This sort of stuff is why I love being a software engineer. The lower you go it starts to feel like an expedition into the mysterious caves under a city. Great job, you got a new sub.
I have been teaching myself about programming/web development for years, and I feel like this is the time to start my journey closer to the machine and understand what is really happening You deserved a new sub
@@LowLevelTV Hi, I just found your channel, and love it! I have been a software developer for 22 years, started as a Delphi developer, then PHP, JS, TS in the meantime, recently C and C++ for Arduino or ESP32, as a hobby, and I realized, that I like low level programming, and assembly the most. I started machine code in the C64 era, so I know everything about 6502 processor, interrupts, memory handling, memory mapped registers, remember many hexa code of every assembly opcodes, addressing types, can write any code in 8bit. I wrote basic extensions for C64 BASIC, even framework for a window OS system like GEOS on C64, font editor in half basic and assembly, screen interrupts to use more than 16 color on screen, etc. I think I should go back to low level programming, because i feel it closer to me than CSS rules and flexbox layout. Is there any demand for low level programmers recently? Is there any point to switch career to this? I'd have many questions...
Cool video! Some ideas of what I think would be interesting: 1. Seeing how a program in high-level language (simple hello world or some file manipulation) gets actually executed on a CPU. It would be extra nice if the high-level language was something with VM in between, like Java or C# (.NET). 2. Explanation of how device drivers work in Linux. 3. Kernel stuff - explained in a way that is easy to understand 4. How the multithreaded or async code is executed on the CPU (multiple cores, multiple threads) - that would be interesting 5. Comparing different architectures of CPU - it would be great to see you giving an overview of CPUs from very simple ones (some AVR, or old 6502, or something even simpler), up to what we have today. I think that would make it much easier to understand why today's architecture are so complicated.
@@mnj1 It's not a VM language because the IL gets JIT-compiled to native machine code at runtime. This only happens once and the resulting code is not run in a VM. It's native machine code. At that point it's the same as compiled C, only with less optimisations because the JIT compiler has to run very quickly. There is no VM involved whatsoever. Java runs a VM, C# does not.
14:27 BTW, I got interested in the instruction "mov r0, #65". Why is the 65 a funny number in embedded programming? Once it's in a decimal format, it's the equivalent to 'A', right?
Last night I finally had the opportunity to try this out on my Pi and am happy with the results. I noticed two things, e.g. that you use „svc“ in later videos, which was „swi“ here (is apparently the same) and that you always start with the r7 (later x8) value and then type out the arguments. I don‘t know about coding conventions yet, but noticed that the order doesn’t technically matter as the execution only happens at swi/svc. When I stepped through this with GDB, I noticed that „pc“ when moved into a register, already points to the next instruction. I don‘t remember if you talk about this in one of your following videos, please excuse if this is the case and my suggestion to cover this is redundant. Thanks again, your content is really helpful.
Super cool to know. I've been exploring x86 as I'm trying to position myself in a better place for a career in reverse engineering. Since Microsoft is showing its biggest push for ARM yet, I'm interested in understanding ARM architecture as well.
You need more followers so that you are more visible :) Glad the algorithm go it right for me. I learned about assembler but never did anything useful with it so it faded away. Maybe you could present a use case scenario where you use assembler to get some use or function out of an older ARM tablet or phone that is no longer fast enough for Windows/Android and does not have Linux support?
I still have an iPhone 4 in the electronics spare parts bin that powers on and an iPhone 5 that is still booting too. Several Windows tablets, and a pile of Pi's. Just sayin :)
That was really easy to understand. My only small quip is that you are pretty quiet - I had to turn the volume up quite a bit - perhaps consider getting a cheap usb studio mic (~$100)?
I would argue x86 is no more complicated for basic things at least. With x86_64, arguably even simpler. Being able to access memory directly without a load, and the sys call instruction, I would think easier than having to think about load/store and software interrupts.
I have multiple questions : 1- why do we need to exit ? I can understand that the system call is the interface to the kernel? where is the kernel we just wrote simple bare metal sw ? so which kernel do we interface with it and caused this crash? 2 - ldr r1 =message do we need the address of memory location to be loaded to the register or the data it self? 3- which .txt or .data this code is linked to? which memory region do we have linker?
I think you are confused. He is writing a program for a computer running on ARM processor, eg Raspberry Pi. It is not for a microcontroller where system call is not required.
Thanks for watching! I'm making these ARM tutorials in a Virtualbox VM, but they will also work on a Raspberry Pi. Check the pinned comment for instructions to compile natively on an ARM platform
I use the program QEMU to emulate an ARM processor and run my programs. If you use a Raspberry Pi you dont need to do this. In either scenario the code that gets created is ARM
Does anyone know if there is a RasPi equivalent of the old style C64 monitor programs ? Tried out gdb, but it's not too friendly. (at least for me, today)
So just to clarify, when you do software interrupt 0, that's not hard-coded in ARM, right? That's just how the Linux kernel implements syscalls? So at some point during its startup, the Linux kernel defines an interrupt handler for swi 0 that checks register 7 and performs whatever routine you requested? Or does the ARM specification require that swi 0 be the way to handle calls into the kernel?
If I’m running windows then I need a VM to work in a Linux environment? Openbox or Proxmox. If I’m running Linux in a VM should I just run an ARM version? Manjaro? What is the HEX editor you ran x??, the screen was too blurry to make it out.
You do need to be in a VM to do this. It doesn't have to be an ARM VM, the commands I use do emulation so you can run ARM binaries in an Intel environment. The command was xxd. Thanks for watching! :)
The thing I'm grappling with is what is linux kernal loaded as boot vs. what is already in a raspberry pi (zero) rom? and how is that same or different when using qemu
How is the information stored? The program gets compiled into assembly, .elf. This elf file is stored either in memory or on the HDD. Is it in the storage medium as hex?
That should also be Pico compatible as well. M0 are arm cores, there is no OS on there, and it’s the same eabi (Embedded Application Binary Interface). (This is formatting (eg. gcc-arm-none-eabi) known as a “triple target”). I’m basically hoping that this will each me some PIO programming that has to be done in ARM Assembly.
at 13:53 i was expecting to see "mov r2, #14" instead of "mov r2, #13" because of the implicit null terminator "\0". how is it that assembly does not have this annoying behaviour that c is so famous for?
3:20 "Step 1... run this command". I can't read any of that. Is it written down somewhere? Out of curiosity, how big was the monitor used to make this, and what resolution was it set to?
What is he writing the code in for it to compile? I've searched all over the internet and everything is either wrong, outdated, missing, or for a OS that I'm not using.
Thanks great video but quick questions: What environment IDE are you using ? What tools (opensource) do you recommend to use the compiler/drbuger in GUI mode ? I’m currently using docker for ARM/asm-32bit but have problem Docker blocks the debugger GDB, so I’m testimg a GDB SERVER with a C.H.I.P. Online, have 38 students not all have Rpi so we virtualization QEMU, but is a pain working GUI IDE on 1/8 of the screen So thats why the questions!
I was unable to install 'gcc-arm-linux-gnueabi' using 'apt' with the error 'No installation candidate'. Spent 20 minutes or so searching for alternate packages only to realize 'apt-get' was all I needed.
I've done a fair bit of C with STM32, been wanting to explore writing some raw assembly for it since I have a ton of STM32s lying around with nothing to do. It just pains me that ARM syntax is right-to-left like NASM. AT&T syntax is way more intuitive to me, but oh well, not that big of a deal :b
Update to my last comment Thanks to @simvalue changed " mov r0, #0x01 " -to- " mov x0, #0x01 " no error message Can you please explain in a tutorial, whats happening? Thank You.
Thank you for great video. Just add: that arm executable could run on x86 linux without calling `qemu-arm' directly, via binfmt_misc mechanism: % uname -p x86_64 % file 001.elf 001.elf: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, not stripped % ./001.elf zsh: exec format error: ./001.elf % sudo apt install qemu-user-static ... % ./001.elf Hello, World % hostnamectl status | tail -3 Operating System: Ubuntu 21.04 Kernel: Linux 5.11.0-25-generic Architecture: x86-64
"we assembled our assembly into machine code. We compiled it into a runable .elf" I don't understand the last part. I though compilers also output machine code. What's the difference between compiler output(ed) machine code and the elf?
Great tutorial, the only thing that is confusing for me, is why length of message string is equal 13 not 14? From the way you count, I assume that you interpret " " as string of length 1, but why is that? Thanks for help in advance :)
Ah, I probably should have explained this a little bit. When you see \ followed by a character in a string, that's called an "escape character". Escape characters are used to represent characters that the keyboard cannot type or that would otherwise be misrepresented if typed manually. When the assembler interprets that string, it treats the sequence as ONE character, to represent the enter key. I hope that makes sense. Thanks for watching!
@@LowLevelTV Yes it does, i'm familiar with programming in c and c++, but for some reason I thought that assembler is more ... I don't know, literal? anyway, thanks :)
@@LowLevelTV recommending your channel to my students we are using ARM with docker (but Docker with Gdb don’t work) so I’m checking if I put a GDB server online (not secure) but students struggle to “view the inside”. Recommend a GDB (with colors) in next future video
The weirdest part about trying to follow is "oh, my windows doesn't have sudo apt get arm or other assembly packages and doesn't know what to do with .elf even though with normal assembly it compiles".
![เปิดคำทำนาย นอสตราดามุส - บาบา วานก้า ปี 2025 คนทั่วโลกต้องเจออะไรบ้าง? | แฉ 11 ธ.ค. 67 [2/3] |GMM25](http://i.ytimg.com/vi/xmTIKWJUMPM/mqdefault.jpg)
For people doing this direct on a pi. Nothing needs to be installed and the commands are:
as 001.asm -o 001.o
gcc 001.o -o 001.elf -nostdlib
Thank you!
I'm doing this on termux:
$ as a.asm -o a.o
$ ld a.o
@@int16_t ooh ta, that worked too on the pi. Can control file name in same way: ld 001.o -o 001.elf
@Hand Grabbing Fruits IIRC, it was automatically installed after "pkg install clang". Not sure though.
and if you're using a Pi4 you need to use x0 instead of r0 because its 64 bits
This sort of stuff is why I love being a software engineer. The lower you go it starts to feel like an expedition into the mysterious caves under a city. Great job, you got a new sub.
Couldn't agree more!
I need your help in one ARM assembly coding assignment pl
That's an amazing way to look at it
so f*king true
I have been teaching myself about programming/web development for years, and I feel like this is the time to start my journey closer to the machine and understand what is really happening
You deserved a new sub
The amount of information presented in short amount of time (and still makes sense) is awesome. Nice work!
3:05 - For what it's worth, I taught high school science for 3-4 year, and I think your pacing so far's been spot on.
Great video. Haven't touched ASM in 40 years. Got a pi sitting in front of me and I'm raring to mov stuff.
That's awesome
Same. These videos are definitely getting my appetite for Assembly going. Last real Assembly I did was on a Motorola 6809. Nice pun, BTW. :)
same as you. I haven't touched it since 1988.
@@hansoak3664 Lol.. me too
@@LowLevelTV Hi, I just found your channel, and love it!
I have been a software developer for 22 years, started as a Delphi developer, then PHP, JS, TS in the meantime, recently C and C++ for Arduino or ESP32, as a hobby, and I realized, that I like low level programming, and assembly the most.
I started machine code in the C64 era, so I know everything about 6502 processor, interrupts, memory handling, memory mapped registers, remember many hexa code of every assembly opcodes, addressing types, can write any code in 8bit. I wrote basic extensions for C64 BASIC, even framework for a window OS system like GEOS on C64, font editor in half basic and assembly, screen interrupts to use more than 16 color on screen, etc.
I think I should go back to low level programming, because i feel it closer to me than CSS rules and flexbox layout. Is there any demand for low level programmers recently? Is there any point to switch career to this? I'd have many questions...
I learned more about assembly in this 15 minute video than I did in an entire LC-3 course. It makes sense now.
I never was on LC-3 course, but I know this type of academy courses.
keep making these videos. There is a lack of good embedded videos on the internet. Many of us wouldn't even mind paying for these courses on udemy.
@@AA7Productionz well don't tell him that!!!
Ok. That was the coolest hello world I’ve ever seen.
Cool video!
Some ideas of what I think would be interesting:
1. Seeing how a program in high-level language (simple hello world or some file manipulation) gets actually executed on a CPU. It would be extra nice if the high-level language was something with VM in between, like Java or C# (.NET).
2. Explanation of how device drivers work in Linux.
3. Kernel stuff - explained in a way that is easy to understand
4. How the multithreaded or async code is executed on the CPU (multiple cores, multiple threads) - that would be interesting
5. Comparing different architectures of CPU - it would be great to see you giving an overview of CPUs from very simple ones (some AVR, or old 6502, or something even simpler), up to what we have today. I think that would make it much easier to understand why today's architecture are so complicated.
C# doesn't have a VM in between. It JIT-compiles to machine code.
@@clonkex There is the MSIL language in-between. It is the VM language
@@mnj1 It's not a VM language because the IL gets JIT-compiled to native machine code at runtime. This only happens once and the resulting code is not run in a VM. It's native machine code. At that point it's the same as compiled C, only with less optimisations because the JIT compiler has to run very quickly. There is no VM involved whatsoever. Java runs a VM, C# does not.
Underrated channel! You deserve many times the views. Keep up the good work!
Much appreciated!
I need your help in one ARM ASSEMBLY ASSIGNMENT PL
Thank you for this perfect tutorial!
To save some typing:
# ARM Assembly Tutorial - 001.arm
.global _start
.section .text
# STDIN - 0
# STDOUT - 1
# STDERR - 2
# write a string to stdout
_start:
mov r7, #0x4
mov r0, #1
ldr r1, =message
mov r2, #13
swi 0
mov r7, #0x1
mov r0, #65
swi 0
.section .data
message:
.ascii "Hello, World
"
swi 0 do not work on x64 asm
I need your help in one ARM assembly coding assignment pl
@@preetik9873 ok
"emacs if you are one of those people" *audible disgust*
LMAO
HAHAHA
14:27 BTW, I got interested in the instruction "mov r0, #65". Why is the 65 a funny number in embedded programming? Once it's in a decimal format, it's the equivalent to 'A', right?
Thanks, really like the way you presented it. Hope you’ll continue this series :)
> Hope you'll continue this seris
I also agree!
Last night I finally had the opportunity to try this out on my Pi and am happy with the results. I noticed two things, e.g. that you use „svc“ in later videos, which was „swi“ here (is apparently the same) and that you always start with the r7 (later x8) value and then type out the arguments. I don‘t know about coding conventions yet, but noticed that the order doesn’t technically matter as the execution only happens at swi/svc. When I stepped through this with GDB, I noticed that „pc“ when moved into a register, already points to the next instruction. I don‘t remember if you talk about this in one of your following videos, please excuse if this is the case and my suggestion to cover this is redundant. Thanks again, your content is really helpful.
I need your help in one ARM ASSEMBLY ASSIGNMENT PL
The C in RISC means Computer, not Compiler.
It's Complicated.
@@dabdoube92 nuh uh
I enjoyed a lot the video. It was very informative, thanks. You've got a new subs
"... in 15 Minutes"
'Looks at length of video' : 15:00
Man, I trust you from now on
I need your help in one ARM ASSEMBLY ASSIGNMENT PL
More please .... this is a super useful video
More to come!
not boring at all, please continue, I learnt a lot
I need your help in one assignment
Wow, we're rolling the calendar back over 40 years, more like 50 years.
Thanks!
Wow thank you so much! You're welcome!
6:43
“We’re gonna take the object file we created and we’re going to produce an elf….Damn it”
Lmfaooo that was so damn funny
Fun! Followed along on my RPi zero w. I'll have to wait for my Mac mini to arrive to try the 64-bit stuff.
Awesome! I'm glad you could follow along!
excellent explanation expressed in a concise and informal way. never had the urge to fast forward. thanks!
Glad you liked it!
I'm trying to get into ARM programming and maybe rev engineering some arm things someday. This is pretty easy to understand. Thank you
Very very very very good!
Thank You very much!
Please, make a complete playlist of ARM Assembly.
This is really quite brilliant. Very high quality content. I'm on board to continue consuming, I really hope you continue producing.
Super cool to know. I've been exploring x86 as I'm trying to position myself in a better place for a career in reverse engineering. Since Microsoft is showing its biggest push for ARM yet, I'm interested in understanding ARM architecture as well.
on Ubuntu, this command does the trick to install the compiler:
$ sudo apt-get -y install gcc-arm*
Also we don't need to hardcoded the message length:
# ARM Assembly Tutorial 001
.global _start
.section .text
# STDIN - 0
# STDOUT - 1
# STDERR - 2
# write a string to stdout
_start:
mov r7, #0x4
mov r0, #1
ldr r1, =message
mov r2, #MSG_LEN
swi 0
mov r7, #0x1
mov r0, #65
swi 0
.section .data
message:
.ascii "Hello, World
"
.equ MSG_LEN, . - message
Playing with small little registers...
That seams fun!
You need more followers so that you are more visible :) Glad the algorithm go it right for me. I learned about assembler but never did anything useful with it so it faded away. Maybe you could present a use case scenario where you use assembler to get some use or function out of an older ARM tablet or phone that is no longer fast enough for Windows/Android and does not have Linux support?
I still have an iPhone 4 in the electronics spare parts bin that powers on and an iPhone 5 that is still booting too. Several Windows tablets, and a pile of Pi's. Just sayin :)
Really good tutorial. Thank you!
' sudo apt install gcc-5-arm-linux-gnueabi ' doesn't work on Ubuntu 20.4
apt search for gcc-10-arm-linux-gneuabi instead, and apt install that.
More than a decade programming embedded software and I never heard a joke about the number 65 ...
I'm still tring to figure that out, lol!
That was really easy to understand. My only small quip is that you are pretty quiet - I had to turn the volume up quite a bit - perhaps consider getting a cheap usb studio mic (~$100)?
Thanks for watching!
Yes, this video was probably the worst of mine in terms of audio quality, I believe my others are better.
perhaps considering contributing a "cheap" $100 donation
Ty u for making this. As an EE major, this helps so much!!!!
I would argue x86 is no more complicated for basic things at least. With x86_64, arguably even simpler. Being able to access memory directly without a load, and the sys call instruction, I would think easier than having to think about load/store and software interrupts.
I have multiple questions : 1- why do we need to exit ? I can understand that the system call is the interface to the kernel? where is the kernel we just wrote simple bare metal sw ? so which kernel do we interface with it and caused this crash? 2 - ldr r1 =message do we need the address of memory location to be loaded to the register or the data it self? 3- which .txt or .data this code is linked to? which memory region do we have linker?
I think you are confused. He is writing a program for a computer running on ARM processor, eg Raspberry Pi. It is not for a microcontroller where system call is not required.
Great video man, keep it up !
One question though, what is your execution platform ? Is it some Rasberry, stm32 or what ?
Thanks for watching!
I'm making these ARM tutorials in a Virtualbox VM, but they will also work on a Raspberry Pi. Check the pinned comment for instructions to compile natively on an ARM platform
@@LowLevelTV so the actual target machine is set to what exactly ? Does the VM emulate arm core ?
I use the program QEMU to emulate an ARM processor and run my programs. If you use a Raspberry Pi you dont need to do this.
In either scenario the code that gets created is ARM
@@LowLevelTV thanks man, I totally missed that quemu part, I took it for smth else. It's all clear now thanks a lot !!
Great Video! Please post these more often. They are very helpful and explain alot better than my prof
I need your help in Arm assembly assignment. pl
Awesome video. What software are you using to compile the code? This is my first time coding in assembly and I'm not sure how to get started.
Hey man do you have a ARM64 tutorial as well, just wondering?
This is fantastic!
Does anyone know if there is a RasPi equivalent of the old style C64 monitor programs ? Tried out gdb, but it's not too friendly. (at least for me, today)
Great tutorial.
Nice. You have a new subscriber!
Excellent video!
Thank you very much!
I need your help in one ARM assembly coding assignment pl
cant wait to start the new era for the demoscene
So just to clarify, when you do software interrupt 0, that's not hard-coded in ARM, right? That's just how the Linux kernel implements syscalls? So at some point during its startup, the Linux kernel defines an interrupt handler for swi 0 that checks register 7 and performs whatever routine you requested? Or does the ARM specification require that swi 0 be the way to handle calls into the kernel?
If I’m running windows then I need a VM to work in a Linux environment? Openbox or Proxmox.
If I’m running Linux in a VM should I just run an ARM version? Manjaro?
What is the HEX editor you ran x??, the screen was too blurry to make it out.
You do need to be in a VM to do this. It doesn't have to be an ARM VM, the commands I use do emulation so you can run ARM binaries in an Intel environment. The command was xxd.
Thanks for watching! :)
keep up the good work!
Thanks, will do!
The thing I'm grappling with is what is linux kernal loaded as boot vs. what is already in a raspberry pi (zero) rom? and how is that same or different when using qemu
But why you using "qemu-arm"? You showed all this on ax86 PC ?
What is the relationship between qemu qemu-arm and qemu-system-arm ?
thank you for the content
How is the information stored?
The program gets compiled into assembly, .elf. This elf file is stored either in memory or on the HDD. Is it in the storage medium as hex?
ELF files are binary, yes
I need your help in one ARM assembly coding assignment pl
can you suggest us a more recent arm complier?
gcc-arm-none-eabi does the trick for me.
@@LowLevelTV thank you, you're a myth
That should also be Pico compatible as well. M0 are arm cores, there is no OS on there, and it’s the same eabi (Embedded Application Binary Interface). (This is formatting (eg. gcc-arm-none-eabi) known as a “triple target”). I’m basically hoping that this will each me some PIO programming that has to be done in ARM Assembly.
at 13:53 i was expecting to see "mov r2, #14" instead of "mov r2, #13" because of the implicit null terminator "\0".
how is it that assembly does not have this annoying behaviour that c is so famous for?
I keep thinking how useful it would be to have embedded assembly in a python environment (a bit like 6502 asm in BBC Basic).
3:20 "Step 1... run this command". I can't read any of that. Is it written down somewhere? Out of curiosity, how big was the monitor used to make this, and what resolution was it set to?
Thank you for your efforts, very nice video 👍
Many thanks!
I need your help in this ARM ASSEMBLY ASSIGNMENT PL
What is he writing the code in for it to compile? I've searched all over the internet and everything is either wrong, outdated, missing, or for a OS that I'm not using.
why the null terminator if we pass the length of the string?!
Good catch, its just good practice in my opinion, but you're right its not necesary.
@@LowLevelTV I need your help in one ARM assembly coding assignment pl
RISC = Reduced Instruction Set Computer
why not use ld to link the object file instead of using gcc ?
Loved this video, excellent for beginners like myself...hoping you add more on ARM assembly
I need you help in one Arm assembly assignment.
Amazing video 😍
Thanks 🤗
I need your help in one ARM assembly coding assignment pl
great work keep it up.
Thank you! Did you figure out your compilation issue?
@@LowLevelTV Yea I did. All I had to do is specify the location of arm-linux-gnueabi with -L
what about leg assembly?
Very clearly and comprehensively presented, good job!
The volume was a bit low, though.
Excelent tutorial :)
Thanks great video but quick questions:
What environment IDE are you using ?
What tools (opensource) do you recommend to use the compiler/drbuger in GUI mode ?
I’m currently using docker for ARM/asm-32bit but have problem Docker blocks the debugger GDB, so I’m testimg a GDB SERVER with a C.H.I.P. Online, have 38 students not all have Rpi so we virtualization QEMU, but is a pain working GUI IDE on 1/8 of the screen
So thats why the questions!
I need your help in one ARM assembly coding assignment pl
Like Fireship said in one of their videos when talking about machine code: _"if we go up one level, we get some syntactic sugar"_
I was unable to install 'gcc-arm-linux-gnueabi' using 'apt' with the error 'No installation candidate'.
Spent 20 minutes or so searching for alternate packages only to realize 'apt-get' was all I needed.
I've done a fair bit of C with STM32, been wanting to explore writing some raw assembly for it since I have a ton of STM32s lying around with nothing to do. It just pains me that ARM syntax is right-to-left like NASM. AT&T syntax is way more intuitive to me, but oh well, not that big of a deal :b
this dude fulfiled his promise.. This vid is 15 min exact
Update to my last comment
Thanks to @simvalue
changed " mov r0, #0x01 " -to- " mov x0, #0x01 " no error message
Can you please explain in a tutorial, whats happening?
Thank You.
Sure! This means you’re running this code on a 64bit arm processor, where r0 is referred to as x0. Im happy you were able to solve this!
@@LowLevelTV
cool, just watching AARCH64 video, spells it all out. Cheers, thank you.
What a compiler do you use?
Thank you so so much, You are the best !!!!
No problem 😊
Hey, how are u searching in command history? i used to do history | grep something, but ur way looks better, thanks:D
Ctrl+R for reverse search :)
@@LowLevelTV thanks!
👍👍, Thanks a lot.
One thing I don’t understand is: Why do you move #0x1 into r7 at the start of the program? Isn’t this the syscall for exit?
Thank you for great video.
Just add: that arm executable could run on x86 linux without calling `qemu-arm' directly,
via binfmt_misc mechanism:
% uname -p
x86_64
% file 001.elf
001.elf: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, not stripped
% ./001.elf
zsh: exec format error: ./001.elf
% sudo apt install qemu-user-static
...
% ./001.elf
Hello, World
% hostnamectl status | tail -3
Operating System: Ubuntu 21.04
Kernel: Linux 5.11.0-25-generic
Architecture: x86-64
Can someone help me i tried to install the package but it said unable to locate package and i dont know what to do
"we assembled our assembly into machine code. We compiled it into a runable .elf" I don't understand the last part. I though compilers also output machine code. What's the difference between compiler output(ed) machine code and the elf?
Question: if you are using qemu, shouldn't you be running this code as a barebones machine? Why can you use Linux syscalls?
What is a good program to modify / compile arm Embedded. .Pkg files
Great tutorial, the only thing that is confusing for me, is why length of message string is equal 13 not 14? From the way you count, I assume that you interpret "
" as string of length 1, but why is that? Thanks for help in advance :)
Ah, I probably should have explained this a little bit.
When you see \ followed by a character in a string, that's called an "escape character". Escape characters are used to represent characters that the keyboard cannot type or that would otherwise be misrepresented if typed manually. When the assembler interprets that string, it treats the sequence
as ONE character, to represent the enter key.
I hope that makes sense. Thanks for watching!
@@LowLevelTV Yes it does, i'm familiar with programming in c and c++, but for some reason I thought that assembler is more ... I don't know, literal? anyway, thanks :)
@@LowLevelTV what about the null terminator though?
@@AmanSingh-sp6bi i expect it is not needed, gave the length to ldr action
@@MehOccor The most literal thing out there - is machine code
something wrong in apr 8, 7:22 pst,
"This video is unavailable on this device."
Thank you so much for telling me this. Something broke the video, your comment helped me fixed it :)
@@LowLevelTV recommending your channel to my students we are using ARM with docker (but Docker with Gdb don’t work) so I’m checking if I put a GDB server online (not secure) but students struggle to “view the inside”. Recommend a GDB (with colors) in next future video
can someone explain the funny number 65 in embedded systems he brought up right at the end of the video?
Cool !
got "hello.asm:7: Error: operand 1 must be an integer register -- `mov r0,#4'" otherwise
I thought RISC means reduced instruction set computer
Anyone know if this will work on ARM64? I am just starting to learn the world of architectures and Assembly language for a CS course I am taking.
I will try to do it on my smartphone since it's my only arm based machine
The weirdest part about trying to follow is "oh, my windows doesn't have sudo apt get arm or other assembly packages and doesn't know what to do with .elf even though with normal assembly it compiles".
how could i do this on windows
Also, im doing this on an AMD CPU, will the command work??
Is this GAS(GNU Assembler) for ARM?
What program are you using to run code?
Under the hood the loader knows to invoke QEMU, which is the emulator program making the ARM program run.