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Message-ID: <556F0ACA.6020402@ptsecurity.com>
Date: Wed, 3 Jun 2015 17:10:18 +0300
From: Alexander Popov <alpopov@...ecurity.com>
To: Andrey Ryabinin <a.ryabinin@...sung.com>,
Ingo Molnar <mingo@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.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
On 03.06.2015 11:44, Andrey Ryabinin wrote:
> On 06/03/2015 10:44 AM, Ingo Molnar wrote:
>>
>> * 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.
>>
>
> Agreed. Eventually, with the patch bellow, we could get rid of the second
> kasan_map_early_shadow(init_level4_pgt) call in x86_64_start_kernel().
> Make it static, and call it from kasan_early_init() only.
>
> ------------------------------------------------------
> From: Andrey Ryabinin <a.ryabinin@...sung.com>
> Subject: [PATCH] x86_64: remove not needed clear_page for init_level4_page
>
> Commit 8170e6bed465 ("x86, 64bit: Use a #PF handler to materialize
> early mappings on demand") introduced clear_page(init_level4_pgt);
> call in x86_64_start_kernel(). However, this clear_page is useless
> because init_level4_page already filled with zeroes in head_64.S
>
> Commit message in 8170e6bed465 says that this clear_page() was
> dropped in v7, but it accidentally reappeared in later versions
> of that patchset.
>
> Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
> ---
> arch/x86/kernel/head64.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 5a46681..6a6eefd 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -177,7 +177,6 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
> */
> load_ucode_bsp();
>
> - clear_page(init_level4_pgt);
> /* set init_level4_pgt kernel high mapping*/
> init_level4_pgt[511] = early_level4_pgt[511];
>
Hello Ingo and Andrey.
Should I make a "patch series" containing Andrey's patch and the 5'th version
of my patch or just include changes from Andrey's patch into mine?
Best regards,
Alexander
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