[PATCH bpf-next v5 0/2] bpf: Reject attaching fexit/fmod_ret to __noreturn functions

[Yafang Shao <laoar.shao@gmail.com>]

Attaching fexit probes to functions marked with __noreturn may lead to
unpredictable behavior. To avoid this, we will reject attaching probes to
such functions. Currently, there is no ideal solution, so we will hardcode
a check for all __noreturn functions.

Once a more robust solution is implemented, this workaround can be removed.

v4->v5:
- Remove unnecessary functions (Alexei)
- Use BTF_ID directly (Alexei)

v3->v4: https://lore.kernel.org/bpf/20250317121735.86515-1-laoar.shao@gmail.com/
- Reject also fmod_ret (Alexei)
- Fix build warnings and remove unnecessary functions (Alexei)

v1->v2: https://lore.kernel.org/bpf/20250223062735.3341-1-laoar.shao@gmail.com/
- keep tools/objtool/noreturns.h as is (Josh)
- Add noreturns.h to objtool/sync-check.sh (Josh)
- Add verbose for the reject and simplify the test case (Song)

v1: https://lore.kernel.org/bpf/20250211023359.1570-1-laoar.shao@gmail.com/

Yafang Shao (2):
  bpf: Reject attaching fexit/fmod_ret to __noreturn functions
  selftests/bpf: Add selftest for attaching fexit to __noreturn
    functions

 kernel/bpf/verifier.c                         | 32 +++++++++++++++++++
 .../bpf/prog_tests/fexit_noreturns.c          |  9 ++++++
 .../selftests/bpf/progs/fexit_noreturns.c     | 15 +++++++++
 3 files changed, 56 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/fexit_noreturns.c
 create mode 100644 tools/testing/selftests/bpf/progs/fexit_noreturns.c

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2.43.5