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Subject: Re: [PATCH] riscv: Add KASAN_VMALLOC support
To:     Palmer Dabbelt <palmer@dabbelt.com>
Cc:     aou@eecs.berkeley.edu, nickhu@andestech.com,
        linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
        nylon7@andestech.com, glider@google.com,
        Paul Walmsley <paul.walmsley@sifive.com>,
        aryabinin@virtuozzo.com, linux-riscv@lists.infradead.org,
        dvyukov@google.com
References: <mhng-ea9a6037-0f18-41d5-8c01-6c16b14b6a63@palmerdabbelt-glaptop>
From:   Alex Ghiti <alex@ghiti.fr>
Message-ID: <e3754d1e-f61f-f7d7-b159-52af2817428d@ghiti.fr>
Date:   Fri, 26 Feb 2021 01:14:36 -0500
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Hi Palmer,

Le 2/26/21 à 12:32 AM, Palmer Dabbelt a écrit :
> On Wed, 24 Feb 2021 23:48:13 PST (-0800), alex@ghiti.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@andestech.com>
>>> Signed-off-by: Nylon Chen <nylon7@andestech.com>
>>> Co-developed-by: Nick Hu <nickhu@andestech.com>
>>> Signed-off-by: Nick Hu <nickhu@andestech.com>
>>> Signed-off-by: Alexandre Ghiti <alex@ghiti.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.
> 

Nylon's patch is functional as is, but as I mentioned here 
https://patchwork.kernel.org/project/linux-riscv/patch/20210116055836.22366-2-nylon7@andestech.com/, 
it does unnecessary things (like trying to walk a user page table that 
does not exist at this point in the boot process).

Anyway, I will send another patch rebased on top of Nylon's.

Thanks,

Alex


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