powerpc/32s: set up an early static hash table for KASAN.

KASAN requires early activation of hash table, before memblock()
functions are available.

This patch implements an early hash_table statically defined in
__initdata.

During early boot, a single page table is used.

For hash32, when doing the final init, one page table is allocated
for each PGD entry because of the _PAGE_HASHPTE flag which can't be
common to several virt pages. This is done after memblock get
available but before switching to the final hash table, otherwise
there are issues with TLB flushing due to the shared entries.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 22 insertions, 1 deletions

diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
index 42617fcad828..ba8361487075 100644
--- a/arch/powerpc/mm/kasan/kasan_init_32.c
+++ b/arch/powerpc/mm/kasan/kasan_init_32.c
@@ -94,6 +94,13 @@ void __init kasan_mmu_init(void)
 	int ret;
 	struct memblock_region *reg;
 
+	if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE)) {
+		ret = kasan_init_shadow_page_tables(KASAN_SHADOW_START, KASAN_SHADOW_END);
+
+		if (ret)
+			panic("kasan: kasan_init_shadow_page_tables() failed");
+	}
+
 	for_each_memblock(memory, reg) {
 		phys_addr_t base = reg->base;
 		phys_addr_t top = min(base + reg->size, total_lowmem);
@@ -135,6 +142,20 @@ void *module_alloc(unsigned long size)
 }
 #endif
 
+#ifdef CONFIG_PPC_BOOK3S_32
+u8 __initdata early_hash[256 << 10] __aligned(256 << 10) = {0};
+
+static void __init kasan_early_hash_table(void)
+{
+	modify_instruction_site(&patch__hash_page_A0, 0xffff, __pa(early_hash) >> 16);
+	modify_instruction_site(&patch__flush_hash_A0, 0xffff, __pa(early_hash) >> 16);
+
+	Hash = (struct hash_pte *)early_hash;
+}
+#else
+static void __init kasan_early_hash_table(void) {}
+#endif
+
 void __init kasan_early_init(void)
 {
 	unsigned long addr = KASAN_SHADOW_START;
@@ -152,5 +173,5 @@ void __init kasan_early_init(void)
 	} while (pmd++, addr = next, addr != end);
 
 	if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE))
-		WARN(true, "KASAN not supported on hash 6xx");
+		kasan_early_hash_table();
 }