HelenOS sources

htif_putuchar      44 kernel/arch/riscv64/include/arch/drivers/ucb.h extern void htif_putuchar(outdev_t *, const char32_t);
htif_putuchar      44 kernel/arch/riscv64/src/drivers/ucb.c 	.write = htif_putuchar,
HelenOS homepage, sources at GitHub