How to set a breakpoint when a method is called using LLDB on OS X?

Question

I'm trying to hit a breakpoint that I set in LLDB (CLI), but for whatever reason I'm not hitting my breakpoint. I am messing around with the stock Calculator.app on OS X, and am trying to call / hit my breakpoint when I open the About dialog box of the Calculator.app.

I launch the Calculator.app, then I start lldb from a Terminal window. I find the process of the Calculator.app using ps and grep. I attach to the running process using LLDB. I then issue the continue command in LLDB to allow the Calculator.app to continue running.

Then I set a breakpoint in LLDB when the following method is called, showAbout

I type the following command into LLDB, (lldb) breakpoint set --method showAbout

However when I click About Calculator from the menu bar it doesn't halt the program, but rather shows the About dialog box for the Calculator.

Answer 1

The Calculator app is stripped as can be seen by running nm. You will need to find the address of the method using class-dump:

$ class-dump -A /Applications/Calculator.app | grep showAbout
- (void)showAbout:(id)arg1; // IMP=0x0000000100009939

However as the Calculator application is already running, the address has been slided because of ASLR. To find the ASLR slide you can use my tool called get_aslr, like so:

$ sudo get_aslr $(pgrep Calculator)
ASLR slide: 0x9508000

You then add the two numbers together:

0x0000000100009939 + 0x9508000 = 0x109511939

That is the current address of the showAbout: method. Now you just need to set the breakpoint in lldb:

b *0x109511939

And it works!