From: Catalin Marinas <catalin.marinas@arm.com>
To: David Miller <davem@davemloft.net>
Cc: arnd@arndb.de, ynorov@caviumnetworks.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-arch@vger.kernel.org, linux-s390@vger.kernel.org,
libc-alpha@sourceware.org, schwidefsky@de.ibm.com,
heiko.carstens@de.ibm.com, pinskia@gmail.com, broonie@kernel.org,
joseph@codesourcery.com,
christoph.muellner@theobroma-systems.com,
bamvor.zhangjian@huawei.com, szabolcs.nagy@arm.com,
klimov.linux@gmail.com, Nathan_Lynch@mentor.com, agraf@suse.de,
Prasun.Kapoor@caviumnetworks.com, kilobyte@angband.pl,
geert@linux-m68k.org, philipp.tomsich@theobroma-systems.com
Subject: Re: [PATCH 01/23] all: syscall wrappers: add documentation
Date: Fri, 27 May 2016 11:10:37 +0100 [thread overview]
Message-ID: <20160527101036.GC7865@e104818-lin.cambridge.arm.com> (raw)
In-Reply-To: <20160526.124344.1660236473079504674.davem@davemloft.net>
On Thu, May 26, 2016 at 12:43:44PM -0700, David Miller wrote:
> From: Catalin Marinas <catalin.marinas@arm.com>
> Date: Thu, 26 May 2016 15:20:58 +0100
>
> > We can solve (a) by adding more __SC_WRAP annotations in the generic
> > unistd.h.
> ...
>
> I really think it's much more robust to clear the tops of the registers
> by default. Then you won't be auditing constantly and adding more and
> more wrappers.
I think we could avoid adding a new __SC_WRAP by redefining __SYSCALL
for ILP32 to always invoke a wrapper. But given the wrapper overhead,
cache locality, I don't think we would notice any performance difference
in either case.
> You can't even quantify the performance gains for me in any precise
> way. Whatever you gain by avoiding the 64-bit
> decompostion/reconstitution for those few system calls with 64-bit
> registers, you are losing by calling the wrappers for more common
> system calls, more often.
I hope Yury can provide some numbers. All being equal, I would go for
the lowest code maintenance cost (which is probably less annotations and
wrappers).
> "it's more natural to pass 64-bit values in a register" is not a clear
> justification for this change.
It's more related to how we went about the ILP32 ABI. We initially asked
for a 64-bit native ABI similar to x32 until the libc-alpha community
raised some POSIX compliance issues on time structures. So we decided to
go for a 32-bit-like ABI while keeping the syscall interface close to
the AArch64/ILP32 procedure calling standard (64-bit values passed in a
single register). And now we have this discussion, revisiting this
decision again (which is perfectly fine, we better get it right before
any merging plans; thanks for your input).
--
Catalin
next prev parent reply other threads:[~2016-05-27 10:10 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-24 0:04 [PATCH v6 00/21] ILP32 for ARM64 Yury Norov
2016-05-24 0:04 ` [PATCH 01/23] all: syscall wrappers: add documentation Yury Norov
2016-05-25 19:30 ` David Miller
2016-05-25 20:03 ` Yury Norov
2016-05-25 20:21 ` David Miller
2016-05-25 20:47 ` Arnd Bergmann
2016-05-25 20:50 ` David Miller
2016-05-25 21:01 ` Arnd Bergmann
2016-05-25 21:28 ` David Miller
2016-05-26 14:20 ` Catalin Marinas
2016-05-26 14:50 ` Szabolcs Nagy
2016-05-26 15:19 ` Catalin Marinas
2016-05-26 19:43 ` David Miller
2016-05-27 10:10 ` Catalin Marinas [this message]
2016-05-26 20:48 ` Yury Norov
2016-05-26 22:29 ` Catalin Marinas
2016-05-27 0:37 ` Yury Norov
2016-05-27 6:03 ` Heiko Carstens
2016-05-27 8:42 ` Arnd Bergmann
2016-05-27 9:30 ` Catalin Marinas
2016-05-27 10:49 ` Arnd Bergmann
2016-05-27 13:04 ` Catalin Marinas
2016-05-27 16:58 ` Yury Norov
2016-05-27 17:36 ` Catalin Marinas
2016-05-27 9:01 ` Catalin Marinas
2016-06-14 23:08 ` Yury Norov
2016-05-27 5:52 ` Heiko Carstens
2016-05-24 0:04 ` [PATCH 02/23] all: introduce COMPAT_WRAPPER option and enable it for s390 Yury Norov
2016-05-24 0:04 ` [PATCH 03/23] all: s390: move wrapper infrastructure to generic headers Yury Norov
2016-05-24 0:04 ` [PATCH 04/23] all: s390: move compat_wrappers.c from arch/s390/kernel to kernel/ Yury Norov
2016-05-24 0:04 ` [PATCH 05/23] all: wrap needed syscalls in generic unistd Yury Norov
2016-05-24 0:04 ` [PATCH 06/23] compat ABI: use non-compat openat and open_by_handle_at variants Yury Norov
2016-05-24 0:04 ` [PATCH 07/23] 32-bit ABI: introduce ARCH_32BIT_OFF_T config option Yury Norov
2016-05-24 0:04 ` [PATCH 08/23] arm64: ilp32: add documentation on the ILP32 ABI for ARM64 Yury Norov
2016-05-24 0:04 ` [PATCH 09/23] arm64: ensure the kernel is compiled for LP64 Yury Norov
2016-05-24 0:04 ` [PATCH 10/23] arm64: rename COMPAT to AARCH32_EL0 in Kconfig Yury Norov
2016-05-24 0:04 ` [PATCH 11/23] arm64:uapi: set __BITS_PER_LONG correctly for ILP32 and LP64 Yury Norov
2016-05-24 0:04 ` [PATCH 12/23] thread: move thread bits accessors to separated file Yury Norov
2016-05-24 0:04 ` [PATCH 13/23] arm64: introduce is_a32_task and is_a32_thread (for AArch32 compat) Yury Norov
2016-06-12 12:21 ` Zhangjian (Bamvor)
2016-06-12 13:08 ` Zhangjian (Bamvor)
2016-06-12 17:56 ` Yury Norov
2016-05-24 0:04 ` [PATCH 14/23] arm64: ilp32: add is_ilp32_compat_{task,thread} and TIF_32BIT_AARCH64 Yury Norov
2016-05-24 0:04 ` [PATCH 15/23] arm64: introduce binfmt_elf32.c Yury Norov
2016-05-24 0:04 ` [PATCH 16/23] arm64: ilp32: introduce binfmt_ilp32.c Yury Norov
2016-05-26 13:49 ` Zhangjian (Bamvor)
2016-05-26 21:08 ` Yury Norov
2016-06-15 0:40 ` Yury Norov
2016-06-13 3:05 ` Zhangjian (Bamvor)
2016-06-13 13:22 ` Zhangjian (Bamvor)
2016-05-24 0:04 ` [PATCH 17/23] arm64: ptrace: handle ptrace_request differently for aarch32 and ilp32 Yury Norov
2016-06-08 1:34 ` zhouchengming
2016-06-08 17:00 ` Yury Norov
2016-06-25 9:36 ` zhouchengming
2016-06-25 14:15 ` Bamvor Zhang
2016-06-27 2:09 ` zhouchengming
2016-05-24 0:04 ` [PATCH 18/23] arm64: ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Yury Norov
2016-05-25 20:26 ` Arnd Bergmann
2016-05-24 0:04 ` [PATCH 19/23] arm64: signal: share lp64 signal routines to ilp32 Yury Norov
2016-05-24 0:04 ` [PATCH 20/23] arm64: signal32: move ilp32 and aarch32 common code to separated file Yury Norov
2016-05-24 0:04 ` [PATCH 21/23] arm64: ilp32: introduce ilp32-specific handlers for sigframe and ucontext Yury Norov
2016-06-04 11:34 ` Zhangjian (Bamvor)
2016-06-12 12:34 ` Zhangjian (Bamvor)
2016-06-12 13:12 ` Zhangjian (Bamvor)
2016-06-12 17:44 ` Yury Norov
2016-06-16 11:21 ` Zhangjian (Bamvor)
2016-06-12 12:39 ` Zhangjian (Bamvor)
2016-05-24 0:04 ` [PATCH 22/23] arm64:ilp32: add vdso-ilp32 and use for signal return Yury Norov
2016-05-24 0:04 ` [PATCH 23/23] arm64:ilp32: add ARM64_ILP32 to Kconfig Yury Norov
2016-05-25 10:42 ` [PATCH v6 00/21] ILP32 for ARM64 Szabolcs Nagy
2016-05-25 16:41 ` Yury Norov
2016-06-02 19:03 ` Yury Norov
2016-06-03 11:02 ` Szabolcs Nagy
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