From: Catalin Marinas <catalin.marinas@arm.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Will Deacon <Will.Deacon@arm.com>
Subject: Re: [PATCH v2 17/31] arm64: System calls handling
Date: Mon, 3 Sep 2012 12:48:31 +0100 [thread overview]
Message-ID: <20120903114831.GA3313@mbp> (raw)
In-Reply-To: <20120822171309.GC2582@arm.com>
Hi Arnd,
On Wed, Aug 22, 2012 at 06:13:10PM +0100, Catalin Marinas wrote:
> On Wed, Aug 22, 2012 at 01:27:14PM +0100, Arnd Bergmann wrote:
> > On Wednesday 22 August 2012, Catalin Marinas wrote:
> > > But what's more important - moving this wrapper to glibc causes issues
> > > with the page size. We support both 4KB and 64KB pages on 64-bit systems
> > > (the latter without compat support). The kernel is in a better position
> > > to do the shift by a compile-time constant. Glibc would need to enquire
> > > the actual page size to do the shift before calling sys_mmap_pgoff. If
> > > we assume in glibc that the shift is always 12, we need another wrapper
> > > in the kernel anyway for 64KB page configuration. So passing the offset
> > > in bytes worked best for us.
> >
> > Right, the kernel interface should really be independent of the page
> > size, as sys_mmap2 normally is, and sys_mmap2 is not provided here.
>
> sys_mmap2 is indeed independent of the page size on most architectures
> assuming that the last argument represents the offset in units of 4096.
> The cris and ia64 seem to differ (one being 8K, the other variable).
>
> sys_mmap is also independent of the page size.
>
> But using sys_mmap2 for a 64-bit architecture, especially when the page
> size is not always 4K, does not bring any advantages. We end up doing a
> shift by 12 in glibc and another shift by (PAGE_SHIFT - 12) in the
> kernel wrapper. Unless I missed your point, I don't see the reason for
> using sys_mmap2 on a 64-bit architecture, apart from it being newer (and
> compat support should not have any relevance, we have different syscall
> tables anyway).
I forgot about this at the KS and we haven't got to a clear conclusion.
Do we (1) stick with the sys_mmap() for 64-bit systems and avoid offset
conversion in both glibc and kernel or (2) use sys_mmap2() with a 12
shift in glibc and (PAGE_SHIFT - 12) in the kernel wrapper?
I personally prefer (1) as it doesn't require a kernel wrapper and we
avoid the double shifting. A reason for (2) would be if we ever need
file offsets greater than 16EB.
--
Catalin
next prev parent reply other threads:[~2012-09-03 11:48 UTC|newest]
Thread overview: 170+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-14 17:52 [PATCH v2 00/31] AArch64 Linux kernel port Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 01/31] arm64: Assembly macros and definitions Catalin Marinas
2012-08-15 12:57 ` Arnd Bergmann
2012-08-14 17:52 ` [PATCH v2 02/31] arm64: Kernel booting and initialisation Catalin Marinas
2012-08-14 23:06 ` Olof Johansson
2012-08-15 17:37 ` Catalin Marinas
2012-08-15 19:03 ` Olof Johansson
2012-08-15 19:53 ` Catalin Marinas
2012-08-15 13:20 ` Arnd Bergmann
2012-08-15 17:06 ` Olof Johansson
2012-08-16 12:53 ` Catalin Marinas
2012-08-16 18:59 ` Nicolas Pitre
2012-08-17 11:20 ` Arnd Bergmann
2012-08-17 13:45 ` Catalin Marinas
2012-08-17 18:21 ` Nicolas Pitre
2012-08-17 8:56 ` Tony Lindgren
2012-08-17 9:41 ` Santosh Shilimkar
2012-08-17 10:05 ` Catalin Marinas
2012-08-17 10:10 ` Shilimkar, Santosh
2012-08-17 13:13 ` Tony Lindgren
2012-08-17 13:48 ` Catalin Marinas
2012-08-24 9:50 ` Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 03/31] arm64: Exception handling Catalin Marinas
2012-08-14 23:29 ` Olof Johansson
2012-08-14 23:47 ` Thomas Gleixner
2012-08-15 13:03 ` Arnd Bergmann
2012-08-16 10:05 ` Will Deacon
2012-08-16 11:54 ` Arnd Bergmann
2012-08-14 17:52 ` [PATCH v2 04/31] arm64: MMU definitions Catalin Marinas
2012-08-15 13:30 ` Arnd Bergmann
2012-08-15 13:39 ` Catalin Marinas
2012-08-15 16:34 ` Geert Uytterhoeven
2012-08-15 16:45 ` Catalin Marinas
2012-08-17 9:04 ` Tony Lindgren
2012-08-17 9:21 ` Catalin Marinas
2012-08-17 9:38 ` Tony Lindgren
2012-08-14 17:52 ` [PATCH v2 05/31] arm64: MMU initialisation Catalin Marinas
2012-08-15 13:45 ` Arnd Bergmann
2012-08-17 10:06 ` Santosh Shilimkar
2012-08-17 10:15 ` Catalin Marinas
2012-08-17 10:25 ` Shilimkar, Santosh
2012-08-14 17:52 ` [PATCH v2 06/31] arm64: MMU fault handling and page table management Catalin Marinas
2012-08-15 13:47 ` Arnd Bergmann
2012-08-17 16:07 ` Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 07/31] arm64: Process management Catalin Marinas
2012-08-14 23:50 ` Olof Johansson
2012-09-14 17:33 ` Catalin Marinas
2012-09-16 0:29 ` Olof Johansson
2012-08-15 13:53 ` Arnd Bergmann
2012-08-17 16:15 ` Catalin Marinas
2012-08-16 15:09 ` Tobias Klauser
2012-08-14 17:52 ` [PATCH v2 08/31] arm64: CPU support Catalin Marinas
2012-08-15 0:10 ` Olof Johansson
2012-08-20 15:57 ` Catalin Marinas
2012-08-20 20:47 ` Arnd Bergmann
2012-08-21 9:50 ` Catalin Marinas
2012-09-14 17:38 ` Catalin Marinas
2012-08-15 13:56 ` Arnd Bergmann
2012-08-20 16:00 ` Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 09/31] arm64: Cache maintenance routines Catalin Marinas
2012-08-17 9:57 ` Santosh Shilimkar
2012-08-17 10:07 ` Catalin Marinas
2012-08-17 10:12 ` Shilimkar, Santosh
2012-08-14 17:52 ` [PATCH v2 10/31] arm64: TLB maintenance functionality Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 11/31] arm64: IRQ handling Catalin Marinas
2012-08-14 23:22 ` Aaro Koskinen
2012-08-14 17:52 ` [PATCH v2 12/31] arm64: Atomic operations Catalin Marinas
2012-08-15 0:21 ` Olof Johansson
2012-08-14 17:52 ` [PATCH v2 13/31] arm64: Device specific operations Catalin Marinas
2012-08-15 0:33 ` Olof Johansson
2012-09-14 17:29 ` Catalin Marinas
2012-09-14 17:31 ` Arnd Bergmann
2012-09-14 17:39 ` Catalin Marinas
2012-09-16 0:28 ` Olof Johansson
2012-08-15 16:13 ` Arnd Bergmann
2012-08-17 9:19 ` Tony Lindgren
2012-08-14 17:52 ` [PATCH v2 14/31] arm64: DMA mapping API Catalin Marinas
2012-08-15 0:40 ` Olof Johansson
2012-08-21 13:05 ` Catalin Marinas
2012-08-15 16:16 ` Arnd Bergmann
2012-08-21 12:59 ` Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 15/31] arm64: SMP support Catalin Marinas
2012-08-15 0:49 ` Olof Johansson
2012-08-15 13:04 ` Arnd Bergmann
2012-08-17 9:21 ` Tony Lindgren
2012-08-17 9:32 ` Catalin Marinas
2012-08-17 9:39 ` Tony Lindgren
2012-08-14 17:52 ` [PATCH v2 16/31] arm64: ELF definitions Catalin Marinas
2012-08-15 14:15 ` Arnd Bergmann
2012-08-16 10:23 ` Will Deacon
2012-08-16 12:37 ` Arnd Bergmann
2012-08-21 16:06 ` Catalin Marinas
2012-08-21 18:17 ` Geert Uytterhoeven
2012-08-21 18:27 ` Catalin Marinas
2012-08-21 18:53 ` Mike Frysinger
2012-08-21 20:17 ` Arnd Bergmann
2012-09-05 19:56 ` Chris Metcalf
2012-08-14 17:52 ` [PATCH v2 17/31] arm64: System calls handling Catalin Marinas
2012-08-15 14:22 ` Arnd Bergmann
2012-08-21 17:51 ` Catalin Marinas
2012-08-21 20:14 ` Arnd Bergmann
2012-08-21 22:01 ` Catalin Marinas
2012-08-22 7:56 ` Arnd Bergmann
2012-08-22 10:29 ` Catalin Marinas
2012-08-22 12:27 ` Arnd Bergmann
2012-08-22 17:13 ` Catalin Marinas
2012-09-03 11:48 ` Catalin Marinas [this message]
2012-09-03 12:39 ` Arnd Bergmann
2012-08-14 17:52 ` [PATCH v2 18/31] arm64: VDSO support Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 19/31] arm64: Signal handling support Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 20/31] arm64: User access library functions Catalin Marinas
2012-08-15 14:49 ` [PATCH v2 20/31] arm64: User access library function Arnd Bergmann
2012-09-03 12:58 ` Catalin Marinas
2012-09-05 19:13 ` Russell King - ARM Linux
2012-09-05 21:01 ` Catalin Marinas
2012-09-05 21:05 ` Russell King - ARM Linux
2012-09-06 8:36 ` Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 21/31] arm64: 32-bit (compat) applications support Catalin Marinas
2012-08-15 14:34 ` Arnd Bergmann
2012-08-16 10:28 ` Will Deacon
2012-08-16 12:39 ` Arnd Bergmann
2012-08-23 6:46 ` PER_LINUX32, Was: " Arnd Bergmann
2012-08-23 10:42 ` Catalin Marinas
2012-08-28 18:28 ` Jiri Kosina
2012-08-24 10:43 ` Catalin Marinas
2012-08-26 4:49 ` Arnd Bergmann
2012-08-20 10:53 ` Pavel Machek
2012-08-20 20:34 ` Arnd Bergmann
2012-08-21 10:28 ` Pavel Machek
2012-08-14 17:52 ` [PATCH v2 22/31] arm64: Floating point and SIMD Catalin Marinas
2012-08-15 14:35 ` Arnd Bergmann
2012-08-14 17:52 ` [PATCH v2 23/31] arm64: Debugging support Catalin Marinas
2012-08-15 15:07 ` Arnd Bergmann
2012-08-16 10:47 ` Will Deacon
2012-08-16 12:49 ` Arnd Bergmann
2012-08-17 7:06 ` Arnd Bergmann
2012-08-20 9:07 ` Will Deacon
2012-08-20 9:27 ` Will Deacon
2012-08-20 20:10 ` Arnd Bergmann
2012-08-21 8:58 ` Will Deacon
2012-08-14 17:52 ` [PATCH v2 24/31] arm64: Add support for /proc/sys/debug/exception-trace Catalin Marinas
2012-08-15 15:08 ` Arnd Bergmann
2012-08-14 17:52 ` [PATCH v2 25/31] arm64: Performance counters support Catalin Marinas
2012-08-15 15:11 ` Arnd Bergmann
2012-08-16 10:51 ` Will Deacon
2012-08-14 17:52 ` [PATCH v2 26/31] arm64: Miscellaneous library functions Catalin Marinas
2012-08-15 15:21 ` Arnd Bergmann
2012-08-16 10:57 ` Will Deacon
2012-08-16 13:00 ` Arnd Bergmann
2012-08-16 14:11 ` Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 27/31] arm64: Loadable modules Catalin Marinas
2012-08-15 15:23 ` Arnd Bergmann
2012-08-15 15:35 ` Catalin Marinas
2012-08-15 16:16 ` Arnd Bergmann
2012-08-14 17:52 ` [PATCH v2 28/31] arm64: Generic timers support Catalin Marinas
2012-08-15 15:52 ` Arnd Bergmann
2012-08-16 12:40 ` Linus Walleij
2012-08-17 9:29 ` Tony Lindgren
2012-08-17 10:21 ` Santosh Shilimkar
2012-08-21 19:20 ` Christopher Covington
2012-08-14 17:52 ` [PATCH v2 29/31] arm64: Miscellaneous header files Catalin Marinas
2012-08-15 15:56 ` Arnd Bergmann
2012-08-14 17:52 ` [PATCH v2 30/31] arm64: Build infrastructure Catalin Marinas
2012-08-14 21:01 ` Sam Ravnborg
2012-08-15 16:07 ` Arnd Bergmann
2012-08-17 9:32 ` Tony Lindgren
2012-08-17 9:46 ` Catalin Marinas
2012-08-14 17:52 ` [PATCH v2 31/31] arm64: MAINTAINERS update Catalin Marinas
2012-08-15 15:57 ` Arnd Bergmann
2012-08-17 9:36 ` [PATCH v2 00/31] AArch64 Linux kernel port Tony Lindgren
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