[PATCH] samples/bpf: Support both enter and exit kprobes in helper

[Lior Ribak <liorribak@gmail.com>]

Currently, in bpf_load.c, the function write_kprobe_events sets
the function name to probe as the probe name.
Even though it's valid to set one kprobe on enter and another on exit,
bpf_load.c won't handle it, and will return an error 'File exists'.

Add a prefix to the event name to indicate if it's on enter or exit,
so both an enter and an exit kprobes can be attached.

Signed-off-by: Lior Ribak <liorribak@gmail.com>
---
 samples/bpf/bpf_load.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index c5ad528f046e..69102358e91a 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -184,18 +184,24 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
 
 #ifdef __x86_64__
 		if (strncmp(event, "sys_", 4) == 0) {
-			snprintf(buf, sizeof(buf), "%c:__x64_%s __x64_%s",
-				is_kprobe ? 'p' : 'r', event, event);
+			if (is_kprobe)
+				event_prefix = "__x64_enter_";
+			else
+				event_prefix = "__x64_exit_";
+			snprintf(buf, sizeof(buf), "%c:%s%s __x64_%s",
+				is_kprobe ? 'p' : 'r', event_prefix, event, event);
 			err = write_kprobe_events(buf);
-			if (err >= 0) {
+			if (err >= 0)
 				need_normal_check = false;
-				event_prefix = "__x64_";
-			}
 		}
 #endif
 		if (need_normal_check) {
-			snprintf(buf, sizeof(buf), "%c:%s %s",
-				is_kprobe ? 'p' : 'r', event, event);
+			if (is_kprobe)
+				event_prefix = "enter_";
+			else
+				event_prefix = "exit_";
+			snprintf(buf, sizeof(buf), "%c:%s%s %s",
+				is_kprobe ? 'p' : 'r', event_prefix, event, event);
 			err = write_kprobe_events(buf);
 			if (err < 0) {
 				printf("failed to create kprobe '%s' error '%s'\n",
-- 
2.25.1