29 Apr
2020
29 Apr
'20
1:55 p.m.
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!
29 Apr
29 Apr
2:18 p.m.
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!
30 Apr
30 Apr
9:49 p.m.
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(a)ronnatalie.com>om>:
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!
10:06 p.m.
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(a)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(a)ronnatalie.com>om>:
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!
10:09 p.m.
Ouch - just looked at that more carefully. exit it returning the what
was left on the stack. The push $0 is something in the system calling
convention for that port. You'll have to look at the kernel sources for
that system in code that takes the trap.
Clem
On Thu, Apr 30, 2020 at 6:06 PM Clem Cole <clemc(a)ccc.com> wrote:
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(a)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(a)ronnatalie.com>om>:
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!
1 May
1 May
12:12 a.m.
The syscall skips over a location for reasons not fully clear to me. I guess if you dug
down into the libc functions that call it you’d figure out why. As far as the kernel is
concerned, it just doesn’t look at it.
The zero is just a spacer, other code just does a tst -(sp) there which just decrs the
stack poitner.
On Apr 30, 2020, at 5:49 PM, Alexander Voropay
<alec(a)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(a)ronnatalie.com>om>:
>
> 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!
>>
>>
>
>
1453
days inactive
1455
days old
5 comments
5 participants
participants (5)
-
Alexander Voropay -
Clem Cole -
Paul Ruizendaal -
ron＠ronnatalie.com -
Ronald Natalie