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Subject: Re: [RFC PATCH] powerpc/book3e: KASAN Full support for 64bit
From:   Christophe Leroy <christophe.leroy@c-s.fr>
To:     dja@axtens.net
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
References: <3401648225001077db54172ee87573b21e1cfa38.1553782837.git.christophe.leroy@c-s.fr>
Message-ID: <488ecc81-ac72-ec04-380a-bd04d4def39d@c-s.fr>
Date:   Thu, 28 Mar 2019 15:40:11 +0100
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Daniel,

This patch applies on top of my series.

With this patch, I've managed to enable KASAN without the changes you 
proposed on the KASAN core. This allows a full support of KASAN, ie not 
limited to KASAN_MINIMAL.

There is still some details to address, but it boots OK on qemu-e500.

Can you have a try and tell me if it works on your side too ?

It will likely fail for modules at the time being as I did nothing about it.

Tell me if you continue working on it. I don't plan to spend more time 
on it for the time being.

Like I did on PPC32, it would be good to create an early_64.c file and 
move into it the few functions from setup_64.c and paca.c that are 
called before feature_fixups are done, in order to not disable KASAN on 
the entire paca.c and setup_64.c

I guess we could reduce a bit the size of the IOREMAP_AREA and put KASAN 
on top of it instead of using VMEMMAP space, allthough I don't have a 
clean view of how it would cooperate with VMEMMMAP if we keep it enabled.

I've not been able to identify what is the largest size of the linear 
mapping (ie the 0xc000000000000000 region).

Christophe

Le 28/03/2019 à 15:21, Christophe Leroy a écrit :
> The KASAN shadow area is mapped into vmemmap space:
> 0x8000 0400 0000 0000 to 0x8000 0600 0000 0000.
> For this vmemmap has to be disabled.
> 
> Cc: Daniel Axtens <dja@axtens.net>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>   arch/powerpc/Kconfig                  |   1 +
>   arch/powerpc/Kconfig.debug            |   3 +-
>   arch/powerpc/include/asm/kasan.h      |  11 +++
>   arch/powerpc/kernel/Makefile          |   2 +
>   arch/powerpc/kernel/head_64.S         |   3 +
>   arch/powerpc/kernel/setup_64.c        |  20 +++---
>   arch/powerpc/mm/kasan/Makefile        |   1 +
>   arch/powerpc/mm/kasan/kasan_init_64.c | 129 ++++++++++++++++++++++++++++++++++
>   8 files changed, 159 insertions(+), 11 deletions(-)
>   create mode 100644 arch/powerpc/mm/kasan/kasan_init_64.c
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 1a2fb50126b2..e0b7c45e4dc7 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..b4140dd6b4e4 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -370,4 +370,5 @@ config PPC_FAST_ENDIAN_SWITCH
>   config KASAN_SHADOW_OFFSET
>   	hex
>   	depends on KASAN
> -	default 0xe0000000
> +	default 0xe0000000 if PPC32
> +	default 0x6800040000000000 if PPC64
> diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
> index 296e51c2f066..756b3d58f921 100644
> --- a/arch/powerpc/include/asm/kasan.h
> +++ b/arch/powerpc/include/asm/kasan.h
> @@ -23,10 +23,21 @@
>   
>   #define KASAN_SHADOW_OFFSET	ASM_CONST(CONFIG_KASAN_SHADOW_OFFSET)
>   
> +#ifdef CONFIG_PPC32
>   #define KASAN_SHADOW_END	0UL
>   
>   #define KASAN_SHADOW_SIZE	(KASAN_SHADOW_END - KASAN_SHADOW_START)
>   
> +#else
> +
> +#include <asm/pgtable.h>
> +
> +#define KASAN_SHADOW_SIZE	(KERN_VIRT_SIZE >> KASAN_SHADOW_SCALE_SHIFT)
> +
> +#define KASAN_SHADOW_END	(KASAN_SHADOW_START + KASAN_SHADOW_SIZE)
> +
> +#endif /* CONFIG_PPC32 */
> +
>   #ifdef CONFIG_KASAN
>   void kasan_early_init(void);
>   void kasan_mmu_init(void);
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index 0ea6c4aa3a20..7f232c06f11d 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -35,6 +35,8 @@ KASAN_SANITIZE_early_32.o := n
>   KASAN_SANITIZE_cputable.o := n
>   KASAN_SANITIZE_prom_init.o := n
>   KASAN_SANITIZE_btext.o := n
> +KASAN_SANITIZE_paca.o := n
> +KASAN_SANITIZE_setup_64.o := n
>   
>   ifdef CONFIG_KASAN
>   CFLAGS_early_32.o += -DDISABLE_BRANCH_PROFILING
> diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
> index 3fad8d499767..80fbd8024fb2 100644
> --- a/arch/powerpc/kernel/head_64.S
> +++ b/arch/powerpc/kernel/head_64.S
> @@ -966,6 +966,9 @@ start_here_multiplatform:
>   	 * and SLB setup before we turn on relocation.
>   	 */
>   
> +#ifdef CONFIG_KASAN
> +	bl	kasan_early_init
> +#endif
>   	/* Restore parameters passed from prom_init/kexec */
>   	mr	r3,r31
>   	bl	early_setup		/* also sets r13 and SPRG_PACA */
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index ba404dd9ce1d..d2bf860dd966 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -311,6 +311,16 @@ void __init early_setup(unsigned long dt_ptr)
>    	DBG(" -> early_setup(), dt_ptr: 0x%lx\n", dt_ptr);
>   
>   	/*
> +	 * Configure exception handlers. This include setting up trampolines
> +	 * if needed, setting exception endian mode, etc...
> +	 */
> +	configure_exceptions();
> +
> +	/* Apply all the dynamic patching */
> +	apply_feature_fixups();
> +	setup_feature_keys();
> +
> +	/*
>   	 * Do early initialization using the flattened device
>   	 * tree, such as retrieving the physical memory map or
>   	 * calculating/retrieving the hash table size.
> @@ -325,16 +335,6 @@ void __init early_setup(unsigned long dt_ptr)
>   	setup_paca(paca_ptrs[boot_cpuid]);
>   	fixup_boot_paca();
>   
> -	/*
> -	 * Configure exception handlers. This include setting up trampolines
> -	 * if needed, setting exception endian mode, etc...
> -	 */
> -	configure_exceptions();
> -
> -	/* Apply all the dynamic patching */
> -	apply_feature_fixups();
> -	setup_feature_keys();
> -
>   	/* Initialize the hash table or TLB handling */
>   	early_init_mmu();
>   
> diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
> index 6577897673dd..0bfbe3892808 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_PPC64)	+= kasan_init_64.o
> diff --git a/arch/powerpc/mm/kasan/kasan_init_64.c b/arch/powerpc/mm/kasan/kasan_init_64.c
> new file mode 100644
> index 000000000000..7fd71b8e883b
> --- /dev/null
> +++ b/arch/powerpc/mm/kasan/kasan_init_64.c
> @@ -0,0 +1,129 @@
> +// 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>
> +
> +static void __init kasan_populate_pte(pte_t *ptep, pgprot_t prot)
> +{
> +	unsigned long va = (unsigned long)kasan_early_shadow_page;
> +	phys_addr_t pa = __pa(kasan_early_shadow_page);
> +	int i;
> +
> +	for (i = 0; i < PTRS_PER_PTE; i++, ptep++)
> +		__set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 0);
> +}
> +
> +static void __init kasan_populate_pmd(pmd_t *pmdp)
> +{
> +	int i;
> +
> +	for (i = 0; i < PTRS_PER_PMD; i++)
> +		pmd_populate_kernel(&init_mm, pmdp + i, kasan_early_shadow_pte);
> +}
> +
> +static void __init kasan_populate_pud(pud_t *pudp)
> +{
> +	int i;
> +
> +	for (i = 0; i < PTRS_PER_PUD; i++)
> +		pud_populate(&init_mm, pudp + i, kasan_early_shadow_pmd);
> +}
> +
> +static void __init *kasan_alloc_pgtable(unsigned long size)
> +{
> +	void *ptr = memblock_alloc_try_nid(size, size, MEMBLOCK_LOW_LIMIT,
> +					   __pa(MAX_DMA_ADDRESS), NUMA_NO_NODE);
> +
> +	if (!ptr)
> +		panic("%s: Failed to allocate %lu bytes align=0x%lx max_addr=%lx\n",
> +		      __func__, size, size, __pa(MAX_DMA_ADDRESS));
> +
> +	return ptr;
> +}
> +
> +static int __init kasan_map_page(unsigned long va, unsigned long pa, pgprot_t prot)
> +{
> +	pgd_t *pgdp = pgd_offset_k(va);
> +	pud_t *pudp;
> +	pmd_t *pmdp;
> +	pte_t *ptep;
> +
> +	if (pgd_none(*pgdp) || (void *)pgd_page_vaddr(*pgdp) == kasan_early_shadow_pud) {
> +		pudp = kasan_alloc_pgtable(PUD_TABLE_SIZE);
> +		kasan_populate_pud(pudp);
> +		pgd_populate(&init_mm, pgdp, pudp);
> +	}
> +	pudp = pud_offset(pgdp, va);
> +	if (pud_none(*pudp) || (void *)pud_page_vaddr(*pudp) == kasan_early_shadow_pmd) {
> +		pmdp = kasan_alloc_pgtable(PMD_TABLE_SIZE);
> +		kasan_populate_pmd(pmdp);
> +		pud_populate(&init_mm, pudp, pmdp);
> +	}
> +	pmdp = pmd_offset(pudp, va);
> +	if (!pmd_present(*pmdp) || (void *)pmd_page_vaddr(*pmdp) == kasan_early_shadow_pte) {
> +		ptep = kasan_alloc_pgtable(PTE_TABLE_SIZE);
> +		kasan_populate_pte(ptep, PAGE_KERNEL);
> +		pmd_populate_kernel(&init_mm, pmdp, ptep);
> +	}
> +	ptep = pte_offset_kernel(pmdp, va);
> +
> +	__set_pte_at(&init_mm, va, ptep, pfn_pte(pa >> PAGE_SHIFT, prot), 0);
> +
> +	return 0;
> +}
> +
> +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);
> +
> +		kasan_map_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);
> +
> +	/* It's too early to use clear_page() ! */
> +	memset(kasan_early_shadow_page, 0, sizeof(kasan_early_shadow_page));
> +
> +	/* Enable error messages */
> +	init_task.kasan_depth = 0;
> +	pr_info("KASAN init done\n");
> +}
> +
> +/* The early shadow maps everything to a single page of zeroes */
> +asmlinkage void __init kasan_early_init(void)
> +{
> +	unsigned long addr = KASAN_SHADOW_START;
> +	unsigned long end = KASAN_SHADOW_END;
> +	pgd_t *pgdp = pgd_offset_k(addr);
> +
> +	kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL);
> +	kasan_populate_pmd(kasan_early_shadow_pmd);
> +	kasan_populate_pud(kasan_early_shadow_pud);
> +
> +	do {
> +		pgd_populate(&init_mm, pgdp, kasan_early_shadow_pud);
> +	} while (pgdp++, addr = pgd_addr_end(addr, end), addr != end);
> +}
>