Re: [Qemu-devel] [PATCH] lsi53c895a: check script ram address value

[Peter Maydell]

On 6 November 2018 at 12:38, li qiang <address@hidden> wrote:
>
> 在 2018/11/6 20:28, Paolo Bonzini 写道:
>> On 06/11/2018 13:27, li qiang wrote:
>>> The addr is 0~0x1fff, but when addr is at the near the end ,for example
>>> 0x1fffe, the add>>2 can be 2047
>>>
>>> and as script_ram is a uint32_t and so s->script_ram[addr >> 2] can read
>>> out of the script_ram.
>> How so?  s->script_ram has size 2048, it's okay to access it at 2047.
>
> Oh, right.
>
>   I'm confused by the script_ram, it's not byte array.

Incidentally, I think the read and write functions here
would be somewhat clearer written as

static void lsi_ram_write(void *opaque, hwaddr addr,
                          uint64_t val, unsigned size)
{
    LSIState *s = opaque;
    void *p = ((void *)s->script_ram) + addr;

    assert(addr + size <= sizeof(s->script_ram));
    stn_p(p, size, val);
}

static uint64_t lsi_ram_read(void *opaque, hwaddr addr,
                             unsigned size)
{
    LSIState *s = opaque;
    void *p = ((void *)s->script_ram) + addr;

    assert(addr + size <= sizeof(s->script_ram));
    return ldn_p(p, size);
}

thanks
-- PMM