Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

From	Arnd Bergmann <arnd@arndb.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it
Date	2015-12-23 22:50 +0100
Message-ID	<qIZsd-6sP-3@gated-at.bofh.it> (permalink)
References	<qG5DP-1iE-3@gated-at.bofh.it> <qIhhw-3ZI-17@gated-at.bofh.it> <qIWul-4Io-5@gated-at.bofh.it>
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On Wednesday 23 December 2015, Yury Norov wrote:
> On Mon, Dec 21, 2015 at 11:31:57PM +0100, Arnd Bergmann wrote:
> > On Tuesday 15 December 2015, Yury Norov wrote:
> > > +
> > > +#define compat_sys_open_by_handle_at   sys_open_by_handle_at
> > > +#define compat_sys_openat              sys_openat
> > > +
> > 
> > One more thing I just remembered: I think we want this behavior for all new
> > 32-bit architectures, it was a bug to call compat_sys_openat for the generic
> > syscall table, as we don't support 32-bit off_t.
> > 
> > Could you split this out into a separate patch that does these changes:
> > 
> > - change the default asm-generic/unistd.h to use sys_openat/sys_open_by_handle_at
> > - change tile to override those two to keep the current (suboptimal) behavior
> > - change the force_o_largefile() definition so it defaults to true for all future
> >   architectures. The easiest way is probably to add a Kconfig symbol for this
> >   that gets selected by all 32-bit architectures, so we can use
> > 
> > #define force_o_largefile() ((BITS_PER_LONG != 32) || !IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T))
> > 
> 
> Hi Arnd,
> 
> First two items are OK. The last one... Do you need it to remove
> compat_sys_openat and compat_sys_open_by_handle_at?

It's needed so all future architectures get it right.

> The patch that introduces CONFIG_ARCH_32BIT_OFF_T will affect all
> architectures, and so I need to get ack from each maintainer. 

Just post it to the linux-arch and linux-kernel mailing lists.
You are not actually changing behavior, so my Ack should be sufficient
here, as long as we make sure we handle all architectures the same
way.

> I will also have to ask them to test that change, because I have no
> access to all the hardware. (Even with QEMU, I cannot test them all.)
> I think the only man who is able to success with it is Linus :)...
> 
> Some arches has more than one compat mode. For example ARM64: aarch32
> requires this config enabled, but ilp32 needs it disabled. Now we can
> enable both features, but this will make them mutual exclusive. We can
> instead (un)define __ARCH_WANT_32BIT_OFF_T for each ABI of each platform,
> but it's even more work. And we'd think twice how to do it because
> it's not mechanical work. For example, on aarch64 it will look like:
> 
>         #define __ARCH_WANT_32BIT_OFF_T is_a32_compat_task()
> 
> I have no idea how it will look on x86 or ppc.

arm64 is not affected at all, because it's a 64-bit-only architecture
and force_o_largefile() already returns true here.

> In your previous email (Nov 18) you write that tile is the only user
> of asm-generic/unistd.h that needs compat behaviour. If so, why not
> just to turn it around, as you initially suggested, and fix tile. And
> do nothing with force_o_largefile()?

The first two of the three changes I listed above are for the
compat ABI, and there it is enough to change tile.

The third change has nothing to do with compat mode, but is about
native 32-bit architectures. However, we should change both in sync,
so the next architecture that gets added with both native 32-bit
mode and compat 32-bit mode on a 64-bit kernel behaves the same
way for all 32-bit user space, independent of what the kernel does.

We can have two separate patches to clarify that these don't have to
be done atomically, but we need to do both for consistency.
 
> By the way, is there a comprehensive list of linux platforms/abis, or
> at least ones that use asm-generic/unistd.h?

Just the source code.

	Arnd
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Thread

[RFC3 PATCH v6 00/20] ILP32 for ARM64 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
  [PATCH v6 10/20] arm64:ilp32 use the native LP64 'start_thread' for ILP32 threads Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 10/20] arm64:ilp32 use the native LP64 'start_thread' for ILP32 threads Arnd Bergmann <arnd@arndb.de> - 2015-12-16 17:00 +0100
      Re: [PATCH v6 10/20] arm64:ilp32 use the native LP64 'start_thread'  for ILP32 threads Yury Norov <ynorov@caviumnetworks.com> - 2015-12-18 15:00 +0100
  [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Arnd Bergmann <arnd@arndb.de> - 2015-12-16 17:10 +0100
    Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate  table (in entry.S) to use it Catalin Marinas <catalin.marinas@arm.com> - 2015-12-17 19:30 +0100
      Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Arnd Bergmann <arnd@arndb.de> - 2015-12-17 21:20 +0100
        Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate  table (in entry.S) to use it Andrew Pinski <pinskia@gmail.com> - 2015-12-17 21:20 +0100
          Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Arnd Bergmann <arnd@arndb.de> - 2015-12-17 22:00 +0100
          Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate  table (in entry.S) to use it Catalin Marinas <catalin.marinas@arm.com> - 2015-12-18 12:50 +0100
            Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Arnd Bergmann <arnd@arndb.de> - 2015-12-18 14:00 +0100
              Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate  table (in entry.S) to use it Catalin Marinas <catalin.marinas@arm.com> - 2015-12-21 19:40 +0100
                Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Arnd Bergmann <arnd@arndb.de> - 2015-12-21 23:30 +0100
              Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it "Dr. Philipp Tomsich" <philipp.tomsich@theobroma-systems.com> - 2015-12-21 19:50 +0100
                Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Arnd Bergmann <arnd@arndb.de> - 2015-12-21 23:20 +0100
    Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Arnd Bergmann <arnd@arndb.de> - 2015-12-21 23:40 +0100
      Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate  table (in entry.S) to use it Yury Norov <ynorov@caviumnetworks.com> - 2015-12-23 19:40 +0100
        Re: [PATCH v6 12/20] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Arnd Bergmann <arnd@arndb.de> - 2015-12-23 22:50 +0100
  [PATCH v6 02/20] arm64: ensure the kernel is compiled for LP64 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
  [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to ilp32 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to ilp32 Andreas Schwab <schwab@suse.de> - 2015-12-17 15:40 +0100
      Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to  ilp32 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-18 15:00 +0100
    Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to  ilp32 Catalin Marinas <catalin.marinas@arm.com> - 2015-12-22 13:30 +0100
      Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to ilp32 Arnd Bergmann <arnd@arndb.de> - 2015-12-22 22:50 +0100
        Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to  ilp32 Catalin Marinas <catalin.marinas@arm.com> - 2015-12-23 14:40 +0100
          Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to ilp32 Arnd Bergmann <arnd@arndb.de> - 2015-12-23 21:50 +0100
            Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to  ilp32 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-30 18:30 +0100
              Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to ilp32 Arnd Bergmann <arnd@arndb.de> - 2015-12-30 23:40 +0100
      Re: [PATCH v6 13/20] arm64: ilp32: share aarch32 syscall wrappers to  ilp32 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-23 05:30 +0100
  [PATCH v6 08/20] arm64: ilp32: add is_ilp32_compat_{task,thread} and TIF_32BIT_AARCH64 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 08/20] arm64: ilp32: add is_ilp32_compat_{task,  thread} and TIF_32BIT_AARCH64 Catalin Marinas <catalin.marinas@arm.com> - 2015-12-17 12:50 +0100
      Re: [PATCH v6 08/20] arm64: ilp32: add is_ilp32_compat_{task,  thread} and TIF_32BIT_AARCH64 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-18 15:20 +0100
        Re: [PATCH v6 08/20] arm64: ilp32: add is_ilp32_compat_{task,  thread} and TIF_32BIT_AARCH64 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-18 15:50 +0100
          Re: [PATCH v6 08/20] arm64: ilp32: add is_ilp32_compat_{task,  thread} and TIF_32BIT_AARCH64 Catalin Marinas <catalin.marinas@arm.com> - 2015-12-21 18:50 +0100
  [PATCH v6 04/20] arm64: change some CONFIG_COMPAT over to use CONFIG_AARCH32_EL0 instead Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 04/20] arm64: change some CONFIG_COMPAT over to use  CONFIG_AARCH32_EL0 instead Yury Norov <ynorov@caviumnetworks.com> - 2015-12-23 15:20 +0100
    > diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile Bamvor Jian Zhang <bamvor.zhangjian@linaro.org> - 2015-12-28 09:50 +0100
      Re: [PATCH v6 04/20] arm64: change some CONFIG_COMPAT over to use  CONFIG_AARCH32_EL0 instead "Zhangjian (Bamvor)" <bamvor.zhangjian@huawei.com> - 2015-12-28 10:10 +0100
        Re: [PATCH v6 04/20] arm64: change some CONFIG_COMPAT over to use  CONFIG_AARCH32_EL0 instead Yury Norov <ynorov@caviumnetworks.com> - 2015-12-29 13:40 +0100
          [PATCH] arm64: compat: fix wrong dependency Bamvor Jian Zhang <bamvor.zhangjian@linaro.org> - 2015-12-29 16:10 +0100
        Re: [PATCH v6 04/20] arm64: change some CONFIG_COMPAT over to use  CONFIG_AARCH32_EL0 instead Yury Norov <ynorov@caviumnetworks.com> - 2015-12-29 14:20 +0100
  [PATCH v6 01/20] arm64: ilp32: add documentation on the ILP32 ABI for ARM64 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
  [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32 Arnd Bergmann <arnd@arndb.de> - 2015-12-16 17:00 +0100
      Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32 Catalin Marinas <catalin.marinas@arm.com> - 2015-12-16 18:00 +0100
        Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32 Catalin Marinas <catalin.marinas@arm.com> - 2015-12-16 18:20 +0100
          Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32 Arnd Bergmann <arnd@arndb.de> - 2015-12-16 20:20 +0100
            Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32 Catalin Marinas <catalin.marinas@arm.com> - 2015-12-17 12:00 +0100
              Re: [PATCH v6 09/20] arm64:ilp32: share HWCAP between LP64 and ILP32 Arnd Bergmann <arnd@arndb.de> - 2015-12-17 15:00 +0100
  [PATCH v6 07/20] arm64: introduce is_a32_task and is_a32_thread (for AArch32 compat) Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 07/20] arm64: introduce is_a32_task and is_a32_thread  (for AArch32 compat) Catalin Marinas <catalin.marinas@arm.com> - 2015-12-17 12:40 +0100
  [PATCH v6 05/20] arm64:uapi: set __BITS_PER_LONG correctly for ILP32 and LP64 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
  [PATCH v6 11/20] arm64:ilp32: support core dump generation for ILP32 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 11/20] arm64:ilp32: support core dump generation for  ILP32 Catalin Marinas <catalin.marinas@arm.com> - 2015-12-17 15:10 +0100
  [PATCH v6 15/20] arm64: signal: move ilp32 and lp64 common code to separated file Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 22:50 +0100
    Re: [PATCH v6 15/20] arm64: signal: move ilp32 and lp64 common code to separated file Arnd Bergmann <arnd@arndb.de> - 2015-12-16 17:10 +0100
      Re: [PATCH v6 15/20] arm64: signal: move ilp32 and lp64 common code  to separated file Yury Norov <ynorov@caviumnetworks.com> - 2015-12-18 14:50 +0100
        Re: [PATCH v6 15/20] arm64: signal: move ilp32 and lp64 common code to separated file Arnd Bergmann <arnd@arndb.de> - 2015-12-18 15:20 +0100
    Re: [PATCH v6 15/20] arm64: signal: move ilp32 and lp64 common code  to separated file Catalin Marinas <catalin.marinas@arm.com> - 2015-12-22 18:20 +0100
  [PATCH v6 17/20] arm64: ilp32: introduce ilp32-specific handlers for sigframe Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 23:00 +0100
    Re: [PATCH v6 17/20] arm64: ilp32: introduce ilp32-specific handlers  for sigframe Catalin Marinas <catalin.marinas@arm.com> - 2015-12-22 18:20 +0100
  [PATCH v6 18/20] arm64:ilp32: add vdso-ilp32 and use for signal return Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 23:00 +0100
  [PATCH v6 19/20] arm64:ilp32: change COMPAT_ELF_PLATFORM to report a a subplatform for ILP32 Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 23:00 +0100
  [PATCH v6 20/20] arm64:ilp32: add ARM64_ILP32 to Kconfig Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 23:00 +0100
  [PATCH v6 16/20] arm64: signal32: move ilp32 and aarch32 common code to separated file Yury Norov <ynorov@caviumnetworks.com> - 2015-12-15 23:00 +0100
    Re: [PATCH v6 16/20] arm64: signal32: move ilp32 and aarch32 common  code to separated file Catalin Marinas <catalin.marinas@arm.com> - 2015-12-22 15:30 +0100
  Re: [RFC3 PATCH v6 00/20] ILP32 for ARM64 Arnd Bergmann <arnd@arndb.de> - 2015-12-16 17:30 +0100

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