[Libguestfs] hang after seabios

[Richard W.M. Jones]

On Fri, Aug 01, 2014 at 07:43:08AM -0700, Zetan Drableg wrote:
> Ok now we are getting somewhere! Those old vars did the trick.
> libguestfs-test-tool launched with qemu-wrapper as expected with the
> debug port open.
> Now on to the fun part!
> 
> (gdb) set architecture i8086
> The target architecture is assumed to be i8086
> (gdb) break *0x7c00
> Breakpoint 1 at 0x7c00
> (gdb) target remote :1234
> Remote debugging using :1234
> 0x0000fff0 in ?? ()
> (gdb) cont
> Continuing.
> 
> The breakpoint you documented as when the boot sector has been loaded
> into memory by the BIOS and control is passed to the boot sector.
> Never hits the breakpoint.....
> 
> Next steps?
> 
> Do I need to load a symbol table? Where might I find it?

This is getting very much to the edge of my experience, but yes, you
probably do need to load the symbol table, and I know how.

First install the kernel-debuginfo package that exactly corresponds to
the kernel which is being run inside the guest.  You can usually tell
which kernel that is by looking at the output of supermin (it's
usually the one which has the highest version number out of all of
those "picked").

Then in the kernel-debuginfo package, find the 'vmlinux' file, eg:

  $ rpm -ql kernel-debuginfo | grep vmlinux
  /usr/lib/debug/lib/modules/3.14.4-200.fc20.x86_64/vmlinux

Then you can get gdb to take the symbols from that file using
the gdb command:

  (gdb) symbol-file /path/to/vmlinux

Rich.

-- 
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