NULL); |
| |
| if (SIDESTEP_SUCCESS != error_code) { |
| SIDESTEP_ASSERT(false); |
| return error_code; |
| } |
| |
| // Flush the instruction cache to make sure the processor doesn't execute the |
| // old version of the instructions (before our patch). |
| // |
| // FlushInstructionCache is actually a no-op at least on |
| // single-processor XP machines. I'm not sure why this is so, but |
| // it is, yet I want to keep the call to the API here for |
| // correctness in case there is a difference in some variants of |
| // Windows/hardware. |
| succeeded = ::FlushInstructionCache(::GetCurrentProcess(), |
| target_function, |
| MAX_PREAMBLE_STUB_SIZE); |
| if (!succeeded) { |
| SIDESTEP_ASSERT(false && "Failed to flush instruction cache."); |
| // We must not return an error here because the function has actually |
| // been patched, and returning an error would likely cause our client |
| // code not to unpatch it. So we just keep going. |
| } |
| |
| SIDESTEP_LOG("PreamblePatcher::RawPatch successfully patched."); |
| |
| // detach the scoped pointer so the memory is not freed |
| *original_function_stub = |
| reinterpret_cast<void*>(guard_preamble_stub.Release()); |
| return SIDESTEP_SUCCESS; |
| } |
| |
| SideStepError PreamblePatcher::Unpatch(void* target_function, |
| void* replacement_function, |
| void* original_function_stub) { |
| SIDESTEP_ASSERT(target_function && replacement_function && |
| original_function_stub); |
| if (!target_function || !replacement_function || |
| !original_function_stub) { |
| return SIDESTEP_INVALID_PARAMETER; |
| } |
| |
| // Before unpatching, target_function should be a JMP to |
| // replacement_function. If it's not, then either it's an error, or |
| // we're falling into the case where the original instruction was a |
| // JMP, and we patched the jumped_to address rather than the JMP |
| // itself. (For instance, if malloc() is just a JMP to __malloc(), |
| // we patched __malloc() and not malloc().) |
| unsigned char* target = reinterpret_cast<unsigned char*>(target_function); |
| target = reinterpret_cast<unsigned char*>( |
| ResolveTargetImpl( |
| target, reinterpret_cast<unsigned char*>(replacement_function), |
| true)); |
| // We should end at the function we patched. When we patch, we insert |
| // a ASM_JMP32REL instruction, so look for that as a sanity check. |
| if (target[0] != ASM_JMP32REL) { |
| SIDESTEP_ASSERT(false && |
| "target_function does not look like it was patched."); |
| return SIDESTEP_INVALID_PARAMETER; |
| } |
| |
| const unsigned int kRequiredTargetPatchBytes = 5; |
| |
| // We need to be able to write to a process-local copy of the first |
| // kRequiredTargetPatchBytes bytes of target_function |
| DWORD old_target_function_protect = 0; |
| BOOL succeeded = ::VirtualProtect(reinterpret_cast<void*>(target), |
| kRequiredTargetPatchBytes, |
| PAGE_EXECUTE_READWRITE, |
| &old_target_function_protect); |
| if (!succeeded) { |
| SIDESTEP_ASSERT(false && "Failed to make page containing target function " |
| "copy-on-write."); |
| return SIDESTEP_ACCESS_DENIED; |
| } |
| |
| unsigned char* preamble_stub = reinterpret_cast<unsigned char*>( |
| original_function_stub); |
| |
| // Disassemble the preamble of stub and copy the bytes back to target. |
| // If we've done any conditional jumps in the preamble we need to convert |
| // them back to the original REL8 jumps in the target. |
| MiniDisassembler disassembler; |
| unsigned int preamble_bytes = 0; |
| unsigned int target_bytes = 0; |
| while (target_bytes < kRequiredTargetPatchBytes) { |
| unsigned int cur_bytes = 0; |
| InstructionType instruction_type = |
| disassembler.Disassemble(preamble_stub + preamble_bytes, cur_bytes); |
| if (IT_JUMP == instruction_type) { |
| unsigned int jump_bytes = 0; |
| SideStepError jump_ret = SIDESTEP_JUMP_INSTRUCTION; |
| if (IsNearConditionalJump(preamble_stub + preamble_bytes, cur_bytes) || |
| IsNearRelativeJump(preamble_stub + preamble_bytes, cur_bytes) || |
| IsNearAbsoluteCall(preamble_stub + preamble_bytes, cur_bytes) || |
| IsNearRelativeCall(preamble_stub + preamble_bytes, cur_bytes)) { |
| jump_ret = PatchNearJumpOrCall(preamble_stub + preamble_bytes, |
| cur_bytes, target + target_bytes, |
| &jump_bytes, MAX_PREAMBLE_STUB_SIZE); |
| } |
| if (jump_ret == SIDESTEP_JUMP_INSTRUCTION) { |
| SIDESTEP_ASSERT(false && |
| "Found unsupported jump instruction in stub!!"); |
| return SIDESTEP_UNSUPPORTED_INSTRUCTION; |
| } |
| target_bytes += jump_bytes; |
| } else if (IT_GENERIC == instruction_type) { |
| if (IsMovWithDisplacement(preamble_stub + preamble_bytes, cur_bytes)) { |
| unsigned int mov_bytes = 0; |
| if (PatchMovWithDisplacement(preamble_stub + preamble_bytes, cur_bytes, |
| target + target_bytes, &mov_bytes, |
| MAX_PREAMBLE_STUB_SIZE) |
| != SIDESTEP_SUCCESS) { |
| SIDESTEP_ASSERT(false && |
| "Found unsupported generic instruction in stub!!"); |
| return SIDESTEP_UNSUPPORTED_INSTRUCTION; |
| } |
| } else { |
| memcpy(reinterpret_cast<void*>(target + target_bytes), |
| reinterpret_cast<void*>(reinterpret_cast<unsigned char*>( |
| original_function_stub) + preamble_bytes), cur_bytes); |
| target_bytes += cur_bytes; |
| } |
| } else { |
| SIDESTEP_ASSERT(false && |
| "Found unsupported instruction in stub!!"); |
| return SIDESTEP_UNSUPPORTED_INSTRUCTION; |
| } |
| preamble_bytes += cur_bytes; |
| } |
| |
| FreePreambleBlock(reinterpret_cast<unsigned char*>(original_function_stub)); |
| |
| // Restore the protection of the first kRequiredTargetPatchBytes bytes of |
| // target to what they were before we started goofing around. |
| succeeded = ::VirtualProtect(reinterpret_cast<void*>(target), |
| kRequiredTargetPatchBytes, |
| old_target_function_protect, |
| &old_target_function_protect); |
| |
| // Flush the instruction cache to make sure the processor doesn't execute the |
| // old version of the instructions (before our patch). |
| // |
| // See comment on FlushInstructionCache elsewhere in this file. |
| succeeded = ::FlushInstructionCache(::GetCurrentProcess(), |
| target, |
| MAX_PREAMBLE_STUB_SIZE); |
| if (!succeeded) { |
| SIDESTEP_ASSERT(false && "Failed to flush instruction cache."); |
| return SIDESTEP_UNEXPECTED; |
| } |
| |
| SIDESTEP_LOG("PreamblePatcher::Unpatch successfully unpatched."); |
| return SIDESTEP_SUCCESS; |
| } |
| |
| void PreamblePatcher::Initialize() { |
| if (!initialized_) { |
| SYSTEM_INFO si = { 0 }; |
| ::GetSystemInfo(&si); |
| granularity_ = si.dwAllocationGranularity; |
| pagesize_ = si.dwPageSize; |
| initialized_ = true; |
| } |
| } |
| |
| unsigned char* PreamblePatcher::AllocPreambleBlockNear(void* target) { |
| PreamblePage* preamble_page = preamble_pages_; |
| while (preamble_page != NULL) { |
| if (preamble_page->free_ != NULL) { |
| __int64 val = reinterpret_cast<__int64>(preamble_page) - |
| reinterpret_cast<__int64>(target); |
| if ((val > 0 && val + pagesize_ <= INT_MAX) || |
| (val < 0 && val >= INT_MIN)) { |
| break; |
| } |
| } |
| preamble_page = preamble_page->next_; |
| } |
| |
| // The free_ member of the page is used to store the next available block |
| // of memory to use or NULL if there are no chunks available, in which case |
| // we'll allocate a new page. |
| if (preamble_page == NULL || preamble_page->free_ == NULL) { |
| // Create a new preamble page and initialize the free list |
| preamble_page = reinterpret_cast<PreamblePage*>(AllocPageNear(target)); |
| SIDESTEP_ASSERT(preamble_page != NULL && "Could not allocate page!"); |
| void** pp = &preamble_page->free_; |
| unsigned char* ptr = reinterpret_cast<unsigned char*>(preamble_page) + |
| MAX_PREAMBLE_STUB_SIZE; |
| unsigned char* limit = reinterpret_cast<unsigned char*>(preamble_page) + |
| pagesize_; |
| while (ptr < limit) { |
| *pp = ptr; |
| pp = reinterpret_cast<void**>(ptr); |
| ptr += MAX_PREAMBLE_STUB_SIZE; |
| } |
| *pp = NULL; |
| // Insert the new page into the list |
| preamble_page->magic_ = kPreamblePageMagic; |
| preamble_page->next_ = preamble_pages_; |
| preamble_pages_ = preamble_page; |
| } |
| unsigned char* ret = reinterpret_cast<unsigned char*>(preamble_page->free_); |
| preamble_page->free_ = *(reinterpret_cast<void**>(preamble_page->free_)); |
| return ret; |
| } |
| |
| void PreamblePatcher::FreePreambleBlock(unsigned char* block) { |
| SIDESTEP_ASSERT(block != NULL); |
| SIDESTEP_ASSERT(granularity_ != 0); |
| uintptr_t ptr = reinterpret_cast<uintptr_t>(block); |
| ptr -= ptr & (granularity_ - 1); |
| PreamblePage* preamble_page = reinterpret_cast<PreamblePage*>(ptr); |
| SIDESTEP_ASSERT(preamble_page->magic_ == kPreamblePageMagic); |
| *(reinterpret_cast<void**>(block)) = preamble_page->free_; |
| preamble_page->free_ = block; |
| } |
| |
| void* PreamblePatcher::AllocPageNear(void* target) { |
| MEMORY_BASIC_INFORMATION mbi = { 0 }; |
| if (!::VirtualQuery(target, &mbi, sizeof(mbi))) { |
| SIDESTEP_ASSERT(false && "VirtualQuery failed on target address"); |
| return 0; |
| } |
| if (initialized_ == false) { |
| PreamblePatcher::Initialize(); |
| SIDESTEP_ASSERT(initialized_); |
| } |
| void* pv = NULL; |
| unsigned char* allocation_base = reinterpret_cast<unsigned char*>( |
| mbi.AllocationBase); |
| __int64 i = 1; |
| bool high_target = reinterpret_cast<__int64>(target) > UINT_MAX; |
| while (pv == NULL) { |
| __int64 val = reinterpret_cast<__int64>(allocation_base) - |
| (i * granularity_); |
| if (high_target && |
| reinterpret_cast<__int64>(target) - val > INT_MAX) { |
| // We're further than 2GB from the target |
| break; |
| } else if (val <= NULL) { |
| // Less than 0 |
| break; |
| } |
| pv = ::VirtualAlloc(reinterpret_cast<void*>(allocation_base - |
| (i++ * granularity_)), |
| pagesize_, MEM_COMMIT | MEM_RESERVE, |
| PAGE_EXECUTE_READWRITE); |
| } |
| |
| // We couldn't allocate low, try to allocate high |
| if (pv == NULL) { |
| i = 1; |
| // Round up to the next multiple of page granularity |
| allocation_base = reinterpret_cast<unsigned char*>( |
| (reinterpret_cast<__int64>(target) & |
| (~(granularity_ - 1))) + granularity_); |
| while (pv == NULL) { |
| __int64 val = reinterpret_cast<__int64>(allocation_base) + |
| (i * granularity_) - reinterpret_cast<__int64>(target); |
| if (val > INT_MAX || val < 0) { |
| // We're too far or we overflowed |
| break; |
| } |
| pv = ::VirtualAlloc(reinterpret_cast<void*>(allocation_base + |
| (i++ * granularity_)), |
| pagesize_, MEM_COMMIT | MEM_RESERVE, |
| PAGE_EXECUTE_READWRITE); |
| } |
| } |
| return pv; |
| } |
| |
| bool PreamblePatcher::IsShortConditionalJump( |
| unsigned char* target, |
| unsigned int instruction_size) { |
| return (*(target) & 0x70) == 0x70 && instruction_size == 2; |
| } |
| |
| bool PreamblePatcher::IsShortJump( |
| unsigned char* target, |
| unsigned int instruction_size) { |
| return target[0] == 0xeb && instruction_size == 2; |
| } |
| |
| bool PreamblePatcher::IsNearConditionalJump( |
| unsigned char* target, |
| unsigned int instruction_size) { |
| return *(target) == 0xf && (*(target + 1) & 0x80) == 0x80 && |
| instruction_size == 6; |
| } |
| |
| bool PreamblePatcher::IsNearRelativeJump( |
| unsigned char* target, |
| unsigned int instruction_size) { |
| return *(target) == 0xe9 && instruction_size == 5; |
| } |
| |
| bool PreamblePatcher::IsNearAbsoluteCall( |
| unsigned char* target, |
| unsigned int instruction_size) { |
| return *(target) == 0xff && (*(target + 1) & 0x10) == 0x10 && |
| instruction_size == 6; |
| } |
| |
| bool PreamblePatcher::IsNearRelativeCall( |
| unsigned char* target, |
| unsigned int instruction_size) { |
| return *(target) == 0xe8 && instruction_size == 5; |
| } |
| |
| bool PreamblePatcher::IsMovWithDisplacement( |
| unsigned char* target, |
| unsigned int instruction_size) { |
| // In this case, the ModRM byte's mod field will be 0 and r/m will be 101b (5) |
| return instruction_size == 7 && *target == 0x48 && *(target + 1) == 0x8b && |
| (*(target + 2) >> 6) == 0 && (*(target + 2) & 0x7) == 5; |
| } |
| |
| SideStepError PreamblePatcher::PatchShortConditionalJump( |
| unsigned char* source, |
| unsigned int instruction_size, |
| unsigned char* target, |
| unsigned int* target_bytes, |
| unsigned int target_size) { |
| // note: rel8 offset is signed. Thus we need to ask for signed char |
| // to negative offsets right |
| unsigned char* original_jump_dest = (source + 2) + static_cast<signed char>(source[1]); |
| unsigned char* stub_jump_from = target + 6; |
| __int64 fixup_jump_offset = original_jump_dest - stub_jump_from; |
| if (fixup_jump_offset > INT_MAX || fixup_jump_offset < INT_MIN) { |
| SIDESTEP_ASSERT(false && |
| "Unable to fix up short jump because target" |
| " is too far away."); |
| return SIDESTEP_JUMP_INSTRUCTION; |
| } |
| |
| *target_bytes = 6; |
| if (target_size > *target_bytes) { |
| // Convert the short jump to a near jump. |
| // |
| // 0f 8x xx xx xx xx = Jcc rel32off |
| unsigned short jmpcode = ((0x80 | (source[0] & 0xf)) << 8) | 0x0f; |
| memcpy(reinterpret_cast<void*>(target), |
| reinterpret_cast<void*>(&jmpcode), 2); |
| memcpy(reinterpret_cast<void*>(target + 2), |
| reinterpret_cast<void*>(&fixup_jump_offset), 4); |
| } |
| |
| return SIDESTEP_SUCCESS; |
| } |
| |
| SideStepError PreamblePatcher::PatchShortJump( |
| unsigned char* source, |
| unsigned int instruction_size, |
| unsigned char* target, |
| unsigned int* target_bytes, |
| unsigned int target_size) { |
| // note: rel8 offset is _signed_. Thus we need signed char here. |
| unsigned char* original_jump_dest = (source + 2) + static_cast<signed char>(source[1]); |
| unsigned char* stub_jump_from = target + 5; |
| __int64 fixup_jump_offset = original_jump_dest - stub_jump_from; |
| if (fixup_jump_offset > INT_MAX || fixup_jump_offset < INT_MIN) { |
| SIDESTEP_ASSERT(false && |
| "Unable to fix up short jump because target" |
| " is too far away."); |
| return SIDESTEP_JUMP_INSTRUCTION; |
| } |
| |
| *target_bytes = 5; |
| if (target_size > *target_bytes) { |
| // Convert the short jump to a near jump. |
| // |
| // e9 xx xx xx xx = jmp rel32off |
| target[0] = 0xe9; |
| memcpy(reinterpret_cast<void*>(target + 1), |
| reinterpret_cast<void*>(&fixup_jump_offset), 4); |
| } |
| |
| return SIDESTEP_SUCCESS; |
| } |
| |
| SideStepError PreamblePatcher::PatchNearJumpOrCall( |
| unsigned char* source, |
| unsigned int instruction_size, |
| unsigned char* target, |
| unsigned int* target_bytes, |
| unsigned int target_size) { |
| SIDESTEP_ASSERT(instruction_size == 5 || instruction_size == 6); |
| unsigned int jmp_offset_in_instruction = instruction_size == 5 ? 1 : 2; |
| unsigned char* original_jump_dest = reinterpret_cast<unsigned char *>( |
| reinterpret_cast<__int64>(source + instruction_size) + |
| *(reinterpret_cast<int*>(source + jmp_offset_in_instruction))); |
| unsigned char* stub_jump_from = target + instruction_size; |
| __int64 fixup_jump_offset = original_jump_dest - stub_jump_from; |
| if (fixup_jump_offset > INT_MAX || fixup_jump_offset < INT_MIN) { |
| SIDESTEP_ASSERT(false && |
| "Unable to fix up near jump because target" |
| " is too far away."); |
| return SIDESTEP_JUMP_INSTRUCTION; |
| } |
| |
| if ((fixup_jump_offset < SCHAR_MAX && fixup_jump_offset > SCHAR_MIN)) { |
| *target_bytes = 2; |
| if (target_size > *target_bytes) { |
| // If the new offset is in range, use a short jump instead of a near jump. |
| if (source[0] == ASM_JCC32REL_0 && |
| (source[1] & ASM_JCC32REL_1_MASK) == ASM_JCC32REL_1_MASK) { |
| unsigned short jmpcode = (static_cast<unsigned char>( |
| fixup_jump_offset) << 8) | (0x70 | (source[1] & 0xf)); |
| memcpy(reinterpret_cast<void*>(target), |
| reinterpret_cast<void*>(&jmpcode), |
| 2); |
| } else { |
| target[0] = ASM_JMP8REL; |
| target[1] = static_cast<unsigned char>(fixup_jump_offset); |
| } |
| } |
| } else { |
| *target_bytes = instruction_size; |
| if (target_size > *target_bytes) { |
| memcpy(reinterpret_cast<void*>(target), |
| reinterpret_cast<void*>(source), |
| jmp_offset_in_instruction); |
| memcpy(reinterpret_cast<void*>(target + jmp_offset_in_instruction), |
| reinterpret_cast<void*>(&fixup_jump_offset), |
| 4); |
| } |
| } |
| |
| return SIDESTEP_SUCCESS; |
| } |
| |
| SideStepError PreamblePatcher::PatchMovWithDisplacement( |
| unsigned char* source, |
| unsigned int instruction_size, |
| unsigned char* target, |
| unsigned int* target_bytes, |
| unsigned int target_size) { |
| SIDESTEP_ASSERT(instruction_size == 7); |
| const int mov_offset_in_instruction = 3; // 0x48 0x8b 0x0d <offset> |
| unsigned char* original_mov_dest = reinterpret_cast<unsigned char*>( |
| reinterpret_cast<__int64>(source + instruction_size) + |
| *(reinterpret_cast<int*>(source + mov_offset_in_instruction))); |
| unsigned char* stub_mov_from = target + instruction_size; |
| __int64 fixup_mov_offset = original_mov_dest - stub_mov_from; |
| if (fixup_mov_offset > INT_MAX || fixup_mov_offset < INT_MIN) { |
| SIDESTEP_ASSERT(false && |
| "Unable to fix up near MOV because target is too far away."); |
| return SIDESTEP_UNEXPECTED; |
| } |
| *target_bytes = instruction_size; |
| if (target_size > *target_bytes) { |
| memcpy(reinterpret_cast<void*>(target), |
| reinterpret_cast<void*>(source), |
| mov_offset_in_instruction); |
| memcpy(reinterpret_cast<void*>(target + mov_offset_in_instruction), |
| reinterpret_cast<void*>(&fixup_mov_offset), |
| 4); |
| } |
| return SIDESTEP_SUCCESS; |
| } |
| |
| }; // namespace sidestep |
