| H. Peter Anvin | e44c22f | 2007-07-11 12:18:44 -0700 | [diff] [blame] | 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 | } |