The kernel currently clears the tag bits (i.e. bits 56-63) in the fault address exposed via siginfo.si_addr and sigcontext.fault_address. However, the tag bits may be needed by tools in order to accurately diagnose memory errors, such as HWASan [1] or future tools based on the Memory Tagging Extension (MTE). We should not stop clearing these bits in the existing fault address fields, because there may be existing userspace applications that are expecting the tag bits to be cleared. Instead, create a new pair of union fields in siginfo._sigfault, and store the tag bits of FAR_EL1 there, together with a mask specifying which bits are valid. However, one does not simply add fields to siginfo, at least not without a mechanism for userspace to detect that they are present and valid. Therefore, the first seven patches in this series introduce a mechanism for userspace to detect the presence of our new siginfo fields, and the last patch uses it to advertise the presence of said fields. The series can be viewed on Gerrit here: https://linux-review.googlesource.com/q/Ia8876bad8c798e0a32df7c2ce1256c4771c81446 [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html Helge Deller (1): parisc: Drop parisc special case for __sighandler_t Peter Collingbourne (7): parisc: start using signal-defs.h arch: move SA_* definitions to generic headers signal: clear non-uapi flag bits when passing/returning sa_flags signal: define the SA_UNSUPPORTED bit in sa_flags signal: deduplicate code dealing with common _sigfault fields signal: define the field siginfo.si_xflags arm64: expose FAR_EL1 tag bits in siginfo Documentation/arm64/tagged-pointers.rst | 21 +++- arch/alpha/include/uapi/asm/signal.h | 14 --- arch/arm/include/asm/signal.h | 2 + arch/arm/include/uapi/asm/signal.h | 28 +---- arch/arm64/include/asm/exception.h | 2 +- arch/arm64/include/asm/signal.h | 19 +++ arch/arm64/include/asm/system_misc.h | 2 +- arch/arm64/include/asm/traps.h | 6 +- arch/arm64/kernel/debug-monitors.c | 5 +- arch/arm64/kernel/entry-common.c | 2 - arch/arm64/kernel/ptrace.c | 7 +- arch/arm64/kernel/sys_compat.c | 5 +- arch/arm64/kernel/traps.c | 29 ++--- arch/arm64/mm/fault.c | 68 ++++++----- arch/h8300/include/uapi/asm/signal.h | 24 ---- arch/ia64/include/uapi/asm/signal.h | 24 ---- arch/m68k/include/uapi/asm/signal.h | 24 ---- arch/mips/include/uapi/asm/signal.h | 12 -- arch/parisc/include/asm/signal.h | 2 + arch/parisc/include/uapi/asm/signal.h | 34 +----- arch/powerpc/include/uapi/asm/signal.h | 24 ---- arch/powerpc/platforms/powernv/vas-fault.c | 1 + arch/s390/include/uapi/asm/signal.h | 24 ---- arch/sparc/include/uapi/asm/signal.h | 4 +- arch/x86/include/uapi/asm/signal.h | 24 ---- arch/x86/kernel/signal_compat.c | 19 +-- arch/xtensa/include/uapi/asm/signal.h | 24 ---- include/linux/compat.h | 4 + include/linux/signal.h | 29 +++++ include/linux/signal_types.h | 12 ++ include/uapi/asm-generic/siginfo.h | 14 +++ include/uapi/asm-generic/signal-defs.h | 58 +++++++++ include/uapi/asm-generic/signal.h | 29 ----- include/uapi/linux/ptrace.h | 12 ++ kernel/ptrace.c | 32 ++++- kernel/signal.c | 134 +++++++++++---------- 36 files changed, 345 insertions(+), 429 deletions(-) create mode 100644 arch/arm64/include/asm/signal.h -- 2.29.0.rc1.297.gfa9743e501-goog
