previous frame pointer

基本解释

The back chain pointer points to the back chain pointer of the previous stack frame.
回链指针指向前一个堆栈框架的回链指针。
The final item in the stack frame is a pointer to the previous stack frame, often called the back pointer.
堆栈帧中的最后一个条目是一个指向前一堆栈帧的指针，通常被称为后向指针（back pointer）。
Each stack frame holds a pointer to the previous stack frame (called the back chain pointer), as well as a space for return addresses for when it calls other functions.
每个堆栈框架都有一个指向前一个堆栈框架的指针（称为回链指针），还有一个当它调用其他函数时用于存放返回地址的空间。