linux-kernel - [PATCH 07/11] Avoid cleaning the KASan shadow area's mapping table

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Date:   Wed, 11 Oct 2017 16:22:23 +0800
From:   Abbott Liu <liuwenliang@...wei.com>
To:     <linux@...linux.org.uk>, <aryabinin@...tuozzo.com>,
        <liuwenliang@...wei.com>, <afzal.mohd.ma@...il.com>,
        <f.fainelli@...il.com>, <labbott@...hat.com>,
        <kirill.shutemov@...ux.intel.com>, <mhocko@...e.com>,
        <cdall@...aro.org>, <marc.zyngier@....com>,
        <catalin.marinas@....com>, <akpm@...ux-foundation.org>,
        <mawilcox@...rosoft.com>, <tglx@...utronix.de>,
        <thgarnie@...gle.com>, <keescook@...omium.org>, <arnd@...db.de>,
        <vladimir.murzin@....com>, <tixy@...aro.org>,
        <ard.biesheuvel@...aro.org>, <robin.murphy@....com>,
        <mingo@...nel.org>, <grygorii.strashko@...aro.org>
CC:     <glider@...gle.com>, <dvyukov@...gle.com>, <opendmb@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>,
        <linux-mm@...ck.org>, <jiazhenghua@...wei.com>,
        <dylix.dailei@...wei.com>, <zengweilin@...wei.com>,
        <heshaoliang@...wei.com>
Subject: [PATCH 07/11] Avoid cleaning the KASan shadow area's mapping table

From: Andrey Ryabinin <a.ryabinin@...sung.com>

 Avoid cleaning the mapping table(page table) of KASAN shadow area.

Cc: Andrey Ryabinin <a.ryabinin@...sung.com>
Signed-off-by: Abbott Liu <liuwenliang@...wei.com>
---
 arch/arm/mm/mmu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index e46a6a4..f5aa1de 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1251,9 +1251,14 @@ static inline void prepare_page_table(void)
 	/*
 	 * Clear out all the mappings below the kernel image.
 	 */
-	for (addr = 0; addr < MODULES_VADDR; addr += PMD_SIZE)
+	for (addr = 0; addr < TASK_SIZE; addr += PMD_SIZE)
 		pmd_clear(pmd_off_k(addr));
 
+#ifdef CONFIG_KASAN
+	/*TASK_SIZE ~ MODULES_VADDR is the KASAN's shadow area -- skip over it*/
+	addr = MODULES_VADDR;
+#endif
+
 #ifdef CONFIG_XIP_KERNEL
 	/* The XIP kernel is mapped in the module area -- skip over it */
 	addr = ((unsigned long)_exiprom + PMD_SIZE - 1) & PMD_MASK;
-- 
2.9.0