arch/x86/lib/cmdline.c

   1 /*
   2  * This file is part of the Linux kernel, and is made available under
   3  * the terms of the GNU General Public License version 2.
   4  *
   5  * Misc librarized functions for cmdline poking.
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/string.h>
   9 #include <linux/ctype.h>
  10 #include <asm/setup.h>
  11
  12 static inline int myisspace(u8 c)
  13 {
  14         return c <= ' ';        /* Close enough approximation */
  15 }
  16
  17 /**
  18  * Find a boolean option (like quiet,noapic,nosmp....)
  19  *
  20  * @cmdline: the cmdline string
  21  * @option: option string to look for
  22  *
  23  * Returns the position of that @option (starts counting with 1)
  24  * or 0 on not found.
  25  */
  26 int cmdline_find_option_bool(const char *cmdline, const char *option)
  27 {
  28         char c;
  29         int len, pos = 0, wstart = 0;
  30         const char *opptr = NULL;
  31         enum {
  32                 st_wordstart = 0,       /* Start of word/after whitespace */
  33                 st_wordcmp,     /* Comparing this word */
  34                 st_wordskip,    /* Miscompare, skip */
  35         } state = st_wordstart;
  36
  37         if (!cmdline)
  38                 return -1;      /* No command line */
  39
  40         len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);
  41         if (!len)
  42                 return 0;
  43
  44         while (len--) {
  45                 c = *(char *)cmdline++;
  46                 pos++;
  47
  48                 switch (state) {
  49                 case st_wordstart:
  50                         if (!c)
  51                                 return 0;
  52                         else if (myisspace(c))
  53                                 break;
  54
  55                         state = st_wordcmp;
  56                         opptr = option;
  57                         wstart = pos;
  58                         /* fall through */
  59
  60                 case st_wordcmp:
  61                         if (!*opptr)
  62                                 if (!c || myisspace(c))
  63                                         return wstart;
  64                                 else
  65                                         state = st_wordskip;
  66                         else if (!c)
  67                                 return 0;
  68                         else if (c != *opptr++)
  69                                 state = st_wordskip;
  70                         else if (!len)          /* last word and is matching */
  71                                 return wstart;
  72                         break;
  73
  74                 case st_wordskip:
  75                         if (!c)
  76                                 return 0;
  77                         else if (myisspace(c))
  78                                 state = st_wordstart;
  79                         break;
  80                 }
  81         }
  82
  83         return 0;       /* Buffer overrun */
  84 }