riscv/kasan: add KASAN_VMALLOC support

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.

Signed-off-by: Nylon Chen <nylon7@andestech.com>
Signed-off-by: Nick Hu <nickhu@andestech.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

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

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)
@@ -83,14 +96,56 @@ 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;
+		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);
+		}
+		vaddr += PAGE_SIZE;
+	}
+}
+
 void __init kasan_init(void)
 {
 	phys_addr_t _start, _end;
 	u64 i;
 
 	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;