2001-09-19 18:37:31 +08:00
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/* Startup code compliant to the ELF x86-64 ABI.
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2003-05-29 05:04:20 +08:00
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Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
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2001-09-19 18:37:31 +08:00
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This file is part of the GNU C Library.
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Contributed by Andreas Jaeger <aj@suse.de>, 2001.
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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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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, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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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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%rdx 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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%rsp The stack contains the arguments and environment:
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0(%rsp) argc
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8(%rsp) argv[0]
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...
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(8*argc)(%rsp) NULL
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(8*(argc+1))(%rsp) envp[0]
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...
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NULL
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*/
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#include "bp-sym.h"
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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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xorq %rbp, %rbp
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/* Extract the arguments as encoded on the stack and set up
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the arguments for __libc_start_main (int (*main) (int, char **, char **),
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int argc, char *argv,
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void (*init) (void), void (*fini) (void),
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void (*rtld_fini) (void), void *stack_end).
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The arguments are passed via registers and on the stack:
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main: %rdi
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argc: %rsi
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argv: %rdx
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init: %rcx
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fini: %r8
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rtld_fini: %r9
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stack_end: stack. */
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movq %rdx, %r9 /* Address of the shared library termination
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function. */
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popq %rsi /* Pop the argument count. */
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movq %rsp, %rdx /* argv starts just at the current stack top. */
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/* Align the stack to a 16 byte boundary to follow the ABI. */
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andq $~15, %rsp
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pushq %rax /* Push garbage because we push 8 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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pushq %rsp
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2003-05-29 05:04:20 +08:00
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#ifdef SHARED
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/* Pass address of our own entry points to .fini and .init. */
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movq __libc_csu_fini@GOTPCREL(%rip), %r8
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movq __libc_csu_init@GOTPCREL(%rip), %rcx
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movq BP_SYM (main)@GOTPCREL(%rip), %rdi
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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 BP_SYM (__libc_start_main)@PLT
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#else
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2001-09-19 18:37:31 +08:00
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/* Pass address of our own entry points to .fini and .init. */
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2002-12-10 04:37:37 +08:00
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movq $__libc_csu_fini, %r8
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movq $__libc_csu_init, %rcx
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2001-09-19 18:37:31 +08:00
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movq $BP_SYM (main), %rdi
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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 BP_SYM (__libc_start_main)
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2003-05-29 05:04:20 +08:00
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#endif
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2001-09-19 18:37:31 +08:00
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hlt /* Crash if somehow `exit' does return. */
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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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