Messages in this thread | | | From | Benjamin Gray <> | Subject | [RFC PATCH 00/13] Add DEXCR support | Date | Mon, 28 Nov 2022 13:44:45 +1100 |
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This series is based on initial work by Chris Riedl that was not sent to the list.
Adds a kernel interface for userspace to interact with the DEXCR. The DEXCR is a SPR that allows control over various execution 'aspects', such as indirect branch prediction and enabling the hashst/hashchk instructions. Further details are in ISA 3.1B Book 3 chapter 12.
This RFC proposes an interface for users to interact with the DEXCR. It aims to support
* Querying supported aspects * Getting/setting aspects on a per-process level * Allowing global overrides across all processes
There are some parts that I'm not sure on the best way to approach (hence RFC):
* The feature names in arch/powerpc/kernel/dt_cpu_ftrs.c appear to be unimplemented in skiboot, so are being defined by this series. Is being so verbose fine? * What aspects should be editable by a process? E.g., SBHE has effects that potentially bleed into other processes. Should it only be system wide configurable? * Should configuring certain aspects for the process be non-privileged? E.g., Is there harm in always allowing configuration of IBRTPD, SRAPD? The *FORCE_SET* action prevents further process local changes regardless of privilege. * The tests fail Patchwork CI because of the new prctl macros, and the CI doesn't run headers_install and add -isystem <buildpath>/usr/include to the make command. * On handling an exception, I don't check if the NPHIE bit is enabled in the DEXCR. To do so would require reading both the DEXCR and HDEXCR, for little gain (it should only matter that the current instruction was a hashchk. If so, the only reason it would cause an exception is the failed check. If the instruction is rewritten between exception and check we'd be wrong anyway).
The series is based on the earlier selftest utils series[1], so the tests won't build at all without applying that first. The kernel side should build fine on ppc/next 247f34f7b80357943234f93f247a1ae6b6c3a740 though.
[1]: https://patchwork.ozlabs.org/project/linuxppc-dev/cover/20221122231103.15829-1-bgray@linux.ibm.com/
Benjamin Gray (13): powerpc/book3s: Add missing <linux/sched.h> include powerpc: Add initial Dynamic Execution Control Register (DEXCR) support powerpc/dexcr: Handle hashchk exception powerpc/dexcr: Support userspace ROP protection prctl: Define PowerPC DEXCR interface powerpc/dexcr: Add prctl implementation powerpc/dexcr: Add sysctl entry for SBHE system override powerpc/dexcr: Add enforced userspace ROP protection config selftests/powerpc: Add more utility macros selftests/powerpc: Add hashst/hashchk test selftests/powerpc: Add DEXCR prctl, sysctl interface test selftests/powerpc: Add DEXCR status utility lsdexcr Documentation: Document PowerPC kernel DEXCR interface
Documentation/powerpc/dexcr.rst | 183 +++++++++++ Documentation/powerpc/index.rst | 1 + arch/powerpc/Kconfig | 5 + arch/powerpc/include/asm/book3s/64/kexec.h | 6 + arch/powerpc/include/asm/book3s/64/kup.h | 1 + arch/powerpc/include/asm/cputable.h | 8 +- arch/powerpc/include/asm/ppc-opcode.h | 1 + arch/powerpc/include/asm/processor.h | 33 ++ arch/powerpc/include/asm/reg.h | 7 + arch/powerpc/kernel/Makefile | 1 + arch/powerpc/kernel/dexcr.c | 310 ++++++++++++++++++ arch/powerpc/kernel/dt_cpu_ftrs.c | 4 + arch/powerpc/kernel/process.c | 31 +- arch/powerpc/kernel/prom.c | 4 + arch/powerpc/kernel/traps.c | 6 + include/uapi/linux/prctl.h | 14 + kernel/sys.c | 16 + tools/testing/selftests/powerpc/Makefile | 1 + .../selftests/powerpc/dexcr/.gitignore | 3 + .../testing/selftests/powerpc/dexcr/Makefile | 11 + tools/testing/selftests/powerpc/dexcr/cap.c | 72 ++++ tools/testing/selftests/powerpc/dexcr/cap.h | 18 + tools/testing/selftests/powerpc/dexcr/dexcr.c | 118 +++++++ tools/testing/selftests/powerpc/dexcr/dexcr.h | 54 +++ .../selftests/powerpc/dexcr/dexcr_test.c | 241 ++++++++++++++ .../selftests/powerpc/dexcr/hashchk_test.c | 229 +++++++++++++ .../testing/selftests/powerpc/dexcr/lsdexcr.c | 178 ++++++++++ tools/testing/selftests/powerpc/include/reg.h | 4 + .../testing/selftests/powerpc/include/utils.h | 44 +++ 29 files changed, 1602 insertions(+), 2 deletions(-) create mode 100644 Documentation/powerpc/dexcr.rst create mode 100644 arch/powerpc/kernel/dexcr.c create mode 100644 tools/testing/selftests/powerpc/dexcr/.gitignore create mode 100644 tools/testing/selftests/powerpc/dexcr/Makefile create mode 100644 tools/testing/selftests/powerpc/dexcr/cap.c create mode 100644 tools/testing/selftests/powerpc/dexcr/cap.h create mode 100644 tools/testing/selftests/powerpc/dexcr/dexcr.c create mode 100644 tools/testing/selftests/powerpc/dexcr/dexcr.h create mode 100644 tools/testing/selftests/powerpc/dexcr/dexcr_test.c create mode 100644 tools/testing/selftests/powerpc/dexcr/hashchk_test.c create mode 100644 tools/testing/selftests/powerpc/dexcr/lsdexcr.c
base-commit: 9dc58a6040662faaf24c8932861f485670fce7ff -- 2.38.1
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