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authorArnaldo Carvalho de Melo <acme@redhat.com>2018-08-06 15:15:18 +0300
committerArnaldo Carvalho de Melo <acme@redhat.com>2018-08-08 21:55:55 +0300
commit53a5d7b80032fcf48cdc5a6c96c8dc8a120b64ef (patch)
tree06ebe9a88eff99e3f3fcea2e5f21a4523be95793 /tools
parent7402e543a74a08ae630234012356ff5cf947bd61 (diff)
downloadlinux-53a5d7b80032fcf48cdc5a6c96c8dc8a120b64ef.tar.xz
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>
Diffstat (limited to 'tools')
-rw-r--r--tools/perf/examples/bpf/hello.c9
-rw-r--r--tools/perf/include/bpf/stdio.h19
2 files changed, 28 insertions, 0 deletions
diff --git a/tools/perf/examples/bpf/hello.c b/tools/perf/examples/bpf/hello.c
new file mode 100644
index 000000000000..cf3c2fdc7f79
--- /dev/null
+++ b/tools/perf/examples/bpf/hello.c
@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+int syscall_enter(openat)(void *args)
+{
+ puts("Hello, world\n");
+ return 0;
+}
+
+license(GPL);
diff --git a/tools/perf/include/bpf/stdio.h b/tools/perf/include/bpf/stdio.h
new file mode 100644
index 000000000000..2899cb7bfed8
--- /dev/null
+++ b/tools/perf/include/bpf/stdio.h
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <bpf.h>
+
+struct bpf_map SEC("maps") __bpf_stdout__ = {
+ .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
+ .key_size = sizeof(int),
+ .value_size = sizeof(u32),
+ .max_entries = __NR_CPUS__,
+};
+
+static int (*perf_event_output)(void *, struct bpf_map *, int, void *, unsigned long) =
+ (void *)BPF_FUNC_perf_event_output;
+
+#define puts(from) \
+ ({ const int __len = sizeof(from); \
+ char __from[__len] = from; \
+ perf_event_output(args, &__bpf_stdout__, BPF_F_CURRENT_CPU, \
+ &__from, __len & (sizeof(from) - 1)); })