linux-kernel - Re: [PATCH] riscv: Add KASAN

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Date:   Thu, 25 Feb 2021 21:32:10 -0800 (PST)
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
Subject:     Re: [PATCH] riscv: Add KASAN_VMALLOC support

On Wed, 24 Feb 2021 23:48:13 PST (-0800), alex@...ti.fr wrote:
> Le 2/25/21 à 2:42 AM, Alexandre Ghiti a écrit :
>> Populate the top-level of the kernel page table to implement KASAN_VMALLOC,
>> lower levels are filled dynamically upon memory allocation at runtime.
>>
>> Co-developed-by: Nylon Chen <nylon7@...estech.com>
>> Signed-off-by: Nylon Chen <nylon7@...estech.com>
>> Co-developed-by: Nick Hu <nickhu@...estech.com>
>> Signed-off-by: Nick Hu <nickhu@...estech.com>
>> Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
>> ---
>>   arch/riscv/Kconfig         |  1 +
>>   arch/riscv/mm/kasan_init.c | 35 ++++++++++++++++++++++++++++++++++-
>>   2 files changed, 35 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 8eadd1cbd524..3832a537c5d6 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 719b6e4d6075..171569df4334 100644
>> --- a/arch/riscv/mm/kasan_init.c
>> +++ b/arch/riscv/mm/kasan_init.c
>> @@ -142,6 +142,31 @@ static void __init kasan_populate(void *start, void *end)
>>   	memset(start, KASAN_SHADOW_INIT, end - start);
>>   }
>>
>> +void __init kasan_shallow_populate_pgd(unsigned long vaddr, unsigned long end)
>> +{
>> +	unsigned long next;
>> +	void *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));
>> +		}
>> +	} while (pgd_k++, vaddr = next, vaddr != end);
>> +}
>> +
>> +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();
>> +}
>> +
>>   void __init kasan_init(void)
>>   {
>>   	phys_addr_t _start, _end;
>> @@ -149,7 +174,15 @@ 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;
>>
>
> Palmer, this commit should replace (if everyone agrees) Nylon and Nick's
> Commit e178d670f251 ("riscv/kasan: add KASAN_VMALLOC support") that is
> already in for-next.

Sorry, but it's way too late to be rebasing things.  I can get trying to have
the history clean, but in this case we're better off having this as an explicit
fix patch -- changing hashes this late in the process messes with all the
testing.

I'm not sure what the issue actually is, so it'd be great if you could send the
fix patch.  If not then LMK and I'll try to figure out what's going on.  Either
way, having the fix will make sure this gets tested properly as whatever's
going on isn't failing for me.