taint: Add TAINT_FWCTL

Requesting a fwctl scope of access that includes mutating device debug
data will cause the kernel to be tainted. Changing the device operation
through things in the debug scope may cause the device to malfunction in
undefined ways. This should be reflected in the TAINT flags to help any
debuggers understand that something has been done.

Link: https://patch.msgid.link/r/[email protected]
Reviewed-by: Jonathan Cameron <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
Reviewed-by: Shannon Nelson <[email protected]>
Tested-by: Dave Jiang <[email protected]>
Tested-by: Shannon Nelson <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: jgunthorpe

Documentation/admin-guide/tainted-kernels.rst

@@ -101,6 +101,7 @@ Bit  Log  Number  Reason that got the kernel tainted
  16  _/X   65536  auxiliary taint, defined for and used by distros
  17  _/T  131072  kernel was built with the struct randomization plugin
  18  _/N  262144  an in-kernel test has been run
+ 19  _/J  524288  userspace used a mutating debug operation in fwctl
 ===  ===  ======  ========================================================
 
 Note: The character ``_`` is representing a blank in this table to make reading
@@ -184,3 +185,7 @@ More detailed explanation for tainting
      build time.
 
  18) ``N`` if an in-kernel test, such as a KUnit test, has been run.
+
+ 19) ``J`` if userpace opened /dev/fwctl/* and performed a FWTCL_RPC_DEBUG_WRITE
+     to use the devices debugging features. Device debugging features could
+     cause the device to malfunction in undefined ways.

include/linux/panic.h

@@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout)
 #define TAINT_AUX			16
 #define TAINT_RANDSTRUCT		17
 #define TAINT_TEST			18
-#define TAINT_FLAGS_COUNT		19
+#define TAINT_FWCTL			19
+#define TAINT_FLAGS_COUNT		20
 #define TAINT_FLAGS_MAX			((1UL << TAINT_FLAGS_COUNT) - 1)
 
 struct taint_flag {

kernel/panic.c

@@ -511,6 +511,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
 	TAINT_FLAG(AUX,				'X', ' ', true),
 	TAINT_FLAG(RANDSTRUCT,			'T', ' ', true),
 	TAINT_FLAG(TEST,			'N', ' ', true),
+	TAINT_FLAG(FWCTL,			'J', ' ', true),
 };
 
 #undef TAINT_FLAG

tools/debugging/kernel-chktaint

@@ -204,6 +204,14 @@ else
 	echo " * an in-kernel test (such as a KUnit test) has been run (#18)"
 fi
 
+T=`expr $T / 2`
+if [ `expr $T % 2` -eq 0 ]; then
+	addout " "
+else
+	addout "J"
+	echo " * fwctl's mutating debug interface was used (#19)"
+fi
+
 echo "For a more detailed explanation of the various taint flags see"
 echo " Documentation/admin-guide/tainted-kernels.rst in the Linux kernel sources"
 echo " or https://kernel.org/doc/html/latest/admin-guide/tainted-kernels.html"