Re: [PATCH v1.1 0/7] aarch64: Allow overriding HWCAP_CPUID feature check

[Siddhesh Poyarekar <siddhesh at gotplt dot org>]

On Thursday 11 May 2017 09:08 PM, Adhemerval Zanella wrote:
> 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.

Heh, I think I know what is going on.  There are two places where it
fails with the exact same error, and both can be reached when there are
too many bits set in DL_HWCAP_IMPORTANT. Setting LD_HWCAP_MASK to
0xffffffff in the test case is crossing both limits I assume.  The fact
that I don't see the failure and you do seems to be because of malloc
not failing on my system and failing on yours.  This may be due to
differences in overcommit behaviour.

Fix is to reduce the number of bits set in the test, so really just this
(untested) patch should do, can you please confirm?

Thanks,
Siddhesh

ChangeLog:

	* elf/Makefile (tst-env-setuid-ENV): Set LD_HWCAP_MASK to 0x1.

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