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Diffstat (limited to 'REORG.TODO/sysdeps/x86_64/start.S')
| -rw-r--r-- | REORG.TODO/sysdeps/x86_64/start.S | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/x86_64/start.S b/REORG.TODO/sysdeps/x86_64/start.S new file mode 100644 index 0000000000..62a00eaeaa --- /dev/null +++ b/REORG.TODO/sysdeps/x86_64/start.S @@ -0,0 +1,131 @@ +/* Startup code compliant to the ELF x86-64 ABI. + Copyright (C) 2001-2017 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 + LP_SIZE(%rsp) argv[0] + ... + (LP_SIZE*argc)(%rsp) NULL + (LP_SIZE*(argc+1))(%rsp) envp[0] + ... + NULL +*/ + +#include <sysdep.h> + +ENTRY (_start) + /* 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. */ + + mov %RDX_LP, %R9_LP /* Address of the shared library termination + function. */ +#ifdef __ILP32__ + mov (%rsp), %esi /* Simulate popping 4-byte argument count. */ + add $4, %esp +#else + popq %rsi /* Pop the argument count. */ +#endif + /* argv starts just at the current stack top. */ + mov %RSP_LP, %RDX_LP + /* Align the stack to a 16 byte boundary to follow the ABI. */ + and $~15, %RSP_LP + + /* Push garbage because we push 8 more bytes. */ + pushq %rax + + /* 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. */ + mov __libc_csu_fini@GOTPCREL(%rip), %R8_LP + mov __libc_csu_init@GOTPCREL(%rip), %RCX_LP + + mov main@GOTPCREL(%rip), %RDI_LP +#else + /* Pass address of our own entry points to .fini and .init. */ + mov $__libc_csu_fini, %R8_LP + mov $__libc_csu_init, %RCX_LP + + mov $main, %RDI_LP +#endif + + /* Call the user's main function, and exit with its value. + But let the libc call main. Since __libc_start_main in + libc.so is called very early, lazy binding isn't relevant + here. Use indirect branch via GOT to avoid extra branch + to PLT slot. In case of static executable, ld in binutils + 2.26 or above can convert indirect branch into direct + branch. */ + call *__libc_start_main@GOTPCREL(%rip) + + hlt /* Crash if somehow `exit' does return. */ +END (_start) + +/* 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 |