Getting a B::OP from an address?


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Getting a B::OP from an address?

by rockyb (Scribe)

on May 10, 2014 at 13:28 UTC ( #1085671=perlquestion: print w/replies, xml )

Need Help??

rockyb has asked for the wisdom of the Perl Monks concerning the following question:

In the debugger Devel::Trepan, there is the ability to show B:OP addresses. There is an optional plugin which allows one to disassemble Perl subroutines and packages. But what I'd like to do is to be able to disassemble a more limited region around the OP address. So how can I do that?

I know about Devel::Pointer, but I can't get that to work here:

(trepanpl): disasm Devel::Trepan::Options::whence_file
    ...    
    OP (0x9961848)
        op_next        0x9961828
        op_sibling    0
        op_ppaddr    PL_ppaddr[OP_PADSV]
        op_type        9
        op_flags    0000000
        op_private    0    
(trepanpl): sprintf "%d", 0x9961848
$DB::D[7] = 160831560
(trepanpl): $c = deref(160831560)
** Bizarre copy of UNKNOWN in scalar assignment
$DB::D[8] = <undef>

Program received signal SEGV.
Segmentation fault (core dumped)
[download]

Thoughts or suggestions?

Thanks.

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Re: Getting a B::OP from an address
by roboticus (Chancellor) on May 10, 2014 at 13:52 UTC

rockyb:

The deref function of Devel::Pointer is for handling perl values, not random chunks of memory. And an opcode isn't a standard perl value. I think you'll probably be better served digging through the B::* modules. If it were me, I'd start with B::Utils from which you can navigate the opcode tree(s) in a program.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

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