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Re: [PATCH v1] memory: assert MemoryRegionOps callbacks are defined
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH v1] memory: assert MemoryRegionOps callbacks are defined |
Date: |
Thu, 18 Jun 2020 16:52:03 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 |
On 6/18/20 3:12 PM, Alex Bennée wrote:
>
> P J P <ppandit@redhat.com> writes:
>
>> From: Prasad J Pandit <pjp@fedoraproject.org>
>>
>> When registering a MemoryRegionOps object, assert that its
>> read/write callback methods are defined. This avoids potential
>> guest crash via a NULL pointer dereference.
>>
>> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
>> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
>> ---
>> memory.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> Update v1: add assert while registering MemoryRegionOps
>> -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg05187.html
>>
>> diff --git a/memory.c b/memory.c
>> index 91ceaf9fcf..6e94fd5958 100644
>> --- a/memory.c
>> +++ b/memory.c
>> @@ -1495,6 +1495,9 @@ void memory_region_init_io(MemoryRegion *mr,
>> const char *name,
>> uint64_t size)
>> {
>> + assert(ops);
>> + assert(ops->read);
>> + assert(ops->write);
>
> If you look at memory_region_dispatch_write you can see that
> mr->ops->write being empty is acceptable because it implies
> mr->ops->write_with_attrs is set instead. I think the same is true for
> read so I think you need something more like:
>
> assert(ops->read || ops->read_with_attrs);
> assert(ops->write || ops->write_with_attrs);
>
>
>> memory_region_init(mr, owner, name, size);
>> mr->ops = ops ? ops : &unassigned_mem_ops;
>> mr->opaque = opaque;
>> @@ -1674,6 +1677,8 @@ void
>> memory_region_init_rom_device_nomigrate(MemoryRegion *mr,
>> {
>> Error *err = NULL;
>> assert(ops);
>> + assert(ops->read);
>> + assert(ops->write);
>
> Do ROM devices need a ->write function?
This is how you put the device in I/O mode, isn't it?
>
> Also doesn't this break a load of running stuff without fixes for all
> the various missing bits? How far does make check-acceptance get?
>
>> memory_region_init(mr, owner, name, size);
>> mr->ops = ops;
>> mr->opaque = opaque;
>
>
Re: [PATCH v1] memory: assert MemoryRegionOps callbacks are defined, no-reply, 2020/06/18