linux-kernel - Re: [PATCH v2 1/1] riscv/kasan: add KASAN

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Date:   Fri, 22 Jan 2021 19:56:41 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     nylon7@...estech.com
CC:     linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        kasan-dev@...glegroups.com,
        Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, aryabinin@...tuozzo.com, glider@...gle.com,
        dvyukov@...gle.com, nylon7717@...il.com, alankao@...estech.com,
        nickhu@...estech.com, nylon7@...estech.com
Subject:     Re: [PATCH v2 1/1] riscv/kasan: add KASAN_VMALLOC support

On Fri, 15 Jan 2021 21:58:35 PST (-0800), nylon7@...estech.com wrote:
> It references to x86/s390 architecture.
>
> So, it doesn't map the early shadow page to cover VMALLOC space.
>
> Prepopulate top level page table for the range that would otherwise be
> empty.
>
> lower levels are filled dynamically upon memory allocation while
> booting.
>
> Signed-off-by: Nylon Chen <nylon7@...estech.com>
> Signed-off-by: Nick Hu <nickhu@...estech.com>
> ---
>  arch/riscv/Kconfig         |  1 +
>  arch/riscv/mm/kasan_init.c | 57 +++++++++++++++++++++++++++++++++++++-
>  2 files changed, 57 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 81b76d44725d..15a2c8088bbe 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -57,6 +57,7 @@ config RISCV
>  	select HAVE_ARCH_JUMP_LABEL
>  	select HAVE_ARCH_JUMP_LABEL_RELATIVE
>  	select HAVE_ARCH_KASAN if MMU && 64BIT
> +	select HAVE_ARCH_KASAN_VMALLOC if MMU && 64BIT
>  	select HAVE_ARCH_KGDB
>  	select HAVE_ARCH_KGDB_QXFER_PKT
>  	select HAVE_ARCH_MMAP_RND_BITS if MMU
> diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
> index 12ddd1f6bf70..4b9149f963d3 100644
> --- a/arch/riscv/mm/kasan_init.c
> +++ b/arch/riscv/mm/kasan_init.c
> @@ -9,6 +9,19 @@
>  #include <linux/pgtable.h>
>  #include <asm/tlbflush.h>
>  #include <asm/fixmap.h>
> +#include <asm/pgalloc.h>
> +
> +static __init void *early_alloc(size_t size, int node)
> +{
> +	void *ptr = memblock_alloc_try_nid(size, size,
> +		__pa(MAX_DMA_ADDRESS), MEMBLOCK_ALLOC_ACCESSIBLE, node);
> +
> +	if (!ptr)
> +		panic("%pS: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
> +			__func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
> +
> +	return ptr;
> +}
>
>  extern pgd_t early_pg_dir[PTRS_PER_PGD];
>  asmlinkage void __init kasan_early_init(void)
> @@ -83,6 +96,40 @@ static void __init populate(void *start, void *end)
>  	memset(start, 0, end - start);
>  }
>
> +void __init kasan_shallow_populate(void *start, void *end)
> +{
> +	unsigned long vaddr = (unsigned long)start & PAGE_MASK;
> +	unsigned long vend = PAGE_ALIGN((unsigned long)end);
> +	unsigned long pfn;
> +	int index;
> +	void *p;
> +	pud_t *pud_dir, *pud_k;
> +	pgd_t *pgd_dir, *pgd_k;
> +	p4d_t *p4d_dir, *p4d_k;
> +
> +	while (vaddr < vend) {
> +		index = pgd_index(vaddr);
> +		pfn = csr_read(CSR_SATP) & SATP_PPN;
> +		pgd_dir = (pgd_t *)pfn_to_virt(pfn) + index;
> +		pgd_k = init_mm.pgd + index;
> +		pgd_dir = pgd_offset_k(vaddr);
> +		set_pgd(pgd_dir, *pgd_k);
> +
> +		p4d_dir = p4d_offset(pgd_dir, vaddr);
> +		p4d_k  = p4d_offset(pgd_k, vaddr);
> +
> +		vaddr = (vaddr + PUD_SIZE) & PUD_MASK;
> +		pud_dir = pud_offset(p4d_dir, vaddr);
> +		pud_k = pud_offset(p4d_k, vaddr);
> +
> +		if (pud_present(*pud_dir)) {
> +			p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
> +			pud_populate(&init_mm, pud_dir, p);
> +		}
> +		vaddr += PAGE_SIZE;
> +	}
> +}
> +
>  void __init kasan_init(void)
>  {
>  	phys_addr_t _start, _end;
> @@ -90,7 +137,15 @@ void __init kasan_init(void)
>
>  	kasan_populate_early_shadow((void *)KASAN_SHADOW_START,
>  				    (void *)kasan_mem_to_shadow((void *)
> -								VMALLOC_END));
> +								VMEMMAP_END));
> +	if (IS_ENABLED(CONFIG_KASAN_VMALLOC))
> +		kasan_shallow_populate(
> +			(void *)kasan_mem_to_shadow((void *)VMALLOC_START),
> +			(void *)kasan_mem_to_shadow((void *)VMALLOC_END));
> +	else
> +		kasan_populate_early_shadow(
> +			(void *)kasan_mem_to_shadow((void *)VMALLOC_START),
> +			(void *)kasan_mem_to_shadow((void *)VMALLOC_END));
>
>  	for_each_mem_range(i, &_start, &_end) {
>  		void *start = (void *)_start;

Thanks, this is on for-next.