linux-kernel - Re: [PATCH v3 2/2] riscv: Cleanup KASAN

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Date:   Mon, 29 Mar 2021 22:06:30 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     alex@...ti.fr
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        nylon7@...estech.com, nickhu@...estech.com,
        aryabinin@...tuozzo.com, glider@...gle.com, dvyukov@...gle.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, alex@...ti.fr
Subject:     Re: [PATCH v3 2/2] riscv: Cleanup KASAN_VMALLOC support

On Sat, 13 Mar 2021 00:45:05 PST (-0800), alex@...ti.fr wrote:
> When KASAN vmalloc region is populated, there is no userspace process and
> the page table in use is swapper_pg_dir, so there is no need to read
> SATP. Then we can use the same scheme used by kasan_populate_p*d
> functions to go through the page table, which harmonizes the code.
>
> In addition, make use of set_pgd that goes through all unused page table
> levels, contrary to p*d_populate functions, which makes this function work
> whatever the number of page table levels.
>
> Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
> Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
> ---
>  arch/riscv/mm/kasan_init.c | 59 ++++++++++++--------------------------
>  1 file changed, 18 insertions(+), 41 deletions(-)
>
> diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
> index 57bf4ae09361..c16178918239 100644
> --- a/arch/riscv/mm/kasan_init.c
> +++ b/arch/riscv/mm/kasan_init.c
> @@ -11,18 +11,6 @@
>  #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)
>  {
> @@ -155,38 +143,27 @@ static void __init kasan_populate(void *start, void *end)
>  	memset(start, KASAN_SHADOW_INIT, end - start);
>  }
>
> -void __init kasan_shallow_populate(void *start, void *end)
> +static void __init kasan_shallow_populate_pgd(unsigned long vaddr, unsigned long end)
>  {
> -	unsigned long vaddr = (unsigned long)start & PAGE_MASK;
> -	unsigned long vend = PAGE_ALIGN((unsigned long)end);
> -	unsigned long pfn;
> -	int index;
> +	unsigned long next;
>  	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);
> +	pgd_t *pgd_k = pgd_offset_k(vaddr);
> +
> +	do {
> +		next = pgd_addr_end(vaddr, end);
> +		if (pgd_page_vaddr(*pgd_k) == (unsigned long)lm_alias(kasan_early_shadow_pmd)) {
> +			p = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> +			set_pgd(pgd_k, pfn_pgd(PFN_DOWN(__pa(p)), PAGE_TABLE));
>  		}
> -		vaddr += PAGE_SIZE;
> -	}
> +	} while (pgd_k++, vaddr = next, vaddr != end);
> +}
> +
> +static 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);
> +
> +	kasan_shallow_populate_pgd(vaddr, vend);
>
>  	local_flush_tlb_all();
>  }

Thanks, this is on for-next.