From: Clem Cole <clemc@ccc.com>
To: Alexander Voropay <alec@sensi.org>
Cc: The Eunuchs Hysterical Society <tuhs@tuhs.org>
Subject: Re: [TUHS] as(1) on Ultrix-11 vs 2.11BSD
Date: Thu, 30 Apr 2020 18:06:16 -0400 [thread overview]
Message-ID: <CAC20D2PcSkWdqTjcnxFWdT109E_FhR9v0xJmMMF2tkLxNPfQXg@mail.gmail.com> (raw)
In-Reply-To: <CAGqcPWAX_N4tvg4DCDC5CWHNnYAmObz0cn7hHU95Po5m7j-8bA@mail.gmail.com>
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Alexander, the exit(2) system call takes a parameter, which is an integer
status that the process will return. The value 0 is traditionally a
successful return, and anything else signifies an error condition.
This assembler is the moral equiv of:
char hello[] = { "hello world\n" };
main() {
write(1, hello, sizeof(hello));
exit(0);
}
On Thu, Apr 30, 2020 at 5:50 PM Alexander Voropay <alec@sensi.org> wrote:
> Can anyone please explain the last $0 pushed to the stack ?
> Early SysIII ans SYSV on the i386 (and may be on i286) used
> similar syscall convention.
>
> I wrote about this:
> https://minnie.tuhs.org/pipermail/tuhs/2019-October/019274.html
> https://minnie.tuhs.org/pipermail/tuhs/2019-October/019294.html
>
> Example:
> ===
> .file "test.s"
> .version "02.01"
> .set WRITE,4
> .set EXIT,1
> .text
> .align 4
> .globl entry
> entry:
> pushl %ebp
> movl %esp,%ebp
> subl $8,%esp
>
> pushl $14 /length
> pushl $hello
> pushl $1 /STDOUT
> pushl $0
> movl $WRITE,%eax
> lcall $0x07,$0
> addl $16,%esp
>
> pushl $0
> movl $EXIT,%eax
> lcall 0x07,$0
>
> .data
> .align 4
> hello:
> .byte 0x48,0x65,0x6c,0x6c,0x6f,0x2c, 0x20,0x77,0x6f,0x72
> .byte 0x6c,0x64,0x21,0x0a,0x00
>
> ср, 29 апр. 2020 г. в 17:19, <ron@ronnatalie.com>:
> >
> > Thanks for the link. With that help, I fixed the bug in the program:
> >
> > mov $6., -(sp)
> > mov $1f, -(sp)
> > mov $1,-(sp)
> > mov $0,-(sp)
> > sys 4
> > add $8., sp
> > mov $0,-(sp)
> > mov $0,-(sp)
> > sys 1
> > 1: <hello>
> >
> >
> > >> Sorry, I typed that in haste without testing. I don’t have a 2.11
> system
> > >> to try it on. However, reading the source code, I did that wrong. The
> > >> args go on the stack, not in line with the code.
> > >> mov $6, -(sp)
> > >> mov a, -(sp)
> > >> mov $1,-(sp)
> > >> sys 4
> > >
> > > Without suggesting that every helpful post should be tested, I find the
> > > superb https://unix50.org web emulator excellent for such things.
> > >
> > > Many thanks to the folks hosting & maintaining this great resource!
> > >
> > >
> >
> >
>
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next prev parent reply other threads:[~2020-04-30 22:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 13:55 Paul Ruizendaal
2020-04-29 14:18 ` ron
2020-04-30 21:49 ` Alexander Voropay
2020-04-30 22:06 ` Clem Cole [this message]
2020-04-30 22:09 ` Clem Cole
2020-05-01 0:12 ` Ronald Natalie
-- strict thread matches above, loose matches on Subject: below --
2020-04-29 2:26 Noel Chiappa
2020-04-29 4:08 ` Jacob Ritorto
2020-04-29 12:20 ` Ronald Natalie
2020-04-28 1:56 Jacob Ritorto
2020-04-28 13:03 ` Ronald Natalie
2020-04-29 0:17 ` Jacob Ritorto
2020-04-29 0:54 ` ron
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