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[212.159.66.145]) by smtp.gmail.com with ESMTPSA id o1sm380229wrn.84.2019.11.26.08.03.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Nov 2019 08:03:55 -0800 (PST) From: Jules Irenge X-Google-Original-From: Jules Irenge Date: Tue, 26 Nov 2019 16:03:40 +0000 (GMT) To: Borislav Petkov cc: Jules Irenge , tglx@linutronix.de, linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, mingo@redhat.com Subject: Re: [PATCH] cpu: microcode: replace 0 with NULL In-Reply-To: <20191126135330.GE31379@zn.tnic> Message-ID: References: <20191126002734.121905-1-jbi.octave@gmail.com> <20191126135330.GE31379@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > > --- > > 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. Kind regards, Jules