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