From: Simon Marchi <simark@simark.ca>
To: Pedro Alves <pedro@palves.net>,
Thiago Jung Bauermann <thiago.bauermann@linaro.org>,
gdb-patches@sourceware.org
Subject: Re: [PATCH v3 0/8] gdbserver improvements for AArch64 SVE support
Date: Mon, 6 Feb 2023 15:05:09 -0500 [thread overview]
Message-ID: <dad86044-18ed-92b6-b074-2dbe77008c54@simark.ca> (raw)
In-Reply-To: <28bdd610-982d-aebb-ebc7-17b6d5fd80ed@palves.net>
> Ah! I had also suggested to you something like that at the Cauldron (when we were in line
> for lunch. :-D However, IIRC, I had suggested that we should be able to cache the tdesc by filename.
>
> Let me explain -- when we fetch a target description, we actually tell the server
> to retrieve a tdesc _by a given filename_. By default, we ask for target.xml, like this:
>
> qXfer:features:read:target.xml
>
> but then, the retrieved target.xml file may "xi:include" some other file, like for example these do:
>
> gdb/features/s390-linux64.xml:14: <xi:include href="s390-core64.xml"/>
> gdb/features/s390-linux64.xml:15: <xi:include href="s390-acr.xml"/>
> gdb/features/s390-linux64.xml:16: <xi:include href="s390-fpr.xml"/>
>
> (try grepping for xi:include in the gdb/features/ dir for a lot more hits.)
>
> and so when processing each of those xi:include's, gdb sends another qXfer:features:read packet,
> with the corresponding included filename, like e.g.,
>
> qXfer:features:read:s390-core64.xml
>
> Here's what the manual says:
>
> @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
> @anchor{qXfer target description read}
> Access the @dfn{target description}. @xref{Target Descriptions}. The
> annex specifies which XML document to access. The main description is
> always loaded from the @samp{target.xml} annex.
>
> So basically I am suggesting that instead a new ID mechanism, we should be able to
> use the preexisting annex/filename concept as key. That means that the stop reply and
> the thread listing would include a new "tdesc=foo.xml" attribute, instead of this
> ID that then is defined to map to "target-id-%u.xml", which is basically admitting
> that tdesc filenames exist anyhow.
Just for completeness, how do you envision that working for SVE?
GDBserver would make up unique names for each configuration, like
"target-vq-%d.xml"?
If caching using filenames as keys, what is the scope of that namespace?
Per remote connection, per inferior? I think it wouldn't work per
remote connection, because fetching "target.xml" for two different
inferiors could give two different answers.
Tangentially, I'm wondering if querying qXfer:features:read (mostly
fetching "target.xml" is going to become thread-sensitive. In other
words, if GDB set the general thread to a thread with vq == A, gets
target.xml, then sets the general thread to a thread with vq == B, then
gets target.xml, is it going to get two different target descriptions?
I think that it would make sense to do so *. Therefore, caching
target.xml per-inferior wouldn't be reliable either. And if included
files could vary per thread, you'd have to make sure to give them unique
names.
* I think that since we're going towards thread-specific tdescs, the
process-wide tdesc is going to become an obsolete concept, maybe just
kept for backwards compatibility for when an old GDB not aware of
per-thread tdescs talks to a new GDBserver aware of it, or vice versa.
Simon
next prev parent reply other threads:[~2023-02-06 20:05 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-30 4:45 Thiago Jung Bauermann
2023-01-30 4:45 ` [PATCH v3 1/8] gdbserver: Add assert in find_register_by_number Thiago Jung Bauermann
2023-01-31 17:05 ` Simon Marchi
2023-01-31 19:49 ` Thiago Jung Bauermann
2023-02-01 15:43 ` Simon Marchi
2023-01-30 4:45 ` [PATCH v3 2/8] gdbserver: Add PID parameter to linux_get_auxv and linux_get_hwcap Thiago Jung Bauermann
2023-02-01 9:07 ` Luis Machado
2023-02-01 10:54 ` Andrew Burgess
2023-02-01 16:01 ` Simon Marchi
2023-02-01 19:33 ` Thiago Jung Bauermann
2023-02-01 19:53 ` Simon Marchi
2023-02-01 21:55 ` Thiago Jung Bauermann
2023-02-06 19:54 ` Pedro Alves
2023-02-06 20:16 ` Simon Marchi
2023-02-07 15:19 ` Pedro Alves
2023-02-07 21:47 ` Thiago Jung Bauermann
2023-02-09 1:31 ` Simon Marchi
2023-02-10 3:54 ` Thiago Jung Bauermann
2023-02-07 22:28 ` Thiago Jung Bauermann
2023-01-30 4:45 ` [PATCH v3 3/8] gdbserver/linux-aarch64: Factor out function to get aarch64_features Thiago Jung Bauermann
2023-02-01 8:59 ` Luis Machado
2023-02-01 16:04 ` Simon Marchi
2023-02-01 22:13 ` Thiago Jung Bauermann
2023-01-30 4:45 ` [PATCH v3 4/8] gdbserver/linux-aarch64: When thread stops, update its target description Thiago Jung Bauermann
2023-02-01 9:05 ` Luis Machado
2023-02-01 11:06 ` Andrew Burgess
2023-02-01 16:21 ` Simon Marchi
2023-02-01 16:32 ` Luis Machado
2023-02-02 2:54 ` Thiago Jung Bauermann
2023-02-02 3:47 ` Simon Marchi
2023-02-03 3:47 ` Thiago Jung Bauermann
2023-02-03 11:13 ` Luis Machado
2023-02-04 15:26 ` Thiago Jung Bauermann
2023-02-03 11:11 ` Luis Machado
2023-02-04 15:21 ` Thiago Jung Bauermann
2023-02-06 9:07 ` Luis Machado
2023-02-06 12:15 ` Thiago Jung Bauermann
2023-02-06 20:29 ` Pedro Alves
2023-02-07 8:11 ` Luis Machado
2023-02-07 14:39 ` Thiago Jung Bauermann
2023-02-03 10:57 ` Luis Machado
2023-02-04 6:18 ` Thiago Jung Bauermann
2023-02-06 20:26 ` Pedro Alves
2023-02-07 21:06 ` Thiago Jung Bauermann
2023-02-09 2:46 ` Simon Marchi
2023-02-10 3:29 ` Thiago Jung Bauermann
2023-02-10 14:56 ` Luis Machado
2023-02-10 15:04 ` Tom Tromey
2023-02-10 15:28 ` Luis Machado
2023-02-10 17:26 ` Thiago Jung Bauermann
2023-02-10 21:01 ` Simon Marchi
2023-01-30 4:45 ` [PATCH v3 5/8] gdbserver: Transmit target description ID in thread list and stop reply Thiago Jung Bauermann
2023-01-30 12:52 ` Eli Zaretskii
2023-01-30 14:05 ` Thiago Jung Bauermann
2023-02-01 9:39 ` Luis Machado
2023-02-01 12:07 ` Andrew Burgess
2023-02-01 13:03 ` Eli Zaretskii
2023-02-01 17:37 ` Simon Marchi
2023-02-02 20:36 ` Thiago Jung Bauermann
2023-02-02 20:56 ` Simon Marchi
2023-02-01 20:46 ` Simon Marchi
2023-02-02 21:43 ` Thiago Jung Bauermann
2023-02-01 14:51 ` Andrew Burgess
2023-02-01 17:03 ` Simon Marchi
2023-02-02 19:52 ` Thiago Jung Bauermann
2023-02-02 20:51 ` Simon Marchi
2023-02-03 2:44 ` Thiago Jung Bauermann
2023-02-03 16:29 ` Andrew Burgess
2023-02-04 6:08 ` Thiago Jung Bauermann
2023-02-03 11:22 ` Luis Machado
2023-02-03 12:50 ` Simon Marchi
2023-01-30 4:45 ` [PATCH v3 6/8] gdb/remote: Parse tdesc field in stop reply and threads list XML Thiago Jung Bauermann
2023-02-01 9:52 ` Luis Machado
2023-02-05 0:06 ` Thiago Jung Bauermann
2023-02-06 9:10 ` Luis Machado
2023-02-01 14:32 ` Andrew Burgess
2023-02-01 19:50 ` Simon Marchi
2023-02-01 20:16 ` Simon Marchi
2023-02-03 11:27 ` Luis Machado
2023-02-03 13:19 ` Simon Marchi
2023-02-03 16:33 ` Andrew Burgess
2023-01-30 4:45 ` [PATCH v3 7/8] gdb/aarch64: Detect vector length changes when debugging remotely Thiago Jung Bauermann
2023-02-01 9:58 ` Luis Machado
2023-02-01 15:26 ` Andrew Burgess
2023-02-01 20:20 ` Simon Marchi
2023-02-03 11:31 ` Luis Machado
2023-02-03 16:38 ` Andrew Burgess
2023-02-03 19:07 ` Simon Marchi
2023-01-30 4:45 ` [PATCH v3 8/8] gdb/testsuite: Add test to exercise multi-threaded AArch64 SVE inferiors Thiago Jung Bauermann
2023-02-01 10:10 ` Luis Machado
2023-02-06 19:11 ` [PATCH v3 0/8] gdbserver improvements for AArch64 SVE support Pedro Alves
2023-02-06 20:05 ` Simon Marchi [this message]
2023-02-06 21:06 ` Pedro Alves
2023-02-07 13:49 ` Simon Marchi
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