[PATCH 0/5] x86: early command-line parsing fixes / tests (v2)

[PATCH 0/5] x86: early command-line parsing fixes / tests (v2)

[Dave Hansen]

The code here is unchanged except for fixing a compile error that
I managed to introduce just before I sent it last time.

The tests for this code are in the last two patches.  If folks
think it is overkill, those can be left out.  But, the first
three are still needed.

Cc: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com

[PATCH 1/5] x86: fix early command-line parsing when matching at end

[Dave Hansen]

From: Dave Hansen <dave.hansen@linux.intel.com>

The x86 early command line parsing in cmdline_find_option_bool()
is buggy.  If it matches a specified 'option' all the way to
the end of the command-line, it will consider it a match.

For instance,

    	cmdline = "foo";
    	cmdline_find_option_bool(cmdline, "fool");

will return 1.  This is particularly annoying since we have
actual FPU options like "noxsave" and "noxsaves"  So,
command-line "foo bar noxsave" will match *BOTH* a "noxsave" and
"noxsaves". (This turns out not to be an actual problem because
"noxsave" implies "noxsaves", but it's still confusing.)

To fix this, we simplify the code and stop tracking 'len'.  'len'
was trying to indicate either the NULL terminator *OR* the end of
a non-NULL-terminated commandline at 'COMMAND_LINE_SIZE'.  But,
each of the three states is *already* checking 'cmdline' for a
NULL terminator.

We _only_ need to check if we have overrun 'COMMAND_LINE_SIZE',
and that we can do without keeping 'len' around.

Also add some commends to clarify what is going on.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
---

 b/arch/x86/lib/cmdline.c |   34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff -puN arch/x86/lib/cmdline.c~x86-broken-end-of-string-command-line-parsing arch/x86/lib/cmdline.c
--- a/arch/x86/lib/cmdline.c~x86-broken-end-of-string-command-line-parsing	2015-12-22 11:56:58.639149442 -0800
+++ b/arch/x86/lib/cmdline.c	2015-12-22 11:56:58.642149577 -0800
@@ -21,12 +21,14 @@ 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)
 {
 	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 +39,14 @@ int cmdline_find_option_bool(const char
 	if (!cmdline)
 		return -1;      /* No command line */
 
-	len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);
-	if (!len)
+	if (!strlen(cmdline))
 		return 0;
 
-	while (len--) {
+	/*
+	 * This 'pos' check ensures we do not overrun
+	 * a non-NULL-terminated 'cmdline'
+	 */
+	while (pos < COMMAND_LINE_SIZE) {
 		c = *(char *)cmdline++;
 		pos++;
 
@@ -58,17 +63,26 @@ int cmdline_find_option_bool(const char
 			/* 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)
+			} else if (!c) {
+				/*
+				 * Hit the NULL terminator on the end of
+				 * cmdline.
+				 */
 				return 0;
-			else if (c != *opptr++)
+			} else if (c != *opptr++) {
 				state = st_wordskip;
-			else if (!len)		/* last word and is matching */
-				return wstart;
+			}
 			break;
 
 		case st_wordskip:
_

[PATCH 2/5] x86: fix early command-line parsing, when partial word match

[Dave Hansen]

From: Dave Hansen <dave.hansen@linux.intel.com>

cmdline_find_option_bool() keeps track of position in two strings:
1. the command-line
2. the option we are searchign for in the command-line

We plow through each character in the command-line one at a time,
always moving forward.  We move forward in the option ('opptr')
when we match characters in 'cmdline'.  We reset the 'opptr' only
when we go in to the 'st_wordstart' state.

But, if we fail to match an option because we see a space (
state=st_wordcmp, *opptr='\0',c=' '), we set state='st_wordskip'
and 'break', moving to the next character.  But, that move to
the next character is the one *after* the ' '.  This means that
we will miss a 'st_wordstart' state.

For instance, if we have

	cmdline = "foo fool";

and are searching for "fool", we have:

	"fool"
opptr = ----^

	"foo fool"
c = --------^

We see that 'l' != ' ', set state=st_wordskip, break, and then
move 'c', so:

	"foo fool"
c = ---------^

and are still in state=st_wordskip.  We will stay in wordskip
until we have skipped "fool", thus missing the option we were
looking for.  This *only* happens when you have a partially-
matching word followed by a matching one.

To fix this, we always fall *into* the 'st_wordskip' state when
we set it.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
---

 b/arch/x86/lib/cmdline.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff -puN arch/x86/lib/cmdline.c~x86-mid-option-match-command-line-parsing arch/x86/lib/cmdline.c
--- a/arch/x86/lib/cmdline.c~x86-mid-option-match-command-line-parsing	2015-12-22 11:56:59.047167827 -0800
+++ b/arch/x86/lib/cmdline.c	2015-12-22 11:56:59.050167962 -0800
@@ -72,18 +72,26 @@ int cmdline_find_option_bool(const char
 				 */
 				if (!c || myisspace(c))
 					return wstart;
-				else
-					state = st_wordskip;
+				/*
+				 * 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 (c == *opptr++) {
+				/*
+				 * We are currently matching, so continue
+				 * to the next character on the cmdline.
+				 */
+				break;
 			}
-			break;
+			state = st_wordskip;
+			/* fall through */
 
 		case st_wordskip:
 			if (!c)
_

[PATCH 3/5] x86: simplify early command line parsing

[Dave Hansen]

From: Dave Hansen <dave.hansen@linux.intel.com>

__cmdline_find_option_bool() tries to account for both
NULL-terminated and non-NULL-terminated strings.  It keeps 'pos'
to look for the end of the buffer and also looks for '!c' in a
bunch of places to look for NULL termination.

But, it also calls strlen().  You can't call strlen on a
non-NULL-terminated string.

If !strlen(cmdline), then cmdline[0]=='\0'.  In that case, we
will go in to the while() loop, set c='\0', hit st_wordstart,
notice !c, and will immediately return 0.

So, remove the strlen().  It is unnecessary and unsafe.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
---

 b/arch/x86/lib/cmdline.c |    3 ---
 1 file changed, 3 deletions(-)

diff -puN arch/x86/lib/cmdline.c~x86-early-command-line-non-term arch/x86/lib/cmdline.c
--- a/arch/x86/lib/cmdline.c~x86-early-command-line-non-term	2015-12-22 11:56:59.454186167 -0800
+++ b/arch/x86/lib/cmdline.c	2015-12-22 11:56:59.457186302 -0800
@@ -39,9 +39,6 @@ int cmdline_find_option_bool(const char
 	if (!cmdline)
 		return -1;      /* No command line */
 
-	if (!strlen(cmdline))
-		return 0;
-
 	/*
 	 * This 'pos' check ensures we do not overrun
 	 * a non-NULL-terminated 'cmdline'
_

[PATCH 4/5] x86: pass in size to early cmdline parsing

[Dave Hansen]

From: Dave Hansen <dave.hansen@linux.intel.com>

We will use this in a few patches to implement tests for early
parsing.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
---

 b/arch/x86/lib/cmdline.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff -puN arch/x86/lib/cmdline.c~pass-in-cmdline-size arch/x86/lib/cmdline.c
--- a/arch/x86/lib/cmdline.c~pass-in-cmdline-size	2015-12-22 11:56:59.859204417 -0800
+++ b/arch/x86/lib/cmdline.c	2015-12-22 11:56:59.862204552 -0800
@@ -25,7 +25,8 @@ static inline int myisspace(u8 c)
  * 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 pos = 0, wstart = 0;
@@ -43,7 +44,7 @@ int cmdline_find_option_bool(const char
 	 * This 'pos' check ensures we do not overrun
 	 * a non-NULL-terminated 'cmdline'
 	 */
-	while (pos < COMMAND_LINE_SIZE) {
+	while (pos < max_cmdline_size) {
 		c = *(char *)cmdline++;
 		pos++;
 
@@ -101,3 +102,9 @@ int cmdline_find_option_bool(const char
 
 	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);
+}
_

[PATCH 5/5] x86: test early command-line code

[Dave Hansen]

From: Dave Hansen <dave.hansen@linux.intel.com>

Here are some simple tests for the early command-line code.  It
had way more bugs than it should have, so let's make sure they
never pop up again.

Note, there are a few failures in here now.  We will fix those
up in the next few patches.

This is complete overkill for this code, but I had to do it to
convince myself that I wasn't making it any worse.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: linux-kernel@vger.kernel.org
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
---

 b/arch/x86/Kconfig.debug  |    7 ++
 b/arch/x86/kernel/check.c |    1 
 b/arch/x86/kernel/setup.c |    9 +++
 b/arch/x86/lib/cmdline.c  |  122 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 138 insertions(+), 1 deletion(-)

diff -puN arch/x86/Kconfig.debug~x86-early-command-line-test arch/x86/Kconfig.debug
--- a/arch/x86/Kconfig.debug~x86-early-command-line-test	2015-12-22 11:57:01.229266152 -0800
+++ b/arch/x86/Kconfig.debug	2015-12-22 11:57:01.238266557 -0800
@@ -400,4 +400,11 @@ config PUNIT_ATOM_DEBUG
 	  The current power state can be read from
 	  /sys/kernel/debug/punit_atom/dev_power_state
 
+config X86_TEST_EARLY_CMDLINE
+	bool "Early command line runtime tests"
+	---help---
+	  This creates some test command-lines and tries to parse
+	  a bunch of options from them.  The overhead is small both
+	  at boot and increased text/data sizes.
+
 endmenu
diff -puN arch/x86/kernel/check.c~x86-early-command-line-test arch/x86/kernel/check.c
--- a/arch/x86/kernel/check.c~x86-early-command-line-test	2015-12-22 11:57:01.230266197 -0800
+++ b/arch/x86/kernel/check.c	2015-12-22 11:57:01.239266602 -0800
@@ -164,4 +164,3 @@ static int start_periodic_check_for_corr
 	return 0;
 }
 device_initcall(start_periodic_check_for_corruption);
-
diff -puN arch/x86/lib/cmdline.c~x86-early-command-line-test arch/x86/lib/cmdline.c
--- a/arch/x86/lib/cmdline.c~x86-early-command-line-test	2015-12-22 11:57:01.232266287 -0800
+++ b/arch/x86/lib/cmdline.c	2015-12-22 11:57:01.239266602 -0800
@@ -4,6 +4,7 @@
  *
  * Misc librarized functions for cmdline poking.
  */
+#include <linux/bug.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
@@ -108,3 +109,124 @@ int cmdline_find_option_bool(const char
 	return __cmdline_find_option_bool(cmdline, COMMAND_LINE_SIZE,
 			option);
 }
+
+#ifdef CONFIG_X86_TEST_EARLY_CMDLINE
+
+static int __cmdtest(char *cmdline, int str_size, char *option,
+		int expected_result, int do_shrink)
+{
+	int ret;
+	int null_terminate;
+	/* Results are 1-based, so bias back down by 1 */
+	int option_end = expected_result + strlen(option) - 1;
+	int shrink_max = 0;
+
+	if (cmdline && do_shrink)
+		shrink_max = strlen(cmdline);
+	/*
+	 * The option was not found.  If it was not found in the
+	 * *full* command-line, it should never be found in any
+	 * *part* of the command-line.
+	 */
+	for (null_terminate = 0; null_terminate <= 1; null_terminate++) {
+		int shrink_by;
+		for (shrink_by = 0; shrink_by < shrink_max; shrink_by++) {
+			int str_size_tst = str_size - shrink_by;
+			char tmp = cmdline[str_size_tst];
+
+			/*
+			 * Do not run tests that would truncate
+			 * over the expected option
+			 */
+			if (str_size_tst <= option_end)
+				continue;
+
+			if (null_terminate)
+				cmdline[str_size_tst] = '\0';
+			ret = __cmdline_find_option_bool(cmdline, str_size_tst,
+					option);
+			if (null_terminate)
+				cmdline[str_size_tst] = tmp;
+
+			if (ret == expected_result)
+				continue;
+			pr_err("failed cmdline test ('%s', %d, '%s') == %d "
+					"nulld: %d got: %d\n",
+					cmdline, str_size_tst, option,
+					expected_result, null_terminate,
+					ret);
+			return 1;
+		}
+	}
+	return 0;
+}
+
+#define cmdtest(cmdline, option, result)	\
+	WARN_ON(__cmdtest(cmdline, sizeof(cmdline), option, result, 1))
+
+#define cmdtest_noshrink(cmdline, option, result)	\
+	WARN_ON(__cmdtest(cmdline, sizeof(cmdline), option, result, 0))
+
+char cmdline1[] = "CALL me Ishmael  ";
+char cmdline2[] = "Whenever I find myself growing grim about the mouth  ";
+char cmdline3[] = "grow growing  ";
+int test_early_cmdline(void)
+{
+	/* NULL command-line: */
+	WARN_ON(__cmdline_find_option_bool(NULL, 22, "Ishmael") != -1);
+	/* zero-length command-line: */
+	cmdtest("", "Ishmael", 0);
+
+	/* Find words at each of 3 positions: start, middle, end */
+	cmdtest(cmdline1, "CALL", 1);
+	cmdtest(cmdline1, "me", 6);
+	cmdtest(cmdline1, "Ishmael", 9);
+
+	/*
+	 * Fail to find strings that all occur in the cmdline,
+	 * but not as full words
+	 */
+	/*
+	 * If "option" is _present_ in "cmdline" as the start of a
+	 * word, like cmdline="foo bar" and we pass in option="b",
+	 * when we shrink cmdline to "foo b", it will match.  So,
+	 * skip shrink tests for those.
+	 */
+	cmdtest_noshrink(cmdline1, "m", 0);
+	cmdtest(cmdline1, "e", 0);
+	cmdtest(cmdline1, "C", 0);
+	cmdtest(cmdline1, "l", 0);
+	cmdtest_noshrink(cmdline1, "Ishmae", 0);
+	cmdtest(cmdline1, "mael", 0);
+	/*
+	 * Look for strings that do not occur, but match until
+	 * close to the end of cmdline
+	 */
+	cmdtest_noshrink(cmdline1, "Ishmae", 0);
+	cmdtest(cmdline1, "Ishmaels", 0);
+	cmdtest(cmdline1, "maels", 0);
+
+	/*
+	 * Look for full words that do not occur in a different
+	 * cmdline
+	 */
+	cmdtest(cmdline2, "CALL", 0);
+	cmdtest(cmdline2, "me", 0);
+	cmdtest(cmdline2, "Ishmael", 0);
+	/*
+	 * Look for full words which do occur in cmdline2
+	 */
+	cmdtest(cmdline2, "Whenever", 1);
+	cmdtest(cmdline2, "growing", 24);
+	cmdtest(cmdline2, "grim", 32);
+	cmdtest(cmdline2, "mouth", 47);
+
+	/*
+	 * Catch the bug where if we match a partial word and
+	 * then have a space, we do not match the _next_ word.
+	 */
+	cmdtest(cmdline3, "grow", 1);
+	cmdtest(cmdline3, "growing", 6);
+	return 0;
+}
+#endif /* CONFIG_X86_TEST_EARLY_CMDLINE */
diff -puN arch/x86/kernel/setup.c~x86-early-command-line-test arch/x86/kernel/setup.c
--- a/arch/x86/kernel/setup.c~x86-early-command-line-test	2015-12-22 11:57:01.233266332 -0800
+++ b/arch/x86/kernel/setup.c	2015-12-22 11:57:01.239266602 -0800
@@ -1282,3 +1282,12 @@ static int __init register_kernel_offset
 	return 0;
 }
 __initcall(register_kernel_offset_dumper);
+
+/*
+ * This code is in lib/ and we do not link initcalls from there.
+ * Stash it here instead.
+ */
+#ifdef CONFIG_X86_TEST_EARLY_CMDLINE
+int test_early_cmdline(void);
+late_initcall(test_early_cmdline);
+#endif /* CONFIG_X86_TEST_EARLY_CMDLINE */
_

Re: [PATCH 1/5] x86: fix early command-line parsing when matching at end

[Borislav Petkov]

On Tue, Dec 22, 2015 at 02:52:38PM -0800, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> The x86 early command line parsing in cmdline_find_option_bool()
> is buggy.  If it matches a specified 'option' all the way to
> the end of the command-line, it will consider it a match.
> 
> For instance,
> 
>     	cmdline = "foo";
>     	cmdline_find_option_bool(cmdline, "fool");
> 
> will return 1.  This is particularly annoying since we have
> actual FPU options like "noxsave" and "noxsaves"  So,
> command-line "foo bar noxsave" will match *BOTH* a "noxsave" and
> "noxsaves". (This turns out not to be an actual problem because
> "noxsave" implies "noxsaves", but it's still confusing.)

So I booted a guest with this command line:

[    0.000000] Kernel command line: root=/dev/sda1 resume=/dev/sdb1 debug ignore_loglevel log_buf_len=16M earlyprintk=ttyS0,115200 console=ttyS0,115200 console=tty0 noxsave

after applying the debug hunk below. However, the only debug output I
got is this:

[    0.000000] x86_noxsave_setup

If I supply "noxsaves", I get, as expected

[    0.000000] x86_noxsaves_setup

only. Ditto for "noxsaveopt".

So what am I missing?

---
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 1a6adcb4fbce..472f6edfb8d9 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -354,6 +354,8 @@ static int __init x86_noxsave_setup(char *s)
 	if (strlen(s))
 		return 0;
 
+	pr_info("%s\n", __func__);
+
 	fpu__xstate_clear_all_cpu_caps();
 
 	return 1;
@@ -367,6 +369,8 @@ static int __init x86_noxsaveopt_setup(char *s)
 {
 	setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
 
+	pr_info("%s\n", __func__);
+
 	return 1;
 }
 __setup("noxsaveopt", x86_noxsaveopt_setup);
@@ -378,6 +382,8 @@ static int __init x86_noxsaves_setup(char *s)
 {
 	setup_clear_cpu_cap(X86_FEATURE_XSAVES);
 
+	pr_info("%s\n", __func__);
+
 	return 1;
 }
 __setup("noxsaves", x86_noxsaves_setup);

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

Re: [PATCH 1/5] x86: fix early command-line parsing when matching at end

[Dave Hansen]

On 01/05/2016 10:35 AM, Borislav Petkov wrote:
> On Tue, Dec 22, 2015 at 02:52:38PM -0800, Dave Hansen wrote:
>> From: Dave Hansen <dave.hansen@linux.intel.com>
>> The x86 early command line parsing in cmdline_find_option_bool()
>> is buggy.  If it matches a specified 'option' all the way to
>> the end of the command-line, it will consider it a match.
>>
>> For instance,
>>
>>     	cmdline = "foo";
>>     	cmdline_find_option_bool(cmdline, "fool");
>>
>> will return 1.  This is particularly annoying since we have
>> actual FPU options like "noxsave" and "noxsaves"  So,
>> command-line "foo bar noxsave" will match *BOTH* a "noxsave" and
>> "noxsaves". (This turns out not to be an actual problem because
>> "noxsave" implies "noxsaves", but it's still confusing.)
> 
> So I booted a guest with this command line:
> 
> [    0.000000] Kernel command line: root=/dev/sda1 resume=/dev/sdb1 debug ignore_loglevel log_buf_len=16M earlyprintk=ttyS0,115200 console=ttyS0,115200 console=tty0 noxsave
> 
> after applying the debug hunk below. However, the only debug output I
> got is this:
> 
> [    0.000000] x86_noxsave_setup
> 
> If I supply "noxsaves", I get, as expected
> 
> [    0.000000] x86_noxsaves_setup
> 
> only. Ditto for "noxsaveopt".
> 
> So what am I missing?

The current code uses __setup() which uses different parsing than
cmdline_find_option_bool().  We're going to have to move the noxsave*
ones over to cmdline_find_option_bool() since we need the parsing
earlier than __setup() works.

The changelog should have been more clear on this, though.

Re: [PATCH 1/5] x86: fix early command-line parsing when matching at end

[Borislav Petkov]

On Tue, Dec 22, 2015 at 02:52:38PM -0800, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> The x86 early command line parsing in cmdline_find_option_bool()
> is buggy.  If it matches a specified 'option' all the way to
> the end of the command-line, it will consider it a match.
> 
> For instance,
> 
>     	cmdline = "foo";
>     	cmdline_find_option_bool(cmdline, "fool");
> 
> will return 1.  This is particularly annoying since we have
> actual FPU options like "noxsave" and "noxsaves"  So,
> command-line "foo bar noxsave" will match *BOTH* a "noxsave" and
> "noxsaves". (This turns out not to be an actual problem because
> "noxsave" implies "noxsaves", but it's still confusing.)
> 
> To fix this, we simplify the code and stop tracking 'len'.  'len'
> was trying to indicate either the NULL terminator *OR* the end of
> a non-NULL-terminated commandline at 'COMMAND_LINE_SIZE'.  But,
> each of the three states is *already* checking 'cmdline' for a
> NULL terminator.
> 
> We _only_ need to check if we have overrun 'COMMAND_LINE_SIZE',
> and that we can do without keeping 'len' around.
> 
> Also add some commends to clarify what is going on.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: fenghua.yu@intel.com
> Cc: yu-cheng.yu@intel.com
> ---
> 
>  b/arch/x86/lib/cmdline.c |   34 ++++++++++++++++++++++++----------
>  1 file changed, 24 insertions(+), 10 deletions(-)
> 
> diff -puN arch/x86/lib/cmdline.c~x86-broken-end-of-string-command-line-parsing arch/x86/lib/cmdline.c
> --- a/arch/x86/lib/cmdline.c~x86-broken-end-of-string-command-line-parsing	2015-12-22 11:56:58.639149442 -0800
> +++ b/arch/x86/lib/cmdline.c	2015-12-22 11:56:58.642149577 -0800
> @@ -21,12 +21,14 @@ 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)
>  {
>  	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 +39,14 @@ int cmdline_find_option_bool(const char
>  	if (!cmdline)
>  		return -1;      /* No command line */
>  
> -	len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);
> -	if (!len)
> +	if (!strlen(cmdline))
>  		return 0;
>  
> -	while (len--) {
> +	/*
> +	 * This 'pos' check ensures we do not overrun
> +	 * a non-NULL-terminated 'cmdline'
> +	 */
> +	while (pos < COMMAND_LINE_SIZE) {

So this is a little bit strange: you're checking strlen(cmdline) above
but iterating until COMMAND_LINE_SIZE.

I think we should make it even more palatable:

	while (pos < min_t(int, strlen(cmdline), COMMAND_LINE_SIZE))

so that it is obvious how far we iterate. I know, I know, it boils down
to the same code because each state is checking !c but this way it is
clearer what we're doing when someone looks at that code again.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

Re: [PATCH 3/5] x86: simplify early command line parsing

[Borislav Petkov]

On Tue, Dec 22, 2015 at 02:52:41PM -0800, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> __cmdline_find_option_bool() tries to account for both
> NULL-terminated and non-NULL-terminated strings.  It keeps 'pos'
> to look for the end of the buffer and also looks for '!c' in a
> bunch of places to look for NULL termination.
> 
> But, it also calls strlen().  You can't call strlen on a
> non-NULL-terminated string.
> 
> If !strlen(cmdline), then cmdline[0]=='\0'.  In that case, we
> will go in to the while() loop, set c='\0', hit st_wordstart,
> notice !c, and will immediately return 0.
> 
> So, remove the strlen().  It is unnecessary and unsafe.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: fenghua.yu@intel.com
> Cc: yu-cheng.yu@intel.com
> ---
> 
>  b/arch/x86/lib/cmdline.c |    3 ---
>  1 file changed, 3 deletions(-)
> 
> diff -puN arch/x86/lib/cmdline.c~x86-early-command-line-non-term arch/x86/lib/cmdline.c
> --- a/arch/x86/lib/cmdline.c~x86-early-command-line-non-term	2015-12-22 11:56:59.454186167 -0800
> +++ b/arch/x86/lib/cmdline.c	2015-12-22 11:56:59.457186302 -0800
> @@ -39,9 +39,6 @@ int cmdline_find_option_bool(const char
>  	if (!cmdline)
>  		return -1;      /* No command line */
>  
> -	if (!strlen(cmdline))
> -		return 0;
> -

Patch 1 adds the strlen(), this patch removes it. Please merge both patches.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

Re: [PATCH 3/5] x86: simplify early command line parsing

[Dave Hansen]

On 01/06/2016 09:10 AM, Borislav Petkov wrote:
>> > diff -puN arch/x86/lib/cmdline.c~x86-early-command-line-non-term arch/x86/lib/cmdline.c
>> > --- a/arch/x86/lib/cmdline.c~x86-early-command-line-non-term	2015-12-22 11:56:59.454186167 -0800
>> > +++ b/arch/x86/lib/cmdline.c	2015-12-22 11:56:59.457186302 -0800
>> > @@ -39,9 +39,6 @@ int cmdline_find_option_bool(const char
>> >  	if (!cmdline)
>> >  		return -1;      /* No command line */
>> >  
>> > -	if (!strlen(cmdline))
>> > -		return 0;
>> > -
> Patch 1 adds the strlen(), this patch removes it. Please merge both patches.

Yes, it adds a line that uses strlen.  But, there was already the use in
the min_t() "call":

> -	len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);
> -	if (!len)
> +	if (!strlen(cmdline))
>  		return 0;

I wanted to separate the two things because they really fix two separate
issues.  I also want to ensure that any problems that this patch causes
can be isolated to the smallest change possible.

Re: [PATCH 3/5] x86: simplify early command line parsing

[Dave Hansen]

On 01/06/2016 09:10 AM, Borislav Petkov wrote:
>> > -	if (!strlen(cmdline))
>> > -		return 0;
>> > -
> Patch 1 adds the strlen(), this patch removes it. Please merge both patches.

As I mentioned, it doesn't strictly add it.

Plus, if I go add this back to that patch, I'll end up having to paste
most of the changelog in to that one.  I think it's much more clear to
have this hunk live on its own.

Re: [PATCH 3/5] x86: simplify early command line parsing

[Borislav Petkov]

On Wed, Jan 06, 2016 at 09:37:40AM -0800, Dave Hansen wrote:
> On 01/06/2016 09:10 AM, Borislav Petkov wrote:
> >> > -	if (!strlen(cmdline))
> >> > -		return 0;
> >> > -
> > Patch 1 adds the strlen(), this patch removes it. Please merge both patches.
> 
> As I mentioned, it doesn't strictly add it.
> 
> Plus, if I go add this back to that patch, I'll end up having to paste
> most of the changelog in to that one.  I think it's much more clear to
> have this hunk live on its own.

So why not leave the min_t:

	maxlen = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);

and then do:

	while (pos < maxlen)

?

This way it is absolutely clear what's going on.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

Re: [PATCH 1/5] x86: fix early command-line parsing when matching at end

[Dave Hansen]

Moving over to the actual patch we're talking about...

On 12/22/2015 02:52 PM, Dave Hansen wrote:
> @@ -37,11 +39,14 @@ int cmdline_find_option_bool(const char
>  	if (!cmdline)
>  		return -1;      /* No command line */
>  
> -	len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);
> -	if (!len)
> +	if (!strlen(cmdline))
>  		return 0;
>  
> -	while (len--) {
> +	/*
> +	 * This 'pos' check ensures we do not overrun
> +	 * a non-NULL-terminated 'cmdline'
> +	 */
> +	while (pos < COMMAND_LINE_SIZE) {

Borislav says:
>> So why not leave the min_t:
>> 
>> 	maxlen = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);
>> 
>> and then do:
>> 
>> 	while (pos < maxlen)

That works, and it's functionally equivalent to what I have (I think).
I like what I have because it separates the 'strlen' checking from the
COMMAND_LINE_SIZE checking, which makes it super duper obvious that the
third patch here is OK.

So, after the third patch, the strlen() goes away any way you do this.
The code ends up looking the same (the while() check is against the
max-length variable alone).

I'm happy to rewrite this to have a different intermediate form and
repost the thing, but the end result will be the same.

Re: [PATCH 1/5] x86: fix early command-line parsing when matching at end

[Borislav Petkov]

On Wed, Jan 06, 2016 at 09:57:08AM -0800, Dave Hansen wrote:
> So, after the third patch, the strlen() goes away any way you do this.
> The code ends up looking the same (the while() check is against the
> max-length variable alone).

True story.

> I'm happy to rewrite this to have a different intermediate form and
> repost the thing, but the end result will be the same.

Yeah, no need.

Thanks.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

Re: [PATCH 5/5] x86: test early command-line code

[Borislav Petkov]

On Tue, Dec 22, 2015 at 02:52:44PM -0800, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> Here are some simple tests for the early command-line code.  It
> had way more bugs than it should have, so let's make sure they
> never pop up again.
> 
> Note, there are a few failures in here now.  We will fix those
> up in the next few patches.
> 
> This is complete overkill for this code, but I had to do it to
> convince myself that I wasn't making it any worse.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: fenghua.yu@intel.com
> Cc: yu-cheng.yu@intel.com
> ---
> 
>  b/arch/x86/Kconfig.debug  |    7 ++
>  b/arch/x86/kernel/check.c |    1 
>  b/arch/x86/kernel/setup.c |    9 +++
>  b/arch/x86/lib/cmdline.c  |  122 ++++++++++++++++++++++++++++++++++++++++++++++

First 4 applied, thanks.

This one belongs into tools/testing/selftests/x86/, AFAICT, and can be
run in userspace just the same.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

[tip:x86/boot] x86/boot: Fix early command-line parsing when matching at end

[tip-bot for Dave Hansen]

Commit-ID:  02afeaae9843733a39cd9b11053748b2d1dc5ae7
Gitweb:     http://git.kernel.org/tip/02afeaae9843733a39cd9b11053748b2d1dc5ae7
Author:     Dave Hansen <dave.hansen@linux.intel.com>
AuthorDate: Tue, 22 Dec 2015 14:52:38 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 3 Feb 2016 12:03:15 +0100

x86/boot: Fix early command-line parsing when matching at end

The x86 early command line parsing in cmdline_find_option_bool() is
buggy. If it matches a specified 'option' all the way to the end of the
command-line, it will consider it a match.

For instance,

  cmdline = "foo";
  cmdline_find_option_bool(cmdline, "fool");

will return 1. This is particularly annoying since we have actual FPU
options like "noxsave" and "noxsaves" So, command-line "foo bar noxsave"
will match *BOTH* a "noxsave" and "noxsaves". (This turns out not to be
an actual problem because "noxsave" implies "noxsaves", but it's still
confusing.)

To fix this, we simplify the code and stop tracking 'len'. 'len'
was trying to indicate either the NULL terminator *OR* the end of a
non-NULL-terminated command line at 'COMMAND_LINE_SIZE'. But, each of the
three states is *already* checking 'cmdline' for a NULL terminator.

We _only_ need to check if we have overrun 'COMMAND_LINE_SIZE', and that
we can do without keeping 'len' around.

Also add some commends to clarify what is going on.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
Link: http://lkml.kernel.org/r/20151222225238.9AEB560C@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/lib/cmdline.c | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index 422db00..49548be 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -21,12 +21,14 @@ 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)
 {
 	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 +39,14 @@ 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)
+	if (!strlen(cmdline))
 		return 0;
 
-	while (len--) {
+	/*
+	 * This 'pos' check ensures we do not overrun
+	 * a non-NULL-terminated 'cmdline'
+	 */
+	while (pos < COMMAND_LINE_SIZE) {
 		c = *(char *)cmdline++;
 		pos++;
 
@@ -58,17 +63,26 @@ 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)
+			} else if (!c) {
+				/*
+				 * Hit the NULL terminator on the end of
+				 * cmdline.
+				 */
 				return 0;
-			else if (c != *opptr++)
+			} else if (c != *opptr++) {
 				state = st_wordskip;
-			else if (!len)		/* last word and is matching */
-				return wstart;
+			}
 			break;
 
 		case st_wordskip:

[tip:x86/boot] x86/boot: Fix early command-line parsing when partial word matches

[tip-bot for Dave Hansen]

Commit-ID:  abcdc1c694fa4055323cbec1cde4c2cb6b68398c
Gitweb:     http://git.kernel.org/tip/abcdc1c694fa4055323cbec1cde4c2cb6b68398c
Author:     Dave Hansen <dave.hansen@linux.intel.com>
AuthorDate: Tue, 22 Dec 2015 14:52:39 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 3 Feb 2016 12:03:16 +0100

x86/boot: Fix early command-line parsing when partial word matches

cmdline_find_option_bool() keeps track of position in two strings:

 1. the command-line
 2. the option we are searchign for in the command-line

We plow through each character in the command-line one at a time, always
moving forward. We move forward in the option ('opptr') when we match
characters in 'cmdline'. We reset the 'opptr' only when we go in to the
'st_wordstart' state.

But, if we fail to match an option because we see a space
(state=st_wordcmp, *opptr='\0',c=' '), we set state='st_wordskip' and
'break', moving to the next character. But, that move to the next
character is the one *after* the ' '. This means that we will miss a
'st_wordstart' state.

For instance, if we have

  cmdline = "foo fool";

and are searching for "fool", we have:

	  "fool"
  opptr = ----^

           "foo fool"
   c = --------^

We see that 'l' != ' ', set state=st_wordskip, break, and then move 'c', so:

          "foo fool"
  c = ---------^

and are still in state=st_wordskip. We will stay in wordskip until we
have skipped "fool", thus missing the option we were looking for. This
*only* happens when you have a partially- matching word followed by a
matching one.

To fix this, we always fall *into* the 'st_wordskip' state when we set
it.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
Link: http://lkml.kernel.org/r/20151222225239.8E1DCA58@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/lib/cmdline.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index 49548be..ff8d1be 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -72,18 +72,26 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 				 */
 				if (!c || myisspace(c))
 					return wstart;
-				else
-					state = st_wordskip;
+				/*
+				 * 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 (c == *opptr++) {
+				/*
+				 * We are currently matching, so continue
+				 * to the next character on the cmdline.
+				 */
+				break;
 			}
-			break;
+			state = st_wordskip;
+			/* fall through */
 
 		case st_wordskip:
 			if (!c)

[tip:x86/boot] x86/boot: Simplify early command line parsing

[tip-bot for Dave Hansen]

Commit-ID:  4de07ea481361b08fe13735004dafae862482d38
Gitweb:     http://git.kernel.org/tip/4de07ea481361b08fe13735004dafae862482d38
Author:     Dave Hansen <dave.hansen@linux.intel.com>
AuthorDate: Tue, 22 Dec 2015 14:52:41 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 3 Feb 2016 12:03:17 +0100

x86/boot: Simplify early command line parsing

__cmdline_find_option_bool() tries to account for both NULL-terminated
and non-NULL-terminated strings. It keeps 'pos' to look for the end of
the buffer and also looks for '!c' in a bunch of places to look for NULL
termination.

But, it also calls strlen(). You can't call strlen on a
non-NULL-terminated string.

If !strlen(cmdline), then cmdline[0]=='\0'. In that case, we will go in
to the while() loop, set c='\0', hit st_wordstart, notice !c, and will
immediately return 0.

So, remove the strlen().  It is unnecessary and unsafe.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
Link: http://lkml.kernel.org/r/20151222225241.15365E43@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/lib/cmdline.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index ff8d1be..945a639 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -39,9 +39,6 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 	if (!cmdline)
 		return -1;      /* No command line */
 
-	if (!strlen(cmdline))
-		return 0;
-
 	/*
 	 * This 'pos' check ensures we do not overrun
 	 * a non-NULL-terminated 'cmdline'

[tip:x86/boot] x86/boot: Pass in size to early cmdline parsing

[tip-bot for Dave Hansen]

Commit-ID:  8c0517759a1a100a8b83134cf3c7f254774aaeba
Gitweb:     http://git.kernel.org/tip/8c0517759a1a100a8b83134cf3c7f254774aaeba
Author:     Dave Hansen <dave.hansen@linux.intel.com>
AuthorDate: Tue, 22 Dec 2015 14:52:43 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 3 Feb 2016 12:03:18 +0100

x86/boot: Pass in size to early cmdline parsing

We will use this in a few patches to implement tests for early parsing.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
[ Aligned args properly. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Cc: yu-cheng.yu@intel.com
Link: http://lkml.kernel.org/r/20151222225243.5CC47EB6@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/lib/cmdline.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index 945a639..5cc78bf 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -25,7 +25,9 @@ static inline int myisspace(u8 c)
  * 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 pos = 0, wstart = 0;
@@ -43,7 +45,7 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 	 * This 'pos' check ensures we do not overrun
 	 * a non-NULL-terminated 'cmdline'
 	 */
-	while (pos < COMMAND_LINE_SIZE) {
+	while (pos < max_cmdline_size) {
 		c = *(char *)cmdline++;
 		pos++;
 
@@ -101,3 +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);
+}