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McKenney" , x86@kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" If an application registers rseq, and ever switches to another pkey protection (such that the rseq becomes inaccessible), then any context switch will cause failure in __rseq_handle_notify_resume() attempting to read/write struct rseq and/or rseq_cs. Since context switches are asynchronous and are outside of the application control (not part of the restricted code scope), temporarily enable access to 0 (default) PKEY to read/write rseq/rseq_cs. 0 is the only PKEY supported for rseq for now. Theoretically other PKEYs can be supported, but it's unclear how/if that can work. So for now we don't support that to simplify code. Cc: Mathieu Desnoyers Cc: Peter Zijlstra Cc: "Paul E. McKenney" Cc: Boqun Feng Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: Aruna Ramakrishna Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org Dmitry Vyukov (4): pkeys: add API to switch to permissive/zero pkey register x86/signal: Use write_permissive_pkey_val() helper rseq: Make rseq work with protection keys selftests/rseq: Add test for rseq+pkeys arch/x86/Kconfig | 1 + arch/x86/include/asm/pkeys.h | 30 +++++++ arch/x86/include/asm/pkru.h | 10 ++- arch/x86/kernel/signal.c | 6 +- include/linux/pkeys.h | 31 +++++++ include/uapi/linux/rseq.h | 4 + kernel/rseq.c | 11 +++ mm/Kconfig | 2 + tools/testing/selftests/rseq/Makefile | 2 +- tools/testing/selftests/rseq/pkey_test.c | 101 +++++++++++++++++++++++ tools/testing/selftests/rseq/rseq.h | 1 + 11 files changed, 191 insertions(+), 8 deletions(-) create mode 100644 tools/testing/selftests/rseq/pkey_test.c base-commit: 4a95bc121ccdaee04c4d72f84dbfa6b880a514b6 -- 2.49.0.1143.g0be31eac6b-goog