150 lines
3.8 KiB
Text
150 lines
3.8 KiB
Text
.TH OBJECT 2
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.SH NAME
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objtype, readobj, objtraverse, isar, nextar, readar \- object file interpretation functions
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.br
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.B #include <bio.h>
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.br
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.B #include <mach.h>
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.PP
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.ta \w'\fLmachines 'u
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.B
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int objtype(Biobuf *bp, char **name)
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.PP
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.B
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int readobj(Biobuf *bp, int objtype)
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.PP
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.B
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void objtraverse(void(*)(Sym*, void*), void*)
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.PP
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.B
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int isar(Biobuf *bp)
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.PP
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.B
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int nextar(Biobuf *bp, int offset, char *buf)
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.PP
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.B
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int readar(Biobuf *bp, int objtype, vlong end, int doautos)
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.SH DESCRIPTION
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These functions provide machine-independent access to object files
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in a directory or an archive.
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.IR Mach (2)
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and
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.IR symbol (2)
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describe additional library functions
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for interpreting executable files and executing images.
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.PP
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Object files contain no formal symbol table; instead, references
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to symbols must be extracted from the encoded object representation
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and resolved. The resulting symbol information is loaded
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into a dummy symbol table where it is available for processing by an
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application. The organization of the dummy symbol
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table is identical
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to that produced by the loader and described in
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.IR symbol (2)
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and
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.IR a.out (6):
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a vector of
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.B Sym
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data structures defining the name, type and relative offset of
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each symbol.
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.PP
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.I Objtype
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reads the header at the current position of the
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file associated with
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.I bp
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(see
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.IR Bio (2))
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to see if it is an intermediate object file.
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If it is, a code indicating the architecture type of the file
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is returned and the second argument, if it is non-zero,
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is set pointing to a string describing the type of the file.
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If the header does not indicate an object file,
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\-1 is returned.
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The header may be at the start of an object
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file or at the beginning of an archive member. The
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file is rewound to its starting
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position after decoding the header.
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.PP
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.I Readobj
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constructs a symbol table for the object file associated with
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.IR bp .
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The second argument contains the type code produced by
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function
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.IR objtype .
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The file must be positioned at the start of the object file.
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Each invocation of
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.I readobj
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destroys the symbol definitions for any previous file.
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.PP
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.I Objtraverse
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scans the symbol table previously built by
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.I readobj
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or
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.IR readar .
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.I Objtraverse
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requires two arguments:
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the address of a call-back function and a
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generic pointer. The call-back function
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is invoked once for each symbol in the symbol table with
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the address of a
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.I Sym
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data structure as the first argument and the
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generic pointer as the second.
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.PP
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.I Isar
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reads the header at the current point in the file
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associated with
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.I bp
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and returns 1 if it is an archive or zero otherwise.
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The file is positioned at the end of the archive
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header and at the beginning of the first member of the archive.
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.PP
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.I Nextar
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extracts information describing the archive member stored
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at
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.I offset
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in the file associated with
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.IR bp .
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If the header describing the member can be
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extracted and decoded, the size of the member is
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returned. Adding this value to
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.I offset
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yields the offset of the beginning of the next member
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in the archive. On return the input file is positioned
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at the end of the member header
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and the name of the member is stored in
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.IR buf ,
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a buffer of
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.B SARNAME
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characters.
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If there are no more members,
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.I nextar
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returns zero; a negative return indicates a missing
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or malformed header.
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.PP
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.I Readar
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constructs the symbol table of the object file stored
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at the current position in the archive associated with
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.IR bp .
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This function operates exactly as
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.IR readobj ;
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the only difference is the extra argument,
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.IR end ,
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specifying the offset to the beginning of the
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next member in the archive.
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.I Readar
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leaves the file positioned at that point.
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.SH SOURCE
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.B /sys/src/libmach
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.SH "SEE ALSO"
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.IR mach (2),
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.IR symbol (2),
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.IR bio (2),
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.IR a.out (6)
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.SH DIAGNOSTICS
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These routines set
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.IR errstr .
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