srt0.S revision 1.1.124.1
1 /* $NetBSD: srt0.S,v 1.1.124.1 2008/05/18 12:32:30 yamt Exp $ */ 2 3 /*- 4 * Copyright (c) 2002 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Steve C. Woodford. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <machine/asm.h> 33 #include <machine/psl.h> 34 #include <powerpc/spr.h> 35 36 #define STACK_SIZE 8192 37 38 /* 39 * The main entry point when loaded by PPC-Bug. 40 * 41 * There are two possible entry conditions here: 42 * 43 * 1) We were booted in `PReP' mode, either from disk or the network. 44 * In this case, we have no control over the load address so we 45 * have to relocate ourselves to the appropriate place. 46 * The firmware passes us the following registers: 47 * 48 * r1 -> Temporary stack 49 * r3 -> Residual Data 50 * r4 -> The address we were loaded to 51 * r5 -> Zero 52 * 53 * 2) We were booted over the network in Non-PReP mode. In this case, 54 * the load address is usually set using PPC-Bug's "niot" command, 55 * but we won't depend on it so relocation may be required. The 56 * firmware passes us the following registers: 57 * 58 * r1 -> Temporary stack 59 * r3 -> CLUN of the network device we booted from 60 * r4 -> DLUN of the network device we booted from 61 * r5 -> Non-zero 62 * r6 -> Base address of network device 63 * r7 -> Execution address of loaded program 64 * r8 -> Address of IP-address data structure 65 * r9 -> Pointer to start of filename string 66 * r10 -> Pointer to end+1 of filename string 67 * r11 -> Pointer to start of argument string 68 * r12 -> Pointer to end+1 of argument string 69 * 70 * The obvious way to distinguish between the two boot modes is by 71 * checking the value of r5. 72 */ 73 ENTRY(_start) 74 bl 1f 75 1: xor r0,r0,r0 76 77 /* First, switch off Instruction and Data caches. */ 78 mfspr r13,SPR_HID0 79 LDCONST(r14, HID0_DCE|HID0_ICE) 80 andc r13,r13,r14 81 sync 82 mtspr SPR_HID0,r13 83 84 85 /* 86 * All registers now available. Let's see if we need to relocate 87 */ 88 LDCONST(r13,_C_LABEL(_start)) /* Where we'd like to be */ 89 LDCONST(r14,_C_LABEL(edata)) /* End of data section */ 90 LDCONST(r15,0x3) 91 add r14,r14,r15 92 andc r14,r14,r15 /* Rounded up to the nearest 32-bits */ 93 sub r15,r14,r13 /* Our size, in bytes */ 94 mflr r16 /* Get address we were loaded to */ 95 subi r16,r16,0x4 /* Correct for branch */ 96 cmp cr0,r13,r16 /* Do we need to relocate? */ 97 beq _ASM_LABEL(clrbss) /* No relocation necessary */ 98 li r17,0x4 99 bgt 1f /* Relocate using forward copy? */ 100 101 /* Nope. Need to copy in reverse in case of overlap */ 102 mr r13,r14 /* dest -> end */ 103 add r16,r16,r15 /* src + size */ 104 subi r17,r17,0x8 /* Increment is -4 */ 105 106 /* 107 * Do the relocation 108 * r13 -> dest 109 * r15 -> number of bytes 110 * r16 -> src 111 * r17 -> Increment (+4 or -4) 112 */ 113 1: srwi r15,r15,0x2 /* Convert length to 32-bit words */ 114 mtctr r15 /* Save in counter register */ 115 116 2: lwz r15,0(r16) 117 stw r15,0(r13) 118 add r16,r16,r17 119 add r13,r13,r17 120 bdnz 2b 121 122 /* Now do an absolute jump to the relocated code */ 123 LDCONST(r13,_ASM_LABEL(clrbss)) 124 mtlr r13 125 blr 126 127 ASENTRY(clrbss) 128 LDCONST(r13,_C_LABEL(edata)) /* End of the data section */ 129 LDCONST(r14,_C_LABEL(end)) /* End of BSS */ 130 LDCONST(r15,0x3) 131 add r14,r14,r15 132 andc r14,r14,r15 /* Round-up end of BSS to 32-bits */ 133 sub r15,r14,r13 /* r15 == length of BSS */ 134 srwi r15,r15,0x2 135 mtctr r15 /* CTR == # of 32-bit words in BSS */ 136 1: stw r0,0(r13) /* Clear BSS */ 137 addi r13,r13,4 138 bdnz 1b 139 140 /* Fix up our own stack */ 141 LDCONST(r1,stack) 142 addi r1,r1,STACK_SIZE-0x10 143 LDCONST(r13,0x0f) 144 andc r1,r1,r13 145 146 /* 147 * Copy the arguments passed in from Bug into bug_bootinfo 148 * 149 * See bugsyscalls.h for details. 150 */ 151 LDCONST(r13,_C_LABEL(bug_bootinfo)) 152 stw r5,0x00(r13) 153 stw r3,0x04(r13) 154 stw r4,0x08(r13) 155 stw r6,0x0c(r13) 156 stw r7,0x10(r13) 157 stw r8,0x14(r13) 158 stw r9,0x18(r13) 159 stw r10,0x1c(r13) 160 stw r11,0x20(r13) 161 stw r12,0x24(r13) 162 163 mr r3,r13 164 bl _C_LABEL(main) /* void main(void) */ 165 /* FALLTHROUGH */ 166 167 /* 168 * Return to the debugger, either because main() returned or via panic(). 169 */ 170 ENTRY(_rtt) 171 addi r10,0,0x0063 172 sc 173 1: nop 174 b 1b 175 176 /* 177 * C code runs on this stack. 178 */ 179 .comm stack,STACK_SIZE,4 180 .comm errno,4,4 181 .comm debug,4,4 182
Indexes created Wed Oct 29 03:09:52 GMT 2025