Re: [Libunwind-devel] ptrace-unwind not working at head

[Humberto Abdelnur]

Hello all,

> I looked at this some more. The unw_cursor_t keeps track of the 
> previous elf image mapped. Before mapping a new image, it unmaps the 
> previous image, so there is no leak.
>
> But in poc.c:
>
>     unw_init_remote(&orig_cursor, as, upt);
>     curr_cursor = orig_cursor;
>
> This assignment makes the cursor lose track of what was previously 
> mapped. I'll let David comment on if a separate API call is needed to 
> cleanup the cursor or the implementation could unmap the last mmap 
> when the end of call chain is reached.
I was just checking and there is no need to create a new API for it, 
actually the problems come with the function

src/ptrace/_UPT_destroy.c:_UPT_destroy

which frees the structure but it does not check whether the ei.image is 
NULL or not.
So, I modified the function to be as follow:

void
_UPT_destroy (void *arg)
{
 struct UPT_info *ui = arg;
 if (ui->ei.image)
   {
     munmap (ui->ei.image, ui->ei.size);
 }
 free (ui);

}


now, it works like a charm :)
I hope it helps, thank to all for the help.

Humberto