Recently, a security issue related to orig_x0 was discovered and fixed
in arm64, but there are still no test cases covering it. Seccomp,
tracepoints, and audit can observe a stale value for x0 after a ptracer
or SECCOMP_RET_TRACE modifies x0.

As Kees suggested, this series adds two kselftests for arm64 that validate
the orig_x0 re-synchronisation fix in ptrace, the first one is for ptrace
update, the second one is for SECCOMP_RET_TRACE update.

Link: https://lore.kernel.org/all/20260717182758.17111-1-will@kernel.org/
Link: https://lore.kernel.org/all/20260716120640.6590-1-will@kernel.org/
Link: https://lore.kernel.org/all/202607152004.DEA95D63@keescook/

Changes in v2:
- Update the 2st testcase to cover the corner case pointed out by Sashiko[1].

[1]: https://sashiko.dev/#/patchset/20260716120640.6590-1-will@kernel.org

Jinjie Ruan (2):
  kselftest/arm64: Add seccomp ptrace x0 bypass test
  kselftest/arm64: Add testcase for SECCOMP_RET_TRACE orig_x0 bypass

 tools/testing/selftests/arm64/abi/.gitignore  |   2 +
 tools/testing/selftests/arm64/abi/Makefile    |   2 +-
 .../arm64/abi/seccomp_ptrace_x0_bypass.c      | 181 ++++++++++++++++
 .../arm64/abi/seccomp_ret_trace_x0_bypass.c   | 196 ++++++++++++++++++
 4 files changed, 380 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/arm64/abi/seccomp_ptrace_x0_bypass.c
 create mode 100644 tools/testing/selftests/arm64/abi/seccomp_ret_trace_x0_bypass.c

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2.34.1