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Date: Mon, 5 Feb 2024 04:48:08 -0800
From: Kees Cook <keescook@chromium.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Florian Weimer <fweimer@redhat.com>, linux-kernel@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-api@vger.kernel.org,
	x86@kernel.org, Eric Biederman <ebiederm@xmission.com>,
	linux-mm@kvack.org
Subject: Re: [PATCH v4] ELF: AT_PAGE_SHIFT_MASK -- supply userspace with
 available page shifts
Message-ID: <202402050445.0331B94A73@keescook>
References: <ecb049aa-bcac-45c7-bbb1-4612d094935a@p183>
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In-Reply-To: <ecb049aa-bcac-45c7-bbb1-4612d094935a@p183>

On Mon, Feb 05, 2024 at 12:51:43PM +0300, Alexey Dobriyan wrote:
> +#define ARCH_AT_PAGE_SHIFT_MASK					\
> +	do {							\
> +		u32 val = 1 << 12;				\
> +		if (boot_cpu_has(X86_FEATURE_PSE)) {		\
> +			val |= 1 << 21;				\
> +		}						\
> +		if (boot_cpu_has(X86_FEATURE_GBPAGES)) {	\
> +			val |= 1 << 30;				\
> +		}						\

Can we use something besides literal "12", "21", and "30" values here?

-Kees

-- 
Kees Cook