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

[Aleksandar Markovic]

On May 16, 2019 3:11 PM, "Jakub Jermar" <address@hidden>
wrote:
>
> Hi,
>
> On 5/3/19 12:02 PM, Jakub Jermar wrote:
> > 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/
>
> Has anyone managed to have a look at this?
>

Sorry for the delay, but there are some unforeseen pending changes and
circumstances, and this patch will be processed later on. It won't be
forgotten, don't worry. You have to have a lot of patience in the open
source world.

Thanks again for participating, talk to you later!

Regards,
Aleksandar

> Thanks,
> Jakub
>
> >
> > Thanks,
> > Jakub
> >
>
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> Hohmuth
>