[PATCH v11 10/13] powerpc/32: Add KASAN support

[Christophe Leroy <christophe.leroy@c-s.fr>]

This patch adds KASAN support for PPC32. The following patch
will add an early activation of hash table for book3s. Until
then, a warning will be raised if trying to use KASAN on an
hash 6xx.

To support KASAN, this patch initialises that MMU mapings for
accessing to the KASAN shadow area defined in a previous patch.

An early mapping is set as soon as the kernel code has been
relocated at its definitive place.

Then the definitive mapping is set once paging is initialised.

For modules, the shadow area is allocated at module_alloc().

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/Kconfig                  |   1 +
 arch/powerpc/include/asm/kasan.h      |   9 ++
 arch/powerpc/kernel/head_32.S         |   3 +
 arch/powerpc/kernel/head_40x.S        |   3 +
 arch/powerpc/kernel/head_44x.S        |   3 +
 arch/powerpc/kernel/head_8xx.S        |   3 +
 arch/powerpc/kernel/head_fsl_booke.S  |   3 +
 arch/powerpc/kernel/setup-common.c    |   3 +
 arch/powerpc/mm/Makefile              |   1 +
 arch/powerpc/mm/init_32.c             |   3 +
 arch/powerpc/mm/kasan/Makefile        |   5 ++
 arch/powerpc/mm/kasan/kasan_init_32.c | 156 ++++++++++++++++++++++++++++++++++
 12 files changed, 193 insertions(+)
 create mode 100644 arch/powerpc/mm/kasan/Makefile
 create mode 100644 arch/powerpc/mm/kasan/kasan_init_32.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a7c80f2b08b5..1a2fb50126b2 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -173,6 +173,7 @@ config PPC
 	select GENERIC_TIME_VSYSCALL
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_JUMP_LABEL
+	select HAVE_ARCH_KASAN			if PPC32
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT
diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
index 05274dea3109..296e51c2f066 100644
--- a/arch/powerpc/include/asm/kasan.h
+++ b/arch/powerpc/include/asm/kasan.h
@@ -27,5 +27,14 @@
 
 #define KASAN_SHADOW_SIZE	(KASAN_SHADOW_END - KASAN_SHADOW_START)
 
+#ifdef CONFIG_KASAN
+void kasan_early_init(void);
+void kasan_mmu_init(void);
+void kasan_init(void);
+#else
+static inline void kasan_init(void) { }
+static inline void kasan_mmu_init(void) { }
+#endif
+
 #endif /* __ASSEMBLY */
 #endif
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index 40aec3f00a05..6e85171e513c 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -969,6 +969,9 @@ start_here:
  * Do early platform-specific initialization,
  * and set up the MMU.
  */
+#ifdef CONFIG_KASAN
+	bl	kasan_early_init
+#endif
 	li	r3,0
 	mr	r4,r31
 	bl	machine_init
diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index a9c934f2319b..efa219d2136e 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -848,6 +848,9 @@ start_here:
 /*
  * Decide what sort of machine this is and initialize the MMU.
  */
+#ifdef CONFIG_KASAN
+	bl	kasan_early_init
+#endif
 	li	r3,0
 	mr	r4,r31
 	bl	machine_init
diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
index 37117ab11584..34a5df827b38 100644
--- a/arch/powerpc/kernel/head_44x.S
+++ b/arch/powerpc/kernel/head_44x.S
@@ -203,6 +203,9 @@ _ENTRY(_start);
 /*
  * Decide what sort of machine this is and initialize the MMU.
  */
+#ifdef CONFIG_KASAN
+	bl	kasan_early_init
+#endif
 	li	r3,0
 	mr	r4,r31
 	bl	machine_init
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 03c73b4c6435..d25adb6ef235 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -853,6 +853,9 @@ start_here:
 /*
  * Decide what sort of machine this is and initialize the MMU.
  */
+#ifdef CONFIG_KASAN
+	bl	kasan_early_init
+#endif
 	li	r3,0
 	mr	r4,r31
 	bl	machine_init
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index 32332e24e421..567e0ed45ca8 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -268,6 +268,9 @@ set_ivor:
 /*
  * Decide what sort of machine this is and initialize the MMU.
  */
+#ifdef CONFIG_KASAN
+	bl	kasan_early_init
+#endif
 	mr	r3,r30
 	mr	r4,r31
 	bl	machine_init
diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index 1729bf409562..15afb01b4374 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -67,6 +67,7 @@
 #include <asm/livepatch.h>
 #include <asm/mmu_context.h>
 #include <asm/cpu_has_feature.h>
+#include <asm/kasan.h>
 
 #include "setup.h"
 
@@ -871,6 +872,8 @@ static void smp_setup_pacas(void)
  */
 void __init setup_arch(char **cmdline_p)
 {
+	kasan_init();
+
 	*cmdline_p = boot_command_line;
 
 	/* Set a half-reasonable default so udelay does something sensible */
diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
index dd945ca869b2..01afb10a7b33 100644
--- a/arch/powerpc/mm/Makefile
+++ b/arch/powerpc/mm/Makefile
@@ -53,6 +53,7 @@ obj-$(CONFIG_PPC_COPRO_BASE)	+= copro_fault.o
 obj-$(CONFIG_SPAPR_TCE_IOMMU)	+= mmu_context_iommu.o
 obj-$(CONFIG_PPC_PTDUMP)	+= ptdump/
 obj-$(CONFIG_PPC_MEM_KEYS)	+= pkeys.o
+obj-$(CONFIG_KASAN)		+= kasan/
 
 # Disable kcov instrumentation on sensitive code
 # This is necessary for booting with kcov enabled on book3e machines
diff --git a/arch/powerpc/mm/init_32.c b/arch/powerpc/mm/init_32.c
index 80cc97cd8878..5b61673e7eed 100644
--- a/arch/powerpc/mm/init_32.c
+++ b/arch/powerpc/mm/init_32.c
@@ -46,6 +46,7 @@
 #include <asm/sections.h>
 #include <asm/hugetlb.h>
 #include <asm/kup.h>
+#include <asm/kasan.h>
 
 #include "mmu_decl.h"
 
@@ -179,6 +180,8 @@ void __init MMU_init(void)
 	btext_unmap();
 #endif
 
+	kasan_mmu_init();
+
 	setup_kup();
 
 	/* Shortly after that, the entire linear mapping will be available */
diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
new file mode 100644
index 000000000000..6577897673dd
--- /dev/null
+++ b/arch/powerpc/mm/kasan/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+KASAN_SANITIZE := n
+
+obj-$(CONFIG_PPC32)           += kasan_init_32.o
diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
new file mode 100644
index 000000000000..42617fcad828
--- /dev/null
+++ b/arch/powerpc/mm/kasan/kasan_init_32.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define DISABLE_BRANCH_PROFILING
+
+#include <linux/kasan.h>
+#include <linux/printk.h>
+#include <linux/memblock.h>
+#include <linux/sched/task.h>
+#include <linux/vmalloc.h>
+#include <asm/pgalloc.h>
+#include <asm/code-patching.h>
+#include <mm/mmu_decl.h>
+
+static void kasan_populate_pte(pte_t *ptep, pgprot_t prot)
+{
+	unsigned long va = (unsigned long)kasan_early_shadow_page;
+	phys_addr_t pa = __pa(kasan_early_shadow_page);
+	int i;
+
+	for (i = 0; i < PTRS_PER_PTE; i++, ptep++)
+		__set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 0);
+}
+
+static int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end)
+{
+	pmd_t *pmd;
+	unsigned long k_cur, k_next;
+
+	pmd = pmd_offset(pud_offset(pgd_offset_k(k_start), k_start), k_start);
+
+	for (k_cur = k_start; k_cur != k_end; k_cur = k_next, pmd++) {
+		pte_t *new;
+
+		k_next = pgd_addr_end(k_cur, k_end);
+		if ((void *)pmd_page_vaddr(*pmd) != kasan_early_shadow_pte)
+			continue;
+
+		new = pte_alloc_one_kernel(&init_mm);
+
+		if (!new)
+			return -ENOMEM;
+		kasan_populate_pte(new, PAGE_KERNEL_RO);
+		pmd_populate_kernel(&init_mm, pmd, new);
+	}
+	return 0;
+}
+
+static void __ref *kasan_get_one_page(void)
+{
+	if (slab_is_available())
+		return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+
+	return memblock_alloc(PAGE_SIZE, PAGE_SIZE);
+}
+
+static int __ref 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;
+	int ret;
+	void *block = NULL;
+
+	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);
+
+	for (k_cur = k_start; k_cur < k_end; k_cur += PAGE_SIZE) {
+		pmd_t *pmd = pmd_offset(pud_offset(pgd_offset_k(k_cur), k_cur), k_cur);
+		void *va = block ? block + k_cur - k_start : kasan_get_one_page();
+		pte_t pte = pfn_pte(PHYS_PFN(__pa(va)), PAGE_KERNEL);
+
+		if (!va)
+			return -ENOMEM;
+
+		__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;
+}
+
+static void __init kasan_remap_early_shadow_ro(void)
+{
+	kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL_RO);
+
+	flush_tlb_kernel_range(KASAN_SHADOW_START, KASAN_SHADOW_END);
+}
+
+void __init kasan_mmu_init(void)
+{
+	int ret;
+	struct memblock_region *reg;
+
+	for_each_memblock(memory, reg) {
+		phys_addr_t base = reg->base;
+		phys_addr_t top = min(base + reg->size, total_lowmem);
+
+		if (base >= top)
+			continue;
+
+		ret = kasan_init_region(__va(base), top - base);
+		if (ret)
+			panic("kasan: kasan_init_region() failed");
+	}
+}
+
+void __init kasan_init(void)
+{
+	kasan_remap_early_shadow_ro();
+
+	clear_page(kasan_early_shadow_page);
+
+	/* At this point kasan is fully initialized. Enable error messages */
+	init_task.kasan_depth = 0;
+	pr_info("KASAN init done\n");
+}
+
+#ifdef CONFIG_MODULES
+void *module_alloc(unsigned long size)
+{
+	void *base = vmalloc_exec(size);
+
+	if (!base)
+		return NULL;
+
+	if (!kasan_init_region(base, size))
+		return base;
+
+	vfree(base);
+
+	return NULL;
+}
+#endif
+
+void __init kasan_early_init(void)
+{
+	unsigned long addr = KASAN_SHADOW_START;
+	unsigned long end = KASAN_SHADOW_END;
+	unsigned long next;
+	pmd_t *pmd = pmd_offset(pud_offset(pgd_offset_k(addr), addr), addr);
+
+	BUILD_BUG_ON(KASAN_SHADOW_START & ~PGDIR_MASK);
+
+	kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL);
+
+	do {
+		next = pgd_addr_end(addr, end);
+		pmd_populate_kernel(&init_mm, pmd, kasan_early_shadow_pte);
+	} while (pmd++, addr = next, addr != end);
+
+	if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE))
+		WARN(true, "KASAN not supported on hash 6xx");
+}
-- 
2.13.3