/* Copyright (C) 2011 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Chris Metcalf , 2011. 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, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ /* This is the canonical entry point, usually the first thing in the text segment. The ELF standard tells us that the stack is set up like this on entry (the left side is the offset from "sp"), in units of __SIZEOF_POINTER__ entries: +0 argc +1 argv[0] ... +(argc+1) NULL +(argc+2) envp[0] ... NULL ... ElfInfo The ElfInfo is pairs of key/value long words following the envp pointers and terminated by a zero-valued key. Although not mandated by the standard, it happens to be the case that we store the actual argv and envp strings immediately after the ElfInfo data on the stack. On entry r0 points to the shared library termination function, or 0 if there isn't one. */ #include #include #include .text .global _start .type _start,@function .align 8 _start: /* Linux starts us with sp pointing at the conventional Elf layout, but we need to allow two "caller" words for our ABI convention. */ { /* Load argc (stored as a "long", equivalent to a pointer type). */ LD_PTR r1, sp /* Save incoming 'sp', which points to the Elf argument block. */ move r52, sp } { /* Allocate stack frame callee space for __libc_start_main. */ ADDI_PTR r12, sp, -(2 * REGSIZE) } { /* Get our PC. */ lnk r13 /* sp is not necessarily properly aligned on startup because of the way ld.so pops off leading argv elements. So align it. */ andi sp, r12, -8 } .Lmy_pc: { /* Pass the address of the shared library termination function. */ move r5, r0 /* Compute location where __libc_start_main's caller is supposed to store its frame pointer. */ ADDI_PTR r12, sp, REGSIZE /* Zero out callee space for return address. Unnecessary but free. This is just paranoia to help backtracing not go awry. */ ST sp, zero } { /* Zero out our frame pointer for __libc_start_main. */ ST r12, zero /* Zero out lr to make __libc_start_main the end of backtrace. */ move lr, zero /* Compute a pointer to argv. envp will be determined later in __libc_start_main. We set up the first argument (the address of main) below. */ ADDI_PTR r2, r52, __SIZEOF_POINTER__ } { /* Pass the highest stack address to user code. */ ADDI_PTR r6, sp, (2 * REGSIZE) /* Pass address of main() in r0, and of our own entry points to .fini and .init in r3 and r4. */ #ifdef __tilegx__ moveli r0, hw2_last(main - .Lmy_pc) } { moveli r3, hw2_last(__libc_csu_init - .Lmy_pc) shl16insli r0, r0, hw1(main - .Lmy_pc) } { shl16insli r3, r3, hw1(__libc_csu_init - .Lmy_pc) shl16insli r0, r0, hw0(main - .Lmy_pc) } { shl16insli r3, r3, hw0(__libc_csu_init - .Lmy_pc) moveli r4, hw2_last(__libc_csu_fini - .Lmy_pc) } { ADD_PTR r0, r0, r13 shl16insli r4, r4, hw1(__libc_csu_fini - .Lmy_pc) } { ADD_PTR r3, r3, r13 shl16insli r4, r4, hw0(__libc_csu_fini - .Lmy_pc) } { ADD_PTR r4, r4, r13 #else addli r0, r13, lo16(main - .Lmy_pc) } { auli r0, r0, ha16(main - .Lmy_pc) addli r3, r13, lo16(__libc_csu_init - .Lmy_pc) } { auli r3, r3, ha16(__libc_csu_init - .Lmy_pc) addli r4, r13, lo16(__libc_csu_fini - .Lmy_pc) } { auli r4, r4, ha16(__libc_csu_fini - .Lmy_pc) #endif /* Call the user's main function, and exit with its value. But let the libc call main. */ j plt(__libc_start_main) } { /* Tell backtracer to give up (_start has no caller). */ info INFO_OP_CANNOT_BACKTRACE } .size _start, .-_start /* Define a symbol for the first piece of initialized data. */ .data .global __data_start .align 8 __data_start: .long 0 .weak data_start data_start = __data_start