Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 478 insertions, 0 deletions

diff --git a/lib/packing.c b/lib/packing.c
new file mode 100644
index 000000000..bb1643d9e
--- /dev/null
+++ b/lib/packing.c
@@ -0,0 +1,478 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/* Copyright 2016-2018 NXP
+ * Copyright (c) 2018-2019, Vladimir Oltean <olteanv@gmail.com>
+ */
+#include <linux/packing.h>
+#include <linux/module.h>
+#include <linux/bitops.h>
+#include <linux/bits.h>
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/bitrev.h>
+
+#define __pack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks)	\
+	({									\
+		for (size_t i = 0; i < (num_fields); i++) {			\
+			typeof(&(fields)[0]) field = &(fields)[i];		\
+			u64 uval;						\
+										\
+			uval = ustruct_field_to_u64(ustruct, field->offset, field->size); \
+										\
+			__pack(pbuf, uval, field->startbit, field->endbit,	\
+			       pbuflen, quirks);				\
+		}								\
+	})
+
+#define __unpack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks)	\
+	({									\
+		for (size_t i = 0; i < (num_fields); i++) {			\
+			typeof(&(fields)[0]) field = &fields[i];		\
+			u64 uval;						\
+										\
+			__unpack(pbuf, &uval, field->startbit, field->endbit,	\
+				 pbuflen, quirks);				\
+										\
+			u64_to_ustruct_field(ustruct, field->offset, field->size, uval); \
+		}								\
+	})
+
+/**
+ * calculate_box_addr - Determine physical location of byte in buffer
+ * @box: Index of byte within buffer seen as a logical big-endian big number
+ * @len: Size of buffer in bytes
+ * @quirks: mask of QUIRK_LSW32_IS_FIRST and QUIRK_LITTLE_ENDIAN
+ *
+ * Function interprets the buffer as a @len byte sized big number, and returns
+ * the physical offset of the @box logical octet within it. Internally, it
+ * treats the big number as groups of 4 bytes. If @len is not a multiple of 4,
+ * the last group may be shorter.
+ *
+ * @QUIRK_LSW32_IS_FIRST gives the ordering of groups of 4 octets relative to
+ * each other. If set, the most significant group of 4 octets is last in the
+ * buffer (and may be truncated if @len is not a multiple of 4).
+ *
+ * @QUIRK_LITTLE_ENDIAN gives the ordering of bytes within each group of 4.
+ * If set, the most significant byte is last in the group. If @len takes the
+ * form of 4k+3, the last group will only be able to represent 24 bits, and its
+ * most significant octet is byte 2.
+ *
+ * Return: the physical offset into the buffer corresponding to the logical box.
+ */
+static size_t calculate_box_addr(size_t box, size_t len, u8 quirks)
+{
+	size_t offset_of_group, offset_in_group, this_group = box / 4;
+	size_t group_size;
+
+	if (quirks & QUIRK_LSW32_IS_FIRST)
+		offset_of_group = this_group * 4;
+	else
+		offset_of_group = len - ((this_group + 1) * 4);
+
+	group_size = min(4, len - offset_of_group);
+
+	if (quirks & QUIRK_LITTLE_ENDIAN)
+		offset_in_group = box - this_group * 4;
+	else
+		offset_in_group = group_size - (box - this_group * 4) - 1;
+
+	return offset_of_group + offset_in_group;
+}
+
+static void __pack(void *pbuf, u64 uval, size_t startbit, size_t endbit,
+		   size_t pbuflen, u8 quirks)
+{
+	/* Logical byte indices corresponding to the
+	 * start and end of the field.
+	 */
+	int plogical_first_u8 = startbit / BITS_PER_BYTE;
+	int plogical_last_u8 = endbit / BITS_PER_BYTE;
+	int value_width = startbit - endbit + 1;
+	int box;
+
+	/* Check if "uval" fits in "value_width" bits.
+	 * The test only works for value_width < 64, but in the latter case,
+	 * any 64-bit uval will surely fit.
+	 */
+	WARN(value_width < 64 && uval >= (1ull << value_width),
+	     "Cannot store 0x%llx inside bits %zu-%zu - will truncate\n",
+	     uval, startbit, endbit);
+
+	/* Iterate through an idealistic view of the pbuf as an u64 with
+	 * no quirks, u8 by u8 (aligned at u8 boundaries), from high to low
+	 * logical bit significance. "box" denotes the current logical u8.
+	 */
+	for (box = plogical_first_u8; box >= plogical_last_u8; box--) {
+		/* Bit indices into the currently accessed 8-bit box */
+		size_t box_start_bit, box_end_bit, box_addr;
+		u8  box_mask;
+		/* Corresponding bits from the unpacked u64 parameter */
+		size_t proj_start_bit, proj_end_bit;
+		u64 proj_mask;
+		u64 pval;
+
+		/* This u8 may need to be accessed in its entirety
+		 * (from bit 7 to bit 0), or not, depending on the
+		 * input arguments startbit and endbit.
+		 */
+		if (box == plogical_first_u8)
+			box_start_bit = startbit % BITS_PER_BYTE;
+		else
+			box_start_bit = 7;
+		if (box == plogical_last_u8)
+			box_end_bit = endbit % BITS_PER_BYTE;
+		else
+			box_end_bit = 0;
+
+		/* We have determined the box bit start and end.
+		 * Now we calculate where this (masked) u8 box would fit
+		 * in the unpacked (CPU-readable) u64 - the u8 box's
+		 * projection onto the unpacked u64. Though the
+		 * box is u8, the projection is u64 because it may fall
+		 * anywhere within the unpacked u64.
+		 */
+		proj_start_bit = ((box * BITS_PER_BYTE) + box_start_bit) - endbit;
+		proj_end_bit = ((box * BITS_PER_BYTE) + box_end_bit) - endbit;
+		proj_mask = GENMASK_ULL(proj_start_bit, proj_end_bit);
+		box_mask = GENMASK(box_start_bit, box_end_bit);
+
+		/* Determine the offset of the u8 box inside the pbuf,
+		 * adjusted for quirks. The adjusted box_addr will be used for
+		 * effective addressing inside the pbuf (so it's not
+		 * logical any longer).
+		 */
+		box_addr = calculate_box_addr(box, pbuflen, quirks);
+
+		/* Write to pbuf, read from uval */
+		pval = uval & proj_mask;
+		pval >>= proj_end_bit;
+		pval <<= box_end_bit;
+
+		if (quirks & QUIRK_MSB_ON_THE_RIGHT) {
+			pval = bitrev8(pval);
+			box_mask = bitrev8(box_mask);
+		}
+
+		((u8 *)pbuf)[box_addr] &= ~box_mask;
+		((u8 *)pbuf)[box_addr] |= pval;
+	}
+}
+
+/**
+ * pack - Pack u64 number into bitfield of buffer.
+ *
+ * @pbuf: Pointer to a buffer holding the packed value.
+ * @uval: CPU-readable unpacked value to pack.
+ * @startbit: The index (in logical notation, compensated for quirks) where
+ *	      the packed value starts within pbuf. Must be larger than, or
+ *	      equal to, endbit.
+ * @endbit: The index (in logical notation, compensated for quirks) where
+ *	    the packed value ends within pbuf. Must be smaller than, or equal
+ *	    to, startbit.
+ * @pbuflen: The length in bytes of the packed buffer pointed to by @pbuf.
+ * @quirks: A bit mask of QUIRK_LITTLE_ENDIAN, QUIRK_LSW32_IS_FIRST and
+ *	    QUIRK_MSB_ON_THE_RIGHT.
+ *
+ * Return: 0 on success, EINVAL or ERANGE if called incorrectly. Assuming
+ *	   correct usage, return code may be discarded. The @pbuf memory will
+ *	   be modified on success.
+ */
+int pack(void *pbuf, u64 uval, size_t startbit, size_t endbit, size_t pbuflen,
+	 u8 quirks)
+{
+	/* startbit is expected to be larger than endbit, and both are
+	 * expected to be within the logically addressable range of the buffer.
+	 */
+	if (unlikely(startbit < endbit || startbit >= BITS_PER_BYTE * pbuflen))
+		/* Invalid function call */
+		return -EINVAL;
+
+	if (unlikely(startbit - endbit >= 64))
+		return -ERANGE;
+
+	__pack(pbuf, uval, startbit, endbit, pbuflen, quirks);
+
+	return 0;
+}
+EXPORT_SYMBOL(pack);
+
+static void __unpack(const void *pbuf, u64 *uval, size_t startbit, size_t endbit,
+		     size_t pbuflen, u8 quirks)
+{
+	/* Logical byte indices corresponding to the
+	 * start and end of the field.
+	 */
+	int plogical_first_u8 = startbit / BITS_PER_BYTE;
+	int plogical_last_u8 = endbit / BITS_PER_BYTE;
+	int box;
+
+	/* Initialize parameter */
+	*uval = 0;
+
+	/* Iterate through an idealistic view of the pbuf as an u64 with
+	 * no quirks, u8 by u8 (aligned at u8 boundaries), from high to low
+	 * logical bit significance. "box" denotes the current logical u8.
+	 */
+	for (box = plogical_first_u8; box >= plogical_last_u8; box--) {
+		/* Bit indices into the currently accessed 8-bit box */
+		size_t box_start_bit, box_end_bit, box_addr;
+		u8  box_mask;
+		/* Corresponding bits from the unpacked u64 parameter */
+		size_t proj_start_bit, proj_end_bit;
+		u64 proj_mask;
+		u64 pval;
+
+		/* This u8 may need to be accessed in its entirety
+		 * (from bit 7 to bit 0), or not, depending on the
+		 * input arguments startbit and endbit.
+		 */
+		if (box == plogical_first_u8)
+			box_start_bit = startbit % BITS_PER_BYTE;
+		else
+			box_start_bit = 7;
+		if (box == plogical_last_u8)
+			box_end_bit = endbit % BITS_PER_BYTE;
+		else
+			box_end_bit = 0;
+
+		/* We have determined the box bit start and end.
+		 * Now we calculate where this (masked) u8 box would fit
+		 * in the unpacked (CPU-readable) u64 - the u8 box's
+		 * projection onto the unpacked u64. Though the
+		 * box is u8, the projection is u64 because it may fall
+		 * anywhere within the unpacked u64.
+		 */
+		proj_start_bit = ((box * BITS_PER_BYTE) + box_start_bit) - endbit;
+		proj_end_bit = ((box * BITS_PER_BYTE) + box_end_bit) - endbit;
+		proj_mask = GENMASK_ULL(proj_start_bit, proj_end_bit);
+		box_mask = GENMASK(box_start_bit, box_end_bit);
+
+		/* Determine the offset of the u8 box inside the pbuf,
+		 * adjusted for quirks. The adjusted box_addr will be used for
+		 * effective addressing inside the pbuf (so it's not
+		 * logical any longer).
+		 */
+		box_addr = calculate_box_addr(box, pbuflen, quirks);
+
+		/* Read from pbuf, write to uval */
+		pval = ((u8 *)pbuf)[box_addr];
+
+		if (quirks & QUIRK_MSB_ON_THE_RIGHT)
+			pval = bitrev8(pval);
+
+		pval &= box_mask;
+
+		pval >>= box_end_bit;
+		pval <<= proj_end_bit;
+		*uval &= ~proj_mask;
+		*uval |= pval;
+	}
+}
+
+/**
+ * unpack - Unpack u64 number from packed buffer.
+ *
+ * @pbuf: Pointer to a buffer holding the packed value.
+ * @uval: Pointer to an u64 holding the unpacked value.
+ * @startbit: The index (in logical notation, compensated for quirks) where
+ *	      the packed value starts within pbuf. Must be larger than, or
+ *	      equal to, endbit.
+ * @endbit: The index (in logical notation, compensated for quirks) where
+ *	    the packed value ends within pbuf. Must be smaller than, or equal
+ *	    to, startbit.
+ * @pbuflen: The length in bytes of the packed buffer pointed to by @pbuf.
+ * @quirks: A bit mask of QUIRK_LITTLE_ENDIAN, QUIRK_LSW32_IS_FIRST and
+ *	    QUIRK_MSB_ON_THE_RIGHT.
+ *
+ * Return: 0 on success, EINVAL or ERANGE if called incorrectly. Assuming
+ *	   correct usage, return code may be discarded. The @uval will be
+ *	   modified on success.
+ */
+int unpack(const void *pbuf, u64 *uval, size_t startbit, size_t endbit,
+	   size_t pbuflen, u8 quirks)
+{
+	/* width of the field to access in the pbuf */
+	u64 value_width;
+
+	/* startbit is expected to be larger than endbit, and both are
+	 * expected to be within the logically addressable range of the buffer.
+	 */
+	if (startbit < endbit || startbit >= BITS_PER_BYTE * pbuflen)
+		/* Invalid function call */
+		return -EINVAL;
+
+	value_width = startbit - endbit + 1;
+	if (value_width > 64)
+		return -ERANGE;
+
+	__unpack(pbuf, uval, startbit, endbit, pbuflen, quirks);
+
+	return 0;
+}
+EXPORT_SYMBOL(unpack);
+
+/**
+ * packing - Convert numbers (currently u64) between a packed and an unpacked
+ *	     format. Unpacked means laid out in memory in the CPU's native
+ *	     understanding of integers, while packed means anything else that
+ *	     requires translation.
+ *
+ * @pbuf: Pointer to a buffer holding the packed value.
+ * @uval: Pointer to an u64 holding the unpacked value.
+ * @startbit: The index (in logical notation, compensated for quirks) where
+ *	      the packed value starts within pbuf. Must be larger than, or
+ *	      equal to, endbit.
+ * @endbit: The index (in logical notation, compensated for quirks) where
+ *	    the packed value ends within pbuf. Must be smaller than, or equal
+ *	    to, startbit.
+ * @pbuflen: The length in bytes of the packed buffer pointed to by @pbuf.
+ * @op: If PACK, then uval will be treated as const pointer and copied (packed)
+ *	into pbuf, between startbit and endbit.
+ *	If UNPACK, then pbuf will be treated as const pointer and the logical
+ *	value between startbit and endbit will be copied (unpacked) to uval.
+ * @quirks: A bit mask of QUIRK_LITTLE_ENDIAN, QUIRK_LSW32_IS_FIRST and
+ *	    QUIRK_MSB_ON_THE_RIGHT.
+ *
+ * Note: this is deprecated, prefer to use pack() or unpack() in new code.
+ *
+ * Return: 0 on success, EINVAL or ERANGE if called incorrectly. Assuming
+ *	   correct usage, return code may be discarded.
+ *	   If op is PACK, pbuf is modified.
+ *	   If op is UNPACK, uval is modified.
+ */
+int packing(void *pbuf, u64 *uval, int startbit, int endbit, size_t pbuflen,
+	    enum packing_op op, u8 quirks)
+{
+	if (op == PACK)
+		return pack(pbuf, *uval, startbit, endbit, pbuflen, quirks);
+
+	return unpack(pbuf, uval, startbit, endbit, pbuflen, quirks);
+}
+EXPORT_SYMBOL(packing);
+
+static u64 ustruct_field_to_u64(const void *ustruct, size_t field_offset,
+				size_t field_size)
+{
+	switch (field_size) {
+	case 1:
+		return *((u8 *)(ustruct + field_offset));
+	case 2:
+		return *((u16 *)(ustruct + field_offset));
+	case 4:
+		return *((u32 *)(ustruct + field_offset));
+	default:
+		return *((u64 *)(ustruct + field_offset));
+	}
+}
+
+static void u64_to_ustruct_field(void *ustruct, size_t field_offset,
+				 size_t field_size, u64 uval)
+{
+	switch (field_size) {
+	case 1:
+		*((u8 *)(ustruct + field_offset)) = uval;
+		break;
+	case 2:
+		*((u16 *)(ustruct + field_offset)) = uval;
+		break;
+	case 4:
+		*((u32 *)(ustruct + field_offset)) = uval;
+		break;
+	default:
+		*((u64 *)(ustruct + field_offset)) = uval;
+		break;
+	}
+}
+
+/**
+ * pack_fields_u8 - Pack array of fields
+ *
+ * @pbuf: Pointer to a buffer holding the packed value.
+ * @pbuflen: The length in bytes of the packed buffer pointed to by @pbuf.
+ * @ustruct: Pointer to CPU-readable structure holding the unpacked value.
+ *	     It is expected (but not checked) that this has the same data type
+ *	     as all struct packed_field_u8 definitions.
+ * @fields: Array of packed_field_u8 field definition. They must not overlap.
+ * @num_fields: Length of @fields array.
+ * @quirks: A bit mask of QUIRK_LITTLE_ENDIAN, QUIRK_LSW32_IS_FIRST and
+ *	    QUIRK_MSB_ON_THE_RIGHT.
+ *
+ * Use the pack_fields() macro instead of calling this directly.
+ */
+void pack_fields_u8(void *pbuf, size_t pbuflen, const void *ustruct,
+		    const struct packed_field_u8 *fields, size_t num_fields,
+		    u8 quirks)
+{
+	__pack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks);
+}
+EXPORT_SYMBOL(pack_fields_u8);
+
+/**
+ * pack_fields_u16 - Pack array of fields
+ *
+ * @pbuf: Pointer to a buffer holding the packed value.
+ * @pbuflen: The length in bytes of the packed buffer pointed to by @pbuf.
+ * @ustruct: Pointer to CPU-readable structure holding the unpacked value.
+ *	     It is expected (but not checked) that this has the same data type
+ *	     as all struct packed_field_u16 definitions.
+ * @fields: Array of packed_field_u16 field definitions. They must not overlap.
+ * @num_fields: Length of @fields array.
+ * @quirks: A bit mask of QUIRK_LITTLE_ENDIAN, QUIRK_LSW32_IS_FIRST and
+ *	    QUIRK_MSB_ON_THE_RIGHT.
+ *
+ * Use the pack_fields() macro instead of calling this directly.
+ */
+void pack_fields_u16(void *pbuf, size_t pbuflen, const void *ustruct,
+		     const struct packed_field_u16 *fields, size_t num_fields,
+		     u8 quirks)
+{
+	__pack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks);
+}
+EXPORT_SYMBOL(pack_fields_u16);
+
+/**
+ * unpack_fields_u8 - Unpack array of fields
+ *
+ * @pbuf: Pointer to a buffer holding the packed value.
+ * @pbuflen: The length in bytes of the packed buffer pointed to by @pbuf.
+ * @ustruct: Pointer to CPU-readable structure holding the unpacked value.
+ *	     It is expected (but not checked) that this has the same data type
+ *	     as all struct packed_field_u8 definitions.
+ * @fields: Array of packed_field_u8 field definitions. They must not overlap.
+ * @num_fields: Length of @fields array.
+ * @quirks: A bit mask of QUIRK_LITTLE_ENDIAN, QUIRK_LSW32_IS_FIRST and
+ *	    QUIRK_MSB_ON_THE_RIGHT.
+ *
+ * Use the unpack_fields() macro instead of calling this directly.
+ */
+void unpack_fields_u8(const void *pbuf, size_t pbuflen, void *ustruct,
+		      const struct packed_field_u8 *fields, size_t num_fields,
+		      u8 quirks)
+{
+	__unpack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks);
+}
+EXPORT_SYMBOL(unpack_fields_u8);
+
+/**
+ * unpack_fields_u16 - Unpack array of fields
+ *
+ * @pbuf: Pointer to a buffer holding the packed value.
+ * @pbuflen: The length in bytes of the packed buffer pointed to by @pbuf.
+ * @ustruct: Pointer to CPU-readable structure holding the unpacked value.
+ *	     It is expected (but not checked) that this has the same data type
+ *	     as all struct packed_field_u16 definitions.
+ * @fields: Array of packed_field_u16 field definitions. They must not overlap.
+ * @num_fields: Length of @fields array.
+ * @quirks: A bit mask of QUIRK_LITTLE_ENDIAN, QUIRK_LSW32_IS_FIRST and
+ *	    QUIRK_MSB_ON_THE_RIGHT.
+ *
+ * Use the unpack_fields() macro instead of calling this directly.
+ */
+void unpack_fields_u16(const void *pbuf, size_t pbuflen, void *ustruct,
+		       const struct packed_field_u16 *fields, size_t num_fields,
+		       u8 quirks)
+{
+	__unpack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks);
+}
+EXPORT_SYMBOL(unpack_fields_u16);
+
+MODULE_DESCRIPTION("Generic bitfield packing and unpacking");