[PATCH net-next v5 0/9] lib: packing: introduce and use (un)pack_fields

[PATCH net-next v5 0/9] lib: packing: introduce and use (un)pack_fields

[Jacob Keller]

This series improves the packing library with a new API for packing or
unpacking a large number of fields at once with minimal code footprint. The
API is then used to replace bespoke packing logic in the ice driver,
preparing it to handle unpacking in the future. Finally, the ice driver has
a few other cleanups related to the packing logic.

The pack_fields and unpack_fields functions have the following improvements
over the existing pack() and unpack() API:

 1. Packing or unpacking a large number of fields takes significantly less
    code. This significantly reduces the .text size for an increase in the
    .data size which is much smaller.

 2. The unpacked data can be stored in sizes smaller than u64 variables.
    This reduces the storage requirement both for runtime data structures,
    and for the rodata defining the fields. This scales with the number of
    fields used.

 3. Most of the error checking is done at compile time, rather than
    runtime, via additional checks added to modpost. This saves wasted
    computation time *and* catches errors in the field definitions early,
    rather than only after the offending code is executed.

The actual packing and unpacking code still uses the u64 size
variables. However, these are converted to the appropriate field sizes when
storing or reading the data from the buffer.

The majority of the "compile time" checks are placed into modpost. This is
done to enable checking ordering and overlap of the fields. An attempt was
made to implement these checks via macro in version 2 of this series.
However, the C pre-processor cannot use loops to execute compile time
checks. Without the loops, drivers were responsible for using the specific
CHECK_PACKED_FIELDS_<N> macro. We generated these macros at compile time,
but this resulted in thousands of lines of macro in the
<generated/packing-checks.h> header. To limit the size, we tried config
options to only generate the macros that are used. This resulted in even
more complexity in the drivers and the build system.

By using modpost, all of this complexity is kept in one place, minimizing
the complexity on driver authors.

Modpost can easily check the field overlap and ordering restrictions, but
it cannot easily check that the fields fit within the buffers. To do that,
modpost would need to obtain the size of the target buffer. This was
attempted in v3, but the result was a mess, as modpost had to obtain a
special symbol with the target size.

Instead, modpost now only checks the things that are simple for it to
check. The buffer size check is now handled directly by the pack_fields and
unpack_fields macros. To obtain the size, we enforce that users wrap their
buffer with an appropriate type (such as via a packed structure with a
fixed size buffer). This reduces the number of arguments, and enables easy
size checking. To allow both ascending and descending order, the first and
last elements are checked to be within the size of the buffer. Modpost
ensures that we do not allow other orderings, so we only need to check 2
places.

This version has much simpler modpost checks, as we no longer need to keep
a hash of all the symbols: each symbol is independently checked. This
reduces the amount of code even further, and avoids some other
modifications that were originally required.

This implementation is even simpler than before, and I do think modpost is
better overall. The macro checks require additional work from drivers and
might need to be extended if a user ever needs more than 50 fields.

If the enforcement of a structured type is frowned upon, I believe we could
keep the original API with a pbuflen argument and use
__builtin_choose_expr() and __is_constexpr() to determine whether to have
the checks run at compile time or run time.

I'm in favor of this modpost implementation over the previous macro based
solution. The fact that the mess of checking the fields is fairly self
contained and avoids the mess of the CHECK_* and config options is a big
win, and I think the modpost option is significantly better for this.

Pros:

 * Significantly less code to implement the checks, even if we ignore the
   generated portions in <generated/packing-checks.h>

 * The modpost checks are able to work in arbitrarily sized arrays, without
   needing to add any modification in the future. The macro implementation
   could require adding additional macros if a driver ever needed >50
   fields.

 * Keeping the size checks within pack_fields() and unpack_fields() greatly
   simplifies the modpost implementation as we no longer need to determine
   the sizes. This makes the checks extremely self contained.

 * This solution avoids needing to edit the top level Kbuild.

 * We don't need to leave 20K+ lines of code in a generated header.

 * We don't need to add extra config options.

 * Field order is enforced, which I think is useful even outside
   simplifying the overlap checks to O(N).

 * Drivers simply DECLARE_PACKED_FIELDS_(S|M) and get modpost warnings,
   without requiring a manual call to CHECK_PACKED_FIELDS*. This should
   make it easier to review, and less likely that checks are skipped.

Cons:

 * modpost doesn't have source code line information, so we can't report
   that back to the user.

 * modpost errors are reported slightly later in the compile process.

 * We have to place the packed field arrays in special sections to enable
   modpost. This is handled by DECLARE macros, so we have to ensure all
   users use these macros. I did not attempt to add a check for that in
   this series, but it could be done in principle with cocinelle or
   checkpatch.

 * These type of checks do feel somewhat ancillary to the original purpose
   of modpost.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
Changes in v5:
- Fix printf format specifier for the sym->st_size
- Link to v4: https://lore.kernel.org/r/20241108-packing-pack-fields-and-ice-implementation-v4-0-81a9f42c30e5@intel.com

Changes in v4:
- Move the buffer size checks to (un)pack_fields() macros.
- Enforce use of a sized type of the packed buffer, removing the now
  unnecessary pbuflen argument of (un)pack_fields().
- Drop exporting the buffer size to modpost.
- Simplify modpost implementation to directly check each symbol in the
  handle_packed_field_symbol() function. This removes the need for a hash,
  and is ultimately much simpler now that modpost doesn't need the size of
  the target buffer.
- Fix the width check to correctly calculate the width and compare it
  properly.
- Refactor modpost messages to consistently report the module name first,
  the symbol name second, and the field number 3rd.
- Correctly implement overlap checks in the modpost, rather than only
  checking field ordering.
- Link to v3: https://lore.kernel.org/r/20241107-packing-pack-fields-and-ice-implementation-v3-0-27c566ac2436@intel.com

Changes in v3:
- Replace macro-based C pre-processor checks with checks implemented in
  modpost.
- Move structure definitions into  <linux/packing_types.h> to enable reuse
  within modpost.
- Add DECLARE_PACKED_FIELDS_S and DECLARE_PACKED_FIELDS_M to enable
  automatically generating the buffer size constants and the section
  attributes.
- Add additional unit tests for the pack_fields and unpack_fields APIs.
- Update documentation with an explanation of the new API as well as some
  example code.
- Link to v2: https://lore.kernel.org/r/20241025-packing-pack-fields-and-ice-implementation-v2-0-734776c88e40@intel.com

Changes in v2:
- Add my missing sign-off to the first patch
- Update the descriptions for a few patches
- Only generate CHECK_PACKED_FIELDS_N when another module selects it
- Add a new patch introducing wrapper structures for the packed Tx and Rx
  queue context, suggested by Vladimir.
- Drop the now unnecessary macros in ice, thanks to the new types
- Link to v1: https://lore.kernel.org/r/20241011-packing-pack-fields-and-ice-implementation-v1-0-d9b1f7500740@intel.com

---
Jacob Keller (6):
      ice: remove int_q_state from ice_tlan_ctx
      ice: use structures to keep track of queue context size
      ice: use <linux/packing.h> for Tx and Rx queue context data
      ice: reduce size of queue context fields
      ice: move prefetch enable to ice_setup_rx_ctx
      ice: cleanup Rx queue context programming functions

Vladimir Oltean (3):
      lib: packing: create __pack() and __unpack() variants without error checking
      lib: packing: demote truncation error in pack() to a warning in __pack()
      lib: packing: add pack_fields() and unpack_fields()

 drivers/net/ethernet/intel/ice/ice_adminq_cmd.h |  11 +-
 drivers/net/ethernet/intel/ice/ice_common.h     |   5 +-
 drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h  |  49 +---
 include/linux/packing.h                         |  43 ++++
 include/linux/packing_types.h                   |  48 ++++
 scripts/mod/modpost.h                           |   5 +
 drivers/net/dsa/sja1105/sja1105_static_config.c |   8 +-
 drivers/net/ethernet/intel/ice/ice_base.c       |   6 +-
 drivers/net/ethernet/intel/ice/ice_common.c     | 293 +++++-------------------
 lib/packing.c                                   | 285 +++++++++++++++++------
 lib/packing_test.c                              |  61 +++++
 scripts/mod/modpost.c                           |   3 +-
 scripts/mod/packed_fields.c                     | 199 ++++++++++++++++
 Documentation/core-api/packing.rst              |  59 +++++
 MAINTAINERS                                     |   2 +
 drivers/net/ethernet/intel/Kconfig              |   1 +
 scripts/mod/Makefile                            |   4 +-
 17 files changed, 725 insertions(+), 357 deletions(-)
---
base-commit: 774ca6d3bf24287ff60b7d6dd4171ebb6e47760a
change-id: 20241004-packing-pack-fields-and-ice-implementation-b17c7ce8e373

Best regards,
-- 
Jacob Keller <jacob.e.keller@intel.com>

[PATCH net-next v5 1/9] lib: packing: create __pack() and __unpack() variants without error checking

[Jacob Keller]

From: Vladimir Oltean <vladimir.oltean@nxp.com>

A future variant of the API, which works on arrays of packed_field
structures, will make most of these checks redundant. The idea will be
that we want to perform sanity checks at compile time, not once
for every function call.

Introduce new variants of pack() and unpack(), which elide the sanity
checks, assuming that the input was pre-sanitized.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
 lib/packing.c | 142 ++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 78 insertions(+), 64 deletions(-)

diff --git a/lib/packing.c b/lib/packing.c
index 793942745e34..f237b8af99f5 100644
--- a/lib/packing.c
+++ b/lib/packing.c
@@ -51,64 +51,20 @@ static size_t calculate_box_addr(size_t box, size_t len, u8 quirks)
 	return offset_of_group + offset_in_group;
 }
 
-/**
- * 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)
+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, plogical_last_u8, box;
-	/* 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 (unlikely(startbit < endbit || startbit >= BITS_PER_BYTE * pbuflen))
-		/* Invalid function call */
-		return -EINVAL;
-
-	value_width = startbit - endbit + 1;
-	if (unlikely(value_width > 64))
-		return -ERANGE;
-
-	/* Check if "uval" fits in "value_width" bits.
-	 * If value_width is 64, the check will fail, but any
-	 * 64-bit uval will surely fit.
-	 */
-	if (unlikely(value_width < 64 && uval >= (1ull << value_width)))
-		/* Cannot store "uval" inside "value_width" bits.
-		 * Truncating "uval" is most certainly not desirable,
-		 * so simply erroring out is appropriate.
-		 */
-		return -ERANGE;
+	int plogical_first_u8 = startbit / BITS_PER_BYTE;
+	int plogical_last_u8 = endbit / BITS_PER_BYTE;
+	int box;
 
 	/* 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.
 	 */
-	plogical_first_u8 = startbit / BITS_PER_BYTE;
-	plogical_last_u8  = endbit / BITS_PER_BYTE;
-
 	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;
@@ -163,15 +119,13 @@ int pack(void *pbuf, u64 uval, size_t startbit, size_t endbit, size_t pbuflen,
 		((u8 *)pbuf)[box_addr] &= ~box_mask;
 		((u8 *)pbuf)[box_addr] |= pval;
 	}
-	return 0;
 }
-EXPORT_SYMBOL(pack);
 
 /**
- * unpack - Unpack u64 number from packed buffer.
+ * pack - Pack u64 number into bitfield of buffer.
  *
  * @pbuf: Pointer to a buffer holding the packed value.
- * @uval: Pointer to an u64 holding the unpacked 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.
@@ -183,16 +137,12 @@ EXPORT_SYMBOL(pack);
  *	    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.
+ *	   correct usage, return code may be discarded. The @pbuf memory will
+ *	   be modified on success.
  */
-int unpack(const void *pbuf, u64 *uval, size_t startbit, size_t endbit,
-	   size_t pbuflen, u8 quirks)
+int 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, plogical_last_u8, box;
 	/* width of the field to access in the pbuf */
 	u64 value_width;
 
@@ -207,6 +157,33 @@ int unpack(const void *pbuf, u64 *uval, size_t startbit, size_t endbit,
 	if (unlikely(value_width > 64))
 		return -ERANGE;
 
+	/* Check if "uval" fits in "value_width" bits.
+	 * If value_width is 64, the check will fail, but any
+	 * 64-bit uval will surely fit.
+	 */
+	if (value_width < 64 && uval >= (1ull << value_width))
+		/* Cannot store "uval" inside "value_width" bits.
+		 * Truncating "uval" is most certainly not desirable,
+		 * so simply erroring out is appropriate.
+		 */
+		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;
 
@@ -214,9 +191,6 @@ int unpack(const void *pbuf, u64 *uval, size_t startbit, size_t endbit,
 	 * no quirks, u8 by u8 (aligned at u8 boundaries), from high to low
 	 * logical bit significance. "box" denotes the current logical u8.
 	 */
-	plogical_first_u8 = startbit / BITS_PER_BYTE;
-	plogical_last_u8  = endbit / BITS_PER_BYTE;
-
 	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;
@@ -271,6 +245,46 @@ int unpack(const void *pbuf, u64 *uval, size_t startbit, size_t endbit,
 		*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);

-- 
2.47.0.265.g4ca455297942

[PATCH net-next v5 2/9] lib: packing: demote truncation error in pack() to a warning in __pack()

[Jacob Keller]

From: Vladimir Oltean <vladimir.oltean@nxp.com>

Most of the sanity checks in pack() and unpack() can be covered at
compile time. There is only one exception, and that is truncation of the
uval during a pack() operation.

We'd like the error-less __pack() to catch that condition as well. But
at the same time, it is currently the responsibility of consumer drivers
(currently just sja1105) to print anything at all when this error
occurs, and then discard the return code.

We can just print a loud warning in the library code and continue with
the truncated __pack() operation. In practice, having the warning is
very important, see commit 24deec6b9e4a ("net: dsa: sja1105: disallow
C45 transactions on the BASE-TX MDIO bus") where the bug was caught
exactly by noticing this print.

Add the first print to the packing library, and at the same time remove
the print for the same condition from the sja1105 driver, to avoid
double printing.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 drivers/net/dsa/sja1105/sja1105_static_config.c |  8 ++------
 lib/packing.c                                   | 26 ++++++++++---------------
 2 files changed, 12 insertions(+), 22 deletions(-)

diff --git a/drivers/net/dsa/sja1105/sja1105_static_config.c b/drivers/net/dsa/sja1105/sja1105_static_config.c
index baba204ad62f..3d790f8c6f4d 100644
--- a/drivers/net/dsa/sja1105/sja1105_static_config.c
+++ b/drivers/net/dsa/sja1105/sja1105_static_config.c
@@ -26,12 +26,8 @@ void sja1105_pack(void *buf, const u64 *val, int start, int end, size_t len)
 		pr_err("Start bit (%d) expected to be larger than end (%d)\n",
 		       start, end);
 	} else if (rc == -ERANGE) {
-		if ((start - end + 1) > 64)
-			pr_err("Field %d-%d too large for 64 bits!\n",
-			       start, end);
-		else
-			pr_err("Cannot store %llx inside bits %d-%d (would truncate)\n",
-			       *val, start, end);
+		pr_err("Field %d-%d too large for 64 bits!\n",
+		       start, end);
 	}
 	dump_stack();
 }
diff --git a/lib/packing.c b/lib/packing.c
index f237b8af99f5..09a2d195b943 100644
--- a/lib/packing.c
+++ b/lib/packing.c
@@ -59,8 +59,17 @@ static void __pack(void *pbuf, u64 uval, size_t startbit, size_t endbit,
 	 */
 	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.
@@ -143,9 +152,6 @@ static void __pack(void *pbuf, u64 uval, size_t startbit, size_t endbit,
 int pack(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.
 	 */
@@ -153,19 +159,7 @@ int pack(void *pbuf, u64 uval, size_t startbit, size_t endbit, size_t pbuflen,
 		/* Invalid function call */
 		return -EINVAL;
 
-	value_width = startbit - endbit + 1;
-	if (unlikely(value_width > 64))
-		return -ERANGE;
-
-	/* Check if "uval" fits in "value_width" bits.
-	 * If value_width is 64, the check will fail, but any
-	 * 64-bit uval will surely fit.
-	 */
-	if (value_width < 64 && uval >= (1ull << value_width))
-		/* Cannot store "uval" inside "value_width" bits.
-		 * Truncating "uval" is most certainly not desirable,
-		 * so simply erroring out is appropriate.
-		 */
+	if (unlikely(startbit - endbit >= 64))
 		return -ERANGE;
 
 	__pack(pbuf, uval, startbit, endbit, pbuflen, quirks);

-- 
2.47.0.265.g4ca455297942

[PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()

[Jacob Keller]

From: Vladimir Oltean <vladimir.oltean@nxp.com>

This is new API which caters to the following requirements:

- Pack or unpack a large number of fields to/from a buffer with a small
  code footprint. The current alternative is to open-code a large number
  of calls to pack() and unpack(), or to use packing() to reduce that
  number to half. But packing() is not const-correct.

- Use unpacked numbers stored in variables smaller than u64. This
  reduces the rodata footprint of the stored field arrays.

- Perform error checking at compile time, rather than runtime, and return
  void from the API functions. Because the C preprocessor can't generat
  variable length code (loops), we can't easily use macros to implement the
  overlap checks at compile time.

  Instead, check for field ordering and overlap in modpost. This allows
  writing C code to validate the data. Enable this by marking the packed
  field arrays in a special data section via use of __section() as part of
  DECLARE_PACKED_FIELD_S and DECLARE_PACKED_FIELD_M macros.

  While modpost can easily check ordering of the packed fields and ensure
  no fields overlap, it is tricky to check that the fields all fit within
  the intended buffer. This is instead handled by BUILD_BUG_ON in the
  pack_fields and unpack_fields() macros. To enable this, the macros
  require that the buffers be represented by a type which has a size. Users
  of the API will need to ensure their buffers are represented by pointers
  to a type of the appropriate size, such as with a struct typedef.

  The use of modpost keeps the logic for size checking contained to one
  place, without requiring drivers to invoke a separate macro like the
  previous C pre-processor solution. It also avoids the need for thousands
  of generated lines of macro.

- Reduced rodata footprint for the storage of the packed field arrays.
  To that end, we have struct packed_field_s (small) and packed_field_m
  (medium). More can be added as needed (unlikely for now). On these
  types, the same generic pack_fields() and unpack_fields() API can be
  used, thanks to the new C11 _Generic() selection feature, which can
  call pack_fields_s() or pack_fields_m(), depending on the type of the
  "fields" array - a simplistic form of polymorphism. It is evaluated at
  compile time which function will actually be called.

Over time, packing() is expected to be completely replaced either with
pack() or with pack_fields().

Co-developed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 include/linux/packing.h            |  43 ++++++++
 include/linux/packing_types.h      |  48 +++++++++
 scripts/mod/modpost.h              |   5 +
 lib/packing.c                      | 145 +++++++++++++++++++++++++++
 lib/packing_test.c                 |  61 ++++++++++++
 scripts/mod/modpost.c              |   3 +-
 scripts/mod/packed_fields.c        | 199 +++++++++++++++++++++++++++++++++++++
 Documentation/core-api/packing.rst |  59 +++++++++++
 MAINTAINERS                        |   2 +
 scripts/mod/Makefile               |   4 +-
 10 files changed, 566 insertions(+), 3 deletions(-)

diff --git a/include/linux/packing.h b/include/linux/packing.h
index 5d36dcd06f60..18e59102ef47 100644
--- a/include/linux/packing.h
+++ b/include/linux/packing.h
@@ -7,6 +7,7 @@
 
 #include <linux/types.h>
 #include <linux/bitops.h>
+#include <linux/packing_types.h>
 
 #define QUIRK_MSB_ON_THE_RIGHT	BIT(0)
 #define QUIRK_LITTLE_ENDIAN	BIT(1)
@@ -26,4 +27,46 @@ int pack(void *pbuf, u64 uval, size_t startbit, size_t endbit, size_t pbuflen,
 int unpack(const void *pbuf, u64 *uval, size_t startbit, size_t endbit,
 	   size_t pbuflen, u8 quirks);
 
+void pack_fields_s(void *pbuf, size_t pbuflen, const void *ustruct,
+		   const struct packed_field_s *fields, size_t num_fields,
+		   u8 quirks);
+
+void pack_fields_m(void *pbuf, size_t pbuflen, const void *ustruct,
+		   const struct packed_field_m *fields, size_t num_fields,
+		   u8 quirks);
+
+void unpack_fields_s(const void *pbuf, size_t pbuflen, void *ustruct,
+		     const struct packed_field_s *fields, size_t num_fields,
+		     u8 quirks);
+
+void unpack_fields_m(const void *pbuf, size_t pbuflen, void *ustruct,
+		     const struct packed_field_m *fields, size_t num_fields,
+		     u8 quirks);
+
+#define pack_fields(pbuf, ustruct, fields, quirks) \
+	({ \
+		typeof(fields[0]) *__f = fields; \
+		size_t pbuflen = sizeof(*pbuf); \
+		size_t num_fields = ARRAY_SIZE(fields); \
+		BUILD_BUG_ON(__f[0].startbit >= BITS_PER_BYTE * pbuflen); \
+		BUILD_BUG_ON(__f[num_fields - 1].startbit >= BITS_PER_BYTE * pbuflen); \
+		_Generic((fields), \
+			 const struct packed_field_s * : pack_fields_s, \
+			 const struct packed_field_m * : pack_fields_m \
+			)(pbuf, pbuflen, ustruct, __f, num_fields, quirks); \
+	})
+
+#define unpack_fields(pbuf, ustruct, fields, quirks) \
+	({ \
+		typeof(fields[0]) *__f = fields; \
+		size_t pbuflen = sizeof(*pbuf); \
+		size_t num_fields = ARRAY_SIZE(fields); \
+		BUILD_BUG_ON(__f[0].startbit >= BITS_PER_BYTE * pbuflen); \
+		BUILD_BUG_ON(__f[num_fields - 1].startbit >= BITS_PER_BYTE * pbuflen); \
+		_Generic((fields), \
+			 const struct packed_field_s * : unpack_fields_s, \
+			 const struct packed_field_m * : unpack_fields_m \
+			)(pbuf, pbuflen, ustruct, __f, num_fields, quirks); \
+	})
+
 #endif
diff --git a/include/linux/packing_types.h b/include/linux/packing_types.h
new file mode 100644
index 000000000000..e0fa5d38ca48
--- /dev/null
+++ b/include/linux/packing_types.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) 2024, Intel Corporation
+ * Copyright (c) 2024, Vladimir Oltean <olteanv@gmail.com>
+ */
+#ifndef _LINUX_PACKING_TYPES_H
+#define _LINUX_PACKING_TYPES_H
+
+#include <linux/types.h>
+
+/* If you add another packed field type, please update
+ * scripts/mod/packed_fields.c to enable compile time sanity checks.
+ */
+
+#define GEN_PACKED_FIELD_MEMBERS(__type) \
+	__type startbit; \
+	__type endbit; \
+	__type offset; \
+	__type size;
+
+/* Small packed field. Use with bit offsets < 256, buffers < 32B and
+ * unpacked structures < 256B.
+ */
+struct packed_field_s {
+	GEN_PACKED_FIELD_MEMBERS(u8);
+};
+
+#define DECLARE_PACKED_FIELDS_S(name) \
+	const struct packed_field_s name[] __section(".rodata.packed_fields_s")
+
+/* Medium packed field. Use with bit offsets < 65536, buffers < 8KB and
+ * unpacked structures < 64KB.
+ */
+struct packed_field_m {
+	GEN_PACKED_FIELD_MEMBERS(u16);
+};
+
+#define DECLARE_PACKED_FIELDS_M(name) \
+	const struct packed_field_m name[] __section(".rodata.packed_fields_m")
+
+#define PACKED_FIELD(start, end, struct_name, struct_field) \
+{ \
+	(start), \
+	(end), \
+	offsetof(struct_name, struct_field), \
+	sizeof_field(struct_name, struct_field), \
+}
+
+#endif
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index ada3a36cc4bc..01e678626531 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -175,12 +175,17 @@ void add_moddevtable(struct buffer *buf, struct module *mod);
 /* sumversion.c */
 void get_src_version(const char *modname, char sum[], unsigned sumlen);
 
+/* packed_fields.c */
+void handle_packed_field_symbol(struct module *mod, struct elf_info *info,
+				Elf_Sym *sym, const char *symname);
+
 /* from modpost.c */
 extern bool target_is_big_endian;
 extern bool host_is_big_endian;
 char *read_text_file(const char *filename);
 char *get_line(char **stringp);
 void *sym_get_data(const struct elf_info *info, const Elf_Sym *sym);
+const char *sec_name(const struct elf_info *info, unsigned int secindex);
 
 void __attribute__((format(printf, 2, 3)))
 modpost_log(bool is_error, const char *fmt, ...);
diff --git a/lib/packing.c b/lib/packing.c
index 09a2d195b943..45164f73fe5b 100644
--- a/lib/packing.c
+++ b/lib/packing.c
@@ -5,10 +5,37 @@
 #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
@@ -322,4 +349,122 @@ int packing(void *pbuf, u64 *uval, int startbit, int endbit, size_t pbuflen,
 }
 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_s - Pack array of small 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_s definitions.
+ * @fields: Array of small packed fields 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.
+ */
+void pack_fields_s(void *pbuf, size_t pbuflen, const void *ustruct,
+		   const struct packed_field_s *fields, size_t num_fields,
+		   u8 quirks)
+{
+	__pack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks);
+}
+EXPORT_SYMBOL(pack_fields_s);
+
+/**
+ * pack_fields_m - Pack array of medium 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_s definitions.
+ * @fields: Array of medium packed fields 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.
+ */
+void pack_fields_m(void *pbuf, size_t pbuflen, const void *ustruct,
+		   const struct packed_field_m *fields, size_t num_fields,
+		   u8 quirks)
+{
+	__pack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks);
+}
+EXPORT_SYMBOL(pack_fields_m);
+
+/**
+ * unpack_fields_s - Unpack array of small 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_s definitions.
+ * @fields: Array of small packed fields 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.
+ */
+void unpack_fields_s(const void *pbuf, size_t pbuflen, void *ustruct,
+		     const struct packed_field_s *fields, size_t num_fields,
+		     u8 quirks)
+{
+	__unpack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks);
+}
+EXPORT_SYMBOL(unpack_fields_s);
+
+/**
+ * unpack_fields_m - Unpack array of medium 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_s definitions.
+ * @fields: Array of medium packed fields 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.
+ */
+void unpack_fields_m(const void *pbuf, size_t pbuflen, void *ustruct,
+		     const struct packed_field_m *fields, size_t num_fields,
+		     u8 quirks)
+{
+	__unpack_fields(pbuf, pbuflen, ustruct, fields, num_fields, quirks);
+}
+EXPORT_SYMBOL(unpack_fields_m);
+
 MODULE_DESCRIPTION("Generic bitfield packing and unpacking");
diff --git a/lib/packing_test.c b/lib/packing_test.c
index b38ea43c03fd..d8693e797d9b 100644
--- a/lib/packing_test.c
+++ b/lib/packing_test.c
@@ -396,9 +396,70 @@ static void packing_test_unpack(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, uval, params->uval);
 }
 
+#define PACKED_BUF_SIZE 8
+
+typedef struct __packed { u8 buf[PACKED_BUF_SIZE]; } packed_buf_t;
+
+struct test_data {
+	u32 field3;
+	u16 field2;
+	u16 field4;
+	u16 field6;
+	u8 field1;
+	u8 field5;
+};
+
+static DECLARE_PACKED_FIELDS_S(test_fields) = {
+	PACKED_FIELD(63, 61, struct test_data, field1),
+	PACKED_FIELD(60, 52, struct test_data, field2),
+	PACKED_FIELD(51, 28, struct test_data, field3),
+	PACKED_FIELD(27, 14, struct test_data, field4),
+	PACKED_FIELD(13, 9, struct test_data, field5),
+	PACKED_FIELD(8, 0, struct test_data, field6),
+};
+
+static void packing_test_pack_fields(struct kunit *test)
+{
+	const struct test_data data = {
+		.field1 = 0x2,
+		.field2 = 0x100,
+		.field3 = 0xF00050,
+		.field4 = 0x7D3,
+		.field5 = 0x9,
+		.field6 = 0x10B,
+	};
+	packed_buf_t expect = {
+		.buf = { 0x50, 0x0F, 0x00, 0x05, 0x01, 0xF4, 0xD3, 0x0B },
+	};
+	packed_buf_t buf = {};
+
+	pack_fields(&buf, &data, test_fields, 0);
+
+	KUNIT_EXPECT_MEMEQ(test, &expect, &buf, sizeof(buf));
+}
+
+static void packing_test_unpack_fields(struct kunit *test)
+{
+	const packed_buf_t buf = {
+		.buf = { 0x17, 0x28, 0x10, 0x19, 0x3D, 0xA9, 0x07, 0x9C },
+	};
+	struct test_data data = {};
+
+	unpack_fields(&buf, &data, test_fields, 0);
+
+	KUNIT_EXPECT_EQ(test, 0, data.field1);
+	KUNIT_EXPECT_EQ(test, 0x172, data.field2);
+	KUNIT_EXPECT_EQ(test, 0x810193, data.field3);
+	KUNIT_EXPECT_EQ(test, 0x36A4, data.field4);
+	KUNIT_EXPECT_EQ(test, 0x3, data.field5);
+	KUNIT_EXPECT_EQ(test, 0x19C, data.field6);
+}
+
 static struct kunit_case packing_test_cases[] = {
 	KUNIT_CASE_PARAM(packing_test_pack, packing_gen_params),
 	KUNIT_CASE_PARAM(packing_test_unpack, packing_gen_params),
+	KUNIT_CASE(packing_test_pack_fields),
+	KUNIT_CASE(packing_test_unpack_fields),
 	{},
 };
 
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 107393a8c48a..5425a2afc2d8 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -327,7 +327,7 @@ static const char *sech_name(const struct elf_info *info, Elf_Shdr *sechdr)
 				      sechdr->sh_name);
 }
 
-static const char *sec_name(const struct elf_info *info, unsigned int secindex)
+const char *sec_name(const struct elf_info *info, unsigned int secindex)
 {
 	/*
 	 * If sym->st_shndx is a special section index, there is no
@@ -1602,6 +1602,7 @@ static void read_symbols(const char *modname)
 
 		handle_symbol(mod, &info, sym, symname);
 		handle_moddevtable(mod, &info, sym, symname);
+		handle_packed_field_symbol(mod, &info, sym, symname);
 	}
 
 	check_sec_ref(mod, &info);
diff --git a/scripts/mod/packed_fields.c b/scripts/mod/packed_fields.c
new file mode 100644
index 000000000000..474c8a8122e2
--- /dev/null
+++ b/scripts/mod/packed_fields.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024, Intel Corporation. */
+
+/* Code to validate struct packed_field_[sm] data, and perform sanity checks
+ * to ensure the packed field data is laid out correctly and fits into the
+ * relevant buffer size.
+ */
+
+#include <fnmatch.h>
+#include <hashtable.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <xalloc.h>
+
+#include "modpost.h"
+
+typedef uint16_t	u16;
+typedef uint8_t		u8;
+
+#define BITS_PER_BYTE	8
+
+/* Big exception to the "don't include kernel headers into userspace", which
+ * even potentially has different endianness and word sizes, since we handle
+ * those differences explicitly below
+ */
+#include "../../include/linux/packing_types.h"
+
+#define max(a, b) ({\
+		typeof(a) _a = a;\
+		typeof(b) _b = b;\
+		_a > _b ? _a : _b; })
+
+#define min(a, b) ({\
+		typeof(a) _a = a;\
+		typeof(b) _b = b;\
+		_a < _b ? _a : _b; })
+
+struct packed_field_elem {
+	uint64_t startbit;
+	uint64_t endbit;
+	uint64_t offset;
+	uint64_t size;
+};
+
+enum field_type {
+	UNKNOWN_SECTION,
+	PACKED_FIELD_S,
+	PACKED_FIELD_M,
+};
+
+enum element_order {
+	FIRST_ELEMENT,
+	SECOND_ELEMENT,
+	ASCENDING_ORDER,
+	DESCENDING_ORDER,
+};
+
+static size_t field_type_to_size(enum field_type type)
+{
+	switch (type) {
+	case PACKED_FIELD_S:
+		return sizeof(struct packed_field_s);
+	case PACKED_FIELD_M:
+		return sizeof(struct packed_field_m);
+	default:
+		error("attempted to get field size for unknown packed field type %u\n",
+		      type);
+		return 0;
+	}
+}
+
+static void get_field_contents(const void *data, enum field_type type,
+			       struct packed_field_elem *elem)
+{
+	switch (type) {
+	case PACKED_FIELD_S: {
+		const struct packed_field_s *data_field = data;
+
+		elem->startbit = TO_NATIVE(data_field->startbit);
+		elem->endbit = TO_NATIVE(data_field->endbit);
+		elem->offset = TO_NATIVE(data_field->offset);
+		elem->size = TO_NATIVE(data_field->size);
+		return;
+	}
+	case PACKED_FIELD_M: {
+		const struct packed_field_m *data_field = data;
+
+		elem->startbit = TO_NATIVE(data_field->startbit);
+		elem->endbit = TO_NATIVE(data_field->endbit);
+		elem->offset = TO_NATIVE(data_field->offset);
+		elem->size = TO_NATIVE(data_field->size);
+		return;
+	}
+	default:
+		error("attempted to get field contents for unknown packed field type %u\n",
+		      type);
+	}
+}
+
+void handle_packed_field_symbol(struct module *mod, struct elf_info *info,
+				Elf_Sym *sym, const char *symname)
+{
+	unsigned int secindex = get_secindex(info, sym);
+	struct packed_field_elem elem = {}, prev = {};
+	enum element_order order = FIRST_ELEMENT;
+	enum field_type type = UNKNOWN_SECTION;
+	size_t field_size, count;
+	const void *data, *ptr;
+	const char *section;
+
+	/* Skip symbols without a name */
+	if (*symname == '\0')
+		return;
+
+	/* Skip symbols with invalid sections */
+	if (secindex >= info->num_sections)
+		return;
+
+	section = sec_name(info, secindex);
+
+	if (strcmp(section, ".rodata.packed_fields_s") == 0)
+		type = PACKED_FIELD_S;
+	else if (strcmp(section, ".rodata.packed_fields_m") == 0)
+		type = PACKED_FIELD_M;
+
+	/* Other sections don't relate to packed fields */
+	if (type == UNKNOWN_SECTION)
+		return;
+
+	field_size = field_type_to_size(type);
+
+	/* check that the data is a multiple of the size */
+	if (sym->st_size % field_size != 0) {
+		error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",
+		      mod->name, symname, sym->st_size, field_size);
+		return;
+	}
+
+	data = sym_get_data(info, sym);
+
+	for (ptr = data, count = 0;
+	     ptr < data + sym->st_size;
+	     ptr += field_size, count++, prev = elem) {
+		get_field_contents(ptr, type, &elem);
+
+		if (elem.size != 1 && elem.size != 2 &&
+		    elem.size != 4 && elem.size != 8)
+			error("[%s.ko] \"%s\" field %zu unpacked size (%" PRIu64 ") must be 1, 2, 4, or 8\n",
+			      mod->name, symname, count, elem.size);
+
+		if (elem.startbit < elem.endbit)
+			error("[%s.ko] \"%s\" field %zu (%" PRIu64 "-%" PRIu64 "): start bit must be >= end bit\n",
+			      mod->name, symname, count,
+			      elem.startbit, elem.endbit);
+
+		if (elem.startbit - elem.endbit + 1 > BITS_PER_BYTE * elem.size)
+			error("[%s.ko] \"%s\" field %zu (%" PRIu64 "-%" PRIu64 ") has a width of %" PRIu64 " bits which does not fit into the unpacked structure field (%" PRIu64 " bytes)\n",
+			      mod->name, symname, count,
+			      elem.startbit, elem.endbit,
+			      elem.startbit - elem.endbit + 1,
+			      elem.size);
+
+		if (order != FIRST_ELEMENT &&
+		    max(elem.endbit, prev.endbit) <=
+		    min(elem.startbit, prev.startbit))
+			error("[%s.ko] \"%s\" field %zu (%" PRIu64 "-%" PRIu64 ") overlaps with previous field (%" PRIu64 "-%" PRIu64 ")\n",
+			      mod->name, symname, count,
+			      elem.startbit, elem.endbit,
+			      prev.startbit, prev.endbit);
+
+		switch (order) {
+		case FIRST_ELEMENT:
+			order = SECOND_ELEMENT;
+			break;
+		case SECOND_ELEMENT:
+			order = prev.startbit < elem.startbit ?
+				ASCENDING_ORDER : DESCENDING_ORDER;
+			break;
+		case ASCENDING_ORDER:
+			if (prev.startbit >= elem.startbit ||
+			    prev.endbit >= elem.endbit)
+				error("[%s.ko] \"%s\" field %zu (%" PRIu64 "-%" PRIu64") not in ascending order with previous field (%" PRIu64 "-%" PRIu64 ")\n",
+				      mod->name, symname, count,
+				      elem.startbit, elem.endbit,
+				      prev.startbit, prev.endbit);
+			break;
+		case DESCENDING_ORDER:
+			if (prev.startbit <= elem.startbit ||
+			    prev.endbit <= elem.endbit)
+				error("[%s.ko] \"%s\" field %zu (%" PRIu64 "-%" PRIu64") not in descending order with previous field (%" PRIu64 "-%" PRIu64 ")\n",
+				      mod->name, symname, count,
+				      elem.startbit, elem.endbit,
+				      prev.startbit, prev.endbit);
+			break;
+		default:
+			break;
+		}
+	}
+}
diff --git a/Documentation/core-api/packing.rst b/Documentation/core-api/packing.rst
index 821691f23c54..d4cdc287704d 100644
--- a/Documentation/core-api/packing.rst
+++ b/Documentation/core-api/packing.rst
@@ -235,3 +235,62 @@ programmer against incorrect API use.  The errors are not expected to occur
 during runtime, therefore it is reasonable for xxx_packing() to return void
 and simply swallow those errors. Optionally it can dump stack or print the
 error description.
+
+The pack_fields() and unpack_fields() macros automatically select the
+appropriate function at compile time based on the type of the fields array
+passed in.
+
+Packed Fields
+-------------
+
+Drivers are encouraged to use the ``pack_fields()`` and ``unpack_fields()``
+APIs over using ``pack()``, ``unpack()``, or ``packing()``.
+
+These APIs use field definitions in arrays of ``struct packed_field_s`` or
+``struct packed_field_m`` stored as ``.rodata``. This significantly reduces
+the code footprint required to pack or unpack many fields. In addition,
+sanity checks on the field definitions are handled at compile time via
+``modpost`` warnings, rather than only when the offending code is executed.
+
+The ``pack_fields()`` and ``unpack_fields()`` macros determine the size of
+the packed buffer by its type. Thus, you must ensure the buffer is a pointer
+to a type with the desired size. This is typically achieved by creating a
+typedef with a packed structure.
+
+Here is an example of how to use the fields APIs:
+
+.. code-block:: c
+
+   struct data {
+        u64 field3;
+        u32 field4;
+        u16 field1;
+        u8 field2;
+   };
+
+   #define SIZE 13
+
+   typdef struct __packed { u8 buf[SIZE]; } packed_buf_t;
+
+   DECLARE_PACKED_FIELDS_S(fields, SIZE) = {
+           PACKED_FIELD(100, 90, struct data, field1),
+           PACKED_FIELD(90, 87, struct data, field2),
+           PACKED_FIELD(86, 30, struct data, field3),
+           PACKED_FIELD(29, 0, struct data, field4),
+   };
+
+   void unpack_your_data(const packed_buf_t *buf, struct data *unpacked)
+   {
+           BUILD_BUG_ON(sizeof(*buf) != SIZE;
+
+           unpack_fields(buf, sizeof(*buf), unpacked, fields,
+                         QUIRK_LITTLE_ENDIAN);
+   }
+
+   void pack_your_data(const struct data *unpacked, packed_buf_t *buf)
+   {
+           BUILD_BUG_ON(sizeof(*buf) != SIZE;
+
+           pack_fields(buf, sizeof(*buf), unpacked, fields,
+                       QUIRK_LITTLE_ENDIAN);
+   }
diff --git a/MAINTAINERS b/MAINTAINERS
index a4855581d62c..daaf4ae5bd9c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17445,8 +17445,10 @@ L:	netdev@vger.kernel.org
 S:	Supported
 F:	Documentation/core-api/packing.rst
 F:	include/linux/packing.h
+F:	include/linux/packing_types.h
 F:	lib/packing.c
 F:	lib/packing_test.c
+F:	scripts/mod/packed_fields.c
 
 PADATA PARALLEL EXECUTION MECHANISM
 M:	Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
index c729bc936bae..aa729b6000b6 100644
--- a/scripts/mod/Makefile
+++ b/scripts/mod/Makefile
@@ -4,7 +4,7 @@ CFLAGS_REMOVE_empty.o += $(CC_FLAGS_LTO)
 hostprogs-always-y	+= modpost mk_elfconfig
 always-y		+= empty.o
 
-modpost-objs	:= modpost.o file2alias.o sumversion.o symsearch.o
+modpost-objs	:= modpost.o file2alias.o sumversion.o symsearch.o packed_fields.o
 
 devicetable-offsets-file := devicetable-offsets.h
 
@@ -15,7 +15,7 @@ targets += $(devicetable-offsets-file) devicetable-offsets.s
 
 # dependencies on generated files need to be listed explicitly
 
-$(obj)/modpost.o $(obj)/file2alias.o $(obj)/sumversion.o $(obj)/symsearch.o: $(obj)/elfconfig.h
+$(obj)/modpost.o $(obj)/file2alias.o $(obj)/sumversion.o $(obj)/symsearch.o $(obj)/packed_fields.o: $(obj)/elfconfig.h
 $(obj)/file2alias.o: $(obj)/$(devicetable-offsets-file)
 
 quiet_cmd_elfconfig = MKELF   $@

-- 
2.47.0.265.g4ca455297942

[PATCH net-next v5 4/9] ice: remove int_q_state from ice_tlan_ctx

[Jacob Keller]

The int_q_state field of the ice_tlan_ctx structure represents the internal
queue state. However, we never actually need to assign this or read this
during normal operation. In fact, trying to unpack it would not be possible
as it is larger than a u64. Remove this field from the ice_tlan_ctx
structure, and remove its packing field from the ice_tlan_ctx_info array.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h | 1 -
 drivers/net/ethernet/intel/ice/ice_common.c    | 1 -
 2 files changed, 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
index 611577ebc29d..0e8ed8c226e6 100644
--- a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
+++ b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
@@ -590,7 +590,6 @@ struct ice_tlan_ctx {
 	u8 drop_ena;
 	u8 cache_prof_idx;
 	u8 pkt_shaper_prof_idx;
-	u8 int_q_state;	/* width not needed - internal - DO NOT WRITE!!! */
 };
 
 #endif /* _ICE_LAN_TX_RX_H_ */
diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
index b22e71dc59d4..0f5a80269a7b 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.c
+++ b/drivers/net/ethernet/intel/ice/ice_common.c
@@ -1467,7 +1467,6 @@ const struct ice_ctx_ele ice_tlan_ctx_info[] = {
 	ICE_CTX_STORE(ice_tlan_ctx, drop_ena,			1,	165),
 	ICE_CTX_STORE(ice_tlan_ctx, cache_prof_idx,		2,	166),
 	ICE_CTX_STORE(ice_tlan_ctx, pkt_shaper_prof_idx,	3,	168),
-	ICE_CTX_STORE(ice_tlan_ctx, int_q_state,		122,	171),
 	{ 0 }
 };
 

-- 
2.47.0.265.g4ca455297942

[PATCH net-next v5 5/9] ice: use structures to keep track of queue context size

[Jacob Keller]

The ice Tx and Rx queue context are currently stored as arrays of bytes
with defined size (ICE_RXQ_CTX_SZ and ICE_TXQ_CTX_SZ). The packed queue
context is often passed to other functions as a simple u8 * pointer, which
does not allow tracking the size. This makes the queue context API easy to
misuse, as you can pass an arbitrary u8 array or pointer.

Introduce wrapper typedefs which use a __packed structure that has the
proper fixed size for the Tx and Rx context buffers. This enables the
compiler to track the size of the value and ensures that passing the wrong
buffer size will be detected by the compiler.

The existing APIs do not benefit much from this change, however the
wrapping structures will be used to simplify the arguments of new packing
functions based on the recently introduced pack_fields API.

Co-developed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_adminq_cmd.h | 11 +++++++++--
 drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h  |  2 --
 drivers/net/ethernet/intel/ice/ice_base.c       |  2 +-
 drivers/net/ethernet/intel/ice/ice_common.c     | 24 +++++++++++-------------
 4 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_adminq_cmd.h b/drivers/net/ethernet/intel/ice/ice_adminq_cmd.h
index 1f01f3501d6b..a0ec9c97c2d7 100644
--- a/drivers/net/ethernet/intel/ice/ice_adminq_cmd.h
+++ b/drivers/net/ethernet/intel/ice/ice_adminq_cmd.h
@@ -12,6 +12,13 @@
 #define ICE_AQC_TOPO_MAX_LEVEL_NUM	0x9
 #define ICE_AQ_SET_MAC_FRAME_SIZE_MAX	9728
 
+#define ICE_RXQ_CTX_SIZE_DWORDS		8
+#define ICE_RXQ_CTX_SZ			(ICE_RXQ_CTX_SIZE_DWORDS * sizeof(u32))
+#define ICE_TXQ_CTX_SZ			22
+
+typedef struct __packed { u8 buf[ICE_RXQ_CTX_SZ]; } ice_rxq_ctx_buf_t;
+typedef struct __packed { u8 buf[ICE_TXQ_CTX_SZ]; } ice_txq_ctx_buf_t;
+
 struct ice_aqc_generic {
 	__le32 param0;
 	__le32 param1;
@@ -2067,10 +2074,10 @@ struct ice_aqc_add_txqs_perq {
 	__le16 txq_id;
 	u8 rsvd[2];
 	__le32 q_teid;
-	u8 txq_ctx[22];
+	ice_txq_ctx_buf_t txq_ctx;
 	u8 rsvd2[2];
 	struct ice_aqc_txsched_elem info;
-};
+} __packed;
 
 /* The format of the command buffer for Add Tx LAN Queues (0x0C30)
  * is an array of the following structs. Please note that the length of
diff --git a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
index 0e8ed8c226e6..a76e5b0e7861 100644
--- a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
+++ b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
@@ -371,8 +371,6 @@ enum ice_rx_flex_desc_status_error_1_bits {
 	ICE_RX_FLEX_DESC_STATUS1_LAST /* this entry must be last!!! */
 };
 
-#define ICE_RXQ_CTX_SIZE_DWORDS		8
-#define ICE_RXQ_CTX_SZ			(ICE_RXQ_CTX_SIZE_DWORDS * sizeof(u32))
 #define ICE_TX_CMPLTNQ_CTX_SIZE_DWORDS	22
 #define ICE_TX_DRBELL_Q_CTX_SIZE_DWORDS	5
 #define GLTCLAN_CQ_CNTX(i, CQ)		(GLTCLAN_CQ_CNTX0(CQ) + ((i) * 0x0800))
diff --git a/drivers/net/ethernet/intel/ice/ice_base.c b/drivers/net/ethernet/intel/ice/ice_base.c
index 3a8e156d7d86..260942877968 100644
--- a/drivers/net/ethernet/intel/ice/ice_base.c
+++ b/drivers/net/ethernet/intel/ice/ice_base.c
@@ -909,7 +909,7 @@ ice_vsi_cfg_txq(struct ice_vsi *vsi, struct ice_tx_ring *ring,
 	ice_setup_tx_ctx(ring, &tlan_ctx, pf_q);
 	/* copy context contents into the qg_buf */
 	qg_buf->txqs[0].txq_id = cpu_to_le16(pf_q);
-	ice_set_ctx(hw, (u8 *)&tlan_ctx, qg_buf->txqs[0].txq_ctx,
+	ice_set_ctx(hw, (u8 *)&tlan_ctx, (u8 *)&qg_buf->txqs[0].txq_ctx,
 		    ice_tlan_ctx_info);
 
 	/* init queue specific tail reg. It is referred as
diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
index 0f5a80269a7b..48d95cb49864 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.c
+++ b/drivers/net/ethernet/intel/ice/ice_common.c
@@ -1359,29 +1359,27 @@ int ice_reset(struct ice_hw *hw, enum ice_reset_req req)
 /**
  * ice_copy_rxq_ctx_to_hw
  * @hw: pointer to the hardware structure
- * @ice_rxq_ctx: pointer to the rxq context
+ * @rxq_ctx: pointer to the packed Rx queue context
  * @rxq_index: the index of the Rx queue
  *
  * Copies rxq context from dense structure to HW register space
  */
-static int
-ice_copy_rxq_ctx_to_hw(struct ice_hw *hw, u8 *ice_rxq_ctx, u32 rxq_index)
+static int ice_copy_rxq_ctx_to_hw(struct ice_hw *hw,
+				  const ice_rxq_ctx_buf_t *rxq_ctx,
+				  u32 rxq_index)
 {
 	u8 i;
 
-	if (!ice_rxq_ctx)
-		return -EINVAL;
-
 	if (rxq_index > QRX_CTRL_MAX_INDEX)
 		return -EINVAL;
 
 	/* Copy each dword separately to HW */
 	for (i = 0; i < ICE_RXQ_CTX_SIZE_DWORDS; i++) {
-		wr32(hw, QRX_CONTEXT(i, rxq_index),
-		     *((u32 *)(ice_rxq_ctx + (i * sizeof(u32)))));
+		u32 ctx = ((const u32 *)rxq_ctx)[i];
 
-		ice_debug(hw, ICE_DBG_QCTX, "qrxdata[%d]: %08X\n", i,
-			  *((u32 *)(ice_rxq_ctx + (i * sizeof(u32)))));
+		wr32(hw, QRX_CONTEXT(i, rxq_index), ctx);
+
+		ice_debug(hw, ICE_DBG_QCTX, "qrxdata[%d]: %08X\n", i, ctx);
 	}
 
 	return 0;
@@ -1426,15 +1424,15 @@ static const struct ice_ctx_ele ice_rlan_ctx_info[] = {
 int ice_write_rxq_ctx(struct ice_hw *hw, struct ice_rlan_ctx *rlan_ctx,
 		      u32 rxq_index)
 {
-	u8 ctx_buf[ICE_RXQ_CTX_SZ] = { 0 };
+	ice_rxq_ctx_buf_t buf = {};
 
 	if (!rlan_ctx)
 		return -EINVAL;
 
 	rlan_ctx->prefena = 1;
 
-	ice_set_ctx(hw, (u8 *)rlan_ctx, ctx_buf, ice_rlan_ctx_info);
-	return ice_copy_rxq_ctx_to_hw(hw, ctx_buf, rxq_index);
+	ice_set_ctx(hw, (u8 *)rlan_ctx, (u8 *)&buf, ice_rlan_ctx_info);
+	return ice_copy_rxq_ctx_to_hw(hw, &buf, rxq_index);
 }
 
 /* LAN Tx Queue Context */

-- 
2.47.0.265.g4ca455297942

[PATCH net-next v5 6/9] ice: use <linux/packing.h> for Tx and Rx queue context data

[Jacob Keller]

The ice driver needs to write the Tx and Rx queue context when programming
Tx and Rx queues. This is currently done using some bespoke custom logic
via the ice_set_ctx() and its helper functions, along with bit position
definitions in the ice_tlan_ctx_info and ice_rlan_ctx_info structures.

This logic does work, but is problematic for several reasons:

1) ice_set_ctx requires a helper function for each byte size being packed,
   as it uses a separate function to pack u8, u16, u32, and u64 fields.
   This requires 4 functions which contain near-duplicate logic with the
   types changed out.

2) The logic in the ice_pack_ctx_word, ice_pack_ctx_dword, and
   ice_pack_ctx_qword does not handle values which straddle alignment
   boundaries very well. This requires that several fields in the
   ice_tlan_ctx_info and ice_rlan_ctx_info be a size larger than their bit
   size should require.

3) Future support for live migration will require adding unpacking
   functions to take the packed hardware context and unpack it into the
   ice_rlan_ctx and ice_tlan_ctx structures. Implementing this would
   require implementing ice_get_ctx, and its associated helper functions,
   which essentially doubles the amount of code required.

The Linux kernel has had a packing library that can handle this logic since
commit 554aae35007e ("lib: Add support for generic packing operations").
The library was recently extended with support for packing or unpacking an
array of fields, with a similar structure as the ice_ctx_ele structure.

Replace the ice-specific ice_set_ctx() logic with the recently added
pack_fields and packed_field_s infrastructure from <linux/packing.h>

For API simplicity, the Tx and Rx queue context are programmed using
separate ice_pack_txq_ctx() and ice_pack_rxq_ctx(). This avoids needing to
export the packed_field_s arrays. The functions can pointers to the
appropriate ice_txq_ctx_buf_t and ice_rxq_ctx_buf_t types, ensuring that
only buffers of the appropriate size are passed.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_common.h    |   5 +-
 drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h |  14 --
 drivers/net/ethernet/intel/ice/ice_base.c      |   3 +-
 drivers/net/ethernet/intel/ice/ice_common.c    | 243 ++++---------------------
 drivers/net/ethernet/intel/Kconfig             |   1 +
 5 files changed, 42 insertions(+), 224 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_common.h b/drivers/net/ethernet/intel/ice/ice_common.h
index 27208a60cece..a68bea3934e3 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.h
+++ b/drivers/net/ethernet/intel/ice/ice_common.h
@@ -92,9 +92,8 @@ ice_aq_set_rss_key(struct ice_hw *hw, u16 vsi_handle,
 bool ice_check_sq_alive(struct ice_hw *hw, struct ice_ctl_q_info *cq);
 int ice_aq_q_shutdown(struct ice_hw *hw, bool unloading);
 void ice_fill_dflt_direct_cmd_desc(struct ice_aq_desc *desc, u16 opcode);
-extern const struct ice_ctx_ele ice_tlan_ctx_info[];
-int ice_set_ctx(struct ice_hw *hw, u8 *src_ctx, u8 *dest_ctx,
-		const struct ice_ctx_ele *ce_info);
+
+void ice_pack_txq_ctx(const struct ice_tlan_ctx *ctx, ice_txq_ctx_buf_t *buf);
 
 extern struct mutex ice_global_cfg_lock_sw;
 
diff --git a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
index a76e5b0e7861..31d4a445d640 100644
--- a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
+++ b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
@@ -408,20 +408,6 @@ struct ice_rlan_ctx {
 	u8 prefena;	/* NOTE: normally must be set to 1 at init */
 };
 
-struct ice_ctx_ele {
-	u16 offset;
-	u16 size_of;
-	u16 width;
-	u16 lsb;
-};
-
-#define ICE_CTX_STORE(_struct, _ele, _width, _lsb) {	\
-	.offset = offsetof(struct _struct, _ele),	\
-	.size_of = sizeof_field(struct _struct, _ele),	\
-	.width = _width,				\
-	.lsb = _lsb,					\
-}
-
 /* for hsplit_0 field of Rx RLAN context */
 enum ice_rlan_ctx_rx_hsplit_0 {
 	ICE_RLAN_RX_HSPLIT_0_NO_SPLIT		= 0,
diff --git a/drivers/net/ethernet/intel/ice/ice_base.c b/drivers/net/ethernet/intel/ice/ice_base.c
index 260942877968..0a325dec804e 100644
--- a/drivers/net/ethernet/intel/ice/ice_base.c
+++ b/drivers/net/ethernet/intel/ice/ice_base.c
@@ -909,8 +909,7 @@ ice_vsi_cfg_txq(struct ice_vsi *vsi, struct ice_tx_ring *ring,
 	ice_setup_tx_ctx(ring, &tlan_ctx, pf_q);
 	/* copy context contents into the qg_buf */
 	qg_buf->txqs[0].txq_id = cpu_to_le16(pf_q);
-	ice_set_ctx(hw, (u8 *)&tlan_ctx, (u8 *)&qg_buf->txqs[0].txq_ctx,
-		    ice_tlan_ctx_info);
+	ice_pack_txq_ctx(&tlan_ctx, &qg_buf->txqs[0].txq_ctx);
 
 	/* init queue specific tail reg. It is referred as
 	 * transmit comm scheduler queue doorbell.
diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
index 48d95cb49864..a743aede7f59 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.c
+++ b/drivers/net/ethernet/intel/ice/ice_common.c
@@ -6,6 +6,7 @@
 #include "ice_adminq_cmd.h"
 #include "ice_flow.h"
 #include "ice_ptp_hw.h"
+#include <linux/packing.h>
 
 #define ICE_PF_RESET_WAIT_COUNT	300
 #define ICE_MAX_NETLIST_SIZE	10
@@ -1385,9 +1386,12 @@ static int ice_copy_rxq_ctx_to_hw(struct ice_hw *hw,
 	return 0;
 }
 
+#define ICE_CTX_STORE(struct_name, struct_field, width, lsb) \
+	PACKED_FIELD((lsb) + (width) - 1, (lsb), struct struct_name, struct_field)
+
 /* LAN Rx Queue Context */
-static const struct ice_ctx_ele ice_rlan_ctx_info[] = {
-	/* Field		Width	LSB */
+static DECLARE_PACKED_FIELDS_S(ice_rlan_ctx_fields) = {
+				 /* Field		Width	LSB */
 	ICE_CTX_STORE(ice_rlan_ctx, head,		13,	0),
 	ICE_CTX_STORE(ice_rlan_ctx, cpuid,		8,	13),
 	ICE_CTX_STORE(ice_rlan_ctx, base,		57,	32),
@@ -1408,9 +1412,23 @@ static const struct ice_ctx_ele ice_rlan_ctx_info[] = {
 	ICE_CTX_STORE(ice_rlan_ctx, tphhead_ena,	1,	196),
 	ICE_CTX_STORE(ice_rlan_ctx, lrxqthresh,		3,	198),
 	ICE_CTX_STORE(ice_rlan_ctx, prefena,		1,	201),
-	{ 0 }
 };
 
+/**
+ * ice_pack_rxq_ctx - Pack Rx queue context into a HW buffer
+ * @ctx: the Rx queue context to pack
+ * @buf: the HW buffer to pack into
+ *
+ * Pack the Rx queue context from the CPU-friendly unpacked buffer into its
+ * bit-packed HW layout.
+ */
+static void ice_pack_rxq_ctx(const struct ice_rlan_ctx *ctx,
+			     ice_rxq_ctx_buf_t *buf)
+{
+	pack_fields(buf, ctx, ice_rlan_ctx_fields,
+		    QUIRK_LITTLE_ENDIAN | QUIRK_LSW32_IS_FIRST);
+}
+
 /**
  * ice_write_rxq_ctx
  * @hw: pointer to the hardware structure
@@ -1431,12 +1449,13 @@ int ice_write_rxq_ctx(struct ice_hw *hw, struct ice_rlan_ctx *rlan_ctx,
 
 	rlan_ctx->prefena = 1;
 
-	ice_set_ctx(hw, (u8 *)rlan_ctx, (u8 *)&buf, ice_rlan_ctx_info);
+	ice_pack_rxq_ctx(rlan_ctx, &buf);
+
 	return ice_copy_rxq_ctx_to_hw(hw, &buf, rxq_index);
 }
 
 /* LAN Tx Queue Context */
-const struct ice_ctx_ele ice_tlan_ctx_info[] = {
+static DECLARE_PACKED_FIELDS_S(ice_tlan_ctx_fields) = {
 				    /* Field			Width	LSB */
 	ICE_CTX_STORE(ice_tlan_ctx, base,			57,	0),
 	ICE_CTX_STORE(ice_tlan_ctx, port_num,			3,	57),
@@ -1465,9 +1484,22 @@ const struct ice_ctx_ele ice_tlan_ctx_info[] = {
 	ICE_CTX_STORE(ice_tlan_ctx, drop_ena,			1,	165),
 	ICE_CTX_STORE(ice_tlan_ctx, cache_prof_idx,		2,	166),
 	ICE_CTX_STORE(ice_tlan_ctx, pkt_shaper_prof_idx,	3,	168),
-	{ 0 }
 };
 
+/**
+ * ice_pack_txq_ctx - Pack Tx queue context into a HW buffer
+ * @ctx: the Tx queue context to pack
+ * @buf: the HW buffer to pack into
+ *
+ * Pack the Tx queue context from the CPU-friendly unpacked buffer into its
+ * bit-packed HW layout.
+ */
+void ice_pack_txq_ctx(const struct ice_tlan_ctx *ctx, ice_txq_ctx_buf_t *buf)
+{
+	pack_fields(buf, ctx, ice_tlan_ctx_fields,
+		    QUIRK_LITTLE_ENDIAN | QUIRK_LSW32_IS_FIRST);
+}
+
 /* Sideband Queue command wrappers */
 
 /**
@@ -4545,205 +4577,6 @@ ice_aq_add_rdma_qsets(struct ice_hw *hw, u8 num_qset_grps,
 
 /* End of FW Admin Queue command wrappers */
 
-/**
- * ice_pack_ctx_byte - write a byte to a packed context structure
- * @src_ctx: unpacked source context structure
- * @dest_ctx: packed destination context data
- * @ce_info: context element description
- */
-static void ice_pack_ctx_byte(u8 *src_ctx, u8 *dest_ctx,
-			      const struct ice_ctx_ele *ce_info)
-{
-	u8 src_byte, dest_byte, mask;
-	u8 *from, *dest;
-	u16 shift_width;
-
-	/* copy from the next struct field */
-	from = src_ctx + ce_info->offset;
-
-	/* prepare the bits and mask */
-	shift_width = ce_info->lsb % 8;
-	mask = GENMASK(ce_info->width - 1 + shift_width, shift_width);
-
-	src_byte = *from;
-	src_byte <<= shift_width;
-	src_byte &= mask;
-
-	/* get the current bits from the target bit string */
-	dest = dest_ctx + (ce_info->lsb / 8);
-
-	memcpy(&dest_byte, dest, sizeof(dest_byte));
-
-	dest_byte &= ~mask;	/* get the bits not changing */
-	dest_byte |= src_byte;	/* add in the new bits */
-
-	/* put it all back */
-	memcpy(dest, &dest_byte, sizeof(dest_byte));
-}
-
-/**
- * ice_pack_ctx_word - write a word to a packed context structure
- * @src_ctx: unpacked source context structure
- * @dest_ctx: packed destination context data
- * @ce_info: context element description
- */
-static void ice_pack_ctx_word(u8 *src_ctx, u8 *dest_ctx,
-			      const struct ice_ctx_ele *ce_info)
-{
-	u16 src_word, mask;
-	__le16 dest_word;
-	u8 *from, *dest;
-	u16 shift_width;
-
-	/* copy from the next struct field */
-	from = src_ctx + ce_info->offset;
-
-	/* prepare the bits and mask */
-	shift_width = ce_info->lsb % 8;
-	mask = GENMASK(ce_info->width - 1 + shift_width, shift_width);
-
-	/* don't swizzle the bits until after the mask because the mask bits
-	 * will be in a different bit position on big endian machines
-	 */
-	src_word = *(u16 *)from;
-	src_word <<= shift_width;
-	src_word &= mask;
-
-	/* get the current bits from the target bit string */
-	dest = dest_ctx + (ce_info->lsb / 8);
-
-	memcpy(&dest_word, dest, sizeof(dest_word));
-
-	dest_word &= ~(cpu_to_le16(mask));	/* get the bits not changing */
-	dest_word |= cpu_to_le16(src_word);	/* add in the new bits */
-
-	/* put it all back */
-	memcpy(dest, &dest_word, sizeof(dest_word));
-}
-
-/**
- * ice_pack_ctx_dword - write a dword to a packed context structure
- * @src_ctx: unpacked source context structure
- * @dest_ctx: packed destination context data
- * @ce_info: context element description
- */
-static void ice_pack_ctx_dword(u8 *src_ctx, u8 *dest_ctx,
-			       const struct ice_ctx_ele *ce_info)
-{
-	u32 src_dword, mask;
-	__le32 dest_dword;
-	u8 *from, *dest;
-	u16 shift_width;
-
-	/* copy from the next struct field */
-	from = src_ctx + ce_info->offset;
-
-	/* prepare the bits and mask */
-	shift_width = ce_info->lsb % 8;
-	mask = GENMASK(ce_info->width - 1 + shift_width, shift_width);
-
-	/* don't swizzle the bits until after the mask because the mask bits
-	 * will be in a different bit position on big endian machines
-	 */
-	src_dword = *(u32 *)from;
-	src_dword <<= shift_width;
-	src_dword &= mask;
-
-	/* get the current bits from the target bit string */
-	dest = dest_ctx + (ce_info->lsb / 8);
-
-	memcpy(&dest_dword, dest, sizeof(dest_dword));
-
-	dest_dword &= ~(cpu_to_le32(mask));	/* get the bits not changing */
-	dest_dword |= cpu_to_le32(src_dword);	/* add in the new bits */
-
-	/* put it all back */
-	memcpy(dest, &dest_dword, sizeof(dest_dword));
-}
-
-/**
- * ice_pack_ctx_qword - write a qword to a packed context structure
- * @src_ctx: unpacked source context structure
- * @dest_ctx: packed destination context data
- * @ce_info: context element description
- */
-static void ice_pack_ctx_qword(u8 *src_ctx, u8 *dest_ctx,
-			       const struct ice_ctx_ele *ce_info)
-{
-	u64 src_qword, mask;
-	__le64 dest_qword;
-	u8 *from, *dest;
-	u16 shift_width;
-
-	/* copy from the next struct field */
-	from = src_ctx + ce_info->offset;
-
-	/* prepare the bits and mask */
-	shift_width = ce_info->lsb % 8;
-	mask = GENMASK_ULL(ce_info->width - 1 + shift_width, shift_width);
-
-	/* don't swizzle the bits until after the mask because the mask bits
-	 * will be in a different bit position on big endian machines
-	 */
-	src_qword = *(u64 *)from;
-	src_qword <<= shift_width;
-	src_qword &= mask;
-
-	/* get the current bits from the target bit string */
-	dest = dest_ctx + (ce_info->lsb / 8);
-
-	memcpy(&dest_qword, dest, sizeof(dest_qword));
-
-	dest_qword &= ~(cpu_to_le64(mask));	/* get the bits not changing */
-	dest_qword |= cpu_to_le64(src_qword);	/* add in the new bits */
-
-	/* put it all back */
-	memcpy(dest, &dest_qword, sizeof(dest_qword));
-}
-
-/**
- * ice_set_ctx - set context bits in packed structure
- * @hw: pointer to the hardware structure
- * @src_ctx:  pointer to a generic non-packed context structure
- * @dest_ctx: pointer to memory for the packed structure
- * @ce_info: List of Rx context elements
- */
-int ice_set_ctx(struct ice_hw *hw, u8 *src_ctx, u8 *dest_ctx,
-		const struct ice_ctx_ele *ce_info)
-{
-	int f;
-
-	for (f = 0; ce_info[f].width; f++) {
-		/* We have to deal with each element of the FW response
-		 * using the correct size so that we are correct regardless
-		 * of the endianness of the machine.
-		 */
-		if (ce_info[f].width > (ce_info[f].size_of * BITS_PER_BYTE)) {
-			ice_debug(hw, ICE_DBG_QCTX, "Field %d width of %d bits larger than size of %d byte(s) ... skipping write\n",
-				  f, ce_info[f].width, ce_info[f].size_of);
-			continue;
-		}
-		switch (ce_info[f].size_of) {
-		case sizeof(u8):
-			ice_pack_ctx_byte(src_ctx, dest_ctx, &ce_info[f]);
-			break;
-		case sizeof(u16):
-			ice_pack_ctx_word(src_ctx, dest_ctx, &ce_info[f]);
-			break;
-		case sizeof(u32):
-			ice_pack_ctx_dword(src_ctx, dest_ctx, &ce_info[f]);
-			break;
-		case sizeof(u64):
-			ice_pack_ctx_qword(src_ctx, dest_ctx, &ce_info[f]);
-			break;
-		default:
-			return -EINVAL;
-		}
-	}
-
-	return 0;
-}
-
 /**
  * ice_get_lan_q_ctx - get the LAN queue context for the given VSI and TC
  * @hw: pointer to the HW struct
diff --git a/drivers/net/ethernet/intel/Kconfig b/drivers/net/ethernet/intel/Kconfig
index 20bc40eec487..24ec9a4f1ffa 100644
--- a/drivers/net/ethernet/intel/Kconfig
+++ b/drivers/net/ethernet/intel/Kconfig
@@ -292,6 +292,7 @@ config ICE
 	select DIMLIB
 	select LIBIE
 	select NET_DEVLINK
+	select PACKING
 	select PLDMFW
 	select DPLL
 	help

-- 
2.47.0.265.g4ca455297942

[PATCH net-next v5 7/9] ice: reduce size of queue context fields

[Jacob Keller]

The ice_rlan_ctx and ice_tlan_ctx structures have some fields which are
intentionally sized larger necessary relative to the packed sizes the data
must fit into. This was done because the original ice_set_ctx() function
and its helpers did not correctly handle packing when the packed bits
straddled a byte. This is no longer the case with the use of the
<linux/packing.h> implementation.

Save some bytes in these structures by sizing the variables to the number
of bytes the actual bitpacked fields fit into.

There are a couple of gaps left in the structure, which is a result of the
fields being in the order they appear in the packed bit layout, but where
alignment forces some extra gaps. We could fix this, saving ~8 bytes from
each structure. However, these structures are not used heavily, and the
resulting savings is minimal:

$ bloat-o-meter ice-before-reorder.ko ice-after-reorder.ko
add/remove: 0/0 grow/shrink: 1/1 up/down: 26/-70 (-44)
Function                                     old     new   delta
ice_vsi_cfg_txq                             1873    1899     +26
ice_setup_rx_ctx.constprop                  1529    1459     -70
Total: Before=1459555, After=1459511, chg -0.00%

Thus, the fields are left in the same order as the packed bit layout,
despite the gaps this causes.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h | 32 ++++++++------------------
 1 file changed, 10 insertions(+), 22 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
index 31d4a445d640..1479b45738af 100644
--- a/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
+++ b/drivers/net/ethernet/intel/ice/ice_lan_tx_rx.h
@@ -375,23 +375,17 @@ enum ice_rx_flex_desc_status_error_1_bits {
 #define ICE_TX_DRBELL_Q_CTX_SIZE_DWORDS	5
 #define GLTCLAN_CQ_CNTX(i, CQ)		(GLTCLAN_CQ_CNTX0(CQ) + ((i) * 0x0800))
 
-/* RLAN Rx queue context data
- *
- * The sizes of the variables may be larger than needed due to crossing byte
- * boundaries. If we do not have the width of the variable set to the correct
- * size then we could end up shifting bits off the top of the variable when the
- * variable is at the top of a byte and crosses over into the next byte.
- */
+/* RLAN Rx queue context data */
 struct ice_rlan_ctx {
 	u16 head;
-	u16 cpuid; /* bigger than needed, see above for reason */
+	u8 cpuid;
 #define ICE_RLAN_BASE_S 7
 	u64 base;
 	u16 qlen;
 #define ICE_RLAN_CTX_DBUF_S 7
-	u16 dbuf; /* bigger than needed, see above for reason */
+	u8 dbuf;
 #define ICE_RLAN_CTX_HBUF_S 6
-	u16 hbuf; /* bigger than needed, see above for reason */
+	u8 hbuf;
 	u8 dtype;
 	u8 dsize;
 	u8 crcstrip;
@@ -399,12 +393,12 @@ struct ice_rlan_ctx {
 	u8 hsplit_0;
 	u8 hsplit_1;
 	u8 showiv;
-	u32 rxmax; /* bigger than needed, see above for reason */
+	u16 rxmax;
 	u8 tphrdesc_ena;
 	u8 tphwdesc_ena;
 	u8 tphdata_ena;
 	u8 tphhead_ena;
-	u16 lrxqthresh; /* bigger than needed, see above for reason */
+	u8 lrxqthresh;
 	u8 prefena;	/* NOTE: normally must be set to 1 at init */
 };
 
@@ -535,18 +529,12 @@ enum ice_tx_ctx_desc_eipt_offload {
 #define ICE_LAN_TXQ_MAX_QGRPS	127
 #define ICE_LAN_TXQ_MAX_QDIS	1023
 
-/* Tx queue context data
- *
- * The sizes of the variables may be larger than needed due to crossing byte
- * boundaries. If we do not have the width of the variable set to the correct
- * size then we could end up shifting bits off the top of the variable when the
- * variable is at the top of a byte and crosses over into the next byte.
- */
+/* Tx queue context data */
 struct ice_tlan_ctx {
 #define ICE_TLAN_CTX_BASE_S	7
 	u64 base;		/* base is defined in 128-byte units */
 	u8 port_num;
-	u16 cgd_num;		/* bigger than needed, see above for reason */
+	u8 cgd_num;
 	u8 pf_num;
 	u16 vmvf_num;
 	u8 vmvf_type;
@@ -557,7 +545,7 @@ struct ice_tlan_ctx {
 	u8 tsyn_ena;
 	u8 internal_usage_flag;
 	u8 alt_vlan;
-	u16 cpuid;		/* bigger than needed, see above for reason */
+	u8 cpuid;
 	u8 wb_mode;
 	u8 tphrd_desc;
 	u8 tphrd;
@@ -566,7 +554,7 @@ struct ice_tlan_ctx {
 	u16 qnum_in_func;
 	u8 itr_notification_mode;
 	u8 adjust_prof_id;
-	u32 qlen;		/* bigger than needed, see above for reason */
+	u16 qlen;
 	u8 quanta_prof_idx;
 	u8 tso_ena;
 	u16 tso_qnum;

-- 
2.47.0.265.g4ca455297942

[PATCH net-next v5 8/9] ice: move prefetch enable to ice_setup_rx_ctx

[Jacob Keller]

The ice_write_rxq_ctx() function is responsible for programming the Rx
Queue context into hardware. It receives the configuration in unpacked form
via the ice_rlan_ctx structure.

This function unconditionally modifies the context to set the prefetch
enable bit. This was done by commit c31a5c25bb19 ("ice: Always set prefena
when configuring an Rx queue"). Setting this bit makes sense, since
prefetching descriptors is almost always the preferred behavior.

However, the ice_write_rxq_ctx() function is not the place that actually
defines the queue context. We initialize the Rx Queue context in
ice_setup_rx_ctx(). It is surprising to have the Rx queue context changed
by a function who's responsibility is to program the given context to
hardware.

Following the principle of least surprise, move the setting of the prefetch
enable bit out of ice_write_rxq_ctx() and into the ice_setup_rx_ctx().

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_base.c   | 3 +++
 drivers/net/ethernet/intel/ice/ice_common.c | 9 +++------
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_base.c b/drivers/net/ethernet/intel/ice/ice_base.c
index 0a325dec804e..f1fbba19e4e4 100644
--- a/drivers/net/ethernet/intel/ice/ice_base.c
+++ b/drivers/net/ethernet/intel/ice/ice_base.c
@@ -453,6 +453,9 @@ static int ice_setup_rx_ctx(struct ice_rx_ring *ring)
 	/* Rx queue threshold in units of 64 */
 	rlan_ctx.lrxqthresh = 1;
 
+	/* Enable descriptor prefetch */
+	rlan_ctx.prefena = 1;
+
 	/* PF acts as uplink for switchdev; set flex descriptor with src_vsi
 	 * metadata and flags to allow redirecting to PR netdev
 	 */
diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
index a743aede7f59..e31d0ed55dff 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.c
+++ b/drivers/net/ethernet/intel/ice/ice_common.c
@@ -1430,14 +1430,13 @@ static void ice_pack_rxq_ctx(const struct ice_rlan_ctx *ctx,
 }
 
 /**
- * ice_write_rxq_ctx
+ * ice_write_rxq_ctx - Write Rx Queue context to hardware
  * @hw: pointer to the hardware structure
  * @rlan_ctx: pointer to the rxq context
  * @rxq_index: the index of the Rx queue
  *
- * Converts rxq context from sparse to dense structure and then writes
- * it to HW register space and enables the hardware to prefetch descriptors
- * instead of only fetching them on demand
+ * Pack the sparse Rx Queue context into dense hardware format and write it
+ * into the HW register space.
  */
 int ice_write_rxq_ctx(struct ice_hw *hw, struct ice_rlan_ctx *rlan_ctx,
 		      u32 rxq_index)
@@ -1447,8 +1446,6 @@ int ice_write_rxq_ctx(struct ice_hw *hw, struct ice_rlan_ctx *rlan_ctx,
 	if (!rlan_ctx)
 		return -EINVAL;
 
-	rlan_ctx->prefena = 1;
-
 	ice_pack_rxq_ctx(rlan_ctx, &buf);
 
 	return ice_copy_rxq_ctx_to_hw(hw, &buf, rxq_index);

-- 
2.47.0.265.g4ca455297942

[PATCH net-next v5 9/9] ice: cleanup Rx queue context programming functions

[Jacob Keller]

The ice_copy_rxq_ctx_to_hw() and ice_write_rxq_ctx() functions perform some
defensive checks which are typically frowned upon by kernel style
guidelines.

In particular, NULL checks on buffers which point to the stack are
discouraged, especially when the functions are static and only called once.
Checks of this sort only serve to hide potential programming error, as we
will not produce the normal crash dump on a NULL access.

In addition, ice_copy_rxq_ctx_to_hw() cannot fail in another way, so could
be made void.

Future support for VF Live Migration will need to introduce an inverse
function for reading Rx queue context from HW registers to unpack it, as
well as functions to pack and unpack Tx queue context from HW.

Rather than copying these style issues into the new functions, lets first
cleanup the existing code.

For the ice_copy_rxq_ctx_to_hw() function:

 * Move the Rx queue index check out of this function.
 * Convert the function to a void return.
 * Use a simple int variable instead of a u8 for the for loop index, and
   initialize it inside the for loop.
 * Update the function description to better align with kernel doc style.

For the ice_write_rxq_ctx() function:

 * Move the Rx queue index check into this function.
 * Update the function description with a Returns: to align with kernel doc
   style.

These changes align the existing write functions to current kernel
style, and will align with the style of the new functions added when we
implement live migration in a future series.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_common.c | 28 +++++++++++-----------------
 1 file changed, 11 insertions(+), 17 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
index e31d0ed55dff..da412fe5d1ff 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.c
+++ b/drivers/net/ethernet/intel/ice/ice_common.c
@@ -1358,32 +1358,23 @@ int ice_reset(struct ice_hw *hw, enum ice_reset_req req)
 }
 
 /**
- * ice_copy_rxq_ctx_to_hw
+ * ice_copy_rxq_ctx_to_hw - Copy packed Rx queue context to HW registers
  * @hw: pointer to the hardware structure
  * @rxq_ctx: pointer to the packed Rx queue context
  * @rxq_index: the index of the Rx queue
- *
- * Copies rxq context from dense structure to HW register space
  */
-static int ice_copy_rxq_ctx_to_hw(struct ice_hw *hw,
-				  const ice_rxq_ctx_buf_t *rxq_ctx,
-				  u32 rxq_index)
+static void ice_copy_rxq_ctx_to_hw(struct ice_hw *hw,
+				   const ice_rxq_ctx_buf_t *rxq_ctx,
+				   u32 rxq_index)
 {
-	u8 i;
-
-	if (rxq_index > QRX_CTRL_MAX_INDEX)
-		return -EINVAL;
-
 	/* Copy each dword separately to HW */
-	for (i = 0; i < ICE_RXQ_CTX_SIZE_DWORDS; i++) {
+	for (int i = 0; i < ICE_RXQ_CTX_SIZE_DWORDS; i++) {
 		u32 ctx = ((const u32 *)rxq_ctx)[i];
 
 		wr32(hw, QRX_CONTEXT(i, rxq_index), ctx);
 
 		ice_debug(hw, ICE_DBG_QCTX, "qrxdata[%d]: %08X\n", i, ctx);
 	}
-
-	return 0;
 }
 
 #define ICE_CTX_STORE(struct_name, struct_field, width, lsb) \
@@ -1432,23 +1423,26 @@ static void ice_pack_rxq_ctx(const struct ice_rlan_ctx *ctx,
 /**
  * ice_write_rxq_ctx - Write Rx Queue context to hardware
  * @hw: pointer to the hardware structure
- * @rlan_ctx: pointer to the rxq context
+ * @rlan_ctx: pointer to the unpacked Rx queue context
  * @rxq_index: the index of the Rx queue
  *
  * Pack the sparse Rx Queue context into dense hardware format and write it
  * into the HW register space.
+ *
+ * Return: 0 on success, or -EINVAL if the Rx queue index is invalid.
  */
 int ice_write_rxq_ctx(struct ice_hw *hw, struct ice_rlan_ctx *rlan_ctx,
 		      u32 rxq_index)
 {
 	ice_rxq_ctx_buf_t buf = {};
 
-	if (!rlan_ctx)
+	if (rxq_index > QRX_CTRL_MAX_INDEX)
 		return -EINVAL;
 
 	ice_pack_rxq_ctx(rlan_ctx, &buf);
+	ice_copy_rxq_ctx_to_hw(hw, &buf, rxq_index);
 
-	return ice_copy_rxq_ctx_to_hw(hw, &buf, rxq_index);
+	return 0;
 }
 
 /* LAN Tx Queue Context */

-- 
2.47.0.265.g4ca455297942

Re: [PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()

[kernel test robot]

Hi Jacob,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 774ca6d3bf24287ff60b7d6dd4171ebb6e47760a]

url:    https://github.com/intel-lab-lkp/linux/commits/Jacob-Keller/lib-packing-create-__pack-and-__unpack-variants-without-error-checking/20241111-161131
base:   774ca6d3bf24287ff60b7d6dd4171ebb6e47760a
patch link:    https://lore.kernel.org/r/20241111-packing-pack-fields-and-ice-implementation-v5-3-80c07349e6b7%40intel.com
patch subject: [PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()
config: x86_64-rhel-8.3 (https://download.01.org/0day-ci/archive/20241111/202411111823.Y2NHM1AE-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241111/202411111823.Y2NHM1AE-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411111823.Y2NHM1AE-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from scripts/mod/packed_fields.c:15:
   scripts/mod/packed_fields.c: In function 'handle_packed_field_symbol':
>> scripts/mod/packed_fields.c:134:23: warning: format '%u' expects argument of type 'unsigned int', but argument 5 has type 'Elf64_Xword' {aka 'long unsigned int'} [-Wformat=]
     134 |                 error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",
         |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     135 |                       mod->name, symname, sym->st_size, field_size);
         |                                           ~~~~~~~~~~~~
         |                                              |
         |                                              Elf64_Xword {aka long unsigned int}
   scripts/mod/modpost.h:207:51: note: in definition of macro 'error'
     207 | #define error(fmt, args...)     modpost_log(true, fmt, ##args)
         |                                                   ^~~
   scripts/mod/packed_fields.c:134:49: note: format string is defined here
     134 |                 error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",
         |                                                ~^
         |                                                 |
         |                                                 unsigned int
         |                                                %lu
--
   In file included from scripts/mod/packed_fields.c:15:
   scripts/mod/packed_fields.c: In function 'handle_packed_field_symbol':
>> scripts/mod/packed_fields.c:134:23: warning: format '%u' expects argument of type 'unsigned int', but argument 5 has type 'Elf64_Xword' {aka 'long unsigned int'} [-Wformat=]
     134 |                 error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",
         |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     135 |                       mod->name, symname, sym->st_size, field_size);
         |                                           ~~~~~~~~~~~~
         |                                              |
         |                                              Elf64_Xword {aka long unsigned int}
   scripts/mod/modpost.h:207:51: note: in definition of macro 'error'
     207 | #define error(fmt, args...)     modpost_log(true, fmt, ##args)
         |                                                   ^~~
   scripts/mod/packed_fields.c:134:49: note: format string is defined here
     134 |                 error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",
         |                                                ~^
         |                                                 |
         |                                                 unsigned int
         |                                                %lu


vim +134 scripts/mod/packed_fields.c

    99	
   100	void handle_packed_field_symbol(struct module *mod, struct elf_info *info,
   101					Elf_Sym *sym, const char *symname)
   102	{
   103		unsigned int secindex = get_secindex(info, sym);
   104		struct packed_field_elem elem = {}, prev = {};
   105		enum element_order order = FIRST_ELEMENT;
   106		enum field_type type = UNKNOWN_SECTION;
   107		size_t field_size, count;
   108		const void *data, *ptr;
   109		const char *section;
   110	
   111		/* Skip symbols without a name */
   112		if (*symname == '\0')
   113			return;
   114	
   115		/* Skip symbols with invalid sections */
   116		if (secindex >= info->num_sections)
   117			return;
   118	
   119		section = sec_name(info, secindex);
   120	
   121		if (strcmp(section, ".rodata.packed_fields_s") == 0)
   122			type = PACKED_FIELD_S;
   123		else if (strcmp(section, ".rodata.packed_fields_m") == 0)
   124			type = PACKED_FIELD_M;
   125	
   126		/* Other sections don't relate to packed fields */
   127		if (type == UNKNOWN_SECTION)
   128			return;
   129	
   130		field_size = field_type_to_size(type);
   131	
   132		/* check that the data is a multiple of the size */
   133		if (sym->st_size % field_size != 0) {
 > 134			error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()

[kernel test robot]

Hi Jacob,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 774ca6d3bf24287ff60b7d6dd4171ebb6e47760a]

url:    https://github.com/intel-lab-lkp/linux/commits/Jacob-Keller/lib-packing-create-__pack-and-__unpack-variants-without-error-checking/20241111-161131
base:   774ca6d3bf24287ff60b7d6dd4171ebb6e47760a
patch link:    https://lore.kernel.org/r/20241111-packing-pack-fields-and-ice-implementation-v5-3-80c07349e6b7%40intel.com
patch subject: [PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20241111/202411111817.tgnRn8v3-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241111/202411111817.tgnRn8v3-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411111817.tgnRn8v3-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> scripts/mod/packed_fields.c:135:29: warning: format specifies type 'unsigned int' but the argument has type 'Elf64_Xword' (aka 'unsigned long') [-Wformat]
     134 |                 error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",
         |                                                ~~
         |                                                %lu
     135 |                       mod->name, symname, sym->st_size, field_size);
         |                                           ^~~~~~~~~~~~
   scripts/mod/modpost.h:207:54: note: expanded from macro 'error'
     207 | #define error(fmt, args...)     modpost_log(true, fmt, ##args)
         |                                                   ~~~    ^~~~
   1 warning generated.
--
>> scripts/mod/packed_fields.c:135:29: warning: format specifies type 'unsigned int' but the argument has type 'Elf64_Xword' (aka 'unsigned long') [-Wformat]
     134 |                 error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",
         |                                                ~~
         |                                                %lu
     135 |                       mod->name, symname, sym->st_size, field_size);
         |                                           ^~~~~~~~~~~~
   scripts/mod/modpost.h:207:54: note: expanded from macro 'error'
     207 | #define error(fmt, args...)     modpost_log(true, fmt, ##args)
         |                                                   ~~~    ^~~~
   1 warning generated.
   In file included from arch/x86/kernel/asm-offsets.c:14:
   In file included from include/linux/suspend.h:5:
   In file included from include/linux/swap.h:9:
   In file included from include/linux/memcontrol.h:21:
   In file included from include/linux/mm.h:2213:
   include/linux/vmstat.h:504:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     504 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     505 |                            item];
         |                            ~~~~
   include/linux/vmstat.h:511:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     511 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     512 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
   include/linux/vmstat.h:524:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     524 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     525 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   4 warnings generated.


vim +135 scripts/mod/packed_fields.c

    99	
   100	void handle_packed_field_symbol(struct module *mod, struct elf_info *info,
   101					Elf_Sym *sym, const char *symname)
   102	{
   103		unsigned int secindex = get_secindex(info, sym);
   104		struct packed_field_elem elem = {}, prev = {};
   105		enum element_order order = FIRST_ELEMENT;
   106		enum field_type type = UNKNOWN_SECTION;
   107		size_t field_size, count;
   108		const void *data, *ptr;
   109		const char *section;
   110	
   111		/* Skip symbols without a name */
   112		if (*symname == '\0')
   113			return;
   114	
   115		/* Skip symbols with invalid sections */
   116		if (secindex >= info->num_sections)
   117			return;
   118	
   119		section = sec_name(info, secindex);
   120	
   121		if (strcmp(section, ".rodata.packed_fields_s") == 0)
   122			type = PACKED_FIELD_S;
   123		else if (strcmp(section, ".rodata.packed_fields_m") == 0)
   124			type = PACKED_FIELD_M;
   125	
   126		/* Other sections don't relate to packed fields */
   127		if (type == UNKNOWN_SECTION)
   128			return;
   129	
   130		field_size = field_type_to_size(type);
   131	
   132		/* check that the data is a multiple of the size */
   133		if (sym->st_size % field_size != 0) {
   134			error("[%s.ko] \"%s\" has size %u which is not a multiple of the field size (%zu)\n",
 > 135			      mod->name, symname, sym->st_size, field_size);

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()

[Masahiro Yamada]

On Mon, Nov 11, 2024 at 5:08 PM Jacob Keller <jacob.e.keller@intel.com> wrote:
>
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
>
> This is new API which caters to the following requirements:
>
> - Pack or unpack a large number of fields to/from a buffer with a small
>   code footprint. The current alternative is to open-code a large number
>   of calls to pack() and unpack(), or to use packing() to reduce that
>   number to half. But packing() is not const-correct.
>
> - Use unpacked numbers stored in variables smaller than u64. This
>   reduces the rodata footprint of the stored field arrays.
>
> - Perform error checking at compile time, rather than runtime, and return
>   void from the API functions. Because the C preprocessor can't generat
>   variable length code (loops), we can't easily use macros to implement the
>   overlap checks at compile time.
>
>   Instead, check for field ordering and overlap in modpost.

This is over-engineering.

modpost should not be bothered just for a small library like this.

Please do sanity checks within lib/packing.c



-- 
Best Regards
Masahiro Yamada

Re: [PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()

[Jacob Keller]

On 11/13/2024 12:32 PM, Masahiro Yamada wrote:
> On Mon, Nov 11, 2024 at 5:08 PM Jacob Keller <jacob.e.keller@intel.com> wrote:
>>
>> From: Vladimir Oltean <vladimir.oltean@nxp.com>
>>
>> This is new API which caters to the following requirements:
>>
>> - Pack or unpack a large number of fields to/from a buffer with a small
>>   code footprint. The current alternative is to open-code a large number
>>   of calls to pack() and unpack(), or to use packing() to reduce that
>>   number to half. But packing() is not const-correct.
>>
>> - Use unpacked numbers stored in variables smaller than u64. This
>>   reduces the rodata footprint of the stored field arrays.
>>
>> - Perform error checking at compile time, rather than runtime, and return
>>   void from the API functions. Because the C preprocessor can't generat
>>   variable length code (loops), we can't easily use macros to implement the
>>   overlap checks at compile time.
>>
>>   Instead, check for field ordering and overlap in modpost.
> 
> This is over-engineering.
> 
> modpost should not be bothered just for a small library like this.
> 
> Please do sanity checks within lib/packing.c
> 

With the goal of maintaining compile time checks, we end up either
needing to use generated macros which are O(N^2) if we allow arbitrary
overlap. If we instead allow only only ascending or descending order,
this would drop to O(N) which would avoid needing to have 20k lines of
generated code for the case with 50. I think we could implement them
without forcing drivers to specifically call the correct macro by using
something like __builtin_choose_expr(), tho implementing that macro to
select could be quite long.

Otherwise we can fall back to either module load time checks, or go all
the way back to only sanity checking at executing of pack_fields or
unpack_fields.

Re: [PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()

[Masahiro Yamada]

On Thu, Nov 14, 2024 at 6:04 AM Jacob Keller <jacob.e.keller@intel.com> wrote:
>
>
>
> On 11/13/2024 12:32 PM, Masahiro Yamada wrote:
> > On Mon, Nov 11, 2024 at 5:08 PM Jacob Keller <jacob.e.keller@intel.com> wrote:
> >>
> >> From: Vladimir Oltean <vladimir.oltean@nxp.com>
> >>
> >> This is new API which caters to the following requirements:
> >>
> >> - Pack or unpack a large number of fields to/from a buffer with a small
> >>   code footprint. The current alternative is to open-code a large number
> >>   of calls to pack() and unpack(), or to use packing() to reduce that
> >>   number to half. But packing() is not const-correct.
> >>
> >> - Use unpacked numbers stored in variables smaller than u64. This
> >>   reduces the rodata footprint of the stored field arrays.
> >>
> >> - Perform error checking at compile time, rather than runtime, and return
> >>   void from the API functions. Because the C preprocessor can't generat
> >>   variable length code (loops), we can't easily use macros to implement the
> >>   overlap checks at compile time.
> >>
> >>   Instead, check for field ordering and overlap in modpost.
> >
> > This is over-engineering.
> >
> > modpost should not be bothered just for a small library like this.
> >
> > Please do sanity checks within lib/packing.c
> >
>
> With the goal of maintaining compile time checks, we end up either
> needing to use generated macros which are O(N^2) if we allow arbitrary
> overlap. If we instead allow only only ascending or descending order,
> this would drop to O(N) which would avoid needing to have 20k lines of
> generated code for the case with 50. I think we could implement them
> without forcing drivers to specifically call the correct macro by using
> something like __builtin_choose_expr(), tho implementing that macro to
> select could be quite long.


WIth Clang, the following check seems to work,
but with GCC, it works only when the array size is small.


#define PACKED_FIELDS_OUT_OF_ORDER(fields) \
({ \
        bool res = false; \
        for (unsigned int i = 1; i < ARRAY_SIZE(fields); i++) \
                res |= fields[i - 1].startbit < fields[i].startbit; \
        res; \
})

#define PACKED_FIELDS_OVERWRAP(fields) \
({ \
        bool res = false; \
        for (unsigned int i = 1; i < ARRAY_SIZE(fields); i++) \
                res |= fields[i - 1].endbit <= fields[i].startbit; \
        res; \
})

/*
 * Clang cleverly computes this at compile time.
 * Unfortunately, GCC gives it up when the array size becomes large.
 * Turn on this check only when building the kernel with Clang.
 */
#ifdef CONFIG_CC_IS_CLANG
#define PACKED_FIELDS_SANITY_CHECKS(fields) \
        BUILD_BUG_ON_MSG(PACKED_FIELDS_OUT_OF_ORDER(fields), \
                         #fields ": not sorted decending order"); \
        BUILD_BUG_ON_MSG(PACKED_FIELDS_OVERWRAP(fields), \
                         #fields ": contains overwrap")
#else
#define PACKED_FIELDS_SANITY_CHECKS(fields)
#endif





> Otherwise we can fall back to either module load time checks, or go all
> the way back to only sanity checking at executing of pack_fields or
> unpack_fields.

Is it a big deal?
One solution is a run-time check (for GCC), which is a one-time
for booting or module loading.

Another is to rely on CICD running with Clang to detect overwraps.


It is horrible to include kernel-space structures from user-space
programs that run in a different architecture.

file2alias.c does this because it is only possible at compile-time,
but it is always the source of troubles.
I am search for a way to generate MODULE_ALIAS() without
including mod_devicetable.h from modpost.




--
Best Regards
Masahiro Yamada

Re: [PATCH net-next v5 3/9] lib: packing: add pack_fields() and unpack_fields()

[Jacob Keller]

On 11/15/2024 12:48 PM, Masahiro Yamada wrote:
> On Thu, Nov 14, 2024 at 6:04 AM Jacob Keller <jacob.e.keller@intel.com> wrote:
>> With the goal of maintaining compile time checks, we end up either
>> needing to use generated macros which are O(N^2) if we allow arbitrary
>> overlap. If we instead allow only only ascending or descending order,
>> this would drop to O(N) which would avoid needing to have 20k lines of
>> generated code for the case with 50. I think we could implement them
>> without forcing drivers to specifically call the correct macro by using
>> something like __builtin_choose_expr(), tho implementing that macro to
>> select could be quite long.
> 
> 
> WIth Clang, the following check seems to work,
> but with GCC, it works only when the array size is small.
> 
> 
> #define PACKED_FIELDS_OUT_OF_ORDER(fields) \
> ({ \
>         bool res = false; \
>         for (unsigned int i = 1; i < ARRAY_SIZE(fields); i++) \
>                 res |= fields[i - 1].startbit < fields[i].startbit; \
>         res; \
> })
> 
> #define PACKED_FIELDS_OVERWRAP(fields) \
> ({ \
>         bool res = false; \
>         for (unsigned int i = 1; i < ARRAY_SIZE(fields); i++) \
>                 res |= fields[i - 1].endbit <= fields[i].startbit; \
>         res; \
> })
> 
> /*
>  * Clang cleverly computes this at compile time.
>  * Unfortunately, GCC gives it up when the array size becomes large.
>  * Turn on this check only when building the kernel with Clang.
>  */
> #ifdef CONFIG_CC_IS_CLANG
> #define PACKED_FIELDS_SANITY_CHECKS(fields) \
>         BUILD_BUG_ON_MSG(PACKED_FIELDS_OUT_OF_ORDER(fields), \
>                          #fields ": not sorted decending order"); \
>         BUILD_BUG_ON_MSG(PACKED_FIELDS_OVERWRAP(fields), \
>                          #fields ": contains overwrap")
> #else
> #define PACKED_FIELDS_SANITY_CHECKS(fields)
> #endif
> 

This definitely seems compiler specific.

> 
> 
> 
> 
>> Otherwise we can fall back to either module load time checks, or go all
>> the way back to only sanity checking at executing of pack_fields or
>> unpack_fields.
> 
> Is it a big deal?
> One solution is a run-time check (for GCC), which is a one-time
> for booting or module loading.
> 
> Another is to rely on CICD running with Clang to detect overwraps.
> 
> 
> It is horrible to include kernel-space structures from user-space
> programs that run in a different architecture.
> 
> file2alias.c does this because it is only possible at compile-time,
> but it is always the source of troubles.
> I am search for a way to generate MODULE_ALIAS() without
> including mod_devicetable.h from modpost.
> 

Yea, I agree modpost is pretty ugly, and I'm happy to drop it.

I think I've managed to get something that works in GCC and Clang with
~3k lines of macro vs the original 20K lines we had for sizes up to 50.

The version I have now works, but does require the 3K lines of macro to
effectively unwind the loops.

Its also slightly brittle because some slight alterations of the checks
no longer get detected by GCC as compile-time constants :(

I am not a huge fan of only testing on CI, since not every developer
will have things go through CI, so we end up with late reports.

I'm going to post the next version which uses the macros again, but
manages to limit things so that the calls are all done from within
<linux/packing.h> without driver intervention, and seem to work reliably
on my test systems.

> 
> 
> 
> --
> Best Regards
> Masahiro Yamada