Re: [RFC6 PATCH v6 00/21] ILP32 for ARM64

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

On 05/04/16 23:08, Yury Norov wrote:
> This version is rebased on kernel v4.6-rc2, and has fixes in signal subsystem.
> It works with updated glibc [1] (though very draft), and tested with LTP.
> 
> It was tested on QEMU and ThunderX machines. No major difference found.
> This is RFC because ILP32 is not tested in big-endian mode.
> 
>  v3: https://lkml.org/lkml/2014/9/3/704
>  v4: https://lkml.org/lkml/2015/4/13/691
>  v5: https://lkml.org/lkml/2015/9/29/911
> 
>  v6:
>  - time_t, __kenel_off_t and other types turned to be 32-bit
>    for compatibility reasons (after v5 discussion);

i added libc-alpha to cc, the thread is at
https://lkml.org/lkml/2016/4/5/872
or http://thread.gmane.org/gmane.linux.kernel.cross-arch/31449

the kernel position seems to be that the aarch64 ilp32 syscall abi
will follow regular 32bit abis (apart from signal context and ptrace
related things and syscalls will take 64bit arguments).

i think the reasoning is that this allows legacy (non-64bit-safe)
software to use this abi on aarch64 without trouble.

i think this design should be ok for glibc.

there are some interop issues between processes following different abis
(e.g. shared mutexes, abi specific file formats, lib paths,..) which apply,
but i assume it is no different from existing 32bit vs 64bit issues.

the 32bit time_t and off_t are ugly and i wonder if 32bit __kernel_off_t
is really necessary. (i don't see where that is changed: it is supposed
to be __kernel_long_t which is 64bit).

i think even legacy software should be able to deal with 64bit off_t,
so we could avoid having two sets of filesystem apis or is 64bit-only
off_t more work to do in linux/glibc?

>  - related changes applied to ILP32 syscall table and handlers;
>  - ILP32 VDSO code excluded. It's not mandatory, and caused questions
>    during review process. We definitely make sure we will follow up
>    with a VDSO later on because it is needed for performance reasons;
>  - fixed build issues with different combinations of AARCH32 / ILP32
>    enabling in config;
>  - ILP32 TLS bug fixed;
>  - entry32-common.S introduced to hold wrappers needed for both ILP32
>    and AARCH32_EL0;
>  - documentation updated according to latest changes;
>  - rebased to the current head;
>  - coding style re-checked;
>  - ILP32 syscall table turned around.
> 
>    rfc3:
>  - all structures and system calls are just like AARCH32 ones now. with 2
>    exceptions: syscalls that take 64-bit parameter in 2 32-bit regosters
>    are replaced with LP64 version; struct rt_sigframe is constructed both
>    from LP64 and AARCH32 fields to be consistent with AARCH64 register set;
>  - documentation rewritten accordingly;
>  - common code for all 3 ABIs is moved to separated files for easy use,
>    new headers and objects are introduced, incl: is_compat.h, thread_bits.h,
>    signal_common.h, signal32_common.h.
>  - ILP32 VDSO code restored, Nathans comments are addressed;
>  - patch "arm64: ilp32: force IPC_64 in msgctl, shmctl, semctl" removed, as
>    Arnd suggested general solution for IPC_64 problem.
> 
>    rfc4:
>  - sys_ilp32.c syscall list is fixed according to comments;
>  - binfmt_elf32.c and binfmt_ilp32.c are introduced to host the code handling
>    corresponding formats;
>  - statfs64, fstsatfs64 and mmap wrappers are removed;
>  - rebased on v4.4-rc8 + http://www.spinics.net/lists/kernel/msg2151759.html
> 
>  rfc5:
>  - addressed rfc4 comments;
>  - turned s390 compat wrappers to be generic and applied it to arm64/ilp32.
>    Heiko Carsten and Martin Schwidefsky added to CC as s390 maintainers.
> 
>  rfc6:
>  - glibc follows new ABI, [1];
>  - significant rework for signal subsystem (patches 21, 23) - struct ucontext
>    is now corresponds user representation;
>  - compat wrappers and 32-bit off_t patchsets are joined with this patchset,
>    as for now ilp32 is the only user for them;
>  - moved to kernel v4.6-rc2;
>  - few minor bugfixes.
> 
> [1] https://github.com/norov/glibc/tree/new-api
> 
> Andrew Pinski (7):
>   arm64: ensure the kernel is compiled for LP64
>   arm64: rename COMPAT to AARCH32_EL0 in Kconfig
>   arm64: change some CONFIG_COMPAT over to use CONFIG_AARCH32_EL0
>     instead
>   arm64:uapi: set __BITS_PER_LONG correctly for ILP32 and LP64
>   arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use
>     it
>   arm64: ilp32: introduce ilp32-specific handlers for sigframe and
>     ucontext
>   arm64:ilp32: add ARM64_ILP32 to Kconfig
> 
> Bamvor Jian Zhang (1):
>   arm64: compat: change config dependences to aarch32
> 
> Philipp Tomsich (1):
>   arm64:ilp32: add vdso-ilp32 and use for signal return
> 
> Yury Norov (16):
>   all: syscall wrappers: add documentation
>   all: introduce COMPAT_WRAPPER option and enable it for s390
>   all: s390: move wrapper infrastructure to generic headers
>   all: s390: move compat_wrappers.c from arch/s390/kernel to kernel/
>   all: wrap needed syscalls in generic unistd
>   compat ABI: use non-compat openat and open_by_handle_at variants
>   32-bit ABI: introduce ARCH_32BIT_OFF_T config option
>   arm64: ilp32: add documentation on the ILP32 ABI for ARM64
>   thread: move thread bits accessors to separated file
>   arm64: introduce is_a32_task and is_a32_thread (for AArch32 compat)
>   arm64: ilp32: add is_ilp32_compat_{task,thread} and TIF_32BIT_AARCH64
>   arm64: introduce binfmt_elf32.c
>   arm64: ilp32: introduce binfmt_ilp32.c
>   arm64: ptrace: handle ptrace_request differently for aarch32 and ilp32
>   arm64: signal: share lp64 signal routines to ilp32
>   arm64: signal32: move ilp32 and aarch32 common code to separated file
> 
>  Documentation/adding-syscalls.txt             |  32 +++
>  Documentation/arm64/ilp32.txt                 |  13 ++
>  arch/Kconfig                                  |   8 +
>  arch/arc/Kconfig                              |   1 +
>  arch/arm/Kconfig                              |   1 +
>  arch/arm64/Kconfig                            |  17 +-
>  arch/arm64/Makefile                           |   5 +
>  arch/arm64/include/asm/compat.h               |  19 +-
>  arch/arm64/include/asm/elf.h                  |  35 +---
>  arch/arm64/include/asm/fpsimd.h               |   2 +-
>  arch/arm64/include/asm/ftrace.h               |   2 +-
>  arch/arm64/include/asm/hwcap.h                |   6 +-
>  arch/arm64/include/asm/is_compat.h            |  84 ++++++++
>  arch/arm64/include/asm/memory.h               |   3 +-
>  arch/arm64/include/asm/processor.h            |  11 +-
>  arch/arm64/include/asm/ptrace.h               |   2 +-
>  arch/arm64/include/asm/signal32.h             |   6 +-
>  arch/arm64/include/asm/signal32_common.h      |  25 +++
>  arch/arm64/include/asm/signal_common.h        |  33 +++
>  arch/arm64/include/asm/signal_ilp32.h         |  34 ++++
>  arch/arm64/include/asm/syscall.h              |   2 +-
>  arch/arm64/include/asm/thread_info.h          |   3 +-
>  arch/arm64/include/asm/unistd.h               |  11 +-
>  arch/arm64/include/asm/unistd32.h             |   2 +-
>  arch/arm64/include/asm/vdso.h                 |   6 +
>  arch/arm64/include/uapi/asm/bitsperlong.h     |   9 +-
>  arch/arm64/kernel/Makefile                    |  12 +-
>  arch/arm64/kernel/asm-offsets.c               |   2 +-
>  arch/arm64/kernel/binfmt_elf32.c              |  33 +++
>  arch/arm64/kernel/binfmt_ilp32.c              |  91 +++++++++
>  arch/arm64/kernel/cpufeature.c                |   8 +-
>  arch/arm64/kernel/cpuinfo.c                   |   4 +-
>  arch/arm64/kernel/entry.S                     |  18 +-
>  arch/arm64/kernel/entry_ilp32.S               |  23 +++
>  arch/arm64/kernel/head.S                      |   2 +-
>  arch/arm64/kernel/hw_breakpoint.c             |  10 +-
>  arch/arm64/kernel/perf_regs.c                 |   2 +-
>  arch/arm64/kernel/process.c                   |   7 +-
>  arch/arm64/kernel/ptrace.c                    |  67 ++++++-
>  arch/arm64/kernel/signal.c                    | 100 ++++++----
>  arch/arm64/kernel/signal32.c                  |  85 --------
>  arch/arm64/kernel/signal32_common.c           | 115 +++++++++++
>  arch/arm64/kernel/signal_ilp32.c              | 192 ++++++++++++++++++
>  arch/arm64/kernel/sys32.c                     |   1 +
>  arch/arm64/kernel/sys_ilp32.c                 |  68 +++++++
>  arch/arm64/kernel/traps.c                     |   5 +-
>  arch/arm64/kernel/vdso-ilp32/.gitignore       |   2 +
>  arch/arm64/kernel/vdso-ilp32/Makefile         |  72 +++++++
>  arch/arm64/kernel/vdso-ilp32/vdso-ilp32.S     |  33 +++
>  arch/arm64/kernel/vdso-ilp32/vdso-ilp32.lds.S |  95 +++++++++
>  arch/arm64/kernel/vdso.c                      |  65 ++++--
>  arch/blackfin/Kconfig                         |   1 +
>  arch/cris/Kconfig                             |   1 +
>  arch/frv/Kconfig                              |   1 +
>  arch/h8300/Kconfig                            |   1 +
>  arch/hexagon/Kconfig                          |   1 +
>  arch/m32r/Kconfig                             |   1 +
>  arch/m68k/Kconfig                             |   1 +
>  arch/metag/Kconfig                            |   1 +
>  arch/microblaze/Kconfig                       |   1 +
>  arch/mips/Kconfig                             |   1 +
>  arch/mn10300/Kconfig                          |   1 +
>  arch/nios2/Kconfig                            |   1 +
>  arch/openrisc/Kconfig                         |   1 +
>  arch/parisc/Kconfig                           |   1 +
>  arch/powerpc/Kconfig                          |   1 +
>  arch/s390/Kconfig                             |   1 +
>  arch/s390/include/asm/compat.h                |  17 +-
>  arch/s390/kernel/Makefile                     |   2 +-
>  arch/s390/kernel/compat_linux.c               |   4 +
>  arch/s390/kernel/compat_wrapper.c             | 180 -----------------
>  arch/score/Kconfig                            |   1 +
>  arch/sh/Kconfig                               |   1 +
>  arch/sparc/Kconfig                            |   1 +
>  arch/tile/Kconfig                             |   1 +
>  arch/tile/kernel/compat.c                     |   3 +
>  arch/unicore32/Kconfig                        |   1 +
>  arch/x86/Kconfig                              |   1 +
>  arch/x86/um/Kconfig                           |   1 +
>  arch/xtensa/Kconfig                           |   1 +
>  drivers/clocksource/arm_arch_timer.c          |   2 +-
>  include/linux/compat.h                        | 277 ++++++++++++++++++++++++++
>  include/linux/fcntl.h                         |   2 +-
>  include/linux/ptrace.h                        |   6 +
>  include/linux/syscalls.h                      |  57 +-----
>  include/linux/syscalls_structs.h              |  60 ++++++
>  include/linux/thread_bits.h                   |  55 +++++
>  include/linux/thread_info.h                   |  44 +---
>  include/uapi/asm-generic/unistd.h             | 231 ++++++++++-----------
>  kernel/Makefile                               |   1 +
>  kernel/compat_wrapper.c                       | 175 ++++++++++++++++
>  kernel/ptrace.c                               |  10 +-
>  92 files changed, 1997 insertions(+), 637 deletions(-)
>  create mode 100644 Documentation/arm64/ilp32.txt
>  create mode 100644 arch/arm64/include/asm/is_compat.h
>  create mode 100644 arch/arm64/include/asm/signal32_common.h
>  create mode 100644 arch/arm64/include/asm/signal_common.h
>  create mode 100644 arch/arm64/include/asm/signal_ilp32.h
>  create mode 100644 arch/arm64/kernel/binfmt_elf32.c
>  create mode 100644 arch/arm64/kernel/binfmt_ilp32.c
>  create mode 100644 arch/arm64/kernel/entry_ilp32.S
>  create mode 100644 arch/arm64/kernel/signal32_common.c
>  create mode 100644 arch/arm64/kernel/signal_ilp32.c
>  create mode 100644 arch/arm64/kernel/sys_ilp32.c
>  create mode 100644 arch/arm64/kernel/vdso-ilp32/.gitignore
>  create mode 100644 arch/arm64/kernel/vdso-ilp32/Makefile
>  create mode 100644 arch/arm64/kernel/vdso-ilp32/vdso-ilp32.S
>  create mode 100644 arch/arm64/kernel/vdso-ilp32/vdso-ilp32.lds.S
>  delete mode 100644 arch/s390/kernel/compat_wrapper.c
>  create mode 100644 include/linux/syscalls_structs.h
>  create mode 100644 include/linux/thread_bits.h
>  create mode 100644 kernel/compat_wrapper.c
>