start.S (5443B) - Raw
1 /* Startup code compliant to the ELF Mips ABI. 2 Copyright (C) 1995-2025 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 <https://www.gnu.org/licenses/>. */ 35 36 #define __ASSEMBLY__ 1 37 #include <entry.h> 38 #include <sgidefs.h> 39 #include <sys/asm.h> 40 41 #ifndef ENTRY_POINT 42 #error ENTRY_POINT needs to be defined for start.S on MIPS/ELF. 43 #endif 44 45 /* This is the canonical entry point, usually the first thing in the text 46 segment. The SVR4/Mips ABI (pages 3-31, 3-32) says that when the entry 47 point runs, most registers' values are unspecified, except for: 48 49 v0 ($2) Contains a function pointer to be registered with `atexit'. 50 This is how the dynamic linker arranges to have DT_FINI 51 functions called for shared libraries that have been loaded 52 before this code runs. 53 54 sp ($29) The stack contains the arguments and environment: 55 0(%esp) argc 56 4(%esp) argv[0] 57 ... 58 (4*argc)(%esp) NULL 59 (4*(argc+1))(%esp) envp[0] 60 ... 61 NULL 62 ra ($31) The return address register is set to zero so that programs 63 that search backward through stack frames recognize the last 64 stack frame. 65 */ 66 67 68 /* We need to call: 69 __libc_start_main (int (*main) (int, char **, char **), int argc, 70 char **argv, void (*init) (void), void (*fini) (void), 71 void (*rtld_fini) (void), void *stack_end) 72 */ 73 74 .text 75 .globl ENTRY_POINT 76 .type ENTRY_POINT,@function 77 #ifndef __mips16 78 ENTRY_POINT: 79 # ifdef __PIC__ 80 SETUP_GPX($0) 81 SETUP_GPX64($25,$0) 82 # else 83 PTR_LA $28, _gp /* Setup GP correctly if we're non-PIC. */ 84 move $31, $0 85 # endif 86 87 PTR_LA $4, main /* main */ 88 PTR_L $5, 0($29) /* argc */ 89 PTR_ADDIU $6, $29, PTRSIZE /* argv */ 90 91 /* Allocate space on the stack for seven arguments (o32 only) 92 and make sure the stack is aligned to double words (8 bytes) 93 on o32 and quad words (16 bytes) on n32 and n64. */ 94 95 and $29, -2 * SZREG 96 # if _MIPS_SIM == _ABIO32 97 PTR_SUBIU $29, 32 98 # endif 99 move $7, $0 /* Used to be init. */ 100 # if _MIPS_SIM == _ABIO32 101 PTR_S $0, 16($29) /* Used to be fini. */ 102 PTR_S $2, 20($29) /* rtld_fini */ 103 PTR_S $29, 24($29) /* stack_end */ 104 # else 105 move $8, $0 /* Used to be fini. */ 106 move $9, $2 /* rtld_fini */ 107 move $10, $29 /* stack_end */ 108 # endif 109 PTR_LA $25, __libc_start_main 110 jalr $25 111 hlt: b hlt /* Crash if somehow it does return. */ 112 113 #elif _MIPS_SIM == _ABIO32 /* __mips16 */ 114 /* MIPS16 entry point. */ 115 .set mips16 116 ENTRY_POINT: 117 # ifdef __PIC__ 118 li $3, %hi(_gp_disp) 119 addiu $4, $pc, %lo(_gp_disp) 120 sll $3, 16 121 addu $3, $4 122 move $gp, $3 123 # else 124 li $3, %hi(_gp) 125 sll $3, 16 126 addiu $3, %lo(_gp) 127 move $gp, $3 128 # endif 129 /* Tie end of stack frames. */ 130 li $4, 0 131 move $31, $4 132 /* Create new SP value in $7, including alignment. */ 133 li $4, 2 * SZREG 134 neg $4, $4 135 move $7, $sp 136 and $7, $4 137 addiu $7, -32 138 /* Load arguments with original SP. */ 139 lw $5, 0($sp) 140 addiu $6, $sp, PTRSIZE 141 /* Update SP. */ 142 move $sp, $7 143 /* Lay out last arguments, and call __libc_start_main(). */ 144 # ifdef __PIC__ 145 sw $7, 24($sp) /* stack_end */ 146 move $4, $0 /* Used to be ini. */ 147 sw $0, 16($sp) /* Used to be fini. */ 148 lw $4, %got(main)($3) /* main */ 149 lw $3, %call16(__libc_start_main)($3) 150 sw $2, 20($sp) /* rtld_fini */ 151 move $25, $3 152 jalr $3 153 # else 154 sw $7, 24($sp) /* stack_end */ 155 move $7, $0 /* Used to be init. */ 156 sw $0, 16($sp) /* Used to be fini. */ 157 lw $4, 3f /* main */ 158 sw $2, 20($sp) /* rtld_fini */ 159 /* Load and call __libc_start_main(). */ 160 lw $3, 4f 161 jalr $3 162 # endif 163 hlt: b hlt /* Crash if somehow it does return. */ 164 # ifndef __PIC__ 165 .align 2 166 3: .word main 167 4: .word __libc_start_main 168 # endif 169 170 #else /* __mips16 && _MIPS_SIM != _ABIO32 */ 171 # error "MIPS16 support for N32/N64 not implemented" 172 173 #endif /* __mips16 */ 174 175 /* Define a symbol for the first piece of initialized data. */ 176 .data 177 .globl __data_start 178 __data_start: 179 .long 0 180 .weak data_start 181 data_start = __data_start