[PATCH v9 0/6] KASAN for powerpc64 radix

[PATCH v9 0/6] KASAN for powerpc64 radix

[Daniel Axtens]

Building on the work of Christophe, Aneesh and Balbir, I've ported
KASAN to 64-bit Book3S kernels running on the Radix MMU.

This is a significant reworking of the previous versions. Instead of
the previous approach which supported inline instrumentation, this
series provides only outline instrumentation.

To get around the problem of accessing the shadow region inside code we run
with translations off (in 'real mode'), we we restrict checking to when
translations are enabled. This is done via a new hook in the kasan core and
by excluding larger quantites of arch code from instrumentation. The upside
is that we no longer require that you be able to specify the amount of
physically contiguous memory on the system at compile time. Hopefully this
is a better trade-off. More details in patch 6.

kexec works. Both 64k and 4k pages work. Running as a KVM host works, but
nothing in arch/powerpc/kvm is instrumented. It's also potentially a bit
fragile - if any real mode code paths call out to instrumented code, things
will go boom.

There are 4 failing KUnit tests:

kasan_stack_oob, kasan_alloca_oob_left & kasan_alloca_oob_right - these are
due to not supporting inline instrumentation.

kasan_global_oob - gcc puts the ASAN init code in a section called
'.init_array'. Powerpc64 module loading code goes through and _renames_ any
section beginning with '.init' to begin with '_init' in order to avoid some
complexities around our 24-bit indirect jumps. This means it renames
'.init_array' to '_init_array', and the generic module loading code then
fails to recognise the section as a constructor and thus doesn't run
it. This hack dates back to 2003 and so I'm not going to try to unpick it
in this series. (I suspect this may have previously worked if the code
ended up in .ctors rather than .init_array but I don't keep my old binaries
around so I have no real way of checking.)


Daniel Axtens (6):
  kasan: allow an architecture to disable inline instrumentation
  kasan: allow architectures to provide an outline readiness check
  kasan: define and use MAX_PTRS_PER_* for early shadow tables
  kasan: Document support on 32-bit powerpc
  powerpc/mm/kasan: rename kasan_init_32.c to init_32.c
  powerpc: Book3S 64-bit outline-only KASAN support

[PATCH v9 1/6] kasan: allow an architecture to disable inline instrumentation

[Daniel Axtens]

For annoying architectural reasons, it's very difficult to support inline
instrumentation on powerpc64.

Add a Kconfig flag to allow an arch to disable inline. (It's a bit
annoying to be 'backwards', but I'm not aware of any way to have
an arch force a symbol to be 'n', rather than 'y'.)

Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 lib/Kconfig.kasan | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 542a9c18398e..31a0b28f6c2b 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -9,6 +9,9 @@ config HAVE_ARCH_KASAN_SW_TAGS
 config	HAVE_ARCH_KASAN_VMALLOC
 	bool
 
+config HAVE_ARCH_NO_KASAN_INLINE
+	def_bool n
+
 config CC_HAS_KASAN_GENERIC
 	def_bool $(cc-option, -fsanitize=kernel-address)
 
@@ -108,6 +111,7 @@ config KASAN_OUTLINE
 
 config KASAN_INLINE
 	bool "Inline instrumentation"
+	depends on !HAVE_ARCH_NO_KASAN_INLINE
 	help
 	  Compiler directly inserts code checking shadow memory before
 	  memory accesses. This is faster than outline (in some workloads
-- 
2.25.1

[PATCH v9 2/6] kasan: allow architectures to provide an outline readiness check

[Daniel Axtens]

Allow architectures to define a kasan_arch_is_ready() hook that bails
out of any function that's about to touch the shadow unless the arch
says that it is ready for the memory to be accessed. This is fairly
uninvasive and should have a negligible performance penalty.

This will only work in outline mode, so an arch must specify
HAVE_ARCH_NO_KASAN_INLINE if it requires this.

Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Daniel Axtens <dja@axtens.net>

--

I discuss the justfication for this later in the series. Also,
both previous RFCs for ppc64 - by 2 different people - have
needed this trick! See:
 - https://lore.kernel.org/patchwork/patch/592820/ # ppc64 hash series
 - https://patchwork.ozlabs.org/patch/795211/      # ppc radix series
---
 include/linux/kasan.h |  4 ++++
 mm/kasan/common.c     | 10 ++++++++++
 mm/kasan/generic.c    |  3 +++
 3 files changed, 17 insertions(+)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 30d343b4a40a..3df66fdf6662 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -20,6 +20,10 @@ struct kunit_kasan_expectation {
 	bool report_found;
 };
 
+#ifndef kasan_arch_is_ready
+static inline bool kasan_arch_is_ready(void)	{ return true; }
+#endif
+
 extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
 extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
 extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 950fd372a07e..ba7744d3e319 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -117,6 +117,9 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value)
 {
 	void *shadow_start, *shadow_end;
 
+	if (!kasan_arch_is_ready())
+		return;
+
 	/*
 	 * Perform shadow offset calculation based on untagged address, as
 	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
@@ -134,6 +137,9 @@ void kasan_unpoison_shadow(const void *address, size_t size)
 {
 	u8 tag = get_tag(address);
 
+	if (!kasan_arch_is_ready())
+		return;
+
 	/*
 	 * Perform shadow offset calculation based on untagged address, as
 	 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
@@ -406,6 +412,10 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 	if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
 		return false;
 
+	/* We can't read the shadow byte if the arch isn't ready */
+	if (!kasan_arch_is_ready())
+		return false;
+
 	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
 	if (shadow_invalid(tag, shadow_byte)) {
 		kasan_report_invalid_free(tagged_object, ip);
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
index 248264b9cb76..e87404026b2b 100644
--- a/mm/kasan/generic.c
+++ b/mm/kasan/generic.c
@@ -169,6 +169,9 @@ static __always_inline bool check_memory_region_inline(unsigned long addr,
 						size_t size, bool write,
 						unsigned long ret_ip)
 {
+	if (!kasan_arch_is_ready())
+		return true;
+
 	if (unlikely(size == 0))
 		return true;
 
-- 
2.25.1

[PATCH v9 3/6] kasan: define and use MAX_PTRS_PER_* for early shadow tables

[Daniel Axtens]

powerpc has a variable number of PTRS_PER_*, set at runtime based
on the MMU that the kernel is booted under.

This means the PTRS_PER_* are no longer constants, and therefore
breaks the build.

Define default MAX_PTRS_PER_*s in the same style as MAX_PTRS_PER_P4D.
As KASAN is the only user at the moment, just define them in the kasan
header, and have them default to PTRS_PER_* unless overridden in arch
code.

Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Suggested-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 include/linux/kasan.h | 18 +++++++++++++++---
 mm/kasan/init.c       |  6 +++---
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 3df66fdf6662..893d054aad6f 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -24,10 +24,22 @@ struct kunit_kasan_expectation {
 static inline bool kasan_arch_is_ready(void)	{ return true; }
 #endif
 
+#ifndef MAX_PTRS_PER_PTE
+#define MAX_PTRS_PER_PTE PTRS_PER_PTE
+#endif
+
+#ifndef MAX_PTRS_PER_PMD
+#define MAX_PTRS_PER_PMD PTRS_PER_PMD
+#endif
+
+#ifndef MAX_PTRS_PER_PUD
+#define MAX_PTRS_PER_PUD PTRS_PER_PUD
+#endif
+
 extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
-extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
-extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
-extern pud_t kasan_early_shadow_pud[PTRS_PER_PUD];
+extern pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE];
+extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
+extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
 extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
 
 int kasan_populate_early_shadow(const void *shadow_start,
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index fe6be0be1f76..42bca3d27db8 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -46,7 +46,7 @@ static inline bool kasan_p4d_table(pgd_t pgd)
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 3
-pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
+pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
 static inline bool kasan_pud_table(p4d_t p4d)
 {
 	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
@@ -58,7 +58,7 @@ static inline bool kasan_pud_table(p4d_t p4d)
 }
 #endif
 #if CONFIG_PGTABLE_LEVELS > 2
-pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
+pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
 static inline bool kasan_pmd_table(pud_t pud)
 {
 	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
@@ -69,7 +69,7 @@ static inline bool kasan_pmd_table(pud_t pud)
 	return false;
 }
 #endif
-pte_t kasan_early_shadow_pte[PTRS_PER_PTE] __page_aligned_bss;
+pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE] __page_aligned_bss;
 
 static inline bool kasan_pte_table(pmd_t pmd)
 {
-- 
2.25.1

[PATCH v9 4/6] kasan: Document support on 32-bit powerpc

[Daniel Axtens]

KASAN is supported on 32-bit powerpc and the docs should reflect this.

Document s390 support while we're at it.

Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 Documentation/dev-tools/kasan.rst |  7 +++++--
 Documentation/powerpc/kasan.txt   | 12 ++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/powerpc/kasan.txt

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index 2b68addaadcd..eaf868094a8e 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -19,7 +19,8 @@ out-of-bounds accesses for global variables is only supported since Clang 11.
 Tag-based KASAN is only supported in Clang.
 
 Currently generic KASAN is supported for the x86_64, arm64, xtensa, s390 and
-riscv architectures, and tag-based KASAN is supported only for arm64.
+riscv architectures. It is also supported on 32-bit powerpc kernels. Tag-based
+KASAN is supported only on arm64.
 
 Usage
 -----
@@ -255,7 +256,9 @@ CONFIG_KASAN_VMALLOC
 ~~~~~~~~~~~~~~~~~~~~
 
 With ``CONFIG_KASAN_VMALLOC``, KASAN can cover vmalloc space at the
-cost of greater memory usage. Currently this is only supported on x86.
+cost of greater memory usage. Currently this supported on x86, s390
+and 32-bit powerpc. It is optional, except 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
new file mode 100644
index 000000000000..26bb0e8bb18c
--- /dev/null
+++ b/Documentation/powerpc/kasan.txt
@@ -0,0 +1,12 @@
+KASAN is supported on powerpc on 32-bit only.
+
+32 bit support
+==============
+
+KASAN is supported on both hash and nohash MMUs on 32-bit.
+
+The shadow area sits at the top of the kernel virtual memory space above the
+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.
-- 
2.25.1

[PATCH v9 5/6] powerpc/mm/kasan: rename kasan_init_32.c to init_32.c

[Daniel Axtens]

kasan is already implied by the directory name, we don't need to
repeat it.

Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 arch/powerpc/mm/kasan/Makefile                       | 2 +-
 arch/powerpc/mm/kasan/{kasan_init_32.c => init_32.c} | 0
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename arch/powerpc/mm/kasan/{kasan_init_32.c => init_32.c} (100%)

diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
index bb1a5408b86b..42fb628a44fd 100644
--- a/arch/powerpc/mm/kasan/Makefile
+++ b/arch/powerpc/mm/kasan/Makefile
@@ -2,6 +2,6 @@
 
 KASAN_SANITIZE := n
 
-obj-$(CONFIG_PPC32)           += kasan_init_32.o
+obj-$(CONFIG_PPC32)           += init_32.o
 obj-$(CONFIG_PPC_8xx)		+= 8xx.o
 obj-$(CONFIG_PPC_BOOK3S_32)	+= book3s_32.o
diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/init_32.c
similarity index 100%
rename from arch/powerpc/mm/kasan/kasan_init_32.c
rename to arch/powerpc/mm/kasan/init_32.c
-- 
2.25.1

[PATCH v9 6/6] powerpc: Book3S 64-bit outline-only KASAN support

[Daniel Axtens]

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@c-s.fr> # ppc32 version
Signed-off-by: Daniel Axtens <dja@axtens.net>
---
 Documentation/dev-tools/kasan.rst            |  9 +-
 Documentation/powerpc/kasan.txt              | 48 +++++++++-
 arch/powerpc/Kconfig                         |  4 +-
 arch/powerpc/Kconfig.debug                   |  2 +-
 arch/powerpc/include/asm/book3s/64/hash.h    |  4 +
 arch/powerpc/include/asm/book3s/64/pgtable.h |  7 ++
 arch/powerpc/include/asm/book3s/64/radix.h   | 13 ++-
 arch/powerpc/include/asm/kasan.h             | 34 ++++++-
 arch/powerpc/kernel/Makefile                 |  5 +
 arch/powerpc/kernel/process.c                | 16 ++--
 arch/powerpc/kvm/Makefile                    |  5 +
 arch/powerpc/mm/book3s64/Makefile            |  8 ++
 arch/powerpc/mm/kasan/Makefile               |  1 +
 arch/powerpc/mm/kasan/init_book3s_64.c       | 98 ++++++++++++++++++++
 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, 265 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 eaf868094a8e..28f08959bd2e 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -19,8 +19,9 @@ out-of-bounds accesses for global variables is only supported since Clang 11.
 Tag-based KASAN is only supported in Clang.
 
 Currently generic KASAN is supported for the x86_64, arm64, xtensa, s390 and
-riscv architectures. It is also supported on 32-bit powerpc kernels. Tag-based
-KASAN is supported only on arm64.
+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 is supported
+only on arm64.
 
 Usage
 -----
@@ -257,8 +258,8 @@ CONFIG_KASAN_VMALLOC
 
 With ``CONFIG_KASAN_VMALLOC``, KASAN can cover vmalloc space at the
 cost of greater memory usage. Currently this supported on x86, s390
-and 32-bit powerpc. It is optional, except on 32-bit powerpc kernels
-with module support, where it is required.
+and powerpc. 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 e9f13fe08492..e6bd02af6ebd 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -180,7 +180,9 @@ 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_BOOK3S_64 && PPC_RADIX_MMU
+	select HAVE_ARCH_NO_KASAN_INLINE	if PPC_BOOK3S_64 && 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 b88900f4832f..60c1bba72a6f 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -396,5 +396,5 @@ config PPC_FAST_ENDIAN_SWITCH
 
 config KASAN_SHADOW_OFFSET
 	hex
-	depends on KASAN
+	depends on KASAN && PPC32
 	default 0xe0000000
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 73ad038ed10b..105b90594a8a 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 a39886681629..767e239d75e3 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -230,6 +230,13 @@ 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..c72fd9281b44 100644
--- a/arch/powerpc/include/asm/kasan.h
+++ b/arch/powerpc/include/asm/kasan.h
@@ -28,9 +28,41 @@
 #define KASAN_SHADOW_START	(KASAN_SHADOW_OFFSET + \
 				 (KASAN_KERN_START >> KASAN_SHADOW_SCALE_SHIFT))
 
+#ifdef CONFIG_KASAN_SHADOW_OFFSET
 #define KASAN_SHADOW_OFFSET	ASM_CONST(CONFIG_KASAN_SHADOW_OFFSET)
+#endif
 
+#ifdef CONFIG_PPC32
 #define KASAN_SHADOW_END	(-(-KASAN_SHADOW_START >> KASAN_SHADOW_SCALE_SHIFT))
+#endif
+
+#ifdef CONFIG_PPC_BOOK3S_64
+/*
+ * We define the  offset such that the shadow of the linear map lives
+ * at the end of vmemmap space, that is, we choose offset such that
+ * shadow(c000_0000_0000_0000) = c00e_0000_0000_0000. This gives:
+ * c00e000000000000 - c000000000000000 >> 3 = a80e000000000000
+ */
+#define KASAN_SHADOW_OFFSET ASM_CONST(0xa80e000000000000)
+
+/*
+ * 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 inline bool kasan_arch_is_ready_ppc64(void)
+{
+	if (static_branch_likely(&powerpc_kasan_enabled_key))
+		return true;
+	return false;
+}
+
+#define kasan_arch_is_ready kasan_arch_is_ready_ppc64
+#endif
 
 #ifdef CONFIG_KASAN
 void kasan_early_init(void);
@@ -47,5 +79,5 @@ void kasan_update_early_region(unsigned long k_start, unsigned long k_end, pte_t
 int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end);
 int kasan_init_region(void *start, size_t size);
 
-#endif /* __ASSEMBLY */
+#endif /* !__ASSEMBLY__ */
 #endif
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index fe2ef598e2ea..cd58202459dd 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -32,6 +32,11 @@ 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_traps.o := n
+KASAN_SANITIZE_mce_power.o := n
 
 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 d421a2c7f822..f02b2766015c 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -2151,8 +2151,8 @@ 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);
@@ -2170,14 +2170,16 @@ 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_INT_FRAME_SIZE)
-		    && stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
+		if (validate_sp(sp, tsk, STACK_INT_FRAME_SIZE) &&
+		    (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    LR = %pS\n",
-			       loglvl, regs->trap,
-			       (void *)regs->nip, (void *)lr);
+			       loglvl, READ_ONCE_NOCHECK(regs->trap),
+			       (void *)READ_ONCE_NOCHECK(regs->nip),
+			       (void *)READ_ONCE_NOCHECK(lr));
 			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 += $(kvm-book3s_64-builtin-objs-y)
+
+# KVM does a lot in real-mode, and 64-bit Book3S KASAN doesn't support that
+ifdef CONFIG_PPC_BOOK3S_64
+KASAN_SANITIZE := n
+endif
diff --git a/arch/powerpc/mm/book3s64/Makefile b/arch/powerpc/mm/book3s64/Makefile
index fd393b8be14f..41a86d2c7da4 100644
--- a/arch/powerpc/mm/book3s64/Makefile
+++ b/arch/powerpc/mm/book3s64/Makefile
@@ -21,3 +21,11 @@ obj-$(CONFIG_PPC_MEM_KEYS)	+= 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
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..b26ada73215d
--- /dev/null
+++ b/arch/powerpc/mm/kasan/init_book3s_64.c
@@ -0,0 +1,98 @@
+// 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) {
+		map_kernel_page(k_cur, __pa(va), PAGE_KERNEL);
+		va += PAGE_SIZE;
+	}
+}
+
+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 c194c4ae8bc7..b6eb8ec1e5ad 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -92,6 +92,7 @@ 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
-- 
2.25.1

Re: [PATCH v9 1/6] kasan: allow an architecture to disable inline instrumentation

[Christophe Leroy]

Le 01/12/2020 à 17:16, Daniel Axtens a écrit :
> For annoying architectural reasons, it's very difficult to support inline
> instrumentation on powerpc64.
> 
> Add a Kconfig flag to allow an arch to disable inline. (It's a bit
> annoying to be 'backwards', but I'm not aware of any way to have
> an arch force a symbol to be 'n', rather than 'y'.)
> 
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> ---
>   lib/Kconfig.kasan | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index 542a9c18398e..31a0b28f6c2b 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -9,6 +9,9 @@ config HAVE_ARCH_KASAN_SW_TAGS
>   config	HAVE_ARCH_KASAN_VMALLOC
>   	bool
>   
> +config HAVE_ARCH_NO_KASAN_INLINE

Maybe a better name could be: ARCH_DISABLE_KASAN_INLINE

> +	def_bool n
> +
>   config CC_HAS_KASAN_GENERIC
>   	def_bool $(cc-option, -fsanitize=kernel-address)
>   
> @@ -108,6 +111,7 @@ config KASAN_OUTLINE
>   
>   config KASAN_INLINE
>   	bool "Inline instrumentation"
> +	depends on !HAVE_ARCH_NO_KASAN_INLINE
>   	help
>   	  Compiler directly inserts code checking shadow memory before
>   	  memory accesses. This is faster than outline (in some workloads
> 

Re: [PATCH v9 2/6] kasan: allow architectures to provide an outline readiness check

[Christophe Leroy]

Le 01/12/2020 à 17:16, Daniel Axtens a écrit :
> Allow architectures to define a kasan_arch_is_ready() hook that bails
> out of any function that's about to touch the shadow unless the arch
> says that it is ready for the memory to be accessed. This is fairly
> uninvasive and should have a negligible performance penalty.
> 
> This will only work in outline mode, so an arch must specify
> HAVE_ARCH_NO_KASAN_INLINE if it requires this.
> 
> Cc: Balbir Singh <bsingharora@gmail.com>
> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Did I signed that off one day ? I can't remember.

Please update my email address, and maybe change it to a Suggested-by: ? I think the first 
Signed-off-by: has to be the author of the patch.

> Signed-off-by: Daniel Axtens <dja@axtens.net>
> 
> --
> 
> I discuss the justfication for this later in the series. Also,
> both previous RFCs for ppc64 - by 2 different people - have
> needed this trick! See:
>   - https://lore.kernel.org/patchwork/patch/592820/ # ppc64 hash series
>   - https://patchwork.ozlabs.org/patch/795211/      # ppc radix series
> ---
>   include/linux/kasan.h |  4 ++++
>   mm/kasan/common.c     | 10 ++++++++++
>   mm/kasan/generic.c    |  3 +++
>   3 files changed, 17 insertions(+)
> 
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 30d343b4a40a..3df66fdf6662 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -20,6 +20,10 @@ struct kunit_kasan_expectation {
>   	bool report_found;
>   };
>   
> +#ifndef kasan_arch_is_ready
> +static inline bool kasan_arch_is_ready(void)	{ return true; }
> +#endif
> +
>   extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
>   extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
>   extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 950fd372a07e..ba7744d3e319 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -117,6 +117,9 @@ void kasan_poison_shadow(const void *address, size_t size, u8 value)
>   {
>   	void *shadow_start, *shadow_end;
>   
> +	if (!kasan_arch_is_ready())
> +		return;
> +
>   	/*
>   	 * Perform shadow offset calculation based on untagged address, as
>   	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
> @@ -134,6 +137,9 @@ void kasan_unpoison_shadow(const void *address, size_t size)
>   {
>   	u8 tag = get_tag(address);
>   
> +	if (!kasan_arch_is_ready())
> +		return;
> +
>   	/*
>   	 * Perform shadow offset calculation based on untagged address, as
>   	 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
> @@ -406,6 +412,10 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
>   	if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
>   		return false;
>   
> +	/* We can't read the shadow byte if the arch isn't ready */
> +	if (!kasan_arch_is_ready())
> +		return false;
> +
>   	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
>   	if (shadow_invalid(tag, shadow_byte)) {
>   		kasan_report_invalid_free(tagged_object, ip);
> diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
> index 248264b9cb76..e87404026b2b 100644
> --- a/mm/kasan/generic.c
> +++ b/mm/kasan/generic.c
> @@ -169,6 +169,9 @@ static __always_inline bool check_memory_region_inline(unsigned long addr,
>   						size_t size, bool write,
>   						unsigned long ret_ip)
>   {
> +	if (!kasan_arch_is_ready())
> +		return true;
> +
>   	if (unlikely(size == 0))
>   		return true;
>   
> 

Re: [PATCH v9 3/6] kasan: define and use MAX_PTRS_PER_* for early shadow tables

[Christophe Leroy]

Le 01/12/2020 à 17:16, Daniel Axtens a écrit :
> powerpc has a variable number of PTRS_PER_*, set at runtime based
> on the MMU that the kernel is booted under.
> 
> This means the PTRS_PER_* are no longer constants, and therefore
> breaks the build.
> 
> Define default MAX_PTRS_PER_*s in the same style as MAX_PTRS_PER_P4D.
> As KASAN is the only user at the moment, just define them in the kasan
> header, and have them default to PTRS_PER_* unless overridden in arch
> code.
> 
> Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>

My neww address is : christophe.leroy@csgroup.eu

> Suggested-by: Balbir Singh <bsingharora@gmail.com>
> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>

Same

> Reviewed-by: Balbir Singh <bsingharora@gmail.com>
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> ---
>   include/linux/kasan.h | 18 +++++++++++++++---
>   mm/kasan/init.c       |  6 +++---
>   2 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 3df66fdf6662..893d054aad6f 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -24,10 +24,22 @@ struct kunit_kasan_expectation {
>   static inline bool kasan_arch_is_ready(void)	{ return true; }
>   #endif
>   
> +#ifndef MAX_PTRS_PER_PTE
> +#define MAX_PTRS_PER_PTE PTRS_PER_PTE
> +#endif
> +
> +#ifndef MAX_PTRS_PER_PMD
> +#define MAX_PTRS_PER_PMD PTRS_PER_PMD
> +#endif
> +
> +#ifndef MAX_PTRS_PER_PUD
> +#define MAX_PTRS_PER_PUD PTRS_PER_PUD
> +#endif
> +
>   extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
> -extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
> -extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
> -extern pud_t kasan_early_shadow_pud[PTRS_PER_PUD];
> +extern pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE];
> +extern pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD];
> +extern pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD];
>   extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
>   
>   int kasan_populate_early_shadow(const void *shadow_start,
> diff --git a/mm/kasan/init.c b/mm/kasan/init.c
> index fe6be0be1f76..42bca3d27db8 100644
> --- a/mm/kasan/init.c
> +++ b/mm/kasan/init.c
> @@ -46,7 +46,7 @@ static inline bool kasan_p4d_table(pgd_t pgd)
>   }
>   #endif
>   #if CONFIG_PGTABLE_LEVELS > 3
> -pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
> +pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
>   static inline bool kasan_pud_table(p4d_t p4d)
>   {
>   	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
> @@ -58,7 +58,7 @@ static inline bool kasan_pud_table(p4d_t p4d)
>   }
>   #endif
>   #if CONFIG_PGTABLE_LEVELS > 2
> -pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
> +pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
>   static inline bool kasan_pmd_table(pud_t pud)
>   {
>   	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
> @@ -69,7 +69,7 @@ static inline bool kasan_pmd_table(pud_t pud)
>   	return false;
>   }
>   #endif
> -pte_t kasan_early_shadow_pte[PTRS_PER_PTE] __page_aligned_bss;
> +pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE] __page_aligned_bss;
>   
>   static inline bool kasan_pte_table(pmd_t pmd)
>   {
> 

Re: [PATCH v9 4/6] kasan: Document support on 32-bit powerpc

[Christophe Leroy]

Le 01/12/2020 à 17:16, Daniel Axtens a écrit :
> KASAN is supported on 32-bit powerpc and the docs should reflect this.
> 
> Document s390 support while we're at it.
> 
> Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>

My new address is <christophe.leroy@csgroup.eu>

> Signed-off-by: Daniel Axtens <dja@axtens.net>
> ---
>   Documentation/dev-tools/kasan.rst |  7 +++++--
>   Documentation/powerpc/kasan.txt   | 12 ++++++++++++
>   2 files changed, 17 insertions(+), 2 deletions(-)
>   create mode 100644 Documentation/powerpc/kasan.txt
> 
> diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
> index 2b68addaadcd..eaf868094a8e 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -19,7 +19,8 @@ out-of-bounds accesses for global variables is only supported since Clang 11.
>   Tag-based KASAN is only supported in Clang.
>   
>   Currently generic KASAN is supported for the x86_64, arm64, xtensa, s390 and
> -riscv architectures, and tag-based KASAN is supported only for arm64.
> +riscv architectures. It is also supported on 32-bit powerpc kernels. Tag-based
> +KASAN is supported only on arm64.
>   
>   Usage
>   -----
> @@ -255,7 +256,9 @@ CONFIG_KASAN_VMALLOC
>   ~~~~~~~~~~~~~~~~~~~~
>   
>   With ``CONFIG_KASAN_VMALLOC``, KASAN can cover vmalloc space at the
> -cost of greater memory usage. Currently this is only supported on x86.
> +cost of greater memory usage. Currently this supported on x86, s390
> +and 32-bit powerpc. It is optional, except 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
> new file mode 100644
> index 000000000000..26bb0e8bb18c
> --- /dev/null
> +++ b/Documentation/powerpc/kasan.txt
> @@ -0,0 +1,12 @@
> +KASAN is supported on powerpc on 32-bit only.
> +
> +32 bit support
> +==============
> +
> +KASAN is supported on both hash and nohash MMUs on 32-bit.
> +
> +The shadow area sits at the top of the kernel virtual memory space above the
> +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.
> 

Re: [PATCH v9 5/6] powerpc/mm/kasan: rename kasan_init_32.c to init_32.c

[Christophe Leroy]

Le 01/12/2020 à 17:16, Daniel Axtens a écrit :
> kasan is already implied by the directory name, we don't need to
> repeat it.
> 
> Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>

My new address is <christophe.leroy@csgroup.eu>


> Signed-off-by: Daniel Axtens <dja@axtens.net>
> ---
>   arch/powerpc/mm/kasan/Makefile                       | 2 +-
>   arch/powerpc/mm/kasan/{kasan_init_32.c => init_32.c} | 0
>   2 files changed, 1 insertion(+), 1 deletion(-)
>   rename arch/powerpc/mm/kasan/{kasan_init_32.c => init_32.c} (100%)
> 
> diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
> index bb1a5408b86b..42fb628a44fd 100644
> --- a/arch/powerpc/mm/kasan/Makefile
> +++ b/arch/powerpc/mm/kasan/Makefile
> @@ -2,6 +2,6 @@
>   
>   KASAN_SANITIZE := n
>   
> -obj-$(CONFIG_PPC32)           += kasan_init_32.o
> +obj-$(CONFIG_PPC32)           += init_32.o
>   obj-$(CONFIG_PPC_8xx)		+= 8xx.o
>   obj-$(CONFIG_PPC_BOOK3S_32)	+= book3s_32.o
> diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/init_32.c
> similarity index 100%
> rename from arch/powerpc/mm/kasan/kasan_init_32.c
> rename to arch/powerpc/mm/kasan/init_32.c
> 

Re: [PATCH v9 6/6] powerpc: Book3S 64-bit outline-only KASAN support

[Christophe Leroy]

Le 01/12/2020 à 17:16, Daniel Axtens a écrit :
> 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@c-s.fr> # ppc32 version
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> ---
>   Documentation/dev-tools/kasan.rst            |  9 +-
>   Documentation/powerpc/kasan.txt              | 48 +++++++++-
>   arch/powerpc/Kconfig                         |  4 +-
>   arch/powerpc/Kconfig.debug                   |  2 +-
>   arch/powerpc/include/asm/book3s/64/hash.h    |  4 +
>   arch/powerpc/include/asm/book3s/64/pgtable.h |  7 ++
>   arch/powerpc/include/asm/book3s/64/radix.h   | 13 ++-
>   arch/powerpc/include/asm/kasan.h             | 34 ++++++-
>   arch/powerpc/kernel/Makefile                 |  5 +
>   arch/powerpc/kernel/process.c                | 16 ++--
>   arch/powerpc/kvm/Makefile                    |  5 +
>   arch/powerpc/mm/book3s64/Makefile            |  8 ++
>   arch/powerpc/mm/kasan/Makefile               |  1 +
>   arch/powerpc/mm/kasan/init_book3s_64.c       | 98 ++++++++++++++++++++
>   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, 265 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 eaf868094a8e..28f08959bd2e 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -19,8 +19,9 @@ out-of-bounds accesses for global variables is only supported since Clang 11.
>   Tag-based KASAN is only supported in Clang.
>   
>   Currently generic KASAN is supported for the x86_64, arm64, xtensa, s390 and
> -riscv architectures. It is also supported on 32-bit powerpc kernels. Tag-based
> -KASAN is supported only on arm64.
> +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 is supported
> +only on arm64.
>   
>   Usage
>   -----
> @@ -257,8 +258,8 @@ CONFIG_KASAN_VMALLOC
>   
>   With ``CONFIG_KASAN_VMALLOC``, KASAN can cover vmalloc space at the
>   cost of greater memory usage. Currently this supported on x86, s390
> -and 32-bit powerpc. It is optional, except on 32-bit powerpc kernels
> -with module support, where it is required.
> +and powerpc. 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 e9f13fe08492..e6bd02af6ebd 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -180,7 +180,9 @@ 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_BOOK3S_64 && PPC_RADIX_MMU

PPC_RADIX_MMU already depends on PPC_BOOK3S_64 so 'if PPC_RADIX_MMU' would be enough

> +	select HAVE_ARCH_NO_KASAN_INLINE	if PPC_BOOK3S_64 && PPC_RADIX_MMU

This list must respect Alphabetical order.

> +	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 b88900f4832f..60c1bba72a6f 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -396,5 +396,5 @@ config PPC_FAST_ENDIAN_SWITCH
>   
>   config KASAN_SHADOW_OFFSET
>   	hex
> -	depends on KASAN
> +	depends on KASAN && PPC32
>   	default 0xe0000000

Instead of the above, why not doing:

	default 0xe0000000 if PPC32
	default 0xa80e000000000000 is PPC_BOOK3S_64

> diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
> index 73ad038ed10b..105b90594a8a 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 a39886681629..767e239d75e3 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -230,6 +230,13 @@ 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)

Nowadays we allow 100 chars per line. Could this fit on a single line ?

> +#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..c72fd9281b44 100644
> --- a/arch/powerpc/include/asm/kasan.h
> +++ b/arch/powerpc/include/asm/kasan.h
> @@ -28,9 +28,41 @@
>   #define KASAN_SHADOW_START	(KASAN_SHADOW_OFFSET + \
>   				 (KASAN_KERN_START >> KASAN_SHADOW_SCALE_SHIFT))
>   
> +#ifdef CONFIG_KASAN_SHADOW_OFFSET
>   #define KASAN_SHADOW_OFFSET	ASM_CONST(CONFIG_KASAN_SHADOW_OFFSET)
> +#endif
>   
> +#ifdef CONFIG_PPC32
>   #define KASAN_SHADOW_END	(-(-KASAN_SHADOW_START >> KASAN_SHADOW_SCALE_SHIFT))
> +#endif
> +
> +#ifdef CONFIG_PPC_BOOK3S_64
> +/*
> + * We define the  offset such that the shadow of the linear map lives
> + * at the end of vmemmap space, that is, we choose offset such that
> + * shadow(c000_0000_0000_0000) = c00e_0000_0000_0000. This gives:
> + * c00e000000000000 - c000000000000000 >> 3 = a80e000000000000
> + */
> +#define KASAN_SHADOW_OFFSET ASM_CONST(0xa80e000000000000)

Why can't you use CONFIG_KASAN_SHADOW_OFFSET ?

> +
> +/*
> + * 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

I think we should be able to have a common formula for PPC32 and PPC64.

> +
> +DECLARE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
> +
> +static inline bool kasan_arch_is_ready_ppc64(void)

I'd make it __always_inline

> +{
> +	if (static_branch_likely(&powerpc_kasan_enabled_key))
> +		return true;
> +	return false;
> +}
> +
> +#define kasan_arch_is_ready kasan_arch_is_ready_ppc64

Usually we keep the generic name, you don't need to have an arch specific name.

> +#endif
>   
>   #ifdef CONFIG_KASAN
>   void kasan_early_init(void);
> @@ -47,5 +79,5 @@ void kasan_update_early_region(unsigned long k_start, unsigned long k_end, pte_t
>   int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end);
>   int kasan_init_region(void *start, size_t size);
>   
> -#endif /* __ASSEMBLY */
> +#endif /* !__ASSEMBLY__ */

This patch is already big. Is that worth it ?

>   #endif
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index fe2ef598e2ea..cd58202459dd 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -32,6 +32,11 @@ 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

The entire setup_64 ?
Can you split things out into an early_64.o like was done for ppc32 ?

> +KASAN_SANITIZE_mce.o := n
> +KASAN_SANITIZE_traps.o := n

Why ? ppc32 doesn't need that.

> +KASAN_SANITIZE_mce_power.o := n
>   
>   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 d421a2c7f822..f02b2766015c 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -2151,8 +2151,8 @@ 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);
> @@ -2170,14 +2170,16 @@ 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_INT_FRAME_SIZE)
> -		    && stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
> +		if (validate_sp(sp, tsk, STACK_INT_FRAME_SIZE) &&
> +		    (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    LR = %pS\n",
> -			       loglvl, regs->trap,
> -			       (void *)regs->nip, (void *)lr);
> +			       loglvl, READ_ONCE_NOCHECK(regs->trap),
> +			       (void *)READ_ONCE_NOCHECK(regs->nip),
> +			       (void *)READ_ONCE_NOCHECK(lr));
>   			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 += $(kvm-book3s_64-builtin-objs-y)
> +
> +# KVM does a lot in real-mode, and 64-bit Book3S KASAN doesn't support that
> +ifdef CONFIG_PPC_BOOK3S_64
> +KASAN_SANITIZE := n
> +endif
> diff --git a/arch/powerpc/mm/book3s64/Makefile b/arch/powerpc/mm/book3s64/Makefile
> index fd393b8be14f..41a86d2c7da4 100644
> --- a/arch/powerpc/mm/book3s64/Makefile
> +++ b/arch/powerpc/mm/book3s64/Makefile
> @@ -21,3 +21,11 @@ obj-$(CONFIG_PPC_MEM_KEYS)	+= 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
> 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..b26ada73215d
> --- /dev/null
> +++ b/arch/powerpc/mm/kasan/init_book3s_64.c
> @@ -0,0 +1,98 @@
> +// 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) {
> +		map_kernel_page(k_cur, __pa(va), PAGE_KERNEL);
> +		va += PAGE_SIZE;
> +	}

What about:

	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);
> +	}

No need of { } for single line loops. Check the kernel codyign stype


> +
> +	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

Why do you need that ? When PTEs are all pointing to the same page, it shoud already appear in a 
single line into []

> +
>   	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 c194c4ae8bc7..b6eb8ec1e5ad 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -92,6 +92,7 @@ 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
> 

Christophe

Re: [PATCH v9 0/6] KASAN for powerpc64 radix

[Andrey Konovalov]

On Tue, Dec 1, 2020 at 5:16 PM Daniel Axtens <dja@axtens.net> wrote:
>
> Building on the work of Christophe, Aneesh and Balbir, I've ported
> KASAN to 64-bit Book3S kernels running on the Radix MMU.
>
> This is a significant reworking of the previous versions. Instead of
> the previous approach which supported inline instrumentation, this
> series provides only outline instrumentation.
>
> To get around the problem of accessing the shadow region inside code we run
> with translations off (in 'real mode'), we we restrict checking to when
> translations are enabled. This is done via a new hook in the kasan core and
> by excluding larger quantites of arch code from instrumentation. The upside
> is that we no longer require that you be able to specify the amount of
> physically contiguous memory on the system at compile time. Hopefully this
> is a better trade-off. More details in patch 6.
>
> kexec works. Both 64k and 4k pages work. Running as a KVM host works, but
> nothing in arch/powerpc/kvm is instrumented. It's also potentially a bit
> fragile - if any real mode code paths call out to instrumented code, things
> will go boom.
>
> There are 4 failing KUnit tests:
>
> kasan_stack_oob, kasan_alloca_oob_left & kasan_alloca_oob_right - these are
> due to not supporting inline instrumentation.
>
> kasan_global_oob - gcc puts the ASAN init code in a section called
> '.init_array'. Powerpc64 module loading code goes through and _renames_ any
> section beginning with '.init' to begin with '_init' in order to avoid some
> complexities around our 24-bit indirect jumps. This means it renames
> '.init_array' to '_init_array', and the generic module loading code then
> fails to recognise the section as a constructor and thus doesn't run
> it. This hack dates back to 2003 and so I'm not going to try to unpick it
> in this series. (I suspect this may have previously worked if the code
> ended up in .ctors rather than .init_array but I don't keep my old binaries
> around so I have no real way of checking.)

Hi Daniel,

Just FYI: there's a number of KASAN-related patches in the mm tree
right now, so this series will need to be rebased. Onto mm or onto
5.11-rc1 one it's been released.

Thanks!

Re: [PATCH v9 6/6] powerpc: Book3S 64-bit outline-only KASAN support

[Daniel Axtens]

Hi Christophe,

>>   	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_BOOK3S_64 && PPC_RADIX_MMU
>
> PPC_RADIX_MMU already depends on PPC_BOOK3S_64 so 'if PPC_RADIX_MMU' would be enough

Done.

>> +	select HAVE_ARCH_NO_KASAN_INLINE	if PPC_BOOK3S_64 && PPC_RADIX_MMU
>
> This list must respect Alphabetical order.

Fixed.

>
>> +	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 b88900f4832f..60c1bba72a6f 100644
>> --- a/arch/powerpc/Kconfig.debug
>> +++ b/arch/powerpc/Kconfig.debug
>> @@ -396,5 +396,5 @@ config PPC_FAST_ENDIAN_SWITCH
>>   
>>   config KASAN_SHADOW_OFFSET
>>   	hex
>> -	depends on KASAN
>> +	depends on KASAN && PPC32
>>   	default 0xe0000000
>
> Instead of the above, why not doing:
>
> 	default 0xe0000000 if PPC32
> 	default 0xa80e000000000000 is PPC_BOOK3S_64

Done. I just used PPC64.

>
>> diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
>> index 73ad038ed10b..105b90594a8a 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 a39886681629..767e239d75e3 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -230,6 +230,13 @@ 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)
>
> Nowadays we allow 100 chars per line. Could this fit on a single line ?

Yes, so long as we drop the tab between the name and the definition and
replace it with a single space.

>> +#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)

>> +#ifdef CONFIG_PPC32
>>   #define KASAN_SHADOW_END	(-(-KASAN_SHADOW_START >> KASAN_SHADOW_SCALE_SHIFT))
>> +#endif
>> +
>> +#ifdef CONFIG_PPC_BOOK3S_64
>> +/*
>> + * We define the  offset such that the shadow of the linear map lives
>> + * at the end of vmemmap space, that is, we choose offset such that
>> + * shadow(c000_0000_0000_0000) = c00e_0000_0000_0000. This gives:
>> + * c00e000000000000 - c000000000000000 >> 3 = a80e000000000000
>> + */
>> +#define KASAN_SHADOW_OFFSET ASM_CONST(0xa80e000000000000)
>
> Why can't you use CONFIG_KASAN_SHADOW_OFFSET ?

I didn't do this earlier due to some interesting interactions in the
generic configuration. The generic Kconfig/Makefile will turn on stack
instrumentation if CONFIG_KASAN_SHADOW_OFFSET is set. This, however,
creates a bunch of inline code that crashes on ppc64 when it runs
translations off.

I've made changes to the patch that introduces ARCH_DISABLE_KASAN_INLINE
to fix this, and converted to using CONFIG_KASAN_SHADOW_OFFSET.

>> +
>> +/*
>> + * 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
>
> I think we should be able to have a common formula for PPC32 and PPC64.
>

Perhaps, but I can't figure out what it would be. For PPC64,
end = start + (size of kernel space + vmalloc space + ioremap space + vmemmap space) >> 3
For PPC32, AIUI you don't have vmemmap space so I'm not sure how to
calculate it.

>> +
>> +DECLARE_STATIC_KEY_FALSE(powerpc_kasan_enabled_key);
>> +
>> +static inline bool kasan_arch_is_ready_ppc64(void)
>
> I'd make it __always_inline

Done.

>> +{
>> +	if (static_branch_likely(&powerpc_kasan_enabled_key))
>> +		return true;
>> +	return false;
>> +}
>> +
>> +#define kasan_arch_is_ready kasan_arch_is_ready_ppc64
>
> Usually we keep the generic name, you don't need to have an arch specific name.

Done.

>> +#endif
>>   
>>   #ifdef CONFIG_KASAN
>>   void kasan_early_init(void);
>> @@ -47,5 +79,5 @@ void kasan_update_early_region(unsigned long k_start, unsigned long k_end, pte_t
>>   int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end);
>>   int kasan_init_region(void *start, size_t size);
>>   
>> -#endif /* __ASSEMBLY */
>> +#endif /* !__ASSEMBLY__ */
>
> This patch is already big. Is that worth it ?

Fair enough. Dropped.

>>   #endif
>> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
>> index fe2ef598e2ea..cd58202459dd 100644
>> --- a/arch/powerpc/kernel/Makefile
>> +++ b/arch/powerpc/kernel/Makefile
>> @@ -32,6 +32,11 @@ 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
>
> The entire setup_64 ?
> Can you split things out into an early_64.o like was done for ppc32 ?

setup_64.c contains around 40 functions, of which about half are not __init:

cpu_ready_for_interrupts

smp setup/maintenance functions:
 early_setup_secondary
 panic_smp_self_stop
 use_spinloop
 smp_release_cpus
(Some of these we couldn't instrument anyway as they use real addresses.)

Functions which AFAICT should be marked __init, as they're static and
only called from __init functions:
 init_cache_info
 pcpu_cpu_distance

Tiny functions:
 memory_block_size_bytes
 hw_nmi_get_sample_period

Flush maintenance:
 do_nothing (an empty function)
 init_fallback_flush
 setup_{rfi,entry,uaccess}_flush (3 functions)
 {rfi,entry,uaccess}_flush_{get,set,enable} (9 functions)

We don't really get much value from instrumenting any of these, but we
could split out at least the flush maintenance ones if we really wanted
to.

I'd say there isn't enough value in moving them to justify the churn but
I'm happy to move them if people feel differently.

>> +KASAN_SANITIZE_mce.o := n
>> +KASAN_SANITIZE_traps.o := n
>
> Why ? ppc32 doesn't need that.

Some of that code runs with translations off. If we try to access the
shadow region with translations off, things will crash. This is part of
what I gave up in order to be able to have the one kernel binary work
regardless of the quantity of physical memory.

Only traps.c is compiled for ppc32, I'll wrap it so that it's still
instrumented there.

> +KASAN_SANITIZE_mce_power.o := n
>>   
>>   ifdef CONFIG_KASAN
>>   CFLAGS_early_32.o += -DDISABLE_BRANCH_PROFILING

>> +
>> +	va = memblock_alloc(k_end - k_start, PAGE_SIZE);
>> +	for (k_cur = k_start; k_cur < k_end; k_cur += PAGE_SIZE) {
>> +		map_kernel_page(k_cur, __pa(va), PAGE_KERNEL);
>> +		va += PAGE_SIZE;
>> +	}
>
> What about:
>
> 	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);
>

Done.

>> +}
>> +
>> +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);
>> +	}
>
> No need of { } for single line loops. Check the kernel codyign stype

Fixed.

>> +
>> +	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
>
> Why do you need that ? When PTEs are all pointing to the same page, it shoud already appear in a 
> single line into []

It would eventually be printed as one line, but first you have to
traverse ~7.5 billion PTEs. It's the process of walking that that takes
too long, not the printing.

Thanks for the review, I'll have a new spin out soon.

Kind regards,
Daniel