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execsp.S revision 1.2 
      1 /*	$NetBSD: execsp.S,v 1.2 2025/04/21 02:31:22 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 1.2 2025/04/21 02:31:22 riastradh Exp $")
     34 
     35 	.set noat
     36 	.text
     37 
     38 /*
     39  * void execsp_start(void *stackpointer@a0, void (*cleanup@a1)(void),
     40  *     void *obj_main@a2, struct ps_strings *ps_strings@a3)
     41  *
     42  *	ELF entry point.  Saves the stack pointer in startsp and defers
     43  *	to the usual csu __start routine.
     44  */
     45 LEAF(execsp_start, 4)
     46 	LDGP(pv)
     47 	ldq	at_reg, startsp(gp)	!literal
     48 	stq	sp, 0(at_reg)
     49 	ldq	pv, __start(gp)		!literal
     50 	jmp	(pv), __start
     51 END(execsp_start)
     52 
     53 /*
     54  * void execsp_ctor(void)
     55  *
     56  *	ELF constructor.  Saves the stack pointer in ctorsp and
     57  *	returns.
     58  */
     59 LEAF(execsp_ctor, 0)
     60 	LDGP(pv)
     61 	ldq	at_reg, ctorsp(gp)	!literal
     62 	stq	sp, 0(at_reg)
     63 	RET
     64 END(execsp_ctor)
     65 
     66 	/* Make execsp_ctor a constructor. */
     67 	.pushsection .ctors,"aw",@progbits
     68 	.p2align 3
     69 	.quad	execsp_ctor
     70 	.popsection
     71 
     72 /*
     73  * int main(int argc@a0, char **argv@a1, ...)
     74  *
     75  *	Main function.  Saves the stack pointer in mainsp and returns
     76  *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
     77  *	been initialized.
     78  */
     79 LEAF(main, 2)
     80 	LDGP(pv)
     81 	ldq	at_reg, mainsp(gp)	!literal
     82 	stq	sp, 0(at_reg)
     83 	mov	zero, v0
     84 	RET
     85 END(main)
     86 
     87 /*
     88  * void execsp_dtor(void)
     89  *
     90  *	ELF destructor.  Saves the stack pointer in dtorsp and defers
     91  *	to the C execsp_main in h_execsp.c to report the stack pointers
     92  *	back to the t_signal_and_sp parent.
     93  */
     94 LEAF(execsp_dtor, 0)
     95 	LDGP(pv)
     96 	ldq	at_reg, dtorsp(gp)	!literal
     97 	stq	sp, 0(at_reg)
     98 	ldq	pv, execsp_main(gp)	!literal
     99 	jmp	(pv), execsp_main
    100 END(execsp_dtor)
    101 
    102 	/* Make execsp_ctor a destructor. */
    103 	.pushsection .dtors,"aw",@progbits
    104 	.p2align 3
    105 	.quad	execsp_dtor
    106 	.popsection
    107