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    Date
    SubjectRe: UBSAN whinge in ihci-hub.c
    From
    2016-05-18 17:40 GMT+03:00 Alan Stern <stern@rowland.harvard.edu>:

    > 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;



    > 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
    > @@ -872,14 +872,17 @@ 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, *hostpc_reg;
    > u32 temp, temp1, status;
    > unsigned long flags;
    > int retval = 0;
    > unsigned selector;
    >
    > + temp = wIndex & 0xff;
    > + temp -= (temp > 0);
    > + status_reg = &ehci->regs->port_status[temp];
    > + hostpc_reg = &ehci->regs->hostpc[temp];
    > +
    > /*
    > * FIXME: support SetPortFeatures USB_PORT_FEAT_INDICATOR.
    > * HCS_INDICATOR may say we can change LEDs to off/amber/green.
    >

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