Illegal instruction: 4

Some old arm v6 binaries that compiled using iPhone-gcc and old sdk have "Illegal instruction: 4" when using devices with A6/A6X CPU such as iPhone 5 / iPad 4 as discussed in http://code.google.com/p/iphone-gcc-full/issues/detail?id=6
The is how to patch these binaries without recompiling or when source code is not available

perl -pe 's/\x{00}\x{30}\x{93}\x{e4}/\x{00}\x{30}\x{93}\x{e5}/g;s/\x{00}\x{30}\x{d3}\x{e4}/\x{00}\x{30}\x{d3}\x{e5}/g;' < old_ios_binary > old_ios_binary_patched
chmod +x old_ios_binary_patched
ldid -s old_ios_binary_patched
mv old_ios_binary old_ios_binary_original
mv old_ios_binary_patched old_ios_binary


If you have gnu sed in iOS or OS X, you can patch directly without the temp file in one step
sed -i'' 's/\x00\x30\x93\xe4/\x00\x30\x93\xe5/g;s/\x00\x30\xd3\xe4/\x00\x30\xd3\xe5/g;' old_ios_binary
ldid -s old_ios_binary


iphone-gcc patched package for iPhone 5 / iPad 4 is here
http://code.google.com/p/apiexplorer/downloads/list

swizzleMethodsForClass

swizzleMethodsForClass.m Select all

#import <objc/runtime.h> // swap a class's instance method selectors, we do this to overload existing methods in category declarations void swizzleMethodsForClass(Class c, SEL origMethodSel, SEL newMethodSel) { NSLog(@"swizzling %@ instance methods: %@ -> %@", NSStringFromClass(c), NSStringFromSelector(origMethodSel), NSStringFromSelector(newMethodSel)); Method origMethod = class_getInstanceMethod(c, origMethodSel); Method newMethod = class_getInstanceMethod(c, newMethodSel); // check if method is inherited from superclass if(class_addMethod(c, origMethodSel, method_getImplementation(newMethod), method_getTypeEncoding(newMethod))) class_replaceMethod(c, newMethodSel, method_getImplementation(origMethod), method_getTypeEncoding(origMethod)); // exchange un-subclassed method else method_exchangeImplementations(origMethod, newMethod); } @interface UIDevice (SpoofUDID) @end #define UDID_TO_SPOOF @"e0101010d38bde8e6740011211af315301010223" @implementation UIDevice (SpoofUDID) // swizzle this instance method for UIDevice class - (NSString *) spoofUniqueIdentifier { static NSString *spoofUDID = UDID_TO_SPOOF; NSLog(@"spoofing %@ instead of %@", spoofUDID, [[UIDevice currentDevice] spoofUniqueIdentifier]); return spoofUDID; } @end // call this from your app delegate - (void) initUDID { NSString *UDID = [[UIDevice currentDevice] uniqueIdentifier]; NSLog(@"this is my old udid: %@", UDID); swizzleMethodsForClass([UIDevice class], @selector(uniqueIdentifier), @selector(spoofUniqueIdentifier)); NSString *UDID2 = [[UIDevice currentDevice] uniqueIdentifier]; NSLog(@"this is my new udid: %@", UDID2); }