util, pidns: generalise get_id_list

The parsing code implemented in it can be easily utilised for reading
other /proc/pid/status fields (Uid/Gid, for example), so let's move it
to util.c and make more generic.

* src/defs.h (proc_status_get_id_list): New declaration.
* src/util.c (proc_status_get_id_list): New function.
* src/pidns.c (get_id_list): Implement as a proc_status_get_id_list
wrapper.

3 files changed, 88 insertions, 57 deletions

diff --git a/src/defs.h b/src/defs.h
index 1121ad571..b8146469d 100644
--- a/src/defs.h
+++ b/src/defs.h
@@ -1157,6 +1157,33 @@ printfd(struct tcb *tcp, int fd)
 }
 
 /**
+ * Helper function, converts pid to string, or to "self" for pid == 0.
+ * Uses static buffer for operation.
+ */
+extern const char *pid_to_str(pid_t pid);
+
+/**
+ * Get list of IDs present in a proc status record. IDs are placed in the array
+ * in the order they are stored in /proc.
+ *
+ * @param proc_pid    PID (as present in /proc) to get information for.
+ * @param id_buf      Pointer to buffer where parsed IDs are stored.
+ *                    Can be NULL.
+ * @param id_buf_size Number of items id_buf can store.  If there are more IDs
+ *                    than id_buf can store, the excess IDs are not stored
+ *                    but still counted.
+ * @param str         (Prefix) string IDs from which are to be read.
+ * @param str_size    Size of the prefix string.  Can be 0, in this case str
+ *                    has to be '\0'-terminated in order to be able to obtain
+ *                    its length.
+ * @return            Number of items read (even if they are not written).
+ *                    0 indicates error.
+ */
+extern size_t proc_status_get_id_list(int proc_pid,
+				      int *id_buf, size_t id_buf_size,
+				      const char *str, size_t str_size);
+
+/**
  * Print file descriptor fd owned by process with ID pid (from the PID NS
  * of the tracee).
  */
diff --git a/src/pidns.c b/src/pidns.c
index d3ebd0535..9ec72a47d 100644
--- a/src/pidns.c
+++ b/src/pidns.c
@@ -139,21 +139,6 @@ get_cached_proc_pid(unsigned int ns, int ns_pid, enum pid_type type)
 }
 
 /**
- * Helper function, converts pid to string, or to "self" for pid == 0.
- * Uses static buffer for operation.
- */
-static const char *
-pid_to_str(pid_t pid)
-{
-	if (!pid)
-		return "self";
-
-	static char buf[sizeof("-2147483648")];
-	xsprintf(buf, "%d", pid);
-	return buf;
-}
-
-/**
  * Returns a list of PID NS IDs for the specified PID.
  *
  * @param proc_pid PID (as present in /proc) to get information for.
@@ -226,48 +211,8 @@ get_ns_hierarchy(int proc_pid, unsigned int *ns_buf, size_t ns_buf_size)
 static size_t
 get_id_list(int proc_pid, int *id_buf, enum pid_type type)
 {
-	const char *ns_str = id_strs[type].str;
-	size_t ns_str_size = id_strs[type].size;
-
-	size_t n = 0;
-
-	char status_path[PATH_MAX + 1];
-	xsprintf(status_path, "/proc/%s/status", pid_to_str(proc_pid));
-	FILE *f = fopen_stream(status_path, "r");
-	if (!f)
-		return 0;
-
-	char *line = NULL;
-	size_t linesize = 0;
-	char *p = NULL;
-
-	while (getline(&line, &linesize, f) > 0) {
-		if (strncmp(line, ns_str, ns_str_size) == 0) {
-			p = line + ns_str_size;
-			break;
-		}
-	}
-
-	while (p) {
-		errno = 0;
-		long id = strtol(p, NULL, 10);
-
-		if (id < 0 || id > INT_MAX || errno) {
-			perror_func_msg("converting pid (%ld) to int", id);
-			break;
-		}
-
-		if (id_buf)
-			id_buf[n] = (int) id;
-
-		n++;
-		strsep(&p, "\t");
-	}
-
-	free(line);
-	fclose(f);
-
-	return n;
+	return proc_status_get_id_list(proc_pid, id_buf, MAX_NS_DEPTH,
+				       id_strs[type].str, id_strs[type].size);
 }
 
 /**
diff --git a/src/util.c b/src/util.c
index a22d4095f..d438150ee 100644
--- a/src/util.c
+++ b/src/util.c
@@ -686,6 +686,65 @@ printfd_pid_tracee_ns(struct tcb *tcp, pid_t pid, int fd)
 	printfd_pid(tcp, strace_pid, fd);
 }
 
+const char *
+pid_to_str(pid_t pid)
+{
+	if (!pid)
+		return "self";
+
+	static char buf[sizeof("-2147483648")];
+	xsprintf(buf, "%d", pid);
+	return buf;
+}
+
+size_t
+proc_status_get_id_list(int proc_pid, int *id_buf, size_t id_buf_size,
+			const char *str, size_t str_size)
+{
+	size_t n = 0;
+
+	if (!str_size)
+		str_size = strlen(str);
+
+	char status_path[PATH_MAX + 1];
+	xsprintf(status_path, "/proc/%s/status", pid_to_str(proc_pid));
+	FILE *f = fopen_stream(status_path, "r");
+	if (!f)
+		return 0;
+
+	char *line = NULL;
+	size_t linesize = 0;
+	char *p = NULL;
+
+	while (getline(&line, &linesize, f) > 0) {
+		if (strncmp(line, str, str_size) == 0) {
+			p = line + str_size;
+			break;
+		}
+	}
+
+	while (p) {
+		errno = 0;
+		long id = strtol(p, NULL, 10);
+
+		if (id < 0 || id > INT_MAX || errno) {
+			debug_func_perror_msg("converting \"%s\" to int", p);
+			break;
+		}
+
+		if (id_buf && n < id_buf_size)
+			id_buf[n] = (int) id;
+
+		n++;
+		strsep(&p, "\t");
+	}
+
+	free(line);
+	fclose(f);
+
+	return n;
+}
+
 /*
  * Quote string `instr' of length `size'
  * Write up to (3 + `size' * 4) bytes to `outstr' buffer.