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SubjectRe: [PATCH] cpu: microcode: replace 0 with NULL
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On Tue, 2019-11-26 at 16:03 +0000, Jules Irenge wrote:
>
> On Tue, 26 Nov 2019, Borislav Petkov wrote:
>
> > On Tue, Nov 26, 2019 at 12:27:34AM +0000, Jules Irenge wrote:
> > > Replace 0 with NULL to fix sparse tool warning
> > > warning: Using plain integer as NULL pointer
> > >
> > > Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
> > > ---
> > > arch/x86/kernel/cpu/microcode/amd.c | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
> > > index a0e52bd00ecc..4934aa7c94e7 100644
> > > --- a/arch/x86/kernel/cpu/microcode/amd.c
> > > +++ b/arch/x86/kernel/cpu/microcode/amd.c
> > > @@ -418,7 +418,7 @@ static int __apply_microcode_amd(struct microcode_amd *mc)
> > > static bool
> > > apply_microcode_early_amd(u32 cpuid_1_eax, void *ucode, size_t size, bool save_patch)
> > > {
> > > - struct cont_desc desc = { 0 };
> > > + struct cont_desc desc = { NULL };
> >
> > So my gcc guy says that 0 and NULL are equivalent as designated
> > initializers in this case. And if you look at the resulting asm, it
> > doesn't change:
> >
> > # arch/x86/kernel/cpu/microcode/amd.c:421: struct cont_desc desc = { 0 };
> > movq $0, 8(%rsp) #, desc
> > movq $0, (%rsp) #, desc
> > movq $0, 16(%rsp) #, desc
> > movq $0, 24(%rsp) #, desc
> >
> > But what I'd prefer actually is, if you do them like this:
> >
> > ... = { 0, };
> >
> > because:
> >
> > 1. It is clear that the memory for the struct is being cleared
> > 2. The following ones - the ones after "," are missing too, on purpose,
> > because they're being cleared too.
> >
> > Also pls add that explanation to the commit message.
> >
> > Thx.
> >
> > --
> > Regards/Gruss,
> > Boris.
> >
> > https://people.kernel.org/tglx/notes-about-netiquette
> >
> Hi Boris,
>
> Thanks for your reply and suggestion.
>
> I am learning patching with sparse trying to solve some problems that the
> tool complains about.
>
> Sometime the tool is not always right. If I take your suggestion that I
> am about to do, sparse will however still complain.
>
> so I will suggest my change to be discarded.
>
> I will take another challenge.

This initializer should ether use named members with the appropriate
zeroing type or just use a blank {} so that regardless of type and
member order, the entire structure is zeroed.

struct cont_desc desc = {};


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