resetvector.s

完整的Bell实验室的嵌入式文件系统TFS

/* resetvector.s:
 *
 * The PowerPC 403GCX (and others) resets at the top of its 32-bit
 * physical memory space at address 0xfffffffc.
 * This means that the monitor must be built with a branch instruction
 * at that location that will take it to the coldstart point of the
 * monitor executable.
 * If the tools worked properly, I should be able to do this in the
 * monXXX.lnk file by specifying that the .text of this file be placed
 * at location 0xfffffffc.  It's four bytes long and would be placed
 * at the last four bytes of the flash device.  Unfortunately, for some
 * reason the linker does not let me do this, it apparently thinks the
 * end of memory is at 0xfffffffe and says that I don't have 4 bytes left
 * starting at 0xfffffffc.  Because of this, I link this .text space to
 * location 0xfffffff8 and then insert 4 0xffs into the binary using the
 * elf -i option (see makefile).  Klunky, but I can't get around the 
 * fact that the linker won't let me do it the right way!!!
 *
 * To allow the starting point of the monitor to grow downward, but still
 * not affect the location of the moncomptr, we also put moncomptr here.
 * The end result (after elf -i) is that moncomptr will be at 0xfffffff0
 * and resetvector will be at 0xfffffffc.  Refer to the make file for
 * one of the PPC403 or PPC405 targets.
 *
 * General notice:
 * This code is part of a boot-monitor package developed as a generic base
 * platform for embedded system designs.  As such, it is likely to be
 * distributed to various projects beyond the control of the original
 * author.  Please notify the author of any enhancements made or bugs found
 * so that all may benefit from the changes.  In addition, notification back
 * to the author will allow the new user to pick up changes that may have
 * been made by other users after this version of the code was distributed.
 *
 * Author:  Ed Sutter
 * email:   [e-mail]
 * phone:   [phone]
 *
 */
    .file "resetvector.s"
    .globl  resetvector
    .globl  moncomptr
    .extern coldstart
    .extern moncom

moncomptr:
    .long   moncom
    .long   0xffffffff

resetvector:
    ba coldstart