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xtensa: add support for KASAN

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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: Max Filippov <jcmvbkbc@gmail.com>
This commit is contained in:
Max Filippov 2017-12-03 13:28:52 -08:00
parent 1af1e8a39d
commit c633544a61
15 changed files with 201 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/features/debug/KASAN/arch-support.txt
View File

@ -35,5 +35,5 @@
| um: | TODO |
| unicore32: | TODO |
| x86: | ok |
| xtensa: | TODO |
| xtensa: | ok |
-----------------------

6
Documentation/xtensa/mmu.txt
View File

@ -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

5
arch/xtensa/Kconfig
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@ -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

2
arch/xtensa/boot/lib/Makefile
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@ -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

37
arch/xtensa/include/asm/kasan.h Normal file
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@ -0,0 +1,37 @@
/* 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

4
arch/xtensa/include/asm/kmem_layout.h
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@ -71,7 +71,11 @@
#endif
#ifndef CONFIG_KASAN
#define KERNEL_STACK_SHIFT 13
#else
#define KERNEL_STACK_SHIFT 15
#endif
#define KERNEL_STACK_SIZE (1 << KERNEL_STACK_SHIFT)
#endif

3
arch/xtensa/include/asm/pgtable.h
View File

@ -12,9 +12,9 @@
#define _XTENSA_PGTABLE_H
#define __ARCH_USE_5LEVEL_HACK
#include <asm-generic/pgtable-nopmd.h>
#include <asm/page.h>
#include <asm/kmem_layout.h>
#include <asm-generic/pgtable-nopmd.h>
/*
* We only use two ring levels, user and kernel space.
@ -170,6 +170,7 @@
#define PAGE_SHARED_EXEC \
__pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_WRITABLE | _PAGE_HW_EXEC)
#define PAGE_KERNEL __pgprot(_PAGE_PRESENT | _PAGE_HW_WRITE)
#define PAGE_KERNEL_RO __pgprot(_PAGE_PRESENT)
#define PAGE_KERNEL_EXEC __pgprot(_PAGE_PRESENT|_PAGE_HW_WRITE|_PAGE_HW_EXEC)
#if (DCACHE_WAY_SIZE > PAGE_SIZE)

19
arch/xtensa/include/asm/string.h
View File

@ -108,14 +108,33 @@ static inline int strncmp(const char *__cs, const char *__ct, size_t __n)
#define __HAVE_ARCH_MEMSET
extern void *memset(void *__s, int __c, size_t __count);
extern void *__memset(void *__s, int __c, size_t __count);
#define __HAVE_ARCH_MEMCPY
extern void *memcpy(void *__to, __const__ void *__from, size_t __n);
extern void *__memcpy(void *__to, __const__ void *__from, size_t __n);
#define __HAVE_ARCH_MEMMOVE
extern void *memmove(void *__dest, __const__ void *__src, size_t __n);
extern void *__memmove(void *__dest, __const__ void *__src, size_t __n);
/* Don't build bcopy at all ... */
#define __HAVE_ARCH_BCOPY
#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
/*
* For files that are not instrumented (e.g. mm/slub.c) we
* should use not instrumented version of mem* functions.
*/
#define memcpy(dst, src, len) __memcpy(dst, src, len)
#define memmove(dst, src, len) __memmove(dst, src, len)
#define memset(s, c, n) __memset(s, c, n)
#ifndef __NO_FORTIFY
#define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */
#endif
#endif
#endif /* _XTENSA_STRING_H */

7
arch/xtensa/kernel/setup.c
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@ -36,6 +36,7 @@
#endif
#include <asm/bootparam.h>
#include <asm/kasan.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
@ -251,6 +252,10 @@ void __init init_arch(bp_tag_t *bp_start)
init_mmu();
/* Initialize initial KASAN shadow map */
kasan_early_init();
/* Parse boot parameters */
if (bp_start)
@ -388,7 +393,7 @@ void __init setup_arch(char **cmdline_p)
#endif
parse_early_param();
bootmem_init();
kasan_init();
unflatten_and_copy_device_tree();
#ifdef CONFIG_SMP

3
arch/xtensa/kernel/xtensa_ksyms.c
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@ -41,6 +41,9 @@
EXPORT_SYMBOL(memset);
EXPORT_SYMBOL(memcpy);
EXPORT_SYMBOL(memmove);
EXPORT_SYMBOL(__memset);
EXPORT_SYMBOL(__memcpy);
EXPORT_SYMBOL(__memmove);
EXPORT_SYMBOL(__strncpy_user);
EXPORT_SYMBOL(clear_page);
EXPORT_SYMBOL(copy_page);

10
arch/xtensa/lib/memcopy.S
View File

@ -109,7 +109,8 @@
addi a5, a5, 2
j .Ldstaligned # dst is now aligned, return to main algorithm
ENTRY(memcpy)
ENTRY(__memcpy)
WEAK(memcpy)
entry sp, 16 # minimal stack frame
# a2/ dst, a3/ src, a4/ len
@ -271,7 +272,7 @@ ENTRY(memcpy)
s8i a6, a5, 0
retw
ENDPROC(memcpy)
ENDPROC(__memcpy)
/*
* void bcopy(const void *src, void *dest, size_t n);
@ -376,7 +377,8 @@ ENDPROC(bcopy)
j .Lbackdstaligned # dst is now aligned,
# return to main algorithm
ENTRY(memmove)
ENTRY(__memmove)
WEAK(memmove)
entry sp, 16 # minimal stack frame
# a2/ dst, a3/ src, a4/ len
@ -548,4 +550,4 @@ ENTRY(memmove)
s8i a6, a5, 0
retw
ENDPROC(memmove)
ENDPROC(__memmove)

5
arch/xtensa/lib/memset.S
View File

@ -31,7 +31,8 @@
*/
.text
ENTRY(memset)
ENTRY(__memset)
WEAK(memset)
entry sp, 16 # minimal stack frame
# a2/ dst, a3/ c, a4/ length
@ -140,7 +141,7 @@ EX(10f) s8i a3, a5, 0
.Lbytesetdone:
retw
ENDPROC(memset)
ENDPROC(__memset)
.section .fixup, "ax"
.align 4

5
arch/xtensa/mm/Makefile
View File

@ -5,3 +5,8 @@
obj-y := init.o misc.o
obj-$(CONFIG_MMU) += cache.o fault.o ioremap.o mmu.o tlb.o
obj-$(CONFIG_HIGHMEM) += highmem.o
obj-$(CONFIG_KASAN) += kasan_init.o
KASAN_SANITIZE_fault.o := n
KASAN_SANITIZE_kasan_init.o := n
KASAN_SANITIZE_mmu.o := n

7
arch/xtensa/mm/init.c
View File

@ -100,6 +100,9 @@ void __init mem_init(void)
mem_init_print_info(NULL);
pr_info("virtual kernel memory layout:\n"
#ifdef CONFIG_KASAN
" kasan : 0x%08lx - 0x%08lx (%5lu MB)\n"
#endif
#ifdef CONFIG_MMU
" vmalloc : 0x%08lx - 0x%08lx (%5lu MB)\n"
#endif
@ -108,6 +111,10 @@ void __init mem_init(void)
" fixmap : 0x%08lx - 0x%08lx (%5lu kB)\n"
#endif
" lowmem : 0x%08lx - 0x%08lx (%5lu MB)\n",
#ifdef CONFIG_KASAN
KASAN_SHADOW_START, KASAN_SHADOW_START + KASAN_SHADOW_SIZE,
KASAN_SHADOW_SIZE >> 20,
#endif
#ifdef CONFIG_MMU
VMALLOC_START, VMALLOC_END,
(VMALLOC_END - VMALLOC_START) >> 20,

95
arch/xtensa/mm/kasan_init.c Normal file
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@ -0,0 +1,95 @@
/*
* Xtensa KASAN shadow map initialization
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2017 Cadence Design Systems Inc.
*/
#include <linux/bootmem.h>
#include <linux/init_task.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/memblock.h>
#include <asm/initialize_mmu.h>
#include <asm/tlbflush.h>
#include <asm/traps.h>
void __init kasan_early_init(void)
{
unsigned long vaddr = KASAN_SHADOW_START;
pgd_t *pgd = pgd_offset_k(vaddr);
pmd_t *pmd = pmd_offset(pgd, vaddr);
int i;
for (i = 0; i < PTRS_PER_PTE; ++i)
set_pte(kasan_zero_pte + i,
mk_pte(virt_to_page(kasan_zero_page), PAGE_KERNEL));
for (vaddr = 0; vaddr < KASAN_SHADOW_SIZE; vaddr += PMD_SIZE, ++pmd) {
BUG_ON(!pmd_none(*pmd));
set_pmd(pmd, __pmd((unsigned long)kasan_zero_pte));
}
early_trap_init();
}
static void __init populate(void *start, void *end)
{
unsigned long n_pages = (end - start) / PAGE_SIZE;
unsigned long n_pmds = n_pages / PTRS_PER_PTE;
unsigned long i, j;
unsigned long vaddr = (unsigned long)start;
pgd_t *pgd = pgd_offset_k(vaddr);
pmd_t *pmd = pmd_offset(pgd, vaddr);
pte_t *pte = memblock_virt_alloc(n_pages * sizeof(pte_t), PAGE_SIZE);
pr_debug("%s: %p - %p\n", __func__, start, end);
for (i = j = 0; i < n_pmds; ++i) {
int k;
for (k = 0; k < PTRS_PER_PTE; ++k, ++j) {
phys_addr_t phys =
memblock_alloc_base(PAGE_SIZE, PAGE_SIZE,
MEMBLOCK_ALLOC_ANYWHERE);
set_pte(pte + j, pfn_pte(PHYS_PFN(phys), PAGE_KERNEL));
}
}
for (i = 0; i < n_pmds ; ++i, pte += PTRS_PER_PTE)
set_pmd(pmd + i, __pmd((unsigned long)pte));
local_flush_tlb_all();
memset(start, 0, end - start);
}
void __init kasan_init(void)
{
int i;
BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_START -
(KASAN_START_VADDR >> KASAN_SHADOW_SCALE_SHIFT));
BUILD_BUG_ON(VMALLOC_START < KASAN_START_VADDR);
/*
* Replace shadow map pages that cover addresses from VMALLOC area
* start to the end of KSEG with clean writable pages.
*/
populate(kasan_mem_to_shadow((void *)VMALLOC_START),
kasan_mem_to_shadow((void *)XCHAL_KSEG_BYPASS_VADDR));
/* Write protect kasan_zero_page and zero-initialize it again. */
for (i = 0; i < PTRS_PER_PTE; ++i)
set_pte(kasan_zero_pte + i,
mk_pte(virt_to_page(kasan_zero_page), PAGE_KERNEL_RO));
local_flush_tlb_all();
memset(kasan_zero_page, 0, PAGE_SIZE);
/* At this point kasan is fully initialized. Enable error messages. */
current->kasan_depth = 0;
pr_info("KernelAddressSanitizer initialized\n");
}