Re: [Xen-devel] possible changes was Re: [PATCH] make domu_debug run-time option + fix int3 handling for MP

[Kip Macy <kmacy@xxxxxxxxxx>]

> Doesn't the gdb server have to attach to the new vm to be able to set 
> the breakpoint, leading to a race anyway? Or have you some way to 
> pre-insert an int3?

There have been times when I've messed things up really early on so I've just 
re-compiled with an int3 in locore.s. For developers who wan't to be able to 
set 
breakpoints early in boot, I've added a boot time option to the command line 
that gets handled in machdep.c:

        if ((caddr_t)xen_start_info->cmd_line)
                kern_envp = xen_setbootenv((caddr_t)xen_start_info->cmd_line);

        boothowto |= xen_boothowto(kern_envp);

        if (boothowto & RB_GDB_PAUSE)
            __asm__("int $0x3;");

This way the VM got paused very early on in boot so that when the gdbserver got 
to attaching to it it hadn't gotten very far.

==========================================================================

But my recent jaunt through xm has lead me to a cleaner solution:

gopts.opt('paused', short='p',
          fn=set_true, default=0,
          use='Leave the domain paused after it is created.')


So I think we're good.

Thanks.


                                        -Kip

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