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.  @option will only be found if it is found
 25 * as an entire word in @cmdline.  For instance, if @option="car"
 26 * then a cmdline which contains "cart" will not match.
 27 */
 28static int
 29__cmdline_find_option_bool(const char *cmdline, int max_cmdline_size,
 30			   const char *option)
 31{
 32	char c;
 33	int pos = 0, wstart = 0;
 34	const char *opptr = NULL;
 35	enum {
 36		st_wordstart = 0,	/* Start of word/after whitespace */
 37		st_wordcmp,	/* Comparing this word */
 38		st_wordskip,	/* Miscompare, skip */
 39	} state = st_wordstart;
 40
 41	if (!cmdline)
 42		return -1;      /* No command line */
 43
 44	/*
 45	 * This 'pos' check ensures we do not overrun
 46	 * a non-NULL-terminated 'cmdline'
 47	 */
 48	while (pos < max_cmdline_size) {
 49		c = *(char *)cmdline++;
 50		pos++;
 51
 52		switch (state) {
 53		case st_wordstart:
 54			if (!c)
 55				return 0;
 56			else if (myisspace(c))
 57				break;
 58
 59			state = st_wordcmp;
 60			opptr = option;
 61			wstart = pos;
 62			/* fall through */
 63
 64		case st_wordcmp:
 65			if (!*opptr) {
 66				/*
 67				 * We matched all the way to the end of the
 68				 * option we were looking for.  If the
 69				 * command-line has a space _or_ ends, then
 70				 * we matched!
 71				 */
 72				if (!c || myisspace(c))
 73					return wstart;
 74				/*
 75				 * We hit the end of the option, but _not_
 76				 * the end of a word on the cmdline.  Not
 77				 * a match.
 78				 */
 79			} else if (!c) {
 80				/*
 81				 * Hit the NULL terminator on the end of
 82				 * cmdline.
 83				 */
 84				return 0;
 85			} else if (c == *opptr++) {
 86				/*
 87				 * We are currently matching, so continue
 88				 * to the next character on the cmdline.
 89				 */
 90				break;
 91			}
 92			state = st_wordskip;
 93			/* fall through */
 94
 95		case st_wordskip:
 96			if (!c)
 97				return 0;
 98			else if (myisspace(c))
 99				state = st_wordstart;
100			break;
101		}
102	}
103
104	return 0;	/* Buffer overrun */
105}
106
107int cmdline_find_option_bool(const char *cmdline, const char *option)
108{
109	return __cmdline_find_option_bool(cmdline, COMMAND_LINE_SIZE, option);
110}