From: Joel Brobecker <brobecker@adacore.com>
To: Jan Vrany via Gdb-patches <gdb-patches@sourceware.org>
Cc: lsix@lancelotsix.com, Jan Vrany <jan.vrany@labware.com>,
Joel Brobecker <brobecker@adacore.com>
Subject: Re: [PATCH v2 1/2] ppc: use 'trap' ('tw, 31, 0, 0', 0x7fe00008) as breakpoint instruction
Date: Sat, 27 Nov 2021 10:45:33 +0400 [thread overview]
Message-ID: <YaHUDVp98G3bsnoR@adacore.com> (raw)
In-Reply-To: <20211124130926.2412617-2-jan.vrany@labware.com>
Hi Jan,
On Wed, Nov 24, 2021 at 01:09:25PM +0000, Jan Vrany via Gdb-patches wrote:
> GDB used to use "tw 12, r2, r2" as a breakpoint instruction. While it
> works, the PowerPC specifies 'tw, 31, 0, 0' (0x7fe00008) as the
> canonical unconditional trap.
> ---
> gdb/rs6000-tdep.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
> index 87a494e0bb8..43880fa4426 100644
> --- a/gdb/rs6000-tdep.c
> +++ b/gdb/rs6000-tdep.c
> @@ -824,8 +824,8 @@ rs6000_fetch_pointer_argument (struct frame_info *frame, int argi,
>
> /* Sequence of bytes for breakpoint instruction. */
>
> -constexpr gdb_byte big_breakpoint[] = { 0x7d, 0x82, 0x10, 0x08 };
> -constexpr gdb_byte little_breakpoint[] = { 0x08, 0x10, 0x82, 0x7d };
> +constexpr gdb_byte big_breakpoint[] = { 0x7f, 0xe0, 0x00, 0x08 };
> +constexpr gdb_byte little_breakpoint[] = { 0x08, 0x00, 0xe0, 0x7f };
>
> typedef BP_MANIPULATION_ENDIAN (little_breakpoint, big_breakpoint)
> rs6000_breakpoint;
I'm going to say OK, but I'd like to know what your source is
for this, so we can document that change. Part of me wonders
why we're making a change like this one on some code which
works, which is always a risk, no matter how small, unless we have
enough evidence that this is going to be helpful in practice.
Thank you,
--
Joel
next prev parent reply other threads:[~2021-11-27 6:45 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-23 15:42 [PATCH " Jan Vrany
2021-11-23 15:42 ` [PATCH 2/2] ppc: recognize all program traps Jan Vrany
2021-11-24 10:43 ` Lancelot SIX
2021-11-24 10:57 ` Lancelot SIX
2021-11-24 13:09 ` [PATCH v2 0/2] " Jan Vrany
2021-11-24 13:09 ` [PATCH v2 1/2] ppc: use 'trap' ('tw, 31, 0, 0', 0x7fe00008) as breakpoint instruction Jan Vrany
2021-11-27 6:45 ` Joel Brobecker [this message]
2021-11-29 11:50 ` Jan Vrany
2021-12-01 9:23 ` Joel Brobecker
2021-11-24 13:09 ` [PATCH v2 2/2] ppc: recognize all program traps Jan Vrany
2021-11-27 6:58 ` Joel Brobecker
2021-11-30 12:17 ` Pedro Alves
2021-12-01 13:52 ` Jan Vrany
2021-12-01 14:30 ` [PATCH v3 0/2] " Jan Vrany
2021-12-01 14:30 ` [PATCH v3 1/2] ppc: use "trap" ("tw, 31, 0, 0") as breakpoint instruction Jan Vrany
2021-12-04 10:16 ` Joel Brobecker
2021-12-01 14:30 ` [PATCH v3 2/2] ppc: recognize all program traps Jan Vrany
2021-12-04 10:18 ` Joel Brobecker
2021-12-07 23:30 ` Pedro Alves
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