Re: [Qemu-devel] [PATCH] Bug Fix:Segmentation fault when use usb-ehci device

[Mike Qiu]

Hi all

Any comments ?

Thanks
Mike
2013/7/16 11:50, Mike Qiu wrote:
> For usb-ehci in qemu, its caps just has read() operation,
> the write() operation does not exist.
>
> This cause a Segmentation fault when use usb-ehci device in ppc64
> platform.
>
> here is gdb output:
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x3fffa7fcef20 (LWP 6793)]
> 0x00000000103f5244 in memory_region_oldmmio_write_accessor
> (opaque=0x113e9e78, addr=9, value=0x3fffa7fce088,
> size=1, shift=0, mask=255) at /home/Mike/qemu-impreza/memory.c:384
> 384  mr->ops->old_mmio.write[ctz32(size)](mr->opaque, addr, tmp);
> (gdb) p *mr->ops
> $1 = {read = @0x10716f68: 0x1020699c <ehci_caps_read>, write = 0,
>    endianness = DEVICE_LITTLE_ENDIAN, valid = {min_access_size = 1,
>    max_access_size = 4, unaligned = false, accepts = 0}, impl =
>    {min_access_size = 1, max_access_size = 1, unaligned = false},
>    old_mmio = {read = {0, 0, 0}, write = {0, 0, 0}}}
>
> Becasue function write() of mr->ops has not been implement, in
> function memory_region_dispatch_write(), it call
> oldmmio write accessor, but at the same time old_mmio still not
> been implement by default.
>
> That is the root cause of the Segmentation fault.
>
> To solve this problem, add empty function: ehci_caps_write()
>
> Signed-off-by: Mike Qiu <address@hidden>
> ---
>  hw/usb/hcd-ehci.c |    7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
> index 67e4b24..6c8a439 100644
> --- a/hw/usb/hcd-ehci.c
> +++ b/hw/usb/hcd-ehci.c
> @@ -1072,6 +1072,12 @@ static void ehci_port_write(void *ptr, hwaddr addr,
>      trace_usb_ehci_portsc_change(addr + s->portscbase, addr >> 2, *portsc, 
> old);
>  }
>
> +static void ehci_caps_write(void *ptr, hwaddr addr, uint64_t val,
> +                           unsigned size)
> +{
> +    /* nothing */
> +}
> +
>  static void ehci_opreg_write(void *ptr, hwaddr addr,
>                               uint64_t val, unsigned size)
>  {
> @@ -2380,6 +2386,7 @@ static void ehci_frame_timer(void *opaque)
>
>  static const MemoryRegionOps ehci_mmio_caps_ops = {
>      .read = ehci_caps_read,
> +    .write = ehci_caps_write,
>      .valid.min_access_size = 1,
>      .valid.max_access_size = 4,
>      .impl.min_access_size = 1,