Patch 1 fixes a KVM+rseq bug where KVM's handling of TIF_NOTIFY_RESUME, e.g. for task migration, clears the flag without informing rseq and leads to stale data in userspace's rseq struct.
Patch 2 is a cleanup to try and make future bugs less likely. It's also a baby step towards moving and renaming tracehook_notify_resume() since it has nothing to do with tracing.
Patch 3 is a fix/cleanup to stop overriding x86's unistd_{32,64}.h when the include path (intentionally) omits tools' uapi headers. KVM's selftests do exactly that so that they can pick up the uapi headers from the installed kernel headers, and still use various tools/ headers that mirror kernel code, e.g. linux/types.h. This allows the new test in patch 4 to reference __NR_rseq without having to manually define it.
Patch 4 is a regression test for the KVM+rseq bug.
Patch 5 is a cleanup made possible by patch 3.
Based on commit 835d31d319d9 ("Merge tag 'media/v5.15-1' of ...").
v3: - Collect Ack/Review. [Mathieu, Ben] - Add explicit smp_wmb() instead of relying on atomic_inc() to do a full barrier. [Mathieu] - Add lots and lots of comments in the selftest, especially around why the migration thread needs a udelay(). [Mathieu] - Delay between 1us and 10us to reduce the odds of having a hard dependency on arch/kernel behavior. [Mathieu] - Dropped an s390 change in patch 2 after a rebase to upstream master.
v2: - https://lkml.kernel.org/r/20210820225002.310652-1-seanjc@google.com - Don't touch rseq_cs when handling KVM case so that rseq_syscall() will still detect a naughty userspace. [Mathieu] - Use a sequence counter + retry in the test to ensure the process isn't migrated between sched_getcpu() and reading rseq.cpu_id, i.e. to avoid a flaky test. [Mathieu] - Add Mathieu's ack for patch 2. - Add more comments in the test.
v1: https://lkml.kernel.org/r/20210818001210.4073390-1-seanjc@google.com
Sean Christopherson (5): KVM: rseq: Update rseq when processing NOTIFY_RESUME on xfer to KVM guest entry: rseq: Call rseq_handle_notify_resume() in tracehook_notify_resume() tools: Move x86 syscall number fallbacks to .../uapi/ KVM: selftests: Add a test for KVM_RUN+rseq to detect task migration bugs KVM: selftests: Remove __NR_userfaultfd syscall fallback
arch/arm/kernel/signal.c | 1 - arch/arm64/kernel/signal.c | 1 - arch/csky/kernel/signal.c | 4 +- arch/mips/kernel/signal.c | 4 +- arch/powerpc/kernel/signal.c | 4 +- include/linux/tracehook.h | 2 + kernel/entry/common.c | 4 +- kernel/rseq.c | 14 +- .../x86/include/{ => uapi}/asm/unistd_32.h | 0 .../x86/include/{ => uapi}/asm/unistd_64.h | 3 - tools/testing/selftests/kvm/.gitignore | 1 + tools/testing/selftests/kvm/Makefile | 3 + tools/testing/selftests/kvm/rseq_test.c | 236 ++++++++++++++++++ 13 files changed, 257 insertions(+), 20 deletions(-) rename tools/arch/x86/include/{ => uapi}/asm/unistd_32.h (100%) rename tools/arch/x86/include/{ => uapi}/asm/unistd_64.h (83%) create mode 100644 tools/testing/selftests/kvm/rseq_test.c