Re: [PATCH] cpu: microcode: replace 0 with NULL
From: Borislav Petkov
Date: Tue Nov 26 2019 - 08:53:45 EST
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@xxxxxxxxx>
> ---
> 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