[RFC PATCH 0/8] arm64: Add a compat vDSO

[Dmitry Safonov]

2016-09-08 17:00 GMT+03:00 Kevin Brodsky <kevin.brodsky at arm.com>:
> Hi,
>
> This series adds support for a compat (AArch32) vDSO, providing two
> userspace functionalities to compat processes:
>
> * "Virtual" time syscalls (gettimeofday and clock_gettime). The
>   implementation is an adaptation of the arm vDSO (vgettimeofday.c),
>   sharing the data page with the 64-bit vDSO.
>
> * sigreturn trampolines, following the example of the 64-bit vDSO
>   (sigreturn.S), but slightly more complicated because we provide A32
>   and T32 variants for both sigreturn and rt_sigreturn.
>
> The first point brings the performance improvement expected of a vDSO,
> by implementing time syscalls directly in userspace. The second point
> allows us to get rid of the compat vector page, at the expense of the
> kuser helpers (this is one reason for not enabling the compat vDSO by
> default).
>
> Unfortunately, this time we cannot escape using a 32-bit toolchain. To
> build the compat VDSO, CONFIG_COMPAT_VDSO must be set *and*
> CROSS_COMPILE_ARM32 must be defined to the prefix of a 32-bit compiler.
> Failure to do so will not prevent building the kernel, but a warning
> will be printed and the compat vDSO will not be built.
>
> I have only tested the series with a 64-bit userspace (+ 32-bit glibc).
> Testing it with a 32-bit userspace would be very welcome.

Hi, what's up with these patches, are you gonna resend them or prepare
a new version?

> Thanks,
> Kevin
>
> Kevin Brodsky (8):
>   arm64: Refactor vDSO setup
>   arm64: compat: Add time-related syscall numbers
>   arm64: compat: Expose offset to registers in sigframes
>   arm64: compat: Add a 32-bit vDSO
>   arm64: compat: 32-bit vDSO setup
>   arm64: elf: Set AT_SYSINFO_EHDR in compat processes
>   arm64: compat: Use vDSO sigreturn trampolines if available
>   arm64: Wire up and expose the new compat vDSO
>
>  arch/arm64/Kconfig                       |  20 +++
>  arch/arm64/Makefile                      |  20 ++-
>  arch/arm64/include/asm/elf.h             |  15 +-
>  arch/arm64/include/asm/signal32.h        |  46 +++++
>  arch/arm64/include/asm/unistd.h          |   2 +
>  arch/arm64/include/asm/vdso.h            |   3 +
>  arch/arm64/kernel/Makefile               |   8 +-
>  arch/arm64/kernel/asm-offsets.c          |  13 ++
>  arch/arm64/kernel/signal32.c             |  61 ++-----
>  arch/arm64/kernel/vdso.c                 | 198 ++++++++++++---------
>  arch/arm64/kernel/vdso32/Makefile        | 121 +++++++++++++
>  arch/arm64/kernel/vdso32/sigreturn.S     |  86 +++++++++
>  arch/arm64/kernel/vdso32/vdso.S          |  32 ++++
>  arch/arm64/kernel/vdso32/vdso.lds.S      |  98 +++++++++++
>  arch/arm64/kernel/vdso32/vgettimeofday.c | 294 +++++++++++++++++++++++++++++++
>  15 files changed, 883 insertions(+), 134 deletions(-)
>  create mode 100644 arch/arm64/kernel/vdso32/Makefile
>  create mode 100644 arch/arm64/kernel/vdso32/sigreturn.S
>  create mode 100644 arch/arm64/kernel/vdso32/vdso.S
>  create mode 100644 arch/arm64/kernel/vdso32/vdso.lds.S
>  create mode 100644 arch/arm64/kernel/vdso32/vgettimeofday.c

-- 
             Dmitry