1 /* Startup code compliant to the ELF Mips ABI.
2 Copyright (C) 1995-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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.
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.)
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
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.
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/>. */
36 #define __ASSEMBLY__ 1
42 #error ENTRY_POINT needs to be defined for start.S on MIPS/ELF.
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:
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.
54 sp ($29) The stack contains the arguments and environment:
59 (4*(argc+1))(%esp) envp[0]
62 ra ($31) The return address register is set to zero so that programs
63 that search backword through stack frames recognize the last
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)
76 .type ENTRY_POINT,@function
83 PTR_LA $28, _gp /* Setup GP correctly if we're non-PIC. */
87 PTR_LA $4, main /* main */
88 PTR_L $5, 0($29) /* argc */
89 PTR_ADDIU $6, $29, PTRSIZE /* argv */
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. */
96 # if _MIPS_SIM == _ABIO32
99 PTR_LA $7, __libc_csu_init /* init */
100 PTR_LA $8, __libc_csu_fini
101 # if _MIPS_SIM == _ABIO32
102 PTR_S $8, 16($29) /* fini */
103 PTR_S $2, 20($29) /* rtld_fini */
104 PTR_S $29, 24($29) /* stack_end */
106 move $9, $2 /* rtld_fini */
107 move $10, $29 /* stack_end */
109 PTR_LA $25, __libc_start_main
111 hlt: b hlt /* Crash if somehow it does return. */
113 #elif _MIPS_SIM == _ABIO32 /* __mips16 */
114 /* MIPS16 entry point. */
119 addiu $4, $pc, %lo(_gp_disp)
129 /* Tie end of stack frames. */
132 /* Create new SP value in $7, including alignment. */
138 /* Load arguments with original SP. */
140 addiu $6, $sp, PTRSIZE
143 /* Lay out last arguments, and call __libc_start_main(). */
145 sw $7, 24($sp) /* stack_end */
146 lw $4, %got(__libc_csu_fini)($3)
147 lw $7, %got(__libc_csu_init)($3) /* init */
148 sw $4, 16($sp) /* fini */
149 lw $4, %got(main)($3) /* main */
150 lw $3, %call16(__libc_start_main)($3)
151 sw $2, 20($sp) /* rtld_fini */
156 sw $7, 24($sp) /* stack_end */
158 sw $4, 16($sp) /* fini */
160 sw $2, 20($sp) /* rtld_fini */
161 /* Load and call __libc_start_main(). */
165 hlt: b hlt /* Crash if somehow it does return. */
168 1: .word __libc_csu_fini
169 2: .word __libc_csu_init
171 4: .word __libc_start_main
174 #else /* __mips16 && _MIPS_SIM != _ABIO32 */
175 # error "MIPS16 support for N32/N64 not implemented"
177 #endif /* __mips16 */
179 /* Define a symbol for the first piece of initialized data. */
185 data_start = __data_start