1/* Copyright (C) 2001-2021 Free Software Foundation, Inc. 2 Contributed by Hans-Peter Nilsson <hp@bitrange.com> 3 4This file is free software; you can redistribute it and/or modify it 5under the terms of the GNU General Public License as published by the 6Free Software Foundation; either version 3, or (at your option) any 7later version. 8 9This file is distributed in the hope that it will be useful, but 10WITHOUT ANY WARRANTY; without even the implied warranty of 11MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12General Public License for more details. 13 14Under Section 7 of GPL version 3, you are granted additional 15permissions described in the GCC Runtime Library Exception, version 163.1, as published by the Free Software Foundation. 17 18You should have received a copy of the GNU General Public License and 19a copy of the GCC Runtime Library Exception along with this program; 20see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 21<http://www.gnu.org/licenses/>. */ 22 23% This is the crt0 equivalent for mmix-knuth-mmixware, for setting up 24% things for compiler-generated assembly-code and for setting up things 25% between where the simulator calls and main, and shutting things down on 26% the way back. There's an actual crt0.o elsewhere, but that's a dummy. 27 28% This file and the GCC output are supposed to be *reasonably* 29% mmixal-compatible to enable people to re-use output with Knuth's mmixal. 30% However, forward references are used more freely: we are using the 31% binutils tools. Users of mmixal beware; you will sometimes have to 32% re-order things or use temporary variables. 33 34% Users of mmixal will want to set up 8H and 9H to be .text and .data 35% respectively, so the compiler can switch between them pretending they're 36% segments. 37 38% This little treasure (some contents) is required so the 32 lowest 39% address bits of user data will not be zero. Because of truncation, 40% that would cause testcase gcc.c-torture/execute/980701-1.c to 41% incorrectly fail. 42 43 .data ! mmixal:= 8H LOC Data_Segment 44 .p2align 3 45dstart OCTA 2009 46 47 .text ! mmixal:= 9H LOC 8B; LOC #100 48 .global Main 49 50% The __Stack_start symbol is provided by the link script. 51stackpp OCTA __Stack_start 52crtstxt OCTA _init % Assumed to be the lowest executed address. 53 OCTA __etext % Assumed to be beyond the highest executed address. 54 55crtsdat OCTA dstart % Assumed to be the lowest accessed address. 56 OCTA _end % Assumed to be beyond the highest accessed address. 57 58% "Main" is the magic symbol the simulator jumps to. We want to go 59% on to "main". 60% We need to set rG explicitly to avoid hard-to-debug situations. 61Main SETL $255,32 62 PUT rG,$255 63 64% Make sure we have valid memory for addresses in .text and .data (and 65% .bss, but we include this in .data), for the benefit of mmo-using 66% simulators that require validation of addresses for which contents 67% is not present. Due to its implicit-zero nature, zeros in contents 68% may be left out in the mmo format, but we don't know the boundaries 69% of those zero-chunks; for mmo files from binutils, they correspond 70% to the beginning and end of sections in objects before linking. We 71% validate the contents by executing PRELD (0; one byte) on each 72% 2048-byte-boundary of our .text .data, and we assume this size 73% matches the magic lowest-denominator chunk-size for all 74% validation-requiring simulators. The effect of the PRELD (any size) 75% is assumed to be the same as initial loading of the contents, as 76% long as the PRELD happens before the first PUSHJ/PUSHGO. If it 77% happens after that, we'll need to distinguish between 78% access-for-execution and read/write access. 79 80 GETA $255,crtstxt 81 LDOU $2,$255,0 82 ANDNL $2,#7ff % Align the start at a 2048-boundary. 83 LDOU $3,$255,8 84 SETL $4,2048 850H PRELD 0,$2,0 86 ADDU $2,$2,$4 87 CMP $255,$2,$3 88 BN $255,0B 89 90 GETA $255,crtsdat 91 LDOU $2,$255,0 92 ANDNL $2,#7ff 93 LDOU $3,$255,8 940H PRELD 0,$2,0 95 ADDU $2,$2,$4 96 CMP $255,$2,$3 97 BN $255,0B 98 99% Initialize the stack pointer. It is supposedly made a global 100% zero-initialized (allowed to change) register in crtn.S; we use the 101% explicit number. 102 GETA $255,stackpp 103 LDOU $254,$255,0 104 105 PUSHJ $2,_init 106 107#ifdef __MMIX_ABI_GNU__ 108% Copy argc and argv from their initial position to argument registers 109% where necessary. 110 SET $231,$0 111 SET $232,$1 112#else 113% For the mmixware ABI, we need to move arguments. The return value will 114% appear in $0. 115 SET $2,$1 116 SET $1,$0 117#endif 118 119 PUSHJ $0,main 120 JMP exit 121 122% Provide the first part of _init and _fini. Save the return address on the 123% register stack. We eventually ignore the return address of these 124% PUSHJ:s, so it doesn't matter that whether .init and .fini code calls 125% functions or where they store rJ. We shouldn't get there, so die 126% (TRAP Halt) if that happens. 127 128 .section .init,"ax",@progbits 129 .global _init 130_init: 131 GET $0,:rJ 132 PUSHJ $1,0F 133 SETL $255,255 134 TRAP 0,0,0 1350H IS @ 136 137% Register _fini to be executed as the last atexit function. 138#ifdef __MMIX_ABI_GNU__ 139 GETA $231,_fini 140#else 141 GETA $1,_fini 142#endif 143 PUSHJ $0,atexit 144 145 .section .fini,"ax",@progbits 146 .global _fini 147_fini: 148 GET $0,:rJ 149 PUSHJ $1,0F 150 SETL $255,255 151 TRAP 0,0,0 1520H IS @ 153