[PATCH v2 1/1] riscv/kasan: add KASAN_VMALLOC support
Alex Ghiti
alex at ghiti.fr
Wed Feb 24 14:11:07 EST 2021
Hi Nylon,
Le 2/22/21 à 12:13 PM, Alex Ghiti a écrit :
> Le 2/21/21 à 8:37 PM, Nylon Chen a écrit :
>> Hi Alex, Palmer
>>
>> Sorry I missed this message.
>> On Sun, Feb 21, 2021 at 09:38:04PM +0800, Alex Ghiti wrote:
>>> Le 2/13/21 à 5:52 AM, Alex Ghiti a écrit :
>>>> Hi Nylon, Palmer,
>>>>
>>>> Le 2/8/21 à 1:28 AM, Alex Ghiti a écrit :
>>>>> Hi Nylon,
>>>>>
>>>>> Le 1/22/21 à 10:56 PM, Palmer Dabbelt a écrit :
>>>>>> On Fri, 15 Jan 2021 21:58:35 PST (-0800), nylon7 at andestech.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.
>>>>>
>>>>> I think we can improve the changelog a bit here with something like
>>>>> that:
>>>>>
>>>>> "KASAN vmalloc space used to be mapped using kasan early shadow page.
>>>>> KASAN_VMALLOC requires the top-level of the kernel page table to be
>>>>> properly populated, lower levels being filled dynamically upon memory
>>>>> allocation at runtime."
>>>>>
>>>>>>>
>>>>>>> Signed-off-by: Nylon Chen <nylon7 at andestech.com>
>>>>>>> Signed-off-by: Nick Hu <nickhu at andestech.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;
>>>>>
>>>>> At this point in the boot process, we know that we use swapper_pg_dir
>>>>> so no need to read SATP.
>>>>>
>>>>>>> + pgd_dir = (pgd_t *)pfn_to_virt(pfn) + index;
>>>>>
>>>>> Here, this pgd_dir assignment is overwritten 2 lines below, so no need
>>>>> for it.
>>>>>
>>>>>>> + pgd_k = init_mm.pgd + index;
>>>>>>> + pgd_dir = pgd_offset_k(vaddr);
>>>>>
>>>>> pgd_offset_k(vaddr) = init_mm.pgd + pgd_index(vaddr) so pgd_k ==
>>>>> pgd_dir.
>>>>>
>>>>>>> + 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;
>>>>>
>>>>> Why do you increase vaddr *before* populating the first one ? And
>>>>> pud_addr_end does that properly: it returns the next pud address if it
>>>>> does not go beyond end address to map.
>>>>>
>>>>>>> + 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);
>>>>>
>>>>> init_mm is not needed here.
>>>>>
>>>>>>> + }
>>>>>>> + vaddr += PAGE_SIZE;
>>>>>
>>>>> Why do you need to add PAGE_SIZE ? vaddr already points to the next
>>>>> pud.
>>>>>
>>>>> It seems like this patch tries to populate userspace page table
>>>>> whereas at this point in the boot process, only swapper_pg_dir is used
>>>>> or am I missing something ?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Alex
>>>>
>>>> I implemented this morning a version that fixes all the comments I made
>>>> earlier. I was able to insert test_kasan_module on both sv39 and sv48
>>>> without any modification: set_pgd "goes through" all the unused page
>>>> table levels, whereas p*d_populate are noop for unused levels.
>>>>
>>>> If you have any comment, do not hesitate.
>>>>
>>>> diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
>>>> index adbf94b7e68a..d643b222167c 100644
>>>> --- a/arch/riscv/mm/kasan_init.c
>>>> +++ b/arch/riscv/mm/kasan_init.c
>>>> @@ -195,6 +195,31 @@ 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_pgd_next)) {
>>>> + 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);
>>>> +}
>>>> +
>>>
>>> This way of going through the page table seems to be largely used across
>>> the kernel (cf KASAN population functions of arm64/x86) so I do think
>>> this patch brings value to Nylon and Nick's patch.
>>>
>>> I can propose a real patch if you agree and I'll add a co-developed by
>>> Nylon/Nick since this only 'improves' theirs.
>>>
>>> Thanks,
>>>
>>> Alex
>>>
>> I agree with your proposal, but when I try your patch that it dosen't
>> work
>> because `kasan_early_shadow_pgd_next` function wasn't define.
>
> Oops, I messed up my rebase, please replace
> 'kasan_early_shadow_pgd_next' with 'kasan_early_shadow_pmd'.
>
> Thank you for your feeback,
>
> Alex
>
Did you have time to test the above fix ? It would be nice to replace
your current patch with the above solution before it gets merged for
5.12, I will propose something tomorrow, feel free to review and test :)
Thanks again,
Alex
>>
>> Do you have complete patch? or just I missed some content?
>>>> +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;
>>>> @@ -206,7 +231,15 @@ 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));
>>>>
>>>>
>>>> /* Populate the linear mapping */
>>>> for_each_mem_range(i, &_start, &_end) {
>>
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