RealView Compilation Tools Utilities Guide: 2.1. Protecting code in images and objects with fromelf

2.1. Protecting code in images and objects with fromelf

If you are delivering images and objects to third parties, then you might want to protect the code they contain. To help you to protect this code, fromelf provides the --strip option and the --privacy option. These options remove or obscure the symbol names in the object or image. The option you choose depends on the how much information you want to remove. The effect of these options is different for object files and images.

Note

You must use --elf with these options. Because you have to use --elf, you must also use --output.

To protect code in image files:

Table 2.1. Effect of fromelf --privacy and --strip options on images files

Option Local symbols Section names Mapping symbols Build attributes

Option	Local symbols	Section names	Mapping symbols	Build attributes
fromelf --elf --privacy	Removes the whole symbol table. Removes the `.comment` section name. This is marked as `[Anonymous Section]` in the fromelf --text output. Gives section names a default value. For example, changes code section names to `'.text'`.
fromelf --elf --strip=symbols	Removes whole symbol table. Section names remain the same.
fromelf --elf --strip=localsymbols	Removed	Present	Removed	Present

fromelf --elf --privacy

Removes the whole symbol table.

Removes the .comment section name. This is marked as [Anonymous Section] in the fromelf --text output.

Gives section names a default value. For example, changes code section names to '.text'.

fromelf --elf --strip=symbols

Removes whole symbol table.

Section names remain the same.

fromelf --elf --strip=localsymbols Removed Present Removed Present

To protect code in object files:

Table 2.2. Effect of fromelf --privacy and --strip options on object files

Option Local symbols Section names Mapping symbols Build attributes

Option	Local symbols	Section names	Mapping symbols	Build attributes
fromelf --elf --privacy	Removes those local symbols that can be removed without loss of functionality. Symbols that cannot be removed, such as the targets for relocations, are kept. For these symbols, the names are removed. These are marked as `[Anonymous Symbol]` in the fromelf --text output.	Gives section names a default value. For example, changes code section names to `'.text'`	Present	Present
fromelf --elf --strip=symbols	Removes those local symbols that can be removed without loss of functionality. Symbols that cannot be removed, such as the targets for relocations, are kept. For these symbols, the names are removed. These are marked as `[Anonymous Symbol]` in the fromelf --text output.	Section names remain the same	Present	Present
fromelf --elf --strip=localsymbols	Removes those local symbols that can be removed without loss of functionality. Symbols that cannot be removed, such as the targets for relocations, are kept. For these symbols, the names are removed. These are marked as `[Anonymous Symbol]` in the fromelf --text output.	Section names remain the same	Present	Present

fromelf --elf --privacy

Removes those local symbols that can be removed without loss of functionality.

Symbols that cannot be removed, such as the targets for relocations, are kept. For these symbols, the names are removed. These are marked as [Anonymous Symbol] in the fromelf --text output.

Gives section names a default value. For example, changes code section names to '.text'

Present

fromelf --elf --strip=symbols

Removes those local symbols that can be removed without loss of functionality.

Symbols that cannot be removed, such as the targets for relocations, are kept. For these symbols, the names are removed. These are marked as [Anonymous Symbol] in the fromelf --text output.

Section names remain the same

Present

fromelf --elf --strip=localsymbols

Removes those local symbols that can be removed without loss of functionality.

Symbols that cannot be removed, such as the targets for relocations, are kept. For these symbols, the names are removed. These are marked as [Anonymous Symbol] in the fromelf --text output.

Section names remain the same

Present

The following example produces a new ELF executable image with the complete symbol table removed and various section names changed, use:

fromelf --elf --privacy --output=outfile.axf infile.axf

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