From: Linus Torvalds <torvalds@linux-foundation.org>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-arch <linux-arch@vger.kernel.org>,
Nick Hu <nickhu@andestech.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Greentime Hu <green.hu@gmail.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vincent Chen <deanbo422@gmail.com>,
linux-riscv@lists.infradead.org
Subject: Re: [PATCH 4/6] uaccess: remove segment_eq
Date: Tue, 14 Jul 2020 08:27:14 -0700 [thread overview]
Message-ID: <CAHk-=wgpYFEPMfYmNR-9SuPaeC432sC7nmZrismRHQEiR2GM4g@mail.gmail.com> (raw)
In-Reply-To: <20200714105505.935079-5-hch@lst.de>
Ack, just with a note:
On Tue, Jul 14, 2020 at 4:06 AM Christoph Hellwig <hch@lst.de> wrote:
>
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -33,7 +33,7 @@ static inline void set_fs(mm_segment_t fs)
> set_thread_flag(TIF_FSCHECK);
> }
>
> -#define segment_eq(a, b) ((a).seg == (b).seg)
> +#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
> #define user_addr_max() (current->thread.addr_limit.seg)
This "uaccess_kernel()" interface is a better model anyway, because at
least on x86 (and from a quick glance at others), we might avoid the
exact equality comparison, and instead do simpler/better things.
On x86-64, for example, checking whether the limit has the high bit
set is not only more flexible and correct, it's much cheaper too.
Of course, trying to get rid of all this means that it doesn't matter
so much, but it would probably have been good to do this part years
ago regardless.
Linus
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next prev parent reply other threads:[~2020-07-14 15:27 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-14 10:54 clean up address limit helpers v2 Christoph Hellwig
2020-07-14 10:55 ` [PATCH 1/6] syscalls: use uaccess_kernel in addr_limit_user_check Christoph Hellwig
2020-07-18 1:38 ` Guenter Roeck
2020-07-18 9:48 ` Christoph Hellwig
2020-07-18 14:54 ` Guenter Roeck
2020-07-20 22:10 ` Guenter Roeck
2020-07-21 4:58 ` Christoph Hellwig
2020-07-21 5:15 ` Guenter Roeck
2020-07-21 5:20 ` Christoph Hellwig
2020-07-21 5:30 ` Guenter Roeck
2020-07-21 5:35 ` Christoph Hellwig
2020-07-14 10:55 ` [PATCH 2/6] nds32: use uaccess_kernel in show_regs Christoph Hellwig
2020-07-14 10:55 ` [PATCH 3/6] riscv: include <asm/pgtable.h> in <asm/uaccess.h> Christoph Hellwig
2020-07-14 10:55 ` [PATCH 4/6] uaccess: remove segment_eq Christoph Hellwig
2020-07-14 15:27 ` Linus Torvalds [this message]
2020-07-14 10:55 ` [PATCH 5/6] uaccess: add force_uaccess_{begin,end} helpers Christoph Hellwig
2020-07-14 15:29 ` Linus Torvalds
2020-07-14 10:55 ` [PATCH 6/6] exec: use force_uaccess_begin during exec and exit Christoph Hellwig
2020-07-15 3:33 ` Eric W. Biederman
2020-07-15 6:06 ` Christoph Hellwig
2020-07-16 23:49 ` clean up address limit helpers v2 Andrew Morton
2020-07-17 6:06 ` Christoph Hellwig
2020-07-20 15:54 ` [PATCH 0/6] arm: don't call addr_limit_user_check for nommu Christoph Hellwig
-- strict thread matches above, loose matches on Subject: below --
2020-07-10 13:57 clean up address limit helpers Christoph Hellwig
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
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