xref: /linux/arch/x86/boot/cmdline.c (revision 16a4baa6) 
1 /* -*- linux-c -*- ------------------------------------------------------- *
2  *
3  *   Copyright (C) 1991, 1992 Linus Torvalds
4  *   Copyright 2007 rPath, Inc. - All Rights Reserved
5  *
6  *   This file is part of the Linux kernel, and is made available under
7  *   the terms of the GNU General Public License version 2.
8  *
9  * ----------------------------------------------------------------------- */
10 
11 /*
12  * Simple command-line parser for early boot.
13  */
14 
15 #include "boot.h"
16 
17 static inline int myisspace(u8 c)
18 {
19 	return c <= ' ';	/* Close enough approximation */
20 }
21 
22 /*
23  * Find a non-boolean option, that is, "option=argument".  In accordance
24  * with standard Linux practice, if this option is repeated, this returns
25  * the last instance on the command line.
26  *
27  * Returns the length of the argument (regardless of if it was
28  * truncated to fit in the buffer), or -1 on not found.
29  */
30 int __cmdline_find_option(u32 cmdline_ptr, const char *option, char *buffer, int bufsize)
31 {
32 	addr_t cptr;
33 	char c;
34 	int len = -1;
35 	const char *opptr = NULL;
36 	char *bufptr = buffer;
37 	enum {
38 		st_wordstart,	/* Start of word/after whitespace */
39 		st_wordcmp,	/* Comparing this word */
40 		st_wordskip,	/* Miscompare, skip */
41 		st_bufcpy	/* Copying this to buffer */
42 	} state = st_wordstart;
43 
44 	if (!cmdline_ptr)
45 		return -1;      /* No command line */
46 
47 	cptr = cmdline_ptr & 0xf;
48 	set_fs(cmdline_ptr >> 4);
49 
50 	while (cptr < 0x10000 && (c = rdfs8(cptr++))) {
51 		switch (state) {
52 		case st_wordstart:
53 			if (myisspace(c))
54 				break;
55 
56 			/* else */
57 			state = st_wordcmp;
58 			opptr = option;
59 			/* fall through */
60 
61 		case st_wordcmp:
62 			if (c == '=' && !*opptr) {
63 				len = 0;
64 				bufptr = buffer;
65 				state = st_bufcpy;
66 			} else if (myisspace(c)) {
67 				state = st_wordstart;
68 			} else if (c != *opptr++) {
69 				state = st_wordskip;
70 			}
71 			break;
72 
73 		case st_wordskip:
74 			if (myisspace(c))
75 				state = st_wordstart;
76 			break;
77 
78 		case st_bufcpy:
79 			if (myisspace(c)) {
80 				state = st_wordstart;
81 			} else {
82 				if (len < bufsize-1)
83 					*bufptr++ = c;
84 				len++;
85 			}
86 			break;
87 		}
88 	}
89 
90 	if (bufsize)
91 		*bufptr = '\0';
92 
93 	return len;
94 }
95 
96 /*
97  * Find a boolean option (like quiet,noapic,nosmp....)
98  *
99  * Returns the position of that option (starts counting with 1)
100  * or 0 on not found
101  */
102 int __cmdline_find_option_bool(u32 cmdline_ptr, const char *option)
103 {
104 	addr_t cptr;
105 	char c;
106 	int pos = 0, wstart = 0;
107 	const char *opptr = NULL;
108 	enum {
109 		st_wordstart,	/* Start of word/after whitespace */
110 		st_wordcmp,	/* Comparing this word */
111 		st_wordskip,	/* Miscompare, skip */
112 	} state = st_wordstart;
113 
114 	if (!cmdline_ptr)
115 		return -1;      /* No command line */
116 
117 	cptr = cmdline_ptr & 0xf;
118 	set_fs(cmdline_ptr >> 4);
119 
120 	while (cptr < 0x10000) {
121 		c = rdfs8(cptr++);
122 		pos++;
123 
124 		switch (state) {
125 		case st_wordstart:
126 			if (!c)
127 				return 0;
128 			else if (myisspace(c))
129 				break;
130 
131 			state = st_wordcmp;
132 			opptr = option;
133 			wstart = pos;
134 			/* fall through */
135 
136 		case st_wordcmp:
137 			if (!*opptr)
138 				if (!c || myisspace(c))
139 					return wstart;
140 				else
141 					state = st_wordskip;
142 			else if (!c)
143 				return 0;
144 			else if (c != *opptr++)
145 				state = st_wordskip;
146 			break;
147 
148 		case st_wordskip:
149 			if (!c)
150 				return 0;
151 			else if (myisspace(c))
152 				state = st_wordstart;
153 			break;
154 		}
155 	}
156 
157 	return 0;	/* Buffer overrun */
158 }
159