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Re: [PATCH v1.1 0/7] aarch64: Allow overriding HWCAP_CPUID feature check
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Thu, 11 May 2017 12:38:07 -0300
- Subject: Re: [PATCH v1.1 0/7] aarch64: Allow overriding HWCAP_CPUID feature check
- Authentication-results: sourceware.org; auth=none
- References: <1494514306-4167-1-git-send-email-siddhesh@sourceware.org>
On 11/05/2017 11:51, Siddhesh Poyarekar wrote:
> 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.
>
> Update from last set:
>
> - Fixed up removal of dl_hwcap_mask in one case I missed during rebase.
It has fixed x86 build, however I am still seeing a runtime failure with:
FAIL: elf/tst-env-setuid
Which basically does:
$ env GCONV_PATH=/home/azanella/Projects/glibc/build/x86_64-linux-gnu/iconvdata LOCPATH=/home/azanella/Projects/glibc/build/x86_64-linux-gnu/localedata LC_ALL=C MALLOC_CHECK_=2 MALLOC_MMAP_THRESHOLD_=4096 LD_HWCAP_MASK=0xffffffff /home/azanella/Projects/glibc/build/x86_64-linux-gnu/elf/tst-env-setuid
: error while loading shared libraries: cannot create capability list: Cannot allocate memory
It is failing on elf/dl-hwcaps.c:
201 /* The result structure: we use a very compressed way to store the
202 various combinations of capability names. */
203 *sz = 1 << cnt;
204 result = (struct r_strlenpair *) malloc (*sz * sizeof (*result) + total);
205 if (result == NULL)
206 _dl_signal_error (ENOMEM, NULL, NULL,
207 N_("cannot create capability list"));
With a total value being way too large. I am still digesting why exactly
this value is being too large.
>
> Siddhesh
>
>
> Siddhesh Poyarekar (7):
> 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 | 13 ++-
> 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/cpu-features.c | 4 +
> sysdeps/x86/libc-start.c | 23 +---
> 16 files changed, 192 insertions(+), 124 deletions(-)
>