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1e8e527dd9
Since start.o may be compiled as PIC, we should check PIC instead of SHARED. Also avoid dynamic relocation against main in static PIE since _start is the entry point before the executable is relocated. * sysdeps/i386/start.S (_start): Check Check PIC instead of SHARED. Avoid dynamic relocation against main in static PIE.
147 lines
4.7 KiB
ArmAsm
147 lines
4.7 KiB
ArmAsm
/* Startup code compliant to the ELF i386 ABI.
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Copyright (C) 1995-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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In addition to the permissions in the GNU Lesser General Public
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License, the Free Software Foundation gives you unlimited
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permission to link the compiled version of this file with other
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programs, and to distribute those programs without any restriction
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coming from the use of this file. (The GNU Lesser General Public
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License restrictions do apply in other respects; for example, they
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cover modification of the file, and distribution when not linked
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into another program.)
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Note that people who make modified versions of this file are not
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obligated to grant this special exception for their modified
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versions; it is their choice whether to do so. The GNU Lesser
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General Public License gives permission to release a modified
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version without this exception; this exception also makes it
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possible to release a modified version which carries forward this
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exception.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* This is the canonical entry point, usually the first thing in the text
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segment. The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
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point runs, most registers' values are unspecified, except for:
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%edx Contains a function pointer to be registered with `atexit'.
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This is how the dynamic linker arranges to have DT_FINI
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functions called for shared libraries that have been loaded
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before this code runs.
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%esp The stack contains the arguments and environment:
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0(%esp) argc
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4(%esp) argv[0]
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...
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(4*argc)(%esp) NULL
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(4*(argc+1))(%esp) envp[0]
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...
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NULL
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*/
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.text
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.globl _start
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.type _start,@function
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_start:
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/* Clear the frame pointer. The ABI suggests this be done, to mark
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the outermost frame obviously. */
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xorl %ebp, %ebp
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/* Extract the arguments as encoded on the stack and set up
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the arguments for `main': argc, argv. envp will be determined
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later in __libc_start_main. */
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popl %esi /* Pop the argument count. */
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movl %esp, %ecx /* argv starts just at the current stack top.*/
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/* Before pushing the arguments align the stack to a 16-byte
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(SSE needs 16-byte alignment) boundary to avoid penalties from
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misaligned accesses. Thanks to Edward Seidl <seidl@janed.com>
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for pointing this out. */
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andl $0xfffffff0, %esp
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pushl %eax /* Push garbage because we allocate
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28 more bytes. */
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/* Provide the highest stack address to the user code (for stacks
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which grow downwards). */
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pushl %esp
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pushl %edx /* Push address of the shared library
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termination function. */
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#ifdef PIC
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/* Load PIC register. */
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call 1f
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addl $_GLOBAL_OFFSET_TABLE_, %ebx
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/* Push address of our own entry points to .fini and .init. */
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leal __libc_csu_fini@GOTOFF(%ebx), %eax
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pushl %eax
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leal __libc_csu_init@GOTOFF(%ebx), %eax
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pushl %eax
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pushl %ecx /* Push second argument: argv. */
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pushl %esi /* Push first argument: argc. */
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# ifdef SHARED
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pushl main@GOT(%ebx)
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# else
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/* Avoid relocation in static PIE since _start is called before
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it is relocated. */
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leal main@GOTOFF(%ebx), %eax
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pushl %eax
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# endif
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/* Call the user's main function, and exit with its value.
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But let the libc call main. */
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call __libc_start_main@PLT
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#else
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/* Push address of our own entry points to .fini and .init. */
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pushl $__libc_csu_fini
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pushl $__libc_csu_init
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pushl %ecx /* Push second argument: argv. */
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pushl %esi /* Push first argument: argc. */
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pushl $main
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/* Call the user's main function, and exit with its value.
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But let the libc call main. */
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call __libc_start_main
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#endif
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hlt /* Crash if somehow `exit' does return. */
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#ifdef PIC
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1: movl (%esp), %ebx
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ret
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#endif
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/* To fulfill the System V/i386 ABI we need this symbol. Yuck, it's so
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meaningless since we don't support machines < 80386. */
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.section .rodata
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.globl _fp_hw
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_fp_hw: .long 3
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.size _fp_hw, 4
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.type _fp_hw,@object
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/* Define a symbol for the first piece of initialized data. */
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.data
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.globl __data_start
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__data_start:
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.long 0
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.weak data_start
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data_start = __data_start
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