From: "Maciej W. Rozycki" <macro@orcam.me.uk>
To: Andy Chiu <andy.chiu@sifive.com>
Cc: Greg Savin <greg.savin@sifive.com>,
Greentime Hu <greentime.hu@sifive.com>,
Oleg Nesterov <oleg@redhat.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
linux-riscv@lists.infradead.org, gdb-patches@sourceware.org,
Andrew Burgess <andrew.burgess@embecosm.com>
Subject: Re: [PATCH] RISC-V: support for vector register accesses via ptrace() in RISC-V Linux native
Date: Thu, 10 Aug 2023 14:55:44 +0100 (BST) [thread overview]
Message-ID: <alpine.DEB.2.21.2308101436450.8596@angie.orcam.me.uk> (raw)
In-Reply-To: <alpine.DEB.2.21.2308101231560.25915@angie.orcam.me.uk>
On Thu, 10 Aug 2023, Maciej W. Rozycki wrote:
> > Does it make sense to you if we encapsulate this with a hwprobe syscall?
> > e.g provide a hwprobe entry to get system's VLENB. We will have to
> > increase and rearrange the buffer for NT_RISCV_VECTOR if we want to use
> > ptrace as the entry point for this purpose. I am not very sure if it'd be
> > too late to do though.
>
> No, how do you expect it to work with a core dump (that can be examined
> on a different system, or with a cross-debugger)? You need to change the
> API I'm afraid; it's unusable anyway. It's a pity the toolchain community
> wasn't consulted if you weren't sure how to design the interface. Better
> yet it would have been to implement the GDB side before the kernel part
> has been committed.
NB since this stuff went in with v6.5-rc1 and v6.5 hasn't been released
you can still back out the problematic change as no one is expected to use
RC stuff in production. Alternatively you can redefine NT_RISCV_VECTOR
for a corrected ABI, but I think it shouldn't be necessary. You just need
to act quickly as I guess there may be 1-2 further v6.5 RCs only and you
have to get with that to Linus right away. We can have a release or two
without NT_RISCV_VECTOR support for the otherwise included vector stuff,
it shouldn't be a big deal. There just won't be support for the debug
API.
CC-ing Linux ptrace/RISC-V maintainers now to bring their attention.
Maciej
next prev parent reply other threads:[~2023-08-10 13:55 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-03 23:01 Greg Savin
2023-08-04 0:21 ` John Baldwin
2023-08-08 22:50 ` [PATCH v2] " Greg Savin
2023-08-11 14:27 ` Andrew Burgess
2023-08-11 16:41 ` Greg Savin
2023-08-09 9:21 ` [PATCH] " Maciej W. Rozycki
2023-08-09 18:11 ` Greg Savin
2023-08-09 23:09 ` Maciej W. Rozycki
2023-08-10 10:35 ` Andy Chiu
2023-08-10 11:40 ` Maciej W. Rozycki
2023-08-10 13:55 ` Maciej W. Rozycki [this message]
2023-08-10 17:23 ` Andy Chiu
2023-08-10 21:08 ` Palmer Dabbelt
2023-08-10 21:21 ` Maciej W. Rozycki
2023-08-11 11:28 ` Andy Chiu
2023-08-10 14:05 ` Andy Chiu
2023-08-10 20:51 ` Maciej W. Rozycki
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