[RFCv2 00/10] Linear Address Masking enabling

Kirill A. Shutemov
2022-05-11T02:30:03Z

Hi all. Here's long overdue update on LAM enabling.

# Description #

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 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.

[1] ISE, Chapter 14.
https://software.intel.com/content/dam/develop/external/us/en/documents-tps/architecture-instruction-set-extensions-programming-reference.pdf

# What's new #

The main change is interface rework. It is now arch_prctl(2)-based and
suppose to be extendable to CET.

QEMU implementation is also updated. It can now be applied onto current
master branch. QEMU patch as it is was rejected by upstream, but it is
functinal and can be used for testing.

Please take a look. Any suggestions are welcome.

v2:
- Rebased onto v5.18-rc1
- New arch_prctl(2)-based API
- Expose status of LAM (or other thread features) in
/proc/$PID/arch_status.

Kirill A. Shutemov (10):
x86/mm: Fix CR3_ADDR_MASK
x86: CPUID and CR3/CR4 flags for Linear Address Masking
x86: Introduce userspace API to handle per-thread features
x86/mm: Introduce X86_THREAD_LAM_U48 and X86_THREAD_LAM_U57
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: Add userspace API to enable Linear Address Masking
x86: Expose thread features status in /proc/$PID/arch_status

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 | 20 ++++
arch/x86/include/asm/processor-flags.h | 2 +-
arch/x86/include/asm/processor.h | 3 +
arch/x86/include/asm/tlbflush.h | 5 +
arch/x86/include/asm/uaccess.h | 15 ++-
arch/x86/include/uapi/asm/prctl.h | 8 ++
arch/x86/include/uapi/asm/processor-flags.h | 6 +
arch/x86/kernel/Makefile | 2 +
arch/x86/kernel/fpu/xstate.c | 47 --------
arch/x86/kernel/proc.c | 63 ++++++++++
arch/x86/kernel/process.c | 56 +++++++++
arch/x86/kernel/process.h | 2 +
arch/x86/kernel/process_64.c | 46 ++++++++
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 | 123 +++++++++++++++++---
22 files changed, 367 insertions(+), 72 deletions(-)
create mode 100644 arch/x86/kernel/proc.c

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2.35.1