On Sat, Aug 12, 2017 at 5:14 AM, Fenggang Wu via iovisor-dev
<
iovisor-dev@...> wrote:
> Hi there,
>
> I am trying out bcc tools from
http://github.com/iovisor/bcc, more
> specificaly profile.py and offcputime.py. However in the tracing result,
> user functions are shown as "[unknown]", whereas kernel functions such as
> "sys_*" are interpreted well. Any ideas?
>
> Thank you very much!
> Fenggang
>
> ======
>
> Here are more details (I use profile.py as the example). If there are more
> details that are necessary please feel free to let me know.
>
> 1) how to reproduce the issue:
> #~> cat Makefile
> all:
> g++ -o spin spin.cc
> objcopy --only-keep-debug spin spin.debug
> objcopy --add-gnu-debuglink=spin.debug spin
>
>
> clean:
> rm spin spin.debug
> #~> cat spin.cc
> #include<iostream>
> using namespace std;
> void myfunc() {
> int i, j, cnt;
> cout << "my func" << endl;
> for (i = 0; i < 4; i++) {
> for ( j = 0; j < 500000000; j++) {
> cnt ^= i + j;
> }
> cout << i << " " << cnt;
> }
> }
>
> int main() {
> cout << "hello" << endl;
> myfunc();
> }
> #~> cat test_profile.sh
> #!/bin/bash
> sudo make
>
> sudo -- bash -c "./spin & PID=\$!; echo PID=\$PID; cat /proc/\$PID/maps;
> (trap - SIGINT; profile -U -p \$PID > spin.profile)& wait \$PID;"; sudo kill
> -SIGINT `pgrep -x profile`; sleep 1; cat spin.profile;
> sleep 1
> sudo make clean
>
> #~>./test_profile.sh
>
> Here, in my server, spin.profile cannot resolve user-level symbols (i.e.
> symbols in spin.cc). It only shows userland symbol names as "[unknown]".
>
> I am using Ubuntu 16.04.3 LTS with Linux Kernel ver. 4.10.0-28-generic. I've
> tried both installing by apt-get or building from source (latest pull from
> github). the results are the same: user-land functions names cannot be
> resolved.
>
> 2) What I've tried/found:
>
> - perf_event works well under my environment in resolving both the kernel
> and userspace symbols.
> - bcc/test/python/test_
debuginfo.py pass all tests. Showing that build-id
> and debug-link both methods work in bcc.
> - [MAJOR PROBLEM] I found the failed statement:
> src/cc/bcc_proc.c:78:
> int bcc_procutils_each_module(int pid, bcc_procutils_modulecb callback, void
> *payload) {
>
> ...
> // always fails, with errno = 2
> procmap = fopen(procmap_filename, "r");
> ...
>
> }
>
> - Afterwards, I've written a similar little c++ program to read
> "/proc/pid/maps", and it can open/read the proc map file successfully.
> Besides, I can also cat the proc map file in the shell, the file can be read
> successfully too.
>
> the little testing c++ program to open and read the procmap file is as
> follows (very similar to bcc_procutils_each_module):
>
> #~> cat read-proc-map.cc
> #include <iostream>
> #include <cstring>
> #include <stdio.h>
> #include <errno.h>
>
> int main(int argc, char*argv[]) {
> char procmap_filename[128];
> FILE *procmap;
> int ret;
>
> printf("%d\n", argc);
>
> if (argc != 2) return -1;
>
> printf("mytest\n");
>
> snprintf(procmap_filename, sizeof(procmap_filename),
> "/proc/%s/maps", argv[1]);
> procmap = fopen(procmap_filename, "r");
>
> printf("mytest: fopen <%s>\n", procmap_filename);
>
> if (!procmap) {
> printf("mytest: ... failed errno=%d\n", errno);
> return -1;
> }
>
> printf("mytest: ... success <%s>\n", procmap_filename);
>
>
> do {
> char endline[4096];
> char perm[8], dev[8];
> long long begin, end, size, inode;
>
> ret = fscanf(procmap, "%llx-%llx %s %llx %s %lld", &begin, &end, perm,
> &size, dev, &inode);
>
> if (!fgets(endline, sizeof(endline), procmap))
> break;
>
> if (ret == 6) {
> char *mapname = endline;
> char *newline = strchr(endline, '\n');
>
> if (newline)
> newline[0] = '\0';
>
> while (isspace(mapname[0])) mapname++;
>
> printf("%s, %llx, %llx\n", mapname, begin, end);
> }
> } while (ret && ret != EOF);
>
> fclose(procmap);
> printf("mytest: fclosed %s\n", procmap_filename);
> return 0;
> }
>
> ====
>
