[RFC PATCH 2/9] x86/sgx: Do not naturally align MAP_FIXED address

[Andy Lutomirski]

> On Jun 5, 2019, at 8:17 AM, Jarkko Sakkinen <jarkko.sakkinen at linux.intel.com> wrote:
> 
>> On Tue, Jun 04, 2019 at 10:10:22PM +0000, Xing, Cedric wrote:
>> A bit off topic here. This mmap()/mprotect() discussion reminds me a
>> question (guess for Jarkko): Now that vma->vm_file->private_data keeps
>> a pointer to the enclave, why do we store it again in vma->vm_private?
>> It isn't a big deal but non-NULL vm_private does prevent mprotect()
>> from merging adjacent VMAs. 
> 
> Same semantics as with a regular mmap i.e. you can close the file and
> still use the mapping.
> 
> 

The file should be properly refcounted — vm_file should not go away while it’s mapped.