On 2016/5/25 18:50, Catalin Marinas wrote: > On Wed, May 25, 2016 at 11:36:38AM +0800, Leizhen (ThunderTown) wrote: >> On 2016/5/25 9:20, Leizhen (ThunderTown) wrote: >>> On 2016/5/24 21:02, Catalin Marinas wrote: >>>> On Tue, May 24, 2016 at 08:19:05PM +0800, Leizhen (ThunderTown) wrote: >>>>> On 2016/5/24 19:37, Mark Rutland wrote: >>>>>> It looks like the test may be missing I-cache maintenance regardless of >>>>>> the semantics of mprotect in this case. >>>>>> >>>>>> I have not yet devled into flush_cache_range and how it is called. >>>>> >>>>> SYSCALL_DEFINE3(mprotect ---> mprotect_fixup ---> change_protection ---> >>>>> change_protection_range --> flush_cache_range >>>> >>>> The change_protection() shouldn't need to flush the caches in >>>> flush_cache_range(). The change_pte_range() function eventually ends up >>>> calling set_pte_at() which calls __sync_icache_dcache() if the mapping >>>> is executable. >>> >>> OK, I see. >>> But I'm afraid it entered the "if (pte_present(oldpte))" branch in >>> function change_pte_range. Because the test case called mmap to >>> create pte first, then called pte_modify. I will check it later. >> >> I have checked that it entered "if (pte_present(oldpte))" branch. > > This path eventually calls set_pte_at() via ptep_modify_prot_commit(). OK, I see.
> >> But I don't known why I add flush_icache_range is OK, but add >> __sync_icache_dcache have no effect. > > Do you mean you modified set_pte_at() to use flush_icache_range() Just about. I added in change_pte_range after below statement. ptent = pte_modify(ptent, newprot); > instead of __sync_icache_dcache() and it works? Yes. > > What happens is that __sync_icache_dcache() only takes care of the first > time a page is mapped in user space and flushes the caches, marking it > as "clean" (PG_dcache_clean) afterwards. Subsequent changes to this > mapping or writes to it are entirely the responsibility of the user. So > if the user plans to execute instructions, it better explicitly flush > the caches (as Mark Rutland already stated in a previous reply). > > I ran our internal LTP version yesterday and it was fine but didn't > realise that we actually patched mprotect04.c to include: > > __clear_cache((char *)func, (char *)func + page_sz); > > just after memcpy(). Yes, I aslo tried this before I sent this patch. Flush dcache in userspace or kernel can both fixs this problem. > > (we still need to investigate whether the I-cache invalidation is > actually needed in flush_cache_range() or it's just something we forgot > to remove) >