kernel/linux.git/arch/arm64/include/asm/mte.h, branch linux-7.0.y

arm64: Replace ASSEMBLY with ASSEMBLER in non-uapi headers

2025-11-11T19:35:59+00:00

While the GCC and Clang compilers already define __ASSEMBLER__ automatically when compiling assembly code, __ASSEMBLY__ is a macro that only gets defined by the Makefiles in the kernel. This can be very confusing when switching between userspace and kernelspace coding, or when dealing with uapi headers that rather should use __ASSEMBLER__ instead. So let's standardize now on the __ASSEMBLER__ macro that is provided by the compilers. This is a mostly mechanical patch (done with a simple "sed -i" statement), except for the following files where comments with mis-spelled macros were tweaked manually: arch/arm64/include/asm/stacktrace/frame.h arch/arm64/include/asm/kvm_ptrauth.h arch/arm64/include/asm/debug-monitors.h arch/arm64/include/asm/esr.h arch/arm64/include/asm/scs.h arch/arm64/include/asm/memory.h Signed-off-by: Thomas Huth Signed-off-by: Catalin Marinas

mm: introduce memdesc_flags_t

2025-09-13T23:55:07+00:00

Patch series "Add and use memdesc_flags_t". At some point struct page will be separated from struct slab and struct folio. This is a step towards that by introducing a type for the 'flags' word of all three structures. This gives us a certain amount of type safety by establishing that some of these unsigned longs are different from other unsigned longs in that they contain things like node ID, section number and zone number in the upper bits. That lets us have functions that can be easily called by anyone who has a slab, folio or page (but not easily by anyone else) to get the node or zone. There's going to be some unusual merge problems with this as some odd bits of the kernel decide they want to print out the flags value or something similar by writing page->flags and now they'll need to write page->flags.f instead. That's most of the churn here. Maybe we should be removing these things from the debug output? This patch (of 11): Wrap the unsigned long flags in a typedef. In upcoming patches, this will provide a strong hint that you can't just pass a random unsigned long to functions which take this as an argument. [willy@infradead.org: s/flags/flags.f/ in several architectures] Link: https://lkml.kernel.org/r/aKMgPRLD-WnkPxYm@casper.infradead.org [nicola.vetrini@gmail.com: mips: fix compilation error] Link: https://lore.kernel.org/lkml/CA+G9fYvkpmqGr6wjBNHY=dRp71PLCoi2341JxOudi60yqaeUdg@mail.gmail.com/ Link: https://lkml.kernel.org/r/20250825214245.1838158-1-nicola.vetrini@gmail.com Link: https://lkml.kernel.org/r/20250805172307.1302730-1-willy@infradead.org Link: https://lkml.kernel.org/r/20250805172307.1302730-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Zi Yan Cc: Shakeel Butt Signed-off-by: Andrew Morton

hugetlb: arm64: add mte support

2024-10-16T13:50:47+00:00

Enable MTE support for hugetlb. The MTE page flags will be set on the folio only. When copying hugetlb folio (for example, CoW), the tags for all subpages will be copied when copying the first subpage. When freeing hugetlb folio, the MTE flags will be cleared. Reviewed-by: Catalin Marinas Reviewed-by: David Hildenbrand Signed-off-by: Yang Shi Link: https://lore.kernel.org/r/20241001225220.271178-1-yang@os.amperecomputing.com Signed-off-by: Catalin Marinas

arm64: mte: Make mte_check_tfsr_*() conditional on KASAN instead of MTE

2024-06-12T15:01:57+00:00

The check in mte_check_tfsr_el1() is only necessary if HW tag based KASAN is enabled. However, we were also executing the check if MTE is enabled and KASAN is enabled at build time but disabled at runtime. This turned out to cause a measurable increase in power consumption on a specific microarchitecture after enabling MTE. Moreover, on the same system, an increase in invalid syscall latency (as measured by [1]) of around 20-30% (depending on the cluster) was observed after enabling MTE; this almost entirely goes away after removing this check. Therefore, make the check conditional on whether KASAN is enabled rather than on whether MTE is enabled. [1] https://lore.kernel.org/all/CAMn1gO4MwRV8bmFJ_SeY5tsYNPn2ZP56LjAhafygjFaKuu5ouw@mail.gmail.com/ Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/I22d98d1483dd400a95595946552b769a5a1ad7bd Reviewed-by: Alexandru Elisei Link: https://lore.kernel.org/r/20240528225131.3577704-1-pcc@google.com Signed-off-by: Catalin Marinas

arm64/mm: Hoist synchronization out of set_ptes() loop

2023-10-16T17:27:31+00:00

set_ptes() sets a physically contiguous block of memory (which all belongs to the same folio) to a contiguous block of ptes. The arm64 implementation of this previously just looped, operating on each individual pte. But the __sync_icache_dcache() and mte_sync_tags() operations can both be hoisted out of the loop so that they are performed once for the contiguous set of pages (which may be less than the whole folio). This should result in minor performance gains. __sync_icache_dcache() already acts on the whole folio, and sets a flag in the folio so that it skips duplicate calls. But by hoisting the call, all the pte testing is done only once. mte_sync_tags() operates on each individual page with its own loop. But by passing the number of pages explicitly, we can rely solely on its loop and do the checks only once. This approach also makes it robust for the future, rather than assuming if a head page of a compound page is being mapped, then the whole compound page is being mapped, instead we explicitly know how many pages are being mapped. The old assumption may not continue to hold once the "anonymous large folios" feature is merged. Signed-off-by: Ryan Roberts Reviewed-by: Steven Price Link: https://lore.kernel.org/r/20231005140730.2191134-1-ryan.roberts@arm.com Signed-off-by: Catalin Marinas

arm64: mte: simplify swap tag restoration logic

2023-08-18T17:12:02+00:00

As a result of the patches "mm: Call arch_swap_restore() from do_swap_page()" and "mm: Call arch_swap_restore() from unuse_pte()", there are no circumstances in which a swapped-in page is installed in a page table without first having arch_swap_restore() called on it. Therefore, we no longer need the logic in set_pte_at() that restores the tags, so remove it. Link: https://lkml.kernel.org/r/20230523004312.1807357-4-pcc@google.com Link: https://linux-review.googlesource.com/id/I8ad54476f3b2d0144ccd8ce0c1d7a2963e5ff6f3 Signed-off-by: Peter Collingbourne Reviewed-by: Steven Price Reviewed-by: Catalin Marinas Cc: Alexandru Elisei Cc: Chinwen Chang Cc: David Hildenbrand Cc: Evgenii Stepanov Cc: Greg Kroah-Hartman Cc: kasan-dev@googlegroups.com Cc: kasan-dev Cc: "Kuan-Ying Lee (李冠穎)" Cc: Qun-Wei Lin Cc: Suren Baghdasaryan Cc: Vincenzo Frascino Cc: Will Deacon Cc: "Huang, Ying" Signed-off-by: Andrew Morton

arm64: mte: rename TCO routines

2023-04-06T02:42:43+00:00

The TCO related routines are used in uaccess methods and load_unaligned_zeropad() but are unrelated to both even if the naming suggest otherwise. Improve the readability of the code moving the away from uaccess.h and pre-pending them with "mte". [andreyknvl@google.com: drop __ from mte_disable/enable_tco names] Link: https://lkml.kernel.org/r/74d26337b2360733956114069e96ff11c296a944.1680114854.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/a48e7adce1248c0f9603a457776d59daa0ef734b.1678491668.git.andreyknvl@google.com Signed-off-by: Vincenzo Frascino Signed-off-by: Catalin Marinas Signed-off-by: Andrey Konovalov Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Marco Elver Cc: Peter Collingbourne Cc: Weizhao Ouyang Cc: Will Deacon Signed-off-by: Andrew Morton

arm64: mte: Lock a page for MTE tag initialisation

2022-11-29T09:26:07+00:00

Initialising the tags and setting PG_mte_tagged flag for a page can race between multiple set_pte_at() on shared pages or setting the stage 2 pte via user_mem_abort(). Introduce a new PG_mte_lock flag as PG_arch_3 and set it before attempting page initialisation. Given that PG_mte_tagged is never cleared for a page, consider setting this flag to mean page unlocked and wait on this bit with acquire semantics if the page is locked: - try_page_mte_tagging() - lock the page for tagging, return true if it can be tagged, false if already tagged. No acquire semantics if it returns true (PG_mte_tagged not set) as there is no serialisation with a previous set_page_mte_tagged(). - set_page_mte_tagged() - set PG_mte_tagged with release semantics. The two-bit locking is based on Peter Collingbourne's idea. Signed-off-by: Catalin Marinas Signed-off-by: Peter Collingbourne Reviewed-by: Steven Price Cc: Will Deacon Cc: Marc Zyngier Cc: Peter Collingbourne Reviewed-by: Cornelia Huck Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20221104011041.290951-6-pcc@google.com

arm64: mte: Fix/clarify the PG_mte_tagged semantics

2022-11-29T09:26:07+00:00

Currently the PG_mte_tagged page flag mostly means the page contains valid tags and it should be set after the tags have been cleared or restored. However, in mte_sync_tags() it is set before setting the tags to avoid, in theory, a race with concurrent mprotect(PROT_MTE) for shared pages. However, a concurrent mprotect(PROT_MTE) with a copy on write in another thread can cause the new page to have stale tags. Similarly, tag reading via ptrace() can read stale tags if the PG_mte_tagged flag is set before actually clearing/restoring the tags. Fix the PG_mte_tagged semantics so that it is only set after the tags have been cleared or restored. This is safe for swap restoring into a MAP_SHARED or CoW page since the core code takes the page lock. Add two functions to test and set the PG_mte_tagged flag with acquire and release semantics. The downside is that concurrent mprotect(PROT_MTE) on a MAP_SHARED page may cause tag loss. This is already the case for KVM guests if a VMM changes the page protection while the guest triggers a user_mem_abort(). Signed-off-by: Catalin Marinas [pcc@google.com: fix build with CONFIG_ARM64_MTE disabled] Signed-off-by: Peter Collingbourne Reviewed-by: Cornelia Huck Reviewed-by: Steven Price Cc: Will Deacon Cc: Marc Zyngier Cc: Peter Collingbourne Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20221104011041.290951-3-pcc@google.com

arm64: mte: move register initialization to C

2022-09-22T17:02:50+00:00

If FEAT_MTE2 is disabled via the arm64.nomte command line argument on a CPU that claims to support FEAT_MTE2, the kernel will use Tagged Normal in the MAIR. If we interpret arm64.nomte to mean that the CPU does not in fact implement FEAT_MTE2, setting the system register like this may lead to UNSPECIFIED behavior. Fix it by arranging for MAIR to be set in the C function cpu_enable_mte which is called based on the sanitized version of the system register. There is no need for the rest of the MTE-related system register initialization to happen from assembly, with the exception of TCR_EL1, which must be set to include at least TBI1 because the secondary CPUs access KASan-allocated data structures early. Therefore, make the TCR_EL1 initialization unconditional and move the rest of the initialization to cpu_enable_mte so that we no longer have a dependency on the unsanitized ID register value. Co-developed-by: Evgenii Stepanov Signed-off-by: Peter Collingbourne Signed-off-by: Evgenii Stepanov Suggested-by: Catalin Marinas Reported-by: kernel test robot Fixes: 3b714d24ef17 ("arm64: mte: CPU feature detection and initial sysreg configuration") Cc: # 5.10.x Link: https://lore.kernel.org/r/20220915222053.3484231-1-eugenis@google.com Signed-off-by: Catalin Marinas

kernel/linux.git/arch/arm64/include/asm/mte.h, branch linux-7.0.y

arm64: Replace __ASSEMBLY__ with __ASSEMBLER__ in non-uapi headers

mm: introduce memdesc_flags_t

hugetlb: arm64: add mte support

arm64: mte: Make mte_check_tfsr_*() conditional on KASAN instead of MTE

arm64/mm: Hoist synchronization out of set_ptes() loop

arm64: mte: simplify swap tag restoration logic

arm64: mte: rename TCO routines

arm64: mte: Lock a page for MTE tag initialisation

arm64: mte: Fix/clarify the PG_mte_tagged semantics

arm64: mte: move register initialization to C

arm64: Replace ASSEMBLY with ASSEMBLER in non-uapi headers