xref: /openbmc/linux/arch/x86/boot/cmdline.c (revision a1e58bbd) 
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  * arch/i386/boot/cmdline.c
13  *
14  * Simple command-line parser for early boot.
15  */
16 
17 #include "boot.h"
18 
19 static inline int myisspace(u8 c)
20 {
21 	return c <= ' ';	/* Close enough approximation */
22 }
23 
24 /*
25  * Find a non-boolean option, that is, "option=argument".  In accordance
26  * with standard Linux practice, if this option is repeated, this returns
27  * the last instance on the command line.
28  *
29  * Returns the length of the argument (regardless of if it was
30  * truncated to fit in the buffer), or -1 on not found.
31  */
32 int cmdline_find_option(const char *option, char *buffer, int bufsize)
33 {
34 	u32 cmdline_ptr = boot_params.hdr.cmd_line_ptr;
35 	addr_t cptr;
36 	char c;
37 	int len = -1;
38 	const char *opptr = NULL;
39 	char *bufptr = buffer;
40 	enum {
41 		st_wordstart,	/* Start of word/after whitespace */
42 		st_wordcmp,	/* Comparing this word */
43 		st_wordskip,	/* Miscompare, skip */
44 		st_bufcpy	/* Copying this to buffer */
45 	} state = st_wordstart;
46 
47 	if (!cmdline_ptr || cmdline_ptr >= 0x100000)
48 		return -1;	/* No command line, or inaccessible */
49 
50 	cptr = cmdline_ptr & 0xf;
51 	set_fs(cmdline_ptr >> 4);
52 
53 	while (cptr < 0x10000 && (c = rdfs8(cptr++))) {
54 		switch (state) {
55 		case st_wordstart:
56 			if (myisspace(c))
57 				break;
58 
59 			/* else */
60 			state = st_wordcmp;
61 			opptr = option;
62 			/* fall through */
63 
64 		case st_wordcmp:
65 			if (c == '=' && !*opptr) {
66 				len = 0;
67 				bufptr = buffer;
68 				state = st_bufcpy;
69 			} else if (myisspace(c)) {
70 				state = st_wordstart;
71 			} else if (c != *opptr++) {
72 				state = st_wordskip;
73 			}
74 			break;
75 
76 		case st_wordskip:
77 			if (myisspace(c))
78 				state = st_wordstart;
79 			break;
80 
81 		case st_bufcpy:
82 			if (myisspace(c)) {
83 				state = st_wordstart;
84 			} else {
85 				if (len < bufsize-1)
86 					*bufptr++ = c;
87 				len++;
88 			}
89 			break;
90 		}
91 	}
92 
93 	if (bufsize)
94 		*bufptr = '\0';
95 
96 	return len;
97 }
98 
99 /*
100  * Find a boolean option (like quiet,noapic,nosmp....)
101  *
102  * Returns the position of that option (starts counting with 1)
103  * or 0 on not found
104  */
105 int cmdline_find_option_bool(const char *option)
106 {
107 	u32 cmdline_ptr = boot_params.hdr.cmd_line_ptr;
108 	addr_t cptr;
109 	char c;
110 	int pos = 0, wstart = 0;
111 	const char *opptr = NULL;
112 	enum {
113 		st_wordstart,	/* Start of word/after whitespace */
114 		st_wordcmp,	/* Comparing this word */
115 		st_wordskip,	/* Miscompare, skip */
116 	} state = st_wordstart;
117 
118 	if (!cmdline_ptr || cmdline_ptr >= 0x100000)
119 		return -1;	/* No command line, or inaccessible */
120 
121 	cptr = cmdline_ptr & 0xf;
122 	set_fs(cmdline_ptr >> 4);
123 
124 	while (cptr < 0x10000) {
125 		c = rdfs8(cptr++);
126 		pos++;
127 
128 		switch (state) {
129 		case st_wordstart:
130 			if (!c)
131 				return 0;
132 			else if (myisspace(c))
133 				break;
134 
135 			state = st_wordcmp;
136 			opptr = option;
137 			wstart = pos;
138 			/* fall through */
139 
140 		case st_wordcmp:
141 			if (!*opptr)
142 				if (!c || myisspace(c))
143 					return wstart;
144 				else
145 					state = st_wordskip;
146 			else if (!c)
147 				return 0;
148 			else if (c != *opptr++)
149 				state = st_wordskip;
150 			break;
151 
152 		case st_wordskip:
153 			if (!c)
154 				return 0;
155 			else if (myisspace(c))
156 				state = st_wordstart;
157 			break;
158 		}
159 	}
160 
161 	return 0;	/* Buffer overrun */
162 }
163