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author | Ulf Samuelsson <ulf@emagii.com> | 2023-03-06 14:31:50 +0100 |
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committer | Nick Clifton <nickc@redhat.com> | 2023-03-07 13:53:10 +0000 |
commit | 3ec28966c3e4c63704212778f96c517cbf2e0090 (patch) | |
tree | b23a80962783727ee0a24fb4bdd22a54c28a486e /ld | |
parent | 099bf2927d446424e8585a60cf4ce63209999aa2 (diff) | |
download | gdb-3ec28966c3e4c63704212778f96c517cbf2e0090.zip gdb-3ec28966c3e4c63704212778f96c517cbf2e0090.tar.gz gdb-3ec28966c3e4c63704212778f96c517cbf2e0090.tar.bz2 |
DIGEST: Documentation
Signed-off-by: Ulf Samuelsson <ulf@emagii.com>
Diffstat (limited to 'ld')
-rw-r--r-- | ld/ld.texi | 498 |
1 files changed, 494 insertions, 4 deletions
@@ -5302,7 +5302,7 @@ __stop_SECNAME, where SECNAME is the name of the section. These indicate the start address and end address of the output section respectively. Note: most section names are not representable as C identifiers because they contain a @samp{.} character. - +@page @node Output Section Data @subsection Output Section Data @cindex data @@ -5353,10 +5353,28 @@ whereas this will work: @smallexample SECTIONS @{@ .text : @{@ *(.text) ; LONG(1) @}@ .data : @{@ *(.data) @}@ @}@ @end smallexample - +@page @cindex output section strings @kindex ASCII (@var{expression}) ``@var{string}'' @kindex ASCIZ ``@var{string}'' +@code{ASCII strings} +@sp 1 +@multitable @columnfractions .25 .20 .30 .20 .05 +@item +ASCIZ +@tab +@tab +"<string" +@tab +@item +ASCII +@tab +(<size>) +@tab +"<string" +@tab +@end multitable +@sp 1 You can include a zero-terminated string in an output section by using @code{ASCIZ}. The keyword is followed by a string which is stored at the current value of the location counter including adding a zero byte @@ -5381,18 +5399,490 @@ it must be enclosed in double quotes. The string can have C escape characters like '\n', '\r', '\t' and octal numbers. The '\"' escape is not supported. Nor are escaped hex values. - +@sp 2 Example 1: This is string of 16 characters and will create a 32 byte area: @smallexample ASCII (32) "This is 16 bytes" @end smallexample - +@sp 2 Example 2: This is a string of 16 characters and will create a 17 byte area: @smallexample ASCIZ "This is 16 bytes" @end smallexample +@page +@cindex output section strings +@kindex DIGEST "<label>[#<endian>]" "CRC64-ECMA" (@var{expr}, @var{expr}) +@kindex DIGEST "<label>[#<endian>]" "CRC64-ISO" (@var{expr}, @var{expr}) +@kindex DIGEST "<label>[#<endian>]" "CRC64-ISO-R" (@var{expr}, @var{expr}) +@kindex DIGEST "<label>[#<endian>]" "CRC64-WE" (@var{expr}, @var{expr}) +@kindex DIGEST "<label>[#<endian>]" "CRC64-XZ" (@var{expr}, @var{expr}) +@kindex DIGEST "<label>[#<endian>]" "CRC32" (@var{expr}, @var{expr}) +@kindex DIGEST "<label>[#<endian>]" POLY (@var{<parms>}) (@var{expr}, @var{expr}) + +@code{CRC Calculation} +@sp 1 +@multitable @columnfractions .20 .27 .28 .25 +@item +DIGEST +@tab +"<label>[#<endian>]" +@tab +"CRC32" +@tab +(start, end) +@item +DIGEST +@tab +"<label>[#<endian>]" +@tab +"CRC64-ECMA" +@tab +(start, end) +@item +DIGEST +@tab +"<label>[#<endian>]" +@tab +"CRC64-GO-ISO" +@tab +(start, end) +@item +DIGEST +@tab +"<label>[#<endian>]" +@tab +"CRC64-GO-ISO-R" +@tab +(start, end) +@item +DIGEST +@tab +"<label>[#<endian>]" +@tab +"CRC64-WE" +@tab +(start, end) +@item +DIGEST +@tab +"<label>[#<endian>]" +@tab +"CRC64-XZ" +@tab +(start, end) +@item +DIGEST +@tab +"<label>[#<endian>]" +@tab +POLY (<params>) +@tab +(start, end) +@item +DIGEST TABLE +@tab +"<label>[#<endian>]" +@tab +@tab +(start, end) +@end multitable + +You can calculate the CRC of a part of an output section through the +@code{DIGEST} command. The default section is the @code{".text"} section. +The commands take parameters for a label, a @code{polynome} and then two more, +specifying range of the checked area. The end address is the first address +past the checked area. + +The checksum is generated in little endian format, but this can be overridden by +adding a @code{#BE} or @code{#LE} modifier to the label string. +The generated label does not include the modifier. The endian can also be +specified on the command line using @code{-BE} or @code{-LE}. + +@sp 1 +There is one predefined 32-bit polynome + +@multitable @columnfractions .3 .4 .4 +@item +* @code{CRC32} +@tab +@code{0x04C11DB7} +@tab +@end multitable + +There are five predefined 64-bit polynomes + +@multitable @columnfractions .3 .4 .4 +@item +* @code{CRC64-ECMA} +@tab +@code{0x42F0E1EBA9EA3693} +@tab +@item +* @code{CRC64-ISO} +@tab +@code{0x000000000000001B} +@tab +@item +* @code{CRC64-ISO-R} +@tab +@code{0xD800000000000000} +@tab +@item +* @code{CRC64-WE} +@tab +@code{0x42F0E1EBA9EA3693} +@tab +@item +* @code{CRC64-XZ} +@tab +@code{0x42F0E1EBA9EA3693} +@tab +@end multitable +@sp 1 +You can also select your own @code{polynome} using the @code{DIGEST POLY}. + +It takes the following @code{parameters} separated by commas. + +@multitable @columnfractions .3 .7 +@item +@code{size} +@tab +size of CRC (32 or 64) +@item +@code{polynome} +@tab +@item +@code{initial} +@tab +initial value of crc before calculation +@item +@code{xor} +@tab +xor result before return +@item +@code{input reflect} +@tab +bitreverse input data +@item +@code{output reflect} +@tab +bitreverse result (before xor'ing) +@item +@code{reciprocal} +@tab +bitreverse polynome before generating table +@end multitable + +The parameters are explained in detail in + +@code{http://www.sunshine2k.de/articles/coding/crc/understanding_crc.html} + +Some of the predefined polynomes are the same, but differs in the other +parameters. +@page +The 32-bit <polynome> command defines the following global symbols. + +@multitable @columnfractions .3 .7 +@item +@code{___CRC32___} +@tab +address of the CRC32 checksum +@item +@code{___CRC32_START___} +@tab +first address in the checked area. +@item +@code{___CRC32_END___} +@tab +first address past the checked area. +@end multitable +@sp 2 +The 64-bit <polynome> command defines the following global symbols. + +@multitable @columnfractions .3 .7 +@item +@code{___CRC64___} +@tab +address of the CRC64 checksum +@item +@code{___CRC64_START___} +@tab +first address in the checked area. +@item +@code{___CRC64_END___} +@tab +first address past the checked area. +@end multitable +@sp 2 +Note: The generated CRC value must be stored outside the checked area. +@sp 2 +Example 1: This request a CRC check using the @code{ECMA} algorithm + +@smallexample + DIGEST "C64" "CRC64-ECMA" (START_CHECK,END_TEXT) +@end smallexample + +The user can retrieve the CRC value through the @code{C64} label. +@sp 2 +Example 2: This request a CRC check using the @code{ISO} algorithm + + The checksum is stored as big endian + +@smallexample + DIGEST "C64I#BE" "CRC64-ISO" (START_CHECK,END_TEXT) +@end smallexample + +The user can retrieve the big endian CRC value through the @code{C64I} label. +@sp 2 +Example 3: This request a CRC check using a user defined @code{polynome} + + The setup is the "CRC32" algorithm + +@smallexample + DIGEST "CRC" POLY (32, 0x04C11DB7,~0,~0,1,1,0) (START_CHECK,END_TEXT) +@end smallexample + +The user can retrieve the CRC value through the @code{CRC} label. +@sp 2 +Example 4: This request a CRC check using the @code{CRC32} polynome + +@smallexample + DIGEST "C32.SE" (START_CHECK,END_TEXT) +@end smallexample + +The user can retrieve the CRC value through the @code{C32} label. + +@page +@cindex output section strings +@kindex DIGEST TABLE "<label>[#<endian>]" +@page +The @code{DIGEST TABLE} command creates a 1 or 2 kByte table for a table-driven +CRC calculation. This speeds up the CRC calculation over a non-table-driver +version since you can handle 8 bits at a time, instead of 1 bit. + +The table generated is for the @code{polynome} selected using a +@code{DIGEST <polynome>} command. + +The command will define the label supplied as a parameter. +The table will be in small endian, unless the @code{.BE} or @code{.LE} extension +is given to the label. +It also defines a symbol based on the size of the polynome. + +@enumerate +@item +@code{___CRC32_TABLE___} address of the CRC32 table, or +@item +@code{___CRC64_TABLE___} address of the CRC64 table +@end enumerate + +@sp 2 +Example 1: Generate a 1 kB table + +(assuming a previous @code{DIGEST "CRC32"} command) + +@smallexample + DIGEST TABLE "crc_tab32" +@end smallexample + +The user must declare @code{extern uint32_t *crc_tab32;} in his code. +@sp 2 +Example 2: Generate a 2 kB table in big endian format. + +(assuming a previous @code{DIGEST "CRC64-###"} command) + +@smallexample + DIGEST TABLE "crc_tab64.be" +@end smallexample + +The user must declare @code{extern uint64_t *crc_tab64;} in his code. + +Using the tables: + The user must include CRC code in the application to test the CRC +@sp 2 + +@multitable @columnfractions .15 .85 +@item +Example 1: +@tab +Calculating CRC-64 +@end multitable +@sp 1 +@multitable @columnfractions .05 .95 +@item +@tab +Copyright (c) 2016 Lammert Bies +@item +@tab +Copyright (c) 2021 Bastian Molkenthin +@item +@tab +Copyright (c) 2023 Ulf Samuelsson +@end multitable +@sp 2 +@smallexample +#define SHIFT(t) ((sizeof(t)-1)*8) +uint64_t calc_crc64 + (algorithm_desc_t * dsc, const unsigned char *input_str, size_t num_bytes) +@{ + uint64_t crc; + const unsigned char *ptr; + uint64_t *crc_tab = dsc->crc_tab; + uint64_t index; + + if ((ptr = input_str) == NULL) + return 0; + + if (crc_tab == NULL) + return 0; + + + crc = dsc->initial; + if (dsc->reciprocal) + @{ + for (uint32_t i = 0; i < num_bytes; i++) + @{ + index = ((crc >> 0) ^ (uint64_t) * ptr++) & 0x00000000000000FFull; + crc = (crc >> 8) ^ crc_tab[index]; + @} + @} + else + @{ + uint32_t shift = SHIFT (uint64_t); + for (uint32_t i = 0; i < num_bytes; i++) + @{ + const unsigned char c = *ptr++; + uint64_t rc = (uint64_t) (dsc->ireflect ? reflect8 (c) : c); + crc = (crc ^ (rc << shift)); + index = (uint32_t) (crc >> shift); + crc = (crc << 8); + crc = (crc ^ (crc_tab[index])); + @} + @} + crc = (dsc->oreflect ? reflect64 (crc) : crc); + crc = crc ^ dsc->xor_val; + return crc; +@} /* calc_crc64 */ +@end smallexample +@page +@multitable @columnfractions .15 .85 +@item +Example 2: +@tab +Calculating CRC-32 +@end multitable +@sp 1 +@multitable @columnfractions .05 .95 +@item +@tab +Copyright (c) 2016 Lammert Bies +@item +@tab +Copyright (c) 2021 Bastian Molkenthin +@item +@tab +Copyright (c) 2023 Ulf Samuelsson +@end multitable +@sp 2 +@smallexample +#define SHIFT(t) ((sizeof(t)-1)*8) +uint32_t +calc_crc32 (algorithm_desc_t * dsc, const unsigned char *input_str, + size_t num_bytes) +@{ + uint32_t crc; + const unsigned char *ptr; + uint32_t index; + uint32_t *crc_tab = dsc->crc_tab; + + if ((ptr = input_str) == NULL) + return 0; + + if (crc_tab == NULL) + return 0; + + crc = dsc->initial; + + if (dsc->reciprocal) + @{ + for (uint32_t i = 0; i < num_bytes; i++) + @{ + index = ((crc >> 0) ^ (uint32_t) * ptr++) & 0x000000FFul; + crc = (crc >> 8) ^ crc_tab[index]; + @} + @} + else + @{ + uint32_t shift = SHIFT (uint32_t); + for (uint32_t i = 0; i < num_bytes; i++) + @{ + const unsigned char c = *ptr++; + uint32_t rc = (uint32_t) (dsc->ireflect ? reflect8 (c) : c); + crc = (crc ^ (rc << shift)); + index = (uint32_t) (crc >> shift); + crc = (crc << 8); + crc = (crc ^ (crc_tab[index])); + @} + @} + crc = (dsc->oreflect ? reflect32 (crc) : crc); + crc = crc ^ dsc->xor_val; + return crc; +@} /* calc_crc32 */ +@end smallexample +@page +@multitable @columnfractions .15 .85 +@item +Example 3: +@tab +Calculating CRC-32 using optimized routine +@end multitable +@sp 1 +@multitable @columnfractions .05 .95 +@item +@tab +Copyright (c) 2016 Lammert Bies +@item +@tab +Copyright (c) 2021 Bastian Molkenthin +@item +@tab +Copyright (c) 2023 Ulf Samuelsson +@end multitable +@sp 2 +@smallexample +#define SHIFT(t) ((sizeof(t)-1)*8) +extern uint32_t *crc_tab; + +uint32_t +calc_crc32 (const unsigned char *input_str, size_t num_bytes) +@{ + uint32_t crc; + const unsigned char *ptr; + uint32_t index; + uint32_t shift = SHIFT (uint32_t); + + if ((ptr = input_str) == NULL) + return 0; + + crc = 0xFFFFFFFF; + for (uint32_t i = 0; i < num_bytes; i++) + @{ + const unsigned char c = *ptr++; + crc = (crc ^ (c << shift)); + index = (uint32_t) (crc >> shift); + crc = (crc << 8); + crc = (crc ^ (crc_tab[index])); + @} + return crc ^ 0xFFFFFFFF; +@} /* calc_crc32 */ +@end smallexample +@page +@cindex output section strings +@kindex TIMESTAMP + +The @code{TIMESTAMP} command creates 64-bit integer with the number of seconds +since Epoch (1970-01-01 00:00). @kindex FILL(@var{expression}) @cindex holes, filling |