Messages in this thread | | | Date | Fri, 1 Apr 2022 09:28:35 -0700 | Subject | Re: [PATCH] sample: bpf: syscall_tp_user: print result of verify_map | From | Yonghong Song <> |
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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@189.cn> >>> --- >>> 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]); >>
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