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Re: [Qemu-devel] [PATCH v2] mips: Decide to map PAGE_EXEC in map_address
From: |
Jakub Jermar |
Subject: |
Re: [Qemu-devel] [PATCH v2] mips: Decide to map PAGE_EXEC in map_address |
Date: |
Thu, 16 May 2019 15:10:25 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 |
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?
Thanks,
Jakub
>
> Thanks,
> Jakub
>
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