riscv: Split early kasan mapping to prepare sv48 introduction

Now that kasan shadow region is next to the kernel, for sv48, this
region won't be aligned on PGDIR_SIZE and then when populating this
region, we'll need to get down to lower levels of the page table. So
instead of reimplementing the page table walk for the early population,
take advantage of the existing functions used for the final population.

Note that kasan swapper initialization must also be split since memblock
is not initialized at this point and as the last PGD is shared with the
kernel, we'd need to allocate a PUD so postpone the kasan final
population after the kernel population is done.

Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

3 files changed, 67 insertions, 51 deletions

diff --git a/arch/riscv/include/asm/kasan.h b/arch/riscv/include/asm/kasan.h
index 257a2495145a..2788e2c46609 100644
--- a/arch/riscv/include/asm/kasan.h
+++ b/arch/riscv/include/asm/kasan.h
@@ -34,6 +34,7 @@
 
 void kasan_init(void);
 asmlinkage void kasan_early_init(void);
+void kasan_swapper_init(void);
 
 #endif
 #endif
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index f515964e9c00..f5d0052c95ad 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -741,6 +741,10 @@ static void __init setup_vm_final(void)
 	create_kernel_page_table(swapper_pg_dir, false);
 #endif
 
+#ifdef CONFIG_KASAN
+	kasan_swapper_init();
+#endif
+
 	/* Clear fixmap PTE and PMD mappings */
 	clear_fixmap(FIX_PTE);
 	clear_fixmap(FIX_PMD);
diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
index 54294f83513d..1434a0225140 100644
--- a/arch/riscv/mm/kasan_init.c
+++ b/arch/riscv/mm/kasan_init.c
@@ -12,44 +12,6 @@
 #include <asm/pgalloc.h>
 
 extern pgd_t early_pg_dir[PTRS_PER_PGD];
-asmlinkage void __init kasan_early_init(void)
-{
-	uintptr_t i;
-	pgd_t *pgd = early_pg_dir + pgd_index(KASAN_SHADOW_START);
-
-	BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
-		KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
-
-	for (i = 0; i < PTRS_PER_PTE; ++i)
-		set_pte(kasan_early_shadow_pte + i,
-			mk_pte(virt_to_page(kasan_early_shadow_page),
-			       PAGE_KERNEL));
-
-	for (i = 0; i < PTRS_PER_PMD; ++i)
-		set_pmd(kasan_early_shadow_pmd + i,
-			pfn_pmd(PFN_DOWN
-				(__pa((uintptr_t) kasan_early_shadow_pte)),
-				__pgprot(_PAGE_TABLE)));
-
-	for (i = KASAN_SHADOW_START; i < KASAN_SHADOW_END;
-	     i += PGDIR_SIZE, ++pgd)
-		set_pgd(pgd,
-			pfn_pgd(PFN_DOWN
-				(__pa(((uintptr_t) kasan_early_shadow_pmd))),
-				__pgprot(_PAGE_TABLE)));
-
-	/* init for swapper_pg_dir */
-	pgd = pgd_offset_k(KASAN_SHADOW_START);
-
-	for (i = KASAN_SHADOW_START; i < KASAN_SHADOW_END;
-	     i += PGDIR_SIZE, ++pgd)
-		set_pgd(pgd,
-			pfn_pgd(PFN_DOWN
-				(__pa(((uintptr_t) kasan_early_shadow_pmd))),
-				__pgprot(_PAGE_TABLE)));
-
-	local_flush_tlb_all();
-}
 
 static void __init kasan_populate_pte(pmd_t *pmd, unsigned long vaddr, unsigned long end)
 {
@@ -108,26 +70,35 @@ static void __init kasan_populate_pmd(pgd_t *pgd, unsigned long vaddr, unsigned
 	set_pgd(pgd, pfn_pgd(PFN_DOWN(__pa(base_pmd)), PAGE_TABLE));
 }
 
-static void __init kasan_populate_pgd(unsigned long vaddr, unsigned long end)
+static void __init kasan_populate_pgd(pgd_t *pgdp,
+				      unsigned long vaddr, unsigned long end,
+				      bool early)
 {
 	phys_addr_t phys_addr;
-	pgd_t *pgdp = pgd_offset_k(vaddr);
 	unsigned long next;
 
 	do {
 		next = pgd_addr_end(vaddr, end);
 
-		/*
-		 * pgdp can't be none since kasan_early_init initialized all KASAN
-		 * shadow region with kasan_early_shadow_pmd: if this is stillthe case,
-		 * that means we can try to allocate a hugepage as a replacement.
-		 */
-		if (pgd_page_vaddr(*pgdp) == (unsigned long)lm_alias(kasan_early_shadow_pmd) &&
-		    IS_ALIGNED(vaddr, PGDIR_SIZE) && (next - vaddr) >= PGDIR_SIZE) {
-			phys_addr = memblock_phys_alloc(PGDIR_SIZE, PGDIR_SIZE);
-			if (phys_addr) {
-				set_pgd(pgdp, pfn_pgd(PFN_DOWN(phys_addr), PAGE_KERNEL));
+		if (IS_ALIGNED(vaddr, PGDIR_SIZE) && (next - vaddr) >= PGDIR_SIZE) {
+			if (early) {
+				phys_addr = __pa((uintptr_t)kasan_early_shadow_pgd_next);
+				set_pgd(pgdp, pfn_pgd(PFN_DOWN(phys_addr), PAGE_TABLE));
 				continue;
+			} else if (pgd_page_vaddr(*pgdp) ==
+				   (unsigned long)lm_alias(kasan_early_shadow_pgd_next)) {
+				/*
+				 * pgdp can't be none since kasan_early_init
+				 * initialized all KASAN shadow region with
+				 * kasan_early_shadow_pud: if this is still the
+				 * case, that means we can try to allocate a
+				 * hugepage as a replacement.
+				 */
+				phys_addr = memblock_phys_alloc(PGDIR_SIZE, PGDIR_SIZE);
+				if (phys_addr) {
+					set_pgd(pgdp, pfn_pgd(PFN_DOWN(phys_addr), PAGE_KERNEL));
+					continue;
+				}
 			}
 		}
 
@@ -135,12 +106,52 @@ static void __init kasan_populate_pgd(unsigned long vaddr, unsigned long end)
 	} while (pgdp++, vaddr = next, vaddr != end);
 }
 
+asmlinkage void __init kasan_early_init(void)
+{
+	uintptr_t i;
+
+	BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
+		KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
+
+	for (i = 0; i < PTRS_PER_PTE; ++i)
+		set_pte(kasan_early_shadow_pte + i,
+			mk_pte(virt_to_page(kasan_early_shadow_page),
+			       PAGE_KERNEL));
+
+	for (i = 0; i < PTRS_PER_PMD; ++i)
+		set_pmd(kasan_early_shadow_pmd + i,
+			pfn_pmd(PFN_DOWN
+				(__pa((uintptr_t)kasan_early_shadow_pte)),
+				PAGE_TABLE));
+
+	if (pgtable_l4_enabled) {
+		for (i = 0; i < PTRS_PER_PUD; ++i)
+			set_pud(kasan_early_shadow_pud + i,
+				pfn_pud(PFN_DOWN
+					(__pa(((uintptr_t)kasan_early_shadow_pmd))),
+					PAGE_TABLE));
+	}
+
+	kasan_populate_pgd(early_pg_dir + pgd_index(KASAN_SHADOW_START),
+			   KASAN_SHADOW_START, KASAN_SHADOW_END, true);
+
+	local_flush_tlb_all();
+}
+
+void __init kasan_swapper_init(void)
+{
+	kasan_populate_pgd(pgd_offset_k(KASAN_SHADOW_START),
+			   KASAN_SHADOW_START, KASAN_SHADOW_END, true);
+
+	local_flush_tlb_all();
+}
+
 static void __init kasan_populate(void *start, void *end)
 {
 	unsigned long vaddr = (unsigned long)start & PAGE_MASK;
 	unsigned long vend = PAGE_ALIGN((unsigned long)end);
 
-	kasan_populate_pgd(vaddr, vend);
+	kasan_populate_pgd(pgd_offset_k(vaddr), vaddr, vend, false);
 
 	local_flush_tlb_all();
 	memset(start, KASAN_SHADOW_INIT, end - start);