[PATCH] powerpc/32s: Fix BATs allocation for KASAN

[Christophe Leroy]

It has been reported some configuration where the kernel doesn't
boot with KASAN enabled.

This is due to wrong BAT allocation for the KASAN area:

	---[ Data Block Address Translation ]---
	0: 0xc0000000-0xcfffffff 0x00000000       256M Kernel rw      m
	1: 0xd0000000-0xdfffffff 0x10000000       256M Kernel rw      m
	2: 0xe0000000-0xefffffff 0x20000000       256M Kernel rw      m
	3: 0xf8000000-0xf9ffffff 0x2a000000        32M Kernel rw      m
	4: 0xfa000000-0xfdffffff 0x2c000000        64M Kernel rw      m

A BAT must have both virtual and physical addresses alignment matching
the size of the BAT. This is not the case for BAT 4 above.

Fix kasan_init_region() by using block_size() function that is in
book3s32/mmu.c. To be able to reuse it here, make it non static and
change its name to bat_block_size() in order to avoid name conflict
with block_size() defined in <linux/blkdev.h>

Also reuse find_free_bat() to avoid an error message from setbat()
when no BAT is available.

With this change we get correct alignment for BATs:

	---[ Data Block Address Translation ]---
	0: 0xc0000000-0xcfffffff 0x00000000       256M Kernel rw
	1: 0xd0000000-0xdfffffff 0x10000000       256M Kernel rw
	2: 0xe0000000-0xefffffff 0x20000000       256M Kernel rw
	3: 0xf8000000-0xfbffffff 0x2c000000        64M Kernel rw
	4: 0xfc000000-0xfdffffff 0x2a000000        32M Kernel rw

Reported-by: Maxime Bizon <mbizon@xxxxxxxxxx>
Fixes: 7974c4732642 ("powerpc/32s: Implement dedicated kasan_init_region()")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
 arch/powerpc/include/asm/book3s/32/mmu-hash.h |  2 +
 arch/powerpc/mm/book3s32/mmu.c                | 10 ++---
 arch/powerpc/mm/kasan/book3s_32.c             | 43 ++++++++++---------
 3 files changed, 29 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/32/mmu-hash.h b/arch/powerpc/include/asm/book3s/32/mmu-hash.h
index f5be185cbdf8..5b45c648a8d9 100644
--- a/arch/powerpc/include/asm/book3s/32/mmu-hash.h
+++ b/arch/powerpc/include/asm/book3s/32/mmu-hash.h
@@ -143,6 +143,8 @@ static __always_inline void update_user_segments(u32 val)
 	update_user_segment(15, val);
 }
 
+int find_free_bat(void);
+unsigned int bat_block_size(unsigned long base, unsigned long top);
 #endif /* !__ASSEMBLY__ */
 
 /* We happily ignore the smaller BATs on 601, we don't actually use
diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
index cb48e4a5106d..9e7714a861bf 100644
--- a/arch/powerpc/mm/book3s32/mmu.c
+++ b/arch/powerpc/mm/book3s32/mmu.c
@@ -76,7 +76,7 @@ unsigned long p_block_mapped(phys_addr_t pa)
 	return 0;
 }
 
-static int find_free_bat(void)
+int find_free_bat(void)
 {
 	int b;
 	int n = mmu_has_feature(MMU_FTR_USE_HIGH_BATS) ? 8 : 4;
@@ -100,7 +100,7 @@ static int find_free_bat(void)
  * - block size has to be a power of two. This is calculated by finding the
  *   highest bit set to 1.
  */
-static unsigned int block_size(unsigned long base, unsigned long top)
+unsigned int bat_block_size(unsigned long base, unsigned long top)
 {
 	unsigned int max_size = SZ_256M;
 	unsigned int base_shift = (ffs(base) - 1) & 31;
@@ -145,7 +145,7 @@ static unsigned long __init __mmu_mapin_ram(unsigned long base, unsigned long to
 	int idx;
 
 	while ((idx = find_free_bat()) != -1 && base != top) {
-		unsigned int size = block_size(base, top);
+		unsigned int size = bat_block_size(base, top);
 
 		if (size < 128 << 10)
 			break;
@@ -204,12 +204,12 @@ void mmu_mark_initmem_nx(void)
 	unsigned long size;
 
 	for (i = 0; i < nb - 1 && base < top && top - base > (128 << 10);) {
-		size = block_size(base, top);
+		size = bat_block_size(base, top);
 		setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT);
 		base += size;
 	}
 	if (base < top) {
-		size = block_size(base, top);
+		size = bat_block_size(base, top);
 		size = max(size, 128UL << 10);
 		if ((top - base) > size) {
 			size <<= 1;
diff --git a/arch/powerpc/mm/kasan/book3s_32.c b/arch/powerpc/mm/kasan/book3s_32.c
index 202bd260a009..c2ff93c63dfa 100644
--- a/arch/powerpc/mm/kasan/book3s_32.c
+++ b/arch/powerpc/mm/kasan/book3s_32.c
@@ -11,32 +11,33 @@ int __init kasan_init_region(void *start, size_t size)
 	unsigned long k_start = (unsigned long)kasan_mem_to_shadow(start);
 	unsigned long k_end = (unsigned long)kasan_mem_to_shadow(start + size);
 	unsigned long k_cur = k_start;
-	int k_size = k_end - k_start;
-	int k_size_base = 1 << (ffs(k_size) - 1);
 	int ret;
 	void *block;
 
-	block = memblock_alloc(k_size, k_size_base);
-
-	if (block && k_size_base >= SZ_128K && k_start == ALIGN(k_start, k_size_base)) {
-		int k_size_more = 1 << (ffs(k_size - k_size_base) - 1);
-
-		setbat(-1, k_start, __pa(block), k_size_base, PAGE_KERNEL);
-		if (k_size_more >= SZ_128K)
-			setbat(-1, k_start + k_size_base, __pa(block) + k_size_base,
-			       k_size_more, PAGE_KERNEL);
-		if (v_block_mapped(k_start))
-			k_cur = k_start + k_size_base;
-		if (v_block_mapped(k_start + k_size_base))
-			k_cur = k_start + k_size_base + k_size_more;
-
-		update_bats();
+	while (k_cur < k_end) {
+		unsigned int k_size = bat_block_size(k_cur, k_end);
+		phys_addr_t phys;
+		int idx = find_free_bat();
+
+		if (idx == -1)
+			break;
+		if (k_size < SZ_128K)
+			break;
+		phys = memblock_phys_alloc(k_size, k_size);
+		if (!phys)
+			break;
+
+		setbat(idx, k_cur, phys, k_size, PAGE_KERNEL);
+		k_cur += k_size;
 	}
+	if (k_cur != k_start)
+		update_bats();
 
-	if (!block)
-		block = memblock_alloc(k_size, PAGE_SIZE);
-	if (!block)
-		return -ENOMEM;
+	if (k_cur < k_end) {
+		block = memblock_alloc(k_end - k_cur, PAGE_SIZE);
+		if (!block)
+			return -ENOMEM;
+	}
 
 	ret = kasan_init_shadow_page_tables(k_start, k_end);
 	if (ret)
-- 
2.33.1