Re: [Qemu-devel] [PATCH] linux-user/syscall.c: Notice about lock bitmask translation for fcntl

[Chen Gang <chengang@emindsoft.com.cn>]

On 2015年12月18日 17:41, Laurent Vivier wrote:
> 
> 
> Le 18/12/2015 07:51, Chen Gang a écrit :
>>
>> I found this issue during my working time, it is about sw_64 (almost the
>> same as alpha) host running i386 wine programs.
>>
>> I also found another issue, but I am not quite sure whether it is worth
>> enough for our upstream: The related fix patch is below, which will let
>> the initialization slower, but for most archs, they have no this issue.
>>
>>     linux-user/mmap.c: Always zero MAP_ANONYMOUS memory in target_mmap()
>>     
>>     In some architectures, they have no policy to zero MAP_ANONYMOUS memory,
>>     which will cause issue for qemu target_mmap.
>>     
>>     Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
>>
>> diff --git a/linux-user/mmap.c b/linux-user/mmap.c
>> index 7b459d5..9c9152d 100644
>> --- a/linux-user/mmap.c
>> +++ b/linux-user/mmap.c
>> @@ -567,6 +567,10 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
>>      printf("\n");
>>  #endif
>>      tb_invalidate_phys_range(start, start + len);
>> +    if ((prot & PROT_WRITE) && (flags & MAP_ANONYMOUS)
>> +        && ((flags & MAP_PRIVATE) || (fd == -1))) {
>> +        memset(g2h(start), 0, len);
>> +    }
> 
> IMHO, their kernel needs a fix, mmap(2):
> 
> MAP_ANONYMOUS
>         The mapping is not backed by any file; its contents are initial‐
>         ized to zero.
> 

OK, Thanks.


-- 
Chen Gang (陈刚)

Open, share, and attitude like air, water, and life which God blessed