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: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 97 insertions, 0 deletions

diff --git a/arch/i386/boot/cmdline.c b/arch/i386/boot/cmdline.c
new file mode 100644
index 000000000000..34bb778c4357
--- /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;
+}