diff options
Diffstat (limited to 'binutils-2.24/bfd/doc/mmo.texi')
| -rw-r--r-- | binutils-2.24/bfd/doc/mmo.texi | 365 |
1 files changed, 0 insertions, 365 deletions
diff --git a/binutils-2.24/bfd/doc/mmo.texi b/binutils-2.24/bfd/doc/mmo.texi deleted file mode 100644 index b0d726aa..00000000 --- a/binutils-2.24/bfd/doc/mmo.texi +++ /dev/null @@ -1,365 +0,0 @@ -@section mmo backend -The mmo object format is used exclusively together with Professor -Donald E.@: Knuth's educational 64-bit processor MMIX. The simulator -@command{mmix} which is available at -@url{http://www-cs-faculty.stanford.edu/~knuth/programs/mmix.tar.gz} -understands this format. That package also includes a combined -assembler and linker called @command{mmixal}. The mmo format has -no advantages feature-wise compared to e.g. ELF. It is a simple -non-relocatable object format with no support for archives or -debugging information, except for symbol value information and -line numbers (which is not yet implemented in BFD). See -@url{http://www-cs-faculty.stanford.edu/~knuth/mmix.html} for more -information about MMIX. The ELF format is used for intermediate -object files in the BFD implementation. - -@c We want to xref the symbol table node. A feature in "chew" -@c requires that "commands" do not contain spaces in the -@c arguments. Hence the hyphen in "Symbol-table". -@menu -* File layout:: -* Symbol-table:: -* mmo section mapping:: -@end menu - -@node File layout, Symbol-table, mmo, mmo -@subsection File layout -The mmo file contents is not partitioned into named sections as -with e.g.@: ELF. Memory areas is formed by specifying the -location of the data that follows. Only the memory area -@samp{0x0000@dots{}00} to @samp{0x01ff@dots{}ff} is executable, so -it is used for code (and constants) and the area -@samp{0x2000@dots{}00} to @samp{0x20ff@dots{}ff} is used for -writable data. @xref{mmo section mapping}. - -There is provision for specifying ``special data'' of 65536 -different types. We use type 80 (decimal), arbitrarily chosen the -same as the ELF @code{e_machine} number for MMIX, filling it with -section information normally found in ELF objects. @xref{mmo -section mapping}. - -Contents is entered as 32-bit words, xor:ed over previous -contents, always zero-initialized. A word that starts with the -byte @samp{0x98} forms a command called a @samp{lopcode}, where -the next byte distinguished between the thirteen lopcodes. The -two remaining bytes, called the @samp{Y} and @samp{Z} fields, or -the @samp{YZ} field (a 16-bit big-endian number), are used for -various purposes different for each lopcode. As documented in -@url{http://www-cs-faculty.stanford.edu/~knuth/mmixal-intro.ps.gz}, -the lopcodes are: - -@table @code -@item lop_quote -0x98000001. The next word is contents, regardless of whether it -starts with 0x98 or not. - -@item lop_loc -0x9801YYZZ, where @samp{Z} is 1 or 2. This is a location -directive, setting the location for the next data to the next -32-bit word (for @math{Z = 1}) or 64-bit word (for @math{Z = 2}), -plus @math{Y * 2^56}. Normally @samp{Y} is 0 for the text segment -and 2 for the data segment. - -@item lop_skip -0x9802YYZZ. Increase the current location by @samp{YZ} bytes. - -@item lop_fixo -0x9803YYZZ, where @samp{Z} is 1 or 2. Store the current location -as 64 bits into the location pointed to by the next 32-bit -(@math{Z = 1}) or 64-bit (@math{Z = 2}) word, plus @math{Y * -2^56}. - -@item lop_fixr -0x9804YYZZ. @samp{YZ} is stored into the current location plus -@math{2 - 4 * YZ}. - -@item lop_fixrx -0x980500ZZ. @samp{Z} is 16 or 24. A value @samp{L} derived from -the following 32-bit word are used in a manner similar to -@samp{YZ} in lop_fixr: it is xor:ed into the current location -minus @math{4 * L}. The first byte of the word is 0 or 1. If it -is 1, then @math{L = (@var{lowest 24 bits of word}) - 2^Z}, if 0, -then @math{L = (@var{lowest 24 bits of word})}. - -@item lop_file -0x9806YYZZ. @samp{Y} is the file number, @samp{Z} is count of -32-bit words. Set the file number to @samp{Y} and the line -counter to 0. The next @math{Z * 4} bytes contain the file name, -padded with zeros if the count is not a multiple of four. The -same @samp{Y} may occur multiple times, but @samp{Z} must be 0 for -all but the first occurrence. - -@item lop_line -0x9807YYZZ. @samp{YZ} is the line number. Together with -lop_file, it forms the source location for the next 32-bit word. -Note that for each non-lopcode 32-bit word, line numbers are -assumed incremented by one. - -@item lop_spec -0x9808YYZZ. @samp{YZ} is the type number. Data until the next -lopcode other than lop_quote forms special data of type @samp{YZ}. -@xref{mmo section mapping}. - -Other types than 80, (or type 80 with a content that does not -parse) is stored in sections named @code{.MMIX.spec_data.@var{n}} -where @var{n} is the @samp{YZ}-type. The flags for such a -sections say not to allocate or load the data. The vma is 0. -Contents of multiple occurrences of special data @var{n} is -concatenated to the data of the previous lop_spec @var{n}s. The -location in data or code at which the lop_spec occurred is lost. - -@item lop_pre -0x980901ZZ. The first lopcode in a file. The @samp{Z} field forms the -length of header information in 32-bit words, where the first word -tells the time in seconds since @samp{00:00:00 GMT Jan 1 1970}. - -@item lop_post -0x980a00ZZ. @math{Z > 32}. This lopcode follows after all -content-generating lopcodes in a program. The @samp{Z} field -denotes the value of @samp{rG} at the beginning of the program. -The following @math{256 - Z} big-endian 64-bit words are loaded -into global registers @samp{$G} @dots{} @samp{$255}. - -@item lop_stab -0x980b0000. The next-to-last lopcode in a program. Must follow -immediately after the lop_post lopcode and its data. After this -lopcode follows all symbols in a compressed format -(@pxref{Symbol-table}). - -@item lop_end -0x980cYYZZ. The last lopcode in a program. It must follow the -lop_stab lopcode and its data. The @samp{YZ} field contains the -number of 32-bit words of symbol table information after the -preceding lop_stab lopcode. -@end table - -Note that the lopcode "fixups"; @code{lop_fixr}, @code{lop_fixrx} and -@code{lop_fixo} are not generated by BFD, but are handled. They are -generated by @code{mmixal}. - -This trivial one-label, one-instruction file: - -@example - :Main TRAP 1,2,3 -@end example - -can be represented this way in mmo: - -@example - 0x98090101 - lop_pre, one 32-bit word with timestamp. - <timestamp> - 0x98010002 - lop_loc, text segment, using a 64-bit address. - Note that mmixal does not emit this for the file above. - 0x00000000 - Address, high 32 bits. - 0x00000000 - Address, low 32 bits. - 0x98060002 - lop_file, 2 32-bit words for file-name. - 0x74657374 - "test" - 0x2e730000 - ".s\0\0" - 0x98070001 - lop_line, line 1. - 0x00010203 - TRAP 1,2,3 - 0x980a00ff - lop_post, setting $255 to 0. - 0x00000000 - 0x00000000 - 0x980b0000 - lop_stab for ":Main" = 0, serial 1. - 0x203a4040 @xref{Symbol-table}. - 0x10404020 - 0x4d206120 - 0x69016e00 - 0x81000000 - 0x980c0005 - lop_end; symbol table contained five 32-bit words. -@end example -@node Symbol-table, mmo section mapping, File layout, mmo -@subsection Symbol table format -From mmixal.w (or really, the generated mmixal.tex) in -@url{http://www-cs-faculty.stanford.edu/~knuth/programs/mmix.tar.gz}): -``Symbols are stored and retrieved by means of a @samp{ternary -search trie}, following ideas of Bentley and Sedgewick. (See -ACM--SIAM Symp.@: on Discrete Algorithms @samp{8} (1997), 360--369; -R.@:Sedgewick, @samp{Algorithms in C} (Reading, Mass.@: -Addison--Wesley, 1998), @samp{15.4}.) Each trie node stores a -character, and there are branches to subtries for the cases where -a given character is less than, equal to, or greater than the -character in the trie. There also is a pointer to a symbol table -entry if a symbol ends at the current node.'' - -So it's a tree encoded as a stream of bytes. The stream of bytes -acts on a single virtual global symbol, adding and removing -characters and signalling complete symbol points. Here, we read -the stream and create symbols at the completion points. - -First, there's a control byte @code{m}. If any of the listed bits -in @code{m} is nonzero, we execute what stands at the right, in -the listed order: - -@example - (MMO3_LEFT) - 0x40 - Traverse left trie. - (Read a new command byte and recurse.) - - (MMO3_SYMBITS) - 0x2f - Read the next byte as a character and store it in the - current character position; increment character position. - Test the bits of @code{m}: - - (MMO3_WCHAR) - 0x80 - The character is 16-bit (so read another byte, - merge into current character. - - (MMO3_TYPEBITS) - 0xf - We have a complete symbol; parse the type, value - and serial number and do what should be done - with a symbol. The type and length information - is in j = (m & 0xf). - - (MMO3_REGQUAL_BITS) - j == 0xf: A register variable. The following - byte tells which register. - j <= 8: An absolute symbol. Read j bytes as the - big-endian number the symbol equals. - A j = 2 with two zero bytes denotes an - unknown symbol. - j > 8: As with j <= 8, but add (0x20 << 56) - to the value in the following j - 8 - bytes. - - Then comes the serial number, as a variant of - uleb128, but better named ubeb128: - Read bytes and shift the previous value left 7 - (multiply by 128). Add in the new byte, repeat - until a byte has bit 7 set. The serial number - is the computed value minus 128. - - (MMO3_MIDDLE) - 0x20 - Traverse middle trie. (Read a new command byte - and recurse.) Decrement character position. - - (MMO3_RIGHT) - 0x10 - Traverse right trie. (Read a new command byte and - recurse.) -@end example - -Let's look again at the @code{lop_stab} for the trivial file -(@pxref{File layout}). - -@example - 0x980b0000 - lop_stab for ":Main" = 0, serial 1. - 0x203a4040 - 0x10404020 - 0x4d206120 - 0x69016e00 - 0x81000000 -@end example - -This forms the trivial trie (note that the path between ``:'' and -``M'' is redundant): - -@example - 203a ":" - 40 / - 40 / - 10 \ - 40 / - 40 / - 204d "M" - 2061 "a" - 2069 "i" - 016e "n" is the last character in a full symbol, and - with a value represented in one byte. - 00 The value is 0. - 81 The serial number is 1. -@end example - -@node mmo section mapping, , Symbol-table, mmo -@subsection mmo section mapping -The implementation in BFD uses special data type 80 (decimal) to -encapsulate and describe named sections, containing e.g.@: debug -information. If needed, any datum in the encapsulation will be -quoted using lop_quote. First comes a 32-bit word holding the -number of 32-bit words containing the zero-terminated zero-padded -segment name. After the name there's a 32-bit word holding flags -describing the section type. Then comes a 64-bit big-endian word -with the section length (in bytes), then another with the section -start address. Depending on the type of section, the contents -might follow, zero-padded to 32-bit boundary. For a loadable -section (such as data or code), the contents might follow at some -later point, not necessarily immediately, as a lop_loc with the -same start address as in the section description, followed by the -contents. This in effect forms a descriptor that must be emitted -before the actual contents. Sections described this way must not -overlap. - -For areas that don't have such descriptors, synthetic sections are -formed by BFD. Consecutive contents in the two memory areas -@samp{0x0000@dots{}00} to @samp{0x01ff@dots{}ff} and -@samp{0x2000@dots{}00} to @samp{0x20ff@dots{}ff} are entered in -sections named @code{.text} and @code{.data} respectively. If an area -is not otherwise described, but would together with a neighboring -lower area be less than @samp{0x40000000} bytes long, it is joined -with the lower area and the gap is zero-filled. For other cases, -a new section is formed, named @code{.MMIX.sec.@var{n}}. Here, -@var{n} is a number, a running count through the mmo file, -starting at 0. - -A loadable section specified as: - -@example - .section secname,"ax" - TETRA 1,2,3,4,-1,-2009 - BYTE 80 -@end example - -and linked to address @samp{0x4}, is represented by the sequence: - -@example - 0x98080050 - lop_spec 80 - 0x00000002 - two 32-bit words for the section name - 0x7365636e - "secn" - 0x616d6500 - "ame\0" - 0x00000033 - flags CODE, READONLY, LOAD, ALLOC - 0x00000000 - high 32 bits of section length - 0x0000001c - section length is 28 bytes; 6 * 4 + 1 + alignment to 32 bits - 0x00000000 - high 32 bits of section address - 0x00000004 - section address is 4 - 0x98010002 - 64 bits with address of following data - 0x00000000 - high 32 bits of address - 0x00000004 - low 32 bits: data starts at address 4 - 0x00000001 - 1 - 0x00000002 - 2 - 0x00000003 - 3 - 0x00000004 - 4 - 0xffffffff - -1 - 0xfffff827 - -2009 - 0x50000000 - 80 as a byte, padded with zeros. -@end example - -Note that the lop_spec wrapping does not include the section -contents. Compare this to a non-loaded section specified as: - -@example - .section thirdsec - TETRA 200001,100002 - BYTE 38,40 -@end example - -This, when linked to address @samp{0x200000000000001c}, is -represented by: - -@example - 0x98080050 - lop_spec 80 - 0x00000002 - two 32-bit words for the section name - 0x7365636e - "thir" - 0x616d6500 - "dsec" - 0x00000010 - flag READONLY - 0x00000000 - high 32 bits of section length - 0x0000000c - section length is 12 bytes; 2 * 4 + 2 + alignment to 32 bits - 0x20000000 - high 32 bits of address - 0x0000001c - low 32 bits of address 0x200000000000001c - 0x00030d41 - 200001 - 0x000186a2 - 100002 - 0x26280000 - 38, 40 as bytes, padded with zeros -@end example - -For the latter example, the section contents must not be -loaded in memory, and is therefore specified as part of the -special data. The address is usually unimportant but might -provide information for e.g.@: the DWARF 2 debugging format. |