[Xen-devel] pdb entered even when set to none

[Kip Macy <kmacy@xxxxxxxxxxxxxxx>]

In traps.c pdb_handle_exception is called on an int3:

asmlinkage void do_int3(struct pt_regs *regs, long error_code)
{
    struct task_struct *p = current;
    struct guest_trap_bounce *gtb =
guest_trap_bounce+smp_processor_id();
    trap_info_t *ti;

    if ( pdb_handle_exception(3, regs) == 0 )
        return;
<...>

It in turn goes through some elaborate checks that don't evaluate to
true when FreeBSD panics:

<...>
    if ( exceptionVector == 3 &&
         (xen_regs->xcs & 3) == 3 &&
         xen_regs->eip != pdb_system_call_next_addr + 1)
    {
        TRC(printf("pdb: user bkpt (0x%x) at 0x%x:0x%lx:0x%lx\n",
                   exceptionVector, xen_regs->xcs & 3, cr3,
xen_regs->eip));
        return 1;
    }

    /*
     * If PDB didn't set the breakpoint, is not single stepping,
     * is not entering a system call in a domain,
     * the user didn't press the magic debug key,
     * then we don't handle the exception.
     */
    bkpt = pdb_bkpt_search(cr3, xen_regs->eip - 1);
    if ( (bkpt == NULL) &&
         !pdb_stepping &&
         !pdb_system_call &&
         xen_regs->eip != pdb_system_call_next_addr + 1 &&
         (exceptionVector != KEYPRESS_EXCEPTION) &&
         xen_regs->eip < 0xc0000000)                   /* xenolinux for
now! */
    {
        TRC(printf("pdb: user bkpt (0x%x) at 0x%lx:0x%lx\n",
                   exceptionVector, cr3, xen_regs->eip));
        return 1;
    }
<...>

As far as I can tell, what you should be doing is returning 1
immediately if pdb_initialized is equal to zero.

Thanks.


                                -Kip





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