On 18.02.23 22:14, Rick Edgecombe wrote:
The x86 Control-flow Enforcement Technology (CET) feature includes a new type of memory called shadow stack. This shadow stack memory has some unusual properties, which requires some core mm changes to function properly. One of these unusual properties is that shadow stack memory is writable, but only in limited ways. These limits are applied via a specific PTE bit combination. Nevertheless, the memory is writable, and core mm code will need to apply the writable permissions in the typical paths that call pte_mkwrite(). In addition to VM_WRITE, the shadow stack VMA's will have a flag denoting that they are special shadow stack flavor of writable memory. So make pte_mkwrite() take a VMA, so that the x86 implementation of it can know to create regular writable memory or shadow stack memory. Apply the same changes for pmd_mkwrite() and huge_pte_mkwrite(). No functional change. Cc: linux-doc@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linux-alpha@xxxxxxxxxxxxxxx Cc: linux-snps-arc@xxxxxxxxxxxxxxxxxxx Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linux-csky@xxxxxxxxxxxxxxx Cc: linux-hexagon@xxxxxxxxxxxxxxx Cc: linux-ia64@xxxxxxxxxxxxxxx Cc: loongarch@xxxxxxxxxxxxxxx Cc: linux-m68k@xxxxxxxxxxxxxxxxxxxx Cc: Michal Simek <monstr@xxxxxxxxx> Cc: Dinh Nguyen <dinguyen@xxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxxx Cc: openrisc@xxxxxxxxxxxxxxxxxxxx Cc: linux-parisc@xxxxxxxxxxxxxxx Cc: linuxppc-dev@xxxxxxxxxxxxxxxx Cc: linux-riscv@xxxxxxxxxxxxxxxxxxx Cc: linux-s390@xxxxxxxxxxxxxxx Cc: linux-sh@xxxxxxxxxxxxxxx Cc: sparclinux@xxxxxxxxxxxxxxx Cc: linux-um@xxxxxxxxxxxxxxxxxxx Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx Cc: linux-arch@xxxxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx Tested-by: Pengfei Xu <pengfei.xu@xxxxxxxxx> Suggested-by: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> --- Hi Non-x86 Arch’s, x86 has a feature that allows for the creation of a special type of writable memory (shadow stack) that is only writable in limited specific ways. Previously, changes were proposed to core MM code to teach it to decide when to create normally writable memory or the special shadow stack writable memory, but David Hildenbrand suggested[0] to change pXX_mkwrite() to take a VMA, so awareness of shadow stack memory can be moved into x86 code. Since pXX_mkwrite() is defined in every arch, it requires some tree-wide changes. So that is why you are seeing some patches out of a big x86 series pop up in your arch mailing list. There is no functional change. After this refactor, the shadow stack series goes on to use the arch helpers to push shadow stack memory details inside arch/x86. Testing was just 0-day build testing. Hopefully that is enough context. Thanks! [0] https://lore.kernel.org/lkml/0e29a2d0-08d8-bcd6-ff26-4bea0e4037b0@xxxxxxxxxx/#t v6: - New patch --- Documentation/mm/arch_pgtable_helpers.rst | 9 ++++++--- arch/alpha/include/asm/pgtable.h | 6 +++++- arch/arc/include/asm/hugepage.h | 2 +- arch/arc/include/asm/pgtable-bits-arcv2.h | 7 ++++++- arch/arm/include/asm/pgtable-3level.h | 7 ++++++- arch/arm/include/asm/pgtable.h | 2 +- arch/arm64/include/asm/pgtable.h | 4 ++-- arch/csky/include/asm/pgtable.h | 2 +- arch/hexagon/include/asm/pgtable.h | 2 +- arch/ia64/include/asm/pgtable.h | 2 +- arch/loongarch/include/asm/pgtable.h | 4 ++-- arch/m68k/include/asm/mcf_pgtable.h | 2 +- arch/m68k/include/asm/motorola_pgtable.h | 6 +++++- arch/m68k/include/asm/sun3_pgtable.h | 6 +++++- arch/microblaze/include/asm/pgtable.h | 2 +- arch/mips/include/asm/pgtable.h | 6 +++--- arch/nios2/include/asm/pgtable.h | 2 +- arch/openrisc/include/asm/pgtable.h | 2 +- arch/parisc/include/asm/pgtable.h | 6 +++++- arch/powerpc/include/asm/book3s/32/pgtable.h | 2 +- arch/powerpc/include/asm/book3s/64/pgtable.h | 4 ++-- arch/powerpc/include/asm/nohash/32/pgtable.h | 2 +- arch/powerpc/include/asm/nohash/32/pte-8xx.h | 2 +- arch/powerpc/include/asm/nohash/64/pgtable.h | 2 +- arch/riscv/include/asm/pgtable.h | 6 +++--- arch/s390/include/asm/hugetlb.h | 4 ++-- arch/s390/include/asm/pgtable.h | 4 ++-- arch/sh/include/asm/pgtable_32.h | 10 ++++++++-- arch/sparc/include/asm/pgtable_32.h | 2 +- arch/sparc/include/asm/pgtable_64.h | 6 +++--- arch/um/include/asm/pgtable.h | 2 +- arch/x86/include/asm/pgtable.h | 6 ++++-- arch/xtensa/include/asm/pgtable.h | 2 +- include/asm-generic/hugetlb.h | 4 ++-- include/linux/mm.h | 2 +- mm/debug_vm_pgtable.c | 16 ++++++++-------- mm/huge_memory.c | 6 +++--- mm/hugetlb.c | 4 ++-- mm/memory.c | 4 ++-- mm/migrate_device.c | 2 +- mm/mprotect.c | 2 +- mm/userfaultfd.c | 2 +- 42 files changed, 106 insertions(+), 69 deletions(-)
That looks painful but IMHO worth it :) Acked-by: David Hildenbrand <david@xxxxxxxxxx> -- Thanks, David / dhildenb
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