61
Other Discussion / Re: NASM or YASM in the modern era (or something else)
« Last post by debs3759 on February 03, 2024, 10:43:57 PM »As far as I know, this is it. There are mailing lists, but they are dead.
Recent Posts
62
Programming with NASM / gdb and debug symbols
« Last post by decuser on February 03, 2024, 10:25:11 PM »nasm newb here...
I have started using nasm and I am trying to debug my program. I did nasm -g and ld -g and when I open gdb, or ddd, it shows my listing and will let me step through the code and whatnot, yay! However, when I try to display a variable's address using 'info address bVar1' it says:
Symbol "bVar1" is at 0x402000 in a file compiled without debugging.
What it means, as I understand it, is that the file was not compiled with gnu debugging symbols. Obviously, there are debugging symbols present, but they're in whatever the default format is for nasm. Should I be worried, or just ignore it?
FWIW, stuff like:
(gdb) x/db &bVar1
seems to work:
0x402000 <bVar1>: 17
Thx!
I have started using nasm and I am trying to debug my program. I did nasm -g and ld -g and when I open gdb, or ddd, it shows my listing and will let me step through the code and whatnot, yay! However, when I try to display a variable's address using 'info address bVar1' it says:
Symbol "bVar1" is at 0x402000 in a file compiled without debugging.
What it means, as I understand it, is that the file was not compiled with gnu debugging symbols. Obviously, there are debugging symbols present, but they're in whatever the default format is for nasm. Should I be worried, or just ignore it?
FWIW, stuff like:
(gdb) x/db &bVar1
seems to work:
0x402000 <bVar1>: 17
Thx!
63
Other Discussion / Re: NASM or YASM in the modern era (or something else)
« Last post by decuser on February 03, 2024, 09:53:13 PM »Cool. So, is there another chattier hangout for nasm users?
64
Other Discussion / Re: NASM or YASM in the modern era (or something else)
« Last post by debs3759 on February 03, 2024, 09:37:11 PM »I don't know yasm, but I can tell you that nasm is constantly in development, with new instruction sets being added pretty much as soon as they are released. We have an Intel developer on the nasm dev team. The forums are not very active most of the time, but there are a couple of active Linux coders who will try to help when they can.
65
Other Discussion / NASM or YASM in the modern era (or something else)
« Last post by decuser on February 03, 2024, 08:58:28 PM »Hi all,
Longtime listener, first time caller...
I'm learning assembly on my whiz-bang MX-Linux 23-2 "Libretto" machine w/Intel i7-3770. I have dabbled, but now I'm quite serious. As it turns out, there appear to be many choices as to what assembler to use. The text I've chosen to start with "x86-64 Assembly Language Programming with Ubuntu" by Ed Jorgensen, available at http://www.egr.unlv.edu/~ed/assembly64.pdf favors yasm and ddd as the toolchain. They work on MX-Linux and that's great, but I don't want to spend a lot of time with a toolchain that I may not settle on. So, before I go too far, I figure I'll ask the experts (y'all)...
Are either NASM or YASM good choices for the assembler, here in 2024, or should I be looking elsewhere? Are either or another actively developed/maintained? What resources do you recommend for the 2024 beginner/intermediate learner?
Thx!
Longtime listener, first time caller...
I'm learning assembly on my whiz-bang MX-Linux 23-2 "Libretto" machine w/Intel i7-3770. I have dabbled, but now I'm quite serious. As it turns out, there appear to be many choices as to what assembler to use. The text I've chosen to start with "x86-64 Assembly Language Programming with Ubuntu" by Ed Jorgensen, available at http://www.egr.unlv.edu/~ed/assembly64.pdf favors yasm and ddd as the toolchain. They work on MX-Linux and that's great, but I don't want to spend a lot of time with a toolchain that I may not settle on. So, before I go too far, I figure I'll ask the experts (y'all)...
Are either NASM or YASM good choices for the assembler, here in 2024, or should I be looking elsewhere? Are either or another actively developed/maintained? What resources do you recommend for the 2024 beginner/intermediate learner?
Thx!
66
Programming with NASM / Re: Linux 64bit / Threads
« Last post by andyz74 on January 30, 2024, 06:54:30 PM »OK, so I will see, if I can get a working program of this. :-)
Thanks for the hint! :-)
Thanks for the hint! :-)
67
Programming with NASM / Re: Linux 64bit / Threads
« Last post by fredericopissarra on January 26, 2024, 12:09:53 PM »For a parent process to wait for a child one is a matter of using sys_wait4 syscall. You can retrieve the errorcode returned by the process (for example: 0 = prime, 1 = not prime)...
68
Programming with NASM / Re: Linux 64bit / Threads
« Last post by andyz74 on January 25, 2024, 08:31:24 PM »OK, I've tested your code and it runs nicely. :-)
But to be honest, I think, my intended question is still open. (Waiting at each other of the processes...)
Maybe I should explain a little better : I have modified this code to calculate primes. Let's say, i want to test the number 2000 to be a prime:
So I divided 2000 by 2 ( got 1000 ) and
tell the parent process to divide the 2000 through all numbers between 2 and 1000, and
tell the child process to divide the 2000 through all numbers between 1000 and 2000.
I know, the range can easily be decreased from 2 to sqrt(number) but I do it like this for testing the fork-thing.
If the parent-process, or the child-process sees a division which goes out even, some boolean-like variable like "not_a_prime" should be set to 1 and both processes could be stopped. Otherwise it is a prime.
But to be honest, I think, my intended question is still open. (Waiting at each other of the processes...)
Maybe I should explain a little better : I have modified this code to calculate primes. Let's say, i want to test the number 2000 to be a prime:
So I divided 2000 by 2 ( got 1000 ) and
tell the parent process to divide the 2000 through all numbers between 2 and 1000, and
tell the child process to divide the 2000 through all numbers between 1000 and 2000.
I know, the range can easily be decreased from 2 to sqrt(number) but I do it like this for testing the fork-thing.
If the parent-process, or the child-process sees a division which goes out even, some boolean-like variable like "not_a_prime" should be set to 1 and both processes could be stopped. Otherwise it is a prime.
69
Programming with NASM / Re: Linux 64bit / Threads
« Last post by fredericopissarra on January 25, 2024, 08:48:30 AM »There are no 'threads' here, but different processes...
Here's a better implementation for your forking...
Here's a better implementation for your forking...
Code: [Select]
; fork,asn
;
; nasm -f elf64 -o fork.o fork.asm
; ld -s fork.o -o fork
; ./fork
bits 64
default rel ; All offset only effective addresses are rip-relative from now on...
; Since no data will be writen, they can be at .rodata section.
section .rodata
; We don't need the nul char!
childMsg db `This is the child process\n` ; a message string
clength equ $-childMsg
parentMsg db `This is the parent process\n` ; a message string
plength equ $-parentMsg
tspec:
dq 3 ; 3 seconds delay.
dq 0
section .text
global _start
_start:
; Notice: Using RAX here will encode a 10 bytes instruction (rex prefix, 8 bytes for the immediate and the opcode).
; In x86-64 mode, changing E?? will AUTOMATICALLY zero the upper 32 bits of R?? registers.
mov eax,57 ; sys_fork
syscall
; fork() will return a file descriptor (int type).
test eax,eax
js .fail ; sys_fork can fail (returs a descriptor < 0).
jz .child
; Parent process.
mov eax,1 ; sys_write
mov edi,eax ; stdout
lea rsi,[parentMsg] ; Must be rip-relative addressing.
mov edx,plength
syscall
call workalot
.exit:
mov eax,60
xor edi,edi
syscall
.fail:
mov eax,60
mov edi,1
syscall
align 4
.child:
mov eax,1 ; sys_write
mov edi,eax ; stdout
lea rsi,[childMsg] ; message address (rip-relative)
mov edx,clength ; message string length
syscall
call workalot
jmp .exit
; -------- unten nur proceduren ---------------------
align 4
workalot:
mov eax,35 ; sys_nanosleep
lea rdi,[tspec]
xor esi,esi
syscall
ret
70
Programming with NASM / Linux 64bit / Threads
« Last post by andyz74 on January 24, 2024, 05:38:14 PM »Hi !
I'm just playing around with learning about threads. Somewhere in the internet I found a little example and changed it for my mind and it seems to work correct for now.
As you see, it just throws out two little messages in a fork and runs down a delay and stops.
Now, my question is, if I have dependencies in the threads at each other, maybe some calculations with needed sums at the end, than I have to wait for this.
I know, there exists something called
"SYSCALL_WAIT4"
but to be honest, I don't have a clue, how to realize that. :-/
Does anyone habe a nice example or can explain a little bit?
Greetings, Andy :-)
I'm just playing around with learning about threads. Somewhere in the internet I found a little example and changed it for my mind and it seems to work correct for now.
Code: [Select]
; Fork
; nasm -f elf64
; ld fork.o -o fork
; Run with: ./fork
[bits 64]
SECTION .data
childMsg db 'This is the child process', 0h ; a message string
clength equ $-childMsg
parentMsg db 'This is the parent process', 0h ; a message string
plength equ $-parentMsg
crlf db 0xA,0xD ; newline, length is 2
SECTION .text
global _start
_start:
mov rax, 57 ; SYS_FORK
syscall
cmp rax, 0 ; if eax is zero we are in the child process
jz child ; jump if eax is zero to child label
parent:
mov rax, 1 ; sys_write
mov rdi, 1 ; stdout
mov rsi, parentMsg ; message address
mov rdx, plength ; message string length
syscall
mov rax, 1 ; sys_write
mov rdi, 1 ; stdout
mov rsi, crlf ; message address
mov rdx, 2 ; message string length
syscall
call workalot
jmp exit
child:
mov rax, 1 ; sys_write
mov rdi, 1 ; stdout
mov rsi, childMsg ; message address
mov rdx, clength ; message string length
syscall
mov rax, 1 ; sys_write
mov rdi, 1 ; stdout
mov rsi, crlf ; message address
mov rdx, 2 ; message string length
syscall
call workalot
jmp exit
exit:
mov rax, 60 ; sys_exit
mov rdi, 0 ; return 0 (success)
syscall
; -------- unten nur proceduren ---------------------
workalot:
mov rcx, 65000
loop1:
push rcx
mov rcx, 65000
loop2:
push rcx
nop
pop rcx
loop loop2
pop rcx
loop loop1
ret
As you see, it just throws out two little messages in a fork and runs down a delay and stops.
Now, my question is, if I have dependencies in the threads at each other, maybe some calculations with needed sums at the end, than I have to wait for this.
I know, there exists something called
"SYSCALL_WAIT4"
but to be honest, I don't have a clue, how to realize that. :-/
Does anyone habe a nice example or can explain a little bit?
Greetings, Andy :-)