Re: [PATCH] linux-user: Update TASK_UNMAPPED_BASE for aarch64

[Lirong Yuan]

Thanks Laurent for the prompt responses! Yes that is exactly where the value is taken from.

For anyone interested in detailed information of the change, here is the previous discussion thread:

http://patchwork.ozlabs.org/patch/1242370/

Regards,

Lirong

On Sat, Mar 14, 2020 at 10:34 AM Laurent Vivier <address@hidden> wrote:

Le 14/03/2020 à 18:01, Aleksandar Markovic a écrit :
> On Sat, Mar 14, 2020 at 11:45 AM Laurent Vivier <address@hidden> wrote:
>>
>> Le 14/03/2020 à 04:06, Aleksandar Markovic a écrit :
>>> On Fri, Mar 13, 2020 at 1:28 AM Lirong Yuan <address@hidden> wrote:
>>>>
>>>> This change updates TASK_UNMAPPED_BASE (the base address for guest programs) for aarch64. It is needed to allow qemu to work with Thread Sanitizer (TSan), which has specific boundary definitions for memory mappings on different platforms:
>>>> https://github.com/llvm/llvm-project/blob/master/compiler-rt/lib/tsan/rtl/tsan_platform.h
>>>>
>>>> Signed-off-by: Lirong Yuan <address@hidden>
>>>> ---
>>>>  linux-user/mmap.c | 4 ++++
>>>>  1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/linux-user/mmap.c b/linux-user/mmap.c
>>>> index 8685f02e7e..e378033797 100644
>>>> --- a/linux-user/mmap.c
>>>> +++ b/linux-user/mmap.c
>>>> @@ -184,7 +184,11 @@ static int mmap_frag(abi_ulong real_start,
>>>>  }
>>>>
>>>>  #if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
>>>> +#ifdef TARGET_AARCH64
>>>> +# define TASK_UNMAPPED_BASE  0x5500000000
>>>
>>> Hi, Lirong,
>>>
>>> Can you point from which line of the file you linked to did you
>>> arrive to the value 0x5500000000?
>>>
>>> Second question: What about other targets?
>>
>> Personally, I prefer to not change the value for other targets if it is
>> not required by someone that had some problems with the current value.
>>
>> It needs to be changed carefully and to be well tested after change.
>>
>
> Sure, but again, from where " 0x5500000000" comes from?

The URL is in the comment, but more precisely I guess:

 https://github.com/llvm/llvm-project/blob/master/compiler-rt/lib/tsan/rtl/tsan_platform.h#L164

Thanks,
Laurent