Hi. In mm/mprotect.c, there's a function, change_pte_range, that
adjusts the protection settings in a range of ptes.
I know that when a page is set up for copy on write, the pte is set
such that a write will result in a page fault. A cow page pte is set
for write protection, and the vma is marked as writable, so
vma->vm_flags & VM_WRITE would be true.
That's why I expected to see some sort of special case for this
situation in change_pte_range. I thought there would be something
like the code below:
pte_t new_pte = pte_modify(entry, newprot);
if (vma->vm_flags & VM_WRITE && !pte_write(*pte))
new_pte = pte_wrprotect(new_pte); /* for cow */
... otherwise it seems like you could ruin the cow settings when
adjusting page protections. Why isn't that needed?
Thanks.
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