[PATCH] riscv: Add KASAN_VMALLOC support

[Alexandre Ghiti]

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 at andestech.com>
Signed-off-by: Nylon Chen <nylon7 at andestech.com>
Co-developed-by: Nick Hu <nickhu at andestech.com>
Signed-off-by: Nick Hu <nickhu at andestech.com>
Signed-off-by: Alexandre Ghiti <alex at 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;
-- 
2.20.1