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    Subject[x86 setup 19/33] Command-line parsing code for the new x86 setup code
    Date
    From: H. Peter Anvin <hpa@zytor.com>

    Simple command-line parser which allows us to access the kernel command
    line from the setup code.

    Signed-off-by: H. Peter Anvin <hpa@zytor.com>
    ---
    arch/i386/boot/cmdline.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++
    1 files changed, 97 insertions(+), 0 deletions(-)
    create mode 100644 arch/i386/boot/cmdline.c
    diff --git a/arch/i386/boot/cmdline.c b/arch/i386/boot/cmdline.c
    new file mode 100644
    index 0000000..34bb778
    --- /dev/null
    +++ b/arch/i386/boot/cmdline.c
    @@ -0,0 +1,97 @@
    +/* -*- 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;
    +}
    --
    1.5.2.2
    -
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