Root/
| 1 | // Iris: micro-kernel for a capability-based operating system. |
| 2 | // mips/start.S: kernel starter at high address. |
| 3 | // Copyright 2009 Bas Wijnen <wijnen@debian.org> |
| 4 | // |
| 5 | // This program is free software: you can redistribute it and/or modify |
| 6 | // it under the terms of the GNU General Public License as published by |
| 7 | // the Free Software Foundation, either version 3 of the License, or |
| 8 | // (at your option) any later version. |
| 9 | // |
| 10 | // This program is distributed in the hope that it will be useful, |
| 11 | // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | // GNU General Public License for more details. |
| 14 | // |
| 15 | // You should have received a copy of the GNU General Public License |
| 16 | // along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 17 | |
| 18 | // This program is a wrapper around the kernel. |
| 19 | // It is position-independant and may be loaded anywhere. |
| 20 | // It does not use gp. This means that li and la must not be used. |
| 21 | .globl __start |
| 22 | .set noreorder |
| 23 | |
| 24 | __start: |
| 25 | // Set t0 to uart0 txd |
| 26 | lui $t0, 0xb003 |
| 27 | |
| 28 | bal 1f |
| 29 | // For some reason the disassembler considers everything |
| 30 | // after __start non-code until the next label. So I add a label. |
| 31 | start_hack_for_disassembler: |
| 32 | lui $a0, 0x8000 |
| 33 | base: |
| 34 | .word image_end - image |
| 35 | 1: |
| 36 | // Set kseg0 to uncachable. |
| 37 | ori $t0, $zero, 2 |
| 38 | mtc0 $t0, $16, 0 |
| 39 | |
| 40 | // Flush cache. |
| 41 | lui $v1, 0x8000 |
| 42 | ori $v0, $v1, 0x8000 |
| 43 | 1: |
| 44 | // i-cache index invalidate. |
| 45 | cache 0, 0($v1) |
| 46 | // d-cache index write-back invalidate. |
| 47 | cache 1, 0($v1) |
| 48 | bne $v1, $v0, 1b |
| 49 | addiu $v1, $v1, 32 |
| 50 | |
| 51 | // Set a1 to start address of image. |
| 52 | addiu $a1, $ra, image - base + ADDR0 - 0x80000000 |
| 53 | |
| 54 | // Set a2 to end address of image. |
| 55 | lw $a2, 0($ra) |
| 56 | add $a2, $a2, $a1 |
| 57 | |
| 58 | // Set t9 to the entry point. |
| 59 | lui $t9, START >> 16 |
| 60 | ori $t9, $t9, START & 0xffff |
| 61 | |
| 62 | // Put the copying code at the end, to prevent overwriting itself. |
| 63 | // The copy goes to the start of RAM, so the target is never larger than the source. |
| 64 | jr $a2 |
| 65 | nop |
| 66 | |
| 67 | image: |
| 68 | .incbin "iris.raw" |
| 69 | image_end: |
| 70 | // Copy the image to the start of RAM. |
| 71 | // a0 is the destination: 0x80000000, counting up. |
| 72 | // a1 is the start of the image, counting up. |
| 73 | // a2 is the end of the image, not changing. |
| 74 | // a3 is the working register to do the move. |
| 75 | 1: lw $a3, 0($a1) |
| 76 | addiu $a1, $a1, 4 |
| 77 | sw $a3, 0($a0) |
| 78 | bne $a1, $a2, 1b |
| 79 | addiu $a0, $a0, 4 |
| 80 | // Done copying. |
| 81 | |
| 82 | // Make the jump to the new code. |
| 83 | jr $t9 |
| 84 | nop |
| 85 |
Branches:
master
