Re: [PATCH, v3] Expect SI_KERNEL or TRAP_BRKPT si_code values for MIPS breakpoint traps

[Luis Machado <lgustavo at codesourcery dot com>]

On 02/22/2016 07:41 PM, Pedro Alves wrote:
> On 02/22/2016 10:20 PM, Luis Machado wrote:
>
> > diff --git a/gdb/nat/linux-ptrace.h b/gdb/nat/linux-ptrace.h
> > index ba58717..72b32b1 100644
> > --- a/gdb/nat/linux-ptrace.h
> > +++ b/gdb/nat/linux-ptrace.h
> > @@ -140,11 +140,16 @@ struct buffer;
> >      in SPU code on a Cell/B.E.  However, SI_KERNEL is never seen
> >      on a SIGTRAP for any other reason.
> >
> > +   The MIPS kernel uses the default si_code of SI_KERNEL for software
> > +   breakpoints, hardware watchpoints and SIGTRAP's in general.
>
> If we get this for both software breakpoints and hardware watchpoints,
> then it seems to me that this change still leaves watchpoints broken,
> as I can't see how check_stopped_by_watchpoint is reached, in either
> gdb/linux-nat.c or gdbserver/linux-low.c.

With or without this specific breakpoint fix, hardware watchpoints are 
already broken for MIPS AFAICS.

MIPS' kernel has never set si_code to anything other than SI_KERNEL. 
When the change to expect TRAP_HWBKPT was committed, then hardware 
watchpoints stopped working properly for MIPS.

Now all hardware watchpoints produce are breakpoint-like traps that get 
silently ignored by GDB as "delayed software breakpoint trap". Neither 
GDB nor GDBserver can tell when a hardware watchpoint really happened by 
using si_code information.

But this seems to be a different issue and i think it should be handle 
separately.

> Also, "and SIGTRAP's in general." seems wrong.  I hope that that's
> not the case for user-sent SIGTRAPs?

I'll get this updated in the next version.