Commit e44c22f6 authored by H. Peter Anvin's avatar H. Peter Anvin Committed by Linus Torvalds
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Command-line parsing code for the new x86 setup code



Simple command-line parser which allows us to access the kernel command
line from the setup code.
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 49df18fa
/* -*- linux-c -*- ------------------------------------------------------- *
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright 2007 rPath, Inc. - All Rights Reserved
*
* This file is part of the Linux kernel, and is made available under
* the terms of the GNU General Public License version 2.
*
* ----------------------------------------------------------------------- */
/*
* arch/i386/boot/cmdline.c
*
* Simple command-line parser for early boot.
*/
#include "boot.h"
static inline int myisspace(u8 c)
{
return c <= ' '; /* Close enough approximation */
}
/*
* Find a non-boolean option, that is, "option=argument". In accordance
* with standard Linux practice, if this option is repeated, this returns
* the last instance on the command line.
*
* Returns the length of the argument (regardless of if it was
* truncated to fit in the buffer), or -1 on not found.
*/
int cmdline_find_option(const char *option, char *buffer, int bufsize)
{
u32 cmdline_ptr = boot_params.hdr.cmd_line_ptr;
addr_t cptr;
char c;
int len = -1;
const char *opptr = NULL;
char *bufptr = buffer;
enum {
st_wordstart, /* Start of word/after whitespace */
st_wordcmp, /* Comparing this word */
st_wordskip, /* Miscompare, skip */
st_bufcpy /* Copying this to buffer */
} state = st_wordstart;
if (!cmdline_ptr || cmdline_ptr >= 0x100000)
return -1; /* No command line, or inaccessible */
cptr = cmdline_ptr & 0xf;
set_fs(cmdline_ptr >> 4);
while (cptr < 0x10000 && (c = rdfs8(cptr++))) {
switch (state) {
case st_wordstart:
if (myisspace(c))
break;
/* else */
state = st_wordcmp;
opptr = option;
/* fall through */
case st_wordcmp:
if (c == '=' && !*opptr) {
len = 0;
bufptr = buffer;
state = st_bufcpy;
} else if (myisspace(c)) {
state = st_wordstart;
} else if (c != *opptr++) {
state = st_wordskip;
}
break;
case st_wordskip:
if (myisspace(c))
state = st_wordstart;
break;
case st_bufcpy:
if (myisspace(c)) {
state = st_wordstart;
} else {
if (len < bufsize-1)
*bufptr++ = c;
len++;
}
break;
}
}
if (bufsize)
*bufptr = '\0';
return len;
}
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