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765 lines
24 KiB
765 lines
24 KiB
// mach_override.c semver:1.2.0
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// Copyright (c) 2003-2012 Jonathan 'Wolf' Rentzsch: http://rentzsch.com
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// Some rights reserved: http://opensource.org/licenses/mit
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// https://github.com/rentzsch/mach_override
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#include "mach_override.h"
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#include <mach-o/dyld.h>
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#include <mach/mach_host.h>
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#include <mach/mach_init.h>
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#include <mach/vm_map.h>
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#include <sys/mman.h>
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#include <libkern/OSAtomic.h>
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#include <CoreServices/CoreServices.h>
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/**************************
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*
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* Constants
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*
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**************************/
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#pragma mark -
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#pragma mark (Constants)
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#define kPageSize 4096
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#if defined(__ppc__) || defined(__POWERPC__)
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long kIslandTemplate[] = {
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0x9001FFFC, // stw r0,-4(SP)
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0x3C00DEAD, // lis r0,0xDEAD
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0x6000BEEF, // ori r0,r0,0xBEEF
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0x7C0903A6, // mtctr r0
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0x8001FFFC, // lwz r0,-4(SP)
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0x60000000, // nop ; optionally replaced
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0x4E800420 // bctr
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};
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#define kAddressHi 3
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#define kAddressLo 5
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#define kInstructionHi 10
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#define kInstructionLo 11
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#elif defined(__i386__)
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#define kOriginalInstructionsSize 16
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// On X86 we migh need to instert an add with a 32 bit immediate after the
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// original instructions.
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#define kMaxFixupSizeIncrease 5
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unsigned char kIslandTemplate[] = {
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// kOriginalInstructionsSize nop instructions so that we
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// should have enough space to host original instructions
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0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
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0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
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// Now the real jump instruction
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0xE9, 0xEF, 0xBE, 0xAD, 0xDE
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};
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#define kInstructions 0
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#define kJumpAddress kInstructions + kOriginalInstructionsSize + 1
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#elif defined(__x86_64__)
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#define kOriginalInstructionsSize 32
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// On X86-64 we never need to instert a new instruction.
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#define kMaxFixupSizeIncrease 0
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#define kJumpAddress kOriginalInstructionsSize + 6
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unsigned char kIslandTemplate[] = {
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// kOriginalInstructionsSize nop instructions so that we
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// should have enough space to host original instructions
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0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
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0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
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0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
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0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90,
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// Now the real jump instruction
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0xFF, 0x25, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00
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};
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#endif
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/**************************
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*
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* Data Types
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*
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**************************/
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#pragma mark -
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#pragma mark (Data Types)
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typedef struct {
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char instructions[sizeof(kIslandTemplate)];
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} BranchIsland;
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/**************************
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*
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* Funky Protos
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*
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**************************/
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#pragma mark -
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#pragma mark (Funky Protos)
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static mach_error_t
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allocateBranchIsland(
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BranchIsland **island,
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void *originalFunctionAddress);
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mach_error_t
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freeBranchIsland(
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BranchIsland *island );
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#if defined(__ppc__) || defined(__POWERPC__)
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mach_error_t
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setBranchIslandTarget(
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BranchIsland *island,
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const void *branchTo,
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long instruction );
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#endif
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#if defined(__i386__) || defined(__x86_64__)
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mach_error_t
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setBranchIslandTarget_i386(
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BranchIsland *island,
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const void *branchTo,
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char* instructions );
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void
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atomic_mov64(
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uint64_t *targetAddress,
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uint64_t value );
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static Boolean
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eatKnownInstructions(
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unsigned char *code,
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uint64_t *newInstruction,
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int *howManyEaten,
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char *originalInstructions,
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int *originalInstructionCount,
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uint8_t *originalInstructionSizes );
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static void
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fixupInstructions(
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uint32_t offset,
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void *instructionsToFix,
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int instructionCount,
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uint8_t *instructionSizes );
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#endif
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/*******************************************************************************
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*
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* Interface
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*
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*******************************************************************************/
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#pragma mark -
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#pragma mark (Interface)
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#if defined(__i386__) || defined(__x86_64__)
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mach_error_t makeIslandExecutable(void *address) {
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mach_error_t err = err_none;
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uintptr_t page = (uintptr_t)address & ~(uintptr_t)(kPageSize-1);
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int e = err_none;
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e |= mprotect((void *)page, kPageSize, PROT_EXEC | PROT_READ | PROT_WRITE);
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e |= msync((void *)page, kPageSize, MS_INVALIDATE );
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if (e) {
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err = err_cannot_override;
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}
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return err;
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}
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#endif
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mach_error_t
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mach_override_ptr(
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void *originalFunctionAddress,
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const void *overrideFunctionAddress,
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void **originalFunctionReentryIsland )
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{
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assert( originalFunctionAddress );
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assert( overrideFunctionAddress );
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// this addresses overriding such functions as AudioOutputUnitStart()
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// test with modified DefaultOutputUnit project
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#if defined(__x86_64__)
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for(;;){
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if(*(uint16_t*)originalFunctionAddress==0x25FF) // jmp qword near [rip+0x????????]
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originalFunctionAddress=*(void**)((char*)originalFunctionAddress+6+*(int32_t *)((uint16_t*)originalFunctionAddress+1));
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else break;
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}
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#elif defined(__i386__)
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for(;;){
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if(*(uint16_t*)originalFunctionAddress==0x25FF) // jmp *0x????????
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originalFunctionAddress=**(void***)((uint16_t*)originalFunctionAddress+1);
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else break;
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}
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#endif
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long *originalFunctionPtr = (long*) originalFunctionAddress;
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mach_error_t err = err_none;
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#if defined(__ppc__) || defined(__POWERPC__)
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// Ensure first instruction isn't 'mfctr'.
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#define kMFCTRMask 0xfc1fffff
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#define kMFCTRInstruction 0x7c0903a6
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long originalInstruction = *originalFunctionPtr;
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if( !err && ((originalInstruction & kMFCTRMask) == kMFCTRInstruction) )
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err = err_cannot_override;
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#elif defined(__i386__) || defined(__x86_64__)
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int eatenCount = 0;
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int originalInstructionCount = 0;
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char originalInstructions[kOriginalInstructionsSize];
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uint8_t originalInstructionSizes[kOriginalInstructionsSize];
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uint64_t jumpRelativeInstruction = 0; // JMP
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Boolean overridePossible = eatKnownInstructions ((unsigned char *)originalFunctionPtr,
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&jumpRelativeInstruction, &eatenCount,
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originalInstructions, &originalInstructionCount,
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originalInstructionSizes );
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if (eatenCount + kMaxFixupSizeIncrease > kOriginalInstructionsSize) {
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//printf ("Too many instructions eaten\n");
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overridePossible = false;
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}
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if (!overridePossible) err = err_cannot_override;
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if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
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#endif
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// Make the original function implementation writable.
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if( !err ) {
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err = vm_protect( mach_task_self(),
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(vm_address_t) originalFunctionPtr, 8, false,
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(VM_PROT_ALL | VM_PROT_COPY) );
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if( err )
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err = vm_protect( mach_task_self(),
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(vm_address_t) originalFunctionPtr, 8, false,
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(VM_PROT_DEFAULT | VM_PROT_COPY) );
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}
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if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
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// Allocate and target the escape island to the overriding function.
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BranchIsland *escapeIsland = NULL;
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if( !err )
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err = allocateBranchIsland( &escapeIsland, originalFunctionAddress );
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if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
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#if defined(__ppc__) || defined(__POWERPC__)
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if( !err )
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err = setBranchIslandTarget( escapeIsland, overrideFunctionAddress, 0 );
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// Build the branch absolute instruction to the escape island.
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long branchAbsoluteInstruction = 0; // Set to 0 just to silence warning.
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if( !err ) {
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long escapeIslandAddress = ((long) escapeIsland) & 0x3FFFFFF;
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branchAbsoluteInstruction = 0x48000002 | escapeIslandAddress;
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}
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#elif defined(__i386__) || defined(__x86_64__)
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if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
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if( !err )
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err = setBranchIslandTarget_i386( escapeIsland, overrideFunctionAddress, 0 );
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if (err) fprintf(stderr, "err = %x %s:%d\n", err, __FILE__, __LINE__);
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// Build the jump relative instruction to the escape island
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#endif
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#if defined(__i386__) || defined(__x86_64__)
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if (!err) {
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uint32_t addressOffset = ((char*)escapeIsland - (char*)originalFunctionPtr - 5);
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addressOffset = OSSwapInt32(addressOffset);
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jumpRelativeInstruction |= 0xE900000000000000LL;
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jumpRelativeInstruction |= ((uint64_t)addressOffset & 0xffffffff) << 24;
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jumpRelativeInstruction = OSSwapInt64(jumpRelativeInstruction);
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}
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#endif
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// Optionally allocate & return the reentry island. This may contain relocated
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// jmp instructions and so has all the same addressing reachability requirements
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// the escape island has to the original function, except the escape island is
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// technically our original function.
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BranchIsland *reentryIsland = NULL;
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if( !err && originalFunctionReentryIsland ) {
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err = allocateBranchIsland( &reentryIsland, escapeIsland);
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if( !err )
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*originalFunctionReentryIsland = reentryIsland;
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}
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#if defined(__ppc__) || defined(__POWERPC__)
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// Atomically:
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// o If the reentry island was allocated:
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// o Insert the original instruction into the reentry island.
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// o Target the reentry island at the 2nd instruction of the
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// original function.
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// o Replace the original instruction with the branch absolute.
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if( !err ) {
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int escapeIslandEngaged = false;
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do {
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if( reentryIsland )
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err = setBranchIslandTarget( reentryIsland,
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(void*) (originalFunctionPtr+1), originalInstruction );
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if( !err ) {
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escapeIslandEngaged = CompareAndSwap( originalInstruction,
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branchAbsoluteInstruction,
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(UInt32*)originalFunctionPtr );
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if( !escapeIslandEngaged ) {
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// Someone replaced the instruction out from under us,
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// re-read the instruction, make sure it's still not
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// 'mfctr' and try again.
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originalInstruction = *originalFunctionPtr;
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if( (originalInstruction & kMFCTRMask) == kMFCTRInstruction)
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err = err_cannot_override;
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}
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}
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} while( !err && !escapeIslandEngaged );
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}
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#elif defined(__i386__) || defined(__x86_64__)
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// Atomically:
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// o If the reentry island was allocated:
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// o Insert the original instructions into the reentry island.
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// o Target the reentry island at the first non-replaced
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// instruction of the original function.
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// o Replace the original first instructions with the jump relative.
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//
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// Note that on i386, we do not support someone else changing the code under our feet
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if ( !err ) {
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uint32_t offset = (uintptr_t)originalFunctionPtr - (uintptr_t)reentryIsland;
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fixupInstructions(offset, originalInstructions,
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originalInstructionCount, originalInstructionSizes );
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if( reentryIsland )
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err = setBranchIslandTarget_i386( reentryIsland,
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(void*) ((char *)originalFunctionPtr+eatenCount), originalInstructions );
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// try making islands executable before planting the jmp
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#if defined(__x86_64__) || defined(__i386__)
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if( !err )
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err = makeIslandExecutable(escapeIsland);
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if( !err && reentryIsland )
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err = makeIslandExecutable(reentryIsland);
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#endif
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if ( !err )
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atomic_mov64((uint64_t *)originalFunctionPtr, jumpRelativeInstruction);
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}
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#endif
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// Clean up on error.
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if( err ) {
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if( reentryIsland )
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freeBranchIsland( reentryIsland );
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if( escapeIsland )
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freeBranchIsland( escapeIsland );
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}
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return err;
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}
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/*******************************************************************************
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*
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* Implementation
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*
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*******************************************************************************/
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#pragma mark -
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#pragma mark (Implementation)
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static bool jump_in_range(intptr_t from, intptr_t to) {
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intptr_t field_value = to - from - 5;
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int32_t field_value_32 = field_value;
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return field_value == field_value_32;
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}
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/*******************************************************************************
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Implementation: Allocates memory for a branch island.
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@param island <- The allocated island.
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@result <- mach_error_t
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***************************************************************************/
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static mach_error_t
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allocateBranchIslandAux(
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BranchIsland **island,
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void *originalFunctionAddress,
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bool forward)
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{
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assert( island );
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assert( sizeof( BranchIsland ) <= kPageSize );
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vm_map_t task_self = mach_task_self();
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vm_address_t original_address = (vm_address_t) originalFunctionAddress;
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vm_address_t address = original_address;
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for (;;) {
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vm_size_t vmsize = 0;
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memory_object_name_t object = 0;
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kern_return_t kr = 0;
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vm_region_flavor_t flavor = VM_REGION_BASIC_INFO;
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// Find the region the address is in.
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#if __WORDSIZE == 32
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vm_region_basic_info_data_t info;
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mach_msg_type_number_t info_count = VM_REGION_BASIC_INFO_COUNT;
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kr = vm_region(task_self, &address, &vmsize, flavor,
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(vm_region_info_t)&info, &info_count, &object);
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#else
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vm_region_basic_info_data_64_t info;
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mach_msg_type_number_t info_count = VM_REGION_BASIC_INFO_COUNT_64;
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kr = vm_region_64(task_self, &address, &vmsize, flavor,
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(vm_region_info_t)&info, &info_count, &object);
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#endif
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if (kr != KERN_SUCCESS)
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return kr;
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assert((address & (kPageSize - 1)) == 0);
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// Go to the first page before or after this region
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vm_address_t new_address = forward ? address + vmsize : address - kPageSize;
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#if __WORDSIZE == 64
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if(!jump_in_range(original_address, new_address))
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break;
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#endif
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address = new_address;
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// Try to allocate this page.
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kr = vm_allocate(task_self, &address, kPageSize, 0);
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if (kr == KERN_SUCCESS) {
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*island = (BranchIsland*) address;
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return err_none;
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}
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if (kr != KERN_NO_SPACE)
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return kr;
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}
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return KERN_NO_SPACE;
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}
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static mach_error_t
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allocateBranchIsland(
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BranchIsland **island,
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void *originalFunctionAddress)
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{
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mach_error_t err =
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allocateBranchIslandAux(island, originalFunctionAddress, true);
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if (!err)
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return err;
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return allocateBranchIslandAux(island, originalFunctionAddress, false);
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}
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/*******************************************************************************
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Implementation: Deallocates memory for a branch island.
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@param island -> The island to deallocate.
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@result <- mach_error_t
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***************************************************************************/
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mach_error_t
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freeBranchIsland(
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BranchIsland *island )
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{
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assert( island );
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assert( (*(long*)&island->instructions[0]) == kIslandTemplate[0] );
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assert( sizeof( BranchIsland ) <= kPageSize );
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return vm_deallocate( mach_task_self(), (vm_address_t) island,
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kPageSize );
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}
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/*******************************************************************************
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Implementation: Sets the branch island's target, with an optional
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instruction.
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@param island -> The branch island to insert target into.
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@param branchTo -> The address of the target.
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@param instruction -> Optional instruction to execute prior to branch. Set
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to zero for nop.
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@result <- mach_error_t
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***************************************************************************/
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#if defined(__ppc__) || defined(__POWERPC__)
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mach_error_t
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setBranchIslandTarget(
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BranchIsland *island,
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const void *branchTo,
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long instruction )
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{
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// Copy over the template code.
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bcopy( kIslandTemplate, island->instructions, sizeof( kIslandTemplate ) );
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// Fill in the address.
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((short*)island->instructions)[kAddressLo] = ((long) branchTo) & 0x0000FFFF;
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((short*)island->instructions)[kAddressHi]
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= (((long) branchTo) >> 16) & 0x0000FFFF;
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// Fill in the (optional) instuction.
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if( instruction != 0 ) {
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((short*)island->instructions)[kInstructionLo]
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= instruction & 0x0000FFFF;
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((short*)island->instructions)[kInstructionHi]
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= (instruction >> 16) & 0x0000FFFF;
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}
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//MakeDataExecutable( island->instructions, sizeof( kIslandTemplate ) );
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msync( island->instructions, sizeof( kIslandTemplate ), MS_INVALIDATE );
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return err_none;
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}
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#endif
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#if defined(__i386__)
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mach_error_t
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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 = (uint8_t*)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__)
|
|
void atomic_mov64(
|
|
uint64_t *targetAddress,
|
|
uint64_t value)
|
|
{
|
|
while (true)
|
|
{
|
|
uint64_t old_value = *targetAddress;
|
|
if (OSAtomicCompareAndSwap64(old_value, value, (int64_t*)targetAddress)) return;
|
|
}
|
|
}
|
|
#elif defined(__x86_64__)
|
|
void atomic_mov64(
|
|
uint64_t *targetAddress,
|
|
uint64_t value )
|
|
{
|
|
*targetAddress = value;
|
|
}
|
|
#endif
|
|
#endif
|