[RFC PATCH 4/7] powerpc: KASAN for 64bit Book3E
Christophe Leroy
christophe.leroy at c-s.fr
Thu May 23 16:15:11 AEST 2019
Le 23/05/2019 à 07:21, Daniel Axtens a écrit :
> Wire up KASAN. Only outline instrumentation is supported.
>
> The KASAN shadow area is mapped into vmemmap space:
> 0x8000 0400 0000 0000 to 0x8000 0600 0000 0000.
> To do this we require that vmemmap be disabled. (This is the default
> in the kernel config that QorIQ provides for the machine in their
> SDK anyway - they use flat memory.)
>
> Only the kernel linear mapping (0xc000...) is checked. The vmalloc and
> ioremap areas (also in 0x800...) are all mapped to the zero page. As
> with the Book3S hash series, this requires overriding the memory <->
> shadow mapping.
>
> Also, as with both previous 64-bit series, early instrumentation is not
> supported. It would allow us to drop the check_return_arch_not_ready()
> hook in the KASAN core, but it's tricky to get it set up early enough:
> we need it setup before the first call to instrumented code like printk().
> Perhaps in the future.
>
> Only KASAN_MINIMAL works.
See https://patchwork.ozlabs.org/patch/1068260/ for a full implementation
Christophe
>
> Tested on e6500. KVM, kexec and xmon have not been tested.
>
> The test_kasan module fires warnings as expected, except for the
> following tests:
>
> - Expected/by design:
> kasan test: memcg_accounted_kmem_cache allocate memcg accounted object
>
> - Due to only supporting KASAN_MINIMAL:
> kasan test: kasan_stack_oob out-of-bounds on stack
> kasan test: kasan_global_oob out-of-bounds global variable
> kasan test: kasan_alloca_oob_left out-of-bounds to left on alloca
> kasan test: kasan_alloca_oob_right out-of-bounds to right on alloca
> kasan test: use_after_scope_test use-after-scope on int
> kasan test: use_after_scope_test use-after-scope on array
>
> Thanks to those who have done the heavy lifting over the past several
> years:
> - Christophe's 32 bit series: https://lists.ozlabs.org/pipermail/linuxppc-dev/2019-February/185379.html
> - Aneesh's Book3S hash series: https://lwn.net/Articles/655642/
> - Balbir's Book3S radix series: https://patchwork.ozlabs.org/patch/795211/
>
> Cc: Christophe Leroy <christophe.leroy at c-s.fr>
> Cc: Aneesh Kumar K.V <aneesh.kumar at linux.vnet.ibm.com>
> Cc: Balbir Singh <bsingharora at gmail.com>
> Signed-off-by: Daniel Axtens <dja at axtens.net>
> [- Removed EXPORT_SYMBOL of the static key
> - Fixed most checkpatch problems
> - Replaced kasan_zero_page[] by kasan_early_shadow_page[]
> - Reduced casting mess by using intermediate locals
> - Fixed build failure on pmac32_defconfig]
> Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
> ---
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/Kconfig.debug | 2 +-
> arch/powerpc/include/asm/kasan.h | 71 ++++++++++++++++++++
> arch/powerpc/mm/kasan/Makefile | 1 +
> arch/powerpc/mm/kasan/kasan_init_book3e_64.c | 50 ++++++++++++++
> arch/powerpc/mm/nohash/Makefile | 5 ++
> 6 files changed, 129 insertions(+), 1 deletion(-)
> create mode 100644 arch/powerpc/mm/kasan/kasan_init_book3e_64.c
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 6a66a2da5b1a..4e266b019dd7 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -170,6 +170,7 @@ config PPC
> select HAVE_ARCH_AUDITSYSCALL
> select HAVE_ARCH_JUMP_LABEL
> select HAVE_ARCH_KASAN if PPC32
> + select HAVE_ARCH_KASAN if PPC_BOOK3E_64 && !SPARSEMEM_VMEMMAP
> select HAVE_ARCH_KGDB
> select HAVE_ARCH_MMAP_RND_BITS
> select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
> diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
> index c59920920ddc..23a37facc854 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -396,5 +396,5 @@ config PPC_FAST_ENDIAN_SWITCH
>
> config KASAN_SHADOW_OFFSET
> hex
> - depends on KASAN
> + depends on KASAN && PPC32
> default 0xe0000000
> diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
> index 296e51c2f066..ae410f0e060d 100644
> --- a/arch/powerpc/include/asm/kasan.h
> +++ b/arch/powerpc/include/asm/kasan.h
> @@ -21,12 +21,15 @@
> #define KASAN_SHADOW_START (KASAN_SHADOW_OFFSET + \
> (PAGE_OFFSET >> KASAN_SHADOW_SCALE_SHIFT))
>
> +#ifdef CONFIG_PPC32
> #define KASAN_SHADOW_OFFSET ASM_CONST(CONFIG_KASAN_SHADOW_OFFSET)
>
> #define KASAN_SHADOW_END 0UL
>
> #define KASAN_SHADOW_SIZE (KASAN_SHADOW_END - KASAN_SHADOW_START)
>
> +#endif /* CONFIG_PPC32 */
> +
> #ifdef CONFIG_KASAN
> void kasan_early_init(void);
> void kasan_mmu_init(void);
> @@ -36,5 +39,73 @@ static inline void kasan_init(void) { }
> static inline void kasan_mmu_init(void) { }
> #endif
>
> +#ifdef CONFIG_PPC_BOOK3E_64
> +#include <asm/pgtable.h>
> +#include <linux/jump_label.h>
> +
> +/*
> + * We don't put this in Kconfig as we only support KASAN_MINIMAL, and
> + * that will be disabled if the symbol is available in Kconfig
> + */
> +#define KASAN_SHADOW_OFFSET ASM_CONST(0x6800040000000000)
> +
> +#define KASAN_SHADOW_SIZE (KERN_VIRT_SIZE >> KASAN_SHADOW_SCALE_SHIFT)
> +
> +extern struct static_key_false powerpc_kasan_enabled_key;
> +extern unsigned char kasan_early_shadow_page[];
> +
> +static inline bool kasan_arch_is_ready_book3e(void)
> +{
> + if (static_branch_likely(&powerpc_kasan_enabled_key))
> + return true;
> + return false;
> +}
> +#define kasan_arch_is_ready kasan_arch_is_ready_book3e
> +
> +static inline void *kasan_mem_to_shadow_book3e(const void *ptr)
> +{
> + unsigned long addr = (unsigned long)ptr;
> +
> + if (addr >= KERN_VIRT_START && addr < KERN_VIRT_START + KERN_VIRT_SIZE)
> + return kasan_early_shadow_page;
> +
> + return (void *)(addr >> KASAN_SHADOW_SCALE_SHIFT) + KASAN_SHADOW_OFFSET;
> +}
> +#define kasan_mem_to_shadow kasan_mem_to_shadow_book3e
> +
> +static inline void *kasan_shadow_to_mem_book3e(const void *shadow_addr)
> +{
> + /*
> + * We map the entire non-linear virtual mapping onto the zero page so if
> + * we are asked to map the zero page back just pick the beginning of that
> + * area.
> + */
> + if (shadow_addr >= (void *)kasan_early_shadow_page &&
> + shadow_addr < (void *)(kasan_early_shadow_page + PAGE_SIZE))
> + return (void *)KERN_VIRT_START;
> +
> + return (void *)(((unsigned long)shadow_addr - KASAN_SHADOW_OFFSET) <<
> + KASAN_SHADOW_SCALE_SHIFT);
> +}
> +#define kasan_shadow_to_mem kasan_shadow_to_mem_book3e
> +
> +static inline bool kasan_addr_has_shadow_book3e(const void *ptr)
> +{
> + unsigned long addr = (unsigned long)ptr;
> +
> + /*
> + * We want to specifically assert that the addresses in the 0x8000...
> + * region have a shadow, otherwise they are considered by the kasan
> + * core to be wild pointers
> + */
> + if (addr >= KERN_VIRT_START && addr < (KERN_VIRT_START + KERN_VIRT_SIZE))
> + return true;
> +
> + return (ptr >= kasan_shadow_to_mem((void *)KASAN_SHADOW_START));
> +}
> +#define kasan_addr_has_shadow kasan_addr_has_shadow_book3e
> +
> +#endif /* CONFIG_PPC_BOOK3E_64 */
> +
> #endif /* __ASSEMBLY */
> #endif
> diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
> index 6577897673dd..f8f164ad8ade 100644
> --- a/arch/powerpc/mm/kasan/Makefile
> +++ b/arch/powerpc/mm/kasan/Makefile
> @@ -3,3 +3,4 @@
> KASAN_SANITIZE := n
>
> obj-$(CONFIG_PPC32) += kasan_init_32.o
> +obj-$(CONFIG_PPC_BOOK3E_64) += kasan_init_book3e_64.o
> diff --git a/arch/powerpc/mm/kasan/kasan_init_book3e_64.c b/arch/powerpc/mm/kasan/kasan_init_book3e_64.c
> new file mode 100644
> index 000000000000..f116c211d83c
> --- /dev/null
> +++ b/arch/powerpc/mm/kasan/kasan_init_book3e_64.c
> @@ -0,0 +1,50 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#define DISABLE_BRANCH_PROFILING
> +
> +#include <linux/kasan.h>
> +#include <linux/printk.h>
> +#include <linux/memblock.h>
> +#include <linux/sched/task.h>
> +#include <asm/pgalloc.h>
> +
> +DEFINE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
> +
> +static void __init kasan_init_region(struct memblock_region *reg)
> +{
> + void *start = __va(reg->base);
> + void *end = __va(reg->base + reg->size);
> + unsigned long k_start, k_end, k_cur;
> +
> + if (start >= end)
> + return;
> +
> + k_start = (unsigned long)kasan_mem_to_shadow(start);
> + k_end = (unsigned long)kasan_mem_to_shadow(end);
> +
> + for (k_cur = k_start; k_cur < k_end; k_cur += PAGE_SIZE) {
> + void *va = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> +
> + map_kernel_page(k_cur, __pa(va), PAGE_KERNEL);
> + }
> + flush_tlb_kernel_range(k_start, k_end);
> +}
> +
> +void __init kasan_init(void)
> +{
> + struct memblock_region *reg;
> +
> + for_each_memblock(memory, reg)
> + kasan_init_region(reg);
> +
> + /* map the zero page RO */
> + map_kernel_page((unsigned long)kasan_early_shadow_page,
> + __pa(kasan_early_shadow_page), PAGE_KERNEL_RO);
> +
> + /* Turn on checking */
> + static_branch_inc(&powerpc_kasan_enabled_key);
> +
> + /* Enable error messages */
> + init_task.kasan_depth = 0;
> + pr_info("KASAN init done (64-bit Book3E)\n");
> +}
> diff --git a/arch/powerpc/mm/nohash/Makefile b/arch/powerpc/mm/nohash/Makefile
> index 33b6f6f29d3f..310149f217d7 100644
> --- a/arch/powerpc/mm/nohash/Makefile
> +++ b/arch/powerpc/mm/nohash/Makefile
> @@ -16,3 +16,8 @@ endif
> # This is necessary for booting with kcov enabled on book3e machines
> KCOV_INSTRUMENT_tlb.o := n
> KCOV_INSTRUMENT_fsl_booke.o := n
> +
> +ifdef CONFIG_KASAN
> +CFLAGS_fsl_booke_mmu.o += -DDISABLE_BRANCH_PROFILING
> +CFLAGS_tlb.o += -DDISABLE_BRANCH_PROFILING
> +endif
>
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