From: Yury Norov <ynorov@caviumnetworks.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: <linux-arm-kernel@lists.infradead.org>, <pinskia@gmail.com>,
<Prasun.Kapoor@caviumnetworks.com>, <catalin.marinas@arm.com>,
<Nathan_Lynch@mentor.com>, <linux-kernel@vger.kernel.org>,
<agraf@suse.de>, <klimov.linux@gmail.com>, <broonie@kernel.org>,
<jan.dakinevich@gmail.com>, <joseph@codesourcery.com>,
<ddaney.cavm@gmail.com>, <schwab@suse.de>,
<bamvor.zhangjian@huawei.com>,
<philipp.tomsich@theobroma-systems.com>,
<andrey.konovalov@linaro.org>,
<christoph.muellner@theobroma-systems.com>
Subject: Re: [PATCH v6 14/19] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it
Date: Wed, 2 Dec 2015 12:15:03 +0300 [thread overview]
Message-ID: <20151202091503.GA15980@yury-N73SV> (raw)
In-Reply-To: <1712431.VUth4NvudT@wuerfel>
On Wed, Dec 02, 2015 at 09:37:05AM +0100, Arnd Bergmann wrote:
> On Wednesday 02 December 2015 02:35:03 Yury Norov wrote:
> > On Tue, Dec 01, 2015 at 11:39:42PM +0100, Arnd Bergmann wrote:
> > > On Wednesday 02 December 2015 00:29:04 Yury Norov wrote:
> > > I'm not sure I understand this part. What changes specifically do we need?
> > >
> >
> > For kernel:
> >
> > diff --git a/arch/arm64/include/asm/shmparam.h b/arch/arm64/include/asm/shmparam.h
> > index 4df608a..e368a55 100644
> > --- a/arch/arm64/include/asm/shmparam.h
> > +++ b/arch/arm64/include/asm/shmparam.h
> > @@ -21,7 +21,7 @@
> > * alignment value. Since we don't have aliasing D-caches, the rest of
> > * the time we can safely use PAGE_SIZE.
> > */
> > -#define COMPAT_SHMLBA 0x4000
> > +#define COMPAT_SHMLBA (4 * PAGE_SIZE)
> >
> > #include <asm-generic/shmparam.h>
> >
> > diff --git a/arch/arm64/kernel/sys_ilp32.c b/arch/arm64/kernel/sys_ilp32.c
> > index c5bc712..877bedf 100644
> > --- a/arch/arm64/kernel/sys_ilp32.c
> > +++ b/arch/arm64/kernel/sys_ilp32.c
> > @@ -42,15 +42,12 @@ asmlinkage long sys_rt_sigreturn_wrapper(void);
> > #define compat_sys_pwrite64 sys_pwrite64
> > #define compat_sys_readahead sys_readahead
> > #define compat_sys_rt_sigaction sys_rt_sigaction
> > -#define compat_sys_shmat sys_shmat
> > #define compat_sys_sync_file_range sys_sync_file_range
> > #define compat_sys_truncate64 sys_truncate
> > #define compat_sys_sigaltstack sys_sigaltstack
> >
> > For library - just create a header in ilp32 directory that defines
> > SHMLBA exactly as arm: __getpagesize () << 2
>
> I think we both reversed our positions here ;-)
>
> The 4*PAGE_SIZE on ARM is an architecture specific oddity, I believe
> to work around aliasing caches on ARMv6. As no other architecture does
> this, we're probably better off not duplicating it for aarch64-ilp32
> and just use sys_shmat as your v6 patch does.
>
> > > It sounds like shmat is one of the cases we an override makes sense
> > > and we should use sys_shmat with PAGE_SIZE for aarch64 ilp32 mode.
> > >
> >
> > [...]
> >
> > > We normally assume that the page size on ARM is fixed to 4K, so
> > > there might be user space that just hardcodes 16K SHMLBA
> >
> > It means that we should use compat_sys_shmat because hardcoded
> > userspace may have a chance to work for 4K pages. If we'll use
> > sys_shmat (and so 4K SHMLBA), we'll definitely make hardcoded
> > userspace broken. Non-hardcoded userspace will work anyway.
> >
> > We can describe in documentation that 4k pages are prefferable.
>
> The hardcoded user space would only apply to old source code that
> specifically tries to adapt to what ARM does, but gets it wrong,
> If we have source code that is converted from x86 or mips and
> hardcodes anything, it's more likely to be the normal __getpagesize().
>
> Arnd
Hmm... OK. Let's have non-compat shmat here...
next prev parent reply other threads:[~2015-12-02 9:16 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-17 21:16 [RFC2 PATCH v6 00/19] ILP32 for ARM64 Yury Norov
2015-11-17 21:16 ` [PATCH v6 01/19] arm64:ilp32: add documentation on the ILP32 ABI " Yury Norov
2015-11-18 8:09 ` Zhangjian (Bamvor)
2015-11-17 21:16 ` [PATCH v6 02/19] arm64: ensure the kernel is compiled for LP64 Yury Norov
2015-11-17 21:16 ` [PATCH v6 03/19] arm64: rename COMPAT to AARCH32_EL0 in Kconfig Yury Norov
2015-11-17 21:16 ` [PATCH v6 04/19] arm64: change some CONFIG_COMPAT over to use CONFIG_AARCH32_EL0 instead Yury Norov
2015-12-03 12:02 ` Catalin Marinas
2015-12-04 21:58 ` Yury Norov
2015-11-17 21:16 ` [PATCH v6 05/19] arm64:uapi: set __BITS_PER_LONG correctly for ILP32 and LP64 Yury Norov
2015-12-03 11:31 ` Catalin Marinas
2015-12-03 11:36 ` Dr. Philipp Tomsich
2015-11-17 21:16 ` [PATCH v6 06/19] arm64:ilp32: share signal structures between ILP32 and LP64 ABIs Yury Norov
2015-11-17 22:14 ` Arnd Bergmann
2015-11-17 21:16 ` [PATCH v6 07/19] arm64: introduce is_a32_task and is_a32_thread (for AArch32 compat) Yury Norov
2015-12-03 12:13 ` Catalin Marinas
2015-12-04 17:05 ` Yury Norov
2015-12-05 11:00 ` Catalin Marinas
2015-11-17 21:16 ` [PATCH v6 08/19] arm64:ilp32: add is_ilp32_compat_{task,thread} and TIF_32BIT_AARCH64 Yury Norov
2015-11-17 21:16 ` [PATCH v6 09/19] arm64:ilp32: share HWCAP between LP64 and ILP32 Yury Norov
2015-11-17 21:16 ` [PATCH v6 10/19] arm64:ilp32 use the native LP64 'start_thread' for ILP32 threads Yury Norov
2015-12-03 12:20 ` Catalin Marinas
2015-11-17 21:16 ` [PATCH v6 11/19] arm64:ilp32: support core dump generation for ILP32 Yury Norov
2015-12-03 16:39 ` Catalin Marinas
2015-11-17 21:16 ` [PATCH v6 12/19] ptrace: Allow compat to use the native siginfo Yury Norov
2015-11-17 21:16 ` [PATCH v6 13/19] arm64: ilp32: common 32-bit wrappers Yury Norov
2015-11-17 21:16 ` [PATCH v6 14/19] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Yury Norov
2015-11-17 21:57 ` Arnd Bergmann
2015-11-18 8:14 ` Arnd Bergmann
2015-11-19 13:21 ` Andreas Schwab
2015-11-19 13:32 ` Arnd Bergmann
2015-11-30 15:34 ` Arnd Bergmann
2015-11-30 20:21 ` Yury Norov
2015-11-30 21:49 ` Arnd Bergmann
2015-12-01 0:20 ` Andrew Pinski
2015-12-01 0:40 ` Yury Norov
2015-12-01 10:26 ` Arnd Bergmann
2015-12-01 9:20 ` Andreas Schwab
2015-12-01 10:22 ` Arnd Bergmann
2015-12-01 11:01 ` Andreas Schwab
2015-12-01 11:30 ` Arnd Bergmann
2015-12-02 0:24 ` Yury Norov
2015-12-02 10:03 ` Arnd Bergmann
2015-12-03 17:17 ` Catalin Marinas
2015-12-01 21:29 ` Yury Norov
2015-12-01 22:39 ` Arnd Bergmann
2015-12-01 23:35 ` Yury Norov
2015-12-02 8:37 ` Arnd Bergmann
2015-12-02 9:15 ` Yury Norov [this message]
2015-12-02 10:35 ` Yury Norov
2015-12-02 13:46 ` Arnd Bergmann
2015-12-02 13:54 ` Arnd Bergmann
2015-12-02 13:57 ` Will Deacon
2015-12-03 17:47 ` Catalin Marinas
2015-12-03 18:14 ` Yury Norov
2015-12-03 20:42 ` Arnd Bergmann
2015-12-02 10:01 ` Yury Norov
2015-12-02 11:03 ` Arnd Bergmann
2015-11-17 21:16 ` [PATCH v6 15/19] arm64: ilp32: force IPC_64 in msgctl, shmctl, semctl Yury Norov
2015-11-17 22:07 ` Arnd Bergmann
2015-11-18 8:25 ` Andreas Schwab
2015-11-18 9:23 ` Arnd Bergmann
2015-11-18 10:07 ` Geert Uytterhoeven
2015-11-18 12:04 ` Arnd Bergmann
2015-11-17 21:16 ` [PATCH v6 16/19] aarch64: ilp32: use generic stat64 structure Yury Norov
2015-11-17 22:09 ` Arnd Bergmann
2015-11-18 20:36 ` Yury Norov
2015-11-18 20:45 ` Arnd Bergmann
2015-11-17 21:16 ` [PATCH v6 17/19] arm64:ilp32: use the native siginfo instead of the compat siginfo Yury Norov
2015-11-17 21:16 ` [PATCH v6 18/19] arm64:ilp32: change COMPAT_ELF_PLATFORM to report a a subplatform for ILP32 Yury Norov
2015-11-18 8:11 ` Zhangjian (Bamvor)
2015-11-18 11:21 ` pinskia
2015-11-18 20:25 ` Yury Norov
2015-11-18 21:47 ` Dr. Philipp Tomsich
2015-11-17 21:16 ` [PATCH v6 19/19] arm64:ilp32: add ARM64_ILP32 to Kconfig Yury Norov
2015-11-18 8:00 ` [RFC2 PATCH v6 00/19] ILP32 for ARM64 Zhangjian (Bamvor)
2015-11-23 16:49 ` Andreas Schwab
2015-12-03 17:59 ` Catalin Marinas
2015-12-04 15:35 ` Yury Norov
2015-12-04 17:18 ` Catalin Marinas
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