read/write arbitrary files

read/write arbitrary files

[Bjorn Helgaas]

I'd like to use gdb to examine and update arbitrary files.  In
particular, I'd like to disassemble and patch files like /dev/mem
that are not in executable or core formats.

Is there already a way to do this?  If not, could there be?  This
was a very useful feature of adb.

Bjorn

Re: read/write arbitrary files

[Michael Snyder]

Bjorn Helgaas wrote:
> I'd like to use gdb to examine and update arbitrary files.  In
> particular, I'd like to disassemble and patch files like /dev/mem
> that are not in executable or core formats.
> 
> Is there already a way to do this?  If not, could there be?  This
> was a very useful feature of adb.

It's not really what gdb is good for.
Arbitrary files such as /dev/mem have no symbols and no types.
It should be easy to either use an existing hex editor, or
write one to do this sort of patching.  This tool could be
orders of magnitude less complicated than gdb.

Re: read/write arbitrary files

[Bjorn Helgaas]

On Monday 25 August 2008 11:23:10 am Michael Snyder wrote:
> Bjorn Helgaas wrote:
> > I'd like to use gdb to examine and update arbitrary files.  In
> > particular, I'd like to disassemble and patch files like /dev/mem
> > that are not in executable or core formats.
> > 
> > Is there already a way to do this?  If not, could there be?  This
> > was a very useful feature of adb.
> 
> It's not really what gdb is good for.
> Arbitrary files such as /dev/mem have no symbols and no types.
> It should be easy to either use an existing hex editor, or
> write one to do this sort of patching.  This tool could be
> orders of magnitude less complicated than gdb.

The hex editor part is easy.  I know how to do that already.

The disassembly part is much harder, and this is the part
I'm looking for.  It'd be very handy to use all the
disassemblers and the well-known user interface of gdb.

Another useful feature of gdb is its knowledge of types.  It
would be convenient to be able to read type information from
an executable, then use that information to format structures
from /dev/mem.

Bjorn

Re: read/write arbitrary files

[Michael Snyder]

Bjorn Helgaas wrote:
> On Monday 25 August 2008 11:23:10 am Michael Snyder wrote:
>> Bjorn Helgaas wrote:
>>> I'd like to use gdb to examine and update arbitrary files.  In
>>> particular, I'd like to disassemble and patch files like /dev/mem
>>> that are not in executable or core formats.
>>>
>>> Is there already a way to do this?  If not, could there be?  This
>>> was a very useful feature of adb.
>> It's not really what gdb is good for.
>> Arbitrary files such as /dev/mem have no symbols and no types.
>> It should be easy to either use an existing hex editor, or
>> write one to do this sort of patching.  This tool could be
>> orders of magnitude less complicated than gdb.
> 
> The hex editor part is easy.  I know how to do that already.
> 
> The disassembly part is much harder, and this is the part
> I'm looking for.  It'd be very handy to use all the
> disassemblers and the well-known user interface of gdb.
> 
> Another useful feature of gdb is its knowledge of types.  It
> would be convenient to be able to read type information from
> an executable, then use that information to format structures
> from /dev/mem.

I see.

Well, if it were me, I think I would write a little
proxy program that could read /dev/mem, and then serve
memory packets to gdb using a socket and the gdb remote
protocol, after the fashion of gdbserver.