/******************************************************************************* mach_override.c Copyright (c) 2003-2009 Jonathan 'Wolf' Rentzsch: Some rights reserved: ***************************************************************************/ #ifdef __APPLE__ #include "mach_override.h" #include #include #include #include #include #include //#define DEBUG_DISASM 1 #undef DEBUG_DISASM /************************** * * Constants * **************************/ #pragma mark - #pragma mark (Constants) #if defined(__ppc__) || defined(__POWERPC__) long kIslandTemplate[] = { 0x9001FFFC, // stw r0,-4(SP) 0x3C00DEAD, // lis r0,0xDEAD 0x6000BEEF, // ori r0,r0,0xBEEF 0x7C0903A6, // mtctr r0 0x8001FFFC, // lwz r0,-4(SP) 0x60000000, // nop ; optionally replaced 0x4E800420 // bctr }; #define kAddressHi 3 #define kAddressLo 5 #define kInstructionHi 10 #define kInstructionLo 11 #elif defined(__i386__) #define kOriginalInstructionsSize 16 char kIslandTemplate[] = { // kOriginalInstructionsSize nop instructions so that we // should have enough space to host original instructions 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, // Now the real jump instruction 0xE9, 0xEF, 0xBE, 0xAD, 0xDE }; #define kInstructions 0 #define kJumpAddress kInstructions + kOriginalInstructionsSize + 1 #elif defined(__x86_64__) #define kOriginalInstructionsSize 32 #define kJumpAddress kOriginalInstructionsSize + 6 char kIslandTemplate[] = { // kOriginalInstructionsSize nop instructions so that we // should have enough space to host original instructions 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, // Now the real jump instruction 0xFF, 0x25, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; #endif #define kAllocateHigh 1 #define kAllocateNormal 0 /************************** * * Data Types * **************************/ #pragma mark - #pragma mark (Data Types) typedef struct { char instructions[sizeof(kIslandTemplate)]; int allocatedHigh; } BranchIsland; /************************** * * Funky Protos * **************************/ #pragma mark - #pragma mark (Funky Protos) mach_error_t allocateBranchIsland( BranchIsland **island, int allocateHigh, void *originalFunctionAddress) __attribute__((visibility("hidden"))); mach_error_t freeBranchIsland( BranchIsland *island ) __attribute__((visibility("hidden"))); mach_error_t defaultIslandMalloc( void **ptr, size_t unused_size, void *hint) __attribute__((visibility("hidden"))); mach_error_t defaultIslandFree( void *ptr) __attribute__((visibility("hidden"))); #if defined(__ppc__) || defined(__POWERPC__) mach_error_t setBranchIslandTarget( BranchIsland *island, const void *branchTo, long instruction ) __attribute__((visibility("hidden"))); #endif #if defined(__i386__) || defined(__x86_64__) mach_error_t setBranchIslandTarget_i386( BranchIsland *island, const void *branchTo, char* instructions ) __attribute__((visibility("hidden"))); void atomic_mov64( uint64_t *targetAddress, uint64_t value ) __attribute__((visibility("hidden"))); static Boolean eatKnownInstructions( unsigned char *code, uint64_t *newInstruction, int *howManyEaten, char *originalInstructions, int *originalInstructionCount, uint8_t *originalInstructionSizes ) __attribute__((visibility("hidden"))); static void fixupInstructions( void *originalFunction, void *escapeIsland, void *instructionsToFix, int instructionCount, uint8_t *instructionSizes ) __attribute__((visibility("hidden"))); #ifdef DEBUG_DISASM static void dump16Bytes( void *ptr); #endif // DEBUG_DISASM #endif /******************************************************************************* * * Interface * *******************************************************************************/ #pragma mark - #pragma mark (Interface) #if defined(__i386__) || defined(__x86_64__) mach_error_t makeIslandExecutable(void *address) { mach_error_t err = err_none; vm_size_t pageSize; host_page_size( mach_host_self(), &pageSize ); uintptr_t page = (uintptr_t)address & ~(uintptr_t)(pageSize-1); int e = err_none; e |= mprotect((void *)page, pageSize, PROT_EXEC | PROT_READ | PROT_WRITE); e |= msync((void *)page, pageSize, MS_INVALIDATE ); if (e) { err = err_cannot_override; } return err; } #endif mach_error_t defaultIslandMalloc( void **ptr, size_t unused_size, void *hint) { return allocateBranchIsland( (BranchIsland**)ptr, kAllocateHigh, hint ); } mach_error_t defaultIslandFree( void *ptr) { return freeBranchIsland(ptr); } mach_error_t __asan_mach_override_ptr( void *originalFunctionAddress, const void *overrideFunctionAddress, void **originalFunctionReentryIsland ) { return __asan_mach_override_ptr_custom(originalFunctionAddress, overrideFunctionAddress, originalFunctionReentryIsland, defaultIslandMalloc, defaultIslandFree); } mach_error_t __asan_mach_override_ptr_custom( void *originalFunctionAddress, const void *overrideFunctionAddress, void **originalFunctionReentryIsland, island_malloc *alloc, island_free *dealloc) { assert( originalFunctionAddress ); assert( overrideFunctionAddress ); // this addresses overriding such functions as AudioOutputUnitStart() // test with modified DefaultOutputUnit project #if defined(__x86_64__) for(;;){ if(*(uint16_t*)originalFunctionAddress==0x25FF) // jmp qword near [rip+0x????????] originalFunctionAddress=*(void**)((char*)originalFunctionAddress+6+*(int32_t *)((uint16_t*)originalFunctionAddress+1)); else break; } #elif defined(__i386__) for(;;){ if(*(uint16_t*)originalFunctionAddress==0x25FF) // jmp *0x???????? originalFunctionAddress=**(void***)((uint16_t*)originalFunctionAddress+1); else break; } #endif #ifdef DEBUG_DISASM { fprintf(stderr, "Replacing function at %p\n", originalFunctionAddress); fprintf(stderr, "First 16 bytes of the function: "); unsigned char *orig = (unsigned char *)originalFunctionAddress; int i; for (i = 0; i < 16; i++) { fprintf(stderr, "%x ", (unsigned int) orig[i]); } fprintf(stderr, "\n"); fprintf(stderr, "To disassemble, save the following function as disas.c" " and run:\n gcc -c disas.c && gobjdump -d disas.o\n" "The first 16 bytes of the original function will start" " after four nop instructions.\n"); fprintf(stderr, "\nvoid foo() {\n asm volatile(\"nop;nop;nop;nop;\");\n"); int j = 0; for (j = 0; j < 2; j++) { fprintf(stderr, " asm volatile(\".byte "); for (i = 8 * j; i < 8 * (j+1) - 1; i++) { fprintf(stderr, "0x%x, ", (unsigned int) orig[i]); } fprintf(stderr, "0x%x;\");\n", (unsigned int) orig[8 * (j+1) - 1]); } fprintf(stderr, "}\n\n"); } #endif long *originalFunctionPtr = (long*) originalFunctionAddress; mach_error_t err = err_none; #if defined(__ppc__) || defined(__POWERPC__) // Ensure first instruction isn't 'mfctr'. #define kMFCTRMask 0xfc1fffff #define kMFCTRInstruction 0x7c0903a6 long originalInstruction = *originalFunctionPtr; if( !err && ((originalInstruction & kMFCTRMask) == kMFCTRInstruction) ) err = err_cannot_override; #elif defined(__i386__) || defined(__x86_64__) int eatenCount = 0; int originalInstructionCount = 0; char originalInstructions[kOriginalInstructionsSize]; uint8_t originalInstructionSizes[kOriginalInstructionsSize]; uint64_t jumpRelativeInstruction = 0; // JMP Boolean overridePossible = eatKnownInstructions ((unsigned char *)originalFunctionPtr, &jumpRelativeInstruction, &eatenCount, originalInstructions, &originalInstructionCount, originalInstructionSizes ); #ifdef DEBUG_DISASM if (!overridePossible) fprintf(stderr, "overridePossible = false @%d\n", __LINE__); #endif if (eatenCount > kOriginalInstructionsSize) { #ifdef DEBUG_DISASM fprintf(stderr, "Too many instructions eaten\n"); #endif overridePossible = false; } if (!overridePossible) err = err_cannot_override; if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__); #endif // Make the original function implementation writable. if( !err ) { err = vm_protect( mach_task_self(), (vm_address_t) originalFunctionPtr, 8, false, (VM_PROT_ALL | VM_PROT_COPY) ); if( err ) err = vm_protect( mach_task_self(), (vm_address_t) originalFunctionPtr, 8, false, (VM_PROT_DEFAULT | VM_PROT_COPY) ); } if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__); // Allocate and target the escape island to the overriding function. BranchIsland *escapeIsland = NULL; if( !err ) err = alloc( (void**)&escapeIsland, sizeof(BranchIsland), originalFunctionAddress ); if ( err ) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__); #if defined(__ppc__) || defined(__POWERPC__) if( !err ) err = setBranchIslandTarget( escapeIsland, overrideFunctionAddress, 0 ); // Build the branch absolute instruction to the escape island. long branchAbsoluteInstruction = 0; // Set to 0 just to silence warning. if( !err ) { long escapeIslandAddress = ((long) escapeIsland) & 0x3FFFFFF; branchAbsoluteInstruction = 0x48000002 | escapeIslandAddress; } #elif defined(__i386__) || defined(__x86_64__) if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__); if( !err ) err = setBranchIslandTarget_i386( escapeIsland, overrideFunctionAddress, 0 ); if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__); // Build the jump relative instruction to the escape island #endif #if defined(__i386__) || defined(__x86_64__) if (!err) { uint32_t addressOffset = ((char*)escapeIsland - (char*)originalFunctionPtr - 5); addressOffset = OSSwapInt32(addressOffset); jumpRelativeInstruction |= 0xE900000000000000LL; jumpRelativeInstruction |= ((uint64_t)addressOffset & 0xffffffff) << 24; jumpRelativeInstruction = OSSwapInt64(jumpRelativeInstruction); } #endif // Optionally allocate & return the reentry island. This may contain relocated // jmp instructions and so has all the same addressing reachability requirements // the escape island has to the original function, except the escape island is // technically our original function. BranchIsland *reentryIsland = NULL; if( !err && originalFunctionReentryIsland ) { err = alloc( (void**)&reentryIsland, sizeof(BranchIsland), escapeIsland); if( !err ) *originalFunctionReentryIsland = reentryIsland; } #if defined(__ppc__) || defined(__POWERPC__) // Atomically: // o If the reentry island was allocated: // o Insert the original instruction into the reentry island. // o Target the reentry island at the 2nd instruction of the // original function. // o Replace the original instruction with the branch absolute. if( !err ) { int escapeIslandEngaged = false; do { if( reentryIsland ) err = setBranchIslandTarget( reentryIsland, (void*) (originalFunctionPtr+1), originalInstruction ); if( !err ) { escapeIslandEngaged = CompareAndSwap( originalInstruction, branchAbsoluteInstruction, (UInt32*)originalFunctionPtr ); if( !escapeIslandEngaged ) { // Someone replaced the instruction out from under us, // re-read the instruction, make sure it's still not // 'mfctr' and try again. originalInstruction = *originalFunctionPtr; if( (originalInstruction & kMFCTRMask) == kMFCTRInstruction) err = err_cannot_override; } } } while( !err && !escapeIslandEngaged ); } #elif defined(__i386__) || defined(__x86_64__) // Atomically: // o If the reentry island was allocated: // o Insert the original instructions into the reentry island. // o Target the reentry island at the first non-replaced // instruction of the original function. // o Replace the original first instructions with the jump relative. // // Note that on i386, we do not support someone else changing the code under our feet if ( !err ) { fixupInstructions(originalFunctionPtr, reentryIsland, originalInstructions, originalInstructionCount, originalInstructionSizes ); if( reentryIsland ) err = setBranchIslandTarget_i386( reentryIsland, (void*) ((char *)originalFunctionPtr+eatenCount), originalInstructions ); // try making islands executable before planting the jmp #if defined(__x86_64__) || defined(__i386__) if( !err ) err = makeIslandExecutable(escapeIsland); if( !err && reentryIsland ) err = makeIslandExecutable(reentryIsland); #endif if ( !err ) atomic_mov64((uint64_t *)originalFunctionPtr, jumpRelativeInstruction); } #endif // Clean up on error. if( err ) { if( reentryIsland ) dealloc( reentryIsland ); if( escapeIsland ) dealloc( escapeIsland ); } #ifdef DEBUG_DISASM { fprintf(stderr, "First 16 bytes of the function after slicing: "); unsigned char *orig = (unsigned char *)originalFunctionAddress; int i; for (i = 0; i < 16; i++) { fprintf(stderr, "%x ", (unsigned int) orig[i]); } fprintf(stderr, "\n"); } #endif return err; } /******************************************************************************* * * Implementation * *******************************************************************************/ #pragma mark - #pragma mark (Implementation) /***************************************************************************//** Implementation: Allocates memory for a branch island. @param island <- The allocated island. @param allocateHigh -> Whether to allocate the island at the end of the address space (for use with the branch absolute instruction). @result <- mach_error_t ***************************************************************************/ mach_error_t allocateBranchIsland( BranchIsland **island, int allocateHigh, void *originalFunctionAddress) { assert( island ); mach_error_t err = err_none; if( allocateHigh ) { vm_size_t pageSize; err = host_page_size( mach_host_self(), &pageSize ); if( !err ) { assert( sizeof( BranchIsland ) <= pageSize ); #if defined(__ppc__) || defined(__POWERPC__) vm_address_t first = 0xfeffffff; vm_address_t last = 0xfe000000 + pageSize; #elif defined(__x86_64__) vm_address_t first = ((uint64_t)originalFunctionAddress & ~(uint64_t)(((uint64_t)1 << 31) - 1)) | ((uint64_t)1 << 31); // start in the middle of the page? vm_address_t last = 0x0; #else vm_address_t first = 0xffc00000; vm_address_t last = 0xfffe0000; #endif vm_address_t page = first; int allocated = 0; vm_map_t task_self = mach_task_self(); while( !err && !allocated && page != last ) { err = vm_allocate( task_self, &page, pageSize, 0 ); if( err == err_none ) allocated = 1; else if( err == KERN_NO_SPACE ) { #if defined(__x86_64__) page -= pageSize; #else page += pageSize; #endif err = err_none; } } if( allocated ) *island = (BranchIsland*) page; else if( !allocated && !err ) err = KERN_NO_SPACE; } } else { void *block = malloc( sizeof( BranchIsland ) ); if( block ) *island = block; else err = KERN_NO_SPACE; } if( !err ) (**island).allocatedHigh = allocateHigh; return err; } /***************************************************************************//** Implementation: Deallocates memory for a branch island. @param island -> The island to deallocate. @result <- mach_error_t ***************************************************************************/ mach_error_t freeBranchIsland( BranchIsland *island ) { assert( island ); assert( (*(long*)&island->instructions[0]) == kIslandTemplate[0] ); assert( island->allocatedHigh ); mach_error_t err = err_none; if( island->allocatedHigh ) { vm_size_t pageSize; err = host_page_size( mach_host_self(), &pageSize ); if( !err ) { assert( sizeof( BranchIsland ) <= pageSize ); err = vm_deallocate( mach_task_self(), (vm_address_t) island, pageSize ); } } else { free( island ); } return err; } /***************************************************************************//** Implementation: Sets the branch island's target, with an optional instruction. @param island -> The branch island to insert target into. @param branchTo -> The address of the target. @param instruction -> Optional instruction to execute prior to branch. Set to zero for nop. @result <- mach_error_t ***************************************************************************/ #if defined(__ppc__) || defined(__POWERPC__) mach_error_t setBranchIslandTarget( BranchIsland *island, const void *branchTo, long instruction ) { // Copy over the template code. bcopy( kIslandTemplate, island->instructions, sizeof( kIslandTemplate ) ); // Fill in the address. ((short*)island->instructions)[kAddressLo] = ((long) branchTo) & 0x0000FFFF; ((short*)island->instructions)[kAddressHi] = (((long) branchTo) >> 16) & 0x0000FFFF; // Fill in the (optional) instuction. if( instruction != 0 ) { ((short*)island->instructions)[kInstructionLo] = instruction & 0x0000FFFF; ((short*)island->instructions)[kInstructionHi] = (instruction >> 16) & 0x0000FFFF; } //MakeDataExecutable( island->instructions, sizeof( kIslandTemplate ) ); msync( island->instructions, sizeof( kIslandTemplate ), MS_INVALIDATE ); return err_none; } #endif #if defined(__i386__) mach_error_t setBranchIslandTarget_i386( BranchIsland *island, const void *branchTo, char* instructions ) { // Copy over the template code. bcopy( kIslandTemplate, island->instructions, sizeof( kIslandTemplate ) ); // copy original instructions if (instructions) { bcopy (instructions, island->instructions + kInstructions, kOriginalInstructionsSize); } // Fill in the address. int32_t addressOffset = (char *)branchTo - (island->instructions + kJumpAddress + 4); *((int32_t *)(island->instructions + kJumpAddress)) = addressOffset; msync( island->instructions, sizeof( kIslandTemplate ), MS_INVALIDATE ); return err_none; } #elif defined(__x86_64__) mach_error_t setBranchIslandTarget_i386( BranchIsland *island, const void *branchTo, char* instructions ) { // Copy over the template code. bcopy( kIslandTemplate, island->instructions, sizeof( kIslandTemplate ) ); // Copy original instructions. if (instructions) { bcopy (instructions, island->instructions, kOriginalInstructionsSize); } // Fill in the address. *((uint64_t *)(island->instructions + kJumpAddress)) = (uint64_t)branchTo; msync( island->instructions, sizeof( kIslandTemplate ), MS_INVALIDATE ); return err_none; } #endif #if defined(__i386__) || defined(__x86_64__) // simplistic instruction matching typedef struct { unsigned int length; // max 15 unsigned char mask[15]; // sequence of bytes in memory order unsigned char constraint[15]; // sequence of bytes in memory order } AsmInstructionMatch; #if defined(__i386__) static AsmInstructionMatch possibleInstructions[] = { { 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xE9, 0x00, 0x00, 0x00, 0x00} }, // jmp 0x???????? { 0x5, {0xFF, 0xFF, 0xFF, 0xFF, 0xFF}, {0x55, 0x89, 0xe5, 0xc9, 0xc3} }, // push %esp; mov %esp,%ebp; leave; ret { 0x1, {0xFF}, {0x90} }, // nop { 0x1, {0xF8}, {0x50} }, // push %reg { 0x2, {0xFF, 0xFF}, {0x89, 0xE5} }, // mov %esp,%ebp { 0x3, {0xFF, 0xFF, 0xFF}, {0x89, 0x1C, 0x24} }, // mov %ebx,(%esp) { 0x3, {0xFF, 0xFF, 0x00}, {0x83, 0xEC, 0x00} }, // sub 0x??, %esp { 0x6, {0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00}, {0x81, 0xEC, 0x00, 0x00, 0x00, 0x00} }, // sub 0x??, %esp with 32bit immediate { 0x2, {0xFF, 0xFF}, {0x31, 0xC0} }, // xor %eax, %eax { 0x3, {0xFF, 0x4F, 0x00}, {0x8B, 0x45, 0x00} }, // mov $imm(%ebp), %reg { 0x3, {0xFF, 0x4C, 0x00}, {0x8B, 0x40, 0x00} }, // mov $imm(%eax-%edx), %reg { 0x3, {0xFF, 0xCF, 0x00}, {0x8B, 0x4D, 0x00} }, // mov $imm(%rpb), %reg { 0x3, {0xFF, 0x4F, 0x00}, {0x8A, 0x4D, 0x00} }, // mov $imm(%ebp), %cl { 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x8B, 0x4C, 0x24, 0x00} }, // mov $imm(%esp), %ecx { 0x4, {0xFF, 0x00, 0x00, 0x00}, {0x8B, 0x00, 0x00, 0x00} }, // mov r16,r/m16 or r32,r/m32 { 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xB9, 0x00, 0x00, 0x00, 0x00} }, // mov $imm, %ecx { 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xB8, 0x00, 0x00, 0x00, 0x00} }, // mov $imm, %eax { 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x66, 0x0F, 0xEF, 0x00} }, // pxor xmm2/128, xmm1 { 0x2, {0xFF, 0xFF}, {0xDB, 0xE3} }, // fninit { 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xE8, 0x00, 0x00, 0x00, 0x00} }, // call $imm { 0x0 } }; #elif defined(__x86_64__) // TODO(glider): disassembling the "0x48, 0x89" sequences is trickier than it's done below. // If it stops working, refer to http://ref.x86asm.net/geek.html#modrm_byte_32_64 to do it // more accurately. // Note: 0x48 is in fact the REX.W prefix, but it might be wrong to treat it as a separate // instruction. static AsmInstructionMatch possibleInstructions[] = { { 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xE9, 0x00, 0x00, 0x00, 0x00} }, // jmp 0x???????? { 0x1, {0xFF}, {0x90} }, // nop { 0x1, {0xF8}, {0x50} }, // push %rX { 0x1, {0xFF}, {0x65} }, // GS prefix { 0x3, {0xFF, 0xFF, 0xFF}, {0x48, 0x89, 0xE5} }, // mov %rsp,%rbp { 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x48, 0x83, 0xEC, 0x00} }, // sub 0x??, %rsp { 0x4, {0xFB, 0xFF, 0x07, 0x00}, {0x48, 0x89, 0x05, 0x00} }, // move onto rbp { 0x3, {0xFB, 0xFF, 0x00}, {0x48, 0x89, 0x00} }, // mov %reg, %reg { 0x3, {0xFB, 0xFF, 0x00}, {0x49, 0x89, 0x00} }, // mov %reg, %reg (REX.WB) { 0x2, {0xFF, 0x00}, {0x41, 0x00} }, // push %rXX { 0x2, {0xFF, 0x00}, {0x85, 0x00} }, // test %rX,%rX { 0x2, {0xFF, 0x00}, {0x77, 0x00} }, // ja $i8 { 0x2, {0xFF, 0x00}, {0x74, 0x00} }, // je $i8 { 0x5, {0xF8, 0x00, 0x00, 0x00, 0x00}, {0xB8, 0x00, 0x00, 0x00, 0x00} }, // mov $imm, %reg { 0x3, {0xFF, 0xFF, 0x00}, {0xFF, 0x77, 0x00} }, // pushq $imm(%rdi) { 0x2, {0xFF, 0xFF}, {0x31, 0xC0} }, // xor %eax, %eax { 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0x25, 0x00, 0x00, 0x00, 0x00} }, // and $imm, %eax { 0x3, {0xFF, 0xFF, 0xFF}, {0x80, 0x3F, 0x00} }, // cmpb $imm, (%rdi) { 0x8, {0xFF, 0xFF, 0xCF, 0xFF, 0x00, 0x00, 0x00, 0x00}, {0x48, 0x8B, 0x04, 0x25, 0x00, 0x00, 0x00, 0x00}, }, // mov $imm, %{rax,rdx,rsp,rsi} { 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x48, 0x83, 0xFA, 0x00}, }, // cmp $i8, %rdx { 0x4, {0xFF, 0xFF, 0x00, 0x00}, {0x83, 0x7f, 0x00, 0x00}, }, // cmpl $imm, $imm(%rdi) { 0xa, {0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, {0x48, 0xB8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00} }, // mov $imm, %rax { 0x6, {0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00}, {0x81, 0xE6, 0x00, 0x00, 0x00, 0x00} }, // and $imm, %esi { 0x6, {0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00}, {0xFF, 0x25, 0x00, 0x00, 0x00, 0x00} }, // jmpq *(%rip) { 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x66, 0x0F, 0xEF, 0x00} }, // pxor xmm2/128, xmm1 { 0x2, {0xFF, 0x00}, {0x89, 0x00} }, // mov r/m32,r32 or r/m16,r16 { 0x3, {0xFF, 0xFF, 0xFF}, {0x49, 0x89, 0xF8} }, // mov %rdi,%r8 { 0x3, {0xFF, 0xFF, 0x00}, {0xFF, 0x77, 0x00} }, // pushq $imm(%rdi) { 0x2, {0xFF, 0xFF}, {0xDB, 0xE3} }, // fninit { 0x0 } }; #endif static Boolean codeMatchesInstruction(unsigned char *code, AsmInstructionMatch* instruction) { Boolean match = true; size_t i; assert(instruction); #ifdef DEBUG_DISASM fprintf(stderr, "Matching: "); #endif for (i=0; ilength; i++) { unsigned char mask = instruction->mask[i]; unsigned char constraint = instruction->constraint[i]; unsigned char codeValue = code[i]; #ifdef DEBUG_DISASM fprintf(stderr, "%x ", (unsigned)codeValue); #endif match = ((codeValue & mask) == constraint); if (!match) break; } #ifdef DEBUG_DISASM if (match) { fprintf(stderr, " OK\n"); } else { fprintf(stderr, " FAIL\n"); } #endif return match; } #if defined(__i386__) || defined(__x86_64__) static Boolean eatKnownInstructions( unsigned char *code, uint64_t *newInstruction, int *howManyEaten, char *originalInstructions, int *originalInstructionCount, uint8_t *originalInstructionSizes ) { Boolean allInstructionsKnown = true; int totalEaten = 0; unsigned char* ptr = code; int remainsToEat = 5; // a JMP instruction takes 5 bytes int instructionIndex = 0; if (howManyEaten) *howManyEaten = 0; if (originalInstructionCount) *originalInstructionCount = 0; while (remainsToEat > 0) { Boolean curInstructionKnown = false; // See if instruction matches one we know AsmInstructionMatch* curInstr = possibleInstructions; do { if ((curInstructionKnown = codeMatchesInstruction(ptr, curInstr))) break; curInstr++; } while (curInstr->length > 0); // if all instruction matches failed, we don't know current instruction then, stop here if (!curInstructionKnown) { allInstructionsKnown = false; fprintf(stderr, "mach_override: some instructions unknown! Need to update mach_override.c\n"); break; } // At this point, we've matched curInstr int eaten = curInstr->length; ptr += eaten; remainsToEat -= eaten; totalEaten += eaten; if (originalInstructionSizes) originalInstructionSizes[instructionIndex] = eaten; instructionIndex += 1; if (originalInstructionCount) *originalInstructionCount = instructionIndex; } if (howManyEaten) *howManyEaten = totalEaten; if (originalInstructions) { Boolean enoughSpaceForOriginalInstructions = (totalEaten < kOriginalInstructionsSize); if (enoughSpaceForOriginalInstructions) { memset(originalInstructions, 0x90 /* NOP */, kOriginalInstructionsSize); // fill instructions with NOP bcopy(code, originalInstructions, totalEaten); } else { #ifdef DEBUG_DISASM fprintf(stderr, "Not enough space in island to store original instructions. Adapt the island definition and kOriginalInstructionsSize\n"); #endif return false; } } if (allInstructionsKnown) { // save last 3 bytes of first 64bits of codre we'll replace uint64_t currentFirst64BitsOfCode = *((uint64_t *)code); currentFirst64BitsOfCode = OSSwapInt64(currentFirst64BitsOfCode); // back to memory representation currentFirst64BitsOfCode &= 0x0000000000FFFFFFLL; // keep only last 3 instructions bytes, first 5 will be replaced by JMP instr *newInstruction &= 0xFFFFFFFFFF000000LL; // clear last 3 bytes *newInstruction |= (currentFirst64BitsOfCode & 0x0000000000FFFFFFLL); // set last 3 bytes } return allInstructionsKnown; } static void fixupInstructions( void *originalFunction, void *escapeIsland, void *instructionsToFix, int instructionCount, uint8_t *instructionSizes ) { void *initialOriginalFunction = originalFunction; int index, fixed_size, code_size = 0; for (index = 0;index < instructionCount;index += 1) code_size += instructionSizes[index]; #ifdef DEBUG_DISASM void *initialInstructionsToFix = instructionsToFix; fprintf(stderr, "BEFORE FIXING:\n"); dump16Bytes(initialOriginalFunction); dump16Bytes(initialInstructionsToFix); #endif // DEBUG_DISASM for (index = 0;index < instructionCount;index += 1) { fixed_size = instructionSizes[index]; if ((*(uint8_t*)instructionsToFix == 0xE9) || // 32-bit jump relative (*(uint8_t*)instructionsToFix == 0xE8)) // 32-bit call relative { uint32_t offset = (uintptr_t)originalFunction - (uintptr_t)escapeIsland; uint32_t *jumpOffsetPtr = (uint32_t*)((uintptr_t)instructionsToFix + 1); *jumpOffsetPtr += offset; } if ((*(uint8_t*)instructionsToFix == 0x74) || // Near jump if equal (je), 2 bytes. (*(uint8_t*)instructionsToFix == 0x77)) // Near jump if above (ja), 2 bytes. { // We replace a near je/ja instruction, "7P JJ", with a 32-bit je/ja, "0F 8P WW XX YY ZZ". // This is critical, otherwise a near jump will likely fall outside the original function. uint32_t offset = (uintptr_t)initialOriginalFunction - (uintptr_t)escapeIsland; uint32_t jumpOffset = *(uint8_t*)((uintptr_t)instructionsToFix + 1); *(uint8_t*)(instructionsToFix + 1) = *(uint8_t*)instructionsToFix + 0x10; *(uint8_t*)instructionsToFix = 0x0F; uint32_t *jumpOffsetPtr = (uint32_t*)((uintptr_t)instructionsToFix + 2 ); *jumpOffsetPtr = offset + jumpOffset; fixed_size = 6; } originalFunction = (void*)((uintptr_t)originalFunction + instructionSizes[index]); escapeIsland = (void*)((uintptr_t)escapeIsland + instructionSizes[index]); instructionsToFix = (void*)((uintptr_t)instructionsToFix + fixed_size); // Expanding short instructions into longer ones may overwrite the next instructions, // so we must restore them. code_size -= fixed_size; if ((code_size > 0) && (fixed_size != instructionSizes[index])) { bcopy(originalFunction, instructionsToFix, code_size); } } #ifdef DEBUG_DISASM fprintf(stderr, "AFTER_FIXING:\n"); dump16Bytes(initialOriginalFunction); dump16Bytes(initialInstructionsToFix); #endif // DEBUG_DISASM } #ifdef DEBUG_DISASM #define HEX_DIGIT(x) ((((x) % 16) < 10) ? ('0' + ((x) % 16)) : ('A' + ((x) % 16 - 10))) static void dump16Bytes( void *ptr) { int i; char buf[3]; uint8_t *bytes = (uint8_t*)ptr; for (i = 0; i < 16; i++) { buf[0] = HEX_DIGIT(bytes[i] / 16); buf[1] = HEX_DIGIT(bytes[i] % 16); buf[2] = ' '; write(2, buf, 3); } write(2, "\n", 1); } #endif // DEBUG_DISASM #endif #if defined(__i386__) __asm( ".text;" ".align 2, 0x90;" "_atomic_mov64:;" " pushl %ebp;" " movl %esp, %ebp;" " pushl %esi;" " pushl %ebx;" " pushl %ecx;" " pushl %eax;" " pushl %edx;" // atomic push of value to an address // we use cmpxchg8b, which compares content of an address with // edx:eax. If they are equal, it atomically puts 64bit value // ecx:ebx in address. // We thus put contents of address in edx:eax to force ecx:ebx // in address " mov 8(%ebp), %esi;" // esi contains target address " mov 12(%ebp), %ebx;" " mov 16(%ebp), %ecx;" // ecx:ebx now contains value to put in target address " mov (%esi), %eax;" " mov 4(%esi), %edx;" // edx:eax now contains value currently contained in target address " lock; cmpxchg8b (%esi);" // atomic move. // restore registers " popl %edx;" " popl %eax;" " popl %ecx;" " popl %ebx;" " popl %esi;" " popl %ebp;" " ret" ); #elif defined(__x86_64__) void atomic_mov64( uint64_t *targetAddress, uint64_t value ) { *targetAddress = value; } #endif #endif #endif // __APPLE__