diodesign / itsylinker

A minimal 64-bit RISC-V (RV64I) ELF linker

itsylinker

Generate 64-bit RISC-V (RV64I) ELF executables from suitable ELF object files. The goal of this project is to produce a minimalist, stable linker in Rust primarily for the Diosix project.

itsylinker is compatible with a subset of the binutils ld command-line interface. The invocation for a typical application ELF execuable would be:

itsylinker -o <output filename> -T <config filename> -L <search path> <list of object filenames>

For example to create the ELF executable myapp using the configuration file link.toml:

itsylinker -o myapp -T link.toml -L target/debug rt0.o main.o

Where rt0.o contains the entry point and runtime startup code, main.o contains the application's code, and both .o files are in the target/debug directory.

A TOML configuration file must be provided using the command line switch -T <config filename> to direct the linking process. Below is the link.toml configuration file for the example myapp executable:

/* set the entry point to the symbol _start, which should be in rt0,
   align the program to the nearest 4096 bytes when loaded into memory,
   produce a dynamically relocatable ELF executable */
[output]
entry = "_start"
alignment = 4096
dynamic_relocation = true

[section.text]
include = [ ".rt0*", ".text*", ".rodata*" ]
alignment = 8

[section.data]
include = [ ".data*" ]
alignment = 8

/* define __bss_start and __bss_end with an 8-byte alignment
   as the start and end addresses of the section.
   this can be used by the rt0 startup code to zero the bss */
[section.bss]
include = [ ".bss*" ]
alignment = 8
start_symbol = "__bss_start"
end_symbol = "__bss_end"

Contact and code of conduct

Please email project lead Chris Williams if you have any questions or issues to raise, wish to get involved, have source to contribute, or have found a security flaw. You can, of course, submit pull requests or raise issues via GitHub, though please consider disclosing security-related matters privately. Please also observe the Diosix project's code of conduct if you wish to participate.

Copyright and license

Copyright © Chris Williams, 2021. See LICENSE for distribution and use of source code and binaries.