syslib

---

'syslib' contains minimum required for embedded RISC-V project.

syslib content

• Startfile startup.S
• Ld-script linker.ld
• Functions for work with interrupts (PLIC and CLINT drivers, handlers etc.)
• Others

To use syslib it is necessary to include syslib/syslib.h.

Startfile

Function _init() called inside __libc_init_array() in startup.S. _init() is user defined function which contains any additional actions before main(). Function _init() must be declared and defined by user otherwise project can't be linked. In this implementation symbol _init is declared and defined immediately in startup.S (empty function).

main.cpp contains examples of function calls.

Build and link

Toolchain: RISC-V GCC/Newlib (riscv64-unknown-elf-gcc).
Use compiler version which does not ignore __attribute__((interrupt)) (version gcc-2018.07.0-x86_64_... or newer).

Link with flag -nostartfiles.

__libc_init_array() is the part of libc, so it is necessary to link project with newlib:

    `-L"\...\riscv64-unknown-elf\lib\rv64imafdc\lp64d"`

For optimization, it can be used keys:

• -fno-exceptions
• -fno-unwind-tables
• -fno-use-cxa-atexit (static object destructors)
• -fno-threadsafe-statics
• -Xlinker --gc-sections (Remove unused sections). It will be more effective with -ffunction-sections and -fdata-sections
• -fno-rtti (dynamic cast)

Quick start

Set actual paths in file '/syslib/paths'.

Build project:

    make

Launch with hardware:

    cd ./launch-sh/
    ./openocd_gdb_launch.sh ../Debug/syslib.elf

Launch with Spike:

    cd ./launch-sh/
    ./spike_openocd_gdb_launch.sh ../Debug/syslib.elf