Re: [PATCH v2 2/2] powerpc: Add HWCAP3/HWCAP4 data to TCB for Power Architecture.

[Peter Bergner <bergner@linux.ibm.com>]

On 12/5/23 6:38 AM, Manjunath Matti wrote:
> This patch adds a new feature for powerpc.  In order to get faster
> access to the HWCAP3/HWCAP4 masks, similar to HWCAP/HWCAP2 (i.e. for
> implementing __builtin_cpu_supports() in GCC) without the overhead of
> reading them from the auxiliary vector, we now reserve space for them
> in the TCB.
> 
> This is an ABI change for GLIBC 2.39.
> 
> Suggested-by: Peter Bergner <bergner@linux.ibm.com>
> ---
>  elf/dl-diagnostics.c                          |  2 +
>  elf/dl-support.c                              |  2 +
>  elf/elf.h                                     |  4 ++
>  sysdeps/generic/ldsodefs.h                    |  2 +
>  sysdeps/powerpc/dl-procinfo.c                 |  6 ++-
>  sysdeps/powerpc/dl-procinfo.h                 | 52 +++++++++++++------
>  sysdeps/powerpc/hwcapinfo.c                   | 11 ++--
>  sysdeps/unix/sysv/linux/dl-parse_auxv.h       |  2 +
>  sysdeps/unix/sysv/linux/dl-sysdep.c           |  2 +
>  .../unix/sysv/linux/powerpc/cpu-features.c    |  2 +
>  .../unix/sysv/linux/powerpc/cpu-features.h    |  2 +
>  sysdeps/unix/sysv/linux/powerpc/libc-start.c  |  6 +++
>  12 files changed, 74 insertions(+), 19 deletions(-)

LGTM.  The only catch is that this patch is dependent on the associated
kernel patch that adds the AT_HWCAP3 and AT_HWCAP4 getting upstream so
glibc can rely on their values.  I'm still working on upstreaming that.

Reviewed-by: Peter Bergner <bergner@linux.ibm.com>

Peter