1 /* Startup code compliant to the ELF Xtensa ABI.
2 Copyright (C) 2001, 2007 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 <http://www.gnu.org/licenses/>. */
38 #ifndef __UCLIBC_CTOR_DTOR__
43 /* This is the canonical entry point, usually the first thing in the text
44 segment. When the entry point runs, most register values are unspecified,
47 a2 Contains a function pointer to be registered with `atexit'.
48 This is how the dynamic linker arranges to have DT_FINI
49 functions called for shared libraries that have been loaded
50 before this code runs.
52 a1 The stack (i.e., a1+16) contains the arguments and environment:
57 a1+(4*(argc+1)) envp[0]
61 Setup parameters accordingly (for a call4). See function prototype
62 from sysdeps/generic/libc-start.c
77 .type _start, @function
87 #if defined(__XTENSA_WINDOWED_ABI__)
92 movi a4, reloc_static_pie
96 /* Clear a0 to obviously mark the outermost frame. */
100 /* Load up the user's main function. */
103 /* Extract the arguments as encoded on the stack and set up
104 the arguments for `main': argc, argv. envp will be determined
105 later in __uClibc_main. */
106 l32i a7, a1, 0 /* Load the argument count. */
107 addi a8, a1, 4 /* Compute the argv pointer. */
109 /* Push address of our own entry points to .fini and .init. */
113 /* Setup the shared library termination function. */
116 /* Provide the highest stack address to the user code (for stacks
117 which grow downwards). Note that we destroy the stack version
121 /* Call the user's main function, and exit with its value.
122 But let the libc call main. */
123 movi a4, __uClibc_main
125 #elif defined(__XTENSA_CALL0_ABI__)
130 movi a0, reloc_static_pie
135 /* Setup the shared library termination function. */
139 /* Load up the user's main function. */
142 /* Extract the arguments as encoded on the stack and set up
143 the arguments for `main': argc, argv. envp will be determined
144 later in __uClibc_main. */
145 l32i a3, a1, 0 /* Load the argument count. */
146 addi a4, a1, 4 /* Compute the argv pointer. */
148 /* Push address of our own entry points to .fini and .init. */
152 /* Provide the highest stack address to the user code (for stacks
153 which grow downwards). Note that we destroy the stack version
157 /* Call the user's main function, and exit with its value.
158 But let the libc call main. */
159 movi a0, __uClibc_main
162 #error Unsupported Xtensa ABI
165 /* Crash if somehow `exit' does return. */
168 /* Define a symbol for the first piece of initialized data. */
175 data_start = __data_start