On 3/31/22 8:37 PM, Song Chen wrote:
在 2022/4/1 11:01, Yonghong Song 写道:
On 3/31/22 6:41 PM, Song Chen wrote:
syscall_tp only prints the map id and messages when something goes
wrong,
but it doesn't print the value passed from bpf map. I think it's better
to show that value to users.
What's more, i also added a 2-second sleep before calling verify_map,
to make the value more obvious.
Signed-off-by: Song Chen <chensong_2000@xxxxxx>
---
samples/bpf/syscall_tp_user.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/samples/bpf/syscall_tp_user.c
b/samples/bpf/syscall_tp_user.c
index a0ebf1833ed3..1faa7f08054e 100644
--- a/samples/bpf/syscall_tp_user.c
+++ b/samples/bpf/syscall_tp_user.c
@@ -36,6 +36,9 @@ static void verify_map(int map_id)
fprintf(stderr, "failed: map #%d returns value 0\n", map_id);
return;
}
+
+ printf("verify map:%d val: %d\n", map_id, val);
I am not sure how useful it is or anybody really cares.
This is just a sample to demonstrate how bpf tracepoint works.
The error path has error print out already.
Considering we already have
printf("prog #%d: map ids %d %d\n", i, map0_fds[i], map1_fds[i]);
I think your proposed additional printout
printf("verify map:%d val: %d\n", map_id, val);
might be okay. The commit message should be rewritten
to justify this change something like:
we already print out
prog <some number>: map ids <..> <...>
further print out
verify map: ...
will help user to understand the program runs successfully.
I think sleep(2) is unnecessary.
+
val = 0;
if (bpf_map_update_elem(map_id, &key, &val, BPF_ANY) != 0) {
fprintf(stderr, "map_update failed: %s\n", strerror(errno));
@@ -98,6 +101,7 @@ static int test(char *filename, int num_progs)
}
close(fd);
+ sleep(2);
The commit message mentioned this sleep(2) is
to make the value more obvious. I don't know what does this mean.
sleep(2) can be added only if it fixed a bug.
The value in bpf map means how many times trace_enter_open_at are
triggered with tracepoint,sys_enter_openat. Sleep(2) is to enlarge the
result, tell the user how many files are opened in the last 2 seconds.
It shows like this:
sudo ./samples/bpf/syscall_tp
prog #0: map ids 4 5
verify map:4 val: 253
verify map:5 val: 252
If we work harder, we can also print those files' name and opened by
which process.
It's just an improvement instead of a bug fix, i will drop it if
reviewers think it's unnecessary.
Thanks.
BR
chensong
/* verify the map */
for (i = 0; i < num_progs; i++) {
verify_map(map0_fds[i]);
