4 Jan
2022
4 Jan
'22
8:37 p.m.
So,
in v6, it was possible to use the mesg function from the system library
with:
ed hello.s
/ hello world using external mesg routine
.globl mesg
mov sp,r5
jsr r5,mesg; <Hello, World!\n\0>; .even
sys exit
as hello.sld -s a.out -l
a.out
Hello, World!
This was because v6 included mesg in the library, in v7, it doesn't look
like mesg is included, so doing the same thing as above requires that
code to write the message out be included and in addition system call
names are not predefined, so exit and write have to be looked up in
/usr/include/sys.s, resulting in the v7 equivalent file:
ed hello2.s
/ hello world using internal mesg routine
mov sp,r5
jsr r5,mesg; <Hello, World!\n\0>; .even
sys 1
mesg:
mov r0,-(sp)
mov r5,r0
mov r5,0f
1:
tstb (r5)+
bne 1b
sub r5,r0
com r0
mov r0,0f+2
mov $1,r0
sys 0; 9f
.data
9:
sys 4; 0:..; ..
.text
inc r5
bic $1,r5
mov (sp)+,r0
rts r5
as hello2.s
a.out
Hello, World!
My questions are:
1. Is mesg or an equivalent available in v7?
2. If not, what was the v7 way of putting strings out?
3. Why aren't the system call names defined?
4. What was the v7 way of naming system calls?
Will
4 Jan
4 Jan
9:12 p.m.
On Tue, Jan 4, 2022 at 3:38 PM Will Senn <will.senn(a)gmail.com> wrote:
[snip]
My questions are:
1. Is mesg or an equivalent available in v7?
Perhaps just call printf?
2. If not, what was the v7 way of putting strings out?
Here's what I did:
$ rm -f h h.o
$ cat h.s
.globl _printf, _exit
mov sp, r5
mov $hi,(sp)
jsr pc,*$_printf
mov $0, (sp)
jsr pc,*$_exit
hi: <Hello, World!\n\0>
$ as -o h.o h.s
$ ld -o h h.o -lc
$ ./h
Hello, World!
$ rm h h.o
3. Why aren't the system call names defined?
If I had to hazard a guess, it would have been to de-emphasize the use
of assembler for user code, particularly as 7th Edition was starting
to be portable beyond the PDP-11.
4. What was the v7 way of naming system calls?
I imagine the canonical way to invoke system calls from assembler was
invoking calling functions in the C library and linking against that.
- Dan C.
9:24 p.m.
On 1/4/22 3:12 PM, Dan Cross wrote:
On Tue, Jan 4, 2022 at 3:38 PM Will
Senn<will.senn(a)gmail.com> wrote:
Yep, that worked... you make it look so easy, and your rationales
are
definitely believable :).
Will
[snip]
My questions are:
1. Is mesg or an equivalent available in v7?
Perhaps just call printf?
2. If not, what was the v7 way of putting strings
out?
Here's what I did:
$ rm -f h h.o
$ cat h.s
.globl _printf, _exit
mov sp, r5
mov $hi,(sp)
jsr pc,*$_printf
mov $0, (sp)
jsr pc,*$_exit
hi: <Hello, World!\n\0>
$ as -o h.o h.s
$ ld -o h h.o -lc
$ ./h
Hello, World!
$ rm h h.o
3. Why aren't the system call names defined?
If I had to hazard a guess, it would have been to de-emphasize the use
of assembler for user code, particularly as 7th Edition was starting
to be portable beyond the PDP-11.
4. What was the v7 way of naming system calls?
I imagine the canonical way to invoke system calls from assembler was
invoking calling functions in the C library and linking against that.
- Dan C. 
9:28 p.m.
On Tue, Jan 4, 2022 at 2:24 PM Will Senn <will.senn(a)gmail.com> wrote:
On 1/4/22 3:12 PM, Dan Cross wrote:
On Tue, Jan 4, 2022 at 3:38 PM Will Senn <will.senn(a)gmail.com>
<will.senn(a)gmail.com> wrote:
[snip]
My questions are:
1. Is mesg or an equivalent available in v7?
Perhaps just call printf?
2. If not, what was the v7 way of putting strings out?
Here's what I did:
$ rm -f h h.o
$ cat h.s
.globl _printf, _exit
mov sp, r5
mov $hi,(sp)
jsr pc,*$_printf
mov $0, (sp)
jsr pc,*$_exit
hi: <Hello, World!\n\0>
$ as -o h.o h.s
$ ld -o h h.o -lc
$ ./h
Hello, World!
$ rm h h.o
3. Why aren't the system call names defined?
If I had to hazard a guess, it would have been to de-emphasize the use
of assembler for user code, particularly as 7th Edition was starting
to be portable beyond the PDP-11.
4. What was the v7 way of naming system calls?
I imagine the canonical way to invoke system calls from assembler was
invoking calling functions in the C library and linking against that.
- Dan C.
Yep, that worked... you make it look so easy, and your rationales are
definitely believable :).
You can use puts too, at least in v7.
The system call interface between V6 and V7 changed as well... Some
internal AT&T branches
(cb unix for one) could run both V6 and V7 binaries. BSD uses the v7 system
call interface through
2.10.x. 2.11 moves to a new system call interface as well. There's niggles
in these statements, since
it isn't quite exactly the same, but for things like this it's ok.
V7 also moved to stdio completely. V6 had precursor routines to stdio and
mesg() was dropped in
that whole process.
Warner
5 Jan
5 Jan
5:35 p.m.
On Tue, Jan 4, 2022 at 4:28 PM Warner Losh <imp(a)bsdimp.com> wrote:
On Tue, Jan 4, 2022 at 2:24 PM Will Senn
<will.senn(a)gmail.com> wrote:
> Yep, that worked... you make it look so easy, and your rationales are definitely
believable :).
It would be nice to hear about the rationale from a primary source.
Perhaps Ken or Doug might chime in?
You can use puts too, at least in v7.
Ah right; I always forget that puts was unequivocally a function in
7th Ed. It'll even add a newline for you!
- Dan C.
4 Jan
4 Jan
9:38 p.m.
On Tue, Jan 4, 2022 at 3:38 PM Will Senn <will.senn(a)gmail.com> wrote:
1. Is mesg or an equivalent available in v7?
its not part of the C stdio library and by te
2. If not, what was the v7 way of putting strings
out?
_puts declared as an external
3. Why aren't the system call names defined?
Ah .. you want the DEC assembler ;-) By the time of V5/V6 assembler is
starting to have less importance and by V7, little if anything is left.
4. What was the v7 way of naming system calls?
_XXX where XXX is the system call declared as a global.
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5 comments
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participants (4)
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Clem Cole -
Dan Cross -
Warner Losh -
Will Senn