[PATCH v2 2/2] riscv: Add KASAN support

Nick Hu
2019-10-02T06:17:30Z

This patch ports the feature Kernel Address SANitizer (KASAN).

Note: The start address of shadow memory is at the beginning of kernel
space, which is 2^64 - (2^39 / 2) in SV39. The size of the kernel space is
2^38 bytes so the size of shadow memory should be 2^38 / 8. Thus, the
shadow memory would not overlap with the fixmap area.

There are currently two limitations in this port,

1. RV64 only: KASAN need large address space for extra shadow memory
region.

2. KASAN can't debug the modules since the modules are allocated in VMALLOC
area. We mapped the shadow memory, which corresponding to VMALLOC area, to
the kasan_early_shadow_page because we don't have enough physical space for
all the shadow memory corresponding to VMALLOC area.

Signed-off-by: Nick Hu <nickhu@andestech.com>
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/kasan.h | 27 ++++++++
arch/riscv/include/asm/pgtable-64.h | 5 ++
arch/riscv/include/asm/string.h | 9 +++
arch/riscv/kernel/head.S | 3 +
arch/riscv/kernel/riscv_ksyms.c | 2 +
arch/riscv/kernel/setup.c | 5 ++
arch/riscv/kernel/vmlinux.lds.S | 1 +
arch/riscv/lib/memcpy.S | 5 +-
arch/riscv/lib/memset.S | 5 +-
arch/riscv/mm/Makefile | 6 ++
arch/riscv/mm/kasan_init.c | 104 ++++++++++++++++++++++++++++
12 files changed, 169 insertions(+), 4 deletions(-)
create mode 100644 arch/riscv/include/asm/kasan.h
create mode 100644 arch/riscv/mm/kasan_init.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 8eebbc8860bb..ca2fc8ba8550 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -61,6 +61,7 @@ config RISCV
select SPARSEMEM_STATIC if 32BIT
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
select HAVE_ARCH_MMAP_RND_BITS
+ select HAVE_ARCH_KASAN if MMU && 64BIT

config ARCH_MMAP_RND_BITS_MIN
default 18 if 64BIT
diff --git a/arch/riscv/include/asm/kasan.h b/arch/riscv/include/asm/kasan.h
new file mode 100644
index 000000000000..eb9b1a2f641c
--- /dev/null
+++ b/arch/riscv/include/asm/kasan.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 Andes Technology Corporation */
+
+#ifndef __ASM_KASAN_H
+#define __ASM_KASAN_H
+
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_KASAN
+
+#include <asm/pgtable.h>
+
+#define KASAN_SHADOW_SCALE_SHIFT 3
+
+#define KASAN_SHADOW_SIZE (UL(1) << (38 - KASAN_SHADOW_SCALE_SHIFT))
+#define KASAN_SHADOW_START 0xffffffc000000000 // 2^64 - 2^38
+#define KASAN_SHADOW_END (KASAN_SHADOW_START + KASAN_SHADOW_SIZE)
+
+#define KASAN_SHADOW_OFFSET (KASAN_SHADOW_END - (1ULL << \
+ (64 - KASAN_SHADOW_SCALE_SHIFT)))
+
+void kasan_init(void);
+asmlinkage void kasan_early_init(void);
+
+#endif
+#endif
+#endif /* __ASM_KASAN_H */
diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
index 7df8daa66cc8..777a1dddb3df 100644
--- a/arch/riscv/include/asm/pgtable-64.h
+++ b/arch/riscv/include/asm/pgtable-64.h
@@ -59,6 +59,11 @@ static inline unsigned long pud_page_vaddr(pud_t pud)
return (unsigned long)pfn_to_virt(pud_val(pud) >> _PAGE_PFN_SHIFT);
}

+static inline struct page *pud_page(pud_t pud)
+{
+ return pfn_to_page(pud_val(pud) >> _PAGE_PFN_SHIFT);
+}
+
#define pmd_index(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))

static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h
index 1b5d44585962..a4451f768826 100644
--- a/arch/riscv/include/asm/string.h
+++ b/arch/riscv/include/asm/string.h
@@ -11,8 +11,17 @@

#define __HAVE_ARCH_MEMSET
extern asmlinkage void *memset(void *, int, size_t);
+extern asmlinkage void *__memset(void *, int, size_t);

#define __HAVE_ARCH_MEMCPY
extern asmlinkage void *memcpy(void *, const void *, size_t);
+extern asmlinkage void *__memcpy(void *, const void *, size_t);

+// For those files which don't want to check by kasan.
+#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
+
+#define memcpy(dst, src, len) __memcpy(dst, src, len)
+#define memset(s, c, n) __memset(s, c, n)
+
+#endif
#endif /* _ASM_RISCV_STRING_H */
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 72f89b7590dd..95eca23cd811 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -102,6 +102,9 @@ clear_bss_done:
sw zero, TASK_TI_CPU(tp)
la sp, init_thread_union + THREAD_SIZE

+#ifdef CONFIG_KASAN
+ call kasan_early_init
+#endif
/* Start the kernel */
call parse_dtb
tail start_kernel
diff --git a/arch/riscv/kernel/riscv_ksyms.c b/arch/riscv/kernel/riscv_ksyms.c
index 4800cf703186..376bba7f65ce 100644
--- a/arch/riscv/kernel/riscv_ksyms.c
+++ b/arch/riscv/kernel/riscv_ksyms.c
@@ -14,3 +14,5 @@ EXPORT_SYMBOL(__asm_copy_to_user);
EXPORT_SYMBOL(__asm_copy_from_user);
EXPORT_SYMBOL(memset);
EXPORT_SYMBOL(memcpy);
+EXPORT_SYMBOL(__memset);
+EXPORT_SYMBOL(__memcpy);
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index a990a6cb184f..41f7eae9bc4d 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -23,6 +23,7 @@
#include <asm/smp.h>
#include <asm/tlbflush.h>
#include <asm/thread_info.h>
+#include <asm/kasan.h>

#ifdef CONFIG_DUMMY_CONSOLE
struct screen_info screen_info = {
@@ -70,6 +71,10 @@ void __init setup_arch(char **cmdline_p)
swiotlb_init(1);
#endif

+#ifdef CONFIG_KASAN
+ kasan_init();
+#endif
+
#ifdef CONFIG_SMP
setup_smp();
#endif
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 23cd1a9e52a1..97009803ba9f 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -46,6 +46,7 @@ SECTIONS
KPROBES_TEXT
ENTRY_TEXT
IRQENTRY_TEXT
+ SOFTIRQENTRY_TEXT
*(.fixup)
_etext = .;
}
diff --git a/arch/riscv/lib/memcpy.S b/arch/riscv/lib/memcpy.S
index b4c477846e91..51ab716253fa 100644
--- a/arch/riscv/lib/memcpy.S
+++ b/arch/riscv/lib/memcpy.S
@@ -7,7 +7,8 @@
#include <asm/asm.h>

/* void *memcpy(void *, const void *, size_t) */
-ENTRY(memcpy)
+ENTRY(__memcpy)
+WEAK(memcpy)
move t6, a0 /* Preserve return value */

/* Defer to byte-oriented copy for small sizes */
@@ -104,4 +105,4 @@ ENTRY(memcpy)
bltu a1, a3, 5b
6:
ret
-END(memcpy)
+END(__memcpy)
diff --git a/arch/riscv/lib/memset.S b/arch/riscv/lib/memset.S
index 5a7386b47175..34c5360c6705 100644
--- a/arch/riscv/lib/memset.S
+++ b/arch/riscv/lib/memset.S
@@ -8,7 +8,8 @@
#include <asm/asm.h>

/* void *memset(void *, int, size_t) */
-ENTRY(memset)
+ENTRY(__memset)
+WEAK(memset)
move t0, a0 /* Preserve return value */

/* Defer to byte-oriented fill for small sizes */
@@ -109,4 +110,4 @@ ENTRY(memset)
bltu t0, a3, 5b
6:
ret
-END(memset)
+END(__memset)
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index 9d9a17335686..b8a8ca71f86e 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -17,3 +17,9 @@ ifeq ($(CONFIG_MMU),y)
obj-$(CONFIG_SMP) += tlbflush.o
endif
obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
+obj-$(CONFIG_KASAN) += kasan_init.o
+
+ifdef CONFIG_KASAN
+KASAN_SANITIZE_kasan_init.o := n
+KASAN_SANITIZE_init.o := n
+endif
diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
new file mode 100644
index 000000000000..c3152768cdbe
--- /dev/null
+++ b/arch/riscv/mm/kasan_init.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2019 Andes Technology Corporation
+
+#include <linux/pfn.h>
+#include <linux/init_task.h>
+#include <linux/kasan.h>
+#include <linux/kernel.h>
+#include <linux/memblock.h>
+#include <asm/tlbflush.h>
+#include <asm/pgtable.h>
+#include <asm/fixmap.h>
+
+extern pgd_t early_pg_dir[PTRS_PER_PGD];
+asmlinkage void __init kasan_early_init(void)
+{
+ uintptr_t i;
+ pgd_t *pgd = early_pg_dir + pgd_index(KASAN_SHADOW_START);
+
+ for (i = 0; i < PTRS_PER_PTE; ++i)
+ set_pte(kasan_early_shadow_pte + i,
+ mk_pte(virt_to_page(kasan_early_shadow_page),
+ PAGE_KERNEL));
+
+ for (i = 0; i < PTRS_PER_PMD; ++i)
+ set_pmd(kasan_early_shadow_pmd + i,
+ pfn_pmd(PFN_DOWN(__pa((uintptr_t)kasan_early_shadow_pte)),
+ __pgprot(_PAGE_TABLE)));
+
+ for (i = KASAN_SHADOW_START; i < KASAN_SHADOW_END;
+ i += PGDIR_SIZE, ++pgd)
+ set_pgd(pgd,
+ pfn_pgd(PFN_DOWN(__pa(((uintptr_t)kasan_early_shadow_pmd))),
+ __pgprot(_PAGE_TABLE)));
+
+ // init for swapper_pg_dir
+ pgd = pgd_offset_k(KASAN_SHADOW_START);
+
+ for (i = KASAN_SHADOW_START; i < KASAN_SHADOW_END;
+ i += PGDIR_SIZE, ++pgd)
+ set_pgd(pgd,
+ pfn_pgd(PFN_DOWN(__pa(((uintptr_t)kasan_early_shadow_pmd))),
+ __pgprot(_PAGE_TABLE)));
+
+ flush_tlb_all();
+}
+
+static void __init populate(void *start, void *end)
+{
+ unsigned long i;
+ unsigned long vaddr = (unsigned long)start & PAGE_MASK;
+ unsigned long vend = PAGE_ALIGN((unsigned long)end);
+ unsigned long n_pages = (vend - vaddr) / PAGE_SIZE;
+ unsigned long n_pmds =
+ (n_pages % PTRS_PER_PTE) ? n_pages / PTRS_PER_PTE + 1 :
+ n_pages / PTRS_PER_PTE;
+ pgd_t *pgd = pgd_offset_k(vaddr);
+ pmd_t *pmd = memblock_alloc(n_pmds * sizeof(pmd_t), PAGE_SIZE);
+ pte_t *pte = memblock_alloc(n_pages * sizeof(pte_t), PAGE_SIZE);
+
+ for (i = 0; i < n_pages; i++) {
+ phys_addr_t phys = memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
+
+ set_pte(pte + i, pfn_pte(PHYS_PFN(phys), PAGE_KERNEL));
+ }
+
+ for (i = 0; i < n_pages; ++pmd, i += PTRS_PER_PTE)
+ set_pmd(pmd, pfn_pmd(PFN_DOWN(__pa((uintptr_t)(pte + i))),
+ __pgprot(_PAGE_TABLE)));
+
+ for (i = vaddr; i < vend; i += PGDIR_SIZE, ++pgd)
+ set_pgd(pgd, pfn_pgd(PFN_DOWN(__pa(((uintptr_t)pmd))),
+ __pgprot(_PAGE_TABLE)));
+
+ flush_tlb_all();
+ memset(start, 0, end - start);
+}
+
+void __init kasan_init(void)
+{
+ struct memblock_region *reg;
+ unsigned long i;
+
+ kasan_populate_early_shadow((void *)KASAN_SHADOW_START,
+ (void *)kasan_mem_to_shadow((void *)VMALLOC_END));
+
+ for_each_memblock(memory, reg) {
+ void *start = (void *)__va(reg->base);
+ void *end = (void *)__va(reg->base + reg->size);
+
+ if (start >= end)
+ break;
+
+ populate(kasan_mem_to_shadow(start),
+ kasan_mem_to_shadow(end));
+ };
+
+ for (i = 0; i < PTRS_PER_PTE; i++)
+ set_pte(&kasan_early_shadow_pte[i],
+ mk_pte(virt_to_page(kasan_early_shadow_page),
+ __pgprot(_PAGE_PRESENT | _PAGE_READ | _PAGE_ACCESSED)));
+
+ memset(kasan_early_shadow_page, 0, PAGE_SIZE);
+ init_task.kasan_depth = 0;
+}
--
2.17.0