kernel/arch/x86/boot/cmdline.c

   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(unsigned long 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(unsigned long 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 }