suhas-pai / operating-system-old

operating-system

An operating system written in C17 (gnu17), for x86_64, aarch64, and riscv64.

So far, only the kernel is being worked on.

Features

The kernel has the following implemented:

• UART drivers; uart8250 on x86_64, riscv64 and pl011 on aarch64
• Physical Memory Buddy Allocator using a vmemmap of struct page
• General memory allocation with kmalloc() using a slab allocator
• RTC (google,goldfish-rtc on riscv64) and LAPIC Timer, HPET on x86_64
• Keyboard (ps2) driver
• Parsing ACPI Tables and Flattened Device Tree (when available)
• Local APIC and I/O APIC
• PCI(e) Device Initialization with drivers

The following is currently being worked on.

• AHCI, SATA, IDE controllers to read disk
• VirtIO drivers to detect devices when PCI(e) isn't available (as is the case on riscv64)
• Filesystem following VFS model
• Network Card drivers
• SMP support to run multiple cores
• Processes, threads, and scheduler to run tasks

In addition, this project has a broad standard library that includes:

• Abstract printf() formatter
  • Used to implement kprintf() and format_to_string() among many use cases
• Abstract strftime() formatter
  • Doesn't support timezones (atm)
  • Used to implement a very basic kstrftime()
• ASCII APIs
• Alignment APIs
  • Defines and provides general-purpose APIs to check for alignment
• Integer Conversion APIs
  • Can convert to and from strings, with the following configurable integer formats:
    • Binary (with 0b prefix)
    • Octal (with 0 or 0o prefix)
    • Decimal
    • Hexadecimal (with 0x prefix)
    • Alpbabetic (with 0a prefix)

Among many others

Running

operating-system currently supports the x86_64, aarch64 (arm64), and riscv64 architectures. x86_64 is the most feature complete, while arm64 and riscv64 are catching up

Several options are available to configure launching in QEMU:

• MEM to configure memory size (in QEMU units) (By Default 4G)
• SMP to configure amount of cpus (By Default 4)
• DEBUG to allow starting in QEMU's debugger mode (By default 0)
• CONSOLE to allow starting in QEMU's console mode (By default 0)

To build and run, only clang and ld.lld are needed (from LLVM). Run using:

make clean && make run ARCH=<arch> MEM=<mem> SMP=<smp>