On Wed, 18 May 2016, Andrey Ryabinin wrote:
> 2016-05-18 17:40 GMT+03:00 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>:
>
> > All right, I'm getting very tired of all these bug reports. Besides,
> > Andrey has a point: Unless you're Linus, arguing against the C standard
> > is futile. (Even though the language dialect used in the kernel is not
> > standard C.)
> >
> > Does this patch make UBSAN happy? The runtime overhead is minimal.
> >
>
> It does. However, you could fool ubsan way more easy:
> u32 __iomem *hostpc_reg = ehci->regs->hostpc +
> (wIndex & 0xff) - 1;
Really? That's a lot simpler. But will it also fool gcc? That is,
will it prevent gcc from optimizing away the !wIndex tests below?
How about this patch?
Alan Stern
Index: usb-4.x/drivers/usb/host/ehci-hub.c
===================================================================
--- usb-4.x.orig/drivers/usb/host/ehci-hub.c
+++ usb-4.x/drivers/usb/host/ehci-hub.c
@@ -872,9 +872,10 @@ int ehci_hub_control(
) {
struct ehci_hcd *ehci = hcd_to_ehci (hcd);
int ports = HCS_N_PORTS (ehci->hcs_params);
- u32 __iomem *status_reg = &ehci->regs->port_status[
- (wIndex & 0xff) - 1];
- u32 __iomem *hostpc_reg = &ehci->regs->hostpc[(wIndex & 0xff) - 1];
+ u32 __iomem *status_reg = ehci->regs->port_status +
+ ((wIndex & 0xff) - 1);
+ u32 __iomem *hostpc_reg = ehci->regs->hostpc +
+ ((wIndex & 0xff) - 1);
u32 temp, temp1, status;
unsigned long flags;
int retval = 0;
--
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