Arnaldo Carvalho de Melo 53a5d7b800 perf bpf: Add bpf/stdio.h wrapper to bpf_perf_event_output function ... That, together with the map __bpf_output__ that is already handled by 'perf trace' to print that event's contents as strings provides a debugging facility, to show it in use, print a simple string everytime the syscalls:sys_enter_openat() syscall tracepoint is hit: # cat tools/perf/examples/bpf/hello.c #include <stdio.h> int syscall_enter(openat)(void *args) { puts("Hello, world\n"); return 0; } license(GPL); # # perf trace -e openat,tools/perf/examples/bpf/hello.c cat /etc/passwd > /dev/null 0.016 ( ): __bpf_stdout__:Hello, world 0.018 ( 0.010 ms): cat/9079 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: CLOEXEC) = 3 0.057 ( ): __bpf_stdout__:Hello, world 0.059 ( 0.011 ms): cat/9079 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: CLOEXEC) = 3 0.417 ( ): __bpf_stdout__:Hello, world 0.419 ( 0.009 ms): cat/9079 openat(dfd: CWD, filename: /etc/passwd) = 3 # This is part of an ongoing experimentation on making eBPF scripts as consumed by perf to be as concise as possible and using familiar concepts such as stdio.h functions, that end up just wrapping the existing BPF functions, trying to hide as much boilerplate as possible while using just conventions and C preprocessor tricks. 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-4tiaqlx5crf0fwpe7a6j84x7@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>		2018-08-08 15:55:55 -03:00
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bpf.h	perf bpf: Add struct bpf_map struct	2018-08-08 15:55:54 -03:00
stdio.h	perf bpf: Add bpf/stdio.h wrapper to bpf_perf_event_output function	2018-08-08 15:55:55 -03:00