Re: [Qemu-devel] [PATCH v2] mips: Decide to map PAGE_EXEC in map_address

[Jakub Jermar]

Hi,

On 4/23/19 4:58 PM, Jakub Jermar wrote:
> Hi Philippe!
> 
> On 4/23/19 3:48 PM, Philippe Mathieu-Daudé wrote:
>> Hi Jakub,
>>
>> On 4/23/19 1:00 PM, Jakub Jermář wrote:
>>> This commit addresses QEMU Bug #1825311:
>>>
>>>   mips_cpu_handle_mmu_fault renders all accessed pages executable
>>>
>>> It allows finer-grained control over whether the accessed page should be
>>> executable by moving the decision to the underlying map_address
>>> function, which has more information for this.
>>>
>>> As a result, pages that have the XI bit set in the TLB and are accessed
>>> for read/write, don't suddenly end up being executable.
>>>
>>
>> Fixes: https://bugs.launchpad.net/qemu/+bug/1825311
>>
>>> Signed-off-by: Jakub Jermář <address@hidden>
>>> ---
>>>  target/mips/helper.c | 17 ++++++++++-------
>>>  1 file changed, 10 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/target/mips/helper.c b/target/mips/helper.c
>>> index c44cdca3b5..132d073fbe 100644
>>> --- a/target/mips/helper.c
>>> +++ b/target/mips/helper.c
>>> @@ -43,7 +43,7 @@ int no_mmu_map_address (CPUMIPSState *env, hwaddr 
>>> *physical, int *prot,
>>>                          target_ulong address, int rw, int access_type)
>>>  {
>>>      *physical = address;
>>> -    *prot = PAGE_READ | PAGE_WRITE;
>>> +    *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
>>>      return TLBRET_MATCH;
>>>  }
>>>  
>>> @@ -61,7 +61,7 @@ int fixed_mmu_map_address (CPUMIPSState *env, hwaddr 
>>> *physical, int *prot,
>>>      else
>>>          *physical = address;
>>>  
>>> -    *prot = PAGE_READ | PAGE_WRITE;
>>> +    *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
>>>      return TLBRET_MATCH;
>>>  }
>>>  
>>> @@ -101,6 +101,9 @@ int r4k_map_address (CPUMIPSState *env, hwaddr 
>>> *physical, int *prot,
>>>                  *prot = PAGE_READ;
>>>                  if (n ? tlb->D1 : tlb->D0)
>>>                      *prot |= PAGE_WRITE;
>>> +                if (!(n ? tlb->XI1 : tlb->XI0)) {
>>> +                    *prot |= PAGE_EXEC;
>>> +                }
>>
>> This was indeed missed in commit 2fb58b73746e.
>>
>>>                  return TLBRET_MATCH;
>>>              }
>>>              return TLBRET_DIRTY;
>>> @@ -182,7 +185,7 @@ static int get_seg_physical_address(CPUMIPSState *env, 
>>> hwaddr *physical,
>>>      } else {
>>>          /* The segment is unmapped */
>>>          *physical = physical_base | (real_address & segmask);
>>> -        *prot = PAGE_READ | PAGE_WRITE;
>>> +        *prot = PAGE_READ | PAGE_WRITE | PAGE_EXEC;
>>>          return TLBRET_MATCH;
>>>      }
>>>  }
>>> @@ -913,8 +916,8 @@ int mips_cpu_handle_mmu_fault(CPUState *cs, vaddr 
>>> address, int size, int rw,
>>>      }
>>>      if (ret == TLBRET_MATCH) {
>>>          tlb_set_page(cs, address & TARGET_PAGE_MASK,
>>> -                     physical & TARGET_PAGE_MASK, prot | PAGE_EXEC,
>>> -                     mmu_idx, TARGET_PAGE_SIZE);
>>> +                     physical & TARGET_PAGE_MASK, prot, mmu_idx,
>>> +                     TARGET_PAGE_SIZE);
>>>          ret = 0;
>>>      } else if (ret < 0)
>>>  #endif
>>> @@ -936,8 +939,8 @@ int mips_cpu_handle_mmu_fault(CPUState *cs, vaddr 
>>> address, int size, int rw,
>>>                                             address, rw, access_type, 
>>> mmu_idx);
>>>                  if (ret == TLBRET_MATCH) {
>>>                      tlb_set_page(cs, address & TARGET_PAGE_MASK,
>>> -                            physical & TARGET_PAGE_MASK, prot | PAGE_EXEC,
>>> -                            mmu_idx, TARGET_PAGE_SIZE);
>>> +                            physical & TARGET_PAGE_MASK, prot, mmu_idx,
>>> +                            TARGET_PAGE_SIZE);
>>>                      ret = 0;
>>>                      return ret;
>>>                  }
>>>
>>
>> Your patch looks correct, but I'd like to test it.
>> Do you have a reproducer?
>> Can you describe the command line you used?
> 
> I've just attached a reproducer image and script to the bug. It's a
> 32-bit little-endian test binary running on top of the L4Re microkernel.
> Let me know if you also need a 64-bit version.
> 
> I tested both 32 and 64-bit versions of the reproducer and also checked
> to see that the the other images I have lying around here (Linux 2.6.32
> big endian and HelenOS master little-endian, both 32-bit for 4Kc)
> continue to run without regressions.
> 
> Best regards,
> Jakub

(ping)

Is there anything else I can do to help to get this merged?

https://patchew.org/QEMU/address@hidden/

Thanks,
Jakub

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