libutil: Introduce util_udev

Move code to read udev files from zdev into a utility library for use by
other tools.

Acked-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

libutil/util_udev.c

@@ -0,0 +1,362 @@
+/*
+ * util - Utility function library
+ *
+ * UDEV helper functions
+ *
+ * Copyright IBM Corp. 2022
+ *
+ * s390-tools is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "lib/util_exit_code.h"
+#include "lib/util_file.h"
+#include "lib/util_libc.h"
+#include "lib/util_list.h"
+#include "lib/util_path.h"
+#include "lib/util_udev.h"
+
+/* Create a newly allocated udev entry. */
+static struct util_udev_entry_node *util_udev_entry_node_new(const char *key,
+							     const char *op,
+							     const char *value)
+{
+	struct util_udev_entry_node *entry;
+
+	entry = util_zalloc(sizeof(struct util_udev_entry_node));
+	entry->key = util_strdup(key);
+	entry->op = util_strdup(op);
+	entry->value = util_strdup(value);
+
+	return entry;
+}
+
+/* Release resources associated with udev entry. */
+static void util_udev_entry_node_free(struct util_udev_entry_node *entry)
+{
+	if (!entry)
+		return;
+	free(entry->key);
+	free(entry->op);
+	free(entry->value);
+	free(entry);
+}
+
+/* Create a newly allocated udev line. */
+static struct util_udev_line_node *util_udev_line_node_new(void)
+{
+	struct util_udev_line_node *line;
+
+	line = util_zalloc(sizeof(struct util_udev_line_node));
+	util_list_init(&line->entries, struct util_udev_entry_node, node);
+
+	return line;
+}
+
+/* Release resources associated with udev line. */
+static void util_udev_line_node_free(struct util_udev_line_node *line)
+{
+	struct util_udev_entry_node *e, *n;
+
+	if (!line)
+		return;
+	util_list_iterate_safe(&line->entries, e, n) {
+		util_list_remove(&line->entries, e);
+		util_udev_entry_node_free(e);
+	}
+	free(line->line);
+	free(line);
+}
+
+/* Create a newly allocated udev file. */
+static struct util_udev_file *util_udev_file_new(void)
+{
+	struct util_udev_file *file;
+
+	file = util_zalloc(sizeof(struct util_udev_file));
+	util_list_init(&file->lines, struct util_udev_line_node, node);
+
+	return file;
+}
+
+/**
+ * Release resources associated with udev file.
+ *
+ * @param[in, out] file       Udev file structure to be freed
+ */
+void util_udev_free_file(struct util_udev_file *file)
+{
+	struct util_udev_line_node *l, *n;
+
+	if (!file)
+		return;
+	util_list_iterate_safe(&file->lines, l, n) {
+		util_list_remove(&file->lines, l);
+		util_udev_line_node_free(l);
+	}
+	free(file);
+}
+
+/**
+ * Print the contents of a udev file to stdout. Used for debugging.
+ *
+ * @param[in]      file       Udev file structure to print
+ */
+void util_udev_file_print(struct util_udev_file *file)
+{
+	struct util_udev_line_node *l;
+	struct util_udev_entry_node *e;
+
+	printf("util_udev_file at %p\n", (void *) file);
+	if (!file)
+		return;
+	util_list_iterate(&file->lines, l) {
+		printf("  util_udev_line_node at %p\n", (void *) l);
+		printf("    line='%s'\n", l->line);
+		util_list_iterate(&l->entries, e) {
+			printf("    util_udev_entry at %p\n", (void *) e);
+			printf("      '%s' '%s' '%s'\n", e->key, e->op,
+			       e->value);
+		}
+	}
+}
+
+static void skip_whitespace(const char **s_ptr)
+{
+	const char *s = *s_ptr;
+
+	while (*s && isspace(*s))
+		s++;
+
+	*s_ptr = s;
+}
+
+static char *parse_key(const char **s_ptr)
+{
+	const char *s, *e;
+	char *key;
+
+	s = *s_ptr;
+	/* Parse \w+(\{[^\}]*\})? */
+	e = s;
+	while (*e && (isalnum(*e) || *e == '_'))
+		e++;
+	if (*e == '{') {
+		while (*e && *e != '}')
+			e++;
+		if (*e == '}')
+			e++;
+	}
+
+	if (e == s)
+		return NULL;
+
+	/* s points to key start, e to character after key end. */
+	key = util_zalloc(e - s + 1);
+	memcpy(key, s, e - s);
+
+	*s_ptr = e;
+
+	return key;
+}
+
+static char *parse_op(const char **s_ptr)
+{
+	const char *ops[] = { "==", "!=", "=", "+=", ":=", NULL };
+	const char *entry;
+	size_t len;
+	int i;
+
+	entry = *s_ptr;
+	for (i = 0; ops[i]; i++) {
+		len = strlen(ops[i]);
+		if (strncmp(entry, ops[i], len) == 0) {
+			*s_ptr += len;
+			return util_strdup(ops[i]);
+		}
+	}
+
+	return NULL;
+}
+
+static char *parse_value(const char **s_ptr)
+{
+	const char *s, *e;
+	char *value;
+
+	/* Parse: ^\s*(.*)\s*$ */
+	s = *s_ptr;
+	skip_whitespace(&s);
+	e = s;
+	while (*e)
+		e++;
+	e--;
+	while (e > s && isspace(*e))
+		e--;
+	e++;
+
+	*s_ptr = e;
+
+	/* Remove quotes. */
+	if ((*s == '"' && *(e - 1) == '"') ||
+	    (*s == '\'' && *(e - 1) == '\'')) {
+		s++;
+		e--;
+	}
+
+	/* s points to value start, e to character after value end. */
+	value = util_zalloc(e - s + 1);
+	memcpy(value, s, e - s);
+
+	return value;
+}
+
+static bool parse_util_udev_entry(struct util_udev_line_node *line,
+				  const char *entry)
+{
+	char *key = NULL, *op = NULL, *value = NULL;
+	struct util_udev_entry_node *e;
+	bool rc = false;
+
+	/* Parse: ^\s*(\w+)\s*(==|!=|=|\+=|:=)\s*"?([^"]*)"\s*$ */
+
+	/* Parse key. */
+	skip_whitespace(&entry);
+	key = parse_key(&entry);
+	if (!key)
+		goto out;
+
+	/* Parse operator. */
+	skip_whitespace(&entry);
+	op = parse_op(&entry);
+	if (!op)
+		goto out;
+
+	/* Parse value. */
+	skip_whitespace(&entry);
+	value = parse_value(&entry);
+	if (!value)
+		goto out;
+	skip_whitespace(&entry);
+
+	/* Check for unrecognized characters at end of entry. */
+	if (*entry != 0)
+		goto out;
+
+	/* Add entry to list. */
+	e = util_udev_entry_node_new(key, op, value);
+	util_list_add_tail(&line->entries, e);
+	rc = true;
+
+out:
+	free(key);
+	free(op);
+	free(value);
+
+	return rc;
+}
+
+static void replace_unquoted(char *s, char from, char to)
+{
+	char quoted = 0;
+
+	for (; *s; s++) {
+		if (quoted) {
+			/* Skip until quote end is found. */
+			if (*s == quoted)
+				quoted = 0;
+			continue;
+		}
+		if (*s == '"' || *s == '\'') {
+			quoted = *s;
+			continue;
+		}
+		if (*s == from)
+			*s = to;
+	}
+}
+
+static bool parse_util_udev_line(struct util_udev_file *file, const char *line)
+{
+	char *copy, *curr, *next;
+	struct util_udev_line_node *l;
+	int i;
+	bool result = true;
+
+	l = util_udev_line_node_new();
+	l->line = util_strdup(line);
+
+	/* Check for empty lines and comment lines. */
+	for (i = 0; line[i] && isspace(line[i]); i++);
+	if (line[i] == 0 || line[i] == '#')
+		goto ok;
+
+	/* Parse each comma-separated entry. */
+	copy = util_strdup(line);
+
+	/* A hack to differentiate between quoted and unquoted commas. */
+	replace_unquoted(copy, ',', 1);
+
+	next = copy;
+	while ((curr = strsep(&next, "\1"))) {
+		if (!parse_util_udev_entry(l, curr)) {
+			result = false;
+			break;
+		}
+	}
+	free(copy);
+
+ok:
+	if (result)
+		util_list_add_tail(&file->lines, l);
+	else
+		util_udev_line_node_free(l);
+
+	return result;
+}
+
+/**
+ * Create a new util_udev_file structure and read the contents of a specified
+ * udev file into that structure.
+ *
+ * @param[in]      path       Path to the udev file that will be read in
+ * @param[in, out] file_ptr   A buffer to store resulting udev file structure
+ *
+ * @retval         0                       Udev file read successfully
+ * @retval         UTIL_EXIT_RUNTIME_ERROR Error reading the udev file
+ */
+util_exit_code_t util_udev_read_file(const char *path,
+				     struct util_udev_file **file_ptr)
+{
+	char *text, *curr, *next;
+	struct util_udev_file *file;
+	int once = 0;
+
+	text = util_file_read_text_file(path, 0);
+	if (!text)
+		return UTIL_EXIT_RUNTIME_ERROR;
+	file = util_udev_file_new();
+
+	/* Iterate over each line. */
+	next = text;
+	while ((curr = strsep(&next, "\n"))) {
+		if (parse_util_udev_line(file, curr))
+			continue;
+		if (!once) {
+			once = 1;
+			fprintf(stderr, "Unrecognized udev rule in %s:\n",
+				path);
+		}
+		fprintf(stderr, "%s\n", curr);
+	}
+
+	free(text);
+	*file_ptr = file;
+
+	return UTIL_EXIT_OK;
+}