[PATCH v7 0/4] KASAN for powerpc64 radix

[PATCH v7 0/4] 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 provides full inline instrumentation on radix, but does require
that you be able to specify the amount of physically contiguous memory
on the system at compile time. More details in patch 4.

v7: Tweaks from Christophe, fix issues detected by snowpatch.

v6: Rebase on the latest changes in powerpc/merge. Minor tweaks
      to the documentation. Small tweaks to the header to work
      with the kasan_late_init() function that Christophe added
      for 32-bit kasan-vmalloc support.
    No functional change.

v5: ptdump support. More cleanups, tweaks and fixes, thanks
    Christophe. Details in patch 4.

    I have seen another stack walk splat, but I don't think it's
    related to the patch set, I think there's a bug somewhere else,
    probably in stack frame manipulation in the kernel or (more
    unlikely) in the compiler.

v4: More cleanups, split renaming out, clarify bits and bobs.
    Drop the stack walk disablement, that isn't needed. No other
    functional change.

v3: Reduce the overly ambitious scope of the MAX_PTRS change.
    Document more things, including around why some of the
    restrictions apply.
    Clean up the code more, thanks Christophe.

v2: The big change is the introduction of tree-wide(ish)
    MAX_PTRS_PER_{PTE,PMD,PUD} macros in preference to the previous
    approach, which was for the arch to override the page table array
    definitions with their own. (And I squashed the annoying
    intermittent crash!)

    Apart from that there's just a lot of cleanup. Christophe, I've
    addressed most of what you asked for and I will reply to your v1
    emails to clarify what remains unchanged.

[PATCH v7 1/4] 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 5cde9e7c2664..b3a4500633f5 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -14,10 +14,22 @@ struct task_struct;
 #include <asm/kasan.h>
 #include <asm/pgtable.h>
 
+#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 ce45c491ebcd..8b54a96d3b3e 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)
 {
-- 
2.20.1

[PATCH v7 2/4] 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>

---

Changes since v5:
 - rebase - riscv has now got support.
 - document s390 support while we're at it
 - clarify when kasan_vmalloc support is required
---
 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 c652d740735d..012ef3d91d1f 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -22,7 +22,8 @@ global variables yet.
 Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later.
 
 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.
-- 
2.20.1

[PATCH v7 3/4] 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 6577897673dd..36a4e1b10b2d 100644
--- a/arch/powerpc/mm/kasan/Makefile
+++ b/arch/powerpc/mm/kasan/Makefile
@@ -2,4 +2,4 @@
 
 KASAN_SANITIZE := n
 
-obj-$(CONFIG_PPC32)           += kasan_init_32.o
+obj-$(CONFIG_PPC32)           += init_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
-- 
2.20.1

[PATCH v7 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support

[Daniel Axtens]

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 in real mode after booting. Most notably a lot of KVM
   runs in real mode, and it would be good to be able to instrument it.

 - Because code runs in real mode after boot, the offset has to point to
   valid memory both in and out of real mode.

    [ppc64 mm note: The kernel installs a linear mapping at effective
    address c000... onward. 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.]

One approach is just to give up on inline instrumentation. This way all
checks can be delayed until after everything set is up correctly, and the
address-to-shadow calculations can be overridden. However, the features and
speed boost provided by inline instrumentation are worth trying to do
better.

If _at compile time_ it is known how much contiguous physical memory a
system has, the top 1/8th of the first block of physical memory can be set
aside for the shadow. This is a big hammer and comes with 3 big
consequences:

 - there's no nice way to handle physically discontiguous memory, so only
   the first physical memory block can be used.

 - kernels will simply fail to boot on machines with less memory than
   specified when compiling.

 - kernels running on machines with more memory than specified when
   compiling will simply ignore the extra memory.

Implement and document KASAN this way. The current implementation is Radix
only.

Despite the limitations, it can still find bugs,
e.g. http://patchwork.ozlabs.org/patch/1103775/

At the moment, this physical memory limit must be set _even for outline
mode_. This may be changed in a later series - a different implementation
could be added for outline mode that dynamically allocates shadow at a
fixed offset. For example, see https://patchwork.ozlabs.org/patch/795211/

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Balbir Singh <bsingharora@gmail.com> # ppc64 out-of-line radix version
Cc: Christophe Leroy <christophe.leroy@c-s.fr> # ppc32 version
Signed-off-by: Daniel Axtens <dja@axtens.net>

---
Changes since v6:
 - rework kasan_late_init support, which also fixes book3e problem that snowpatch
   picked up (I think)
 - fix a checkpatch error that snowpatch picked up
 - don't needlessly move the include in kasan.h

Changes since v5:
 - rebase on powerpc/merge, with Christophe's latest changes integrating
   kasan-vmalloc
 - documentation tweaks based on latest 32-bit changes

Changes since v4:
 - fix some ppc32 build issues
 - support ptdump
 - clean up the header file. It turns out we don't need or use KASAN_SHADOW_SIZE,
   so just dump it, and make KASAN_SHADOW_END the thing that varies between 32
   and 64 bit. As part of this, make sure KASAN_SHADOW_OFFSET is only configured for
   32 bit - it is calculated in the Makefile for ppc64.
 - various cleanups

Changes since v3:
 - Address further feedback from Christophe.
 - Drop changes to stack walking, it looks like the issue I observed is
   related to that particular stack, not stack-walking generally.

Changes since v2:

 - Address feedback from Christophe around cleanups and docs.
 - Address feedback from Balbir: at this point I don't have a good solution
   for the issues you identify around the limitations of the inline implementation
   but I think that it's worth trying to get the stack instrumentation support.
   I'm happy to have an alternative and more flexible outline mode - I had
   envisoned this would be called 'lightweight' mode as it imposes fewer restrictions.
   I've linked to your implementation. I think it's best to add it in a follow-up series.
 - Made the default PHYS_MEM_SIZE_FOR_KASAN value 1024MB. I think most people have
   guests with at least that much memory in the Radix 64s case so it's a much
   saner default - it means that if you just turn on KASAN without reading the
   docs you're much more likely to have a bootable kernel, which you will never
   have if the value is set to zero! I'm happy to bikeshed the value if we want.

Changes since v1:
 - Landed kasan vmalloc support upstream
 - Lots of feedback from Christophe.

Changes since the rfc:

 - Boots real and virtual hardware, kvm works.

 - disabled reporting when we're checking the stack for exception
   frames. The behaviour isn't wrong, just incompatible with KASAN.

 - Documentation!

 - Dropped old module stuff in favour of KASAN_VMALLOC.

The bugs with ftrace and kuap were due to kernel bloat pushing
prom_init calls to be done via the plt. Because we did not have
a relocatable kernel, and they are done very early, this caused
everything to explode. Compile with CONFIG_RELOCATABLE!
---
 Documentation/dev-tools/kasan.rst            |   9 +-
 Documentation/powerpc/kasan.txt              | 112 ++++++++++++++++++-
 arch/powerpc/Kconfig                         |   2 +
 arch/powerpc/Kconfig.debug                   |  23 +++-
 arch/powerpc/Makefile                        |  11 ++
 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   |   5 +
 arch/powerpc/include/asm/kasan.h             |  11 +-
 arch/powerpc/kernel/prom.c                   |  61 +++++++++-
 arch/powerpc/mm/kasan/Makefile               |   1 +
 arch/powerpc/mm/kasan/init_book3s_64.c       |  73 ++++++++++++
 arch/powerpc/mm/ptdump/ptdump.c              |  10 +-
 arch/powerpc/platforms/Kconfig.cputype       |   1 +
 14 files changed, 320 insertions(+), 10 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 012ef3d91d1f..5722de91ccce 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -22,8 +22,9 @@ global variables yet.
 Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later.
 
 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..bf645a5cd486 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 +10,113 @@ 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 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 in real mode after booting. Most notably a lot of KVM runs
+   in real mode, and it would be good to be able to instrument it.
+
+ - Because code runs in real mode after boot, the offset has to point to
+   valid memory both in and out of real mode.
+
+One approach is just to give up on inline instrumentation. This way all checks
+can be delayed until after everything set is up correctly, and the
+address-to-shadow calculations can be overridden. However, the features and
+speed boost provided by inline instrumentation are worth trying to do better.
+
+If _at compile time_ it is known how much contiguous physical memory a system
+has, the top 1/8th of the first block of physical memory can be set aside for
+the shadow. This is a big hammer and comes with 3 big consequences:
+
+ - there's no nice way to handle physically discontiguous memory, so only the
+   first physical memory block can be used.
+
+ - kernels will simply fail to boot on machines with less memory than specified
+   when compiling.
+
+ - kernels running on machines with more memory than specified when compiling
+   will simply ignore the extra memory.
+
+At the moment, this physical memory limit must be set _even for outline mode_.
+This may be changed in a future version - a different implementation could be
+added for outline mode that dynamically allocates shadow at a fixed offset.
+For example, see https://patchwork.ozlabs.org/patch/795211/
+
+This value is configured in CONFIG_PHYS_MEM_SIZE_FOR_KASAN.
+
+Tips
+----
+
+ - Compile with CONFIG_RELOCATABLE.
+
+   In development, boot hangs were observed when building with ftrace and KUAP
+   on. These ended up being due to kernel bloat pushing prom_init calls to be
+   done via the PLT. Because the kernel was not relocatable, and the calls are
+   done very early, this caused execution to jump off into somewhere
+   invalid. Enabling relocation fixes this.
+
+NUMA/discontiguous physical memory
+----------------------------------
+
+Currently the code cannot really deal with discontiguous physical memory. Only
+physical memory that is contiguous from physical address zero can be used. The
+size of that memory, not total memory, must be specified when configuring the
+kernel.
+
+Discontiguous memory can occur on machines with memory spread across multiple
+nodes. For example, on a Talos II with 64GB of RAM:
+
+ - 32GB runs from 0x0 to 0x0000_0008_0000_0000,
+ - then there's a gap,
+ - then the final 32GB runs from 0x0000_2000_0000_0000 to 0x0000_2008_0000_0000
+
+This can create _significant_ issues:
+
+ - If the machine is treated as having 64GB of _contiguous_ RAM, the
+   instrumentation would assume that it ran from 0x0 to
+   0x0000_0010_0000_0000. The last 1/8th - 0x0000_000e_0000_0000 to
+   0x0000_0010_0000_0000 would be reserved as the shadow region. But when the
+   kernel tried to access any of that, it would be trying to access pages that
+   are not physically present.
+
+ - If the shadow region size is based on the top address, then the shadow
+   region would be 0x2008_0000_0000 / 8 = 0x0401_0000_0000 bytes = 4100 GB of
+   memory, clearly more than the 64GB of RAM physically present.
+
+Therefore, the code currently is restricted to dealing with memory in the node
+starting at 0x0. For this system, that's 32GB. If a contiguous physical memory
+size greater than the size of the first contiguous region of memory is
+specified, the system will be unable to boot or even print an error message.
+
+The layout of a system's memory can be observed in the messages that the Radix
+MMU prints on boot. The Talos II discussed earlier has:
+
+radix-mmu: Mapped 0x0000000000000000-0x0000000040000000 with 1.00 GiB pages (exec)
+radix-mmu: Mapped 0x0000000040000000-0x0000000800000000 with 1.00 GiB pages
+radix-mmu: Mapped 0x0000200000000000-0x0000200800000000 with 1.00 GiB pages
+
+As discussed, this system would be configured for 32768 MB.
+
+Another system prints:
+
+radix-mmu: Mapped 0x0000000000000000-0x0000000040000000 with 1.00 GiB pages (exec)
+radix-mmu: Mapped 0x0000000040000000-0x0000002000000000 with 1.00 GiB pages
+radix-mmu: Mapped 0x0000200000000000-0x0000202000000000 with 1.00 GiB pages
+
+This machine has more memory: 0x0000_0040_0000_0000 total, but only
+0x0000_0020_0000_0000 is physically contiguous from zero, so it would be
+configured for 131072 MB of physically contiguous memory.
+
+This restriction currently also affects outline mode, but this could be
+changed in future if an alternative outline implementation is added.
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 497b7d0b2d7e..f1c54c08a88e 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -169,7 +169,9 @@ 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
+	select HAVE_ARCH_KASAN			if PPC_BOOK3S_64 && PPC_RADIX_MMU
 	select HAVE_ARCH_KASAN_VMALLOC		if PPC32
+	select HAVE_ARCH_KASAN_VMALLOC		if PPC_BOOK3S_64 && PPC_RADIX_MMU
 	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 0b063830eea8..faed301a3b10 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -394,7 +394,28 @@ config PPC_FAST_ENDIAN_SWITCH
 	help
 	  If you're unsure what this is, say N.
 
+config PHYS_MEM_SIZE_FOR_KASAN
+	int "Contiguous physical memory size for KASAN (MB)" if KASAN && PPC_BOOK3S_64
+	default 1024
+	help
+
+	  To get inline instrumentation support for KASAN on 64-bit Book3S
+	  machines, you need to know how much contiguous physical memory your
+	  system has. A shadow offset will be calculated based on this figure,
+	  which will be compiled in to the kernel. KASAN will use this offset
+	  to access its shadow region, which is used to verify memory accesses.
+
+	  If you attempt to boot on a system with less memory than you specify
+	  here, your system will fail to boot very early in the process. If you
+	  boot on a system with more memory than you specify, the extra memory
+	  will wasted - it will be reserved and not used.
+
+	  For systems with discontiguous blocks of physical memory, specify the
+	  size of the block starting at 0x0. You can determine this by looking
+	  at the memory layout info printed to dmesg by the radix MMU code
+	  early in boot. See Documentation/powerpc/kasan.txt.
+
 config KASAN_SHADOW_OFFSET
 	hex
-	depends on KASAN
+	depends on KASAN && PPC32
 	default 0xe0000000
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index f35730548e42..eb47dc768c0a 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -230,6 +230,17 @@ ifdef CONFIG_476FPE_ERR46
 		-T $(srctree)/arch/powerpc/platforms/44x/ppc476_modules.lds
 endif
 
+ifdef CONFIG_PPC_BOOK3S_64
+# The KASAN shadow offset is such that linear map (0xc000...) is shadowed by
+# the last 8th of linearly mapped physical memory. This way, if the code uses
+# 0xc addresses throughout, accesses work both in in real mode (where the top
+# bits are ignored) and outside of real mode.
+#
+# 0xc000000000000000 >> 3 = 0xa800000000000000 = 12105675798371893248
+KASAN_SHADOW_OFFSET = $(shell echo 7 \* 1024 \* 1024 \* $(CONFIG_PHYS_MEM_SIZE_FOR_KASAN) / 8 + 12105675798371893248 | bc)
+KBUILD_CFLAGS += -DKASAN_SHADOW_OFFSET=$(KASAN_SHADOW_OFFSET)UL
+endif
+
 # No AltiVec or VSX instructions when building kernel
 KBUILD_CFLAGS += $(call cc-option,-mno-altivec)
 KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index 2781ebf6add4..fce329b8452e 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 201a69e6a355..309fb925a96e 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -231,6 +231,13 @@ 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 d97db3ad9aae..4f826259de71 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.
  */
diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
index fbff9ff9032e..b21d3ef88214 100644
--- a/arch/powerpc/include/asm/kasan.h
+++ b/arch/powerpc/include/asm/kasan.h
@@ -21,11 +21,18 @@
 #define KASAN_SHADOW_START	(KASAN_SHADOW_OFFSET + \
 				 (PAGE_OFFSET >> 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	0UL
+#endif
 
-#define KASAN_SHADOW_SIZE	(KASAN_SHADOW_END - KASAN_SHADOW_START)
+#ifdef CONFIG_PPC_BOOK3S_64
+#define KASAN_SHADOW_END	(KASAN_SHADOW_OFFSET + \
+				 (RADIX_VMEMMAP_END >> KASAN_SHADOW_SCALE_SHIFT))
+#endif
 
 #ifdef CONFIG_KASAN
 void kasan_early_init(void);
@@ -38,5 +45,5 @@ static inline void kasan_mmu_init(void) { }
 static inline void kasan_late_init(void) { }
 #endif
 
-#endif /* __ASSEMBLY */
+#endif /* !__ASSEMBLY__ */
 #endif
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 6620f37abe73..2857c3d44e9c 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -72,6 +72,7 @@ unsigned long tce_alloc_start, tce_alloc_end;
 u64 ppc64_rma_size;
 #endif
 static phys_addr_t first_memblock_size;
+static phys_addr_t top_phys_addr;
 static int __initdata boot_cpu_count;
 
 static int __init early_parse_mem(char *p)
@@ -449,6 +450,26 @@ static bool validate_mem_limit(u64 base, u64 *size)
 {
 	u64 max_mem = 1UL << (MAX_PHYSMEM_BITS);
 
+	/*
+	 * To handle the NUMA/discontiguous memory case, don't allow a block
+	 * to be added if it falls completely beyond the configured physical
+	 * memory. Print an informational message.
+	 *
+	 * Frustratingly we also see this with qemu - it seems to split the
+	 * specified memory into a number of smaller blocks. If this happens
+	 * under qemu, it probably represents misconfiguration. So we want
+	 * the message to be noticeable, but not shouty.
+	 *
+	 * See Documentation/powerpc/kasan.txt
+	 */
+	if (IS_ENABLED(CONFIG_KASAN) &&
+	    (base >= ((u64)CONFIG_PHYS_MEM_SIZE_FOR_KASAN * SZ_1M))) {
+		pr_warn("KASAN: not adding memory block at %llx (size %llx)\n"
+			"This could be due to discontiguous memory or kernel misconfiguration.",
+			base, *size);
+		return false;
+	}
+
 	if (base >= max_mem)
 		return false;
 	if ((base + *size) > max_mem)
@@ -572,8 +593,10 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 
 	/* Add the chunk to the MEMBLOCK list */
 	if (add_mem_to_memblock) {
-		if (validate_mem_limit(base, &size))
+		if (validate_mem_limit(base, &size)) {
 			memblock_add(base, size);
+			top_phys_addr = max(top_phys_addr, (phys_addr_t)(base + size));
+		}
 	}
 }
 
@@ -613,6 +636,8 @@ static void __init early_reserve_mem_dt(void)
 static void __init early_reserve_mem(void)
 {
 	__be64 *reserve_map;
+	phys_addr_t kasan_shadow_start;
+	phys_addr_t kasan_memory_size;
 
 	reserve_map = (__be64 *)(((unsigned long)initial_boot_params) +
 			fdt_off_mem_rsvmap(initial_boot_params));
@@ -651,6 +676,40 @@ static void __init early_reserve_mem(void)
 		return;
 	}
 #endif
+
+	if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_PPC_BOOK3S_64)) {
+		kasan_memory_size =
+			((phys_addr_t)CONFIG_PHYS_MEM_SIZE_FOR_KASAN * SZ_1M);
+
+		if (top_phys_addr < kasan_memory_size) {
+			/*
+			 * We are doomed. We shouldn't even be able to get this
+			 * far, but we do in qemu. If we continue and turn
+			 * relocations on, we'll take fatal page faults for
+			 * memory that's not physically present. Instead,
+			 * panic() here: it will be saved to __log_buf even if
+			 * it doesn't get printed to the console.
+			 */
+			panic("Tried to boot a KASAN kernel configured for %u MB with only %llu MB! Aborting.",
+			      CONFIG_PHYS_MEM_SIZE_FOR_KASAN,
+			      (u64)(top_phys_addr * SZ_1M));
+		} else if (top_phys_addr > kasan_memory_size) {
+			/* print a biiiig warning in hopes people notice */
+			pr_err("===========================================\n"
+				"Physical memory exceeds compiled-in maximum!\n"
+				"This kernel was compiled for KASAN with %u MB physical memory.\n"
+				"The physical memory detected is at least %llu MB.\n"
+				"Memory above the compiled limit will not be used!\n"
+				"===========================================\n",
+				CONFIG_PHYS_MEM_SIZE_FOR_KASAN,
+				(u64)(top_phys_addr * SZ_1M));
+		}
+
+		kasan_shadow_start = _ALIGN_DOWN(kasan_memory_size * 7 / 8, PAGE_SIZE);
+		DBG("reserving %llx -> %llx for KASAN",
+		    kasan_shadow_start, top_phys_addr);
+		memblock_reserve(kasan_shadow_start, top_phys_addr - kasan_shadow_start);
+	}
 }
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
index 36a4e1b10b2d..f02b15c78e4d 100644
--- a/arch/powerpc/mm/kasan/Makefile
+++ b/arch/powerpc/mm/kasan/Makefile
@@ -3,3 +3,4 @@
 KASAN_SANITIZE := n
 
 obj-$(CONFIG_PPC32)           += init_32.o
+obj-$(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..1c95fe6495c7
--- /dev/null
+++ b/arch/powerpc/mm/kasan/init_book3s_64.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KASAN for 64-bit Book3S powerpc
+ *
+ * Copyright (C) 2019 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 <asm/pgalloc.h>
+
+void __init kasan_init(void)
+{
+	int i;
+	void *k_start = kasan_mem_to_shadow((void *)RADIX_KERN_VIRT_START);
+	void *k_end = kasan_mem_to_shadow((void *)RADIX_VMEMMAP_END);
+
+	pte_t pte =  pte_mkpte(pfn_pte(virt_to_pfn(kasan_early_shadow_page),
+				       PAGE_KERNEL));
+
+	if (!early_radix_enabled())
+		panic("KASAN requires radix!");
+
+	for (i = 0; i < PTRS_PER_PTE; i++)
+		__set_pte_at(&init_mm, (unsigned long)kasan_early_shadow_page,
+			     &kasan_early_shadow_pte[i], 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);
+
+	memset((void *)KASAN_SHADOW_START, KASAN_SHADOW_INIT,
+	       ((u64)CONFIG_PHYS_MEM_SIZE_FOR_KASAN *
+		     SZ_1M >> KASAN_SHADOW_SCALE_SHIFT));
+
+	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)RADIX_KERN_VIRT_START),
+				    kasan_mem_to_shadow((void *)RADIX_VMALLOC_START));
+
+	/* leave a hole here for vmalloc */
+
+	kasan_populate_early_shadow(
+		kasan_mem_to_shadow((void *)RADIX_VMALLOC_END),
+		kasan_mem_to_shadow((void *)RADIX_VMEMMAP_END));
+
+	flush_tlb_kernel_range((unsigned long)k_start, (unsigned long)k_end);
+
+	/* mark early shadow region as RO and wipe */
+	pte = pte_mkpte(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], 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);
+
+	/* Enable error messages */
+	init_task.kasan_depth = 0;
+	pr_info("KASAN init done (64-bit Book3S heavyweight mode)\n");
+}
+
+void __init kasan_late_init(void) { }
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index 206156255247..b982dc5441c0 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -73,6 +73,10 @@ struct addr_marker {
 
 static struct addr_marker address_markers[] = {
 	{ 0,	"Start of kernel VM" },
+#if defined(CONFIG_PPC64) && defined(CONFIG_KASAN)
+	{ 0,	"kasan shadow mem start" },
+	{ 0,	"kasan shadow mem end" },
+#endif
 	{ 0,	"vmalloc() Area" },
 	{ 0,	"vmalloc() End" },
 #ifdef CONFIG_PPC64
@@ -92,10 +96,10 @@ static struct addr_marker address_markers[] = {
 #endif
 	{ 0,	"Fixmap start" },
 	{ 0,	"Fixmap end" },
-#endif
 #ifdef CONFIG_KASAN
 	{ 0,	"kasan shadow mem start" },
 	{ 0,	"kasan shadow mem end" },
+#endif
 #endif
 	{ -1,	NULL },
 };
@@ -317,6 +321,10 @@ static void populate_markers(void)
 	int i = 0;
 
 	address_markers[i++].start_address = PAGE_OFFSET;
+#if defined(CONFIG_PPC64) && defined(CONFIG_KASAN)
+	address_markers[i++].start_address = KASAN_SHADOW_START;
+	address_markers[i++].start_address = KASAN_SHADOW_END;
+#endif
 	address_markers[i++].start_address = VMALLOC_START;
 	address_markers[i++].start_address = VMALLOC_END;
 #ifdef CONFIG_PPC64
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 6caedc88474f..cedc86686e65 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -99,6 +99,7 @@ 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"
-- 
2.20.1

Re: [PATCH v7 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support

[Christophe Leroy]

Le 13/02/2020 à 01:47, Daniel Axtens a écrit :
> 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 in real mode after booting. Most notably a lot of KVM
>     runs in real mode, and it would be good to be able to instrument it.
> 
>   - Because code runs in real mode after boot, the offset has to point to
>     valid memory both in and out of real mode.
> 
>      [ppc64 mm note: The kernel installs a linear mapping at effective
>      address c000... onward. 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.]
> 
> One approach is just to give up on inline instrumentation. This way all
> checks can be delayed until after everything set is up correctly, and the
> address-to-shadow calculations can be overridden. However, the features and
> speed boost provided by inline instrumentation are worth trying to do
> better.
> 
> If _at compile time_ it is known how much contiguous physical memory a
> system has, the top 1/8th of the first block of physical memory can be set
> aside for the shadow. This is a big hammer and comes with 3 big
> consequences:
> 
>   - there's no nice way to handle physically discontiguous memory, so only
>     the first physical memory block can be used.
> 
>   - kernels will simply fail to boot on machines with less memory than
>     specified when compiling.
> 
>   - kernels running on machines with more memory than specified when
>     compiling will simply ignore the extra memory.
> 
> Implement and document KASAN this way. The current implementation is Radix
> only.
> 
> Despite the limitations, it can still find bugs,
> e.g. http://patchwork.ozlabs.org/patch/1103775/
> 
> At the moment, this physical memory limit must be set _even for outline
> mode_. This may be changed in a later series - a different implementation
> could be added for outline mode that dynamically allocates shadow at a
> fixed offset. For example, see https://patchwork.ozlabs.org/patch/795211/
> 
> Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Balbir Singh <bsingharora@gmail.com> # ppc64 out-of-line radix version
> Cc: Christophe Leroy <christophe.leroy@c-s.fr> # ppc32 version
> Signed-off-by: Daniel Axtens <dja@axtens.net>

Reviewed-by: <christophe.leroy@c-s.fr> # focussed mainly on 
Documentation and things impacting PPC32

Re: [PATCH v7 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support

[Christophe Leroy]

Le 13/02/2020 à 01:47, Daniel Axtens a écrit :
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 497b7d0b2d7e..f1c54c08a88e 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -169,7 +169,9 @@ 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
> +	select HAVE_ARCH_KASAN			if PPC_BOOK3S_64 && PPC_RADIX_MMU

That's probably detail, but as it is necessary to deeply define the HW 
when selecting that (I mean giving the exact amount of memory and with 
restrictions like having a wholeblock memory), should it also depend of 
EXPERT ?

>   	select HAVE_ARCH_KASAN_VMALLOC		if PPC32
> +	select HAVE_ARCH_KASAN_VMALLOC		if PPC_BOOK3S_64 && PPC_RADIX_MMU

Maybe we could have

-  	select HAVE_ARCH_KASAN_VMALLOC		if PPC32
+	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


Christophe

Re: [PATCH v7 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support

[Michael Neuling]

Daniel. 

Can you start this commit message with a simple description of what you are
actually doing? This reads like you've been on a long journey to Mordor and
back, which as a reader of this patch in the long distant future, I don't care
about. I just want to know what you're implementing.

Also I'm struggling to review this as I don't know what software or hardware
mechanisms you are using to perform sanitisation.

Mikey

On Thu, 2020-02-13 at 11:47 +1100, Daniel Axtens wrote:
> 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 in real mode after booting. Most notably a lot of KVM
>    runs in real mode, and it would be good to be able to instrument it.
> 
>  - Because code runs in real mode after boot, the offset has to point to
>    valid memory both in and out of real mode.
> 
>     [ppc64 mm note: The kernel installs a linear mapping at effective
>     address c000... onward. 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.]
> 
> One approach is just to give up on inline instrumentation. This way all
> checks can be delayed until after everything set is up correctly, and the
> address-to-shadow calculations can be overridden. However, the features and
> speed boost provided by inline instrumentation are worth trying to do
> better.
> 
> If _at compile time_ it is known how much contiguous physical memory a
> system has, the top 1/8th of the first block of physical memory can be set
> aside for the shadow. This is a big hammer and comes with 3 big
> consequences:
> 
>  - there's no nice way to handle physically discontiguous memory, so only
>    the first physical memory block can be used.
> 
>  - kernels will simply fail to boot on machines with less memory than
>    specified when compiling.
> 
>  - kernels running on machines with more memory than specified when
>    compiling will simply ignore the extra memory.
> 
> Implement and document KASAN this way. The current implementation is Radix
> only.
> 
> Despite the limitations, it can still find bugs,
> e.g. http://patchwork.ozlabs.org/patch/1103775/
> 
> At the moment, this physical memory limit must be set _even for outline
> mode_. This may be changed in a later series - a different implementation
> could be added for outline mode that dynamically allocates shadow at a
> fixed offset. For example, see https://patchwork.ozlabs.org/patch/795211/
> 
> Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Balbir Singh <bsingharora@gmail.com> # ppc64 out-of-line radix version
> Cc: Christophe Leroy <christophe.leroy@c-s.fr> # ppc32 version
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> 
> ---
> Changes since v6:
>  - rework kasan_late_init support, which also fixes book3e problem that
> snowpatch
>    picked up (I think)
>  - fix a checkpatch error that snowpatch picked up
>  - don't needlessly move the include in kasan.h
> 
> Changes since v5:
>  - rebase on powerpc/merge, with Christophe's latest changes integrating
>    kasan-vmalloc
>  - documentation tweaks based on latest 32-bit changes
> 
> Changes since v4:
>  - fix some ppc32 build issues
>  - support ptdump
>  - clean up the header file. It turns out we don't need or use
> KASAN_SHADOW_SIZE,
>    so just dump it, and make KASAN_SHADOW_END the thing that varies between 32
>    and 64 bit. As part of this, make sure KASAN_SHADOW_OFFSET is only
> configured for
>    32 bit - it is calculated in the Makefile for ppc64.
>  - various cleanups
> 
> Changes since v3:
>  - Address further feedback from Christophe.
>  - Drop changes to stack walking, it looks like the issue I observed is
>    related to that particular stack, not stack-walking generally.
> 
> Changes since v2:
> 
>  - Address feedback from Christophe around cleanups and docs.
>  - Address feedback from Balbir: at this point I don't have a good solution
>    for the issues you identify around the limitations of the inline
> implementation
>    but I think that it's worth trying to get the stack instrumentation
> support.
>    I'm happy to have an alternative and more flexible outline mode - I had
>    envisoned this would be called 'lightweight' mode as it imposes fewer
> restrictions.
>    I've linked to your implementation. I think it's best to add it in a
> follow-up series.
>  - Made the default PHYS_MEM_SIZE_FOR_KASAN value 1024MB. I think most people
> have
>    guests with at least that much memory in the Radix 64s case so it's a much
>    saner default - it means that if you just turn on KASAN without reading the
>    docs you're much more likely to have a bootable kernel, which you will
> never
>    have if the value is set to zero! I'm happy to bikeshed the value if we
> want.
> 
> Changes since v1:
>  - Landed kasan vmalloc support upstream
>  - Lots of feedback from Christophe.
> 
> Changes since the rfc:
> 
>  - Boots real and virtual hardware, kvm works.
> 
>  - disabled reporting when we're checking the stack for exception
>    frames. The behaviour isn't wrong, just incompatible with KASAN.
> 
>  - Documentation!
> 
>  - Dropped old module stuff in favour of KASAN_VMALLOC.
> 
> The bugs with ftrace and kuap were due to kernel bloat pushing
> prom_init calls to be done via the plt. Because we did not have
> a relocatable kernel, and they are done very early, this caused
> everything to explode. Compile with CONFIG_RELOCATABLE!
> ---
>  Documentation/dev-tools/kasan.rst            |   9 +-
>  Documentation/powerpc/kasan.txt              | 112 ++++++++++++++++++-
>  arch/powerpc/Kconfig                         |   2 +
>  arch/powerpc/Kconfig.debug                   |  23 +++-
>  arch/powerpc/Makefile                        |  11 ++
>  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   |   5 +
>  arch/powerpc/include/asm/kasan.h             |  11 +-
>  arch/powerpc/kernel/prom.c                   |  61 +++++++++-
>  arch/powerpc/mm/kasan/Makefile               |   1 +
>  arch/powerpc/mm/kasan/init_book3s_64.c       |  73 ++++++++++++
>  arch/powerpc/mm/ptdump/ptdump.c              |  10 +-
>  arch/powerpc/platforms/Kconfig.cputype       |   1 +
>  14 files changed, 320 insertions(+), 10 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 012ef3d91d1f..5722de91ccce 100644
> --- a/Documentation/dev-tools/kasan.rst
> +++ b/Documentation/dev-tools/kasan.rst
> @@ -22,8 +22,9 @@ global variables yet.
>  Tag-based KASAN is only supported in Clang and requires version 7.0.0 or
> later.
>  
>  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..bf645a5cd486 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 +10,113 @@ 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
> 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 in real mode after booting. Most notably a lot of KVM
> runs
> +   in real mode, and it would be good to be able to instrument it.
> +
> + - Because code runs in real mode after boot, the offset has to point to
> +   valid memory both in and out of real mode.
> +
> +One approach is just to give up on inline instrumentation. This way all
> checks
> +can be delayed until after everything set is up correctly, and the
> +address-to-shadow calculations can be overridden. However, the features and
> +speed boost provided by inline instrumentation are worth trying to do better.
> +
> +If _at compile time_ it is known how much contiguous physical memory a system
> +has, the top 1/8th of the first block of physical memory can be set aside for
> +the shadow. This is a big hammer and comes with 3 big consequences:
> +
> + - there's no nice way to handle physically discontiguous memory, so only the
> +   first physical memory block can be used.
> +
> + - kernels will simply fail to boot on machines with less memory than
> specified
> +   when compiling.
> +
> + - kernels running on machines with more memory than specified when compiling
> +   will simply ignore the extra memory.
> +
> +At the moment, this physical memory limit must be set _even for outline
> mode_.
> +This may be changed in a future version - a different implementation could be
> +added for outline mode that dynamically allocates shadow at a fixed offset.
> +For example, see https://patchwork.ozlabs.org/patch/795211/
> +
> +This value is configured in CONFIG_PHYS_MEM_SIZE_FOR_KASAN.
> +
> +Tips
> +----
> +
> + - Compile with CONFIG_RELOCATABLE.
> +
> +   In development, boot hangs were observed when building with ftrace and
> KUAP
> +   on. These ended up being due to kernel bloat pushing prom_init calls to be
> +   done via the PLT. Because the kernel was not relocatable, and the calls
> are
> +   done very early, this caused execution to jump off into somewhere
> +   invalid. Enabling relocation fixes this.
> +
> +NUMA/discontiguous physical memory
> +----------------------------------
> +
> +Currently the code cannot really deal with discontiguous physical memory.
> Only
> +physical memory that is contiguous from physical address zero can be used.
> The
> +size of that memory, not total memory, must be specified when configuring the
> +kernel.
> +
> +Discontiguous memory can occur on machines with memory spread across multiple
> +nodes. For example, on a Talos II with 64GB of RAM:
> +
> + - 32GB runs from 0x0 to 0x0000_0008_0000_0000,
> + - then there's a gap,
> + - then the final 32GB runs from 0x0000_2000_0000_0000 to
> 0x0000_2008_0000_0000
> +
> +This can create _significant_ issues:
> +
> + - If the machine is treated as having 64GB of _contiguous_ RAM, the
> +   instrumentation would assume that it ran from 0x0 to
> +   0x0000_0010_0000_0000. The last 1/8th - 0x0000_000e_0000_0000 to
> +   0x0000_0010_0000_0000 would be reserved as the shadow region. But when the
> +   kernel tried to access any of that, it would be trying to access pages
> that
> +   are not physically present.
> +
> + - If the shadow region size is based on the top address, then the shadow
> +   region would be 0x2008_0000_0000 / 8 = 0x0401_0000_0000 bytes = 4100 GB of
> +   memory, clearly more than the 64GB of RAM physically present.
> +
> +Therefore, the code currently is restricted to dealing with memory in the
> node
> +starting at 0x0. For this system, that's 32GB. If a contiguous physical
> memory
> +size greater than the size of the first contiguous region of memory is
> +specified, the system will be unable to boot or even print an error message.
> +
> +The layout of a system's memory can be observed in the messages that the
> Radix
> +MMU prints on boot. The Talos II discussed earlier has:
> +
> +radix-mmu: Mapped 0x0000000000000000-0x0000000040000000 with 1.00 GiB pages
> (exec)
> +radix-mmu: Mapped 0x0000000040000000-0x0000000800000000 with 1.00 GiB pages
> +radix-mmu: Mapped 0x0000200000000000-0x0000200800000000 with 1.00 GiB pages
> +
> +As discussed, this system would be configured for 32768 MB.
> +
> +Another system prints:
> +
> +radix-mmu: Mapped 0x0000000000000000-0x0000000040000000 with 1.00 GiB pages
> (exec)
> +radix-mmu: Mapped 0x0000000040000000-0x0000002000000000 with 1.00 GiB pages
> +radix-mmu: Mapped 0x0000200000000000-0x0000202000000000 with 1.00 GiB pages
> +
> +This machine has more memory: 0x0000_0040_0000_0000 total, but only
> +0x0000_0020_0000_0000 is physically contiguous from zero, so it would be
> +configured for 131072 MB of physically contiguous memory.
> +
> +This restriction currently also affects outline mode, but this could be
> +changed in future if an alternative outline implementation is added.
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 497b7d0b2d7e..f1c54c08a88e 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -169,7 +169,9 @@ 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
> +	select HAVE_ARCH_KASAN			if PPC_BOOK3S_64 &&
> PPC_RADIX_MMU
>  	select HAVE_ARCH_KASAN_VMALLOC		if PPC32
> +	select HAVE_ARCH_KASAN_VMALLOC		if PPC_BOOK3S_64 &&
> PPC_RADIX_MMU
>  	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 0b063830eea8..faed301a3b10 100644
> --- a/arch/powerpc/Kconfig.debug
> +++ b/arch/powerpc/Kconfig.debug
> @@ -394,7 +394,28 @@ config PPC_FAST_ENDIAN_SWITCH
>  	help
>  	  If you're unsure what this is, say N.
>  
> +config PHYS_MEM_SIZE_FOR_KASAN
> +	int "Contiguous physical memory size for KASAN (MB)" if KASAN &&
> PPC_BOOK3S_64
> +	default 1024
> +	help
> +
> +	  To get inline instrumentation support for KASAN on 64-bit Book3S
> +	  machines, you need to know how much contiguous physical memory your
> +	  system has. A shadow offset will be calculated based on this figure,
> +	  which will be compiled in to the kernel. KASAN will use this offset
> +	  to access its shadow region, which is used to verify memory accesses.
> +
> +	  If you attempt to boot on a system with less memory than you specify
> +	  here, your system will fail to boot very early in the process. If you
> +	  boot on a system with more memory than you specify, the extra memory
> +	  will wasted - it will be reserved and not used.
> +
> +	  For systems with discontiguous blocks of physical memory, specify the
> +	  size of the block starting at 0x0. You can determine this by looking
> +	  at the memory layout info printed to dmesg by the radix MMU code
> +	  early in boot. See Documentation/powerpc/kasan.txt.
> +
>  config KASAN_SHADOW_OFFSET
>  	hex
> -	depends on KASAN
> +	depends on KASAN && PPC32
>  	default 0xe0000000
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index f35730548e42..eb47dc768c0a 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -230,6 +230,17 @@ ifdef CONFIG_476FPE_ERR46
>  		-T $(srctree)/arch/powerpc/platforms/44x/ppc476_modules.lds
>  endif
>  
> +ifdef CONFIG_PPC_BOOK3S_64
> +# The KASAN shadow offset is such that linear map (0xc000...) is shadowed by
> +# the last 8th of linearly mapped physical memory. This way, if the code uses
> +# 0xc addresses throughout, accesses work both in in real mode (where the top
> +# bits are ignored) and outside of real mode.
> +#
> +# 0xc000000000000000 >> 3 = 0xa800000000000000 = 12105675798371893248
> +KASAN_SHADOW_OFFSET = $(shell echo 7 \* 1024 \* 1024 \*
> $(CONFIG_PHYS_MEM_SIZE_FOR_KASAN) / 8 + 12105675798371893248 | bc)
> +KBUILD_CFLAGS += -DKASAN_SHADOW_OFFSET=$(KASAN_SHADOW_OFFSET)UL
> +endif
> +
>  # No AltiVec or VSX instructions when building kernel
>  KBUILD_CFLAGS += $(call cc-option,-mno-altivec)
>  KBUILD_CFLAGS += $(call cc-option,-mno-vsx)
> diff --git a/arch/powerpc/include/asm/book3s/64/hash.h
> b/arch/powerpc/include/asm/book3s/64/hash.h
> index 2781ebf6add4..fce329b8452e 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 201a69e6a355..309fb925a96e 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -231,6 +231,13 @@ 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 d97db3ad9aae..4f826259de71 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.
>   */
> diff --git a/arch/powerpc/include/asm/kasan.h
> b/arch/powerpc/include/asm/kasan.h
> index fbff9ff9032e..b21d3ef88214 100644
> --- a/arch/powerpc/include/asm/kasan.h
> +++ b/arch/powerpc/include/asm/kasan.h
> @@ -21,11 +21,18 @@
>  #define KASAN_SHADOW_START	(KASAN_SHADOW_OFFSET + \
>  				 (PAGE_OFFSET >> 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	0UL
> +#endif
>  
> -#define KASAN_SHADOW_SIZE	(KASAN_SHADOW_END - KASAN_SHADOW_START)
> +#ifdef CONFIG_PPC_BOOK3S_64
> +#define KASAN_SHADOW_END	(KASAN_SHADOW_OFFSET + \
> +				 (RADIX_VMEMMAP_END >>
> KASAN_SHADOW_SCALE_SHIFT))
> +#endif
>  
>  #ifdef CONFIG_KASAN
>  void kasan_early_init(void);
> @@ -38,5 +45,5 @@ static inline void kasan_mmu_init(void) { }
>  static inline void kasan_late_init(void) { }
>  #endif
>  
> -#endif /* __ASSEMBLY */
> +#endif /* !__ASSEMBLY__ */
>  #endif
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 6620f37abe73..2857c3d44e9c 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -72,6 +72,7 @@ unsigned long tce_alloc_start, tce_alloc_end;
>  u64 ppc64_rma_size;
>  #endif
>  static phys_addr_t first_memblock_size;
> +static phys_addr_t top_phys_addr;
>  static int __initdata boot_cpu_count;
>  
>  static int __init early_parse_mem(char *p)
> @@ -449,6 +450,26 @@ static bool validate_mem_limit(u64 base, u64 *size)
>  {
>  	u64 max_mem = 1UL << (MAX_PHYSMEM_BITS);
>  
> +	/*
> +	 * To handle the NUMA/discontiguous memory case, don't allow a block
> +	 * to be added if it falls completely beyond the configured physical
> +	 * memory. Print an informational message.
> +	 *
> +	 * Frustratingly we also see this with qemu - it seems to split the
> +	 * specified memory into a number of smaller blocks. If this happens
> +	 * under qemu, it probably represents misconfiguration. So we want
> +	 * the message to be noticeable, but not shouty.
> +	 *
> +	 * See Documentation/powerpc/kasan.txt
> +	 */
> +	if (IS_ENABLED(CONFIG_KASAN) &&
> +	    (base >= ((u64)CONFIG_PHYS_MEM_SIZE_FOR_KASAN * SZ_1M))) {
> +		pr_warn("KASAN: not adding memory block at %llx (size %llx)\n"
> +			"This could be due to discontiguous memory or kernel
> misconfiguration.",
> +			base, *size);
> +		return false;
> +	}
> +
>  	if (base >= max_mem)
>  		return false;
>  	if ((base + *size) > max_mem)
> @@ -572,8 +593,10 @@ void __init early_init_dt_add_memory_arch(u64 base, u64
> size)
>  
>  	/* Add the chunk to the MEMBLOCK list */
>  	if (add_mem_to_memblock) {
> -		if (validate_mem_limit(base, &size))
> +		if (validate_mem_limit(base, &size)) {
>  			memblock_add(base, size);
> +			top_phys_addr = max(top_phys_addr, (phys_addr_t)(base +
> size));
> +		}
>  	}
>  }
>  
> @@ -613,6 +636,8 @@ static void __init early_reserve_mem_dt(void)
>  static void __init early_reserve_mem(void)
>  {
>  	__be64 *reserve_map;
> +	phys_addr_t kasan_shadow_start;
> +	phys_addr_t kasan_memory_size;
>  
>  	reserve_map = (__be64 *)(((unsigned long)initial_boot_params) +
>  			fdt_off_mem_rsvmap(initial_boot_params));
> @@ -651,6 +676,40 @@ static void __init early_reserve_mem(void)
>  		return;
>  	}
>  #endif
> +
> +	if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_PPC_BOOK3S_64)) {
> +		kasan_memory_size =
> +			((phys_addr_t)CONFIG_PHYS_MEM_SIZE_FOR_KASAN * SZ_1M);
> +
> +		if (top_phys_addr < kasan_memory_size) {
> +			/*
> +			 * We are doomed. We shouldn't even be able to get this
> +			 * far, but we do in qemu. If we continue and turn
> +			 * relocations on, we'll take fatal page faults for
> +			 * memory that's not physically present. Instead,
> +			 * panic() here: it will be saved to __log_buf even if
> +			 * it doesn't get printed to the console.
> +			 */
> +			panic("Tried to boot a KASAN kernel configured for %u MB
> with only %llu MB! Aborting.",
> +			      CONFIG_PHYS_MEM_SIZE_FOR_KASAN,
> +			      (u64)(top_phys_addr * SZ_1M));
> +		} else if (top_phys_addr > kasan_memory_size) {
> +			/* print a biiiig warning in hopes people notice */
> +			pr_err("===========================================\n"
> +				"Physical memory exceeds compiled-in maximum!\n"
> +				"This kernel was compiled for KASAN with %u MB
> physical memory.\n"
> +				"The physical memory detected is at least %llu
> MB.\n"
> +				"Memory above the compiled limit will not be
> used!\n"
> +				"===========================================\n",
> +				CONFIG_PHYS_MEM_SIZE_FOR_KASAN,
> +				(u64)(top_phys_addr * SZ_1M));
> +		}
> +
> +		kasan_shadow_start = _ALIGN_DOWN(kasan_memory_size * 7 / 8,
> PAGE_SIZE);
> +		DBG("reserving %llx -> %llx for KASAN",
> +		    kasan_shadow_start, top_phys_addr);
> +		memblock_reserve(kasan_shadow_start, top_phys_addr -
> kasan_shadow_start);
> +	}
>  }
>  
>  #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> diff --git a/arch/powerpc/mm/kasan/Makefile b/arch/powerpc/mm/kasan/Makefile
> index 36a4e1b10b2d..f02b15c78e4d 100644
> --- a/arch/powerpc/mm/kasan/Makefile
> +++ b/arch/powerpc/mm/kasan/Makefile
> @@ -3,3 +3,4 @@
>  KASAN_SANITIZE := n
>  
>  obj-$(CONFIG_PPC32)           += init_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..1c95fe6495c7
> --- /dev/null
> +++ b/arch/powerpc/mm/kasan/init_book3s_64.c
> @@ -0,0 +1,73 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * KASAN for 64-bit Book3S powerpc
> + *
> + * Copyright (C) 2019 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 <asm/pgalloc.h>
> +
> +void __init kasan_init(void)
> +{
> +	int i;
> +	void *k_start = kasan_mem_to_shadow((void *)RADIX_KERN_VIRT_START);
> +	void *k_end = kasan_mem_to_shadow((void *)RADIX_VMEMMAP_END);
> +
> +	pte_t pte =  pte_mkpte(pfn_pte(virt_to_pfn(kasan_early_shadow_page),
> +				       PAGE_KERNEL));
> +
> +	if (!early_radix_enabled())
> +		panic("KASAN requires radix!");
> +
> +	for (i = 0; i < PTRS_PER_PTE; i++)
> +		__set_pte_at(&init_mm, (unsigned long)kasan_early_shadow_page,
> +			     &kasan_early_shadow_pte[i], 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);
> +
> +	memset((void *)KASAN_SHADOW_START, KASAN_SHADOW_INIT,
> +	       ((u64)CONFIG_PHYS_MEM_SIZE_FOR_KASAN *
> +		     SZ_1M >> KASAN_SHADOW_SCALE_SHIFT));
> +
> +	kasan_populate_early_shadow(kasan_mem_to_shadow((void
> *)RADIX_KERN_VIRT_START),
> +				    kasan_mem_to_shadow((void
> *)RADIX_VMALLOC_START));
> +
> +	/* leave a hole here for vmalloc */
> +
> +	kasan_populate_early_shadow(
> +		kasan_mem_to_shadow((void *)RADIX_VMALLOC_END),
> +		kasan_mem_to_shadow((void *)RADIX_VMEMMAP_END));
> +
> +	flush_tlb_kernel_range((unsigned long)k_start, (unsigned long)k_end);
> +
> +	/* mark early shadow region as RO and wipe */
> +	pte = pte_mkpte(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], 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);
> +
> +	/* Enable error messages */
> +	init_task.kasan_depth = 0;
> +	pr_info("KASAN init done (64-bit Book3S heavyweight mode)\n");
> +}
> +
> +void __init kasan_late_init(void) { }
> diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> index 206156255247..b982dc5441c0 100644
> --- a/arch/powerpc/mm/ptdump/ptdump.c
> +++ b/arch/powerpc/mm/ptdump/ptdump.c
> @@ -73,6 +73,10 @@ struct addr_marker {
>  
>  static struct addr_marker address_markers[] = {
>  	{ 0,	"Start of kernel VM" },
> +#if defined(CONFIG_PPC64) && defined(CONFIG_KASAN)
> +	{ 0,	"kasan shadow mem start" },
> +	{ 0,	"kasan shadow mem end" },
> +#endif
>  	{ 0,	"vmalloc() Area" },
>  	{ 0,	"vmalloc() End" },
>  #ifdef CONFIG_PPC64
> @@ -92,10 +96,10 @@ static struct addr_marker address_markers[] = {
>  #endif
>  	{ 0,	"Fixmap start" },
>  	{ 0,	"Fixmap end" },
> -#endif
>  #ifdef CONFIG_KASAN
>  	{ 0,	"kasan shadow mem start" },
>  	{ 0,	"kasan shadow mem end" },
> +#endif
>  #endif
>  	{ -1,	NULL },
>  };
> @@ -317,6 +321,10 @@ static void populate_markers(void)
>  	int i = 0;
>  
>  	address_markers[i++].start_address = PAGE_OFFSET;
> +#if defined(CONFIG_PPC64) && defined(CONFIG_KASAN)
> +	address_markers[i++].start_address = KASAN_SHADOW_START;
> +	address_markers[i++].start_address = KASAN_SHADOW_END;
> +#endif
>  	address_markers[i++].start_address = VMALLOC_START;
>  	address_markers[i++].start_address = VMALLOC_END;
>  #ifdef CONFIG_PPC64
> diff --git a/arch/powerpc/platforms/Kconfig.cputype
> b/arch/powerpc/platforms/Kconfig.cputype
> index 6caedc88474f..cedc86686e65 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -99,6 +99,7 @@ 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"

Re: [PATCH v7 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support

[Christophe Leroy]

Le 17/02/2020 à 00:08, Michael Neuling a écrit :
> Daniel.
> 
> Can you start this commit message with a simple description of what you are
> actually doing? This reads like you've been on a long journey to Mordor and
> back, which as a reader of this patch in the long distant future, I don't care
> about. I just want to know what you're implementing.
> 
> Also I'm struggling to review this as I don't know what software or hardware
> mechanisms you are using to perform sanitisation.

KASAN is standard, it's simply using GCC ASAN in kernel mode, ie kernel 
is built with -fsanitize=kernel-address 
(https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html)

You have more details there: 
https://www.kernel.org/doc/html/latest/dev-tools/kasan.html

Christophe

Re: [PATCH v7 4/4] powerpc: Book3S 64-bit "heavyweight" KASAN support

[Daniel Axtens]

Christophe Leroy <christophe.leroy@c-s.fr> writes:

> Le 13/02/2020 à 01:47, Daniel Axtens a écrit :
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index 497b7d0b2d7e..f1c54c08a88e 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -169,7 +169,9 @@ 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
>> +	select HAVE_ARCH_KASAN			if PPC_BOOK3S_64 && PPC_RADIX_MMU
>
> That's probably detail, but as it is necessary to deeply define the HW 
> when selecting that (I mean giving the exact amount of memory and with 
> restrictions like having a wholeblock memory), should it also depend of 
> EXPERT ?

If it weren't a debug feature I would definitely agree with you, but I
think being a debug feature it's not so necessary. Also anything with
more memory than the config option specifies will still boot - it's just
less memory that won't boot. I've set the default to 1024MB: I know
that's a lot of memory for an embedded system but I think for anything
with the Radix MMU it's an OK default.

I'm sure if mpe disagrees he can add EXPERT when he's merging :)

> Maybe we could have
>
> -  	select HAVE_ARCH_KASAN_VMALLOC		if PPC32
> +	select HAVE_ARCH_KASAN_VMALLOC		if HAVE_ARCH_KASAN

That's a good idea. Done.

Thanks for the review!

Regards,
Daniel

>
>>   	select HAVE_ARCH_KGDB
>>   	select HAVE_ARCH_MMAP_RND_BITS
>>   	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT
>
>
> Christophe