在 ELF 规范中,BA_OS 和 KE_OS 是什么意思?

In the ELF spec, what does BA_OS and KE_OS mean?

ELF spec excerpted from the System V ABI, various functions are referenced as exec(BA_OS), as on page 7 of 1。其他函数用 KE_OS 引用。这些 *_OS 符号是什么意思?

原来latest base document的第11页描述了"components of conforming systems",其中"BA"表示"base system","KE"表示"kernel extension",而"OS" 表示 "operating system service routines","LIB" 表示 "general library routines"。