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Updated: Wednesday, February 10, 2021
 
 

elfcompress (1)

Name

elfcompress - compress/decompress debug sections of an object file

Synopsis

elfcompress [-fV] [-c [!]class1,[!]class2,... | -n name]
     [-t cmp-type[,cmp-opt...]] file...

Description

The elfcompress command is used to compress or decompress sections in ELF object files. Unless otherwise specified, all debug and annotate sections are manipulated.

If the input file is an archive (see ar.h(3HEAD)), the archive is treated as a set of individual files. If the archive member is not an object file, then it is left unchanged.

elfcompress cannot modify a section that is contained within a segment. Such allocable sections have their SHF_ALLOC section flag set. elfcompress cannot modify sections of type SHT_NOBITS. The compression operation specified with the–t option may place additional limits on candidate sections. See the –t option, and NOTES.

When the –n option is used to specify one or more sections to process, only the specified sections are processed, and all other sections are left unmodified.

When the –n option is not used, elfcompress processes sections selected by the –c option that are compatible with the compression format specified with the –t option. By default, debug and annotate sections are compressed using the zlib format.

Options

The following options are supported:

–c [!]class1,[!]class2,...

Specify candidate sections. This option provides fine grained control over the selection of candidate sections to be manipulated. –c is used in conjunction with the –t option. If the –c option is not specified, elfcompress will default to the annotate and debug classes.

Each section class token can be prepended with a '!' to indicate that the class should not be a candidate.

The following classes of section can be defined.

nonalloc

Process any non-allocatable section. These sections are identified as not including the SHF_ALLOC section flag. This class encapsulates all of the other classes, except for the shstrtab class.

annotate

Process any annotation section. These sections provide information that is used by memory access tools, and coverage related tools. These sections are identified by having a SHT_SUNW_ANNOTATE section type.

comment

Process any comment section. These sections are identified by having a .comment section name.

debug

Process sections commonly used to contain debugging data. Debug sections are identified by having a .compcom, .debug*, .line, .stab*, .SUNW_ctf, or .zdebug* section name. These sections are also identified by having an SHT_PROGBITS, SHT_SUNW_DEBUG, or SHT_SUNW_DEBUGSTR section type.

shstrtab

Process the .shstrtab section used to hold ELF section names. This option is intended for specialized dynamic objects, and is not recommended for general use.

sort_sym_addr, sort_sym_name, sort, sort_sym

Process the symbol sort sections associated to SHT_SYMTAB symbol tables. Each of these symbol tables typically have associated symbol sort sections, sorted by address, and by name.

sort_sym_addr

By-address .symtab symbol sort sections (SHT_SUNW_symsort, SHT_SUNW_tlssort).

sort_sym_name

By-name .symtab symbol sort sections (SHT_SUNW_symnsort).

sort, sort_sym

All .symtab symbol sort sections. Equivalent to specifying both sort_sym_addr and sort_sym_name.

symbol

Process any non-allocatable symbol table. These sections are identified by having a SHT_SYMTAB section type. This class also encapsulates the sort classes. Any associated string table or symbol sort sections are also processed.

–f

By default, elfcompress will only compress sections if their resulting size is equal to or smaller than the original data. Specify –f to force compression even when the resulting size is larger than the original. The –f option is equivalent to specifying the –t force option.

–n name

Specifies the name of the section to process. elfcompress can take multiple –n options to allow for specification of multiple sections. If –n is not used, elfcompress selects all debug sections that are compatible with the specified compression operation. See the –t option, and NOTES.

–t cmp-type[,cmp-opt...]

Specifies the compression operation to be performed. If the –t option is not specified, elfcompress will default to zlib. The following compression types are recognized.

none

Compressed sections are decompressed.

zlib

Compress debug sections with ZLIB compression. The candidate sections for compression can be specified using the –c option. If –c is not present, elfcompress defaults to compressing annotate and debug sections, as if the –c annotate,debug option had been set. The resulting sections will have the SHF_COMPRESSED section flag set to identify the use of compression.

zlib-gnu

Compress debug sections with ZLIB compression, using the GNU section compression format. Candidate sections must be non-allocable (SHF_ALLOC flag not set), cannot have type SHT_NOBITS, and must have a name that begins with .debug. The resulting section will be renamed to start with .zdebug, to identify the use of compression.

The following cmp-opt option can be specified.

force

By default, elfcompress will only compress sections if their resulting size is equal to or smaller than the original data. Specify force to force compression even when the resulting size is larger than the original.

–V
–-version

Print version information.

–?
–-help

Print usage message and immediately exit.

Notes

The zlib-gnu compression format is limited to sections with names that start with .debug, while the default zlib compression format can be applied to sections with arbitrary names. When –t zlib-gnu is specified, and the –n option is not, any previously compressed sections with names that are incompatible with the zlib-gnu format are decompressed.

The elfcompress command is unable to modify core files.

The elfcompress –c and –t options correspond to the ld –z compress-class and –z compress-sections options, respectively. Performing these operations at link-edit time, rather than using elfcompress to post process objects is more efficient, but otherwise equivalent. See ld(1).

Examples

Example 1 Apply zlib compression to all debug sections
% elfcompress file
Example 2 Decompress all debug sections
% elfcompress -t none file
Example 3 Compress the .debug_info section, using the GNU-style format
% elfcompress -t zlib-gnu -n .debug_info file
Example 4 Compress the .symtab symbol table and all related sections
% elfcompress -c symbol file
Example 5 Compress .symtab symbol table and all related sections, excluding symbol sort sections
% elfcompress -c 'symbol,!sort' file

Files

/tmp/elfcompress_*

temporary files

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Availability
developer/base-developer-utilities
Interface Stability
Committed

See Also

ar(1), as(1), ld(1), mcs(1), strip(1), elf(3ELF), ar.h(3HEAD), zlib(3), a.out(5), attributes(7)

Oracle Solaris 11.4 Linkers and Libraries Guide