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

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