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execsp.S revision 1.1 
      1 /*	$NetBSD: execsp.S,v 1.1 2025/04/20 22:33:13 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 22:33:13 riastradh Exp $")
     34 
     35 /*
     36  * void execsp_start(void (*cleanup@edx)(void), void *obj_main@ecx,
     37  *     struct ps_strings *ps_strings@ebx)
     38  *
     39  *	ELF entry point.  Saves the stack pointer in startsp and defers
     40  *	to the usual csu __start routine.
     41  */
     42 ENTRY(execsp_start)
     43 	call	getpc_eax
     44 	addl	$_GLOBAL_OFFSET_TABLE_,%eax
     45 	movl	_C_LABEL(startsp)@GOT(%eax),%eax
     46 	movl	%esp,(%eax)
     47 	jmp	_C_LABEL(__start)@PLT
     48 END(execsp_start)
     49 
     50 /*
     51  * void execsp_ctor(void)
     52  *
     53  *	ELF constructor.  Saves the stack pointer in ctorsp and
     54  *	returns.
     55  */
     56 ENTRY(execsp_ctor)
     57 	call	getpc_eax
     58 	addl	$_GLOBAL_OFFSET_TABLE_,%eax
     59 	movl	_C_LABEL(ctorsp)@GOT(%eax),%eax
     60 	movl	%esp,(%eax)
     61 	ret
     62 END(execsp_ctor)
     63 
     64 	/* Make execsp_ctor a constructor. */
     65 	.section .ctors,"aw",@progbits
     66 	.p2align 2
     67 	.long	_C_LABEL(execsp_ctor)
     68 
     69 /*
     70  * int main(int argc@rdi, char **argv@rsi, ...)
     71  *
     72  *	Main function.  Saves the stack pointer in mainsp and returns
     73  *	zero.  We will call execsp_main in execsp_dtor once dtorsp has
     74  *	been initialized.
     75  */
     76 ENTRY(main)
     77 	call	getpc_eax
     78 	addl	$_GLOBAL_OFFSET_TABLE_,%eax
     79 	movl	_C_LABEL(mainsp)@GOT(%eax),%eax
     80 	movl	%esp,(%eax)
     81 	xorl	%eax,%eax
     82 	ret
     83 END(main)
     84 
     85 /*
     86  * void execsp_dtor(void)
     87  *
     88  *	ELF destructor.  Saves the stack pointer in dtorsp and defers
     89  *	to the C execsp_main in h_execsp.c to report the stack pointers
     90  *	back to the t_signal_and_sp parent.
     91  */
     92 ENTRY(execsp_dtor)
     93 	call	getpc_eax
     94 	addl	$_GLOBAL_OFFSET_TABLE_,%eax
     95 	movl	_C_LABEL(dtorsp)@GOT(%eax),%eax
     96 	movl	%esp,(%eax)
     97 	jmp	_C_LABEL(execsp_main)@PLT
     98 END(execsp_dtor)
     99 
    100 	/* Make execsp_ctor a destructor. */
    101 	.section .dtors,"aw",@progbits
    102 	.p2align 2
    103 	.long	_C_LABEL(execsp_dtor)
    104 
    105 	.text
    106 	_ALIGN_TEXT
    107 	.local	getpc_eax
    108 	.type	getpc_eax,@function
    109 getpc_eax:
    110 	movl	(%esp),%eax
    111 	ret
    112 END(getpc_eax)
    113