Nick Piggin <[email protected]> wrote:
>
> On Fri, Apr 21, 2006 at 12:17:12AM -0700, Andrew Morton wrote:
> > Nick Piggin <[email protected]> wrote:
> > >
> > > Add a remap_vmalloc_range and get rid of as many remap_pfn_range and
> > > vm_insert_page loops as possible.
> > >
> > > remap_vmalloc_range can do a whole lot of nice range checking even
> > > if the caller gets it wrong (which it looks like one or two do).
> > >
> > >
> > > - if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > > - if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > > - if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > > - if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
> > > - if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > > - if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > > - if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
> > > - if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
> > > - if (remap_pfn_range(vma, start, page + vma->vm_pgoff,
> > > - PAGE_SIZE, vma->vm_page_prot))
> > > - if (remap_pfn_range(vma, addr, pfn, PAGE_SIZE, PAGE_READONLY))
> >
> > You've removed the ability for the caller to set the pte protections - it
> > now always uses vma->vm_page_prot.
> >
> > please explain...
>
> They should use vma->vm_page_prot?
>
> The callers affected are the PAGE_SHARED ones (the others are unchanged).
> Isn't it correct to provide readonly mappings if userspace asks for it?
Dunno. I assume perfmon was using PAGE_READONLY because it doesn't want
userspace altering the memory. One would think that this should be
enforced at mmap()-time, and that mprotect() might be able to override it
anyway. But I haven't looked that closely.
First impression is that there's some potential for breaking stuff in all
this - convince me otherwise ;)
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