On Wed, 2010-10-13 at 16:25 +0530, ext Varadarajan, Charulatha wrote:
>
> > -----Original Message-----
> > From: Evgeny Kuznetsov [mailto:[email protected]]
> > Sent: Wednesday, October 13, 2010 3:35 PM
> > To: [email protected]
> > Cc: [email protected]; [email protected]; linux-arm-
> > [email protected]; Balbi, Felipe; [email protected];
> > [email protected]; [email protected]; Varadarajan,
> > Charulatha; [email protected]; [email protected]
> > Subject: [PATCHv2 1/1] omap: Ptr "isr_reg" tracked as NULL was
> > dereferenced
> >
> > From: Evgeny Kuznetsov <[email protected]>
> >
> > Value of "isr_reg" pointer is depend on configuration and GPIO method.
> > Potentially it may have NULL value and it is dereferenced later
> > in code. If pointer is NULL there is some kernel issue.
>
> Can you elaborate?
"isr_reg" should not be NULL. But if it is NULL then there is kernel
bug. And WARN_ON() used to show it.
I did not see this bug, this is potentially may happen.
>
> > Warning and exit from function are added in this case.
> > Also compilation check is added for correct architecture
> > configuration.
> >
> > Signed-off-by: Evgeny Kuznetsov <[email protected]>
> > ---
> > arch/arm/plat-omap/gpio.c | 18 ++++++++++++++++++
> > 1 files changed, 18 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/arm/plat-omap/gpio.c b/arch/arm/plat-omap/gpio.c
> > index c05c653..d04913c 100644
> > --- a/arch/arm/plat-omap/gpio.c
> > +++ b/arch/arm/plat-omap/gpio.c
> > @@ -1318,6 +1318,23 @@ static void gpio_irq_handler(unsigned int irq,
> > struct irq_desc *desc)
> > if (bank->method == METHOD_GPIO_44XX)
> > isr_reg = bank->base + OMAP4_GPIO_IRQSTATUS0;
> > #endif
> > +
> > +#if !defined(CONFIG_ARCH_OMAP1) && \
> > + !defined(CONFIG_ARCH_OMAP15XX) && \
> > + !defined(CONFIG_ARCH_OMAP16XX) && \
> > + !defined(CONFIG_ARCH_OMAP730) && \
> > + !defined(CONFIG_ARCH_OMAP850) && \
> > + !defined(CONFIG_ARCH_OMAP2) && \
> > + !defined(CONFIG_ARCH_OMAP3) && \
> > + !defined(CONFIG_ARCH_OMAP4)
> > +
> > +#error "Incorrect arch configuration"
>
> This is not required. If the architecture is not one of the above
> mentioned, gpio_irq_handler() will not be used/called at all.
This could be removed.
> Also all the possible gpio methods for a given OMAP architecture are
> already considered with "#ifdef"s and (bank->method) checks in
> gpio_irq_handler().
It is not cover all cased, e.g. for OMAP4 arch:
....
#if defined(CONFIG_ARCH_OMAP4)
if (bank->method == METHOD_GPIO_44XX)
isr_reg = bank->base + OMAP4_GPIO_IRQSTATUS0;
#endif
.....
If (bank->method != METHOD_GPIO_44XX) then isr_reg will be NULL.
This should not happen, but potentially may have place.
>
> > +
> > +#endif
> > +
> > + if (WARN_ON(!isr_reg))
> > + goto exit;
>
> For the above mentioned reason, this isr_reg would be non-NULL. Have
> you observed this error anytime?
I did not see this bug, this is potentially may happen.
>
> Also, the omap-gpio code has similar code spread all over and has to be
> anyway cleaned-up. Is there any reason why gpio_irq_handler() alone is
> addressed in this patch?
Here "isr_reg" is used later in code and may cause oops if it is NULL.
>
> > +
> > while(1) {
> > u32 isr_saved, level_mask = 0;
> > u32 enabled;
> > @@ -1377,6 +1394,7 @@ static void gpio_irq_handler(unsigned int irq,
> > struct irq_desc *desc)
> > configured, we must unmask the bank interrupt only after
> > handler(s) are executed in order to avoid spurious bank
> > interrupt */
> > +exit:
> > if (!unmasked)
> > desc->chip->unmask(irq);
> >
> > --
> > 1.6.3.3
>
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