We have a usecase where we want to audit symbol names (if available) in callback registration hooks. (ex: fentry/nf_register_net_hook)
A few months back, I proposed a bpf_kallsyms_lookup series but it was decided in the reviews that a more generic helper, bpf_snprintf, would be more useful. This series implements the helper according to the feedback received in https://lore.kernel.org/bpf/20201126165748.1748417-1-rev...@google.com/T/#u - A new arg type guarantees the NULL-termination of string arguments and lets us pass format strings in only one arg - A new helper is implemented using that guarantee. Because the format string is known at verification time, the format string validation is done by the verifier - To implement a series of tests for bpf_snprintf, the logic for marshalling variadic args in a fixed-size array is reworked as per: https://lore.kernel.org/bpf/20210310015455.1095207-1-rev...@chromium.org/T/#u Florent Revest (5): bpf: Add a ARG_PTR_TO_CONST_STR argument type bpf: Add a bpf_snprintf helper libbpf: Initialize the bpf_seq_printf parameters array field by field libbpf: Introduce a BPF_SNPRINTF helper macro selftests/bpf: Add a series of tests for bpf_snprintf include/linux/bpf.h | 5 + include/uapi/linux/bpf.h | 28 +++ kernel/bpf/verifier.c | 178 ++++++++++++++++++ kernel/trace/bpf_trace.c | 110 +++++++++++ tools/include/uapi/linux/bpf.h | 28 +++ tools/lib/bpf/bpf_tracing.h | 45 ++++- .../selftests/bpf/prog_tests/snprintf.c | 71 +++++++ .../selftests/bpf/progs/test_snprintf.c | 71 +++++++ 8 files changed, 535 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c -- 2.30.1.766.gb4fecdf3b7-goog
