Re: [Qemu-devel] [PATCH] linux-user: Fix stale tbs after mmap

[Alexander Graf]

On 07.05.2012, at 13:32, Alexander Graf wrote:

> 
> On 07.05.2012, at 12:37, Peter Maydell wrote:
> 
>> On 7 May 2012 10:30, Alexander Graf <address@hidden> wrote:
>>> @@ -587,6 +587,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, 
>>> int prot,
>>>    page_dump(stdout);
>>>    printf("\n");
>>> #endif
>>> +    tb_invalidate_phys_page_range(start, start + len, 0);
>>>    mmap_unlock();
>>>    return start;
>> 
>> The comment at the top of tb_invalidate_phys_page_range() says
>> "start and end must refer to the same physical page" -- is it
>> out of date or does that not apply to user-mode?
>> 
>> Do you need to also invalidate the range on munmap() and
>> mprotect-to-not-executable in order to correctly fault on
>> the case of:
>> map something
>> execute it
>> unmap it
>> try to execute it again
>> 
>> ? (haven't tested that case but it seems like it might be an issue)
> 
> Yeah, the issue does exist:

And the below patch on top of my revised patch fixes it. The question is 
whether we still need to flush on mmap() then?


Alex

diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 3611deb..bb4e752 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -690,8 +690,10 @@ int target_munmap(abi_ulong start, abi_ulong len)
         }
     }
 
-    if (ret == 0)
+    if (ret == 0) {
         page_set_flags(start, start + len, 0);
+        tb_invalidate_phys_range(start, start + len, 0);
+    }
     mmap_unlock();
     return ret;
 }