Re: [PATCH 09/24] linux-user: Implement MAP_FIXED_NOREPLACE

[Richard Henderson <richard.henderson@linaro.org>]

On 7/3/23 11:51, Alex Bennée wrote:
>> @@ -544,7 +544,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
>>           }
>>       }
>>   
>> -    if (!(flags & MAP_FIXED)) {
>> +    if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
>>           unsigned long host_start;
>>           void *p;
>>   
...
>> @@ -608,7 +615,8 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
>>                   goto fail;
>>               }
>>               retaddr = target_mmap(start, len, target_prot | PROT_WRITE,
>> -                                  MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
>> +                                  (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))
>> +                                  | MAP_PRIVATE | MAP_ANONYMOUS,
> 
> I thought we always MAP_FIXED because we've already jumped the hoops to
> work out where in the memory space this allocation is going.

We have not, no.  Not here, anyway.

> IOW I thought the MAP_FIXED here was an internal QEMU implementation
> details rather than reflecting the guests wishes.

As I read it, MAP_FIXED was here because we'd already checked for it in the IF that I 
retained above.  But now we're checking for 2 things, and must pass that on to the recursion.


r~