[PATCH 02/28] perf augmented_syscalls: Filter on a hard coded pid

Arnaldo Carvalho de Melo
2018-11-22T03:36:33Z

Just to show where we'll hook pid based filters, and what we use to
obtain the current pid, using a BPF getpid() equivalent.

Now we need to remove that hardcoded PID with a BPF hash map, so that we
start by filtering 'perf trace's own PID, implement the --filter-pid
functionality, etc.

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-oshrcgcekiyhd0whwisxfvtv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/examples/bpf/augmented_raw_syscalls.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/examples/bpf/augmented_raw_syscalls.c b/tools/perf/examples/bpf/augmented_raw_syscalls.c
index 90a19336310b..2feb00018f79 100644
--- a/tools/perf/examples/bpf/augmented_raw_syscalls.c
+++ b/tools/perf/examples/bpf/augmented_raw_syscalls.c
@@ -15,6 +15,7 @@
*/

#include <stdio.h>
+#include <unistd.h>
#include <linux/socket.h>

/* bpf-output associated map */
@@ -56,6 +57,9 @@ int sys_enter(struct syscall_enter_args *args)
unsigned int len = sizeof(augmented_args);
const void *filename_arg = NULL;

+ if (getpid() == 2971)
+ return 0;
+
probe_read(&augmented_args.args, sizeof(augmented_args.args), args);
/*
* Yonghong and Edward Cree sayz:
@@ -125,7 +129,7 @@ int sys_enter(struct syscall_enter_args *args)
SEC("raw_syscalls:sys_exit")
int sys_exit(struct syscall_exit_args *args)
{
- return 1; /* 0 as soon as we start copying data returned by the kernel, e.g. 'read' */
+ return getpid() != 2971;
}

license(GPL);
--
2.14.5