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Diffstat (limited to 'sysdeps/nios2/start.S')
| -rw-r--r-- | sysdeps/nios2/start.S | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/sysdeps/nios2/start.S b/sysdeps/nios2/start.S new file mode 100644 index 0000000000..96cec96e24 --- /dev/null +++ b/sysdeps/nios2/start.S @@ -0,0 +1,146 @@ +/* Startup code for Nios II + Copyright (C) 1995-2015 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 |