xref: /linux/lib/parser.c (revision f3d9478b2ce468c3115b02ecae7e975990697f15)
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/module.h>
10 #include <linux/parser.h>
11 #include <linux/slab.h>
12 #include <linux/string.h>
13 
14 /**
15  * match_one: - Determines if a string matches a simple pattern
16  * @s: the string to examine for presense of the pattern
17  * @p: the string containing the pattern
18  * @args: array of %MAX_OPT_ARGS &substring_t elements. Used to return match
19  * locations.
20  *
21  * Description: Determines if the pattern @p is present in string @s. Can only
22  * match extremely simple token=arg style patterns. If the pattern is found,
23  * the location(s) of the arguments will be returned in the @args array.
24  */
25 static int match_one(char *s, char *p, substring_t args[])
26 {
27 	char *meta;
28 	int argc = 0;
29 
30 	if (!p)
31 		return 1;
32 
33 	while(1) {
34 		int len = -1;
35 		meta = strchr(p, '%');
36 		if (!meta)
37 			return strcmp(p, s) == 0;
38 
39 		if (strncmp(p, s, meta-p))
40 			return 0;
41 
42 		s += meta - p;
43 		p = meta + 1;
44 
45 		if (isdigit(*p))
46 			len = simple_strtoul(p, &p, 10);
47 		else if (*p == '%') {
48 			if (*s++ != '%')
49 				return 0;
50 			p++;
51 			continue;
52 		}
53 
54 		if (argc >= MAX_OPT_ARGS)
55 			return 0;
56 
57 		args[argc].from = s;
58 		switch (*p++) {
59 		case 's':
60 			if (strlen(s) == 0)
61 				return 0;
62 			else if (len == -1 || len > strlen(s))
63 				len = strlen(s);
64 			args[argc].to = s + len;
65 			break;
66 		case 'd':
67 			simple_strtol(s, &args[argc].to, 0);
68 			goto num;
69 		case 'u':
70 			simple_strtoul(s, &args[argc].to, 0);
71 			goto num;
72 		case 'o':
73 			simple_strtoul(s, &args[argc].to, 8);
74 			goto num;
75 		case 'x':
76 			simple_strtoul(s, &args[argc].to, 16);
77 		num:
78 			if (args[argc].to == args[argc].from)
79 				return 0;
80 			break;
81 		default:
82 			return 0;
83 		}
84 		s = args[argc].to;
85 		argc++;
86 	}
87 }
88 
89 /**
90  * match_token: - Find a token (and optional args) in a string
91  * @s: the string to examine for token/argument pairs
92  * @table: match_table_t describing the set of allowed option tokens and the
93  * arguments that may be associated with them. Must be terminated with a
94  * &struct match_token whose pattern is set to the NULL pointer.
95  * @args: array of %MAX_OPT_ARGS &substring_t elements. Used to return match
96  * locations.
97  *
98  * Description: Detects which if any of a set of token strings has been passed
99  * to it. Tokens can include up to MAX_OPT_ARGS instances of basic c-style
100  * format identifiers which will be taken into account when matching the
101  * tokens, and whose locations will be returned in the @args array.
102  */
103 int match_token(char *s, match_table_t table, substring_t args[])
104 {
105 	struct match_token *p;
106 
107 	for (p = table; !match_one(s, p->pattern, args) ; p++)
108 		;
109 
110 	return p->token;
111 }
112 
113 /**
114  * match_number: scan a number in the given base from a substring_t
115  * @s: substring to be scanned
116  * @result: resulting integer on success
117  * @base: base to use when converting string
118  *
119  * Description: Given a &substring_t and a base, attempts to parse the substring
120  * as a number in that base. On success, sets @result to the integer represented
121  * by the string and returns 0. Returns either -ENOMEM or -EINVAL on failure.
122  */
123 static int match_number(substring_t *s, int *result, int base)
124 {
125 	char *endp;
126 	char *buf;
127 	int ret;
128 
129 	buf = kmalloc(s->to - s->from + 1, GFP_KERNEL);
130 	if (!buf)
131 		return -ENOMEM;
132 	memcpy(buf, s->from, s->to - s->from);
133 	buf[s->to - s->from] = '\0';
134 	*result = simple_strtol(buf, &endp, base);
135 	ret = 0;
136 	if (endp == buf)
137 		ret = -EINVAL;
138 	kfree(buf);
139 	return ret;
140 }
141 
142 /**
143  * match_int: - scan a decimal representation of an integer from a substring_t
144  * @s: substring_t to be scanned
145  * @result: resulting integer on success
146  *
147  * Description: Attempts to parse the &substring_t @s as a decimal integer. On
148  * success, sets @result to the integer represented by the string and returns 0.
149  * Returns either -ENOMEM or -EINVAL on failure.
150  */
151 int match_int(substring_t *s, int *result)
152 {
153 	return match_number(s, result, 0);
154 }
155 
156 /**
157  * match_octal: - scan an octal representation of an integer from a substring_t
158  * @s: substring_t to be scanned
159  * @result: resulting integer on success
160  *
161  * Description: Attempts to parse the &substring_t @s as an octal integer. On
162  * success, sets @result to the integer represented by the string and returns
163  * 0. Returns either -ENOMEM or -EINVAL on failure.
164  */
165 int match_octal(substring_t *s, int *result)
166 {
167 	return match_number(s, result, 8);
168 }
169 
170 /**
171  * match_hex: - scan a hex representation of an integer from a substring_t
172  * @s: substring_t to be scanned
173  * @result: resulting integer on success
174  *
175  * Description: Attempts to parse the &substring_t @s as a hexadecimal integer.
176  * On success, sets @result to the integer represented by the string and
177  * returns 0. Returns either -ENOMEM or -EINVAL on failure.
178  */
179 int match_hex(substring_t *s, int *result)
180 {
181 	return match_number(s, result, 16);
182 }
183 
184 /**
185  * match_strcpy: - copies the characters from a substring_t to a string
186  * @to: string to copy characters to.
187  * @s: &substring_t to copy
188  *
189  * Description: Copies the set of characters represented by the given
190  * &substring_t @s to the c-style string @to. Caller guarantees that @to is
191  * large enough to hold the characters of @s.
192  */
193 void match_strcpy(char *to, substring_t *s)
194 {
195 	memcpy(to, s->from, s->to - s->from);
196 	to[s->to - s->from] = '\0';
197 }
198 
199 /**
200  * match_strdup: - allocate a new string with the contents of a substring_t
201  * @s: &substring_t to copy
202  *
203  * Description: Allocates and returns a string filled with the contents of
204  * the &substring_t @s. The caller is responsible for freeing the returned
205  * string with kfree().
206  */
207 char *match_strdup(substring_t *s)
208 {
209 	char *p = kmalloc(s->to - s->from + 1, GFP_KERNEL);
210 	if (p)
211 		match_strcpy(p, s);
212 	return p;
213 }
214 
215 EXPORT_SYMBOL(match_token);
216 EXPORT_SYMBOL(match_int);
217 EXPORT_SYMBOL(match_octal);
218 EXPORT_SYMBOL(match_hex);
219 EXPORT_SYMBOL(match_strcpy);
220 EXPORT_SYMBOL(match_strdup);
221