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
  15 static 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  */
  28 int __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  */
 100 int __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 }