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