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

[Adhemerval Zanella]

On 12/05/2017 10:44, Siddhesh Poyarekar wrote:
> On Friday 12 May 2017 05:40 PM, Szabolcs Nagy wrote:
>> it seems LD_HWCAP_MASK affects ldso behaviour,
>> (some library search path is computed based on
>> "important" hwcap names)
>>
>> so it's probably not a good idea to reuse it for
>> ifunc dispatch tuning of the libc.
>>
>> (the exact semantics of the LD_HWCAP_MASK is not
>> clear to me though)
> 
> The dynamic linker is trying to allocate space for strings to describe
> the hwcaps and somehow setting hwcap_mask like that is causing it to
> allocated lots of memory.  It is a bug in the dynamic linker, not a
> problem with setting hwcap_mask.
> 
> My 'solution' of fixing the test case papered over the fact that the
> dynamic linker should not be barfing like this.  I'll work on this.
> This is unrelated to the patchset under discussion however since the
> problem should be visible even in 2.25.
> 
> Siddhesh
> 

That is my understanding as well, we should iron out the LD_HWCAP_MASK
for the possible flags values.  Answering your previous question,
on my system I am using vm.overcommit_kbytes=0 and setting LD_HWCAP_MASK
to 0x1 seems to make the test pass (since it won't try to preallocate lots
of memory).