Hi Andrey, On 09/03/18 14:01, Andrey Konovalov wrote:
arm64 has a feature called Top Byte Ignore, which allows to embed pointer tags into the top byte of each pointer. Userspace programs (such as HWASan, a memory debugging tool [1]) might use this feature and pass tagged user pointers to the kernel through syscalls or other interfaces.
If you propose changing the ABI, then Documentation/arm64/tagged-pointers.txt needs to reflect the new one, since passing nonzero tags via syscalls is currently explicitly forbidden.
Robin.
This patch makes a few of the kernel interfaces accept tagged user pointers. The kernel is already able to handle user faults with tagged pointers and has the untagged_addr macro, which this patchset reuses. We're not trying to cover all possible ways the kernel accepts user pointers in one patchset, so this one should be considered as a start. It would be nice to learn about the interfaces that I missed though. Sending this as an RFC, as I'm not sure if this should be committed as is, and would like to receive some feedback. Thanks! [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html Andrey Konovalov (6): arm64: add type casts to untagged_addr macro arm64: untag user addresses in copy_from_user and others mm, arm64: untag user addresses in memory syscalls mm, arm64: untag user addresses in mm/gup.c lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user arch: add untagged_addr definition for other arches arch/alpha/include/asm/uaccess.h | 2 ++ arch/arc/include/asm/uaccess.h | 1 + arch/arm/include/asm/uaccess.h | 2 ++ arch/arm64/include/asm/uaccess.h | 9 +++++++-- arch/blackfin/include/asm/uaccess.h | 2 ++ arch/c6x/include/asm/uaccess.h | 2 ++ arch/cris/include/asm/uaccess.h | 2 ++ arch/frv/include/asm/uaccess.h | 2 ++ arch/ia64/include/asm/uaccess.h | 2 ++ arch/m32r/include/asm/uaccess.h | 2 ++ arch/m68k/include/asm/uaccess.h | 2 ++ arch/metag/include/asm/uaccess.h | 2 ++ arch/microblaze/include/asm/uaccess.h | 2 ++ arch/mips/include/asm/uaccess.h | 2 ++ arch/mn10300/include/asm/uaccess.h | 2 ++ arch/nios2/include/asm/uaccess.h | 2 ++ arch/openrisc/include/asm/uaccess.h | 2 ++ arch/parisc/include/asm/uaccess.h | 2 ++ arch/powerpc/include/asm/uaccess.h | 2 ++ arch/riscv/include/asm/uaccess.h | 2 ++ arch/score/include/asm/uaccess.h | 2 ++ arch/sh/include/asm/uaccess.h | 2 ++ arch/sparc/include/asm/uaccess.h | 2 ++ arch/tile/include/asm/uaccess.h | 2 ++ arch/x86/include/asm/uaccess.h | 2 ++ arch/xtensa/include/asm/uaccess.h | 2 ++ include/asm-generic/uaccess.h | 2 ++ lib/strncpy_from_user.c | 2 ++ lib/strnlen_user.c | 2 ++ mm/gup.c | 12 ++++++++++++ mm/madvise.c | 2 ++ mm/mempolicy.c | 6 ++++++ mm/mincore.c | 2 ++ mm/mlock.c | 5 +++++ mm/mmap.c | 9 +++++++++ mm/mprotect.c | 2 ++ mm/mremap.c | 2 ++ mm/msync.c | 3 +++ 38 files changed, 105 insertions(+), 2 deletions(-)
