On Wed, Apr 26, 2017 at 5:02 PM, Nadav Amit <[email protected]> wrote: > And besides, it looks as if the code was meant to flush the entire > TLB in some cases (e.g., if pgd_none_or_clear_bad() is true). > > On 4/26/17, 4:56 PM, "Nadav Amit" <[email protected]> wrote: > > It may be benign, but I don’t think that flushing the TLB without > holding the ptl or the mmap_sem (for no apparent reason) is a good > practice. > > On 4/22/17, 12:01 AM, "Andy Lutomirski" <[email protected]> wrote: > > mark_screen_rdonly() is the last remaining caller of flush_tlb(). > flush_tlb_mm_range() is potentially faster and isn't obsolete. > > Compile-tested only because I don't know whether software that uses > this mechanism even exists. > > Cc: Rik van Riel <[email protected]> > Cc: Dave Hansen <[email protected]> > Cc: Nadav Amit <[email protected]> > Cc: Michal Hocko <[email protected]> > Cc: Sasha Levin <[email protected]> > Cc: Andrew Morton <[email protected]> > Signed-off-by: Andy Lutomirski <[email protected]> > --- > arch/x86/kernel/vm86_32.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c > index 23ee89ce59a9..3eda76b3c835 100644 > --- a/arch/x86/kernel/vm86_32.c > +++ b/arch/x86/kernel/vm86_32.c > @@ -193,7 +193,7 @@ static void mark_screen_rdonly(struct mm_struct > *mm) > pte_unmap_unlock(pte, ptl); > out: > up_write(&mm->mmap_sem); > - flush_tlb(); > + flush_tlb_mm_range(mm, 0xA0000, 0xA0000 + 32*PAGE_SIZE, 0UL); > } >
Those should probably be pgd_none(), not pgd_none_or_clear_bad(). But this whole function is just garbage. It mucks with page protections without even looking up the VMA. What happens if the pages are file-backed? How about chardevs? I'd like to delete it. Stas, do you know if there's any code at all that uses VM86_SCREEN_BITMAP? Some Googling didn't turn any up at all.
