Stack Trace: Difference between revisions
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→Walking the stack: Add instructions for NULL stack frame |
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}
</source>
Note that the above code requires a NULL return address, and GDB backtracing requires 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:
<source lang="asm">
mov $stack_end, %esp ; Initialize %esp
...
xor %ebp, %ebp ; Set %ebp to NULL
push %ebp ; Push a NULL return address to the stack
jmp kmain ; According to calling convention, kmain will save %ebp (=NULL) to the stack
</source>
With this, stack tracers will see the NULL %ebp and/or return address as the end of the trace. You can use call in place of push/jmp, but your tracer will need to check for a NULL %ebp, rather than a NULL return address.
=== Resolving Function Names ===
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