[PATCH v8 11/11] powerpc/32s: set up an early static hash table for KASAN.

[Christophe Leroy]

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.

Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
---
 arch/powerpc/kernel/head_32.S         | 40 ++++++++++++++++++++++++++---------
 arch/powerpc/mm/kasan/kasan_init_32.c | 32 ++++++++++++++++++++++++----
 arch/powerpc/mm/mmu_decl.h            |  1 +
 3 files changed, 59 insertions(+), 14 deletions(-)

diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index e644aab2cf5b..65c9e8819da1 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -160,6 +160,10 @@ __after_mmu_off:
 	bl	flush_tlbs
 
 	bl	initial_bats
+	bl	load_segment_registers
+#ifdef CONFIG_KASAN
+	bl	early_hash_table
+#endif
 #if defined(CONFIG_BOOTX_TEXT)
 	bl	setup_disp_bat
 #endif
@@ -205,7 +209,7 @@ __after_mmu_off:
  */
 turn_on_mmu:
 	mfmsr	r0
-	ori	r0,r0,MSR_DR|MSR_IR
+	ori	r0,r0,MSR_DR|MSR_IR|MSR_RI
 	mtspr	SPRN_SRR1,r0
 	lis	r0,start_here at h
 	ori	r0,r0,start_here at l
@@ -881,11 +885,24 @@ _ENTRY(__restore_cpu_setup)
 	blr
 #endif /* !defined(CONFIG_PPC_BOOK3S_32) */
 
-
 /*
  * Load stuff into the MMU.  Intended to be called with
  * IR=0 and DR=0.
  */
+#ifdef CONFIG_KASAN
+early_hash_table:
+	sync			/* Force all PTE updates to finish */
+	isync
+	tlbia			/* Clear all TLB entries */
+	sync			/* wait for tlbia/tlbie to finish */
+	TLBSYNC			/* ... on all CPUs */
+	/* Load the SDR1 register (hash table base & size) */
+	lis	r6, early_hash - PAGE_OFFSET at h
+	ori	r6, r6, 3	/* 256kB table */
+	mtspr	SPRN_SDR1, r6
+	blr
+#endif
+
 load_up_mmu:
 	sync			/* Force all PTE updates to finish */
 	isync
@@ -897,14 +914,6 @@ load_up_mmu:
 	tophys(r6,r6)
 	lwz	r6,_SDR1 at l(r6)
 	mtspr	SPRN_SDR1,r6
-	li	r0,16		/* load up segment register values */
-	mtctr	r0		/* for context 0 */
-	lis	r3,0x2000	/* Ku = 1, VSID = 0 */
-	li	r4,0
-3:	mtsrin	r3,r4
-	addi	r3,r3,0x111	/* increment VSID */
-	addis	r4,r4,0x1000	/* address of next segment */
-	bdnz	3b
 
 /* Load the BAT registers with the values set up by MMU_init.
    MMU_init takes care of whether we're on a 601 or not. */
@@ -926,6 +935,17 @@ BEGIN_MMU_FTR_SECTION
 END_MMU_FTR_SECTION_IFSET(MMU_FTR_USE_HIGH_BATS)
 	blr
 
+load_segment_registers:
+	li	r0, 16		/* load up segment register values */
+	mtctr	r0		/* for context 0 */
+	lis	r3, 0x2000	/* Ku = 1, VSID = 0 */
+	li	r4, 0
+3:	mtsrin	r3, r4
+	addi	r3, r3, 0x111	/* increment VSID */
+	addis	r4, r4, 0x1000	/* address of next segment */
+	bdnz	3b
+	blr
+
 /*
  * This is where the main kernel code starts.
  */
diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
index 42f8534ce3ea..8c25c1e8c2c8 100644
--- a/arch/powerpc/mm/kasan/kasan_init_32.c
+++ b/arch/powerpc/mm/kasan/kasan_init_32.c
@@ -60,10 +60,13 @@ static int __ref kasan_init_region(void *start, size_t size)
 	unsigned long k_cur;
 	pmd_t *pmd;
 	void *block = NULL;
-	int ret = kasan_init_shadow_page_tables(k_start, k_end);
 
-	if (ret)
-		return ret;
+	if (!early_mmu_has_feature(MMU_FTR_HPTE_TABLE)) {
+		int ret = kasan_init_shadow_page_tables(k_start, k_end);
+
+		if (ret)
+			return ret;
+	}
 
 	if (!slab_is_available())
 		block = memblock_alloc(k_end - k_start, PAGE_SIZE);
@@ -94,6 +97,13 @@ void __init kasan_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);
@@ -132,6 +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;
@@ -149,5 +173,5 @@ void __init kasan_early_init(void)
 	} while (pmd++, addr = next, addr != end);
 
 	if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE))
-		WARN(1, "KASAN not supported on hash 6xx");
+		kasan_early_hash_table();
 }
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index d726ff776054..31fce3914ddc 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -106,6 +106,7 @@ extern unsigned int rtas_data, rtas_size;
 struct hash_pte;
 extern struct hash_pte *Hash, *Hash_end;
 extern unsigned long Hash_size, Hash_mask;
+extern u8 early_hash[];
 
 #endif /* CONFIG_PPC32 */
 
-- 
2.13.3