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Matt Mascarenhas 2018-04-24 20:37:33 +01:00
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[video member=miotatsu stream_platform=twitch project=riscy medium=research title="Playing with a Fedora chroot & Ion on the HiFive Unleashed" vod_platform=youtube id=AHH-KfjJn_s annotator=Miblo]
[0:13][Begin to recap and set the stage for the day][:speech]
[0:17][@riskyfive][\\o/]
[0:39][@riskyfive][Hmm, I can't see my own text]
[1:19][@riscyfive][Ah, any feedback on the podcast? Boring? Confusing?]
[4:28][Plug @riscyfive's podcast 'Why So Anemic'[ref
site="Twitter: @coredumppodcast"
page="Episode 1: Why So Anemic?"
url=https://twitter.com/coredumppodcast/status/985931647437672448]]
[4:42][@riskyfive][Well, I want(ed) to keep my mind open. If I had found out (or I later find out) that the OOP-style modeling was the best option then so be it. I just want to get at the truth, I don't have a camp]
[5:30][@riskyfive][People at DConf 2016 thought I was Italian, due to the way I talk]
[6:11][Determine to continue doing stuff with the HiFive Unleashed, [ref
site="SiFive Forums"
page="Is there a more complete system image for Unleashed board?"
url=https://forums.sifive.com/t/is-there-a-more-complete-system-image-for-unleashed-board/1146]]
[10:49][Explain the process of installing Fedora onto the HiFive Unleashed,[ref
site="Fedora Project Wiki"
page="Architectures/RISC-V"
url=https://fedoraproject.org/wiki/Architectures/RISC-V] noting the block size in Arch Linux's example dd invocation[ref
site="Arch Wiki"
page="USB flash installation media"
url=https://wiki.archlinux.org/index.php/USB_flash_installation_media#In_GNU.2FLinux]]
[15:42][@riskyfive][By the way, you probably don't have video on your RISC-V system. SiFive used an adapter FPGA board for their demo. I wanted to share with you and your viewers that you can buy the Nexys Video (the bigger one recommended for ~Bitwise) using an academic discount. I ordered one. We can then later collaborate to get HDMI output using one, or something like that. I can help you with that]
[17:02][Continue to explain the dd part of the installation process]
[17:44][@riskyfive][You can even add MP4 encoding in the FPGA itself. No need for OBS]
[18:38][Continue to explain the installation process]
[19:08][@riskyfive][You need more Patreons. I'll try to promote you[ref
site=Patreon
page="miotatsu is creating RISCY BUSINESS"
url=https://www.patreon.com/miotatsu][ref
site=Gumroad
page="RISCY BUSINESS: Programming a handmade tool-chain for RISC-V live on Twitch"
url=https://gumroad.com/riscy]]
[20:49][Finish up explaining the setup process, including building the Ion compiler from ~bitwise and having it run out of the box!]
[23:00][Don the antistatic wristband and plug in the HiFive Unleashed][:admin]
[24:03][@riskyfive][Where are you plugging the band?]
[25:03][@riskyfive][The "duct tape" method. Good engineering]
[25:23][Read 5.3. Knobs on the HiFive Unleashed[ref
site="SiFive Developers"
page="HiFive Unleashed Getting Started Guide"
url=https://www.sifive.com/documentation/boards/hifive-unleashed/hifive-unleashed-getting-started-guide/]]
[27:02][@riskyfive][I've worked with $5K boards at Siemens without grounding and they never exhibited problems. After that I never cared too much]
[28:47][@riskyfive][That actually was very surprising because I kept getting shocked due to the static discharges at that laboratory (when touching the server racks). But the hardware itself never complained]
[30:25][@riskyfive][No, there was a ground. But we were busy and lazy! Maybe that was the trick: I kept discharging myself unintentionally!]
[30:42][Plug in and power up the board][:admin]
[31:53][@riskyfive][Yeah, I pretty much only have grounded plugs in the kitchen]
[32:18][Connect to the HiFive Unleashed and setup the environment][:admin]
[36:45][@riskyfive][It seems the cool kids use tmux these days]
[37:09][Delete our test files related to ion][:admin]
[40:01][@riskyfive][Try: $ shopt | grep checkwinsize]
[41:05][Compile ion, :run generate_test.py, show the resulting Ion code in test3.ion, run ion on that file to produce test3.c]
[43:54][Point out that qemu[ref
site=QEMU
url=https://www.qemu.org/] may provide the closest means to follow along, without having to invest in a HiFive Unleashed][:speech]
[45:30][Try to :run ion on test2.ion and then gcc on the resulting test2.c file]
[46:54][Try to :run ion on test1.ion and then gcc on the resulting test1.c file, to see printouts and input totally working][:"input handling"]
[48:39][Read through test1.ion]
[51:45][:Run test1 to provide the first demo of Ion code compiled to and running on RISC-V]
[52:50][Note @Miblo's thought to use readelf while he wrote annotations for ~Bitwise][:speech]
[55:12][:Run objdump on test2]
[55:44][Determine to run objdump on hello][:speech]
[56:51][@riskyfive][I use readelf all the time for my empire RISC-V port]
[57:03][Continue to figure out how to unfreeze the screen][:admin]
[57:57][@riskyfive][Ctrl-q?]
[58:21][Note the annoyance of the XOFF ASCII character and screen's default keybinding for it][:rant]
[59:39][@riskyfive][Yeah, very annoying. Arguably it's just it not ignoring the ASCII characters (XON / XOFF) that you actually typed]
[1:00:30][Copy hello into the (Fedora) chroot environment][:admin]
[1:01:06][@riskyfive][Yeah, but when you type Ctrl-something it emits certain ASCII characters that are control characters, like stop transmitting (freeze)]
[1:03:35][:Run objdump on our elf64-littleriscv hello]
[1:04:50][Consider trying the hula RISC-V "Hello, world!" on our HiFive Unleashed[ref
site=GitHub
page="riscy-business / hula"
url=https://github.com/riscy-business/hula]]
[1:05:37][@riskyfive][That's just what the ASCII character 19 means: stop transmitting. And when you type Ctrl-s you type that character. The real question is, who thought it was a good idea to transmit control information in-band with the content. That is, if you cat a .txt file that contains that character you're screwed]
[1:07:14][@riskyfive][You see, it used to be that terminals had dedicated wires for control. But then $ happened]
[1:07:31][:Rant on screen having kept legacy baggage around]
[1:09:31][Continue to compare the objdump of hello with hula[ref
site=GitHub
page="riscy-business / hula"
url=https://github.com/riscy-business/hula]]
[1:10:02][@riskyfive][With dedicated wires you don't need in-band control characters]
[1:10:43][@riskyfive][No, there was a message missing in between]
[1:10:52][Compare hula's "write" code with the hello objdump]
[1:11:55][@riskyfive][The Ctrl-z was an example of how the shell has the same problem]
[1:13:11][Note that the hello objdump may not show scall]
[1:14:08][@riskyfive][I agree it's braindead. But just think this: the initial Ctrl-a just means that you want the sequence Ctrl-a q to pass as a Ctrl-q to the target process. It's not a list of Ctrl-a commands, it just a generic escape]
[1:14:34][@riskyfive][scall -> ecall]
[1:15:14][@riskyfive][It's the old name]
[1:15:16][Wonder if the objdump is not using system calls, and that it's a lot bigger than hula]
[1:16:19][@riskyfive][Notice: disassembly of XXX (not .text) section]
[1:16:42][Hunt for a7 in the objdump because that is where you put the syscall number in RISC-V]
[1:18:11][@riskyfive][You can do a readelf of the binary in your main system]
[1:18:27][Consult man readelf]
[1:19:25][:Run readelf -a hello]
[1:20:21][Read through the readelf of hello]
[1:21:40][@riskyfive][Maybe just try GDB with the binary?]
[1:22:13][Continue to read through the readelf of hello]
[1:22:31][@riskyfive][That's why you need the JTAG port]
[1:22:46][Return to the objdump of hello]
[1:23:42][@riskyfive][The system calls are probably wrapped in libc functions]
[1:23:55][Notice the mentions of "libc" in the hello objdump]
[1:24:49][@riskyfive][I think the ligc_start_main is just a red herring. Notice the offset is different between different __libc_start_main lines]
[1:25:58][Notice "libc_start_main" in the hello objdump]
[1:27:59][Consult the objdump of test1, to see that its symbols are correctly resolved]
[1:30:39][Call it a day][:speech]
[/video]