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

[Kevin Brodsky]

Please ignore this whole series, I sent the wrong version... Sorry for the noise! 
I'll be sending the right version momentarily.

Kevin

On 08/09/16 14:53, Kevin Brodsky wrote:
> Hi,
>
> This series adds support for a compat (AArch32) vDSO, providing two
> userspace functionalities to compat processes:
>
> * Time "virtual" syscalls (gettimeofday and clock_gettime). The
>    implementation is an adaptation of the arm vDSO (vgettimeofday.c),
>    using the same the data page as 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 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.
>
>
> The last patch requires my Makefile fix [1] to apply. I pushed the
> series on top of this patch on pdsw-git:
>
>    git at pdsw-git.cambridge.arm.com:users/kevbro01/linux compat-vdso
>
> 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.
>
> Thanks,
> Kevin
>
> [1]: "arm64: fix vdso-offsets.h dependency"
>       http://lists.infradead.org/pipermail/linux-arm-kernel/2016-April/422307.html
>
> 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             |  13 +-
>   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               |   9 +-
>   arch/arm64/kernel/asm-offsets.c          |  13 ++
>   arch/arm64/kernel/signal32.c             |  61 ++-----
>   arch/arm64/kernel/vdso.c                 | 196 +++++++++++++--------
>   arch/arm64/kernel/vdso32/Makefile        | 120 +++++++++++++
>   arch/arm64/kernel/vdso32/sigreturn.S     |  82 +++++++++
>   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, 876 insertions(+), 133 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
>