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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 | } |