armv6: bcm2835 & qvpb have nearly identical locore _start
It makes sense to common-ize _start for all armv6 machines.  They will all
have to do the same basic setup.  If there is any machine specific setup
they need to do, they can do so in the new _mach_start function.

          --- old/usr/src/uts/armv6/bcm2835/ml/locore.s
          +++ new/usr/src/uts/armv6/bcm2835/ml/locore.s

   1    1  /*
   2    2   * This file and its contents are supplied under the terms of the
   3    3   * Common Development and Distribution License ("CDDL"), version 1.0.
   4    4   * You may only use this file in accordance with the terms of version
   5    5   * 1.0 of the CDDL.
   6    6   *
   7    7   * A full copy of the text of the CDDL should have accompanied this
   8    8   * source.  A copy of the CDDL is also available via the Internet at
   9    9   * http://www.illumos.org/license/CDDL.
  10   10   */

  11   11  
  12   12  /*
  13   13   * Copyright 2013 (c) Joyent, Inc. All rights reserved.
  14   14   * Copyright 2015 (c) Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
  15   15   */
  16   16  
  17   17  #include <sys/asm_linkage.h>
  18   18  #include <sys/machparam.h>
  19   19  #include <sys/cpu_asm.h>
  20   20  
  21      -/*
  22      - * Every story needs a beginning. This is ours.
  23      - */
  24      -
  25      -/*
  26      - * We are in a primordial world here. The BMC2835 is going to come along and
  27      - * boot us at _start. Normally we would go ahead and use a main() function, but
  28      - * for now, we'll do that ourselves. As we've started the world, we also need to
  29      - * set up a few things about us, for example our stack pointer. To help us out,
  30      - * it's useful to remember the rough memory map. Remember, this is for physcial
  31      - * addresses. There is no virtual memory here. These sizes are often manipulated
  32      - * by the 'configuration' in the bootloader.
  33      - *
  34      - * +----------------+ <---- Max physical memory
  35      - * |                |
  36      - * |                |
  37      - * |                |
  38      - * +----------------+
  39      - * |                |
  40      - * |      I/O       |
  41      - * |  Peripherals   |
  42      - * |                |
  43      - * +----------------+ <---- I/O base 0x20000000 (corresponds to 0x7E000000)
  44      - * |                |
  45      - * |     Main       |
  46      - * |    Memory      |
  47      - * |                |
  48      - * +----------------+ <---- Top of SDRAM
  49      - * |                |
  50      - * |       VC       |
  51      - * |     SDRAM      |
  52      - * |                |
  53      - * +----------------+ <---- Split determined by bootloader config
  54      - * |                |
  55      - * |      ARM       |
  56      - * |     SDRAM      |
  57      - * |                |
  58      - * +----------------+ <---- Bottom of physical memory 0x00000000
  59      - *
  60      - * With the Raspberry Pi Model B, we have 512 MB of SDRAM. That means we have a
  61      - * range of addresses from [0, 0x20000000). If we assume that the minimum amount
  62      - * of DRAM is given to the GPU - 32 MB, that means we really have the following
  63      - * range: [0, 0x1e000000).
  64      - *
  65      - * By default, this binary will be loaded into 0x8000. For now, that means we
  66      - * will set our initial stack to 0x10000000.
  67      - */
  68      -
  69      -/*
  70      - * Recall that _start is the traditional entry point for an ELF binary.
  71      - */
  72      -        ENTRY(_start)
  73      -        ldr sp, =t0stack
  74      -        ldr r4, =DEFAULTSTKSZ
  75      -        add sp, r4
  76      -        bic sp, sp, #0xff
  77      -
  78      -        /*
  79      -         * establish bogus stacks for exceptional CPU states, our exception
  80      -         * code should never make use of these, and we want loud and violent
  81      -         * failure should we accidentally try.
  82      -         */
  83      -        cps #(CPU_MODE_UND)
  84      -        mov sp, #-1
  85      -        cps #(CPU_MODE_ABT)
  86      -        mov sp, #-1
  87      -        cps #(CPU_MODE_FIQ)
  88      -        mov sp, #-1
  89      -        cps #(CPU_MODE_IRQ)
  90      -        mov sp, #-1
  91      -        cps #(CPU_MODE_SVC)
  92      -
  93      -        /* Enable highvecs (moves the base of the exception vector) */
  94      -        mrc     p15, 0, r3, c1, c0, 0
  95      -        mov     r4, #1
  96      -        lsl     r4, r4, #13
  97      -        orr     r3, r3, r4
  98      -        mcr     p15, 0, r3, c1, c0, 0
  99      -
       21 +        ENTRY(_mach_start)
 100   22          /* Enable access to p10 and p11 (privileged mode only) */
 101   23          mrc     p15, 0, r0, c1, c0, 2
 102   24          orr     r0, #0x00500000
 103   25          mcr     p15, 0, r0, c1, c0, 2
 104   26  
 105      -        bl _fakebop_start
 106      -        SET_SIZE(_start)
 107      -
 108      -        ENTRY(arm_reg_read)
 109      -        ldr r0, [r0]
 110      -        bx lr
 111      -        SET_SIZE(arm_reg_read)
 112      -
 113      -        ENTRY(arm_reg_write)
 114      -        str r1, [r0]
 115      -        bx lr
 116      -        SET_SIZE(arm_reg_write)
       27 +        bx      r14
       28 +        SET_SIZE(_mach_start)
    

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