From: Zhao Shujing <pearly.zhao@oracle.com>
To: Andrew Cagney <cagney@redhat.com>
Cc: frysk@sourceware.org
Subject: Re: [patch] disassembly window
Date: Wed, 22 Aug 2007 09:14:00 -0000 [thread overview]
Message-ID: <1187774326.4163.16.camel@linux-pzhao.site> (raw)
In-Reply-To: <46C997F2.1060206@redhat.com>
Hi, Andrew
Thanks for the explanation of disassemble backwards.
If the symbol isn't available, gdb's disassemble command would return
"No function contains specified address". Would frysk's disassemble
command disassemble a small range from the frame's PC, not just return
some warning sentence?
Thanks
Pearly
On Mon, 2007-08-20 at 09:32 -0400, Andrew Cagney wrote:
> Zhao Shujing wrote:
> > Hi
> >
> > This patch is to fix bug #4932 and other bugs of disassembly window.
> > rowPrepend is added to prepend rows by calculating memory information
> > like rowAppend. Because the methods that are provided by class
> > Disassembler, disassembleInstructions and
> > disassembleInstructionsStartEnd, can only read the instructions that are
> > following some address, rowPrepend have to use two while execution
> > control to read the instructions that are preceding some address.
> > Any suggestions are welcomed.
> >
>
> Pearly, nice work.
>
> The challenge here, and the reason why the disassembler only goes
> forward from PC is that, in general, it isn't possible to disassemble
> backwards. This is because architectures such as the i386 and x86-64
> have variable length instructions making it effectively impossible to
> figure out where, looking backwards, an instruction starts. For
> instance, looking backwards is that a one byte int80 instruction, or a
> multi-byte instruction loading the hex code for int80?
>
> For disassembling a range, can I suggest doing something similar to the
> disassembler command in frysk.hpd.DisassemblerCommand. That code first
> attempts to fetch the frysk.symtab.Symbol at the frame's
> adjusted-address and then uses its address/size to determine the start
> address and size to disassemble. If the symbol isn't available, then
> I'd just disassemble a small range from the frame's PC.
>
> One heads up for you; you may want to consider configuring your personal
> build with --with-libopcodes.
>
> Andrew
>
next prev parent reply other threads:[~2007-08-22 9:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-17 8:47 Zhao Shujing
2007-08-20 9:07 ` Zhao Shujing
2007-08-20 13:32 ` Andrew Cagney
2007-08-22 9:14 ` Zhao Shujing [this message]
2007-08-22 13:09 ` Andrew Cagney
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