Re: [RFA/RFC] mips tracepoint: fix Bug 12013

[Hui Zhu <teawater at gmail dot com>]

On Wed, Dec 29, 2010 at 02:04, Pedro Alves <pedro@codesourcery.com> wrote:
> On Tuesday 28 December 2010 17:23:59, Pedro Alves wrote:
>> On Tuesday 28 December 2010 17:08:52, Joel Brobecker wrote:
>> > > Joel, ?do you think this patch can check in to 7.2.1.
>> >
>> > I think that it's borderline, and I'm tempted to say no, considering
>> > that this is not a crash or a regression (just a limitation). ?But
>> > it looks relatively safe to me. ?So, if Pedro agrees, it's OK with me.
>>
>> Yeah. ?I understand that without this patch, MIPS tracepoints are
>> practically useless on 7.2, so on those grounds, I'd be okay.
>>
>> However, I just went to check whether collecting a pseudo or
>> user register in x86/x86_64 still gives a reasonable error, and
>> I now get:
>>
>> ?>./gdb -q ./gdb
>> ?Reading symbols from /home/pedro/gdb/baseline/build/gdb/gdb...done.
>> ?(top-gdb) start
>> ?Temporary breakpoint 3 at 0x4565c3: file ../../src/gdb/gdb.c, line 29.
>> ?Starting program: /home/pedro/gdb/baseline/build/gdb/gdb
>> ?[Thread debugging using libthread_db enabled]
>>
>> ?Temporary breakpoint 3, main (argc=1, argv=0x7fffffffe108) at ../../src/gdb/gdb.c:29
>> ?29 ? ? ? ?memset (&args, 0, sizeof args);
>> ?(top-gdb) maint agent $sp
>> ?../../src/gdb/regcache.c:166: internal-error: register_type: Assertion `regnum >= 0 && regnum < descr->nr_cooked_registers' failed.
>> ?A problem internal to GDB has been detected,
>> ?further debugging may prove unreliable.
>> ?Quit this debugging session? (y or n)
>>
>> While before (on 7.2), we'd get:
>>
>> ?(top-gdb) maint agent $sp
>> ?'sp' is a pseudo-register; GDB cannot yet trace pseudoregister contents.
>>
>> We'll need to get this fixed this before considering a backport to 7.2.
>>
>>
>
> Fixed for now. ?I've reinstated the exact same old error, but under
> a stricter check: we now error out for user registers, but let
> pseudo-registers pass:
>
> ?(top-gdb) maint agent $pc
> ?'pc' is a pseudo-register; GDB cannot yet trace pseudoregister contents.
>
> Pseudo-registers will error out further on, on the new errors that Hui
> added when the new gdbarch callbacks aren't implemented. ?On x86_64:
>
> ?(top-gdb) maint agent $rsp
> ?Scope: 0x4565c3
> ?Reg mask: 80
> ? 0 ?end
>
> ?(top-gdb) maint agent $esp
> ?'esp' is a pseudo-register; GDB cannot yet trace its contents.
>
> --
> Pedro Alves
>
> 2010-12-28 ?Pedro Alves ?<pedro@codesourcery.com>
>
> ? ? ? ?gdb/
> ? ? ? ?* ax-gdb.c (gen_expr) <OP_REGISTER>: Error out if trying to
> ? ? ? ?collect a user register.
>
> ---
> ?gdb/ax-gdb.c | ? ?6 ++++++
> ?1 file changed, 6 insertions(+)
>
> Index: src/gdb/ax-gdb.c
> ===================================================================
> --- src.orig/gdb/ax-gdb.c ? ? ? 2010-12-28 16:22:01.000000000 +0000
> +++ src/gdb/ax-gdb.c ? ?2010-12-28 17:54:45.000000000 +0000
> @@ -1978,6 +1978,12 @@ gen_expr (struct expression *exp, union
> ? ? ? ?if (reg == -1)
> ? ? ? ? ?internal_error (__FILE__, __LINE__,
> ? ? ? ? ? ? ? ? ? ? ? ? ?_("Register $%s not available"), name);
> + ? ? ? /* No support for tracing user registers yet. ?*/
> + ? ? ? if (reg >= gdbarch_num_regs (exp->gdbarch)
> + ? ? ? ? ? + gdbarch_num_pseudo_regs (exp->gdbarch))
> + ? ? ? ? error (_("'%s' is a pseudo-register; "
> + ? ? ? ? ? ? ? ? ?"GDB cannot yet trace pseudoregister contents."),
> + ? ? ? ? ? ? ? ?name);
> ? ? ? ?value->kind = axs_lvalue_register;
> ? ? ? ?value->u.reg = reg;
> ? ? ? ?value->type = register_type (exp->gdbarch, reg);
>

(top-gdb) maintenance agent $pc
'pc' is a pseudo-register; GDB cannot yet trace pseudoregister contents.
(top-gdb) maintenance agent $ax
'ax' is a pseudo-register; GDB cannot yet trace its contents.

This place is a bit confusing.  Do you think we change the
"pseudo-register" to "user-register" in gen_expr?

For example:
(top-gdb) maintenance agent $pc
'pc' is a user-register; GDB cannot yet trace user-register contents.
(top-gdb) maintenance agent $ax
'ax' is a pseudo-register; GDB cannot yet trace its contents.


I make a patch for it.

Thanks,
Hui

2010-12-29  Hui Zhu  <teawater@gmail.com>

	* ax-gdb.c (gen_expr): Change error message.

Attachment: gen_expr_change_message.txt
Description: Text document