CODEWITHSUNDEEP
cobjective-cxcodemacosassembly
somethingunderscore
somethingunderscore

Reputation: 101

Illegal instruction (ud2) when running application with Xcode as root on macOS

I'm trying to run my application as root with Xcode on macOS, but I keep getting this bizarre error..

Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

It's literally just a hello world. All I've added was a printf to the default Obj-C application, tried running it as root, aaaand it ends up on a ud2 instruction somehow. I've tried running Xcode with sudo, editing the scheme, the combination of the two, and nothing works. It seems like just the thought of root shudders causes Xcode to insert some undefined instruction and crash.

edit: I'm on macOS Catalina 10.15.3 and Xcode 11.4, which I just downloaded yesterday, and this is the code I'm trying to run:

#import <Cocoa/Cocoa.h>

int main(int argc, const char * argv[]) {
    printf("Hello world\n");
    @autoreleasepool {
        // Setup code that might create autoreleased objects goes here.
    }
    return NSApplicationMain(argc, argv);
}

'My code' doesn't actually do anything. Removing the printf still causes the ud2 instruction crash, so the actual boilerplate developed by Apple doesn't work when run as root..

Upvotes: 2

Views: 1116

Answers (1)

jvarela
jvarela

Reputation: 3847

I tried your project I downloaded from the GitHub link you provided and I can tell you I'm able to reproduce the bug you reported. Apparently, there is some incompatibility between libsystem_secinit initialization code and when you turn on the entitlement App Sandbox to YES. If you turn it off, the crash goes away.

That reminds me of a bug described by Eskimo, who is a really helpful Apple engineer. He described also some incompatibilities between entitlements and libsystem_secinit.

I would definitely recommend that you file a bug against this incompatibility with Feedback Assistant. At least, Apple's boiler plate code should work without crashing.

Upvotes: 5

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