1 /* Startup code compliant to the ELF s390 ABI.
2 Copyright (C) 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
3 Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
4 This file is part of the GNU C Library.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 In addition to the permissions in the GNU Lesser General Public
12 License, the Free Software Foundation gives you unlimited
13 permission to link the compiled version of this file with other
14 programs, and to distribute those programs without any restriction
15 coming from the use of this file. (The GNU Lesser General Public
16 License restrictions do apply in other respects; for example, they
17 cover modification of the file, and distribution when not linked
18 into another program.)
20 Note that people who make modified versions of this file are not
21 obligated to grant this special exception for their modified
22 versions; it is their choice whether to do so. The GNU Lesser
23 General Public License gives permission to release a modified
24 version without this exception; this exception also makes it
25 possible to release a modified version which carries forward this
28 The GNU C Library is distributed in the hope that it will be useful,
29 but WITHOUT ANY WARRANTY; without even the implied warranty of
30 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
31 Lesser General Public License for more details.
33 You should have received a copy of the GNU Lesser General Public
34 License along with the GNU C Library; if not, write to the Free
35 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
39 This is the canonical entry point, usually the first thing in the text
40 segment. Most registers' values are unspecified, except for:
42 %r14 Contains a function pointer to be registered with `atexit'.
43 This is how the dynamic linker arranges to have DT_FINI
44 functions called for shared libraries that have been loaded
45 before this code runs.
47 %r15 The stack contains the arguments and environment:
52 (4*(argc+1))(%r15) envp[0]
59 .type _start,@function
61 /* Setup pointer to literal pool of _start */
63 .L0: ahi %r13,.Llit-.L0
65 /* load argc and argv from stack */
66 la %r4,4(%r15) # get argv
67 l %r3,0(%r15) # get argc
69 /* align the stack to a double word boundary */
73 /* Setup a stack frame and a parameter area */
74 ahi %r15,-104 # make room on stack
75 xc 0(4,%r15),0(%r15) # clear back-chain
77 /* set up arguments for __libc_start_main:
78 main, argc, argv, envp, _init, _fini, rtld_fini, stack_end
79 Note that envp will be determined later in __libc_start_main
81 stm %r14,%r15,96(%r15) # store rtld_fini/stack_end to parameter area
83 l %r6,.L2-.Llit(%r13) # load pointer to __libc_csu_fini
84 l %r5,.L1-.Llit(%r13) # load pointer to __libc_csu_init
85 l %r2,.L3-.Llit(%r13) # load pointer to main
86 l %r1,.L4-.Llit(%r13) # load pointer to __libc_start_main
88 l %r12,.L5-.Llit(%r13) # load .got pointer
96 /* ok, now branch to the libc main routine */
99 /* crash if __libc_start_main returns */
104 .L1: .long __libc_csu_init
105 .L2: .long __libc_csu_fini
107 .L4: .long __libc_start_main
109 .L1: .long __libc_csu_init-.Llit
110 .L2: .long __libc_csu_fini-.Llit
111 .L3: .long main-.Llit
112 .L4: .long __libc_start_main@plt-.Llit
113 .L5: .long _GLOBAL_OFFSET_TABLE_-.Llit
116 /* Define a symbol for the first piece of initialized data. */
122 data_start = __data_start