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Commit c633544a authored by Max Filippov's avatar Max Filippov
Browse files

xtensa: add support for KASAN 



Cover kernel addresses above 0x90000000 by the shadow map. Enable
HAVE_ARCH_KASAN when MMU is enabled. Provide kasan_early_init that fills
shadow map with writable copies of kasan_zero_page. Call
kasan_early_init right after mmu initialization in the setup_arch.
Provide kasan_init that allocates proper shadow map pages from the
memblock and puts these pages into the shadow map for addresses from
VMALLOC area to the end of KSEG. Call kasan_init right after memblock
initialization. Don't use KASAN for the boot code, MMU and KASAN
initialization and page fault handler. Make kernel stack size 4 times
larger when KASAN is enabled to avoid stack overflows.
GCC 7.3, 8 or newer is required to build the xtensa kernel with KASAN.

Signed-off-by: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent 1af1e8a3

Documentation/features/debug/KASAN/arch-support.txt

+1 −1
Original line number Diff line number Diff line
@@ -35,5 +35,5 @@ 
    |          um: | TODO |

    |   unicore32: | TODO |

    |         x86: |  ok  |

    |      xtensa: | TODO |

    |      xtensa: |  ok  |

    -----------------------

Documentation/xtensa/mmu.txt

+6 −0
Original line number Diff line number Diff line
@@ -71,6 +71,8 @@ Default MMUv2-compatible layout. 
+------------------+

| Page table       |  XCHAL_PAGE_TABLE_VADDR   0x80000000  XCHAL_PAGE_TABLE_SIZE

+------------------+

| KASAN shadow map |  KASAN_SHADOW_START       0x80400000  KASAN_SHADOW_SIZE

+------------------+                           0x8e400000

+------------------+

| VMALLOC area     |  VMALLOC_START            0xc0000000  128MB - 64KB

+------------------+  VMALLOC_END
@@ -111,6 +113,8 @@ Default MMUv2-compatible layout. 
+------------------+

| Page table       |  XCHAL_PAGE_TABLE_VADDR   0x80000000  XCHAL_PAGE_TABLE_SIZE

+------------------+

| KASAN shadow map |  KASAN_SHADOW_START       0x80400000  KASAN_SHADOW_SIZE

+------------------+                           0x8e400000

+------------------+

| VMALLOC area     |  VMALLOC_START            0xa0000000  128MB - 64KB

+------------------+  VMALLOC_END
@@ -152,6 +156,8 @@ Default MMUv2-compatible layout. 
+------------------+

| Page table       |  XCHAL_PAGE_TABLE_VADDR   0x80000000  XCHAL_PAGE_TABLE_SIZE

+------------------+

| KASAN shadow map |  KASAN_SHADOW_START       0x80400000  KASAN_SHADOW_SIZE

+------------------+                           0x8e400000

+------------------+

| VMALLOC area     |  VMALLOC_START            0x90000000  128MB - 64KB

+------------------+  VMALLOC_END

arch/xtensa/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ config XTENSA 
	select GENERIC_IRQ_SHOW

	select GENERIC_PCI_IOMAP

	select GENERIC_SCHED_CLOCK

	select HAVE_ARCH_KASAN if MMU

	select HAVE_CC_STACKPROTECTOR

	select HAVE_DEBUG_KMEMLEAK

	select HAVE_DMA_API_DEBUG
@@ -80,6 +81,10 @@ config VARIANT_IRQ_SWITCH 
config HAVE_XTENSA_GPIO32

	def_bool n



config KASAN_SHADOW_OFFSET

	hex

	default 0x6e400000



menu "Processor type and features"



choice

arch/xtensa/boot/lib/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -15,6 +15,8 @@ CFLAGS_REMOVE_inftrees.o = -pg 
CFLAGS_REMOVE_inffast.o = -pg

endif



KASAN_SANITIZE := n



CFLAGS_REMOVE_inflate.o += -fstack-protector -fstack-protector-strong

CFLAGS_REMOVE_zmem.o += -fstack-protector -fstack-protector-strong

CFLAGS_REMOVE_inftrees.o += -fstack-protector -fstack-protector-strong

arch/xtensa/include/asm/kasan.h

0 → 100644
+37 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef __ASM_KASAN_H

#define __ASM_KASAN_H



#ifndef __ASSEMBLY__



#ifdef CONFIG_KASAN



#include <linux/kernel.h>

#include <linux/sizes.h>

#include <asm/kmem_layout.h>



/* Start of area covered by KASAN */

#define KASAN_START_VADDR __XTENSA_UL_CONST(0x90000000)

/* Start of the shadow map */

#define KASAN_SHADOW_START (XCHAL_PAGE_TABLE_VADDR + XCHAL_PAGE_TABLE_SIZE)

/* Size of the shadow map */

#define KASAN_SHADOW_SIZE (-KASAN_START_VADDR >> KASAN_SHADOW_SCALE_SHIFT)

/* Offset for mem to shadow address transformation */

#define KASAN_SHADOW_OFFSET __XTENSA_UL_CONST(CONFIG_KASAN_SHADOW_OFFSET)



void __init kasan_early_init(void);

void __init kasan_init(void);



#else



static inline void kasan_early_init(void)

{

}



static inline void kasan_init(void)

{

}



#endif

#endif

#endif