From: Christoph Hellwig <hch@lst.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Christoph Hellwig <hch@lst.de>, Nick Hu <nickhu@andestech.com>,
Greentime Hu <green.hu@gmail.com>,
Vincent Chen <deanbo422@gmail.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-riscv <linux-riscv@lists.infradead.org>,
Linux-Arch <linux-arch@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 5/6] uaccess: add force_uaccess_{begin,end} helpers
Date: Tue, 14 Jul 2020 09:12:11 +0200 [thread overview]
Message-ID: <20200714071211.GC776@lst.de> (raw)
In-Reply-To: <CAMuHMdUCmEeU0G9wkUxZKm5tC9YoB-KXSSCLKwpSia746Myebw@mail.gmail.com>
On Mon, Jul 13, 2020 at 03:19:42PM +0200, Geert Uytterhoeven wrote:
> > This used to set KERNEL_DS, and now it sets USER_DS, which looks wrong
> > superficially.
>
> Thanks for noticing, and sorry for missing that myself.
>
> The same issue is present for SuperH:
>
> - set_fs(KERNEL_DS);
> + oldfs = force_uaccess_begin();
>
> So the patch description should be:
>
> "Add helpers to wraper the get_fs/set_fs magic for undoing any damage
> done by set_fs(USER_DS)."
>
> and leave alone users setting KERNEL_DS?
Yes, this was broken. Fixed for the next version.
> > If the new behaviour is fine it suggests that the old behaviour was
> > wrong, or that this is superfluous and could go entirely.
> >
> > Geert?
>
> Nope, on m68k, TLB cache operations operate on the current address space.
> Hence to flush a kernel TLB entry, you have to switch to KERNEL_DS first.
>
> If we're guaranteed to be already using KERNEL_DS, I guess the
> address space handling can be removed. But can we be sure?
We can't be sure yet. But with a lot of my pending work we should be
able to get there in the not too far future.
next prev parent reply other threads:[~2020-07-14 7:12 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 13:57 clean up address limit helpers Christoph Hellwig
2020-07-10 13:57 ` [PATCH 1/6] syscalls: use uaccess_kernel in addr_limit_user_check Christoph Hellwig
2020-07-10 13:57 ` [PATCH 2/6] nds32: use uaccess_kernel in show_regs Christoph Hellwig
2020-07-13 10:02 ` Greentime Hu
2020-07-10 13:57 ` [PATCH 3/6] riscv: include <asm/pgtable.h> in <asm/uaccess.h> Christoph Hellwig
2020-07-21 23:02 ` Palmer Dabbelt
2020-07-10 13:57 ` [PATCH 4/6] uaccess: remove segment_eq Christoph Hellwig
2020-07-13 9:16 ` Geert Uytterhoeven
2020-07-13 10:05 ` Greentime Hu
2020-07-10 13:57 ` [PATCH 5/6] uaccess: add force_uaccess_{begin,end} helpers Christoph Hellwig
2020-07-13 9:12 ` Geert Uytterhoeven
2020-07-13 10:06 ` Greentime Hu
2020-07-13 12:21 ` Mark Rutland
2020-07-13 13:19 ` Geert Uytterhoeven
2020-07-14 7:12 ` Christoph Hellwig [this message]
2020-07-13 12:26 ` Mark Rutland
2020-07-10 13:57 ` [PATCH 6/6] exec: use force_uaccess_begin during exec and exit Christoph Hellwig
2020-07-10 15:25 ` clean up address limit helpers Linus Torvalds
2020-07-14 7:09 ` Christoph Hellwig
2020-07-14 15:33 ` Linus Torvalds
2020-07-14 10:54 clean up address limit helpers v2 Christoph Hellwig
2020-07-14 10:55 ` [PATCH 5/6] uaccess: add force_uaccess_{begin,end} helpers Christoph Hellwig
2020-07-14 15:29 ` Linus Torvalds
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