| xf.li | bdd93d5 | 2023-05-12 07:10:14 -0700 | [diff] [blame^] | 1 | /* Startup code for Nios II |
| 2 | Copyright (C) 1995-2016 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | In addition to the permissions in the GNU Lesser General Public |
| 11 | License, the Free Software Foundation gives you unlimited |
| 12 | permission to link the compiled version of this file with other |
| 13 | programs, and to distribute those programs without any restriction |
| 14 | coming from the use of this file. (The GNU Lesser General Public |
| 15 | License restrictions do apply in other respects; for example, they |
| 16 | cover modification of the file, and distribution when not linked |
| 17 | into another program.) |
| 18 | |
| 19 | Note that people who make modified versions of this file are not |
| 20 | obligated to grant this special exception for their modified |
| 21 | versions; it is their choice whether to do so. The GNU Lesser |
| 22 | General Public License gives permission to release a modified |
| 23 | version without this exception; this exception also makes it |
| 24 | possible to release a modified version which carries forward this |
| 25 | exception. |
| 26 | |
| 27 | The GNU C Library is distributed in the hope that it will be useful, |
| 28 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 29 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 30 | Lesser General Public License for more details. |
| 31 | |
| 32 | You should have received a copy of the GNU Lesser General Public |
| 33 | License along with the GNU C Library. If not, see |
| 34 | <http://www.gnu.org/licenses/>. */ |
| 35 | |
| 36 | /* This is the canonical entry point, usually the first thing in the text |
| 37 | segment. |
| 38 | |
| 39 | Note that the code in the .init section has already been run. |
| 40 | This includes _init and _libc_init |
| 41 | |
| 42 | The stack pointer, sp, will point to the argument count on the stack. |
| 43 | The initial state of the stack when a userspace process is started is: |
| 44 | |
| 45 | Purpose Start Address Length |
| 46 | Unspecified High Addresses |
| 47 | Referenced strings, etc. Varies |
| 48 | Unspecified |
| 49 | Null auxilliary vector entry 4bytes |
| 50 | Auxilliary vector entries 8bytes each |
| 51 | NULL terminator for envp 4bytes |
| 52 | Environment pointers sp+8+4*argc 4bytes each |
| 53 | NULL terminator for argv sp+4+4*argc 4bytes |
| 54 | Argument pointers sp+4 4bytes each |
| 55 | Argument count sp 4bytes |
| 56 | Unspecified Low Addresses |
| 57 | |
| 58 | If the application should register a destructor function with atexit, |
| 59 | the pointer will be placed in r4. Otherwise r4 will be zero. |
| 60 | |
| 61 | The contents of all other registers are unspecified. User code should |
| 62 | set fp to zero to mark the end of the frame chain. |
| 63 | |
| 64 | The auxilliary vector is a series of pairs of 32-bit tag and 32-bit |
| 65 | value, terminated by an AT_NULL tag. |
| 66 | */ |
| 67 | |
| 68 | .text |
| 69 | .globl _start |
| 70 | .type _start,%function |
| 71 | _start: |
| 72 | /* Set up the global pointer. */ |
| 73 | movhi gp, %hiadj(_gp) |
| 74 | addi gp, gp, %lo(_gp) |
| 75 | |
| 76 | /* Save the stack pointer. */ |
| 77 | mov r2, sp |
| 78 | |
| 79 | /* Create room on the stack for the fini, rtld_fini and stack_end args |
| 80 | to __libc_start_main. */ |
| 81 | subi sp, sp, 12 |
| 82 | |
| 83 | /* Push stack_end */ |
| 84 | stw r2, 8(sp) |
| 85 | |
| 86 | /* Push rtld_fini */ |
| 87 | stw r4, 4(sp) |
| 88 | |
| 89 | /* Set up the GOT pointer. */ |
| 90 | nextpc r22 |
| 91 | 1: movhi r2, %hiadj(_gp_got - 1b) |
| 92 | addi r2, r2, %lo(_gp_got - 1b) |
| 93 | add r22, r22, r2 |
| 94 | |
| 95 | /* Push fini */ |
| 96 | movhi r8, %call_hiadj(__libc_csu_fini) |
| 97 | addi r8, r8, %call_lo(__libc_csu_fini) |
| 98 | add r8, r8, r22 |
| 99 | ldw r8, 0(r8) |
| 100 | stw r8, 0(sp) |
| 101 | |
| 102 | /* r7 == init */ |
| 103 | movhi r7, %call_hiadj(__libc_csu_init) |
| 104 | addi r7, r7, %call_lo(__libc_csu_init) |
| 105 | add r7, r7, r22 |
| 106 | ldw r7, 0(r7) |
| 107 | |
| 108 | /* r6 == argv */ |
| 109 | addi r6, sp, 16 |
| 110 | |
| 111 | /* r5 == argc */ |
| 112 | ldw r5, 12(sp) |
| 113 | |
| 114 | /* r4 == main */ |
| 115 | movhi r4, %call_hiadj(main) |
| 116 | addi r4, r4, %call_lo(main) |
| 117 | add r4, r4, r22 |
| 118 | ldw r4, 0(r4) |
| 119 | |
| 120 | /* fp == 0 */ |
| 121 | mov fp, zero |
| 122 | |
| 123 | /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, |
| 124 | stack_end) */ |
| 125 | |
| 126 | /* Let the libc call main and exit with its return code. */ |
| 127 | movhi r2, %call_hiadj(__libc_start_main) |
| 128 | addi r2, r2, %call_lo(__libc_start_main) |
| 129 | add r2, r2, r22 |
| 130 | ldw r2, 0(r2) |
| 131 | callr r2 |
| 132 | |
| 133 | /* should never get here....*/ |
| 134 | movhi r2, %call_hiadj(abort) |
| 135 | addi r2, r2, %call_lo(abort) |
| 136 | add r2, r2, r22 |
| 137 | ldw r2, 0(r2) |
| 138 | callr r2 |
| 139 | |
| 140 | /* Define a symbol for the first piece of initialized data. */ |
| 141 | .data |
| 142 | .globl __data_start |
| 143 | __data_start: |
| 144 | .long 0 |
| 145 | .weak data_start |
| 146 | data_start = __data_start |