Merge branch 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 boot updates from Ingo Molnar:
 "Early command line options parsing enhancements from Dave Hansen, plus
  minor cleanups and enhancements"

* 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/boot: Remove unused 'is_big_kernel' variable
  x86/boot: Use proper array element type in memset() size calculation
  x86/boot: Pass in size to early cmdline parsing
  x86/boot: Simplify early command line parsing
  x86/boot: Fix early command-line parsing when partial word matches
  x86/boot: Fix early command-line parsing when matching at end
  x86/boot: Simplify kernel load address alignment check
  x86/boot: Micro-optimize reset_early_page_tables()

1 files changed, 43 insertions, 17 deletions

diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index 422db00..5cc78bf 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -21,12 +21,16 @@ static inline int myisspace(u8 c)
  * @option: option string to look for
  *
  * Returns the position of that @option (starts counting with 1)
- * or 0 on not found.
+ * or 0 on not found.  @option will only be found if it is found
+ * as an entire word in @cmdline.  For instance, if @option="car"
+ * then a cmdline which contains "cart" will not match.
  */
-int cmdline_find_option_bool(const char *cmdline, const char *option)
+static int
+__cmdline_find_option_bool(const char *cmdline, int max_cmdline_size,
+			   const char *option)
 {
 	char c;
-	int len, pos = 0, wstart = 0;
+	int pos = 0, wstart = 0;
 	const char *opptr = NULL;
 	enum {
 		st_wordstart = 0,	/* Start of word/after whitespace */
@@ -37,11 +41,11 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 	if (!cmdline)
 		return -1;      /* No command line */
 
-	len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);
-	if (!len)
-		return 0;
-
-	while (len--) {
+	/*
+	 * This 'pos' check ensures we do not overrun
+	 * a non-NULL-terminated 'cmdline'
+	 */
+	while (pos < max_cmdline_size) {
 		c = *(char *)cmdline++;
 		pos++;
 
@@ -58,18 +62,35 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 			/* fall through */
 
 		case st_wordcmp:
-			if (!*opptr)
+			if (!*opptr) {
+				/*
+				 * We matched all the way to the end of the
+				 * option we were looking for.  If the
+				 * command-line has a space _or_ ends, then
+				 * we matched!
+				 */
 				if (!c || myisspace(c))
 					return wstart;
-				else
-					state = st_wordskip;
-			else if (!c)
+				/*
+				 * We hit the end of the option, but _not_
+				 * the end of a word on the cmdline.  Not
+				 * a match.
+				 */
+			} else if (!c) {
+				/*
+				 * Hit the NULL terminator on the end of
+				 * cmdline.
+				 */
 				return 0;
-			else if (c != *opptr++)
-				state = st_wordskip;
-			else if (!len)		/* last word and is matching */
-				return wstart;
-			break;
+			} else if (c == *opptr++) {
+				/*
+				 * We are currently matching, so continue
+				 * to the next character on the cmdline.
+				 */
+				break;
+			}
+			state = st_wordskip;
+			/* fall through */
 
 		case st_wordskip:
 			if (!c)
@@ -82,3 +103,8 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 
 	return 0;	/* Buffer overrun */
 }
+
+int cmdline_find_option_bool(const char *cmdline, const char *option)
+{
+	return __cmdline_find_option_bool(cmdline, COMMAND_LINE_SIZE, option);
+}