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Diffstat (limited to 'xpcom/build/mach_override.c')
| -rw-r--r-- | xpcom/build/mach_override.c | 789 |
1 files changed, 789 insertions, 0 deletions
diff --git a/xpcom/build/mach_override.c b/xpcom/build/mach_override.c new file mode 100644 index 000000000..9e4940d29 --- /dev/null +++ b/xpcom/build/mach_override.c @@ -0,0 +1,789 @@ +// Copied from upstream at revision 195c13743fe0ebc658714e2a9567d86529f20443. +// mach_override.c semver:1.2.0 +// Copyright (c) 2003-2012 Jonathan 'Wolf' Rentzsch: http://rentzsch.com +// Some rights reserved: http://opensource.org/licenses/mit +// https://github.com/rentzsch/mach_override + +#include "mach_override.h" + +#include <mach-o/dyld.h> +#include <mach/mach_host.h> +#include <mach/mach_init.h> +#include <mach/vm_map.h> +#include <sys/mman.h> + +#include <CoreServices/CoreServices.h> + +/************************** +* +* Constants +* +**************************/ +#pragma mark - +#pragma mark (Constants) + +#define kPageSize 4096 +#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 +// On X86 we migh need to instert an add with a 32 bit immediate after the +// original instructions. +#define kMaxFixupSizeIncrease 5 + +unsigned 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 +// On X86-64 we never need to instert a new instruction. +#define kMaxFixupSizeIncrease 0 + +#define kJumpAddress kOriginalInstructionsSize + 6 + +unsigned 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 + +/************************** +* +* Data Types +* +**************************/ +#pragma mark - +#pragma mark (Data Types) + +typedef struct { + char instructions[sizeof(kIslandTemplate)]; +} BranchIsland; + +/************************** +* +* Funky Protos +* +**************************/ +#pragma mark - +#pragma mark (Funky Protos) + +static mach_error_t +allocateBranchIsland( + BranchIsland **island, + void *originalFunctionAddress); + + mach_error_t +freeBranchIsland( + BranchIsland *island ); + +#if defined(__ppc__) || defined(__POWERPC__) + mach_error_t +setBranchIslandTarget( + BranchIsland *island, + const void *branchTo, + long instruction ); +#endif + +#if defined(__i386__) || defined(__x86_64__) +mach_error_t +setBranchIslandTarget_i386( + BranchIsland *island, + const void *branchTo, + char* instructions ); +void +atomic_mov64( + uint64_t *targetAddress, + uint64_t value ); + + static Boolean +eatKnownInstructions( + unsigned char *code, + uint64_t *newInstruction, + int *howManyEaten, + char *originalInstructions, + int *originalInstructionCount, + uint8_t *originalInstructionSizes ); + + static void +fixupInstructions( + uint32_t offset, + void *instructionsToFix, + int instructionCount, + uint8_t *instructionSizes ); +#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; + uintptr_t page = (uintptr_t)address & ~(uintptr_t)(kPageSize-1); + int e = err_none; + e |= mprotect((void *)page, kPageSize, PROT_EXEC | PROT_READ | PROT_WRITE); + e |= msync((void *)page, kPageSize, MS_INVALIDATE ); + if (e) { + err = err_cannot_override; + } + return err; +} +#endif + + mach_error_t +mach_override_ptr( + void *originalFunctionAddress, + const void *overrideFunctionAddress, + void **originalFunctionReentryIsland ) +{ + 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 + + 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 ); + if (eatenCount + kMaxFixupSizeIncrease > kOriginalInstructionsSize) { + //printf ("Too many instructions eaten\n"); + 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 = allocateBranchIsland( &escapeIsland, 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 = allocateBranchIsland( &reentryIsland, 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 ) { + uint32_t offset = (uintptr_t)originalFunctionPtr - (uintptr_t)reentryIsland; + fixupInstructions(offset, 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 ) + freeBranchIsland( reentryIsland ); + if( escapeIsland ) + freeBranchIsland( escapeIsland ); + } + + return err; +} + +/******************************************************************************* +* +* Implementation +* +*******************************************************************************/ +#pragma mark - +#pragma mark (Implementation) + +static bool jump_in_range(intptr_t from, intptr_t to) { + intptr_t field_value = to - from - 5; + int32_t field_value_32 = field_value; + return field_value == field_value_32; +} + +/******************************************************************************* + Implementation: Allocates memory for a branch island. + + @param island <- The allocated island. + @result <- mach_error_t + + ***************************************************************************/ + +static mach_error_t +allocateBranchIslandAux( + BranchIsland **island, + void *originalFunctionAddress, + bool forward) +{ + assert( island ); + assert( sizeof( BranchIsland ) <= kPageSize ); + + vm_map_t task_self = mach_task_self(); + vm_address_t original_address = (vm_address_t) originalFunctionAddress; + vm_address_t address = original_address; + + for (;;) { + vm_size_t vmsize = 0; + memory_object_name_t object = 0; + kern_return_t kr = 0; + vm_region_flavor_t flavor = VM_REGION_BASIC_INFO; + // Find the region the address is in. +#if __WORDSIZE == 32 + vm_region_basic_info_data_t info; + mach_msg_type_number_t info_count = VM_REGION_BASIC_INFO_COUNT; + kr = vm_region(task_self, &address, &vmsize, flavor, + (vm_region_info_t)&info, &info_count, &object); +#else + vm_region_basic_info_data_64_t info; + mach_msg_type_number_t info_count = VM_REGION_BASIC_INFO_COUNT_64; + kr = vm_region_64(task_self, &address, &vmsize, flavor, + (vm_region_info_t)&info, &info_count, &object); +#endif + if (kr != KERN_SUCCESS) + return kr; + assert((address & (kPageSize - 1)) == 0); + + // Go to the first page before or after this region + vm_address_t new_address = forward ? address + vmsize : address - kPageSize; +#if __WORDSIZE == 64 + if(!jump_in_range(original_address, new_address)) + break; +#endif + address = new_address; + + // Try to allocate this page. + kr = vm_allocate(task_self, &address, kPageSize, 0); + if (kr == KERN_SUCCESS) { + *island = (BranchIsland*) address; + return err_none; + } + if (kr != KERN_NO_SPACE) + return kr; + } + + return KERN_NO_SPACE; +} + +static mach_error_t +allocateBranchIsland( + BranchIsland **island, + void *originalFunctionAddress) +{ + mach_error_t err = + allocateBranchIslandAux(island, originalFunctionAddress, true); + if (!err) + return err; + return allocateBranchIslandAux(island, originalFunctionAddress, false); +} + + +/******************************************************************************* + 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( sizeof( BranchIsland ) <= kPageSize ); + return vm_deallocate( mach_task_self(), (vm_address_t) island, + kPageSize ); +} + +/******************************************************************************* + 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 %ebp; mov %esp,%ebp; leave; ret + { 0x1, {0xFF}, {0x90} }, // nop + { 0x1, {0xFF}, {0x55} }, // push %esp + { 0x2, {0xFF, 0xFF}, {0x89, 0xE5} }, // mov %esp,%ebp + { 0x1, {0xFF}, {0x53} }, // push %ebx + { 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 + { 0x1, {0xFF}, {0x57} }, // push %edi + { 0x1, {0xFF}, {0x56} }, // push %esi + { 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 + { 0x4, {0xFF, 0xFF, 0xFF, 0x00}, {0x8B, 0x4C, 0x24, 0x00} }, // mov $imm(%esp), %ecx + { 0x5, {0xFF, 0x00, 0x00, 0x00, 0x00}, {0xB8, 0x00, 0x00, 0x00, 0x00} }, // mov $imm, %eax + { 0x6, {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}, {0xE8, 0x00, 0x00, 0x00, 0x00, 0x58} }, // call $imm; pop %eax + { 0x0 } +}; +#elif defined(__x86_64__) +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 + { 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, 0x00, 0x00}, {0x48, 0x89, 0x00, 0x00} }, // move onto rbp + { 0x4, {0xFF, 0xFF, 0xFF, 0xFF}, {0x40, 0x0f, 0xbe, 0xce} }, // movsbl %sil, %ecx + { 0x2, {0xFF, 0x00}, {0x41, 0x00} }, // push %rXX + { 0x2, {0xFF, 0x00}, {0x85, 0x00} }, // test %rX,%rX + { 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 + { 0x2, {0xFF, 0xFF}, {0x89, 0xF8} }, // mov %edi, %eax + + //leaq offset(%rip),%rax + { 0x7, {0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00}, {0x48, 0x8d, 0x05, 0x00, 0x00, 0x00, 0x00} }, + + { 0x0 } +}; +#endif + +static Boolean codeMatchesInstruction(unsigned char *code, AsmInstructionMatch* instruction) +{ + Boolean match = true; + + size_t i; + for (i=0; i<instruction->length; i++) { + unsigned char mask = instruction->mask[i]; + unsigned char constraint = instruction->constraint[i]; + unsigned char codeValue = code[i]; + + match = ((codeValue & mask) == constraint); + if (!match) break; + } + + 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 { + // printf ("Not enough space in island to store original instructions. Adapt the island definition and kOriginalInstructionsSize\n"); + 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( + uint32_t offset, + void *instructionsToFix, + int instructionCount, + uint8_t *instructionSizes ) +{ + // The start of "leaq offset(%rip),%rax" + static const uint8_t LeaqHeader[] = {0x48, 0x8d, 0x05}; + + int index; + for (index = 0;index < instructionCount;index += 1) + { + if (*(uint8_t*)instructionsToFix == 0xE9) // 32-bit jump relative + { + uint32_t *jumpOffsetPtr = (uint32_t*)((uintptr_t)instructionsToFix + 1); + *jumpOffsetPtr += offset; + } + + // leaq offset(%rip),%rax + if (memcmp(instructionsToFix, LeaqHeader, 3) == 0) { + uint32_t *LeaqOffsetPtr = (uint32_t*)((uintptr_t)instructionsToFix + 3); + *LeaqOffsetPtr += offset; + } + + // 32-bit call relative to the next addr; pop %eax + if (*(uint8_t*)instructionsToFix == 0xE8) + { + // Just this call is larger than the jump we use, so we + // know this is the last instruction. + assert(index == (instructionCount - 1)); + assert(instructionSizes[index] == 6); + + // Insert "addl $offset, %eax" in the end so that when + // we jump to the rest of the function %eax has the + // value it would have if eip had been pushed by the + // call in its original position. + uint8_t *op = instructionsToFix; + op += 6; + *op = 0x05; // addl + uint32_t *addImmPtr = (uint32_t*)(op + 1); + *addImmPtr = offset; + } + + instructionsToFix = (void*)((uintptr_t)instructionsToFix + instructionSizes[index]); + } +} +#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 |