ruxpin

Ruxpinos

Dimulai 1 Maret 2022

Upaya membuat sistem operasi dalam karat untuk raspberry pi 3. Karena kendala waktu, saya telah memprioritaskan mendapatkan sesuatu yang berfungsi alih-alih mencoba ide-ide baru, jadi untuk saat ini ini adalah OS monolitik dengan API seperti Unix, tetapi saya mungkin mengubahnya di masa depan. Saya sebagian besar menyalin apa yang telah saya lakukan untuk Gloworm OS yang ditulis dalam C.

Saat ini, ia memiliki dukungan untuk memori virtual, dengan alokasi halaman sesuai permintaan, tetapi belum ada dukungan untuk bertukar memori ke disk. Ini memiliki sistem file virtual dengan dukungan untuk sistem file Ext2, serta beberapa sistem file dalam memori. Ini mendukung banyak proses dengan switching konteks yang dipicu oleh timer sistem, tetapi belum mendukung banyak utas.

Saat ini, hanya ada driver konsol (subsistem TTY) dan driver kartu SD/EMMC (subsistem perangkat blok). Subsistem driver blok menyediakan blok bufcache ke cache yang dibaca dari disk oleh sistem file. Blok yang dipinjam karena dapat berubah menjadi kotor dan akan ditulis kembali di blok berikutnya. Dukungan penulisan EXT2 belum diuji dengan baik, jadi komitmen dinonaktifkan untuk saat ini.

Aplikasi dapat ditulis dalam karat dan dikompilasi dengan perpustakaan yang disertakan, yang menggunakan instruksi AARCH64 SVC untuk melakukan panggilan sistem ke OS. Saat ini mendukung operasi file dasar, serta exit , fork , dan exec . OS dapat secara langsung memuat binari ELF yang diproduksi oleh kargo sebagai aplikasi, dan menjalankannya. Program shell sederhana (diluncurkan oleh kernel setelah inisialisasi) dan perintah ls tersedia, tetapi hanya pada tahap bukti konsep.

Menyusun

OS terdiri dari kernel dan beberapa aplikasi yang semuanya dikompilasi secara terpisah. Aplikasi dapat dimuat ke partisi EXT2, yang dapat dibaca oleh kernel, tetapi kernel perlu dimuat secara terpisah, sehingga tidak termasuk dalam gambar.

Biasanya, ketika raspberry pi boots, firmware mencari partisi lemak pada kartu microSD yang berisi file kernel8.img , yang kemudian dimuat pada alamat 0x80000 dan dijalankan. Setelah kernel berjalan, kemudian dapat memasang partisi lain untuk digunakan sebagai sistem file root. Saat berjalan di QEMU, gambar kernel dilewatkan pada baris perintah, bersama dengan nama file dari gambar disk yang berisi partisi EXT2.

Makefile disediakan di root proyek untuk membangun gambar disk EXT2. Untuk membuatnya lebih mudah untuk menguji kode di QEMU atau pada perangkat keras, itu membuat gambar disk yang terlihat sama dengan kartu microSD (yaitu. Partisi lemak ditambah partisi EXT2). Saat menggunakan QEMU, partisi lemak diabaikan.

Untuk membuat gambar, dari komputer Linux yang dijalankan:

make create-image
make load-image

Ini akan membuat file gambar 4GB baru, gunakan mkfs.ext2 untuk membuat sistem file baru di dalamnya, pasang sebagai perangkat loopback di <project>/build , dan kemudian menyusun dan memuat aplikasi ke dalamnya. Ini juga menyalin tabel partisi kode-keras ke dalam gambar, yang mereplikasi partisi yang digunakan oleh perangkat keras.

Setelah gambar telah dibuat, kernel dapat dikompilasi dan dijalankan di QEMU, menggunakan:

 cd config/raspberrypi3/
make
./qemu.sh

Untuk menjalankan Raspberry Pi saat ini membutuhkan konsol serial USB. Saya menggunakan program Miniload dari tutorial Rust Raspberry Pi OS untuk mengidap kernel di atas port serial. Dimungkinkan untuk memasukkan gambar kernel yang dikompilasi ( ruxpin.img ) ke dalam partisi boot dari file yang dibuat dan menulisnya ke disk, tetapi saya belum mengujinya.

Output contoh

Output berikut disalin dari konsol saat dijalankan di QEMU. Ini memiliki banyak pesan debug untuk menunjukkan apa yang terjadi. Dimulai dengan mengatur knel heap dan memori halaman, mendaftarkan jenis sistem file, menginisialisasi driver perangkat, dan memasang partisi root ext2. Kemudian melakukan sejumlah tes untuk memeriksa fungsionalitas sistem file dasar, diikuti dengan meluncurkan proses pertama (shell). Perintah kemudian diketik, ditampilkan antara "<>", yang meluncurkan program ls , mencetak daftar file dan direktori di / , dan kemudian keluar kembali ke prompt shell.

 starting kernel...
kernel heap: using 0x200000, size 14MiB
virtual memory: using region at PhysicalAddress(0x1000000), size 240 MiB, pages 61438
interrupts: initializing generic arm interrupt controller
fs: registering filesystem tmpfs
fs: registering filesystem devfs
fs: registering filesystem ext2
console: initializing
sd: initializing
sd: found partition 0 at 2000, 256 MiB
sd: found partition 1 at 82000, 740 MiB
fs: mounting ext2 at /, device Some(DeviceID(0, 2))
ext2: magic number ef53, block size 4096
ext2: total blocks 982016, total inodes 245760, unallocated blocks: 963991, unallocated inodes: 245742
ext2: features compat: 38, ro: 3, incompat: 2
ext2: allocating inode 13
fs: mounting devfs at /dev, device None
ext2: looking for "dev", found inode 13

Running some hardcoded tests before completing the startup

Mounting the tmpfs filesystem (simple in-memory file system)
ext2: allocating inode 14
fs: mounting tmpfs at /tmp, device None
ext2: looking for "tmp", found inode 14

Creating a directory and a file inside of it
ext2: allocating inode 15
ext2: looking for "testdir", found inode 15
ext2: allocating inode 16
ext2: allocating block 761 in group 0
ext2: allocating block 762 in group 0
ext2: writing to block 762
Read file 14: This is a test

Opening the console device file and writing to it
ext2: looking for "dev", found inode 13
the device file can write

Opening the testapp binary through the vfs interface and reading some data
ext2: looking for "bin", found inode 32769
ext2: looking for "testapp", found inode 32770
read in 1024 bytes
0xffff00000007f790: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
0xffff00000007f7a0: 02 00 b7 00 01 00 00 00 70 29 21 00 00 00 00 00 
0xffff00000007f7b0: 40 00 00 00 00 00 00 00 d0 c8 0d 00 00 00 00 00 
0xffff00000007f7c0: 00 00 00 00 40 00 38 00 04 00 40 00 10 00 0e 00 
0xffff00000007f7d0: 06 00 00 00 04 00 00 00 40 00 00 00 00 00 00 00 
0xffff00000007f7e0: 40 00 20 00 00 00 00 00 40 00 20 00 00 00 00 00 
0xffff00000007f7f0: e0 00 00 00 00 00 00 00 e0 00 00 00 00 00 00 00 
0xffff00000007f800: 08 00 00 00 00 00 00 00 01 00 00 00 04 00 00 00 
0xffff00000007f810: 00 00 00 00 00 00 00 00 00 00 20 00 00 00 00 00 
0xffff00000007f820: 00 00 20 00 00 00 00 00 60 09 00 00 00 00 00 00 
0xffff00000007f830: 60 09 00 00 00 00 00 00 00 00 01 00 00 00 00 00 
0xffff00000007f840: 01 00 00 00 05 00 00 00 60 09 00 00 00 00 00 00 
0xffff00000007f850: 60 09 21 00 00 00 00 00 60 09 21 00 00 00 00 00 
0xffff00000007f860: d8 31 00 00 00 00 00 00 d8 31 00 00 00 00 00 00 
0xffff00000007f870: 00 00 01 00 00 00 00 00 51 e5 74 64 06 00 00 00 
0xffff00000007f880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007f890: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007f8a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007f8b0: 63 61 6c 6c 65 64 20 60 52 65 73 75 6c 74 3a 3a 
0xffff00000007f8c0: 75 6e 77 72 61 70 28 29 60 20 6f 6e 20 61 6e 20 
0xffff00000007f8d0: 60 45 72 72 60 20 76 61 6c 75 65 00 00 00 00 00 
0xffff00000007f8e0: 60 09 21 00 00 00 00 00 08 00 00 00 00 00 00 00 
0xffff00000007f8f0: 08 00 00 00 00 00 00 00 20 10 21 00 00 00 00 00 
0xffff00000007f900: 60 09 21 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007f910: 01 00 00 00 00 00 00 00 94 28 21 00 00 00 00 00 
0xffff00000007f920: 61 20 72 65 61 6c 6c 79 20 63 6f 6f 6c 20 6d 65 
0xffff00000007f930: 73 73 61 67 65 20 74 68 61 74 20 49 27 64 20 6c 
0xffff00000007f940: 69 6b 65 20 74 6f 20 73 65 65 00 00 00 00 00 00 
0xffff00000007f950: 90 01 20 00 00 00 00 00 2a 00 00 00 00 00 00 00 
0xffff00000007f960: 73 72 63 2f 6d 61 69 6e 2e 72 73 00 00 00 00 00 
0xffff00000007f970: d0 01 20 00 00 00 00 00 0b 00 00 00 00 00 00 00 
0xffff00000007f980: 0c 00 00 00 05 00 00 00 0a 2f 6d 6e 74 2f 74 65 
0xffff00000007f990: 73 74 32 00 00 00 00 00 d0 01 20 00 00 00 00 00 
0xffff00000007f9a0: 0b 00 00 00 00 00 00 00 0e 00 00 00 51 00 00 00 
0xffff00000007f9b0: d0 01 20 00 00 00 00 00 0b 00 00 00 00 00 00 00 
0xffff00000007f9c0: 10 00 00 00 28 00 00 00 d0 01 20 00 00 00 00 00 
0xffff00000007f9d0: 0b 00 00 00 00 00 00 00 11 00 00 00 19 00 00 00 
0xffff00000007f9e0: d0 01 20 00 00 00 00 00 0b 00 00 00 00 00 00 00 
0xffff00000007f9f0: 11 00 00 00 2a 00 00 00 d0 01 20 00 00 00 00 00 
0xffff00000007fa00: 0b 00 00 00 00 00 00 00 12 00 00 00 11 00 00 00 
0xffff00000007fa10: d0 01 20 00 00 00 00 00 0b 00 00 00 00 00 00 00 
0xffff00000007fa20: 17 00 00 00 38 00 00 00 d0 01 20 00 00 00 00 00 
0xffff00000007fa30: 0b 00 00 00 00 00 00 00 1a 00 00 00 10 00 00 00 
0xffff00000007fa40: 72 65 61 64 20 69 6e 20 00 00 00 00 20 00 00 00 
0xffff00000007fa50: 4e 6f 74 41 46 69 6c 65 d0 01 20 00 00 00 00 00 
0xffff00000007fa60: 0b 00 00 00 00 00 00 00 1c 00 00 00 31 00 00 00 
0xffff00000007fa70: d0 01 20 00 00 00 00 00 0b 00 00 00 00 00 00 00 
0xffff00000007fa80: 1d 00 00 00 31 00 00 00 64 6f 6e 65 00 00 00 00 
0xffff00000007fa90: f8 02 20 00 00 00 00 00 04 00 00 00 00 00 00 00 
0xffff00000007faa0: d0 01 20 00 00 00 00 00 0b 00 00 00 00 00 00 00 
0xffff00000007fab0: 2d 00 00 00 05 00 00 00 65 78 65 63 75 74 69 6e 
0xffff00000007fac0: 67 20 73 65 6c 66 00 00 28 03 20 00 00 00 00 00 
0xffff00000007fad0: 0e 00 00 00 00 00 00 00 d0 01 20 00 00 00 00 00 
0xffff00000007fae0: 0b 00 00 00 00 00 00 00 24 00 00 00 15 00 00 00 
0xffff00000007faf0: 46 69 6c 65 53 69 7a 65 54 6f 6f 4c 61 72 67 65 
0xffff00000007fb00: 4e 6f 53 75 63 68 46 69 6c 65 73 79 73 74 65 6d 
0xffff00000007fb10: 2f 6d 6e 74 2f 62 69 6e 2f 74 65 73 74 61 70 70 
0xffff00000007fb20: 54 6f 6f 4d 61 6e 79 46 69 6c 65 73 4f 70 65 6e 
0xffff00000007fb30: 72 61 6e 67 65 20 65 6e 64 20 69 6e 64 65 78 20 
0xffff00000007fb40: 50 0e 21 00 00 00 00 00 08 00 00 00 00 00 00 00 
0xffff00000007fb50: 08 00 00 00 00 00 00 00 90 0f 21 00 00 00 00 00 
0xffff00000007fb60: 60 0e 21 00 00 00 00 00 50 0f 21 00 00 00 00 00 
0xffff00000007fb70: 00 05 0a 0f 14 19 1e 23 28 2d 32 37 3c 41 46 4b 
0xffff00000007fb80: 50 55 5a 5f 64 69 6e 73 78 7d 82 87 8c 91 63 61 

Opening a new file and writing some data into it
ext2: allocating inode 17
ext2: allocating block 763 in group 0
ext2: writing to block 763

Reading back the data written previously
ext2: looking for "test2", found inode 17
0xffff00000007fba0: 74 68 69 73 20 69 73 20 73 6f 6d 65 20 74 65 73 
0xffff00000007fbb0: 74 20 64 61 74 61 00 00 00 00 00 00 00 00 00 00 
0xffff00000007fbc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007fbd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007fbe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007fbf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007fc00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
0xffff00000007fc10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 

Printing the contents of the root directory (ext2 mount)
reading dir . with inode 2
reading dir .. with inode 2
reading dir lost+found with inode 11
reading dir bin with inode 32769
reading dir test with inode 12
reading dir dev with inode 13
reading dir tmp with inode 14
reading dir testdir with inode 15
reading dir test2 with inode 17

Finished tests

loading the first processs (/bin/sh) from elf binary file
ext2: looking for "bin", found inode 32769
ext2: looking for "sh", found inode 32772
program segment 0: 6 4 offset: 40 v:200040 p:200040 size: e0
program segment 1: 1 4 offset: 0 v:200000 p:200000 size: 1870
program segment 2: 1 5 offset: 1870 v:211870 p:211870 size: 53c8
program segment 3: 6474e551 6 offset: 0 v:0 p:0 size: 0
ext2: looking for "dev", found inode 13
timer: initializing generic arm timer to trigger context switch
kernel initialization complete
scheduler: starting multitasking
Instruction or Data Abort caused by Access Flag at address 215a70 (allocating new page)
Instruction or Data Abort caused by Access Flag at address fffffff0 (allocating new page)
Instruction or Data Abort caused by Access Flag at address 21337c (allocating new page)
Instruction or Data Abort caused by Access Flag at address 212190 (allocating new page)

Starting shell...
Instruction or Data Abort caused by Access Flag at address 216c34 (allocating new page)
% <typing in ls>
Instruction or Data Abort caused by Access Flag at address 2140e8 (allocating new page)
executing /bin/ls
child pid is 3
clearing old process space
executing a new process
ext2: looking for "bin", found inode 32769
ext2: looking for "ls", found inode 32774
program segment 0: 6 4 offset: 40 v:200040 p:200040 size: e0
program segment 1: 1 4 offset: 0 v:200000 p:200000 size: 730
program segment 2: 1 5 offset: 730 v:210730 p:210730 size: 2cb8
program segment 3: 6474e551 6 offset: 0 v:0 p:0 size: 0
ext2: looking for "dev", found inode 13
Instruction or Data Abort caused by Access Flag at address 212220 (allocating new page)
Instruction or Data Abort caused by Access Flag at address fffffff0 (allocating new page)
ext2: looking for ".", found inode 2
Instruction or Data Abort caused by Access Flag at address 2133e4 (allocating new page)
Instruction or Data Abort caused by Access Flag at address 2110e4 (allocating new page)
.
..
lost+found
bin
test
dev
tmp
testdir
test2
Exiting process 3
%