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Re: [Qemu-devel] [PATCH] memory region: check the old.mmio.read status
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH] memory region: check the old.mmio.read status |
Date: |
Wed, 12 Sep 2018 13:54:50 +0100 |
On 12 September 2018 at 13:32, Li Qiang <address@hidden> wrote:
> To avoid NULL-deref for the devices without read callbacks
>
> Signed-off-by: Li Qiang <address@hidden>
> ---
> memory.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/memory.c b/memory.c
> index 9b73892768..48d025426b 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -406,6 +406,10 @@ static MemTxResult
> memory_region_oldmmio_read_accessor(MemoryRegion *mr,
> {
> uint64_t tmp;
>
> + if (!mr->ops->old_mmio.read[ctz32(size)]) {
> + return MEMTX_DECODE_ERROR;
> + }
> +
> tmp = mr->ops->old_mmio.read[ctz32(size)](mr->opaque, addr);
> if (mr->subpage) {
> trace_memory_region_subpage_read(get_cpu_index(), mr, addr, tmp,
> size);
> --
> 2.11.0
>
There's patches on-list which drop the old_mmio field from the MemoryRegion
struct entirely, so I think this patch as it stands is obsolete.
Currently our semantics are "you must provide both read and write, even
if one of them just always returns 0 / does nothing / returns an error".
We could probably reasonably assert this at the point when the
MemoryRegionOps is registered.
thanks
-- PMM