[Barrelfish-users] Maybe a Bug of modify_flags

[Simon Peter]

Hi Jinghao,

I've compiled your code for x86-64 and ran it on QEMU. Here's the output 
I get:

pmaptest.0: begin monothelic_frame test...
kernel 0: user page fault in 'pmaptest': addr 60000000 IP 4003a0, error 0x7
kernel 0: user page fault in 'pmaptest': addr 60001000 IP 4003a0, error 0x7
pmaptest.0: array init done!
pmaptest.0: begin one_page_one_frame test...
kernel 0: user page fault in 'pmaptest': addr 68000000 IP 400560, error 0x7
kernel 0: user page fault in 'pmaptest': addr 68001000 IP 400560, error 0x7
pmaptest.0: array init done
pmaptest.0: array check done!

This seems to be working?

Simon

On 20.05.2012 16:00, jhshi at cs.hku.hk wrote:
> Here is my previous email, FYI.
>
> https://lists.inf.ethz.ch/pipermail/barrelfish-users/2012-May/000593.html
>
> Quoting jhshi at cs.hku.hk:
>
>>
>> Hi,
>>
>> For some reason, I need to work on x86_32 instead of x86_64. And I
>> found that x86_32's pmap->f.modify_flags is NYI. So I ported it from
>>   x86_64, as described by my previous email (link). But then I found
>> that the port won't work properly. Personally, I don't think the
>> problem lies in the porting but in the modify_flags itself.
>>
>> Here is my test case workflow:
>>
>> First allocate two pages using frame_alloc and map them at some
>> "safe"  virtual address as read-only using pmap->f.map. Then fill
>> the two  pages with different content. Since they are read-only,
>> page faults  will occur when filling. I catch them and map the fault
>> page as  read-write using pmap->f.modify_flags in the fault handler.
>> But then I  found that the two page's content are identical, which
>> is not supposed  to be.
>>
>> Then I found that if I allocate one frame for each page, instead of
>> one monolithic frame, everything is fine.
>>
>> I've summarized my test in the attached C file, which should be
>> compiled and run under x86_32. Apology for not being able to test it
>>   under X86_64 since I encounter some weird errors when compiling
>> arch  x86_64. But if you substitute all the X86_32 to X86_64 in the
>> test  file, it should work under x86_64 as well.
>>
>> However, if the test goes all fine under x86_64, then please give
>> some  hint about why its x86_32's port would fail.
>>
>> Thanks in advance!
>>
>> Regards,
>> Jinghao
>>
>
>
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