Custom-Operating-System/boot/riscv64/prekernel/main.c

#include "drivers/uart.h"
#include "vm.h"
#include <libboot/abi/memory.h>
#include <libboot/devtree/devtree.h>
#include <libboot/elf/elf_lite.h>
#include <libboot/log/log.h>
#include <libboot/mem/alloc.h>
#include <libboot/mem/mem.h>

#define DEBUG_BOOT
#define EARLY_FB

extern uint32_t EMBED_DEVTREE_START[];
extern uint32_t EMBED_DEVTREE_END[];

extern void jump_to_s_mode(uintptr_t);
extern void jump_to_kernel(void*, uintptr_t);
static void* bootdesc_paddr;
static void* bootdesc_vaddr;
static size_t kernel_vaddr = 0;
static size_t kernel_paddr = 0;
static size_t kernel_size = 0;

#define LAUNCH_SERVER_PATH "/System/launch_server"

static int alloc_init()
{
    devtree_entry_t* dev = devtree_find_device("ram");
    if (!dev) {
        log("Can't find RAM in devtree");
        while (1) { };
    }

    extern uint32_t RAWIMAGE_END[];
    uintptr_t start_addr = ROUND_CEIL((uint64_t)RAWIMAGE_END, page_size());
    size_t free_space = dev->region_size - (start_addr - dev->region_base);
    malloc_init((void*)start_addr, free_space);

#ifdef DEBUG_BOOT
    log("malloc inited %llx %llx", start_addr, free_space);
#endif
    return 0;
}

static size_t memory_layout_size()
{
    return 0 + 1; // Including the trailing element.
}

static int preserve_alloc_init(size_t kernsize)
{
    const size_t devtreesize = ROUND_CEIL(devtree_size(), page_size());
    const size_t memmap = ROUND_CEIL(memory_layout_size() * sizeof(memory_layout_t), page_size());
    const size_t bootargsstruct = ROUND_CEIL(sizeof(boot_args_t), page_size());
    const size_t bootargssize = devtreesize + memmap + bootargsstruct;

    // 32 tables should be enough for initial mappings.
    const size_t prekernelvmsize = 32 * page_size();
    const size_t total = ROUND_CEIL(kernsize + bootargssize + prekernelvmsize, page_size());

    return palloc_init(total, 2 << 20);
}

static memory_boot_desc_t memory_boot_desc_init()
{
    devtree_entry_t* dev = devtree_find_device("ram");
    if (!dev) {
#ifdef EARLY_FB
        log("Can't find RAM in devtree");
#endif
        while (1) { };
    }

    memory_boot_desc_t res;
    const size_t memlayout_size = memory_layout_size();
    memory_layout_t* mem_layout_paddr = palloc_aligned(memlayout_size * sizeof(memory_layout_t), page_size());

    // Init of trailing element.
    mem_layout_paddr[memlayout_size - 1].flags = MEMORY_LAYOUT_FLAG_TERMINATE;
    memory_layout_t* mem_layout_vaddr = paddr_to_vaddr(mem_layout_paddr, kernel_paddr, kernel_vaddr);
#if defined(DEBUG_BOOT) && defined(EARLY_FB)
    log("initing MEMLAYOUT %lx of %d elems", mem_layout_vaddr, memlayout_size);
#endif

    res.ram_base = dev->region_base;
    res.ram_size = dev->region_size;
    res.reserved_areas = mem_layout_vaddr;
    return res;
}

static void load_kernel(void* kenrelstart)
{
    kernel_size = elf_get_kernel_size(kenrelstart);
    kernel_size = ROUND_CEIL(kernel_size, page_size());

    int err = preserve_alloc_init(kernel_size);
    if (err) {
#ifdef EARLY_FB
        log("add assert");
#endif
        while (1) { }
    }

    int res = elf_load_kernel(kenrelstart, kernel_size, &kernel_vaddr, &kernel_paddr);
#if defined(DEBUG_BOOT) && defined(EARLY_FB)
    log("kernel %lx %lx %lx", kernel_vaddr, kernel_paddr, kernel_size);
#endif

    void* odt_paddr = palloc_aligned(devtree_size(), page_size());
    memcpy(odt_paddr, devtree_start(), devtree_size());
    void* odt_vaddr = paddr_to_vaddr(odt_paddr, kernel_paddr, kernel_vaddr);
#if defined(DEBUG_BOOT) && defined(EARLY_FB)
    log("copying ODT %lx -> %lx of %d", devtree_start(), odt_vaddr, devtree_size());
#endif

    boot_args_t boot_args;
    boot_args.vaddr = kernel_vaddr;
    boot_args.paddr = kernel_paddr;
    boot_args.kernel_data_size = 0x0; // Sets up later
    boot_args.mem_boot_desc = memory_boot_desc_init();
    boot_args.devtree = odt_vaddr;
    boot_args.fb_boot_desc.vaddr = 0; // Marking fb as invalid.
    memcpy(boot_args.init_process, LAUNCH_SERVER_PATH, sizeof(LAUNCH_SERVER_PATH));

    bootdesc_paddr = palloc_aligned(sizeof(boot_args), page_size());
    memcpy(bootdesc_paddr, &boot_args, sizeof(boot_args));
    bootdesc_vaddr = paddr_to_vaddr(bootdesc_paddr, kernel_paddr, kernel_vaddr);
#if defined(DEBUG_BOOT) && defined(EARLY_FB)
    log("copying BOOTDESC %lx -> %lx of %d", &boot_args, bootdesc_vaddr, sizeof(boot_args));
#endif
}

static int enable_timer()
{
    devtree_entry_t* dev = devtree_find_device("rv64timer");
    if (!dev) {
        log("Can't find timer in devtree");
        return 1;
    }

    struct timer_scratch_mem {
        uint64_t entries[5];
    };
    struct timer_scratch_mem* scratch = palloc_aligned(sizeof(struct timer_scratch_mem), page_size());

    size_t hartid = 0;
    volatile uint64_t* mtime = (uint64_t*)(dev->region_base + 0xBFF8);
    volatile uint64_t* mtimecmp = (uint64_t*)(dev->region_base + 0x4000 + 8 * hartid);

    size_t interval = 10000000 / 125;
    *mtimecmp = *mtime + interval;
    scratch->entries[3] = (uint64_t)mtimecmp;
    scratch->entries[4] = interval;

    extern void setup_timer_m_mode(void*);
    setup_timer_m_mode(scratch);
    return 0;
}

void main(uintptr_t base)
{
    devtree_init((void*)EMBED_DEVTREE_START, (uint64_t)EMBED_DEVTREE_END - (uint64_t)EMBED_DEVTREE_START);
    uart_init();
    log_init(uart_write);
    alloc_init();

    extern uint32_t EMBED_KERNEL_START[];
    load_kernel((void*)(EMBED_KERNEL_START));

    enable_timer();
    jump_to_s_mode(base);
}

int main_s_mode(uintptr_t base)
{
    vm_setup(base, bootdesc_paddr);

#ifdef DEBUG_BOOT
    log("Preboot done: booting to OS@%llx", ((boot_args_t*)bootdesc_vaddr)->vaddr);
#endif

    ((boot_args_t*)bootdesc_vaddr)->kernel_data_size = ROUND_CEIL(palloc_used_size(), page_size());
    jump_to_kernel((void*)bootdesc_vaddr, ((boot_args_t*)bootdesc_vaddr)->vaddr);
    return 0;
}