/* Startup code compliant to the ELF s390 ABI.

   Copyright (C) 2000-2018 Free Software Foundation, Inc.

   Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).

   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, see

   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>

/*

   This is the canonical entry point, usually the first thing in the text

   segment. Most registers' values are unspecified, except for:

   %r14         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.

   %r15		The stack contains the arguments and environment:

		0(%r15)			argc

		4(%r15)			argv[0]

		...

		(4*argc)(%r15)		NULL

		(4*(argc+1))(%r15)	envp[0]

		...

					NULL

*/

	.text

	.globl _start

	.type _start,@function

_start:

	cfi_startproc

	/* Mark r14 as undefined in order to stop unwinding here!  */

	cfi_undefined (r14)

	/* Check if the kernel provides highgprs facility if needed by

	   the binary.  */

	lr	%r6,%r15

	la	%r6,4(%r6)     /* Skip the argument counter.  */

.L11:	l	%r5,0(%r6)     /* Skip the argument vector.  */

	la	%r6,4(%r6)

	ltr	%r5,%r5

	jne	.L11

.L12:	l	%r5,0(%r6)     /* Skip the environment vector.  */

	la	%r6,4(%r6)

	ltr	%r5,%r5

	jne	.L12

	/* Usually the auxiliary vector can be expected directly after

	   the environment variables.  But we have to skip extra zeros

	   because the loader might have removed unsecure variables for

	   setuid programs.  */

.L26:	l	%r5,0(%r6)

	la	%r6,4(%r6)

	ltr	%r5,%r5

	jz	.L26

	ahi	%r6,-4

	/* Obtain the needed values from the auxiliary vector.  */

	lhi	%r7,16	       /* AT_HWCAP */

	lhi	%r8,3	       /* AT_PHDR */

	lhi	%r9,5          /* AT_PHNUM */

	lhi	%r2,4          /* AT_PHENT */

.L13:	l	%r5,0(%r6)

	clr	%r5,%r7

	jne	.L15

	l	%r10,4(%r6)    /* r10 = AT_HWCAP value.  */

.L15:	clr	%r5,%r8

	jne	.L16

	l	%r11,4(%r6)    /* r11 = AT_PHDR value.  */

.L16:	clr	%r5,%r9

	jne	.L17

	l	%r12,4(%r6)    /* r12 = AT_PHNUM value.  */

.L17:	clr	%r5,%r2

	jne	.L18

	l	%r0,4(%r6)     /* r0 = AT_PHENT value.  */

.L18:	ltr	%r5,%r5

	la	%r6,8(%r6)

	jnz	.L13

	/* Locate the ELF header by looking for the first PT_LOAD

	   segment with a p_offset of zero.  */

	lr	%r4,%r11       /* Backup AT_PHDR.  */

	lhi	%r7,1          /* PT_LOAD id */

	lhi	%r8,0

.L19:	cl	%r7,0(%r4)     /* p_type == PT_LOAD? */

	jne	.L20

	cl	%r8,4(%r4)     /* p_offset == 0? */

	jne	.L20

	l	%r9,8(%r4)     /* r9 = PT_LOAD.p_vaddr <- ELF header address  */

	j	.L24

.L20:	alr	%r4,%r0        /* r4 += AT_PHENT value */

	brct	%r12,.L19

	j	.+2            /* Trap, there must be such a phdr.  */

.L24:	lr	%r4,%r11       /* Backup AT_PHDR.  */

	lhi	%r2,6          /* PT_PHDR id */

.L23:	cl	%r2,0(%r4)

	jne	.L22

	l	%r3,8(%r4)     /* r3 = PT_PHDR p_vaddr */

	j	.L25

.L22:	alr	%r4,%r0        /* r4 += AT_PHENT value */

	brct	%r12,.L23

	j	.L14	       /* No PT_PHDR found - skip checking.  */

.L25:	slr	%r11,%r3       /* AT_PHDR - PT_PHDR.p_vaddr (relocation offset)*/

	alr	%r9,%r11       /* PT_LOAD.p_vaddr += relocation offset */

	l	%r5,36(%r9)    /* Load the e_flags field.  */

	tml	%r5,1

	jz	.L14	       /* Binary does not require highgprs facility.  */

	tml	%r10,512       /* Check the AT_HWCAP value.  */

	jz	2              /* Trap if no highgprs facility available.  */

.L14:

	/* Setup pointer to literal pool of _start */

	basr    %r13,0

.L0:    ahi     %r13,.Llit-.L0

	/* load argc and argv from stack */

	la      %r4,4(%r15)             # get argv

	l       %r3,0(%r15)             # get argc

	/* align the stack to a double word boundary */

	lhi     %r0,-8

	nr      %r15,%r0

	/* Setup a stack frame and a parameter area */

	ahi     %r15,-104               # make room on stack

	xc      0(4,%r15),0(%r15)       # clear back-chain

	/* set up arguments for __libc_start_main:

	   main, argc, argv, envp, _init, _fini, rtld_fini, stack_end

	   Note that envp will be determined later in __libc_start_main

	 */

	stm     %r14,%r15,96(%r15)      # store rtld_fini/stack_end to parameter area

	la      %r7,96(%r15)

	l       %r6,.L2-.Llit(%r13)     # load pointer to __libc_csu_fini

	l       %r5,.L1-.Llit(%r13)     # load pointer to __libc_csu_init

	l       %r2,.L3-.Llit(%r13)     # load pointer to main

	l       %r1,.L4-.Llit(%r13)	# load pointer to __libc_start_main

#ifdef PIC

	l       %r12,.L5-.Llit(%r13)    # load .got pointer

	la	%r6,0(%r13,%r6)

	la	%r5,0(%r13,%r5)

	la	%r12,0(%r13,%r12)

	l	%r2,0(%r12,%r2)

	la	%r1,0(%r13,%r1)

#endif

	/* ok, now branch to the libc main routine */

	basr    %r14,%r1

	/* crash if __libc_start_main returns */

	.word   0

	cfi_endproc

.Llit:

#ifndef PIC

.L1:    .long  __libc_csu_init

.L2:    .long  __libc_csu_fini

.L3:    .long  main

.L4:    .long  __libc_start_main

#else

.L1:    .long  __libc_csu_init-.Llit

.L2:    .long  __libc_csu_fini-.Llit

.L3:    .long  main@GOT

.L4:    .long  __libc_start_main@plt-.Llit

.L5:    .long  _GLOBAL_OFFSET_TABLE_-.Llit

#endif

/* 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