1/*
  2 * lib/parser.c - simple parser for mount, etc. options.
  3 *
  4 * This source code is licensed under the GNU General Public License,
  5 * Version 2.  See the file COPYING for more details.
  6 */
  7
  8#include <linux/ctype.h>
  9#include <linux/types.h>
 10#include <linux/export.h>
 11#include <linux/parser.h>
 12#include <linux/slab.h>
 13#include <linux/string.h>
 14
 15/**
 16 * match_one: - Determines if a string matches a simple pattern
 17 * @s: the string to examine for presence of the pattern
 18 * @p: the string containing the pattern
 19 * @args: array of %MAX_OPT_ARGS &substring_t elements. Used to return match
 20 * locations.
 21 *
 22 * Description: Determines if the pattern @p is present in string @s. Can only
 23 * match extremely simple token=arg style patterns. If the pattern is found,
 24 * the location(s) of the arguments will be returned in the @args array.
 25 */
 26static int match_one(char *s, const char *p, substring_t args[])
 27{
 28	char *meta;
 29	int argc = 0;
 30
 31	if (!p)
 32		return 1;
 33
 34	while(1) {
 35		int len = -1;
 36		meta = strchr(p, '%');
 37		if (!meta)
 38			return strcmp(p, s) == 0;
 39
 40		if (strncmp(p, s, meta-p))
 41			return 0;
 42
 43		s += meta - p;
 44		p = meta + 1;
 45
 46		if (isdigit(*p))
 47			len = simple_strtoul(p, (char **) &p, 10);
 48		else if (*p == '%') {
 49			if (*s++ != '%')
 50				return 0;
 51			p++;
 52			continue;
 53		}
 54
 55		if (argc >= MAX_OPT_ARGS)
 56			return 0;
 57
 58		args[argc].from = s;
 59		switch (*p++) {
 60		case 's': {
 61			size_t str_len = strlen(s);
 62
 63			if (str_len == 0)
 64				return 0;
 65			if (len == -1 || len > str_len)
 66				len = str_len;
 67			args[argc].to = s + len;
 68			break;
 69		}
 70		case 'd':
 71			simple_strtol(s, &args[argc].to, 0);
 72			goto num;
 73		case 'u':
 74			simple_strtoul(s, &args[argc].to, 0);
 75			goto num;
 76		case 'o':
 77			simple_strtoul(s, &args[argc].to, 8);
 78			goto num;
 79		case 'x':
 80			simple_strtoul(s, &args[argc].to, 16);
 81		num:
 82			if (args[argc].to == args[argc].from)
 83				return 0;
 84			break;
 85		default:
 86			return 0;
 87		}
 88		s = args[argc].to;
 89		argc++;
 90	}
 91}
 92
 93/**
 94 * match_token: - Find a token (and optional args) in a string
 95 * @s: the string to examine for token/argument pairs
 96 * @table: match_table_t describing the set of allowed option tokens and the
 97 * arguments that may be associated with them. Must be terminated with a
 98 * &struct match_token whose pattern is set to the NULL pointer.
 99 * @args: array of %MAX_OPT_ARGS &substring_t elements. Used to return match
100 * locations.
101 *
102 * Description: Detects which if any of a set of token strings has been passed
103 * to it. Tokens can include up to MAX_OPT_ARGS instances of basic c-style
104 * format identifiers which will be taken into account when matching the
105 * tokens, and whose locations will be returned in the @args array.
106 */
107int match_token(char *s, const match_table_t table, substring_t args[])
108{
109	const struct match_token *p;
110
111	for (p = table; !match_one(s, p->pattern, args) ; p++)
112		;
113
114	return p->token;
115}
116
117/**
118 * match_number: scan a number in the given base from a substring_t
119 * @s: substring to be scanned
120 * @result: resulting integer on success
121 * @base: base to use when converting string
122 *
123 * Description: Given a &substring_t and a base, attempts to parse the substring
124 * as a number in that base. On success, sets @result to the integer represented
125 * by the string and returns 0. Returns either -ENOMEM or -EINVAL on failure.
126 */
127static int match_number(substring_t *s, int *result, int base)
128{
129	char *endp;
130	char *buf;
131	int ret;
132	size_t len = s->to - s->from;
133
134	buf = kmalloc(len + 1, GFP_KERNEL);
135	if (!buf)
136		return -ENOMEM;
137	memcpy(buf, s->from, len);
138	buf[len] = '\0';
139	*result = simple_strtol(buf, &endp, base);
140	ret = 0;
141	if (endp == buf)
142		ret = -EINVAL;
143	kfree(buf);
144	return ret;
145}
146
147/**
148 * match_int: - scan a decimal representation of an integer from a substring_t
149 * @s: substring_t to be scanned
150 * @result: resulting integer on success
151 *
152 * Description: Attempts to parse the &substring_t @s as a decimal integer. On
153 * success, sets @result to the integer represented by the string and returns 0.
154 * Returns either -ENOMEM or -EINVAL on failure.
155 */
156int match_int(substring_t *s, int *result)
157{
158	return match_number(s, result, 0);
159}
160
161/**
162 * match_octal: - scan an octal representation of an integer from a substring_t
163 * @s: substring_t to be scanned
164 * @result: resulting integer on success
165 *
166 * Description: Attempts to parse the &substring_t @s as an octal integer. On
167 * success, sets @result to the integer represented by the string and returns
168 * 0. Returns either -ENOMEM or -EINVAL on failure.
169 */
170int match_octal(substring_t *s, int *result)
171{
172	return match_number(s, result, 8);
173}
174
175/**
176 * match_hex: - scan a hex representation of an integer from a substring_t
177 * @s: substring_t to be scanned
178 * @result: resulting integer on success
179 *
180 * Description: Attempts to parse the &substring_t @s as a hexadecimal integer.
181 * On success, sets @result to the integer represented by the string and
182 * returns 0. Returns either -ENOMEM or -EINVAL on failure.
183 */
184int match_hex(substring_t *s, int *result)
185{
186	return match_number(s, result, 16);
187}
188
189/**
190 * match_strlcpy: - Copy the characters from a substring_t to a sized buffer
191 * @dest: where to copy to
192 * @src: &substring_t to copy
193 * @size: size of destination buffer
194 *
195 * Description: Copy the characters in &substring_t @src to the
196 * c-style string @dest.  Copy no more than @size - 1 characters, plus
197 * the terminating NUL.  Return length of @src.
198 */
199size_t match_strlcpy(char *dest, const substring_t *src, size_t size)
200{
201	size_t ret = src->to - src->from;
202
203	if (size) {
204		size_t len = ret >= size ? size - 1 : ret;
205		memcpy(dest, src->from, len);
206		dest[len] = '\0';
207	}
208	return ret;
209}
210
211/**
212 * match_strdup: - allocate a new string with the contents of a substring_t
213 * @s: &substring_t to copy
214 *
215 * Description: Allocates and returns a string filled with the contents of
216 * the &substring_t @s. The caller is responsible for freeing the returned
217 * string with kfree().
218 */
219char *match_strdup(const substring_t *s)
220{
221	size_t sz = s->to - s->from + 1;
222	char *p = kmalloc(sz, GFP_KERNEL);
223	if (p)
224		match_strlcpy(p, s, sz);
225	return p;
226}
227
228EXPORT_SYMBOL(match_token);
229EXPORT_SYMBOL(match_int);
230EXPORT_SYMBOL(match_octal);
231EXPORT_SYMBOL(match_hex);
232EXPORT_SYMBOL(match_strlcpy);
233EXPORT_SYMBOL(match_strdup);