如何强制 GDB 执行没有符号的代码

Question

I have a C program that (for good reason) allocates memory, copies some code to it, uses mprotect() to give it execute privileges, and then calls that code. Yes I know this is unportable and unsafe, but there's a good reason. Anyway, I need to single-step with gdb through the assembly code (using si command) but it won't let me -- it keeps saying: "No function contains program counter for selected frame"

Is there a way to force gdb to execute this code? Is there another debugger that I should be using instead for this type of thing?

Thanks!

Answer 1

Seems like you want the add-symbol-file', or add-symbol-file-from-memory' commands to let gdb know about the code that has been copied to that memory location.

Answer 2

You should be able to follow through your code by using display/i $pc before starting to si / stepi . This tells it to show the disassembly of the current instruction just before printing the prompt each time.

Answer 3

The stepi command itself doesn't require any symbols and should work just fine in the scenario you described (though I haven't actually checked whether it does).

Is your problem really with stepi ? Showing relevant part(s) of your debug session might open your question to better answers.