2 * Copyright (c) 2013-2014 Robert N. M. Watson
5 * This software was developed by SRI International and the University of
6 * Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
7 * ("CTSRD"), as part of the DARPA CRASH research programme.
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39 * Save arguments from the BERI firmware for use in C-land, and jump into
40 * main. Assume that registers/stack/etc are sufficiently initialised to get
41 * going. Notice that we use only temporaries while relocating, as we want to
42 * retain argument registers to pass in to main().
44 * Note slightly surprising structure: boot2 is linked for a specific address,
45 * but we may start running the code somewhere else (e.g., in DRAM as inserted
46 * with JTAG, or in flash). The starting assembly is therefore PIC, but the
47 * main body of the code is not PIC.
52 .global prerelocate_start
53 .ent prerelocate_start
57 * Calculate the actual run-time, pre-relocated value of
58 * 'start', which we will use as the source address for
59 * memcpy(). Note that although a symbol is used here, this
60 * should generate code for a short relative branch, leaving
61 * the previous $pc in $ra.
66 dsub $t1, $ra, 8 /* Src. */
69 * Relocate boot2 to DRAM where we can write back global
70 * variable values; jump to it. Assume all values are 32-bit
71 * aligned. Use an inline PIC version of memcpy()
72 * pre-relocation; strong alignment assumptions.
74 dla $t0, __boot2_base_vaddr__ /* Dst. */
75 dla $t2, __boot_loader_len__ /* Len. */
78 beq $t2, 0, memcopy_done
90 * We can now jump into the relocated code, running from
91 * cached DRAM rather than uncached flash. Note that a
92 * relative branch instruction cannot be used.
94 dla $at, relocated_start
103 .end prerelocate_start