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Subject: Re: [PATCH RFC v3 18/18] powerpc: KASAN for 64bit Book3E
From:   Christophe Leroy <christophe.leroy@c-s.fr>
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Daniel Axtens <dja@axtens.net>
Cc:     linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com
References: <cover.1552428161.git.christophe.leroy@c-s.fr>
 <3e97aba429c769bd99ccd8d6f16eda98f7d378a7.1552428161.git.christophe.leroy@c-s.fr>
Message-ID: <62ba1b83-cc75-82a4-a1c0-5a54464c963b@c-s.fr>
Date:   Wed, 13 Mar 2019 08:02:01 +0100
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Why does snowpatch reports not being able to apply it to any branch ?

I built the serie on top of merge branch, but it also cleanly applies on 
next branch.

Could it be because the begining of the series is names 'v10' while the 
end of it is 'RFC v3' as it comes from Daniel's RFC v2 ?

Christophe

Le 12/03/2019 à 23:16, Christophe Leroy a écrit :
> From: Daniel Axtens <dja@axtens.net>
> 
> 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.
> 
> 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@c-s.fr>
> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Cc: Balbir Singh <bsingharora@gmail.com>
> Signed-off-by: Daniel Axtens <dja@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@c-s.fr>
> ---
>   arch/powerpc/Kconfig                         |  1 +
>   arch/powerpc/Kconfig.debug                   |  2 +-
>   arch/powerpc/include/asm/kasan.h             | 71 ++++++++++++++++++++++++++++
>   arch/powerpc/mm/Makefile                     |  2 +
>   arch/powerpc/mm/kasan/Makefile               |  1 +
>   arch/powerpc/mm/kasan/kasan_init_book3e_64.c | 50 ++++++++++++++++++++
>   6 files changed, 126 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 d9364368329b..51ef9fac6c5d 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -174,6 +174,7 @@ 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 61febbbdd02b..fc1f5fa7554e 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -369,5 +369,5 @@ 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/Makefile b/arch/powerpc/mm/Makefile
> index 80382a2d169b..fc49231f807c 100644
> --- a/arch/powerpc/mm/Makefile
> +++ b/arch/powerpc/mm/Makefile
> @@ -8,9 +8,11 @@ ccflags-$(CONFIG_PPC64)	:= $(NO_MINIMAL_TOC)
>   CFLAGS_REMOVE_slb.o = $(CC_FLAGS_FTRACE)
>   
>   KASAN_SANITIZE_ppc_mmu_32.o := n
> +KASAN_SANITIZE_fsl_booke_mmu.o := n
>   
>   ifdef CONFIG_KASAN
>   CFLAGS_ppc_mmu_32.o  		+= -DDISABLE_BRANCH_PROFILING
> +CFLAGS_fsl_booke_mmu.o		+= -DDISABLE_BRANCH_PROFILING
>   endif
>   
>   obj-y				:= fault.o mem.o pgtable.o mmap.o \
> diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
> index 6577897673dd..f8f164ad8ade 100644
> --- a/arch/powerpc/mm/kasan/Makefile
> +++ b/arch/powerpc/mm/kasan/Makefile
> @@ -3,3 +3,4 @@
>   KASAN_SANITIZE := n
>   
>   obj-$(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");
> +}
>