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+/* Startup code compliant to the ELF x86-64 ABI.
+ Copyright (C) 2001-2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Andreas Jaeger <aj@suse.de>, 2001.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ In addition to the permissions in the GNU Lesser General Public
+ License, the Free Software Foundation gives you unlimited
+ permission to link the compiled version of this file with other
+ programs, and to distribute those programs without any restriction
+ coming from the use of this file. (The GNU Lesser General Public
+ License restrictions do apply in other respects; for example, they
+ cover modification of the file, and distribution when not linked
+ into another program.)
+
+ Note that people who make modified versions of this file are not
+ obligated to grant this special exception for their modified
+ versions; it is their choice whether to do so. The GNU Lesser
+ General Public License gives permission to release a modified
+ version without this exception; this exception also makes it
+ possible to release a modified version which carries forward this
+ exception.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* This is the canonical entry point, usually the first thing in the text
+ segment. The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
+ point runs, most registers' values are unspecified, except for:
+
+ %rdx Contains a function pointer to be registered with `atexit'.
+ This is how the dynamic linker arranges to have DT_FINI
+ functions called for shared libraries that have been loaded
+ before this code runs.
+
+ %rsp The stack contains the arguments and environment:
+ 0(%rsp) argc
+ 8(%rsp) argv[0]
+ ...
+ (8*argc)(%rsp) NULL
+ (8*(argc+1))(%rsp) envp[0]
+ ...
+ NULL
+*/
+
+#include <sysdep.h>
+#include "bp-sym.h"
+
+ .text
+ .globl _start
+ .type _start,@function
+_start:
+ cfi_startproc
+ /* Clearing frame pointer is insufficient, use CFI. */
+ cfi_undefined (rip)
+ /* Clear the frame pointer. The ABI suggests this be done, to mark
+ the outermost frame obviously. */
+ xorl %ebp, %ebp
+
+ /* Extract the arguments as encoded on the stack and set up
+ the arguments for __libc_start_main (int (*main) (int, char **, char **),
+ int argc, char *argv,
+ void (*init) (void), void (*fini) (void),
+ void (*rtld_fini) (void), void *stack_end).
+ The arguments are passed via registers and on the stack:
+ main: %rdi
+ argc: %rsi
+ argv: %rdx
+ init: %rcx
+ fini: %r8
+ rtld_fini: %r9
+ stack_end: stack. */
+
+ movq %rdx, %r9 /* Address of the shared library termination
+ function. */
+ popq %rsi /* Pop the argument count. */
+ movq %rsp, %rdx /* argv starts just at the current stack top. */
+ /* Align the stack to a 16 byte boundary to follow the ABI. */
+ andq $~15, %rsp
+
+ pushq %rax /* Push garbage because we push 8 more bytes. */
+
+ /* Provide the highest stack address to the user code (for stacks
+ which grow downwards). */
+ pushq %rsp
+
+#ifdef SHARED
+ /* Pass address of our own entry points to .fini and .init. */
+ movq __libc_csu_fini@GOTPCREL(%rip), %r8
+ movq __libc_csu_init@GOTPCREL(%rip), %rcx
+
+ movq BP_SYM (main)@GOTPCREL(%rip), %rdi
+
+ /* Call the user's main function, and exit with its value.
+ But let the libc call main. */
+ call BP_SYM (__libc_start_main)@PLT
+#else
+ /* Pass address of our own entry points to .fini and .init. */
+ movq $__libc_csu_fini, %r8
+ movq $__libc_csu_init, %rcx
+
+ movq $BP_SYM (main), %rdi
+
+ /* Call the user's main function, and exit with its value.
+ But let the libc call main. */
+ call BP_SYM (__libc_start_main)
+#endif
+
+ hlt /* Crash if somehow `exit' does return. */
+ cfi_endproc
+
+/* Define a symbol for the first piece of initialized data. */
+ .data
+ .globl __data_start
+__data_start:
+ .long 0
+ .weak data_start
+ data_start = __data_start