x86 setup: early cmdline parser handle boolean options

This patch extends the early commandline parser to support boolean options.
The current version in mainline only supports parsing "option=arg" value pairs.

With this it should be easy making other messages like "Uncompressing kernel"
honour the "quiet" parameter, too.

Signed-off-by: Roland Kletzing <devzero@web.de>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 65 insertions, 0 deletions

diff --git a/arch/x86/boot/cmdline.c b/arch/x86/boot/cmdline.c
index 34bb778c4357..cc65a33bf65c 100644
--- a/arch/x86/boot/cmdline.c
+++ b/arch/x86/boot/cmdline.c
@@ -95,3 +95,68 @@ int cmdline_find_option(const char *option, char *buffer, int bufsize)
 
         return len;
 }
+
+/*
+ * Find a boolean option (like quiet,noapic,nosmp....)
+ *
+ * Returns the position of that option (starts counting with 1)
+ * or 0 on not found
+ */
+int cmdline_find_option_bool(const char *option)
+{
+        u32 cmdline_ptr = boot_params.hdr.cmd_line_ptr;
+        addr_t cptr;
+        char c;
+        int pos =0 , wstart = 0;
+        const char *opptr = NULL;
+        enum {
+                st_wordstart,   /* Start of word/after whitespace */
+                st_wordcmp,     /* Comparing this word */
+                st_wordskip,    /* Miscompare, skip */
+        } 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++);
+                pos++;
+
+                switch (state) {
+                case st_wordstart:
+                        if (!c)
+                                return 0;
+                        else if (myisspace(c))
+                                break;
+
+                        state = st_wordcmp;
+                        opptr = option;
+                        wstart = pos;
+                        /* fall through */
+
+                case st_wordcmp:
+                        if (!*opptr)
+                                if (!c || myisspace(c))
+                                        return wstart;
+                                else
+                                        state = st_wordskip;
+                        else if (!c)
+                                return 0;
+                        else if (c != *opptr++)
+                                state = st_wordskip;
+                        break;
+
+                case st_wordskip:
+                        if (!c)
+                                return 0;
+                        else if (myisspace(c))
+                                state = st_wordstart;
+                        break;
+                }
+        }
+
+        return 0;       /* Buffer overrun */
+}