linux-kernel - Re: [PATCH v4 1/1] x86_64: fix KASan shadow region page tables

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Date:	Wed, 3 Jun 2015 09:44:28 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Alexander Popov <alpopov@...ecurity.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrey Ryabinin <a.ryabinin@...sung.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Andy Lutomirski <luto@...capital.net>,
	Alexander Kuleshov <kuleshovmail@...il.com>,
	Borislav Petkov <bp@...e.de>,
	Denys Vlasenko <dvlasenk@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/1] x86_64: fix KASan shadow region page tables


* Alexander Popov <alpopov@...ecurity.com> wrote:

>  #ifdef CONFIG_KASAN
>  void __init kasan_map_early_shadow(pgd_t *pgd);
> +void __init kasan_early_init(void);
>  void __init kasan_init(void);
>  #else
>  static inline void kasan_map_early_shadow(pgd_t *pgd) { }
> +static inline void kasan_early_init(void) { }
>  static inline void kasan_init(void) { }
>  #endif
>  
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 2b55ee6..e9a84a1 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -161,11 +161,15 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
>  	/* Kill off the identity-map trampoline */
>  	reset_early_page_tables();
>  
> -	kasan_map_early_shadow(early_level4_pgt);
> -
> -	/* clear bss before set_intr_gate with early_idt_handler */
> +	/*
> +	 * Clear bss before kasan_early_init and set_intr_gate
> +	 * with early_idt_handler
> +	 */
>  	clear_bss();
>  
> +	kasan_early_init();
> +	kasan_map_early_shadow(early_level4_pgt);

So why isn't kasan_map_early_shadow() called in kasan_early_init()?

High level x86 init code should not be polluted with too many low level details.

Thanks,

	Ingo
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