perf bpf: Add probe() helper to reduce kprobes boilerplate
So that kprobe definitions become: int probe(function, variables)(void *ctx, int err, var1, var2, ...) The existing 5sec.c, got converted and goes from: SEC("func=hrtimer_nanosleep rqtp->tv_sec") int func(void *ctx, int err, long sec) { } To: int probe(hrtimer_nanosleep, rqtp->tv_sec)(void *ctx, int err, long sec) { } If we decide to add tv_nsec as well, then it becomes: $ cat tools/perf/examples/bpf/5sec.c #include <bpf.h> int probe(hrtimer_nanosleep, rqtp->tv_sec rqtp->tv_nsec)(void *ctx, int err, long sec, long nsec) { return sec == 5; } license(GPL); $ And if we run it, system wide as before and run some 'sleep' with values for the tv_nsec field, we get: # perf trace --no-syscalls -e tools/perf/examples/bpf/5sec.c 0.000 perf_bpf_probe:hrtimer_nanosleep:(ffffffff9811b5f0) tv_sec=5 tv_nsec=100000000 9641.650 perf_bpf_probe:hrtimer_nanosleep:(ffffffff9811b5f0) tv_sec=5 tv_nsec=123450001 ^C# Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Wang Nan <wangnan0@huawei.com> Link: https://lkml.kernel.org/n/tip-1v9r8f6ds5av0w9pcwpeknyl@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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@ -15,6 +15,13 @@
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. While this is running, run something like "sleep 5s".
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. If we decide to add tv_nsec as well, then it becomes:
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int probe(hrtimer_nanosleep, rqtp->tv_sec rqtp->tv_nsec)(void *ctx, int err, long sec, long nsec)
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I.e. add where it comes from (rqtp->tv_nsec) and where it will be
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accessible in the function body (nsec)
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# perf trace --no-syscalls -e tools/perf/examples/bpf/5sec.c/call-graph=dwarf/
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0.000 perf_bpf_probe:func:(ffffffff9811b5f0) tv_sec=5
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hrtimer_nanosleep ([kernel.kallsyms])
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#include <bpf.h>
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SEC("func=hrtimer_nanosleep rqtp->tv_sec")
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int func(void *ctx, int err, long sec)
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int probe(hrtimer_nanosleep, rqtp->tv_sec)(void *ctx, int err, long sec)
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{
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return sec == 5;
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}
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@ -3,6 +3,9 @@
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#define _PERF_BPF_H
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#define SEC(NAME) __attribute__((section(NAME), used))
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#define probe(function, vars) \
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SEC(#function "=" #function " " #vars) function
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#define license(name) \
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char _license[] SEC("license") = #name; \
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int _version SEC("version") = LINUX_VERSION_CODE;
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