[PATCH] Add -bare option to llvm-objdump

[Kevin Enderby]

On Sep 11, 2014, at 12:11 AM, Steve King <steve at metrokings.com> wrote:

> On Wed, Sep 10, 2014 at 8:29 PM, Sean Silva <chisophugis at gmail.com> wrote:
>> 
>> Right, you mean like otool's -d (" Display the contents of the
>> (__DATA,__data) section") or -t ("Display  the contents of the
>> (__TEXT,__text) section.  With the -v flag, this disassembles the text.")?
>> ;)
>> 
> 
> I've never used otools, but presumably Kevin has some idea here.

I’ll try to explain my ideas.  I think what we are talking about is how detailed the disassembly is, that is not printing just the raw bytes of a section and no disassembly.  That is we are not talking about otool(1)’s printing of the text section without the -v flag.

Disassembly for otool(1) requires -v to get the disassembly of sections with instructions in them.  In this mode (without -V) it will disassembly the instructions but will not try to symbolicate the operands.  For example:

% otool -tv hello.o
…
0000000000000026	callq	0x2b

With -V then it will attempt to symbolicate the operands (using all the information it has, relocation entries, symbol tables, etc):

% otool -tV hello.o
…
0000000000000026	callq	_printf

my goal is by default this:

% llvm-objdump -m -d hello.o

will do the same as otool(1)’s -tV and produce the best disassembly (or maybe even better).

But I do want have the option of getting just the disassembly without symbolicating operands.  So I’m thinking that these would would produce the same results:

% llvm-objdump -m -d hello.o -bare
% otool -tv hello.o

with both producing disassembly but not symbolicating operands.  But I’m open to other ways to get this functionality.  One note if your carefully reading non-symbolic operand to the callq instruction above, I want to see the the target address, in this case 0x2b, not the displacement.

> 
>> What is your goal?
> 
> A symbolizing disassembler with at least the possibility to tune
> output to match existing norms per host platform.
> 
> 
>> From what I can gather, it seems like you just want to
>> make llvm-objdump's default behavior match GNU objdump, which doesn't seem
>> like a very good direction (how deep is the rabbit hole? why GNU objdump and
>> not tool or the windows one?).
> 
> What I personally need is a just symbolizing disassembler.  What my
> colleagues will expect is a fair approximation of GNU objdump because
> that's what they already know.  Kevin piped up early that he wanted
> otools style output, so we ended up at the goal above.

Yep my goal would be the best symbolic disassembly by default.  With switches to turn off the symbolic operands for test cases or the power user who is likely the guy hunting down bugs and needs to see the operands raw.  Basically it would be nice to have a less verbose option for those that need these things.

For example, the code I added for the Mach-O printing of private headers has a boolean verbose and will do this today.  The call right now is passing in true for verbose but if there was a -bare or some other option I’d wire it up to that parameter.  I don’t really care what we call it and I can live with what ever develops over time.  If nothing does I’ll eventually create a Mach-O specific option to wire this up.

My thoughts,
Kev
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20140911/75a95dbf/attachment.html>