/* Copyright (C) 2011-2017 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. 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 . */ #include /* Get address of "sym" in "reg" assuming r51 holds ".Llink". */ .macro pic_addr reg, sym moveli \reg, hw1_last(\sym - .Llink) shl16insli \reg, \reg, hw0(\sym - .Llink) ADD_PTR \reg, r51, \reg .endm .text ENTRY (_start) /* Linux starts us with sp pointing at the conventional Elf layout, but we need to allow two 'caller' words for our ABI convention. */ { move r52, sp andi sp, sp, -8 } cfi_def_cfa_register (r52) { /* Point sp at base of ABI area; point r4 to the caller-sp word. */ ADDI_PTR sp, sp, -(2 * REGSIZE) ADDI_PTR r4, sp, -REGSIZE } { /* Save zero for caller sp in our 'caller' save area, and make sure lr has a zero value, to limit backtraces. */ move lr, zero st r4, zero } { move r0, r52 jal _dl_start } /* Save returned start of user program address for later. */ move r50, r0 /* See if we were invoked explicitly with the dynamic loader, in which case we have to adjust the argument vector. */ lnk r51; .Llink: pic_addr r4, _dl_skip_args ld4u r4, r4 beqzt r4, .Lno_skip /* Load the argc word at the initial sp and adjust it. We basically jump "sp" up over the first few argv entries and write "argc" a little higher up in memory, to be the base of the new kernel-initialized stack area. */ LD_PTR r0, r52 { sub r0, r0, r4 SHL_PTR_ADD r52, r4, r52 } { ST_PTR r52, r0 SHL_PTR_ADD sp, r4, sp } andi sp, sp, -8 .Lno_skip: /* Call_dl_init (_dl_loaded, argc, argv, envp). See elf/start.s for the layout of memory here; r52 is pointing to "+0". */ pic_addr r0, _rtld_local { LD_PTR r1, r52 /* load argc in r1 */ ADDLI_PTR r2, r52, __SIZEOF_POINTER__ /* point r2 at argv */ } { LD_PTR r0, r0 /* yields _rtld_global._ns_loaded */ addi r3, r1, 1 move lr, zero } { SHL_PTR_ADD r3, r3, r2 /* point r3 at envp */ jal _dl_init } /* Call user program whose address we saved in r50. We invoke it just like a static binary, but with _dl_fini in r0 so we can distinguish. */ pic_addr r0, _dl_fini move lr, zero { move sp, r52 jr r50 } /* Tell backtracer to give up (_start has no caller). */ info 2 /* INFO_OP_CANNOT_BACKTRACE */ END (_start)