diff options
Diffstat (limited to 'libc/sysdeps/linux/xtensa/crt1.S')
| -rw-r--r-- | libc/sysdeps/linux/xtensa/crt1.S | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/xtensa/crt1.S b/libc/sysdeps/linux/xtensa/crt1.S new file mode 100644 index 000000000..63fbadc15 --- /dev/null +++ b/libc/sysdeps/linux/xtensa/crt1.S @@ -0,0 +1,119 @@ +/* Startup code compliant to the ELF Xtensa ABI. + Copyright (C) 2001, 2007 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + 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., 51 Franklin Street - Fifth Floor, + Boston, MA 02110-1301, USA. */ + +#include <features.h> + +#ifndef __UCLIBC_CTOR_DTOR__ + .weak _init + .weak _fini +#endif + +/* This is the canonical entry point, usually the first thing in the text + segment. When the entry point runs, most register values are unspecified, + except for: + + a2 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. + + a1 The stack (i.e., a1+16) contains the arguments and environment: + a1+0 argc + a1+4 argv[0] + ... + a1+(4*argc) NULL + a1+(4*(argc+1)) envp[0] + ... + NULL + + Setup parameters accordingly (for a call4). See function prototype + from sysdeps/generic/libc-start.c + + a6 = *main + a7 = argc + a8 = ubp_av + a9 = *init + a10 = *fini + a11 = *rtld_fini + [sp+0] = stack_end + */ + + .text + .align 4 + .literal_position + .global _start + .type _start, @function +_start: + /* Clear a0 to obviously mark the outermost frame. */ + movi a0, 0 + + /* Load up the user's main function. */ + movi a6, main + + /* Extract the arguments as encoded on the stack and set up + the arguments for `main': argc, argv. envp will be determined + later in __uClibc_main. */ + l32i a7, a1, 0 /* Load the argument count. */ + addi a8, a1, 4 /* Compute the argv pointer. */ + + /* Push address of our own entry points to .fini and .init. */ + movi a9, _init + movi a10, _fini + + /* Setup the shared library termination function. */ + mov a11, a2 + + /* Provide the highest stack address to the user code (for stacks + which grow downwards). Note that we destroy the stack version + of argc here. */ + s32i a1, a1, 0 + + /* Call the user's main function, and exit with its value. + But let the libc call main. */ + movi a4, __uClibc_main + callx4 a4 + + /* Crash if somehow `exit' does return. */ + ill + + /* Define a symbol for the first piece of initialized data. */ + .data + .align 4 + .global __data_start +__data_start: + .long 0 + .weak data_start + data_start = __data_start |