KGZIP(8) BSD System Manager's Manual KGZIP(8)NAMEkgzip — compress a kernel
SYNOPSISkgzip [-cv] [-f format] [-l loader] [-o output] file
DESCRIPTION
The kgzip utility compresses a kernel or some other bootable binary.
Operation is in two phases as follows:
1. A load image of the executable file is built which omits all but the
‘text’ and ‘data’ segments. This image is compressed using gzip(1)
and output as data in relocatable object format.
2. The object file is linked with a special self-hosting loader, pro‐
ducing an executable suitable for booting with either the second- or
third-level bootstraps.
Supported object formats are 32-bit ELF and a.out ZMAGIC.
If the file operand has a ‘.o’ suffix, input is assumed to be for the
link phase, and the first phase is omitted.
The options are:
-c Omit the link phase.
-v Display object file information.
-f format Use format as the output format, where format is ‘aout’ or
‘elf’. The default format is ELF.
-l loader Link loader as the loader.
-o output Name the output file output. The default is to use the input
name with the suffix ‘.o’ (for relocatables) or ‘.kgz’ (for
executables).
NOTES
Global variables equivalent to the following are defined in the output:
struct kgz_hdr {
char ident[4]; /* identification: "KGZ" */
uint32_t dload; /* decoded image load address */
uint32_t dsize; /* decoded image size */
uint32_t isize; /* image size in memory */
uint32_t entry; /* entry point */
uint32_t nsize; /* encoded image size */
} kgz;
uint8_t kgz_ndata[]; /* encoded data */
The encoded data is simply gzip(1) output: a header (with no optional
fields); compressed data; and 32-bit CRC and size values.
FILES
/usr/lib/kgzldr.o The default loader
EXIT STATUS
The kgzip utility exits 0 on success, and >0 if an error occurs.
SEE ALSOgzip(1), ld(1), a.out(5), elf(5), boot(8), loader(8)AUTHORS
Robert Nordier ⟨rnordier@FreeBSD.org⟩.
BUGS
As symbols are lost, the usefulness of this utility for compressing ker‐
nels is limited to situations where loader(8) cannot be used; otherwise
the preferred method of compressing a kernel is simply to gzip(1) it.
BSD July 19, 1999 BSD
