diff options
Diffstat (limited to 'lib/packing.c')
-rw-r--r-- | lib/packing.c | 507 |
1 files changed, 392 insertions, 115 deletions
diff --git a/lib/packing.c b/lib/packing.c index 3f656167c17e..bb1643d9e64d 100644 --- a/lib/packing.c +++ b/lib/packing.c @@ -5,56 +5,163 @@ #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> -static int get_le_offset(int offset) -{ - int closest_multiple_of_4; +#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); \ + } \ + }) - closest_multiple_of_4 = (offset / 4) * 4; - offset -= closest_multiple_of_4; - return closest_multiple_of_4 + (3 - offset); -} +#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); \ + } \ + }) -static int get_reverse_lsw32_offset(int offset, size_t len) +/** + * 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) { - int closest_multiple_of_4; - int word_index; - - word_index = offset / 4; - closest_multiple_of_4 = word_index * 4; - offset -= closest_multiple_of_4; - word_index = (len / 4) - word_index - 1; - return word_index * 4 + offset; + 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 adjust_for_msb_right_quirk(u64 *to_write, int *box_start_bit, - int *box_end_bit, u8 *box_mask) +static void __pack(void *pbuf, u64 uval, size_t startbit, size_t endbit, + size_t pbuflen, u8 quirks) { - int box_bit_width = *box_start_bit - *box_end_bit + 1; - int new_box_start_bit, new_box_end_bit; - - *to_write >>= *box_end_bit; - *to_write = bitrev8(*to_write) >> (8 - box_bit_width); - *to_write <<= *box_end_bit; - - new_box_end_bit = box_bit_width - *box_start_bit - 1; - new_box_start_bit = box_bit_width - *box_end_bit - 1; - *box_mask = GENMASK_ULL(new_box_start_bit, new_box_end_bit); - *box_start_bit = new_box_start_bit; - *box_end_bit = new_box_end_bit; + /* 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; + } } /** - * 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. + * 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. @@ -62,79 +169,68 @@ static void adjust_for_msb_right_quirk(u64 *to_write, int *box_start_bit, * 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. * * 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. + * correct usage, return code may be discarded. The @pbuf memory will + * be modified on success. */ -int packing(void *pbuf, u64 *uval, int startbit, int endbit, size_t pbuflen, - enum packing_op op, u8 quirks) +int pack(void *pbuf, u64 uval, size_t startbit, size_t endbit, size_t pbuflen, + u8 quirks) { - /* Number of bits for storing "uval" - * also width of the field to access in the pbuf + /* startbit is expected to be larger than endbit, and both are + * expected to be within the logically addressable range of the buffer. */ - u64 value_width; - /* Logical byte indices corresponding to the - * start and end of the field. - */ - int plogical_first_u8, plogical_last_u8, box; - - /* startbit is expected to be larger than endbit */ - if (startbit < endbit) + if (unlikely(startbit < endbit || startbit >= BITS_PER_BYTE * pbuflen)) /* Invalid function call */ return -EINVAL; - value_width = startbit - endbit + 1; - if (value_width > 64) + if (unlikely(startbit - endbit >= 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. + __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. */ - if (op == PACK && 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; /* Initialize parameter */ - if (op == UNPACK) - *uval = 0; + *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. */ - plogical_first_u8 = startbit / 8; - plogical_last_u8 = endbit / 8; - for (box = plogical_first_u8; box >= plogical_last_u8; box--) { /* Bit indices into the currently accessed 8-bit box */ - int box_start_bit, box_end_bit, box_addr; + size_t box_start_bit, box_end_bit, box_addr; u8 box_mask; /* Corresponding bits from the unpacked u64 parameter */ - int proj_start_bit, proj_end_bit; + 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 % 8; + box_start_bit = startbit % BITS_PER_BYTE; else box_start_bit = 7; if (box == plogical_last_u8) - box_end_bit = endbit % 8; + box_end_bit = endbit % BITS_PER_BYTE; else box_end_bit = 0; @@ -145,57 +241,238 @@ int packing(void *pbuf, u64 *uval, int startbit, int endbit, size_t pbuflen, * box is u8, the projection is u64 because it may fall * anywhere within the unpacked u64. */ - proj_start_bit = ((box * 8) + box_start_bit) - endbit; - proj_end_bit = ((box * 8) + box_end_bit) - endbit; + 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_ULL(box_start_bit, box_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 = pbuflen - box - 1; - if (quirks & QUIRK_LITTLE_ENDIAN) - box_addr = get_le_offset(box_addr); - if (quirks & QUIRK_LSW32_IS_FIRST) - box_addr = get_reverse_lsw32_offset(box_addr, - pbuflen); - - if (op == UNPACK) { - u64 pval; - - /* Read from pbuf, write to uval */ - pval = ((u8 *)pbuf)[box_addr] & box_mask; - if (quirks & QUIRK_MSB_ON_THE_RIGHT) - adjust_for_msb_right_quirk(&pval, - &box_start_bit, - &box_end_bit, - &box_mask); - - pval >>= box_end_bit; - pval <<= proj_end_bit; - *uval &= ~proj_mask; - *uval |= pval; - } else { - u64 pval; - - /* Write to pbuf, read from uval */ - pval = (*uval) & proj_mask; - pval >>= proj_end_bit; - if (quirks & QUIRK_MSB_ON_THE_RIGHT) - adjust_for_msb_right_quirk(&pval, - &box_start_bit, - &box_end_bit, - &box_mask); - - pval <<= box_end_bit; - ((u8 *)pbuf)[box_addr] &= ~box_mask; - ((u8 *)pbuf)[box_addr] |= pval; - } + 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"); |