powerpc/32s: Implement dedicated kasan_init_region()

Implement a kasan_init_region() dedicated to book3s/32 that
allocates KASAN regions using BATs.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/709e821602b48a1d7c211a9b156da26db98c3e9d.1589866984.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/kasan.h

@@ -34,6 +34,7 @@ static inline void kasan_init(void) { }
 static inline void kasan_late_init(void) { }
 #endif
 
+void kasan_update_early_region(unsigned long k_start, unsigned long k_end, pte_t pte);
 int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end);
 int kasan_init_region(void *start, size_t size);
 

arch/powerpc/mm/kasan/Makefile

@@ -4,3 +4,4 @@ KASAN_SANITIZE := n
 
 obj-$(CONFIG_PPC32)           += kasan_init_32.o
 obj-$(CONFIG_PPC_8xx)		+= 8xx.o
+obj-$(CONFIG_PPC_BOOK3S_32)	+= book3s_32.o

arch/powerpc/mm/kasan/book3s_32.c

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define DISABLE_BRANCH_PROFILING
+
+#include <linux/kasan.h>
+#include <linux/memblock.h>
+#include <asm/pgalloc.h>
+#include <mm/mmu_decl.h>
+
+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();
+	}
+
+	if (!block)
+		block = memblock_alloc(k_size, PAGE_SIZE);
+	if (!block)
+		return -ENOMEM;
+
+	ret = kasan_init_shadow_page_tables(k_start, k_end);
+	if (ret)
+		return ret;
+
+	kasan_update_early_region(k_start, k_cur, __pte(0));
+
+	for (; k_cur < k_end; k_cur += PAGE_SIZE) {
+		pmd_t *pmd = pmd_ptr_k(k_cur);
+		void *va = block + k_cur - k_start;
+		pte_t pte = pfn_pte(PHYS_PFN(__pa(va)), PAGE_KERNEL);
+
+		__set_pte_at(&init_mm, k_cur, pte_offset_kernel(pmd, k_cur), pte, 0);
+	}
+	flush_tlb_kernel_range(k_start, k_end);
+	return 0;
+}

arch/powerpc/mm/kasan/kasan_init_32.c

@@ -79,7 +79,7 @@ int __init __weak kasan_init_region(void *start, size_t size)
 	return 0;
 }
 
-static void __init
+void __init
 kasan_update_early_region(unsigned long k_start, unsigned long k_end, pte_t pte)
 {
 	unsigned long k_cur;