lwn.git/arch/powerpc/mm/kasan, branch master

kasan: introduce ARCH_DEFER_KASAN and unify static key across modes

2025-09-21T21:21:58+00:00

Patch series "kasan: unify kasan_enabled() and remove arch-specific implementations", v6. This patch series addresses the fragmentation in KASAN initialization across architectures by introducing a unified approach that eliminates duplicate static keys and arch-specific kasan_arch_is_ready() implementations. The core issue is that different architectures have inconsistent approaches to KASAN readiness tracking: - PowerPC, LoongArch, and UML arch, each implement own kasan_arch_is_ready() - Only HW_TAGS mode had a unified static key (kasan_flag_enabled) - Generic and SW_TAGS modes relied on arch-specific solutions or always-on behavior This patch (of 2): Introduce CONFIG_ARCH_DEFER_KASAN to identify architectures [1] that need to defer KASAN initialization until shadow memory is properly set up, and unify the static key infrastructure across all KASAN modes. [1] PowerPC, UML, LoongArch selects ARCH_DEFER_KASAN. The core issue is that different architectures haveinconsistent approaches to KASAN readiness tracking: - PowerPC, LoongArch, and UML arch, each implement own kasan_arch_is_ready() - Only HW_TAGS mode had a unified static key (kasan_flag_enabled) - Generic and SW_TAGS modes relied on arch-specific solutions or always-on behavior This patch addresses the fragmentation in KASAN initialization across architectures by introducing a unified approach that eliminates duplicate static keys and arch-specific kasan_arch_is_ready() implementations. Let's replace kasan_arch_is_ready() with existing kasan_enabled() check, which examines the static key being enabled if arch selects ARCH_DEFER_KASAN or has HW_TAGS mode support. For other arch, kasan_enabled() checks the enablement during compile time. Now KASAN users can use a single kasan_enabled() check everywhere. Link: https://lkml.kernel.org/r/20250810125746.1105476-1-snovitoll@gmail.com Link: https://lkml.kernel.org/r/20250810125746.1105476-2-snovitoll@gmail.com Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217049 Signed-off-by: Sabyrzhan Tasbolatov Reviewed-by: Christophe Leroy Reviewed-by: Ritesh Harjani (IBM) #powerpc Cc: Alexander Gordeev Cc: Alexander Potapenko Cc: Alexandre Ghiti Cc: Alexandre Ghiti Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Baoquan He Cc: David Gow Cc: Dmitriy Vyukov Cc: Heiko Carstens Cc: Huacai Chen Cc: Marco Elver Cc: Qing Zhang Cc: Sabyrzhan Tasbolatov Cc: Vincenzo Frascino Signed-off-by: Andrew Morton

mm/memblock: add memblock_alloc_or_panic interface

2025-01-26T04:22:38+00:00

Before SLUB initialization, various subsystems used memblock_alloc to allocate memory. In most cases, when memory allocation fails, an immediate panic is required. To simplify this behavior and reduce repetitive checks, introduce `memblock_alloc_or_panic`. This function ensures that memory allocation failures result in a panic automatically, improving code readability and consistency across subsystems that require this behavior. [guoweikang.kernel@gmail.com: arch/s390: save_area_alloc default failure behavior changed to panic] Link: https://lkml.kernel.org/r/20250109033136.2845676-1-guoweikang.kernel@gmail.com Link: https://lore.kernel.org/lkml/Z2fknmnNtiZbCc7x@kernel.org/ Link: https://lkml.kernel.org/r/20250102072528.650926-1-guoweikang.kernel@gmail.com Signed-off-by: Guo Weikang Acked-by: Geert Uytterhoeven [m68k] Reviewed-by: Alexander Gordeev [s390] Acked-by: Mike Rapoport (Microsoft) Cc: Alexander Gordeev Signed-off-by: Andrew Morton

asm-generic: introduce text-patching.h

2024-11-07T22:25:15+00:00

Several architectures support text patching, but they name the header files that declare patching functions differently. Make all such headers consistently named text-patching.h and add an empty header in asm-generic for architectures that do not support text patching. Link: https://lkml.kernel.org/r/20241023162711.2579610-4-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Christoph Hellwig Acked-by: Geert Uytterhoeven # m68k Acked-by: Arnd Bergmann Reviewed-by: Luis Chamberlain Tested-by: kdevops Cc: Andreas Larsson Cc: Andy Lutomirski Cc: Ard Biesheuvel Cc: Borislav Petkov (AMD) Cc: Brian Cain Cc: Catalin Marinas Cc: Christophe Leroy Cc: Dave Hansen Cc: Dinh Nguyen Cc: Guo Ren Cc: Helge Deller Cc: Huacai Chen Cc: Ingo Molnar Cc: Johannes Berg Cc: John Paul Adrian Glaubitz Cc: Kent Overstreet Cc: Liam R. Howlett Cc: Mark Rutland Cc: Masami Hiramatsu (Google) Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Michal Simek Cc: Oleg Nesterov Cc: Palmer Dabbelt Cc: Peter Zijlstra Cc: Richard Weinberger Cc: Russell King Cc: Song Liu Cc: Stafford Horne Cc: Steven Rostedt (Google) Cc: Suren Baghdasaryan Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Uladzislau Rezki (Sony) Cc: Vineet Gupta Cc: Will Deacon Signed-off-by: Andrew Morton

powerpc/8xx: rework support for 8M pages using contiguous PTE entries

2024-07-12T22:52:17+00:00

In order to fit better with standard Linux page tables layout, add support for 8M pages using contiguous PTE entries in a standard page table. Page tables will then be populated with 1024 similar entries and two PMD entries will point to that page table. The PMD entries also get a flag to tell it is addressing an 8M page, this is required for the HW tablewalk assistance. Link: https://lkml.kernel.org/r/8693d9a0408371043ca63bf9e4a9c140667af63e.1719928057.git.christophe.leroy@csgroup.eu Signed-off-by: Christophe Leroy Reviewed-by: Oscar Salvador Cc: Jason Gunthorpe Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Peter Xu Signed-off-by: Andrew Morton

powerpc64/kasan: Pass virtual addresses to kasan_init_phys_region()

2024-05-07T14:28:16+00:00

The kasan_init_phys_region() function maps shadow pages necessary for the ranges of the linear map backed by physical pages. Currently kasan_init_phys_region() is being passed physical addresses, but kasan_mem_to_shadow() expects virtual addresses. It works right now because the lower bits (12:64) of the kasan_mem_to_shadow() calculation are the same for the real and virtual addresses, so the actual PTE value is the same in the end. But virtual addresses are the intended input, so fix it. Signed-off-by: Benjamin Gray Signed-off-by: Michael Ellerman Link: https://msgid.link/20240212045020.70364-1-bgray@linux.ibm.com

powerpc/kasan: Fix addr error caused by page alignment

2024-02-05T11:57:26+00:00

In kasan_init_region, when k_start is not page aligned, at the begin of for loop, k_cur = k_start & PAGE_MASK is less than k_start, and then `va = block + k_cur - k_start` is less than block, the addr va is invalid, because the memory address space from va to block is not alloced by memblock_alloc, which will not be reserved by memblock_reserve later, it will be used by other places. As a result, memory overwriting occurs. for example: int __init __weak kasan_init_region(void *start, size_t size) { [...] /* if say block(dcd97000) k_start(feef7400) k_end(feeff3fe) */ block = memblock_alloc(k_end - k_start, PAGE_SIZE); [...] for (k_cur = k_start & PAGE_MASK; k_cur < k_end; k_cur += PAGE_SIZE) { /* at the begin of for loop * block(dcd97000) va(dcd96c00) k_cur(feef7000) k_start(feef7400) * va(dcd96c00) is less than block(dcd97000), va is invalid */ void *va = block + k_cur - k_start; [...] } [...] } Therefore, page alignment is performed on k_start before memblock_alloc() to ensure the validity of the VA address. Fixes: 663c0c9496a6 ("powerpc/kasan: Fix shadow area set up for modules.") Signed-off-by: Jiangfeng Xiao Signed-off-by: Michael Ellerman Link: https://msgid.link/1705974359-43790-1-git-send-email-xiaojiangfeng@huawei.com

powerpc/kasan: Disable KCOV in KASAN code

2023-07-17T12:49:44+00:00

As per the generic KASAN code in mm/kasan, disable KCOV with KCOV_INSTRUMENT := n in the makefile. This fixes a ppc64 boot hang when KCOV and KASAN are enabled. kasan_early_init() gets called before a PACA is initialised, but the KCOV hook expects a valid PACA. Suggested-by: Christophe Leroy Signed-off-by: Benjamin Gray Signed-off-by: Michael Ellerman Link: https://msgid.link/20230710044143.146840-1-bgray@linux.ibm.com

powerpc/32s: Fix boot failure with KASAN + SMP + JUMP_LABEL_FEATURE_CHECK_DEBUG

2022-07-27T11:36:05+00:00

Since commit 4291d085b0b0 ("powerpc/32s: Make pte_update() non atomic on 603 core"), pte_update() has been using mmu_has_feature(MMU_FTR_HPTE_TABLE) to avoid a useless atomic operation on 603 cores. When kasan_early_init() sets up the early zero shadow, it uses __set_pte_at(). On book3s/32, __set_pte_at() calls pte_update() when CONFIG_SMP is selected in order to ensure the preservation of _PAGE_HASHPTE in case of concurrent update of the PTE. But that's too early for mmu_has_feature(), so when CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG is selected, mmu_has_feature() calls printk(). That's too early to call printk() because KASAN early zero shadow page is not set up yet. It leads to a deadlock. However, when kasan_early_init() is called, there is only one CPU running and no risk of concurrent PTE update. So __set_pte_at() can be called with the 'percpu' flag. With that flag set, the PTE is written directly instead of being written via pte_update(). Fixes: 4291d085b0b0 ("powerpc/32s: Make pte_update() non atomic on 603 core") Reported-by: Erhard Furtner Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/2ee707512b8b212b079b877f4ceb525a1606a3fb.1656655567.git.christophe.leroy@csgroup.eu

powerpc/64e: KASAN Full support for BOOK3E/64

2022-06-29T07:04:15+00:00

We now have memory organised in a way that allows implementing KASAN. Unlike book3s/64, book3e always has translation active so the only thing needed to use KASAN is to setup an early zero shadow mapping just after setting a stack pointer and before calling early_setup(). The memory layout is now as follows +------------------------+ Kernel virtual map end (0xc000200000000000) | | | 16TB of KASAN map | | | +------------------------+ Kernel KASAN shadow map start | | | 16TB of IO map | | | +------------------------+ Kernel IO map start | | | 16TB of vmemmap | | | +------------------------+ Kernel vmemmap start | | | 16TB of vmap | | | +------------------------+ Kernel virt start (0xc000100000000000) | | | 64TB of linear mem | | | +------------------------+ Kernel linear (0xc.....) Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/0bef8beda27baf71e3b9e8b13e620fba6e19499b.1656427701.git.christophe.leroy@csgroup.eu

powerpc: Book3S 64-bit outline-only KASAN support

2022-05-22T05:58:29+00:00

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. - Document KASAN in 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. [paulus@ozlabs.org - Rebased onto 5.17. Note that a kernel with CONFIG_KASAN=y will crash during boot on a machine using HPT translation because not all the entry points to the generic KASAN code are protected with a call to kasan_arch_is_ready().] Originally-by: Balbir Singh # ppc64 out-of-line radix version Signed-off-by: Daniel Axtens Signed-off-by: Paul Mackerras [mpe: Update copyright year and comment formatting] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/YoTE69OQwiG7z+Gu@cleo