1/* start, OpenRISC version.
2 Copyright (C) 2022-2024 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/* This is the canonical entry point, usually the first thing in the text
37 segment.
38
39 sp The stack contains the arguments and environment:
40 0(sp) argc
41 4(sp) argv[0]
42 ...
43 (4*argc)(sp) NULL
44 (4*(argc+1))(sp) envp[0]
45 ...
46 NULL
47 */
48
49#define __ASSEMBLY__
50#include <sysdep.h>
51#include <entry.h>
52
53ENTRY (ENTRY_POINT)
54
55 /* Setup Arguments to the __libc_start_main function. */
56
57 /* Take values for argc and argv off the stack.
58 These will be passed as arguments two and three to main
59 and thus go in registers r4 and r5, respectively. */
60 l.lwz r4, 0(r1)
61 l.addi r5, r1, 4
62
63 /* Pass in rtld_fini from dl-start.S. */
64 l.or r8, r3, r3
65
66#ifdef PIC
67 /* Obtain a pointer to .got in r16 */
68 l.jal 0x8
69 l.movhi r16, gotpchi(_GLOBAL_OFFSET_TABLE_-4)
70 l.ori r16, r16, gotpclo(_GLOBAL_OFFSET_TABLE_+0)
71 l.add r16, r16, r9
72
73 /* Pass in the the main symbol. */
74 l.lwz r3, got(main)(r16)
75#else
76 /* Pass in the the main symbol. */
77 l.movhi r3, hi(main)
78 l.ori r3, r3, lo(main)
79#endif
80 /* Used to be init and fini. */
81 l.movhi r6, 0x0
82 l.movhi r7, 0x0
83
84 /* Push stack limit onto the stack.
85 This provides the highest stack address to user code (as stack grows
86 downwards.
87 This is the seventh argument to __libc_start_main and thus needs to
88 be passed on the stack. */
89 l.sw -4(r1), r1
90
91 /* Adjust stack to account for a total of 7 args (i.e. the last one is
92 on the stack. */
93 l.addi r1, r1, -4
94
95 /* Clear the frame pointer and link register since this is the
96 outermost frame. */
97 l.movhi r2, 0x0
98 l.movhi r9, 0x0
99
100 /* Let the libc call main and exit with its return code. */
101#ifdef PIC
102 l.j plt(__libc_start_main)
103#else
104 l.j __libc_start_main
105#endif
106 l.nop
107END (ENTRY_POINT)
108
109 /* Define a symbol for the first piece of initialized data. */
110 .data
111 .globl __data_start
112__data_start:
113 .long 0
114 .weak data_start
115 data_start = __data_start
116

source code of glibc/sysdeps/or1k/start.S