Linear Address Masking[1] (LAM) modifies the checking that is applied to 64-bit linear addresses, allowing software to use of the untranslated address bits for metadata. The patchset brings support for LAM for userspace addresses. The most sensitive part of enabling is change in tlb.c, where CR3 flags get set. Please take a look that what I'm doing makes sense. The patchset is RFC quality and the code requires more testing before it can be applied. The userspace API is not finalized yet. The patchset extends API used by ARM64: PR_GET/SET_TAGGED_ADDR_CTRL. The API is adjusted to not imply ARM TBI: it now allows to request a number of bits of metadata needed and report where these bits are located in the address. There's an alternative proposal[2] for the API based on Intel CET interface. Please let us know if you prefer one over another. The feature competes for bits with 5-level paging: LAM_U48 makes it impossible to map anything about 47-bits. The patchset made these capability mutually exclusive: whatever used first wins. LAM_U57 can be combined with mappings above 47-bits. I include QEMU patch in case if somebody wants to play with the feature. The branch: git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git lam Any comments are welcome. [1] ISE, Chapter 14. https://software.intel.com/content/dam/develop/external/us/en/documents-tps/architecture-instruction-set-extensions-programming-reference.pdf [2] https://github.com/hjl-tools/linux/commit/e85fa032e5b276ddf17edd056f92f599db9e8369 Kirill A. Shutemov (9): mm, arm64: Update PR_SET/GET_TAGGED_ADDR_CTRL interface x86/mm: Fix CR3_ADDR_MASK x86: CPUID and CR3/CR4 flags for Linear Address Masking x86/mm: Introduce TIF_LAM_U57 and TIF_LAM_U48 x86/mm: Provide untagged_addr() helper x86/uaccess: Remove tags from the address before checking x86/mm: Handle tagged memory accesses from kernel threads x86/mm: Make LAM_U48 and mappings above 47-bits mutually exclusive x86/mm: Implement PR_SET/GET_TAGGED_ADDR_CTRL with LAM arch/arm64/include/asm/processor.h | 12 +- arch/arm64/kernel/process.c | 45 +++++- arch/arm64/kernel/ptrace.c | 4 +- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/include/asm/elf.h | 3 +- arch/x86/include/asm/mmu.h | 1 + arch/x86/include/asm/mmu_context.h | 13 ++ arch/x86/include/asm/page_32.h | 3 + arch/x86/include/asm/page_64.h | 19 +++ arch/x86/include/asm/processor-flags.h | 2 +- arch/x86/include/asm/processor.h | 10 ++ arch/x86/include/asm/thread_info.h | 9 +- arch/x86/include/asm/tlbflush.h | 5 + arch/x86/include/asm/uaccess.h | 16 +- arch/x86/include/uapi/asm/processor-flags.h | 6 + arch/x86/kernel/process_64.c | 145 ++++++++++++++++++ arch/x86/kernel/sys_x86_64.c | 5 +- arch/x86/mm/hugetlbpage.c | 6 +- arch/x86/mm/mmap.c | 9 +- arch/x86/mm/tlb.c | 124 +++++++++++++-- kernel/sys.c | 14 +- .../testing/selftests/arm64/tags/tags_test.c | 31 ---- .../selftests/{arm64 => vm}/tags/.gitignore | 0 .../selftests/{arm64 => vm}/tags/Makefile | 0 .../{arm64 => vm}/tags/run_tags_test.sh | 0 tools/testing/selftests/vm/tags/tags_test.c | 57 +++++++ 26 files changed, 464 insertions(+), 76 deletions(-) delete mode 100644 tools/testing/selftests/arm64/tags/tags_test.c rename tools/testing/selftests/{arm64 => vm}/tags/.gitignore (100%) rename tools/testing/selftests/{arm64 => vm}/tags/Makefile (100%) rename tools/testing/selftests/{arm64 => vm}/tags/run_tags_test.sh (100%) create mode 100644 tools/testing/selftests/vm/tags/tags_test.c -- 2.26.2
