From: "Sangamesh Mallayya" <sangamesh.swamy@in.ibm.com>
To: "Ulrich Weigand" <uweigand@de.ibm.com>
Cc: gdb-patches@sourceware.org, kevinb@redhat.com (Kevin Buettner)
Subject: Re: [PATCH] Adding support for reding signal handler frame in AIX
Date: Thu, 27 Sep 2018 08:33:00 -0000 [thread overview]
Message-ID: <OF4C5ED06A.3C846B3C-ON65258315.002EABF7-65258315.002F0301@notes.na.collabserv.com> (raw)
In-Reply-To: <20180912135319.E5948D80320@oc3748833570.ibm.com>
Thanks Ulrich and kevin for the review and comments.
Sorry for the late reply as i was off due to personal emergency.
I will have look at the suggestions and implement the new changes.
Thanks,
Sangamesh
From: "Ulrich Weigand" <uweigand@de.ibm.com>
To: Sangamesh Mallayya/India/IBM@IBMIN
Cc: kevinb@redhat.com (Kevin Buettner), gdb-patches@sourceware.org
Date: 09/12/2018 07:23 PM
Subject: Re: [PATCH] Adding support for reding signal handler frame
in AIX
Sangamesh Mallayya wrote:
> Yes. Thanks!
> Earlier code was calling validate function twice which wasn't required.
> We can remove that AIX ifdef and i have made the below changes. Rest
all=20
> are same.
> Let me know your view on this.
>
> # diff -u tramp-frame.c_orig tramp-frame.c
> --- tramp-frame.c_orig 2018-08-27 03:25:49 +0000
> +++ tramp-frame.c 2018-09-07 10:20:09 +0000
> @@ -86,11 +86,15 @@
> struct gdbarch *gdbarch =3D get_frame_arch (this_frame);
> enum bfd_endian byte_order =3D gdbarch_byte_order (gdbarch);
> int ti;
> + CORE_ADDR old_pc =3D pc;
> =20
> /* Check if we can use this trampoline. */
> if (tramp->validate && !tramp->validate (tramp, this_frame, &pc))
> return 0;
> -
> + if ((tramp->insn[0].bytes =3D=3D TRAMP_SENTINEL_INSN) &&
> + (tramp->insn[1].bytes =3D=3D AIX_TRAMP_SENTINEL_INSN) &&
> + (old_pc < 0x1000000))
> + return pc;
I agree with Kevin that code like this shouldn't be in common code.
It looks like the underlying problem is that tramp-frame isn't a
good match for what you're trying to do: tramp-frame tries to
detect trampolines by matching well-known *code sequences*.
However, you don't actually have any code sequence to match,
but want to identify trampolines solely by their PC. Since you
pass no code sequence to the tramp-frame matcher, it will actually
never match.
I'd suggest the best way forward is to not actually use tramp-frame
at all then, but just write your own matcher based directly on a
trad-frame cache.
An example to look at might be s390_stub_frame_unwind. Along those
lines, you can implement a sniffer that checks for special PC value
(and possibly a backchain zero check in addition), and then implement
this_id and prev_register routines based on a trad-frame register
cache (you should be able to use the aix_sigtramp_cache routine in
your patch as-is for that part).
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU/Linux compilers and toolchain
Ulrich.Weigand@de.ibm.com
next prev parent reply other threads:[~2018-09-27 8:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-29 5:54 Sangamesh Mallayya
2018-09-04 23:18 ` Kevin Buettner
2018-09-10 6:32 ` Sangamesh Mallayya
2018-09-10 17:34 ` Kevin Buettner
2018-09-12 13:53 ` Ulrich Weigand
2018-09-27 8:33 ` Sangamesh Mallayya [this message]
[not found] ` <OF4C5ED06A.3C846B3C-ON65258315.002EABF7-65258315.002F01D3@LocalDomain>
2018-10-30 7:16 ` Sangamesh Mallayya
2018-10-30 10:20 ` Ulrich Weigand
2018-10-31 10:18 ` Sangamesh Mallayya
2018-10-31 10:37 ` Ulrich Weigand
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