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authorAndreas Jaeger <aj@suse.de>2012-03-27 21:35:36 +0200
committerAndreas Jaeger <aj@suse.de>2012-03-27 21:35:36 +0200
commit1e3cdfda7486316198ec0587a8aa96f50e88b3bc (patch)
tree4badfb248f3392b95be5b86d747c98331409dca7 /sysdeps/i386/start.S
parentc876e002a2484d53c797140c005f3630e6abec72 (diff)
parentd6373f9ce3972a1891e4d09479a98e0dbc7e3d73 (diff)
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Merge branch 'elf-move'
Conflicts:
	debug/backtracesymsfd.c
	sysdeps/generic/elf/backtracesymsfd.c
	sysdeps/i386/configure.in
Diffstat (limited to 'sysdeps/i386/start.S')
-rw-r--r--sysdeps/i386/start.S141
1 files changed, 141 insertions, 0 deletions
diff --git a/sysdeps/i386/start.S b/sysdeps/i386/start.S
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+/* Startup code compliant to the ELF i386 ABI.
+   Copyright (C) 1995-2012 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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:
+
+   %edx		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.
+
+   %esp		The stack contains the arguments and environment:
+		0(%esp)			argc
+		4(%esp)			argv[0]
+		...
+		(4*argc)(%esp)		NULL
+		(4*(argc+1))(%esp)	envp[0]
+		...
+					NULL
+*/
+
+#include "bp-sym.h"
+
+	.text
+	.globl _start
+	.type _start,@function
+_start:
+	/* 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 `main': argc, argv.  envp will be determined
+	   later in __libc_start_main.  */
+	popl %esi		/* Pop the argument count.  */
+	movl %esp, %ecx		/* argv starts just at the current stack top.*/
+
+	/* Before pushing the arguments align the stack to a 16-byte
+	(SSE needs 16-byte alignment) boundary to avoid penalties from
+	misaligned accesses.  Thanks to Edward Seidl <seidl@janed.com>
+	for pointing this out.  */
+	andl $0xfffffff0, %esp
+	pushl %eax		/* Push garbage because we allocate
+				   28 more bytes.  */
+
+	/* Provide the highest stack address to the user code (for stacks
+	   which grow downwards).  */
+	pushl %esp
+
+	pushl %edx		/* Push address of the shared library
+				   termination function.  */
+
+#ifdef SHARED
+	/* Load PIC register.  */
+	call 1f
+	addl $_GLOBAL_OFFSET_TABLE_, %ebx
+
+	/* Push address of our own entry points to .fini and .init.  */
+	leal __libc_csu_fini@GOTOFF(%ebx), %eax
+	pushl %eax
+	leal __libc_csu_init@GOTOFF(%ebx), %eax
+	pushl %eax
+
+	pushl %ecx		/* Push second argument: argv.  */
+	pushl %esi		/* Push first argument: argc.  */
+
+	pushl BP_SYM (main)@GOT(%ebx)
+
+	/* 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
+	/* Push address of our own entry points to .fini and .init.  */
+	pushl $__libc_csu_fini
+	pushl $__libc_csu_init
+
+	pushl %ecx		/* Push second argument: argv.  */
+	pushl %esi		/* Push first argument: argc.  */
+
+	pushl $BP_SYM (main)
+
+	/* 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.  */
+
+#ifdef SHARED
+1:	movl	(%esp), %ebx
+	ret
+#endif
+
+/* To fulfill the System V/i386 ABI we need this symbol.  Yuck, it's so
+   meaningless since we don't support machines < 80386.  */
+	.section .rodata
+	.globl _fp_hw
+_fp_hw:	.long 3
+	.size _fp_hw, 4
+	.type _fp_hw,@object
+
+/* 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