linux-kernel - Re: [PATCH 01/10] x86/mm/numa: Remove uninitialized

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Message-ID: <874krr8dps.fsf@nanos.tec.linutronix.de>
Date:   Thu, 04 Jun 2020 09:58:07 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Joe Perches <joe@...ches.com>,
        Andy Whitcroft <apw@...onical.com>, x86@...nel.org,
        drbd-dev@...ts.linbit.com, linux-block@...r.kernel.org,
        b43-dev@...ts.infradead.org, netdev@...r.kernel.org,
        linux-wireless@...r.kernel.org, linux-ide@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-spi@...r.kernel.org,
        linux-mm@...ck.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH 01/10] x86/mm/numa: Remove uninitialized_var() usage

Kees Cook <keescook@...omium.org> writes:
> -#ifdef NODE_NOT_IN_PAGE_FLAGS
> -	pfn_align = node_map_pfn_alignment();
> -	if (pfn_align && pfn_align < PAGES_PER_SECTION) {
> -		printk(KERN_WARNING "Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
> -		       PFN_PHYS(pfn_align) >> 20,
> -		       PFN_PHYS(PAGES_PER_SECTION) >> 20);
> -		return -EINVAL;
> +	if (IS_ENABLED(NODE_NOT_IN_PAGE_FLAGS)) {

Hrm, clever ...

> +		unsigned long pfn_align = node_map_pfn_alignment();
> +
> +		if (pfn_align && pfn_align < PAGES_PER_SECTION) {
> +			pr_warn("Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
> +				PFN_PHYS(pfn_align) >> 20,
> +				PFN_PHYS(PAGES_PER_SECTION) >> 20);
> +			return -EINVAL;
> +		}
>  	}
> -#endif
>  	if (!numa_meminfo_cover_memory(mi))
>  		return -EINVAL;
>  
> diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h
> index 71283739ffd2..1a4cdec2bd29 100644
> --- a/include/linux/page-flags-layout.h
> +++ b/include/linux/page-flags-layout.h
> @@ -100,7 +100,7 @@
>   * there.  This includes the case where there is no node, so it is implicit.
>   */
>  #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
> -#define NODE_NOT_IN_PAGE_FLAGS
> +#define NODE_NOT_IN_PAGE_FLAGS 1

but if we ever lose the 1 then the above will silently compile the code
within the IS_ENABLED() section out.

Thanks,

        tglx