elfwrap - wrap data in anELFfile
elfwrap [-64] [-e end-symbol] [-n section-name] [-o relobj-file] [-s start-symbol] [-V] [-z target=sparc | x86] data-file ...
The elfwrap utility creates an ELF relocatable object file from one or more data files. The relocatable object encapsulates each data file within an individual section, together with symbols that can be used to reference the section. The relocatable object is appropriate for inclusion with a subsequent link-edit. Users can reference the encapsulated data using the associated symbols.
By default, a 32–bit ELF relocatable object is created that is appropriate for the machine on which elfwrap is executed. The –64 option can be used to create a 64–bit ELF relocatable object. The –z target option can be used to create a relocatable object for a specific machine type.
By default, the relocatable object a.wrap.o is created. The –o option can be used to specify an alternative relocatable object name.
By default, the base name of each data file, as define by the basename(1) utility, is used to create section and symbol names that are assigned to the associated data. The –e, –n, and –s options can be used to override these defaults. Without these options, an input data file ISV/isv-data, has the following ELF information associated to the data within the output relocatable object.
This section contains the entire contents of the input data file. The section is also identified with the SHF_SUNW_ELFWRAP section flag.
This symbol reflects the starting address of the .isv-data section.
This symbol reflects the address of the first location after the .isv-data section.
The following options are supported:
Create a 64–bit ELF relocatable object.
Specifies the symbol name to be associated with the end of the input data file that follows this option on the command line.
Specifies the section name to be used for the input data file that follows this option on the command line.
Produce a relocatable object that is named relobj-file.
Specifies the symbol name to be associated with the start of the input data file that follows this option on the command line.
Specifies the machine type for the output relocatable object. Supported targets are sparc and x86. The 32–bit machine type for the specified target is used unless the –64 option is also present, in which case the corresponding 64–bit machine type is used. By default, the relocatable object that is generated is 32–bit for the machine one which elfwrap is executed.
Print version information and immediately exit.
Print usage message and immediately exit.
The –e, –n, and –s options are associated to the input data files that follow these options on the command line. These options can be repeated, prior to any input data file, to associate unique names to each data file. Applying the same –e, or –s options to more than one input data file results in multiply defined symbols being defined within the relocatable object being created. This may render the object unsuitable for additional link-editing. Multiple use of these options in this manner results in warning messages from elfwrap.
The following example encapsulates the system passwd file and the system group file within a relocatable object passgroup.o.
example% elfwrap -o passgroup.o /etc/passwd /etc/group example% elfdump -c -T PROGBITS passgroup.o Section Header[1]: sh_name: .passwd sh_addr: 0 sh_flags: [ SHF_ALLOC SHF_SUNW_ELFWRAP ] sh_size: 0x5a2 sh_type: [ SHT_PROGBITS ] ... Section Header[2]: sh_name: .group sh_addr: 0 sh_flags: [ SHF_ALLOC SHF_SUNW_ELFWRAP ] sh_size: 0x199 sh_type: [ SHT_PROGBITS ] ... example% elfdump -s passgroup.o | egrep "passwd|group" [2] 0 0 SECT LOCL D 0 .passwd [3] 0 0 SECT LOCL D 0 .group [7] 0 0x5a2 OBJT GLOB D 0 .passwd passwd_start [8] 0x5a2 0 OBJT GLOB D 0 .passwd passwd_end [9] 0 0x199 OBJT GLOB D 0 .group group_start [10] 0x199 0 OBJT GLOB D 0 .group group_end example% strings -N.passwd passgroup.o | head -1 root:x:0:0:Super-User:/:/usr/sbin/sh example% strings -N.group passgroup.o | head -1 root::0:
The password data within the relocatable object can be referenced from the following user code.
example% cat main.c #include <stdio.h> extern char passwd_start, passwd_end; void main() { char *pstart = &passwd_start, *pend = &passwd_end; char *str, *lstr; for (lstr = str = pstart; str < pend; str++) { if ((*str == '\n') && (str != (pend - 1))) { (void) printf("%.*s", (++str - lstr), lstr); lstr = str; } } } example% cc -o main main.c passgroup.o example% ./main root:x:0:0:Super-User:/:/usr/sbin/sh .... nobody4:x:65534:65534:SunOS 4.x NFS Anonymous Access User:/:
The following example uses the same input files, but assigns their data to a common section name, and associates unique symbol names to each data.
example% elfwrap -o passgroup.o -n .rodata \ -s P_START -e P_END /etc/passwd \ -s G_START -e G_END /etc/group example% elfdump -c -T PROGBITS passgroup.o Section Header[1]: sh_name: .rodata sh_addr: 0 sh_flags: [ SHF_ALLOC SHF_SUNW_ELFWRAP ] sh_size: 0x5a2 sh_type: [ SHT_PROGBITS ] ... Section Header[2]: sh_name: .rodata sh_addr: 0 sh_flags: [ SHF_ALLOC SHF_SUNW_ELFWRAP ] sh_size: 0x199 sh_type: [ SHT_PROGBITS ] ... example% elfdump -s passgroup.o | fgrep .rodata [2] 0 0 SECT LOCL D 0 .rodata [3] 0 0 SECT LOCL D 0 .rodata [7] 0 0x5a2 OBJT GLOB D 0 .rodata P_START [8] 0x5a2 0 OBJT GLOB D 0 .rodata P_END [9] 0 0x199 OBJT GLOB D 0 .rodata G_START [10] 0x199 0 OBJT GLOB D 0 .rodata G_END
The default relocatable object file created.
See attributes(7) for descriptions of the following attributes:
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elfdump(1), ld(1), strings(1), elf(3ELF), attributes(7), ddi_modopen(9F)
Oracle Solaris 11.4 Linkers and Libraries Guide
Any data encapsulated with elfwrap must be in a format appropriate for the destination target.
The name of the input file drives the creation of the symbol names to associate with the input file data. Therefore, input files should be uniquely named to avoid the creation of symbols with the same name.