Virtual memory & paging

[lunaix-os.git] / lunaix-os / arch / x86 / hhk.c

diff --git a/lunaix-os/arch/x86/hhk.c b/lunaix-os/arch/x86/hhk.c
new file mode 100644 (file)
index 0000000..c0e5f9a
--- /dev/null
+++ b/lunaix-os/arch/x86/hhk.c
@@ -0,0 +1,134 @@
+#include <arch/x86/boot/multiboot.h>
+#include <arch/x86/idt.h>
+#include <lunaix/mm/page.h>
+#include <lunaix/constants.h>
+
+#define PT_ADDR(ptd, pt_index)                       ((ptd_t*)ptd + (pt_index + 1) * 1024)
+#define SET_PDE(ptd, pde_index, pde)                 *((ptd_t*)ptd + pde_index) = pde;
+#define SET_PTE(ptd, pt_index, pte_index, pte)       *(PT_ADDR(ptd, pt_index) + pte_index) = pte;
+#define sym_val(sym)                                 (uintptr_t)(&sym)
+
+#define KERNEL_PAGE_COUNT           ((sym_val(__kernel_end) - sym_val(__kernel_start) + 0x1000 - 1) >> 12);
+#define HHK_PAGE_COUNT              ((sym_val(__init_hhk_end) - 0x100000 + 0x1000 - 1) >> 12)
+
+// use table #1
+#define PG_TABLE_IDENTITY           0
+
+// use table #2-4
+// hence the max size of kernel is 8MiB
+#define PG_TABLE_KERNEL             1
+
+// use table #5
+#define PG_TABLE_STACK              4
+
+// Provided by linker (see linker.ld)
+extern uint8_t __kernel_start;
+extern uint8_t __kernel_end;
+extern uint8_t __init_hhk_end;
+extern uint8_t _k_stack;
+
+void 
+_init_page(ptd_t* ptd) {
+    SET_PDE(ptd, 0, PDE(PG_PRESENT, ptd + PG_MAX_ENTRIES))
+    
+    // 对低1MiB空间进行对等映射（Identity mapping），也包括了我们的VGA，方便内核操作。
+    for (uint32_t i = 0; i < 256; i++)
+    {
+        SET_PTE(ptd, PG_TABLE_IDENTITY, i, PTE(PG_PREM_RW, (i << 12)))
+    }
+
+    // 对等映射我们的hhk_init，这样一来，当分页与地址转换开启后，我们依然能够照常执行最终的 jmp 指令来跳转至
+    //  内核的入口点
+    for (uint32_t i = 0; i < HHK_PAGE_COUNT; i++)
+    {
+        SET_PTE(ptd, PG_TABLE_IDENTITY, 256 + i, PTE(PG_PREM_RW, 0x100000 + (i << 12)))
+    }
+    
+    // --- 将内核重映射至高半区 ---
+    
+    // 这里是一些计算，主要是计算应当映射进的 页目录 与 页表 的条目索引（Entry Index）
+    uint32_t kernel_pde_index = PD_INDEX(sym_val(__kernel_start));
+    uint32_t kernel_pte_index = PT_INDEX(sym_val(__kernel_start));
+    uint32_t kernel_pg_counts = KERNEL_PAGE_COUNT;
+    
+    // 将内核所需要的页表注册进页目录
+    //  当然，就现在而言，我们的内核只占用不到50个页（每个页表包含1024个页）
+    //  这里分配了3个页表（12MiB），未雨绸缪。
+    for (uint32_t i = 0; i < PG_TABLE_STACK - PG_TABLE_KERNEL; i++)
+    {
+        SET_PDE(
+            ptd, 
+            kernel_pde_index + i,   
+            PDE(PG_PREM_RW, PT_ADDR(ptd, PG_TABLE_KERNEL + i))
+        )
+    }
+    
+    // 首先，检查内核的大小是否可以fit进我们这几个表（12MiB）
+    if (kernel_pg_counts > (PG_TABLE_STACK - PG_TABLE_KERNEL) * 1024) {
+        // ERROR: require more pages
+        //  here should do something else other than head into blocking
+        while (1);
+    }
+    
+    // 计算内核.text段的物理地址
+    uintptr_t kernel_pm = V2P(&__kernel_start);
+    
+    // 重映射内核至高半区地址（>=0xC0000000）
+    for (uint32_t i = 0; i < kernel_pg_counts; i++)
+    {
+        SET_PTE(
+            ptd, 
+            PG_TABLE_KERNEL, 
+            kernel_pte_index + i, 
+            PTE(PG_PREM_RW, kernel_pm + (i << 12))
+        )
+    }
+
+    // 最后一个entry用于循环映射
+    SET_PDE(
+        ptd,
+        1023,
+        PDE(T_SELF_REF_PERM, ptd)
+    );
+}
+
+uint32_t __save_subset(uint8_t* destination, uint8_t* base, unsigned int size) {
+    unsigned int i = 0;
+    for (; i < size; i++)
+    {
+        *(destination + i) = *(base + i);
+    }
+    return i;
+}
+
+void 
+_save_multiboot_info(multiboot_info_t* info, uint8_t* destination) {
+    uint32_t current = 0;
+    uint8_t* info_b = (uint8_t*) info;
+    for (; current < sizeof(multiboot_info_t); current++)
+    {
+        *(destination + current) = *(info_b + current);
+    }
+
+    ((multiboot_info_t*) destination)->mmap_addr = (uintptr_t)destination + current;
+    current += __save_subset(destination + current, (uint8_t*)info->mmap_addr, info->mmap_length);
+
+    if (present(info->flags, MULTIBOOT_INFO_DRIVE_INFO)) {
+        ((multiboot_info_t*) destination)->drives_addr = (uintptr_t)destination + current;
+        current += __save_subset(destination + current, (uint8_t*)info->drives_addr, info->drives_length);
+    }
+}
+
+void 
+_hhk_init(ptd_t* ptd, uint32_t kpg_size) {
+
+    // 初始化 kpg 全为0
+    //      P.s. 真没想到GRUB会在这里留下一堆垃圾！ 老子的页表全乱套了！
+    uint8_t* kpg = (uint8_t*) ptd;
+    for (uint32_t i = 0; i < kpg_size; i++)
+    {
+        *(kpg + i) = 0;
+    }
+    
+    _init_page(ptd);
+}
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