linux-kernel - Re: [PATCH v2 2/4] x86/xen: add basic KASAN support for PV kernel

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Date:   Fri, 17 Jan 2020 09:56:12 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Sergey Dyasli <sergey.dyasli@...rix.com>, xen-devel@...ts.xen.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        George Dunlap <george.dunlap@...rix.com>,
        Ross Lagerwall <ross.lagerwall@...rix.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 2/4] x86/xen: add basic KASAN support for PV kernel



On 1/17/20 7:58 AM, Sergey Dyasli wrote:
> --- a/arch/x86/mm/kasan_init_64.c
> +++ b/arch/x86/mm/kasan_init_64.c
> @@ -13,6 +13,9 @@
>   #include <linux/sched/task.h>
>   #include <linux/vmalloc.h>
>   
> +#include <xen/xen.h>
> +#include <xen/xen-ops.h>
> +
>   #include <asm/e820/types.h>
>   #include <asm/pgalloc.h>
>   #include <asm/tlbflush.h>
> @@ -332,6 +335,11 @@ void __init kasan_early_init(void)
>   	for (i = 0; pgtable_l5_enabled() && i < PTRS_PER_P4D; i++)
>   		kasan_early_shadow_p4d[i] = __p4d(p4d_val);
>   
> +	if (xen_pv_domain()) {
> +		pgd_t *pv_top_pgt = xen_pv_kasan_early_init();
> +		kasan_map_early_shadow(pv_top_pgt);
> +	}
> +


I'd suggest replacing this with xen_kasan_early_init() and doing 
everything, including PV check, there. This way non-Xen code won't need 
to be aware of Xen-specific details such as guest types.


>   	kasan_map_early_shadow(early_top_pgt);
>   	kasan_map_early_shadow(init_top_pgt);
>   }
> @@ -369,6 +377,8 @@ void __init kasan_init(void)
>   				__pgd(__pa(tmp_p4d_table) | _KERNPG_TABLE));
>   	}
>   
> +	xen_pv_kasan_pin_pgd(early_top_pgt);
> +

And drop "_pv" here (and below) for the same reason.

-boris

>   	load_cr3(early_top_pgt);
>   	__flush_tlb_all();
>   
> @@ -433,6 +443,8 @@ void __init kasan_init(void)
>   	load_cr3(init_top_pgt);
>   	__flush_tlb_all();
>   
> +	xen_pv_kasan_unpin_pgd(early_top_pgt);
> +
>