commit bf616d21f41174389c6d720ae21bf40f154474c8
author David Howells <dhowells@redhat.com> Tue Apr 04 16:54:21 2017 +0100
committer David Howells <dhowells@redhat.com> Tue Apr 04 16:54:21 2017 +0100
tree ad57e44f77343fbfa31a368bffa0db97f8591e65
parent ddb99e118e37f324a4be65a411bb60ae62795cf9

Annotate module params that specify hardware parameters (eg. ioport)

Provided an annotation for module parameters that specify hardware
parameters (such as io ports, iomem addresses, irqs, dma channels, fixed
dma buffers and other types).

This will enable such parameters to be locked down in the core parameter
parser for secure boot support.

I've also included annotations as to what sort of hardware configuration
each module is dealing with for future use.  Some of these are
straightforward (ioport, iomem, irq, dma), but there are also:

 (1) drivers that switch the semantics of a parameter between ioport and
     iomem depending on a second parameter,

 (2) drivers that appear to reserve a CPU memory buffer at a fixed address,

 (3) other parameters, such as bus types and irq selection bitmasks.

For the moment, the hardware configuration type isn't actually stored,
though its validity is checked.

Signed-off-by: David Howells <dhowells@redhat.com>

include/linux/moduleparam.h

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 52666d9..6be1949 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -60,9 +60,11 @@
  * Flags available for kernel_param
  *
  * UNSAFE - the parameter is dangerous and setting it will taint the kernel
+ * HWPARAM - Hardware param not permitted in lockdown mode
  */
 enum {
-	KERNEL_PARAM_FL_UNSAFE = (1 << 0)
+	KERNEL_PARAM_FL_UNSAFE	= (1 << 0),
+	KERNEL_PARAM_FL_HWPARAM	= (1 << 1),
 };
 
 struct kernel_param {
@@ -451,6 +453,67 @@
 			    perm, -1, 0);				\
 	__MODULE_PARM_TYPE(name, "array of " #type)
 
+enum hwparam_type {
+	hwparam_ioport,		/* Module parameter configures an I/O port */
+	hwparam_iomem,		/* Module parameter configures an I/O mem address */
+	hwparam_ioport_or_iomem, /* Module parameter could be either, depending on other option */
+	hwparam_irq,		/* Module parameter configures an I/O port */
+	hwparam_dma,		/* Module parameter configures a DMA channel */
+	hwparam_dma_addr,	/* Module parameter configures a DMA buffer address */
+	hwparam_other,		/* Module parameter configures some other value */
+};
+
+/**
+ * module_param_hw_named - A parameter representing a hw parameters
+ * @name: a valid C identifier which is the parameter name.
+ * @value: the actual lvalue to alter.
+ * @type: the type of the parameter
+ * @hwtype: what the value represents (enum hwparam_type)
+ * @perm: visibility in sysfs.
+ *
+ * Usually it's a good idea to have variable names and user-exposed names the
+ * same, but that's harder if the variable must be non-static or is inside a
+ * structure.  This allows exposure under a different name.
+ */
+#define module_param_hw_named(name, value, type, hwtype, perm)		\
+	param_check_##type(name, &(value));				\
+	__module_param_call(MODULE_PARAM_PREFIX, name,			\
+			    &param_ops_##type, &value,			\
+			    perm, -1,					\
+			    KERNEL_PARAM_FL_HWPARAM | (hwparam_##hwtype & 0));	\
+	__MODULE_PARM_TYPE(name, #type)
+
+#define module_param_hw(name, type, hwtype, perm)		\
+	module_param_hw_named(name, name, type, hwtype, perm)
+
+/**
+ * module_param_hw_array - A parameter representing an array of hw parameters
+ * @name: the name of the array variable
+ * @type: the type, as per module_param()
+ * @hwtype: what the value represents (enum hwparam_type)
+ * @nump: optional pointer filled in with the number written
+ * @perm: visibility in sysfs
+ *
+ * Input and output are as comma-separated values.  Commas inside values
+ * don't work properly (eg. an array of charp).
+ *
+ * ARRAY_SIZE(@name) is used to determine the number of elements in the
+ * array, so the definition must be visible.
+ */
+#define module_param_hw_array(name, type, hwtype, nump, perm)		\
+	param_check_##type(name, &(name)[0]);				\
+	static const struct kparam_array __param_arr_##name		\
+	= { .max = ARRAY_SIZE(name), .num = nump,			\
+	    .ops = &param_ops_##type,					\
+	    .elemsize = sizeof(name[0]), .elem = name };		\
+	__module_param_call(MODULE_PARAM_PREFIX, name,			\
+			    &param_array_ops,				\
+			    .arr = &__param_arr_##name,			\
+			    perm, -1,					\
+			    KERNEL_PARAM_FL_HWPARAM | (hwparam_##hwtype & 0));	\
+	__MODULE_PARM_TYPE(name, "array of " #type)
+
+
 extern const struct kernel_param_ops param_array_ops;
 
 extern const struct kernel_param_ops param_ops_string;