0l, 5l, 6l, 8l, 9l, kl, ql, vl – loaders

8l [ option ... ] [ file ... ]

These commands load the named files into executable files for the corresponding architectures; see 8c(1) for the correspondence between an architecture and the character (6, 8, etc.) that specifies it. The files should be object files or libraries (archives of object files) for the appropriate architecture. Also, a name like –lext represents the library libext.a in /$objtype/lib, where objtype is one of 386, etc. as listed in 8c(1). If the environment variable ccroot is defined, the library is sought in $ccroot/$objtype/lib instead. The libraries must have tables of contents (see ar(1)).

In practice, –l options are rarely necessary as the header files for the libraries cause their archives to be included automatically in the load (see 8c(1)). For example, any program that includes header file libc.h causes the loader to search the C library /$objtype/lib/libc.a. Also, the loader creates an undefined symbol _main (or _mainp if profiling is enabled) to force loading of the startup linkage from the C library.

The order of search to resolve undefined symbols is to load all files and libraries mentioned explicitly on the command line, and then to resolve remaining symbols by searching in topological order libraries mentioned in header files included by files already loaded. When scanning such libraries, the algorithm is to scan each library repeatedly until no new undefined symbols are picked up, then to start on the next library. Thus if library A needs B which needs A again, it may be necessary to mention A explicitly so it will be read a second time.

The loader options are:
l       (As a bare option.) Suppress the default loading of the startup linkage and libraries specified by header files.
o out    Place output in file out. Default is O.out, where O is the first letter of the loader name.
p       Insert profiling code into the executable output; no special action is needed during compilation or assembly.
e       Insert (embedded) tracing code into the executable output; no special action is needed during compilation or assembly. The added code calls _tracein at function entries and _traceout at function exits.
s       Strip the symbol tables from the output file.
a       Print the object code in assembly language, with addresses.
v       Print debugging output that annotates the activities of the load.
M       (Kl only) Generate instructions rather than calls to emulation routines for multiply and divide.
EsymbolThe entry point for the binary is symbol (default _main; _mainp under –p).
x [ file ]   Produce an export table in the executable. The optional file restricts the exported symbols to those listed in the file. See dynld(2).
u [ file ]   Produce an export table, import table and a dynamic load section in the executable. The optional file restricts the imported symbols to those listed in the file. See dynld(2).
t       (5l and vl only) Move strings into the text segment.
f       (5l only) Generate VFP hardware floating–point instructions. Without this option, 5l generates arm7500 floating–point instructions which are emulated in the kernel.
Hn      Executable header is type n. The meaning of the types is architecture–dependent; typically type 1 is Plan 9 boot format and type 2 is the regular Plan 9 format, the default. These are reversed on the MIPS. The Next boot format is 3. Type 4 in vl creates a MIPS executable for an SGI Unix system. There is
often a type that produces ELF or ELF64 format; 5 for ELF is common. See obj.c in the source directory for a complete list.
k       (ELF only) Executable is a standalone boot image or kernel.
Tt      The text segment starts at (virtual) address t.
Pt      (ELF only) The text segment starts at physical address t (by default the text segment's virtual start address).
Dd      The data segment starts at address d.
Rr      The text segment is rounded to a multiple of r (if r is nonzero).
Ldir     For a library reference –lext, search dir before looking in the standard library directory. If more than one –L option is given, directories will be searched in order of appearance.

The numbers in the above options can begin with 0x or 0 to change the default base from decimal to hexadecimal or octal. The defaults for the values depend on the compiler and the header type.

The loaded image has several symbols inserted by the loader: etext is the address of the end of the text segment; bdata is the address of the beginning of the data segment; edata is the address of the end of the data segment; and end is the address of the end of the bss segment, and of the program.

/$objtype/lib   for –llib arguments.

/sys/src/cmd/8l, etc.

8c(1), 8a(1), ar(1), nm(1), db(1), prof(1)

Rob Pike, ``How to Use the Plan 9 C Compiler''

The list of loaders given above is only partial, not all architectures are supported on all systems, some have been retired and some are provided by third parties.
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