[PATCH] elf: Fix elf/tst-decorate-maps on aarch64 after 321e1fc73f

[Adhemerval Zanella Netto]

On 18/12/25 11:31, Dev Jain wrote:
> 
> On 18/12/25 6:38 pm, Adhemerval Zanella Netto wrote:
>>
>> On 18/12/25 10:05, Dev Jain wrote:
>>> On 18/12/25 5:56 pm, Adhemerval Zanella Netto wrote:
>>>> On 18/12/25 03:27, Dev Jain wrote:
>>>>> On 18/12/25 2:25 am, Adhemerval Zanella wrote:
>>>>>> The malloc size might be too low to trigger the mmap call on aarch64
>>>>>> with mTHP.
>>>>> Thanks, but mTHP has got nothing to do with mmap() getting triggered by
>>>>> malloc() - it is dependent on MMAP_THRESHOLD? I think we can have this
>>>>> change when we get around changing the hardcoded tunables according
>>>>> to whether THP is there by default or not - we definitely should
>>>>> increase MMAP_THRESHOLD in that case.
>>>> The test is issued with
>>>>
>>>> tst-decorate-maps-ENV = \
>>>>   GLIBC_TUNABLES=glibc.malloc.arena_max=8:glibc.malloc.mmap_threshold=1024:glibc.mem.decorate_maps=1
>>>> tst-decorate-maps-ARGS = 8
>>> So currently we do xmalloc (256 * 1024), which is greater than glibc.malloc.mmap_threshold=1024,
>>> so mmap gets triggered right? If you are trying to say that this size is not enough to back the returned
>>> memory with a 2MB THP - why is it necessary for this test?
>> It is necessary because this test check is the __set_vma_name is correctly
>> setting the mmap range used by sysmalloc_mmap. Currently after 321e1fc73f
>> on 4k page size system tst-decorate-maps fails because there is no decoration
>> found because the memory is being allocated in the sbrk range.
> 
> Ah I get you now. So basically a malloc(256KB) gets satisfied from the brk heap itself
> because it is getting extended by 2MB straightaway. Thanks.
> 
> Would you be so kind to include this in the patch description - that the test now fails
> because it expects malloc() to go to mmapped memory but post my commit will be
> satisfied from the brk heap itself? It is not obvious to figure that out!
> 

Right, are you with the following commit message:

  The test check is the __set_vma_name is correctly setting the mmap 
  range used by sysmalloc_mmap.  Currently after 321e1fc73fon 4k page s
  ize system tst-decorate-maps fails because there is no decoration
  found due the memory is being allocated in the sbrk range.