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      1 /*	$NetBSD: execsp.S,v 1.1 2025/04/20 22:32:49 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2025 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #define	_LOCORE
     30 
     31 #include <machine/asm.h>
     32 
     33 RCSID("$NetBSD: execsp.S,v 1.1 2025/04/20 22:32:49 riastradh Exp $")
     34 
     35 	.import _GLOBAL_OFFSET_TABLE_
     36 
     37 /*
     38  * void execsp_start(struct ps_strings *ps_strings@arg0,
     39  *     void (*cleanup@arg1)(void), void *obj_main@arg2)
     40  *
     41  *	ELF entry point.  Saves the stack pointer in startsp and defers
     42  *	to the usual csu __start routine.
     43  */
     44 LEAF_ENTRY(execsp_start)
     45 	/*
     46 	 * Set up the data pointer (r19) and linkage table register
     47 	 * (r27) like the real startup routine so we can get at the
     48 	 * global symbols startsp and __start.
     49 	 *
     50 	 * XXX Not really sure why we need to set up r27, since we only
     51 	 * use r19 here and the real startup routine, __start, will set
     52 	 * up both r19 and r27 anyway.  But this crashes with SIGSEGV
     53 	 * shortly after startup if we don't set up r27, and gdb
     54 	 * crashes on my attempts to single-step, so I'll just leave
     55 	 * the initialization of r27 here for now until someone is
     56 	 * motivated by the potential for a single-instruction
     57 	 * micro-optimization in this test program to find out why r27
     58 	 * is needed too.
     59 	 */
     60 	bl	L$lpc, %r27
     61 	 depi	0, 31, 2, %r27
     62 L$lpc:	addil	L'_GLOBAL_OFFSET_TABLE_ - ($PIC_pcrel$0 - 8), %r27
     63 	ldo	R'_GLOBAL_OFFSET_TABLE_ - ($PIC_pcrel$0 - 12)(%r1), %r27
     64 	copy	%r27, %r19
     65 
     66 	addil	LT%_C_LABEL(startsp), %r19	/* r20 := &startsp */
     67 	ldw	RT%_C_LABEL(startsp)(%r1), %r20
     68 
     69 	/* PIC_TAILCALL(__start), if we had it */
     70 	addil	LT%_C_LABEL(__start), %r19	/* r1 := __start */
     71 	ldw	RT%_C_LABEL(__start)(%r1), %r1
     72 	bv	%r0(%r1)			/* jump to __start */
     73 	 stw	%sp, 0(%r20)			/* startsp := sp */
     74 EXIT(execsp_start)
     75 
     76 /*
     77  * void execsp_ctor(void)
     78  *
     79  *	ELF constructor.  Saves the stack pointer in ctorsp and
     80  *	returns.
     81  */
     82 LEAF_ENTRY(execsp_ctor)
     83 	addil	LT%_C_LABEL(ctorsp), %r19	/* r1 := &ctorsp */
     84 	ldw	RT%_C_LABEL(ctorsp)(%r1), %r1
     85 	bv	%r0(%rp)			/* return */
     86 	 stw	%sp, 0(%r1)			/* ctorsp := sp */
     87 EXIT(execsp_ctor)
     88 
     89 	/* Make execsp_ctor a constructor. */
     90 	.section .ctors,"aw",@progbits
     91 	.p2align 2
     92 	.word	_C_LABEL(execsp_ctor)
     93 
     94 /*
     95  * int main(int argc@arg0, char **argv@arg1, ...)
     96  *
     97  *	Main function.  Saves the stack pointer in mainsp and returns
     98  *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
     99  *	been initialized.
    100  */
    101 LEAF_ENTRY(main)
    102 	addil	LT%_C_LABEL(mainsp), %r19	/* r1 := &mainsp */
    103 	ldw	RT%_C_LABEL(mainsp)(%r1), %r1
    104 	stw	%sp, 0(%r1)			/* ctorsp := sp */
    105 	bv	%r0(%rp)			/* return... */
    106 	 copy	%r0, %ret0			/* ...zero */
    107 EXIT(main)
    108 
    109 /*
    110  * void execsp_dtor(void)
    111  *
    112  *	ELF destructor.  Saves the stack pointer in dtorsp and defers
    113  *	to the C execsp_main in h_execsp.c to report the stack pointers
    114  *	back to the t_signal_and_sp parent.
    115  */
    116 LEAF_ENTRY(execsp_dtor)
    117 	addil	LT%_C_LABEL(dtorsp), %r19	/* r20 := &dtorsp */
    118 	ldw	RT%_C_LABEL(dtorsp)(%r1), %r20
    119 
    120 	/* PIC_TAILCALL(__start), if we had it */
    121 	addil	LT%_C_LABEL(execsp_main), %r19	/* r1 := execsp_main */
    122 	ldw	RT%_C_LABEL(execsp_main)(%r1), %r1
    123 	bv	%r0(%r1)			/* jump to execsp_main */
    124 	 stw	%sp, 0(%r20)			/* startsp := sp */
    125 EXIT(execsp_dtor)
    126 
    127 	/* Make execsp_ctor a destructor. */
    128 	.section .dtors,"aw",@progbits
    129 	.p2align 2
    130 	.word	_C_LABEL(execsp_dtor)
    131