[PATCH v11 6/6] powerpc: Book3S 64-bit outline-only KASAN support

Daniel Axtens
2021-03-19T14:41:45Z

Implement a limited form of KASAN for Book3S 64-bit machines running under
the Radix MMU, supporting only outline mode.

- Enable the compiler instrumentation to check addresses and maintain the
shadow region. (This is the guts of KASAN which we can easily reuse.)

- Require kasan-vmalloc support to handle modules and anything else in
vmalloc space.

- KASAN needs to be able to validate all pointer accesses, but we can't
instrument all kernel addresses - only linear map and vmalloc. On boot,
set up a single page of read-only shadow that marks all iomap and
vmemmap accesses as valid.

- Make our stack-walking code KASAN-safe by using READ_ONCE_NOCHECK -
generic code, arm64, s390 and x86 all do this for similar sorts of
reasons: when unwinding a stack, we might touch memory that KASAN has
marked as being out-of-bounds. In our case we often get this when
checking for an exception frame because we're checking an arbitrary
offset into the stack frame.

See commit 20955746320e ("s390/kasan: avoid false positives during stack
unwind"), commit bcaf669b4bdb ("arm64: disable kasan when accessing
frame->fp in unwind_frame"), commit 91e08ab0c851 ("x86/dumpstack:
Prevent KASAN false positive warnings") and commit 6e22c8366416
("tracing, kasan: Silence Kasan warning in check_stack of stack_tracer")

- Document KASAN in both generic and powerpc docs.

Background
----------

KASAN support on Book3S is a bit tricky to get right:

- It would be good to support inline instrumentation so as to be able to
catch stack issues that cannot be caught with outline mode.

- Inline instrumentation requires a fixed offset.

- Book3S runs code with translations off ("real mode") during boot,
including a lot of generic device-tree parsing code which is used to
determine MMU features.

[ppc64 mm note: The kernel installs a linear mapping at effective
address c000...-c008.... This is a one-to-one mapping with physical
memory from 0000... onward. Because of how memory accesses work on
powerpc 64-bit Book3S, a kernel pointer in the linear map accesses the
same memory both with translations on (accessing as an 'effective
address'), and with translations off (accessing as a 'real
address'). This works in both guests and the hypervisor. For more
details, see s5.7 of Book III of version 3 of the ISA, in particular
the Storage Control Overview, s5.7.3, and s5.7.5 - noting that this
KASAN implementation currently only supports Radix.]

- Some code - most notably a lot of KVM code - also runs with translations
off after boot.

- Therefore any offset has to point to memory that is valid with
translations on or off.

One approach is just to give up on inline instrumentation. This way
boot-time checks can be delayed until after the MMU is set is up, and we
can just not instrument any code that runs with translations off after
booting. Take this approach for now and require outline instrumentation.

Previous attempts allowed inline instrumentation. However, they came with
some unfortunate restrictions: only physically contiguous memory could be
used and it had to be specified at compile time. Maybe we can do better in
the future.

Cc: Balbir Singh <bsingharora@gmail.com> # ppc64 out-of-line radix version
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> # ppc64 hash version
Cc: Christophe Leroy <christophe.leroy@csgroup.eu> # ppc32 version
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
Documentation/dev-tools/kasan.rst | 11 +--
Documentation/powerpc/kasan.txt | 48 +++++++++-
arch/powerpc/Kconfig | 4 +-
arch/powerpc/Kconfig.debug | 3 +-
arch/powerpc/include/asm/book3s/64/hash.h | 4 +
arch/powerpc/include/asm/book3s/64/pgtable.h | 4 +
arch/powerpc/include/asm/book3s/64/radix.h | 13 ++-
arch/powerpc/include/asm/kasan.h | 22 +++++
arch/powerpc/kernel/Makefile | 11 +++
arch/powerpc/kernel/process.c | 16 ++--
arch/powerpc/kvm/Makefile | 5 ++
arch/powerpc/mm/book3s64/Makefile | 9 ++
arch/powerpc/mm/kasan/Makefile | 1 +
arch/powerpc/mm/kasan/init_book3s_64.c | 95 ++++++++++++++++++++
arch/powerpc/mm/ptdump/ptdump.c | 20 ++++-
arch/powerpc/platforms/Kconfig.cputype | 1 +
arch/powerpc/platforms/powernv/Makefile | 6 ++
arch/powerpc/platforms/pseries/Makefile | 3 +
18 files changed, 257 insertions(+), 19 deletions(-)
create mode 100644 arch/powerpc/mm/kasan/init_book3s_64.c

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index 2cfd5d9068c0..8024b55c7aa8 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -36,8 +36,9 @@ Both software KASAN modes work with SLUB and SLAB memory allocators,
while the hardware tag-based KASAN currently only supports SLUB.

Currently, generic KASAN is supported for the x86_64, arm, arm64, xtensa, s390,
-and riscv architectures. It is also supported on 32-bit powerpc kernels.
-Tag-based KASAN modes are supported only for arm64.
+and riscv architectures. It is also supported on powerpc for 32-bit kernels and
+for 64-bit kernels running under the Radix MMU. Tag-based KASAN modes are
+supported only for arm64.

Usage
-----
@@ -335,10 +336,10 @@ CONFIG_KASAN_VMALLOC

With ``CONFIG_KASAN_VMALLOC``, KASAN can cover vmalloc space at the
cost of greater memory usage. Currently, this is supported on x86,
-riscv, s390, and 32-bit powerpc.
+riscv, s390, and powerpc.

-It is optional, except on 32-bit powerpc kernels with module support,
-where it is required.
+It is optional, except on 64-bit powerpc kernels, and on 32-bit
+powerpc kernels with module support, where it is required.

This works by hooking into vmalloc and vmap and dynamically
allocating real shadow memory to back the mappings.
diff --git a/Documentation/powerpc/kasan.txt b/Documentation/powerpc/kasan.txt
index 26bb0e8bb18c..f032b4eaf205 100644
--- a/Documentation/powerpc/kasan.txt
+++ b/Documentation/powerpc/kasan.txt
@@ -1,4 +1,4 @@
-KASAN is supported on powerpc on 32-bit only.
+KASAN is supported on powerpc on 32-bit and Radix 64-bit only.

32 bit support
==============
@@ -10,3 +10,49 @@ fixmap area and occupies one eighth of the total kernel virtual memory space.

Instrumentation of the vmalloc area is optional, unless built with modules,
in which case it is required.
+
+64 bit support
+==============
+
+Currently, only the radix MMU is supported. There have been versions for hash
+and Book3E processors floating around on the mailing list, but nothing has been
+merged.
+
+KASAN support on Book3S is a bit tricky to get right:
+
+ - It would be good to support inline instrumentation so as to be able to catch
+ stack issues that cannot be caught with outline mode.
+
+ - Inline instrumentation requires a fixed offset.
+
+ - Book3S runs code with translations off ("real mode") during boot, including a
+ lot of generic device-tree parsing code which is used to determine MMU
+ features.
+
+ - Some code - most notably a lot of KVM code - also runs with translations off
+ after boot.
+
+ - Therefore any offset has to point to memory that is valid with
+ translations on or off.
+
+One approach is just to give up on inline instrumentation. This way boot-time
+checks can be delayed until after the MMU is set is up, and we can just not
+instrument any code that runs with translations off after booting. This is the
+current approach.
+
+To avoid this limitiation, the KASAN shadow would have to be placed inside the
+linear mapping, using the same high-bits trick we use for the rest of the linear
+mapping. This is tricky:
+
+ - We'd like to place it near the start of physical memory. In theory we can do
+ this at run-time based on how much physical memory we have, but this requires
+ being able to arbitrarily relocate the kernel, which is basically the tricky
+ part of KASLR. Not being game to implement both tricky things at once, this
+ is hopefully something we can revisit once we get KASLR for Book3S.
+
+ - Alternatively, we can place the shadow at the _end_ of memory, but this
+ requires knowing how much contiguous physical memory a system has _at compile
+ time_. This is a big hammer, and has some unfortunate consequences: inablity
+ to handle discontiguous physical memory, total failure to boot on machines
+ with less memory than specified, and that machines with more memory than
+ specified can't use it. This was deemed unacceptable.
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 4232d3f539c8..04aa817d1c5a 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -118,6 +118,7 @@ config PPC
# Please keep this list sorted alphabetically.
#
select ARCH_32BIT_OFF_T if PPC32
+ select ARCH_DISABLE_KASAN_INLINE if PPC_RADIX_MMU
select ARCH_HAS_DEBUG_VIRTUAL
select ARCH_HAS_DEVMEM_IS_ALLOWED
select ARCH_HAS_ELF_RANDOMIZE
@@ -183,7 +184,8 @@ config PPC
select HAVE_ARCH_HUGE_VMAP if PPC_BOOK3S_64 && PPC_RADIX_MMU
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_KASAN if PPC32 && PPC_PAGE_SHIFT <= 14
- select HAVE_ARCH_KASAN_VMALLOC if PPC32 && PPC_PAGE_SHIFT <= 14
+ select HAVE_ARCH_KASAN if PPC_RADIX_MMU
+ select HAVE_ARCH_KASAN_VMALLOC if HAVE_ARCH_KASAN
select HAVE_ARCH_KGDB
select HAVE_ARCH_MMAP_RND_BITS
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index ae084357994e..195f7845f41a 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -398,4 +398,5 @@ config PPC_FAST_ENDIAN_SWITCH
config KASAN_SHADOW_OFFSET
hex
depends on KASAN
- default 0xe0000000
+ default 0xe0000000 if PPC32
+ default 0xa80e000000000000 if PPC64
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index d959b0195ad9..222669864ff6 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h
@@ -18,6 +18,10 @@
#include <asm/book3s/64/hash-4k.h>
#endif

+#define H_PTRS_PER_PTE (1 << H_PTE_INDEX_SIZE)
+#define H_PTRS_PER_PMD (1 << H_PMD_INDEX_SIZE)
+#define H_PTRS_PER_PUD (1 << H_PUD_INDEX_SIZE)
+
/* Bits to set in a PMD/PUD/PGD entry valid bit*/
#define HASH_PMD_VAL_BITS (0x8000000000000000UL)
#define HASH_PUD_VAL_BITS (0x8000000000000000UL)
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 058601efbc8a..7598a5b055bd 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -230,6 +230,10 @@ extern unsigned long __pmd_frag_size_shift;
#define PTRS_PER_PUD (1 << PUD_INDEX_SIZE)
#define PTRS_PER_PGD (1 << PGD_INDEX_SIZE)

+#define MAX_PTRS_PER_PTE ((H_PTRS_PER_PTE > R_PTRS_PER_PTE) ? H_PTRS_PER_PTE : R_PTRS_PER_PTE)
+#define MAX_PTRS_PER_PMD ((H_PTRS_PER_PMD > R_PTRS_PER_PMD) ? H_PTRS_PER_PMD : R_PTRS_PER_PMD)
+#define MAX_PTRS_PER_PUD ((H_PTRS_PER_PUD > R_PTRS_PER_PUD) ? H_PTRS_PER_PUD : R_PTRS_PER_PUD)
+
/* PMD_SHIFT determines what a second-level page table entry can map */
#define PMD_SHIFT (PAGE_SHIFT + PTE_INDEX_SIZE)
#define PMD_SIZE (1UL << PMD_SHIFT)
diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
index c7813dc628fc..b3492b80f858 100644
--- a/arch/powerpc/include/asm/book3s/64/radix.h
+++ b/arch/powerpc/include/asm/book3s/64/radix.h
@@ -35,6 +35,11 @@
#define RADIX_PMD_SHIFT (PAGE_SHIFT + RADIX_PTE_INDEX_SIZE)
#define RADIX_PUD_SHIFT (RADIX_PMD_SHIFT + RADIX_PMD_INDEX_SIZE)
#define RADIX_PGD_SHIFT (RADIX_PUD_SHIFT + RADIX_PUD_INDEX_SIZE)
+
+#define R_PTRS_PER_PTE (1 << RADIX_PTE_INDEX_SIZE)
+#define R_PTRS_PER_PMD (1 << RADIX_PMD_INDEX_SIZE)
+#define R_PTRS_PER_PUD (1 << RADIX_PUD_INDEX_SIZE)
+
/*
* Size of EA range mapped by our pagetables.
*/
@@ -68,11 +73,11 @@
*
*
* 3rd quadrant expanded:
- * +------------------------------+
+ * +------------------------------+ Highest address (0xc010000000000000)
+ * +------------------------------+ KASAN shadow end (0xc00fc00000000000)
* | |
* | |
- * | |
- * +------------------------------+ Kernel vmemmap end (0xc010000000000000)
+ * +------------------------------+ Kernel vmemmap end/shadow start (0xc00e000000000000)
* | |
* | 512TB |
* | |
@@ -126,6 +131,8 @@
#define RADIX_VMEMMAP_SIZE RADIX_KERN_MAP_SIZE
#define RADIX_VMEMMAP_END (RADIX_VMEMMAP_START + RADIX_VMEMMAP_SIZE)

+/* For the sizes of the shadow area, see kasan.h */
+
#ifndef __ASSEMBLY__
#define RADIX_PTE_TABLE_SIZE (sizeof(pte_t) << RADIX_PTE_INDEX_SIZE)
#define RADIX_PMD_TABLE_SIZE (sizeof(pmd_t) << RADIX_PMD_INDEX_SIZE)
diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
index 7355ed05e65e..df946165812d 100644
--- a/arch/powerpc/include/asm/kasan.h
+++ b/arch/powerpc/include/asm/kasan.h
@@ -30,9 +30,31 @@

#define KASAN_SHADOW_OFFSET ASM_CONST(CONFIG_KASAN_SHADOW_OFFSET)

+#ifdef CONFIG_PPC32
#define KASAN_SHADOW_END (-(-KASAN_SHADOW_START >> KASAN_SHADOW_SCALE_SHIFT))
+#endif

#ifdef CONFIG_KASAN
+#ifdef CONFIG_PPC_BOOK3S_64
+/*
+ * The shadow ends before the highest accessible address
+ * because we don't need a shadow for the shadow. Instead:
+ * c00e000000000000 << 3 + a80e000000000000000 = c00fc00000000000
+ */
+#define KASAN_SHADOW_END 0xc00fc00000000000UL
+
+DECLARE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
+
+static __always_inline bool kasan_arch_is_ready(void)
+{
+ if (static_branch_likely(&powerpc_kasan_enabled_key))
+ return true;
+ return false;
+}
+
+#define kasan_arch_is_ready kasan_arch_is_ready
+#endif
+
void kasan_early_init(void);
void kasan_mmu_init(void);
void kasan_init(void);
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 6084fa499aa3..163755b1cef4 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -32,6 +32,17 @@ KASAN_SANITIZE_early_32.o := n
KASAN_SANITIZE_cputable.o := n
KASAN_SANITIZE_prom_init.o := n
KASAN_SANITIZE_btext.o := n
+KASAN_SANITIZE_paca.o := n
+KASAN_SANITIZE_setup_64.o := n
+KASAN_SANITIZE_mce.o := n
+KASAN_SANITIZE_mce_power.o := n
+
+# we have to be particularly careful in ppc64 to exclude code that
+# runs with translations off, as we cannot access the shadow with
+# translations off. However, ppc32 can sanitize this.
+ifdef CONFIG_PPC64
+KASAN_SANITIZE_traps.o := n
+endif

ifdef CONFIG_KASAN
CFLAGS_early_32.o += -DDISABLE_BRANCH_PROFILING
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 3231c2df9e26..d4ae21b9e9b7 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -2160,8 +2160,8 @@ void show_stack(struct task_struct *tsk, unsigned long *stack,
break;

stack = (unsigned long *) sp;
- newsp = stack[0];
- ip = stack[STACK_FRAME_LR_SAVE];
+ newsp = READ_ONCE_NOCHECK(stack[0]);
+ ip = READ_ONCE_NOCHECK(stack[STACK_FRAME_LR_SAVE]);
if (!firstframe || ip != lr) {
printk("%s["REG"] ["REG"] %pS",
loglvl, sp, ip, (void *)ip);
@@ -2179,17 +2179,19 @@ void show_stack(struct task_struct *tsk, unsigned long *stack,
* See if this is an exception frame.
* We look for the "regshere" marker in the current frame.
*/
- if (validate_sp(sp, tsk, STACK_FRAME_WITH_PT_REGS)
- && stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
+ if (validate_sp(sp, tsk, STACK_FRAME_WITH_PT_REGS) &&
+ (READ_ONCE_NOCHECK(stack[STACK_FRAME_MARKER]) ==
+ STACK_FRAME_REGS_MARKER)) {
struct pt_regs *regs = (struct pt_regs *)
(sp + STACK_FRAME_OVERHEAD);

- lr = regs->link;
+ lr = READ_ONCE_NOCHECK(regs->link);
printk("%s--- interrupt: %lx at %pS\n",
- loglvl, regs->trap, (void *)regs->nip);
+ loglvl, READ_ONCE_NOCHECK(regs->trap),
+ (void *)READ_ONCE_NOCHECK(regs->nip));
__show_regs(regs);
printk("%s--- interrupt: %lx\n",
- loglvl, regs->trap);
+ loglvl, READ_ONCE_NOCHECK(regs->trap));

firstframe = 1;
}
diff --git a/arch/powerpc/kvm/Makefile b/arch/powerpc/kvm/Makefile
index 2bfeaa13befb..7f1592dacbeb 100644
--- a/arch/powerpc/kvm/Makefile
+++ b/arch/powerpc/kvm/Makefile
@@ -136,3 +136,8 @@ obj-$(CONFIG_KVM_BOOK3S_64_PR) += kvm-pr.o
obj-$(CONFIG_KVM_BOOK3S_64_HV) += kvm-hv.o

obj-y += $(kvm-book3s_64-builtin-objs-y)
+
+# KVM does a lot in real-mode, and 64-bit Book3S KASAN doesn't support that
+ifdef CONFIG_PPC_BOOK3S_64
+KASAN_SANITIZE := n
+endif
diff --git a/arch/powerpc/mm/book3s64/Makefile b/arch/powerpc/mm/book3s64/Makefile
index 1b56d3af47d4..a7d8a68bd2c5 100644
--- a/arch/powerpc/mm/book3s64/Makefile
+++ b/arch/powerpc/mm/book3s64/Makefile
@@ -21,3 +21,12 @@ obj-$(CONFIG_PPC_PKEY) += pkeys.o

# Instrumenting the SLB fault path can lead to duplicate SLB entries
KCOV_INSTRUMENT_slb.o := n
+
+# Parts of these can run in real mode and therefore are
+# not safe with the current outline KASAN implementation
+KASAN_SANITIZE_mmu_context.o := n
+KASAN_SANITIZE_pgtable.o := n
+KASAN_SANITIZE_radix_pgtable.o := n
+KASAN_SANITIZE_radix_tlb.o := n
+KASAN_SANITIZE_slb.o := n
+KASAN_SANITIZE_pkeys.o := n
diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
index 42fb628a44fd..07eef87abd6c 100644
--- a/arch/powerpc/mm/kasan/Makefile
+++ b/arch/powerpc/mm/kasan/Makefile
@@ -5,3 +5,4 @@ KASAN_SANITIZE := n
obj-$(CONFIG_PPC32) += init_32.o
obj-$(CONFIG_PPC_8xx) += 8xx.o
obj-$(CONFIG_PPC_BOOK3S_32) += book3s_32.o
+obj-$(CONFIG_PPC_BOOK3S_64) += init_book3s_64.o
diff --git a/arch/powerpc/mm/kasan/init_book3s_64.c b/arch/powerpc/mm/kasan/init_book3s_64.c
new file mode 100644
index 000000000000..ca913ed951a2
--- /dev/null
+++ b/arch/powerpc/mm/kasan/init_book3s_64.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KASAN for 64-bit Book3S powerpc
+ *
+ * Copyright (C) 2019-2020 IBM Corporation
+ * Author: Daniel Axtens <dja@axtens.net>
+ */
+
+#define DISABLE_BRANCH_PROFILING
+
+#include <linux/kasan.h>
+#include <linux/printk.h>
+#include <linux/sched/task.h>
+#include <linux/memblock.h>
+#include <asm/pgalloc.h>
+
+DEFINE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
+
+static void __init kasan_init_phys_region(void *start, void *end)
+{
+ unsigned long k_start, k_end, k_cur;
+ void *va;
+
+ if (start >= end)
+ return;
+
+ k_start = ALIGN_DOWN((unsigned long)kasan_mem_to_shadow(start), PAGE_SIZE);
+ k_end = ALIGN((unsigned long)kasan_mem_to_shadow(end), PAGE_SIZE);
+
+ va = memblock_alloc(k_end - k_start, PAGE_SIZE);
+ for (k_cur = k_start; k_cur < k_end; k_cur += PAGE_SIZE, va += PAGE_SIZE)
+ map_kernel_page(k_cur, __pa(va), PAGE_KERNEL);
+}
+
+void __init kasan_init(void)
+{
+ /*
+ * We want to do the following things:
+ * 1) Map real memory into the shadow for all physical memblocks
+ * This takes us from c000... to c008...
+ * 2) Leave a hole over the shadow of vmalloc space. KASAN_VMALLOC
+ * will manage this for us.
+ * This takes us from c008... to c00a...
+ * 3) Map the 'early shadow'/zero page over iomap and vmemmap space.
+ * This takes us up to where we start at c00e...
+ */
+
+ void *k_start = kasan_mem_to_shadow((void *)RADIX_VMALLOC_END);
+ void *k_end = kasan_mem_to_shadow((void *)RADIX_VMEMMAP_END);
+ phys_addr_t start, end;
+ u64 i;
+ pte_t zero_pte = pfn_pte(virt_to_pfn(kasan_early_shadow_page), PAGE_KERNEL);
+
+ if (!early_radix_enabled())
+ panic("KASAN requires radix!");
+
+ for_each_mem_range(i, &start, &end)
+ kasan_init_phys_region((void *)start, (void *)end);
+
+ for (i = 0; i < PTRS_PER_PTE; i++)
+ __set_pte_at(&init_mm, (unsigned long)kasan_early_shadow_page,
+ &kasan_early_shadow_pte[i], zero_pte, 0);
+
+ for (i = 0; i < PTRS_PER_PMD; i++)
+ pmd_populate_kernel(&init_mm, &kasan_early_shadow_pmd[i],
+ kasan_early_shadow_pte);
+
+ for (i = 0; i < PTRS_PER_PUD; i++)
+ pud_populate(&init_mm, &kasan_early_shadow_pud[i],
+ kasan_early_shadow_pmd);
+
+ /* map the early shadow over the iomap and vmemmap space */
+ kasan_populate_early_shadow(k_start, k_end);
+
+ /* mark early shadow region as RO and wipe it */
+ zero_pte = pfn_pte(virt_to_pfn(kasan_early_shadow_page), PAGE_KERNEL_RO);
+ for (i = 0; i < PTRS_PER_PTE; i++)
+ __set_pte_at(&init_mm, (unsigned long)kasan_early_shadow_page,
+ &kasan_early_shadow_pte[i], zero_pte, 0);
+
+ /*
+ * clear_page relies on some cache info that hasn't been set up yet.
+ * It ends up looping ~forever and blows up other data.
+ * Use memset instead.
+ */
+ memset(kasan_early_shadow_page, 0, PAGE_SIZE);
+
+ static_branch_inc(&powerpc_kasan_enabled_key);
+
+ /* Enable error messages */
+ init_task.kasan_depth = 0;
+ pr_info("KASAN init done (64-bit Book3S)\n");
+}
+
+void __init kasan_late_init(void) { }
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index aca354fb670b..63672aa656e8 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -20,6 +20,7 @@
#include <linux/seq_file.h>
#include <asm/fixmap.h>
#include <linux/const.h>
+#include <linux/kasan.h>
#include <asm/page.h>
#include <asm/hugetlb.h>

@@ -317,6 +318,23 @@ static void walk_pud(struct pg_state *st, p4d_t *p4d, unsigned long start)
unsigned long addr;
unsigned int i;

+#if defined(CONFIG_KASAN) && defined(CONFIG_PPC_BOOK3S_64)
+ /*
+ * On radix + KASAN, we want to check for the KASAN "early" shadow
+ * which covers huge quantities of memory with the same set of
+ * read-only PTEs. If it is, we want to note the first page (to see
+ * the status change), and then note the last page. This gives us good
+ * results without spending ages noting the exact same PTEs over 100s of
+ * terabytes of memory.
+ */
+ if (p4d_page(*p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud))) {
+ walk_pmd(st, pud, start);
+ addr = start + (PTRS_PER_PUD - 1) * PUD_SIZE;
+ walk_pmd(st, pud, addr);
+ return;
+ }
+#endif
+
for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
addr = start + i * PUD_SIZE;
if (!pud_none(*pud) && !pud_is_leaf(*pud))
@@ -387,11 +405,11 @@ static void populate_markers(void)
#endif
address_markers[i++].start_address = FIXADDR_START;
address_markers[i++].start_address = FIXADDR_TOP;
+#endif /* CONFIG_PPC64 */
#ifdef CONFIG_KASAN
address_markers[i++].start_address = KASAN_SHADOW_START;
address_markers[i++].start_address = KASAN_SHADOW_END;
#endif
-#endif /* CONFIG_PPC64 */
}

static int ptdump_show(struct seq_file *m, void *v)
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 3ce907523b1e..9063c13e7221 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -101,6 +101,7 @@ config PPC_BOOK3S_64
select ARCH_SUPPORTS_NUMA_BALANCING
select IRQ_WORK
select PPC_MM_SLICES
+ select KASAN_VMALLOC if KASAN

config PPC_BOOK3E_64
bool "Embedded processors"
diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
index 2eb6ae150d1f..f277e4793696 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -1,4 +1,10 @@
# SPDX-License-Identifier: GPL-2.0
+
+# nothing that deals with real mode is safe to KASAN
+# in particular, idle code runs a bunch of things in real mode
+KASAN_SANITIZE_idle.o := n
+KASAN_SANITIZE_pci-ioda.o := n
+
obj-y += setup.o opal-call.o opal-wrappers.o opal.o opal-async.o
obj-y += idle.o opal-rtc.o opal-nvram.o opal-lpc.o opal-flash.o
obj-y += rng.o opal-elog.o opal-dump.o opal-sysparam.o opal-sensor.o
diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index c8a2b0b05ac0..202199ef9e5c 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -30,3 +30,6 @@ obj-$(CONFIG_PPC_SVM) += svm.o
obj-$(CONFIG_FA_DUMP) += rtas-fadump.o

obj-$(CONFIG_SUSPEND) += suspend.o
+
+# nothing that operates in real mode is safe for KASAN
+KASAN_SANITIZE_ras.o := n
--
2.27.0