430 lines
23 KiB
Plaintext
430 lines
23 KiB
Plaintext
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flat assembler
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Symbolic information file format
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Table 1 Header
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/-------------------------------------------------------------------------\
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| Offset | Size | Description |
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|========|=========|======================================================|
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| +0 | dword | Signature 1A736166h (little-endian). |
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|--------|---------|------------------------------------------------------|
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| +4 | byte | Major version of flat assembler. |
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|--------|---------|------------------------------------------------------|
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| +5 | byte | Minor version of flat assembler. |
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|--------|---------|------------------------------------------------------|
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| +6 | word | Length of header. |
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|--------|---------|------------------------------------------------------|
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| +8 | dword | Offset of input file name in the strings table. |
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|--------|---------|------------------------------------------------------|
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| +12 | dword | Offset of output file name in the strings table. |
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|--------|---------|------------------------------------------------------|
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| +16 | dword | Offset of strings table. |
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|--------|---------|------------------------------------------------------|
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| +20 | dword | Length of strings table. |
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|--------|---------|------------------------------------------------------|
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| +24 | dword | Offset of symbols table. |
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|--------|---------|------------------------------------------------------|
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| +28 | dword | Length of symbols table. |
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|--------|---------|------------------------------------------------------|
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| +32 | dword | Offset of preprocessed source. |
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|--------|---------|------------------------------------------------------|
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| +36 | dword | Length of preprocessed source. |
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|--------|---------|------------------------------------------------------|
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| +40 | dword | Offset of assembly dump. |
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|--------|---------|------------------------------------------------------|
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| +44 | dword | Length of assembly dump. |
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|--------|---------|------------------------------------------------------|
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| +48 | dword | Offset of section names table. |
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|--------|---------|------------------------------------------------------|
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| +52 | dword | Length of section names table. |
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|--------|---------|------------------------------------------------------|
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| +56 | dword | Offset of symbol references dump. |
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|--------|---------|------------------------------------------------------|
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| +60 | dword | Length of symbol references dump. |
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\-------------------------------------------------------------------------/
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Notes:
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If header is shorter than 64 bytes, it comes from a version that does not
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support dumping some of the structures. It should then be interpreted
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that the data for missing structures could not be provided, not that the
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size of that data is zero.
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Offsets given in header generally mean positions in the file, however
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input and output file names are specified by offsets in the strings table,
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so you have to add their offset to the offset of strings table to obtain
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the positions of those strings in the file.
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The strings table contains just a sequence of ASCIIZ strings, which may
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be referred to by other parts of the file. It contains the names of
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main input file, the output file, and the names of the sections and
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external symbols if there were any.
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The symbols table is an array of 32-byte structures, each one in format
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specified by table 2.
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The preprocessed source is a sequence of preprocessed lines, each one
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in format as defined in table 3.
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The assembly dump contains an array of 28-byte structures, each one in
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format specified by table 4, and at the end of this array an additional
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double word containing the offset in output file at which the assembly
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was ended.
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It is possible that file does not contain assembly dump at all - this
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happens when some error occured and only the preprocessed source was
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dumped. If error occured during the preprocessing, only the source up to
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the point of error is provided. In such case (and only then) the field
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at offset 44 contains zero.
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The section names table exists only when the output format was an object
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file (ELF or COFF), and it is an array of 4-byte entries, each being an
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offset of the name of the section in the strings table.
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The index of section in this table is the same, as the index of section
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in the generated object file.
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The symbol references dump contains an array of 8-byte structures, each
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one describes an event of some symbol being used. The first double word
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of such structure contains an offset of symbol in the symbols table,
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and the second double word is an offset of structure in assembly dump,
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which specifies at what moment the symbol was referenced.
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Table 2 Symbol structure
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/-------------------------------------------------------------------------\
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| Offset | Size | Description |
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|========|=======|========================================================|
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| +0 | qword | Value of symbol. |
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|--------|-------|--------------------------------------------------------|
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| +8 | word | Flags (table 2.1). |
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|--------|-------|--------------------------------------------------------|
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| +10 | byte | Size of data labelled by this symbol (zero means plain |
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| | | label without size attached). |
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|--------|-------|--------------------------------------------------------|
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| +11 | byte | Type of value (table 2.2). Any value other than zero |
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| | | means some kind of relocatable symbol. |
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|--------|-------|--------------------------------------------------------|
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| +12 | dword | Extended SIB, the first two bytes are register codes |
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| | | and the second two bytes are corresponding scales. |
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|--------|-------|--------------------------------------------------------|
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| +16 | word | Number of pass in which symbol was defined last time. |
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|--------|-------|--------------------------------------------------------|
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| +18 | word | Number of pass in which symbol was used last time. |
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|--------|-------|--------------------------------------------------------|
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| +20 | dword | If the symbol is relocatable, this field contains |
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| | | information about section or external symbol, to which |
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| | | it is relative - otherwise this field has no meaning. |
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| | | When the highest bit is cleared, the symbol is |
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| | | relative to a section, and the bits 0-30 contain |
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| | | the index (starting from 1) in the table of sections. |
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| | | When the highest bit is set, the symbol is relative to |
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| | | an external symbol, and the bits 0-30 contain the |
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| | | the offset of the name of this symbol in the strings |
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| | | table. |
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|--------|-------|--------------------------------------------------------|
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| +24 | dword | If the highest bit is cleared, the bits 0-30 contain |
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| | | the offset of symbol name in the preprocessed source. |
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| | | This name is a pascal-style string (byte length |
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| | | followed by string data). |
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| | | Zero in this field means an anonymous symbol. |
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| | | If the highest bit is set, the bits 0-30 contain the |
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| | | offset of the symbol name in the strings table, and |
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| | | this name is a zero-ended string in this case (as are |
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| | | all the strings there). |
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|--------|-------|--------------------------------------------------------|
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| +28 | dword | Offset in the preprocessed source of line that defined |
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| | | this symbol (see table 3). |
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\-------------------------------------------------------------------------/
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Table 2.1 Symbol flags
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/-----------------------------------------------------------------\
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| Bit | Value | Description |
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|=====|=======|===================================================|
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| 0 | 1 | Symbol was defined. |
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|-----|-------|---------------------------------------------------|
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| 1 | 2 | Symbol is an assembly-time variable. |
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|-----|-------|---------------------------------------------------|
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| 2 | 4 | Symbol cannot be forward-referenced. |
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|-----|-------|---------------------------------------------------|
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| 3 | 8 | Symbol was used. |
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|-----|-------|---------------------------------------------------|
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| 4 | 10h | The prediction was needed when checking |
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| | | whether the symbol was used. |
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|-----|-------|---------------------------------------------------|
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| 5 | 20h | Result of last predicted check for being used. |
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|-----|-------|---------------------------------------------------|
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| 6 | 40h | The prediction was needed when checking |
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| | | whether the symbol was defined. |
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|-----|-------|---------------------------------------------------|
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| 7 | 80h | Result of last predicted check for being defined. |
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|-----|-------|---------------------------------------------------|
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| 8 | 100h | The optimization adjustment is applied to |
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| | | the value of this symbol. |
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|-----|-------|---------------------------------------------------|
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| 9 | 200h | The value of symbol is negative number encoded |
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| | | as two's complement. |
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|-----|-------|---------------------------------------------------|
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| 10 | 400h | Symbol is a special marker and has no value. |
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\-----------------------------------------------------------------/
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Notes:
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Some of those flags are listed here just for completness, as they
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have little use outside of the flat assembler. However the bit 0
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is important, because the symbols table contains all the labels
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that occured in source, even if some of them were in the
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conditional blocks that did not get assembled.
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Table 2.2 Symbol value types
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/-------------------------------------------------------------------\
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| Value | Description |
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|=======|===========================================================|
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| 0 | Absolute value. |
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|-------|-----------------------------------------------------------|
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| 1 | Relocatable segment address (only with MZ output). |
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|-------|-----------------------------------------------------------|
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| 2 | Relocatable 32-bit address. |
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|-------|-----------------------------------------------------------|
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| 3 | Relocatable relative 32-bit address (value valid only for |
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| | symbol used in the same place where it was calculated, |
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| | it should not occur in the symbol structure). |
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|-------|-----------------------------------------------------------|
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| 4 | Relocatable 64-bit address. |
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|-------|-----------------------------------------------------------|
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| 5 | [ELF only] GOT-relative 32-bit address. |
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|-------|-----------------------------------------------------------|
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| 6 | [ELF only] 32-bit address of PLT entry. |
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|-------|-----------------------------------------------------------|
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| 7 | [ELF only] Relative 32-bit address of PLT entry (value |
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| | valid only for symbol used in the same place where it |
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| | was calculated, it should not occur in the symbol |
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| | structure). |
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\-------------------------------------------------------------------/
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Notes:
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The types 3 and 7 should never be encountered in the symbols dump,
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they are only used internally by the flat assembler.
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If type value is a negative number, it is an opposite of a value
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from this table and it means that the symbol of a given type has
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been negated.
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Table 2.3 Register codes for extended SIB
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/------------------\
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| Value | Register |
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|=======|==========|
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| 23h | BX |
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|-------|----------|
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| 25h | BP |
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|-------|----------|
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| 26h | SI |
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|-------|----------|
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| 27h | DI |
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|-------|----------|
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| 40h | EAX |
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|-------|----------|
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| 41h | ECX |
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|-------|----------|
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| 42h | EDX |
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|-------|----------|
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| 43h | EBX |
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|-------|----------|
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| 44h | ESP |
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|-------|----------|
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| 45h | EBP |
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|-------|----------|
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| 46h | ESI |
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|-------|----------|
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| 47h | EDI |
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|-------|----------|
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| 48h | R8D |
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|-------|----------|
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| 49h | R9D |
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|-------|----------|
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| 4Ah | R10D |
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|-------|----------|
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| 4Bh | R11D |
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|-------|----------|
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| 4Ch | R12D |
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|-------|----------|
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| 4Dh | R13D |
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|-------|----------|
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| 4Eh | R14D |
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|-------|----------|
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| 4Fh | R15D |
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|-------|----------|
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| 80h | RAX |
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|-------|----------|
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| 81h | RCX |
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|-------|----------|
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| 82h | RDX |
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|-------|----------|
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| 83h | RBX |
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|-------|----------|
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| 84h | RSP |
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|-------|----------|
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| 85h | RBP |
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|-------|----------|
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| 86h | RSI |
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|-------|----------|
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| 87h | RDI |
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|-------|----------|
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| 88h | R8 |
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|-------|----------|
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| 89h | R9 |
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|-------|----------|
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| 8Ah | R10 |
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|-------|----------|
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| 8Bh | R11 |
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|-------|----------|
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| 8Ch | R12 |
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|-------|----------|
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| 8Dh | R13 |
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|-------|----------|
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| 8Eh | R14 |
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|-------|----------|
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| 8Fh | R15 |
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|-------|----------|
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| 94h | EIP |
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|-------|----------|
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| 98h | RIP |
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\------------------/
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Table 3 Preprocessed line
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/--------------------------------------------------------------------------\
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| Offset | Size | Value |
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|========|=================================================================|
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| +0 | dword | When the line was loaded from source, this field |
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| | | contains either zero (if it is the line from the main |
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| | | input file), or an offset inside the preprocessed |
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| | | source to the name of file, from which this line was |
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| | | loaded (the name of file is zero-ended string). |
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| | | When the line was generated by macroinstruction, this |
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| | | field contains offset inside the preprocessed source to |
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| | | the pascal-style string specifying the name of |
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| | | macroinstruction, which generated this line. |
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|--------|-------|---------------------------------------------------------|
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| +4 | dword | Bits 0-30 contain the number of this line. |
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| | | If the highest bit is zeroed, this line was loaded from |
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| | | source. |
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| | | If the highest bit is set, this line was generated by |
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| | | macroinstruction. |
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|--------|-------|---------------------------------------------------------|
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| +8 | dword | If the line was loaded from source, this field contains |
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| | | the position of the line inside the source file, from |
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| | | which it was loaded. |
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| | | If line was generated by macroinstruction, this field |
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| | | contains the offset of preprocessed line, which invoked |
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| | | the macroinstruction. |
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| | | If line was generated by instantaneous macro, this |
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| | | field is equal to the next one. |
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|--------|-------|---------------------------------------------------------|
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| +12 | dword | If the line was generated by macroinstruction, this |
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| | | field contains offset of the preprocessed line inside |
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| | | the definition of macro, from which this one was |
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| | | generated. |
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|--------|-------|---------------------------------------------------------|
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| +16 | ? | The tokenized contents of line. |
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\--------------------------------------------------------------------------/
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Notes:
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To determine, whether this is the line loaded from source, or generated by
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macroinstruction, you need to check the highest bit of the second double
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word.
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The contents of line is no longer a text, which it was in source file,
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but a sequence of tokens, ended with a zero byte.
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Any chain of characters that aren't special ones, separated from other
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similar chains with spaces or some other special characters, is converted
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into symbol token. The first byte of this element has the value of 1Ah,
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the second byte is the count of characters, followed by this amount of
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bytes, which build the symbol.
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Some characters have a special meaning, and cannot occur inside the
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symbol, they split the symbols and are converted into separate tokens.
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For example, if source contains this line of text:
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mov ax,4
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preprocessor converts it into the chain of bytes, shown here with their
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hexadecimal values (characters corresponding to some of those values are
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placed below the hexadecimal codes):
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1A 03 6D 6F 76 1A 02 61 78 2C 1A 01 34 00
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m o v a x , 4
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The third type of token that can be found in preprocessed line is the
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quoted text. This element is created from chain of any bytes other than
|
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line breaks that are placed between the single or double quotes in the
|
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|
|
original text. First byte of such element is always 22h, it is followed
|
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|
by double word which specifies the number of bytes that follow, and the
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|
value of quoted text comes next. For example, this line from source:
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|
|
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|
mov eax,'ABCD'
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|
|
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||
|
|
is converted into (the notation used is the same as in previous sample):
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|
|
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1A 03 6D 6F 76 1A 03 65 61 78 2C 22 04 00 00 00 41 42 43 44 00
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m o v e a x , A B C D
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|
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||
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This data defines two symbols followed by symbol character, quoted text
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and zero byte that marks end of line.
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There is also a special case of symbol token with first byte having the
|
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|
|
value 3Bh instead of 1Ah, such symbol means that all the line elements
|
||
|
|
that follow, including this one, have already been interpreted by
|
||
|
|
preprocessor and are ignored by assembler.
|
||
|
|
|
||
|
|
|
||
|
|
Table 4 Row of the assembly dump
|
||
|
|
/-------------------------------------------------------------------------\
|
||
|
|
| Offset | Size | Description |
|
||
|
|
|========|=======|========================================================|
|
||
|
|
| +0 | dword | Offset in output file. |
|
||
|
|
|--------|-------|--------------------------------------------------------|
|
||
|
|
| +4 | dword | Offset of line in preprocessed source. |
|
||
|
|
|--------|-------|--------------------------------------------------------|
|
||
|
|
| +8 | qword | Value of $ address. |
|
||
|
|
|--------|-------|--------------------------------------------------------|
|
||
|
|
| +16 | dword | Extended SIB for the $ address, the first two bytes |
|
||
|
|
| | | are register codes and the second two bytes are |
|
||
|
|
| | | corresponding scales. |
|
||
|
|
|--------|-------|--------------------------------------------------------|
|
||
|
|
| +20 | dword | If the $ address is relocatable, this field contains |
|
||
|
|
| | | information about section or external symbol, to which |
|
||
|
|
| | | it is relative - otherwise this field is zero. |
|
||
|
|
| | | When the highest bit is cleared, the address is |
|
||
|
|
| | | relative to a section, and the bits 0-30 contain |
|
||
|
|
| | | the index (starting from 1) in the table of sections. |
|
||
|
|
| | | When the highest bit is set, the address is relative |
|
||
|
|
| | | to an external symbol, and the bits 0-30 contain the |
|
||
|
|
| | | the offset of the name of this symbol in the strings |
|
||
|
|
| | | table. |
|
||
|
|
|--------|-------|--------------------------------------------------------|
|
||
|
|
| +24 | byte | Type of $ address value (as in table 2.2). |
|
||
|
|
|--------|-------|--------------------------------------------------------|
|
||
|
|
| +25 | byte | Type of code - possible values are 16, 32, and 64. |
|
||
|
|
|--------|-------|--------------------------------------------------------|
|
||
|
|
| +26 | byte | If the bit 0 is set, then at this point the assembly |
|
||
|
|
| | | was taking place inside the virtual block, and the |
|
||
|
|
| | | offset in output file has no meaning here. |
|
||
|
|
| | | If the bit 1 is set, the line was assembled at the |
|
||
|
|
| | | point, which was not included in the output file for |
|
||
|
|
| | | some other reasons (like inside the reserved data at |
|
||
|
|
| | | the end of section). |
|
||
|
|
|--------|-------|--------------------------------------------------------|
|
||
|
|
| +27 | byte | The higher bits of value of $ address. |
|
||
|
|
\-------------------------------------------------------------------------/
|
||
|
|
|
||
|
|
|
||
|
|
Notes:
|
||
|
|
|
||
|
|
Each row of the assembly dump informs, that the given line of preprocessed
|
||
|
|
source was assembled at the specified address (defined by its type, value
|
||
|
|
and the extended SIB) and at the specified position in output file.
|