On Tue, Sep 13, 2022, Kirill A. Shutemov wrote:
On Tue, Sep 13, 2022 at 02:53:25PM +0000, Sean Christopherson wrote:
Switching topics, what actually prevents mmapp() on the shim? I tried to follow, but I don't know these areas well enough.
It has no f_op->mmap, so mmap() will fail with -ENODEV. See do_mmap(). (I did not read the switch statement correctly at first. Note there are two 'fallthrough' there.)
Ah, validate_mmap_request(). Thought not implementing ->mmap() was the key, but couldn't find the actual check.
validate_mmap_request() is in mm/nommu.c which is not relevant for real computers.
I was talking about this check:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/m...
Hence the comment about 'fallthrough'. Thanks again!