From: Luis Machado <luis.machado@arm.com>
To: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Cc: gdb-patches@sourceware.org, Andrew Burgess <aburgess@redhat.com>
Subject: Re: [PATCH v3 13/16] [gdb/generic] corefile/bug: Fixup (gcore) core file target description reading order
Date: Mon, 31 Jul 2023 12:38:07 +0100 [thread overview]
Message-ID: <b3ae8f10-8f23-2814-2457-b9e567147ed8@arm.com> (raw)
In-Reply-To: <878rb07mqm.fsf@linaro.org>
On 7/28/23 04:12, Thiago Jung Bauermann wrote:
>
> Luis Machado via Gdb-patches <gdb-patches@sourceware.org> writes:
>
>> Due to the nature of the AArch64 SVE/SME extensions in GDB, each thread
>> can potentially have distinct target descriptions/gdbarches.
>>
>> When loading a gcore-generated core file, at the moment GDB gives priority
>> to the target description dumped to NT_GDB_TDESC. Though technically correct
>> for most target, it doesn't work correctly for AArch64 with SVE or SME
>> support.
>>
>> The correct approach for AArch64/Linux is to rely on the
>> gdbarch_core_read_description hook, so it can figure out the proper target
>> description for a given thread based on the various available register notes.
>>
>> I think this should work for other architectures as well. If not, we may
>> need to adjust things so all architectures get the information that they
>> need for discovering the target description of the core file.
>
> The code to load the target description from the core file was added in
> commit 95ce627aeb9d "gdb: write target description into core file", by
> Andrew Burgess. My understanding of that commit message is that it was
> added before the gdbarch hook on purpose, and my reading of:
>
> “My primary motivation for adding this feature is that, in a future
> commit, I will be adding support for bare metal core dumps on some
> targets. For RISC-V specifically, I want to be able to dump all the
> available control status registers. As different targets will present
> different sets of register in their target description, including
> registers that are possibly not otherwise known to GDB I wanted a way
> to capture these registers in the core dump.”
>
> is that it doesn't work if reading from the target description comes
> last, though I'm not sure about that. I copied him in this email to see
> if he would like to chime in.
>
I think the risc-v case should still work as it doesn't provide a core_read_description hook. If one is added though, then gdb will
give that hook preference.
Usually the core_read_description hook is provided when the target runs hosted on an OS. So for bare metal we wouldn't have that hook implemented.
Still, I agree we might want to make sure both of these features coexist. The assumption a tdesc is the same for all the threads of a process, and that
this tdesc is exposed through a single note in the core file, doesn't hold true for AArch64 unfortunately.
It would've been true if we had a sizeless vector type, in which case all the threads of a process for AArch64 would have the exact same tdesc.
next prev parent reply other threads:[~2023-07-31 11:38 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-30 13:46 [PATCH v3 00/16] SME support for AArch64 gdb/gdbserver on Linux Luis Machado
2023-06-30 13:46 ` [PATCH v3 01/16] [gdb/aarch64] Fix register fetch/store order for native AArch64 Linux Luis Machado
2023-07-24 15:53 ` Thiago Jung Bauermann
2023-07-24 16:26 ` Luis Machado
2023-06-30 13:46 ` [PATCH v3 02/16] [gdb/aarch64] refactor: Rename SVE-specific files Luis Machado
2023-06-30 13:46 ` [PATCH v3 03/16] [gdb/gdbserver] refactor: Simplify SVE interface to read/write registers Luis Machado
2023-07-24 16:19 ` Thiago Jung Bauermann
2023-07-25 9:28 ` Luis Machado
2023-06-30 13:46 ` [PATCH v3 04/16] [gdb/aarch64] sve: Fix return command when using V registers in a SVE-enabled target Luis Machado
2023-06-30 13:46 ` [PATCH v3 05/16] [gdb/aarch64] sme: Enable SME registers and pseudo-registers Luis Machado
2023-07-26 20:01 ` Thiago Jung Bauermann
2023-07-27 9:01 ` Luis Machado
2023-07-28 1:19 ` Thiago Jung Bauermann
2023-06-30 13:46 ` [PATCH v3 06/16] [gdbserver/aarch64] refactor: Adjust expedited registers dynamically Luis Machado
2023-06-30 13:46 ` [PATCH v3 07/16] [gdbserver/aarch64] sme: Add support for SME Luis Machado
2023-07-27 19:41 ` Thiago Jung Bauermann
2023-06-30 13:46 ` [PATCH v3 08/16] [gdb/aarch64] sve: Fix signal frame z/v register restore Luis Machado
2023-07-27 21:52 ` Thiago Jung Bauermann
2023-07-31 12:22 ` Luis Machado
2023-06-30 13:46 ` [PATCH v3 09/16] [gdb/aarch64] sme: Signal frame support Luis Machado
2023-07-27 22:25 ` Thiago Jung Bauermann
2023-07-31 12:23 ` Luis Machado
2023-06-30 13:46 ` [PATCH v3 10/16] [gdb/aarch64] sme: Fixup sigframe gdbarch when vg/svg changes Luis Machado
2023-07-28 1:01 ` Thiago Jung Bauermann
2023-07-31 12:27 ` Luis Machado
2023-06-30 13:46 ` [PATCH v3 11/16] [gdb/aarch64] sme: Support TPIDR2 signal frame context Luis Machado
2023-06-30 13:46 ` [PATCH v3 12/16] [gdb/generic] corefile/bug: Use thread-specific gdbarch when dumping register state to core files Luis Machado
2023-06-30 13:46 ` [PATCH v3 13/16] [gdb/generic] corefile/bug: Fixup (gcore) core file target description reading order Luis Machado
2023-07-28 3:12 ` Thiago Jung Bauermann
2023-07-31 11:38 ` Luis Machado [this message]
2023-09-05 8:28 ` Luis Machado
2023-06-30 13:46 ` [PATCH v3 14/16] [gdb/aarch64] sme: Core file support for Linux Luis Machado
2023-08-03 0:18 ` Thiago Jung Bauermann
2023-08-03 11:37 ` Luis Machado
2023-08-04 20:45 ` Thiago Jung Bauermann
2023-06-30 13:46 ` [PATCH v3 15/16] [gdb/testsuite] sme: Add SVE/SME testcases Luis Machado
2023-08-04 0:59 ` Thiago Jung Bauermann
2023-08-11 15:42 ` Luis Machado
2023-08-12 0:42 ` Thiago Jung Bauermann
2023-06-30 13:46 ` [PATCH v3 16/16] [gdb/docs] sme: Document SME registers and features Luis Machado
2023-07-01 8:58 ` Eli Zaretskii
2023-07-03 9:52 ` Luis Machado
2023-07-03 12:03 ` Eli Zaretskii
2023-07-03 12:06 ` Luis Machado
2023-07-17 11:40 ` [PING][PATCH v3 00/16] SME support for AArch64 gdb/gdbserver on Linux Luis Machado
2023-07-24 8:15 ` Luis Machado
2023-08-04 21:24 ` [PATCH " Thiago Jung Bauermann
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