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Re: [PATCH v5 00/23] ILP32 for ARM64

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> On Oct 1, 2015, at 2:29 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> 
>> On Thursday 01 October 2015 22:15:20 Yury Norov wrote:
>> 
>> Regarding time_t, it, of course, doesn't takes much time to make it
>> 32-bit, but I think 64 bit is better because of Y2038. X32 and mips
>> n32 has time_t 64-bit (and ppc, not sure), and that's OK for them.
> 
> I'm pretty sure that n32 has 32-bit time_t, and we know that it still
> causes real-world problems on x32: socket timestamps, v4l, alsa and
> other subsystems all have bugs in this area that are hard to fix.
> 
>> That's OK for BSD as well. The objection may come from users of ABI,
>> complaining portability problems, but I found no such complains in
>> public discussions.
>> 
>> Nevertheless, as I told, I do not see any problem to rework time_t.
>> But some arguments supporting this decision are appreciated.
>> 
>> The downside of 32 bit time_t is that we still face Y2038 problem,
>> but that's the other story fixing it.
> 
> The main reason for 32-bit time_t is compatibility with existing
> ioctls (also getsockopts and some others), and having a sane way
> for fixing them. We cannot change compat_time_t to be 64-bit
> without breaking arm32 compat mode, and we can't use the native
> 64-bit ioctl implementation on ARM64/ILP32 because that breaks
> all interfaces that pass 'long' or a pointer.
> 
> This means drivers that currently pass a time_t (or timeval, timespec
> etc) need to not only have a compat_ioctl handler to convert it,
> they also need to check whether which of the two compat modes they
> are talking to. This is a mess to add (I know, because I'm working
> on this for y2038 compliance for normal 32-bit mode), and making
> the two behave differently makes it even harder to get right for
> all cases.
> 
>> __kernel_long_t is the same. Now it's 64 bits length. Compatibility
>> may suffer, but, again, there're no complains, and in long run it
>> looks better.
> 
> __kernel_long_t isn't actually used that much, and rarely used in
> places where it matters. The idea was to be able to reuse the
> native syscalls rather than the compat syscall calls, but that
> comes with the downside of defining the ABI in a way that is
> incompatible with all other 32-bit user space.
> 
> Having a 64-bit __kernel_off_t is similar to the 64-bit time_t:
> a good idea in principle, but it breaks device drivers that
> expect user space to pass 32-bit arguments. For any interface
> that really needs 64-bit data, we have to fix it for all
> 32-bit architectures, and we're better off avoiding special
> cases.

Ok, we will rewrite these patches using 32bit time_t and 32bit off_t and redo the toolchain support for them.  Note this is going back to the abi I had originally done when I submitted my original version when it was asked to change time_t to be 64bit. 

Thanks,
Andrew


> 
>    Arnd
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[PATCH v5 00/23] ILP32 for ARM64 Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 08/23] arm64:ilp32: use 64bit syscall-names for ILP32 when passing 64bit registers Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 17/23] arm64:ilp32: add vdso-ilp32 and use for signal return Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
    Re: [PATCH v5 17/23] arm64:ilp32: add vdso-ilp32 and use for signal  return Nathan Lynch <Nathan_Lynch@mentor.com> - 2015-09-30 06:10 +0200
      Re: [PATCH v5 17/23] arm64:ilp32: add vdso-ilp32 and use for signal  return Yury Norov <ynorov@caviumnetworks.com> - 2015-10-01 21:50 +0200
        Re: [PATCH v5 17/23] arm64:ilp32: add vdso-ilp32 and use for signal return "Dr. Philipp Tomsich" <philipp.tomsich@theobroma-systems.com> - 2015-10-01 22:40 +0200
  [PATCH v5 09/23] arm64:ilp32: use non-compat syscall names for ILP32 as for LP64 Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 23/23] arm64:ilp32: add ARM64_ILP32 to Kconfig Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 13/23] arm64:ilp32: share HWCAP between LP64 and ILP32 Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 04/23] arm64: change some CONFIG_COMPAT over to use CONFIG_AARCH32_EL0 instead Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
    Re: [PATCH v5 04/23] arm64: change some CONFIG_COMPAT over to use  CONFIG_AARCH32_EL0 instead kbuild test robot <lkp@intel.com> - 2015-09-30 05:40 +0200
  [PATCH v5 02/23] arm64: ensure the kernel is compiled for LP64 Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 16/23] arm64: add support for starting ILP32 (ELFCLASS32) binaries Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 15/23] arm64:ilp32: support core dump generation for ILP32 Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 05/23] arm64:ilp32: expose 'kernel_long' as 'long long' for ILP32 Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
  [PATCH v5 10/23] arm64: introduce is_a32_task and is_a32_thread (for AArch32 compat) Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:20 +0200
    Re: [PATCH v5 10/23] arm64: introduce is_a32_task and is_a32_thread  (for AArch32 compat) kbuild test robot <lkp@intel.com> - 2015-09-30 05:50 +0200
  [PATCH v5 22/23] aarch64: ilp32: msgrcv, msgsnd handlers Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:30 +0200
  [PATCH v5 20/23] arm64:ilp32: use the native siginfo instead of the compat siginfo Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:30 +0200
  [PATCH v5 07/23] arm64:ilp32: share signal structures between ILP32 and LP64 ABIs Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:30 +0200
  [PATCH v5 19/23] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:30 +0200
  [PATCH v5 21/23] arm64:ilp32: change COMPAT_ELF_PLATFORM to report a a subplatform for ILP32 Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:30 +0200
  [PATCH v5 18/23] ptrace: Allow compat to use the native siginfo Yury Norov <ynorov@caviumnetworks.com> - 2015-09-30 00:30 +0200
  Re: [PATCH v5 00/23] ILP32 for ARM64 Catalin Marinas <catalin.marinas@arm.com> - 2015-09-30 12:20 +0200
    Re: [PATCH v5 00/23] ILP32 for ARM64 Mark Brown <broonie@kernel.org> - 2015-09-30 18:50 +0200
      Re: [PATCH v5 00/23] ILP32 for ARM64 Catalin Marinas <catalin.marinas@arm.com> - 2015-10-01 13:20 +0200
        Re: [PATCH v5 00/23] ILP32 for ARM64 Mark Brown <broonie@kernel.org> - 2015-10-01 13:40 +0200
          Re: [PATCH v5 00/23] ILP32 for ARM64 Andrey Konovalov <andrey.konovalov@linaro.org> - 2015-10-01 18:50 +0200
      Re: [PATCH v5 00/23] ILP32 for ARM64 Yury Norov <ynorov@caviumnetworks.com> - 2015-10-01 21:40 +0200
    Re: [PATCH v5 00/23] ILP32 for ARM64 Yury Norov <ynorov@caviumnetworks.com> - 2015-10-01 21:20 +0200
      Re: [PATCH v5 00/23] ILP32 for ARM64 Arnd Bergmann <arnd@arndb.de> - 2015-10-01 23:30 +0200
        Re: [PATCH v5 00/23] ILP32 for ARM64 "Pinski, Andrew" <Andrew.Pinski@caviumnetworks.com> - 2015-10-01 23:50 +0200
          Re: [PATCH v5 00/23] ILP32 for ARM64 Catalin Marinas <catalin.marinas@arm.com> - 2015-10-02 11:40 +0200
            Re: [PATCH v5 00/23] ILP32 for ARM64 "Kapoor, Prasun" <Prasun.Kapoor@caviumnetworks.com> - 2015-10-03 05:00 +0200
              Re: [PATCH v5 00/23] ILP32 for ARM64 Catalin Marinas <catalin.marinas@arm.com> - 2015-10-05 18:00 +0200
                Re: [PATCH v5 00/23] ILP32 for ARM64 "Pinski, Andrew" <Andrew.Pinski@caviumnetworks.com> - 2015-10-05 23:10 +0200
          Re: [PATCH v5 00/23] ILP32 for ARM64 Yury Norov <ynorov@caviumnetworks.com> - 2015-10-05 21:20 +0200

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