linux-kernel - Re: [PATCH 28/43] x86/mm/kaiser: Map cpu entry area

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Date:   Sat, 25 Nov 2017 22:40:52 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ingo Molnar <mingo@...nel.org>
cc:     linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 28/43] x86/mm/kaiser: Map cpu entry area

On Fri, 24 Nov 2017, Ingo Molnar wrote:
> +void kaiser_add_mapping_cpu_entry(int cpu)
> +{
> +	kaiser_add_user_map_early(get_cpu_gdt_ro(cpu), PAGE_SIZE,
> +				  __PAGE_KERNEL_RO);
> +
> +	/* includes the entry stack */
> +	kaiser_add_user_map_early(&get_cpu_entry_area(cpu)->tss,
> +				  sizeof(get_cpu_entry_area(cpu)->tss),
> +				  __PAGE_KERNEL | _PAGE_GLOBAL);
> +
> +	/* Entry code, so needs to be EXEC */
> +	kaiser_add_user_map_early(&get_cpu_entry_area(cpu)->entry_trampoline,
> +				  sizeof(get_cpu_entry_area(cpu)->entry_trampoline),
> +				  __PAGE_KERNEL_EXEC | _PAGE_GLOBAL);

This creates a RWX mapping and wants to be __PAGE_KERNEL_RX!

Whats weird is that I saw dump_walk_pgd_level_checkwx() complain once about
that, but on the next boot it failed to detect it for whatever reason. This
needs further investigation.

Thanks,

	tglx