[PATCH v2 1/1] riscv/kasan: add KASAN_VMALLOC support
Alex Ghiti
alex at ghiti.fr
Sat Feb 13 05:52:36 EST 2021
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);
+}
+
+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) {
--
2.20.1
Thanks,
Alex
>
>>> + }
>>> +}
>>> +
>>> 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.
>>
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>
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