This patchset adds 2 kfuncs to provide a way to precisely measure the time spent running some code. The first patch provides a way to get cpu cycles counter which is used to feed CLOCK_MONOTONIC_RAW. On x86 architecture it is effectively rdtsc_ordered() function while on other architectures it falls back to __arch_get_hw_counter(). The second patch adds a kfunc to convert cpu cycles to nanoseconds using shift/mult constants discovered by kernel. JIT version is done for x86 for now, on other architectures it falls back to slightly simplified version of vdso_calc_ns. Selftests are also added to check whether the JIT implementation is correct and to show the simplest usage example. Change log: v5 -> v6: * added cover letter * add comment about dropping S64_MAX manipulation in jitted implementation of rdtsc_oredered (Alexey) * add comment about using 'lfence;rdtsc' variant (Alexey) * change the check in fixup_kfunc_call() (Eduard) * make __arch_get_hw_counter() call more aligned with vDSO implementation (Yonghong) v4 -> v5: * use #if instead of #ifdef with IS_ENABLED v3 -> v4: * change name of the helper to bpf_get_cpu_cycles (Andrii) * Hide the helper behind CONFIG_GENERIC_GETTIMEOFDAY to avoid exposing it on architectures which do not have vDSO functions and data * reduce the scope of check of inlined functions in verifier to only 2, which are actually inlined. * change helper name to bpf_cpu_cycles_to_ns. * hide it behind CONFIG_GENERIC_GETTIMEOFDAY to avoid exposing on unsupported architectures. v2 -> v3: * change name of the helper to bpf_get_cpu_cycles_counter to * explicitly mention what counter it provides (Andrii) * move kfunc definition to bpf.h to use it in JIT. * introduce another kfunc to convert cycles into nanoseconds as * more meaningful time units for generic tracing use case (Andrii) v1 -> v2: * Fix incorrect function return value type to u64 * Introduce bpf_jit_inlines_kfunc_call() and use it in mark_fastcall_pattern_for_call() to avoid clobbering in case of running programs with no JIT (Eduard) * Avoid rewriting instruction and check function pointer directly in JIT (Alexei) * Change includes to fix compile issues on non x86 architectures Vadim Fedorenko (4): bpf: add bpf_get_cpu_cycles kfunc bpf: add bpf_cpu_cycles_to_ns helper selftests/bpf: add selftest to check rdtsc jit selftests/bpf: add usage example for cpu cycles kfuncs arch/x86/net/bpf_jit_comp.c | 60 ++++++++++ arch/x86/net/bpf_jit_comp32.c | 33 ++++++ include/linux/bpf.h | 6 + include/linux/filter.h | 1 + kernel/bpf/core.c | 11 ++ kernel/bpf/helpers.c | 32 ++++++ kernel/bpf/verifier.c | 41 ++++++- .../bpf/prog_tests/test_cpu_cycles.c | 35 ++++++ .../selftests/bpf/prog_tests/verifier.c | 2 + .../selftests/bpf/progs/test_cpu_cycles.c | 25 +++++ .../selftests/bpf/progs/verifier_cpu_cycles.c | 104 ++++++++++++++++++ 11 files changed, 344 insertions(+), 6 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/test_cpu_cycles.c create mode 100644 tools/testing/selftests/bpf/progs/test_cpu_cycles.c create mode 100644 tools/testing/selftests/bpf/progs/verifier_cpu_cycles.c -- 2.43.5
