pluto/src/kernel/mem.zig

const multiboot = @import("multiboot.zig");

pub const MemProfile = struct {
    vaddr_end: [*]u8,
    vaddr_start: [*]u8,
    physaddr_end: [*]u8,
    physaddr_start: [*]u8,
    mem_kb: u32,
    fixed_alloc_size: u32,
};

// The virtual/physical start/end of the kernel code
extern var KERNEL_VADDR_END: *u32;
extern var KERNEL_VADDR_START: *u32;
extern var KERNEL_PHYSADDR_END: *u32;
extern var KERNEL_PHYSADDR_START: *u32;

// The size of the fixed allocator used before the heap is set up. Set to 1MiB.
const FIXED_ALLOC_SIZE = 1024 * 1024;

pub fn init(mb_info: *multiboot.multiboot_info_t) MemProfile {
    return MemProfile{
        .vaddr_end = @ptrCast([*]u8, &KERNEL_VADDR_END),
        .vaddr_start = @ptrCast([*]u8, &KERNEL_VADDR_START),
        .physaddr_end = @ptrCast([*]u8, &KERNEL_PHYSADDR_END),
        .physaddr_start = @ptrCast([*]u8, &KERNEL_PHYSADDR_START),
        // Total memory available including the initial 1MiB that grub doesn't include
        .mem_kb = mb_info.mem_upper + mb_info.mem_lower + 1024,
        .fixed_alloc_size = FIXED_ALLOC_SIZE,
    };
}