samples/bpf: move common-purpose trace functions to selftests

There is no functionality change in this patch. The common-purpose
trace functions, including perf_event polling and ksym lookup,
are moved from trace_output_user.c and bpf_load.c to
selftests/bpf/trace_helpers.c so that these function can
be reused later in selftests.

Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

samples/bpf/bpf_load.c

@@ -648,66 +648,3 @@ void read_trace_pipe(void)
 		}
 	}
 }
-
-#define MAX_SYMS 300000
-static struct ksym syms[MAX_SYMS];
-static int sym_cnt;
-
-static int ksym_cmp(const void *p1, const void *p2)
-{
-	return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
-}
-
-int load_kallsyms(void)
-{
-	FILE *f = fopen("/proc/kallsyms", "r");
-	char func[256], buf[256];
-	char symbol;
-	void *addr;
-	int i = 0;
-
-	if (!f)
-		return -ENOENT;
-
-	while (!feof(f)) {
-		if (!fgets(buf, sizeof(buf), f))
-			break;
-		if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
-			break;
-		if (!addr)
-			continue;
-		syms[i].addr = (long) addr;
-		syms[i].name = strdup(func);
-		i++;
-	}
-	sym_cnt = i;
-	qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
-	return 0;
-}
-
-struct ksym *ksym_search(long key)
-{
-	int start = 0, end = sym_cnt;
-	int result;
-
-	while (start < end) {
-		size_t mid = start + (end - start) / 2;
-
-		result = key - syms[mid].addr;
-		if (result < 0)
-			end = mid;
-		else if (result > 0)
-			start = mid + 1;
-		else
-			return &syms[mid];
-	}
-
-	if (start >= 1 && syms[start - 1].addr < key &&
-	    key < syms[start].addr)
-		/* valid ksym */
-		return &syms[start - 1];
-
-	/* out of range. return _stext */
-	return &syms[0];
-}
-