[PATCH] x86/cmdline: Return 0 from cmdline_find_option_bool() for no cmdline

[Thorsten Blum <thorsten.blum@linux.dev>]

cmdline_find_option_bool() is documented to return the position of the
option or 0 when the option is not found. However, the boot-time and
kernel-proper implementations return -1 when there is no command line,
and the real-mode wrapper also returns -1 when the command line is
inaccessible.

That makes normal boolean use of the helper wrong: callers testing the
return value directly treat an unavailable command line as if the option
was present.

Return 0 from cmdline_find_option_bool() for unavailable command lines.

Fixes: 32d0b9898029 ("x86 setup: early cmdline parser handle boolean options")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 arch/x86/boot/boot.h    |  2 +-
 arch/x86/boot/cmdline.c |  6 +++---
 arch/x86/lib/cmdline.c  | 11 ++++++-----
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 8e3eab34dff4..b623572b6964 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -261,7 +261,7 @@ static inline int cmdline_find_option_bool(const char *option)
 	unsigned long cmd_line_ptr = boot_params.hdr.cmd_line_ptr;
 
 	if (cmd_line_ptr >= 0x100000)
-		return -1;      /* inaccessible */
+		return 0;	/* inaccessible */
 
 	return __cmdline_find_option_bool(cmd_line_ptr, option);
 }
diff --git a/arch/x86/boot/cmdline.c b/arch/x86/boot/cmdline.c
index 21d56ae83cdf..2418c9d0b5aa 100644
--- a/arch/x86/boot/cmdline.c
+++ b/arch/x86/boot/cmdline.c
@@ -94,8 +94,8 @@ int __cmdline_find_option(unsigned long cmdline_ptr, const char *option, char *b
 /*
  * Find a boolean option (like quiet,noapic,nosmp....)
  *
- * Returns the position of that option (starts counting with 1)
- * or 0 on not found
+ * Returns the position of that option (starts counting with 1),
+ * or 0 if the option is not found or the command line is unavailable.
  */
 int __cmdline_find_option_bool(unsigned long cmdline_ptr, const char *option)
 {
@@ -110,7 +110,7 @@ int __cmdline_find_option_bool(unsigned long cmdline_ptr, const char *option)
 	} state = st_wordstart;
 
 	if (!cmdline_ptr)
-		return -1;      /* No command line */
+		return 0;	/* No command line */
 
 	cptr = cmdline_ptr & 0xf;
 	set_fs(cmdline_ptr >> 4);
diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index c65cd5550454..0e40779a4729 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -23,10 +23,11 @@ static inline int myisspace(u8 c)
  * @max_cmdline_size: the maximum size of cmdline
  * @option: option string to look for
  *
- * Returns the position of that @option (starts counting with 1)
- * 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.
+ * Returns the position of that @option (starts counting with 1),
+ * or 0 if the option is not found or the command line is unavailable.
+ * @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.
  */
 static int
 __cmdline_find_option_bool(const char *cmdline, int max_cmdline_size,
@@ -42,7 +43,7 @@ __cmdline_find_option_bool(const char *cmdline, int max_cmdline_size,
 	} state = st_wordstart;
 
 	if (!cmdline)
-		return -1;      /* No command line */
+		return 0;	/* No command line */
 
 	/*
 	 * This 'pos' check ensures we do not overrun