[sf-lug] save the mbr!

Adrien Lamothe alamozzz at yahoo.com
Sat Feb 24 19:46:09 PST 2007

It's too bad Red Hat didn't do anything with Code Fusion, which they got when they acquired Cygnus Solutions. Code Fusion had a special version of gdb, integrated into the Code Fusion GUI. Code Fusion was the closest thing to Borland style tools. If you hunt around the Red Hat site, you may be able to still find the source code for Code Fusion, I believe they had it there at some point.

Jason Turner <jturner at nonzerosums.org> wrote: Ahh, someone is just getting real curious... :-D

Well, let me say ahead of time... no bonus points for me.  But I only 
chime in here because, selfishly, I'm curious if anyone out there would 
recommend a particularly good interface(gui) to gdb.  Which is my first 
answer to your question about a disassembler.  Now, I'm primarily an 
emacs+gdb guy when playing with code on Linux.  But I have to admit I've 
never been as effective with that tool when debugging source(much less 
object) code than when I used Symantec or Borland tools on Windoze. 

So, I know gdb inside emacs is not an option for you, VI guy.  Have you 
tried to dump the code into gdb on the command line and seen anything 
helpful?  I just dunno ahead of time if that would pass all your 
stipulations.  But it's cheap to try, no?


jim stockford wrote:
> last meeting catherine suggested backing up the
> master boot record.
> i did it.
> Here's the story:
> as root in a terminal window using the bash shell:
> # dd if=/dev/hda of=./mbr bs=512 count=1
> i used the dd command
> if  is the input source. i think /dev/hda represents the
> entire primary master hard drive starting at byte zero
> of sector zero of track zero of side zero, in other words
> the master boot record area.
> of  is the output, ./mbr (in the current directory, a file
> with a name i made up -- mbr)
> bs  is the number of bytes to read at a time, 512, which
> i know is the number of bytes in the master boot record.
> count  is the number of blocks to transfer from if to of
> Non Geeks might want to stop here--this is how you
> get a backup of your system's master boot record,
> IF your machine is using IDE hard disks.
> the following is idle idiocy i find interesting with a
> request at bottom for a "real good" disassembler.
> # ls -l mbr
> -rw--r--r  1  root  root     512  Feb 23 19:44 mbr
> the ls command shows ./mbr has 512 bytes in it
> # file ./mbr
> mbr:     x86 boot sector, code offset 0x48
> hmmm, i don't know what "code offset" means,
> 0x48 is hexadecimal for 72 and i'm guessing
> this file has machine code that starts on byte
> 0x48.
> # od -h ./mbr > ./mbr.od
> od  the od -h command reads the .mbr file and
> outputs hexadecimal to a new file named ./mbr.od
> (which is 1544 bytes)
> # strings ./mbr > ./mbr.strings
> strings  the strings command outputs any ASCII
> sequences that are in the ./mbr file to a new file
> that I've named ./mbr.strings (which is 48 bytes).
> The contents are
> D|f1
> Geom
> Hard Disk
> Read
>   Error
> Well, to me that seems like the kind of strings that
> ought to be in the master boot record.
> # vi ./mbr
> well, it looks like martian, all right.
> okay, i know i'm a maniac, but hey! the vi editor
> can edit anything.
> # vi -b ./mbr
> this looks a little better, but only a little (the -b
> option tells vi it's working with a "binary" file).
> # dis
> -bash: dis: command not found
> damn! the  dis  command was on ATT sysVreviii
> where's a disassembler when you need one?  <-- geek question
> there are lots, but which is real good? <-- bonus geek question
> for me, "real good" is probably "real stupid" in that it will not
> fail on any input for any reason, does not expect ELF or other
> header data, just takes a byte stream and generates mnemonics
> for any machine code it finds; i've got 32-bit iAPX86 stuff.
> ever hopefully,
> jim
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