LXR linux/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
  12static 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 */
  26int 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}
  85