HelenOS sources

__CONTEXT_OFFSET_X21   36 uspace/lib/c/arch/arm64/include/libarch/fibril_context.h #define __CONTEXT_OFFSET_X21    0x20
__CONTEXT_OFFSET_X21   54 uspace/lib/c/arch/riscv64/include/libarch/fibril_context.h #define __CONTEXT_OFFSET_X21  0xb0