[PATCH 0/8] aarch64: Allow overriding HWCAP_CPUID feature check

[Siddhesh Poyarekar <siddhesh at sourceware dot org>]

Hi,

This set of patches moves LD_HWCAP_MASK environment variable to tunables
as glibc.tune.hwcap_mask and gets all of its uses using tunables instead.
This is needed to override the HWCAP_CPUID bit for aarch64 to allow
disabling of the multiarch MIDR check if needed.

The patchset enhances the tunables framework further for this and as a
result, the tunable_list is now laid out in the .relro section so that it
cannot be modified after relocations have been processed.  Also, tunables
can now be set to have a default value, and can also take unsigned int64
values.

I have done a sanity test of this patchset on aarch64 and seems to work
just fine.  x86 would perhaps benefit from a similar delaying of
cpu_features reading for static binaries so that they can be overriden by
tunables in future (an aarch64 patch coming up; spoiler alert: the tunable
name proposed is glibc.tune.mcpu) but I haven't done that at this time
since it is not necessary for this patchset.

Siddhesh

Siddhesh Poyarekar (8):
  tunables: Make tunable_list relro
  tunables: Specify a default value for tunables
  tunables: Add support for tunables of uint64_t type
  tunables: Add hooks to get and update tunables
  tunables: Add LD_HWCAP_MASK to tunables
  tunables: Use glibc.tune.hwcap_mask tunable instead of _dl_hwcap_mask
  Delay initialization of CPU features struct in static binaries
  aarch64: Allow overriding HWCAP_CPUID feature check using HWCAP_MASK

 csu/libc-start.c                               |   6 ++
 elf/dl-cache.c                                 |   9 +-
 elf/dl-hwcaps.c                                |  15 ++-
 elf/dl-support.c                               |   2 +
 elf/dl-tunable-types.h                         |   1 +
 elf/dl-tunables.c                              | 142 ++++++++++++++-----------
 elf/dl-tunables.h                              |  43 +++++---
 elf/dl-tunables.list                           |   7 ++
 elf/rtld.c                                     |   4 +
 scripts/gen-tunables.awk                       |  15 ++-
 sysdeps/generic/ldsodefs.h                     |   2 +
 sysdeps/sparc/sparc32/dl-machine.h             |   7 +-
 sysdeps/unix/sysv/linux/aarch64/cpu-features.c |  15 ++-
 sysdeps/unix/sysv/linux/aarch64/libc-start.c   |  23 +---
 sysdeps/x86/libc-start.c                       |  23 +---
 15 files changed, 189 insertions(+), 125 deletions(-)

-- 
2.9.3