[PATCH 04/10] misc: lkdtm: bugs: At least try to use popuated variable

[Lee Jones]

The result may not be intereresting, but not using a set variable
is bad form and causes W=1 kernel builds to complain.

Fixes the following W=1 warning(s):

 drivers/misc/lkdtm/bugs.c: In function ‘lkdtm_STACK_GUARD_PAGE_LEADING’:
 drivers/misc/lkdtm/bugs.c:331:25: warning: variable ‘byte’ set but not used [-Wunused-but-set-variable]
 331 | volatile unsigned char byte;
 | ^~~~
 drivers/misc/lkdtm/bugs.c: In function ‘lkdtm_STACK_GUARD_PAGE_TRAILING’:
 drivers/misc/lkdtm/bugs.c:345:25: warning: variable ‘byte’ set but not used [-Wunused-but-set-variable]
 345 | volatile unsigned char byte;
 | ^~~~

Cc: Kees Cook <keescook at chromium.org>
Signed-off-by: Lee Jones <lee.jones at linaro.org>
---
 drivers/misc/lkdtm/bugs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index 736675f0a2464..4f94296fc58ad 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -334,7 +334,7 @@ void lkdtm_STACK_GUARD_PAGE_LEADING(void)
 
 	byte = *ptr;
 
-	pr_err("FAIL: accessed page before stack!\n");
+	pr_err("FAIL: accessed page before stack! (byte: %x)\n", byte);
 }
 
 /* Test that VMAP_STACK is actually allocating with a trailing guard page */
@@ -348,7 +348,7 @@ void lkdtm_STACK_GUARD_PAGE_TRAILING(void)
 
 	byte = *ptr;
 
-	pr_err("FAIL: accessed page after stack!\n");
+	pr_err("FAIL: accessed page after stack! (byte: %x)\n", byte);
 }
 
 void lkdtm_UNSET_SMEP(void)
-- 
2.25.1