/* Copyright (C) 2001-2021 Free Software Foundation, Inc. Contributed by Hans-Peter Nilsson This file is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. This file is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. Under Section 7 of GPL version 3, you are granted additional permissions described in the GCC Runtime Library Exception, version 3.1, as published by the Free Software Foundation. You should have received a copy of the GNU General Public License and a copy of the GCC Runtime Library Exception along with this program; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see . */ % This is the crt0 equivalent for mmix-knuth-mmixware, for setting up % things for compiler-generated assembly-code and for setting up things % between where the simulator calls and main, and shutting things down on % the way back. There's an actual crt0.o elsewhere, but that's a dummy. % This file and the GCC output are supposed to be *reasonably* % mmixal-compatible to enable people to re-use output with Knuth's mmixal. % However, forward references are used more freely: we are using the % binutils tools. Users of mmixal beware; you will sometimes have to % re-order things or use temporary variables. % Users of mmixal will want to set up 8H and 9H to be .text and .data % respectively, so the compiler can switch between them pretending they're % segments. % This little treasure (some contents) is required so the 32 lowest % address bits of user data will not be zero. Because of truncation, % that would cause testcase gcc.c-torture/execute/980701-1.c to % incorrectly fail. .data ! mmixal:= 8H LOC Data_Segment .p2align 3 dstart OCTA 2009 .text ! mmixal:= 9H LOC 8B; LOC #100 .global Main % The __Stack_start symbol is provided by the link script. stackpp OCTA __Stack_start crtstxt OCTA _init % Assumed to be the lowest executed address. OCTA __etext % Assumed to be beyond the highest executed address. crtsdat OCTA dstart % Assumed to be the lowest accessed address. OCTA _end % Assumed to be beyond the highest accessed address. % "Main" is the magic symbol the simulator jumps to. We want to go % on to "main". % We need to set rG explicitly to avoid hard-to-debug situations. Main SETL $255,32 PUT rG,$255 % Make sure we have valid memory for addresses in .text and .data (and % .bss, but we include this in .data), for the benefit of mmo-using % simulators that require validation of addresses for which contents % is not present. Due to its implicit-zero nature, zeros in contents % may be left out in the mmo format, but we don't know the boundaries % of those zero-chunks; for mmo files from binutils, they correspond % to the beginning and end of sections in objects before linking. We % validate the contents by executing PRELD (0; one byte) on each % 2048-byte-boundary of our .text .data, and we assume this size % matches the magic lowest-denominator chunk-size for all % validation-requiring simulators. The effect of the PRELD (any size) % is assumed to be the same as initial loading of the contents, as % long as the PRELD happens before the first PUSHJ/PUSHGO. If it % happens after that, we'll need to distinguish between % access-for-execution and read/write access. GETA $255,crtstxt LDOU $2,$255,0 ANDNL $2,#7ff % Align the start at a 2048-boundary. LDOU $3,$255,8 SETL $4,2048 0H PRELD 0,$2,0 ADDU $2,$2,$4 CMP $255,$2,$3 BN $255,0B GETA $255,crtsdat LDOU $2,$255,0 ANDNL $2,#7ff LDOU $3,$255,8 0H PRELD 0,$2,0 ADDU $2,$2,$4 CMP $255,$2,$3 BN $255,0B % Initialize the stack pointer. It is supposedly made a global % zero-initialized (allowed to change) register in crtn.S; we use the % explicit number. GETA $255,stackpp LDOU $254,$255,0 PUSHJ $2,_init #ifdef __MMIX_ABI_GNU__ % Copy argc and argv from their initial position to argument registers % where necessary. SET $231,$0 SET $232,$1 #else % For the mmixware ABI, we need to move arguments. The return value will % appear in $0. SET $2,$1 SET $1,$0 #endif PUSHJ $0,main JMP exit % Provide the first part of _init and _fini. Save the return address on the % register stack. We eventually ignore the return address of these % PUSHJ:s, so it doesn't matter that whether .init and .fini code calls % functions or where they store rJ. We shouldn't get there, so die % (TRAP Halt) if that happens. .section .init,"ax",@progbits .global _init _init: GET $0,:rJ PUSHJ $1,0F SETL $255,255 TRAP 0,0,0 0H IS @ % Register _fini to be executed as the last atexit function. #ifdef __MMIX_ABI_GNU__ GETA $231,_fini #else GETA $1,_fini #endif PUSHJ $0,atexit .section .fini,"ax",@progbits .global _fini _fini: GET $0,:rJ PUSHJ $1,0F SETL $255,255 TRAP 0,0,0 0H IS @