linux-kernel - Re: [RFC] regset ->get() API

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Message-Id: <20200221.112244.1426580944977593272.davem@davemloft.net>
Date:   Fri, 21 Feb 2020 11:22:44 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     viro@...iv.linux.org.uk
Cc:     torvalds@...ux-foundation.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, arnd@...db.de
Subject: Re: [RFC] regset ->get() API

From: Al Viro <viro@...iv.linux.org.uk>
Date: Fri, 21 Feb 2020 18:59:03 +0000

> Again, a couple of copy_regset_to_user(), but there's an additional
> twist - GETREGSET of 32bit task on sparc64 will use access_process_vm()
> when trying to fetch L0..L7/I0..I7 of other task, using copy_from_user()
> only when the target is equal to current.  For sparc32 this is not
> true - it's always copy_from_user() there, so the values it reports
> for those registers have nothing to do with the target process.  That
> part smells like a bug; by the time GETREGSET had been introduced
> sparc32 was not getting much attention, GETREGS worked just fine
> (not reporting L*/I* anyway) and for coredump it was accessing the
> caller's memory.  Not sure if anyone cares at that point...

That's definitely a bug and sparc64 is doing it correctly.