Re: [PATCH] elf: dl-minimal malloc needs to respect fundamental alignment

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Tue, Jun 21, 2016 at 5:57 AM, Florian Weimer <fweimer@redhat.com> wrote:
> On 06/21/2016 02:54 PM, H.J. Lu wrote:
>>
>> On Tue, Jun 21, 2016 at 4:17 AM, Florian Weimer <fweimer@redhat.com>
>> wrote:
>>>
>>> If malloc is used instead of memalign for small alignments,
>>> malloc needs to provide the ABI-required alignment.
>>>
>>> 2016-06-21  Florian Weimer  <fweimer@redhat.com>
>>>
>>>         * elf/dl-minimal.c (malloc): Allocate with fundamental alignment.
>>>
>>> diff --git a/elf/dl-minimal.c b/elf/dl-minimal.c
>>> index c8a8f8d..2d7d139 100644
>>> --- a/elf/dl-minimal.c
>>> +++ b/elf/dl-minimal.c
>>> @@ -27,6 +27,7 @@
>>>  #include <sys/types.h>
>>>  #include <ldsodefs.h>
>>>  #include <_itoa.h>
>>> +#include <stdalign.h>
>>>
>>>  #include <assert.h>
>>>
>>> @@ -90,7 +91,7 @@ __libc_memalign (size_t align, size_t n)
>>>  void * weak_function
>>>  malloc (size_t n)
>>>  {
>>> -  return __libc_memalign (sizeof (double), n);
>>> +  return __libc_memalign (_Alignof (max_align_t), n);
>>>  }
>>>
>>>  /* We use this function occasionally since the real implementation may
>>
>>
>> We also have MALLOC_ALIGNMENT in malloc.  Should they be consistent?
>
>
> MALLOC_ALIGNMENT is potentially larger.  malloc/tst-malloc-thread-fail tests
> for alignment.  To my knowledge, it passes on all regularly tested
> architectures after commit dea39b13e2958a7f0e75b5594a06d97d61cc439f.
>

MALLOC_ALIGNMENT is kind of mapped to the malloc alignment of
a psABI.  Shouldn't ld.so malloc have the same alignment of libc malloc?


-- 
H.J.