* Julia Lawall <julia.lawall@xxxxxxx> wrote:
>
>
> On Thu, 28 Dec 2017, Ingo Molnar wrote:
>
> >
> > * Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> >
> > > The annoying static analyzer follow up patches make a pain rather then
> > > fixing issues.
> > >
> > > The one done by commit 276c87054751
> > >
> > > ("x86/platform/intel-mid: Make 'bt_sfi_data' const")
> > >
> > > made an obvious regression [BugLink] since the struct bt_sfi_data used
> > > as a temporary container for important data that is used to fill
> > > 'parent' and 'name' fields in struct platform_device_info.
> > >
> > > That's why revert the commit which had been apparently done w/o reading
> > > the code.
> > >
> > > BugLink: https://github.com/andy-shev/linux/issues/20
> > > Cc: Bhumika Goyal <bhumirks@xxxxxxxxx>
> > > Cc: julia.lawall@xxxxxxx
> > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> > > ---
> > > arch/x86/platform/intel-mid/device_libs/platform_bt.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/platform/intel-mid/device_libs/platform_bt.c b/arch/x86/platform/intel-mid/device_libs/platform_bt.c
> > > index dc036e511f48..5a0483e7bf66 100644
> > > --- a/arch/x86/platform/intel-mid/device_libs/platform_bt.c
> > > +++ b/arch/x86/platform/intel-mid/device_libs/platform_bt.c
> > > @@ -60,7 +60,7 @@ static int __init tng_bt_sfi_setup(struct bt_sfi_data *ddata)
> > > return 0;
> > > }
> > >
> > > -static const struct bt_sfi_data tng_bt_sfi_data __initdata = {
> > > +static struct bt_sfi_data tng_bt_sfi_data __initdata = {
> > > .setup = tng_bt_sfi_setup,
> > > };
> >
> > This is nasty, why didn't the compiler warn about this bug?
> >
> > Normally when using a const data structure for a non-const purpose. (Unless
> > there's a type cast which loses the type - one of the many reasons why type casts
> > should be avoided.)
>
> Indeed, because there is a cast:
>
> #define ICPU(model, ddata) \
> { X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY, (kernel_ulong_t)&ddata }
>
> static const struct x86_cpu_id bt_sfi_cpu_ids[] = {
> ICPU(INTEL_FAM6_ATOM_MERRIFIELD, tng_bt_sfi_data),
> {}
> };
So the type is the following, in include/linux/mod_devicetable.h:
struct x86_cpu_id {
__u16 vendor;
__u16 family;
__u16 model;
__u16 feature; /* bit index */
kernel_ulong_t driver_data;
};
Is there a syntactic method that would allow the conversion to kernel_ulong_t, but
would preserve any const-ness?
Barring that, maybe we could convert driver_data to 'void *', fix up all users,
and not force the type - this would allow the preservation of the const attribute,
I think.
BTW., a quick grep suggests similar type casting patterns here:
arch/x86/platform/intel-mid/pwr.c: { PCI_VDEVICE(INTEL, PCI_DEVICE_ID_PENWELL), (kernel_ulong_t)&pnw_info },
arch/x86/platform/intel-mid/pwr.c: { PCI_VDEVICE(INTEL, PCI_DEVICE_ID_TANGIER), (kernel_ulong_t)&tng_info },
Thanks,
Ingo
