GDB (GNU Debugger) is a powerful tool for debugging programs on the x86 architecture. It allows developers to trace through code, set breakpoints, and examine variables and memory to find and fix bugs. However, what happens when you need to use GDB on a program that does not have debugging symbols? In this article, we will explore the usage of GDB on x86 without debugging symbols and how it can still be a valuable tool for debugging.
Debugging symbols, also known as debug information or symbols, are pieces of data that contain information about the source code and its structure. They are added to a program during the compilation process and are used by debuggers like GDB to map machine code back to the original source code. Without these symbols, GDB is unable to provide meaningful information about the program, making debugging a bit more challenging. However, there are still ways to use GDB effectively even without debugging symbols.
The first step in using GDB on a program without debugging symbols is to compile the program with the -g option. This will add debugging symbols to the executable, making it easier for GDB to work with. If you do not have access to the source code, you can also use the objcopy command to extract the debugging symbols from the program and create a separate file. This file can then be used by GDB to debug the program.
Once you have the program compiled with debugging symbols or have extracted them using objcopy, you can start GDB as usual. However, you will notice that when you try to set a breakpoint, GDB will not be able to find the function or line of code you specified. This is because without debugging symbols, GDB does not know the address of the function or line of code. To get around this, you can use the disassemble command to disassemble the program and find the address of the function or line of code you want to set a breakpoint on.
Another challenge when using GDB without debugging symbols is examining variables and memory. Without symbols, GDB does not know the names of the variables, making it difficult to view their values. To tackle this, you can use the x command to print out the contents of the memory at a specific address. You can also use the info registers command to view the values of the CPU registers, which can be helpful in understanding the program's state.
In addition to these commands, there are also other techniques you can use to debug a program without debugging symbols. For example, you can use the stepi command to step through the program one instruction at a time, allowing you to see the effects of each instruction on the program's state. You can also use the finish command to continue execution until the current function returns, which can be useful for debugging functions without symbols.
In conclusion, while debugging symbols make the process of debugging with GDB much more straightforward, they are not always available. Thankfully, there are still ways to use GDB effectively on programs without debugging symbols. By compiling the program with the -g option or extracting the symbols using objcopy, using the disassemble command to find addresses, and using other helpful commands, developers can still use GDB to debug their programs on x86 architecture without symbols. So the next time you encounter a program without debugging symbols, don't fret, GDB is still a reliable tool to help you find and fix bugs.
