About fromELF

 

一、About fromELF

The fromELF utility translates Executable Linkable Format (ELF) image files produced by armlink into other formats suited to ROM tools and to loading directly into memory. You can also use it to display various information about an ELF object or to generate text files containing the information.

fromELF outputs the following image formats:

• Plain binary format.

• Motorola 32-bit S-record format.

• Intel Hex-32 format.

• Byte Oriented (Verilog Memory Model) Hex format.

• ELF format. You can resave as ELF. For example, you can convert a -debug ELF image to a -nodebug ELF image).

fromELF can also display information about the input file, for example disassembly output or symbol listings, to either standard output or a text file.

Note

Do not link your images with the -nodebug linker option if you require a -fieldoffsets fromELF step. If your image is produced without debug information:

• fromELF cannot translate the image into other file formats

• fromELF cannot produce a meaningful disassembly listing.

二、fromELF command-line options

The fromELF command syntax is as follows:

fromelf [-help] [ -fieldoffsets [[-select select_options]]] [-nolinkview] [-nodebug] [-vsn] [[text_output_format] |  code_output_format] [-base n] [memory_config] [-output output_file] {input_file}

where:

-help

This option shows help and usage information. If this option is specified, other command-line options are ignored. Calling fromELF without any parameters produces the same help information.

-fieldoffsets

This option produces, to standard output, a list of assembly language EQU directives that equate C++ class or C structure field names to their offsets from the base of the class or structure. The input ELF file can be a relocatable object or an image.

Use -o to redirect the output to a file. Use the INCLUDE command from armasm to load the produced file and provide access to C++ classes and C structure members by name from assembly language. See the ADS Assembler Guide for more information on armasm.

Note

If the source file does not have debug information, this option is not available. You cannot use this option together with a code_output_format.

-fieldoffsets outputs all structure information. To output a subset of the structures, use -select select_options.

If you do not require a file that can be input to armasm, use the -text -a option to format the display addresses in a more readable form. The -a option only outputs address information for structures and static data in images because the addresses are not known in a relocatable object.

-select select_options

Use -select select_option together with either the -fieldoffsets or -text -a options to select only those fields that match the patterns in the option list.

Use special characters to select multiple fields:

• Join options in the list together with a , as in: a*,b*,c*.

• The wildcard character * can be used to match any name.

• The wildcard character ? can be used to match any single letter.

• Specify the fields to include by prefixing a + to the select_option string. This is the default.

• Specify the fields to exclude by prefixing a ~ to the select_option string.

If you are using a special character on Unix, you must enclose the options in quotes to prevent the shell expanding the selection.

-nolinkview

Use -nolinkview to discard the section-level view (link-time view) from the ELF image and retain only the segment level view (load-time view). Discarding the link-view section level eliminates:

• the section header table

• the section header string table

• the string table

• the symbol table

• all debug sections.

All that is left in the output is the program header table and the program segments. According to the ELF specification, these are all that a program loader can rely upon being present in an ELF file.

Caution

This option can have unexpected effects if -elf is not specified on the command line. See Example 7.2 for an example of correct usage.

-nodebug

This option does not put debug information in the output files. This is the default for binary images. If -nodebug is specified, it affects all output formats. It overrides the -text -g option.

Caution

This option can have unexpected effects if -elf is not specified on the command line. The options in Example 7.1 produce a text file because no output format has been specified.

Example 7.1. Text output

fromelf -nodebug image -o image_nodb.asf 

To get ELF format output use the options shown in Example 7.2

Example 7.2. ELF output

fromelf -elf -nodebug image.axf -o image_ndb.axf

-vsn

This option displays fromELF version information.

text_output_format

Use a text specification, for example -text -c, to display image information in text format. You can decode an ELF image or ELF object file using this option. This is the default. If no text or code output format is specified, -text is assumed.

If output_file is not specified with the -o option, the information is displayed on stdout.

If a specific text category is not specified, the default is to output header information.

If specified, the text category consists of one or more of the following:

a

Prints the global and static data addresses (including addresses for structure and union contents). This option can only be used on files containing debug information. Use the -select option to output a subset of the data addresses.

c

Disassembles code

d

Prints contents of the data sections

g

Prints debug information

r

Prints relocation information

s

Prints the symbol table

t

Prints the string table(s)

v

Prints detailed information on each segment and section header of the image

z

Prints the code and data sizes.

The category selectors can be specified as one of:

• individual options, -text -c -d

• a single concatenated string, -text -cd

• category selectors only, -c -d

• multiple characters following a slash character, -text/cd.

If an output format is not specified, the default output format of -text is used and the individual category selectors are recognized. If another output format is specified, the selectors are ignored.

code_output_format

This option selects the binary or ELF output file options. code_output_format can be one of:

-bin

Plain binary. You can split output from this option into multiple files with the memory_config option.

-ihf

Extended Intellec Hex format. You can specify the base address of the output with the -base option. (This option is deprecated and will be removed from future versions of the product.)

-m32

Motorola 32-bit format (32-bit S-records). You can specify the base address of the output with the -base option.

-i32

Intel Hex-32 format. You can specify the base address of the output with the -base option.

-vhx

Byte Oriented (Verilog Memory Model) Hex format. This format is suitable for loading into the memory models of HDL simulators. You can split output from this option into multiple files with the memory_config option.

-elf

ELF format (resaves as ELF). This can be used to convert a debug ELF image into a no-debug ELF image.

If you use fromELF to convert an ELF image containing multiple load regions to a binary format using any of the -bin, -ihf, -m32, -i32, or -vhx options, fromELF creates an output directory named output_file and generates one binary output file for each load region in the input image. fromELF places the output files in the output_file directory.

ELF images contain multiple load regions if, for example, they are built with a scatter-load description file that defines more than one load region.

-base n

This option specifies the base address of the output for Motorola S-record, Intel Hex, and Extended Intellec Hex file formats. This option is available only if -m32, -i32, or -ihf is specified as the output format.

You can specify the base address as either:

• a decimal value, for example -base 0

• as a hexadecimal value, for example -base 0x8000.

All addresses encoded in the output file start at the base address n. If you do not specify a -base option, the base address is taken from the load region address.

Note

If multiple load regions are present, the -base value is used for each output file. That is, it overrides all load region addresses.

memory_config

This option outputs multiple files for multiple memory banks. This option is available only if -vhx or -bin is specified as the output format.

The format of memory_config is -widthxbanks where:

width

is the width of memory in the target memory system (8-bit, 16-bit, 32-bit, or 64-bit).

banks

specifies the number of memory banks in the target memory system.

Valid configurations are:

-8x1
-8x2
-8x4
-16x1
-16x2
-32x1
-32x2
-64x1

fromELF uses the last specified configuration if more than one configuration is specified. If this option is selected for any format other than -bin or -vhx it is ignored.

If the image has one load region, fromELF generates bank files with the following naming conventions:

• If there is one memory bank (banks is 1) the output file is named by the -o output_file argument.

• If there are multiple memory banks (bank>1), fromELF generates banks number of files starting with output_file0 and finishing with output_file bank-1. For example:

  
  fromelf -vhx -8x2 test.axf -o test

  generates two files named test0 and test1.

If the image has multiple load regions, fromELF creates a directory named output_file and generates bank files for each load region named load region0 to load region banks-1.

The memory width specified by width controls the size of the chunk of information read from the image and written to a file. The first chunk read is allocated to the first file (output_file0), the next chunk is allocated to the next file. After a chunk is allocated to the last file, allocation begins again with the first file (that is, the allocation is modulo based on the number of files). For example:

For a memory_config of -8x4

byte0 -> file0
byte1 -> file1
byte2 -> file2 
byte3 -> file3 
byte4 -> file0 
...

For a memory_config of -16x2

halfword0 -> file0 
halfword1 -> file1 
halfword3 -> file0 
...

-output output_file

This option specifies the name of the output file, or the name of the output directory if multiple output files are created (see the description of text_output_format and code_output_format for more information). Specifying the output file is optional with the -text output option and mandatory with all other outputs.

input_file

This option specifies the ELF file to be translated.

fromELF accepts only ARM-executable ELF files and ARM object ELF files (.o). If input_file is a scatter-loaded image that contains more than one load region and the output format is either -bin, -ihf, -m32, -i32, or -vhx, fromELF creates a separate file for each load region.