Re: [PATCH 10/12] kexec: arrange for paddr_vmcoreinfo_note() to return phys_addr_t

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Fri, Apr 29, 2016 at 08:36:43PM +0530, Pratyush Anand wrote:
> On Thu, Apr 28, 2016 at 2:58 PM, Russell King
> <rmk+kernel@arm.linux.org.uk> wrote:
> > diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
> > index 152da4a48867..9f1920d2d0c6 100644
> > --- a/kernel/ksysfs.c
> > +++ b/kernel/ksysfs.c
> > @@ -128,8 +128,8 @@ KERNEL_ATTR_RW(kexec_crash_size);
> >  static ssize_t vmcoreinfo_show(struct kobject *kobj,
> >                                struct kobj_attribute *attr, char *buf)
> >  {
> > -       return sprintf(buf, "%lx %x\n",
> > -                      paddr_vmcoreinfo_note(),
> > +       phys_addr_t vmcore_base = paddr_vmcoreinfo_note();
> > +       return sprintf(buf, "%pa %x\n", &vmcore_base,
> 
> Why do we pass &vmcore_base? Shouldn't it be vmcore_base?

You seem to not know what the "%pa" format string means.

%p always takes a _pointer_ as per C standard, so the printf argument
must be a pointer.  However, the kernel format strings are extended
with additional suffixes - in this case 'a', which means that we want
to print the contents of a _pointer_ to a phys_addr_t.

Full details in Documentation/printk-formats.txt in the kernel.

The code above is correct.

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