linux-kernel - Re: [PATCH 1/2] riscv: ptrace: Use the correct API for `fcsr' access

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Message-ID: <20200805020745.GL1236603@ZenIV.linux.org.uk>
Date:   Wed, 5 Aug 2020 03:07:45 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     macro@....com, linux-riscv@...ts.infradead.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/2] riscv: ptrace: Use the correct API for `fcsr' access

On Tue, Aug 04, 2020 at 07:01:01PM -0700, Palmer Dabbelt wrote:

> > We currently have @start_pos fixed at 0 across all calls, which works as
> > a result of the implementation, in particular because we have no padding
> > between the FP general registers and the FP control and status register,
> > but appears not to have been the intent of the API and is not what other
> > ports do, requiring one to study the copy handlers to understand what is
> > going on here.

start_pos *is* fixed at 0 and it's going to go away, along with the
sodding user_regset_copyout() very shortly.  ->get() is simply a bad API.
See vfs.git#work.regset for replacement.  And ->put() is also going to be
taken out and shot (next cycle, most likely).