| /* Startup code for Nios II |
| Copyright (C) 1995-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| In addition to the permissions in the GNU Lesser General Public |
| License, the Free Software Foundation gives you unlimited |
| permission to link the compiled version of this file with other |
| programs, and to distribute those programs without any restriction |
| coming from the use of this file. (The GNU Lesser General Public |
| License restrictions do apply in other respects; for example, they |
| cover modification of the file, and distribution when not linked |
| into another program.) |
| |
| Note that people who make modified versions of this file are not |
| obligated to grant this special exception for their modified |
| versions; it is their choice whether to do so. The GNU Lesser |
| General Public License gives permission to release a modified |
| version without this exception; this exception also makes it |
| possible to release a modified version which carries forward this |
| exception. |
| |
| The GNU C Library 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 |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| /* This is the canonical entry point, usually the first thing in the text |
| segment. |
| |
| Note that the code in the .init section has already been run. |
| This includes _init and _libc_init |
| |
| The stack pointer, sp, will point to the argument count on the stack. |
| The initial state of the stack when a userspace process is started is: |
| |
| Purpose Start Address Length |
| Unspecified High Addresses |
| Referenced strings, etc. Varies |
| Unspecified |
| Null auxilliary vector entry 4bytes |
| Auxilliary vector entries 8bytes each |
| NULL terminator for envp 4bytes |
| Environment pointers sp+8+4*argc 4bytes each |
| NULL terminator for argv sp+4+4*argc 4bytes |
| Argument pointers sp+4 4bytes each |
| Argument count sp 4bytes |
| Unspecified Low Addresses |
| |
| If the application should register a destructor function with atexit, |
| the pointer will be placed in r4. Otherwise r4 will be zero. |
| |
| The contents of all other registers are unspecified. User code should |
| set fp to zero to mark the end of the frame chain. |
| |
| The auxilliary vector is a series of pairs of 32-bit tag and 32-bit |
| value, terminated by an AT_NULL tag. |
| */ |
| |
| .text |
| .globl _start |
| .type _start,%function |
| _start: |
| /* Set up the global pointer. */ |
| movhi gp, %hiadj(_gp) |
| addi gp, gp, %lo(_gp) |
| |
| /* Save the stack pointer. */ |
| mov r2, sp |
| |
| /* Create room on the stack for the fini, rtld_fini and stack_end args |
| to __libc_start_main. */ |
| subi sp, sp, 12 |
| |
| /* Push stack_end */ |
| stw r2, 8(sp) |
| |
| /* Push rtld_fini */ |
| stw r4, 4(sp) |
| |
| /* Set up the GOT pointer. */ |
| nextpc r22 |
| 1: movhi r2, %hiadj(_gp_got - 1b) |
| addi r2, r2, %lo(_gp_got - 1b) |
| add r22, r22, r2 |
| |
| /* Push fini */ |
| movhi r8, %call_hiadj(__libc_csu_fini) |
| addi r8, r8, %call_lo(__libc_csu_fini) |
| add r8, r8, r22 |
| ldw r8, 0(r8) |
| stw r8, 0(sp) |
| |
| /* r7 == init */ |
| movhi r7, %call_hiadj(__libc_csu_init) |
| addi r7, r7, %call_lo(__libc_csu_init) |
| add r7, r7, r22 |
| ldw r7, 0(r7) |
| |
| /* r6 == argv */ |
| addi r6, sp, 16 |
| |
| /* r5 == argc */ |
| ldw r5, 12(sp) |
| |
| /* r4 == main */ |
| movhi r4, %call_hiadj(main) |
| addi r4, r4, %call_lo(main) |
| add r4, r4, r22 |
| ldw r4, 0(r4) |
| |
| /* fp == 0 */ |
| mov fp, zero |
| |
| /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, |
| stack_end) */ |
| |
| /* Let the libc call main and exit with its return code. */ |
| movhi r2, %call_hiadj(__libc_start_main) |
| addi r2, r2, %call_lo(__libc_start_main) |
| add r2, r2, r22 |
| ldw r2, 0(r2) |
| callr r2 |
| |
| /* should never get here....*/ |
| movhi r2, %call_hiadj(abort) |
| addi r2, r2, %call_lo(abort) |
| add r2, r2, r22 |
| ldw r2, 0(r2) |
| callr r2 |
| |
| /* Define a symbol for the first piece of initialized data. */ |
| .data |
| .globl __data_start |
| __data_start: |
| .long 0 |
| .weak data_start |
| data_start = __data_start |
