Stack Trace: Difference between revisions

Note that the above code and GDB backtracing require a NULL %ebp, to know when to stop. Otherwise the traces will run off into garbage. To account for this, set up a NULL stack frame before you jump to your C entry point:

 

mov $stack_end, %esp ; Initialize %esp

...

xor %ebp, %ebp ; Set %ebp to NULL

call kmain ; According to calling convention, kmain will save %ebp (=NULL) to the stack

 

With this, stack tracers will see the NULL %ebp as the end of the trace.

This assembly implementation for x86 uses the same algorithm as above and similarly relies on a NULL base pointer to be placed near the top of the stack. Rather than print the contents of the stack, however, it builds an array of addresses which can then be resolved into symbol names.

 

; Walks backwards through the call stack and builds a list of return addresses.

; Args:

leave

ret

 

=== Resolving Function Names ===