LXR linux/arch/x86/boot/cmdline.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/* -*- linux-c -*- ------------------------------------------------------- *
   3 *
   4 *   Copyright (C) 1991, 1992 Linus Torvalds
   5 *   Copyright 2007 rPath, Inc. - All Rights Reserved
   6 *
   7 * ----------------------------------------------------------------------- */
   8
   9/*
  10 * Simple command-line parser for early boot.
  11 */
  12
  13#include "boot.h"
  14
  15static inline int myisspace(u8 c)
  16{
  17        return c <= ' ';        /* Close enough approximation */
  18}
  19
  20/*
  21 * Find a non-boolean option, that is, "option=argument".  In accordance
  22 * with standard Linux practice, if this option is repeated, this returns
  23 * the last instance on the command line.
  24 *
  25 * Returns the length of the argument (regardless of if it was
  26 * truncated to fit in the buffer), or -1 on not found.
  27 */
  28int __cmdline_find_option(unsigned long cmdline_ptr, const char *option, char *buffer, int bufsize)
  29{
  30        addr_t cptr;
  31        char c;
  32        int len = -1;
  33        const char *opptr = NULL;
  34        char *bufptr = buffer;
  35        enum {
  36                st_wordstart,   /* Start of word/after whitespace */
  37                st_wordcmp,     /* Comparing this word */
  38                st_wordskip,    /* Miscompare, skip */
  39                st_bufcpy       /* Copying this to buffer */
  40        } state = st_wordstart;
  41
  42        if (!cmdline_ptr)
  43                return -1;      /* No command line */
  44
  45        cptr = cmdline_ptr & 0xf;
  46        set_fs(cmdline_ptr >> 4);
  47
  48        while (cptr < 0x10000 && (c = rdfs8(cptr++))) {
  49                switch (state) {
  50                case st_wordstart:
  51                        if (myisspace(c))
  52                                break;
  53
  54                        /* else */
  55                        state = st_wordcmp;
  56                        opptr = option;
  57                        fallthrough;
  58
  59                case st_wordcmp:
  60                        if (c == '=' && !*opptr) {
  61                                len = 0;
  62                                bufptr = buffer;
  63                                state = st_bufcpy;
  64                        } else if (myisspace(c)) {
  65                                state = st_wordstart;
  66                        } else if (c != *opptr++) {
  67                                state = st_wordskip;
  68                        }
  69                        break;
  70
  71                case st_wordskip:
  72                        if (myisspace(c))
  73                                state = st_wordstart;
  74                        break;
  75
  76                case st_bufcpy:
  77                        if (myisspace(c)) {
  78                                state = st_wordstart;
  79                        } else {
  80                                if (len < bufsize-1)
  81                                        *bufptr++ = c;
  82                                len++;
  83                        }
  84                        break;
  85                }
  86        }
  87
  88        if (bufsize)
  89                *bufptr = '\0';
  90
  91        return len;
  92}
  93
  94/*
  95 * Find a boolean option (like quiet,noapic,nosmp....)
  96 *
  97 * Returns the position of that option (starts counting with 1)
  98 * or 0 on not found
  99 */
 100int __cmdline_find_option_bool(unsigned long cmdline_ptr, const char *option)
 101{
 102        addr_t cptr;
 103        char c;
 104        int pos = 0, wstart = 0;
 105        const char *opptr = NULL;
 106        enum {
 107                st_wordstart,   /* Start of word/after whitespace */
 108                st_wordcmp,     /* Comparing this word */
 109                st_wordskip,    /* Miscompare, skip */
 110        } state = st_wordstart;
 111
 112        if (!cmdline_ptr)
 113                return -1;      /* No command line */
 114
 115        cptr = cmdline_ptr & 0xf;
 116        set_fs(cmdline_ptr >> 4);
 117
 118        while (cptr < 0x10000) {
 119                c = rdfs8(cptr++);
 120                pos++;
 121
 122                switch (state) {
 123                case st_wordstart:
 124                        if (!c)
 125                                return 0;
 126                        else if (myisspace(c))
 127                                break;
 128
 129                        state = st_wordcmp;
 130                        opptr = option;
 131                        wstart = pos;
 132                        fallthrough;
 133
 134                case st_wordcmp:
 135                        if (!*opptr)
 136                                if (!c || myisspace(c))
 137                                        return wstart;
 138                                else
 139                                        state = st_wordskip;
 140                        else if (!c)
 141                                return 0;
 142                        else if (c != *opptr++)
 143                                state = st_wordskip;
 144                        break;
 145
 146                case st_wordskip:
 147                        if (!c)
 148                                return 0;
 149                        else if (myisspace(c))
 150                                state = st_wordstart;
 151                        break;
 152                }
 153        }
 154
 155        return 0;       /* Buffer overrun */
 156}
 157