1 files changed, 56 insertions, 16 deletions

diff --git a/kernel/paging.cpp b/kernel/paging.cpp
index 8c27abc..17b61f4 100644
--- a/kernel/paging.cpp
+++ b/kernel/paging.cpp
@@ -10,9 +10,13 @@ extern "C" {
 namespace mercury::kernel::paging {
 
   static constexpr uint64_t kernel_vram_start = 0xffffffffc0000000;
-  static constexpr uint64_t kernel_vram_pages = 261888;
-  static constexpr uint64_t kernel_stack_bottom = 0xfffffffffff01000;
-  static constexpr uint64_t kernel_stack_top = 0xfffffffffffff000;
+  static constexpr uint64_t kernel_vram_end = 0xffffffffffe00000;
+  static constexpr uint64_t kernel_vram_pages =
+    (kernel_vram_end - kernel_vram_start) / 4096;
+  static constexpr uint64_t syscall_stack_bottom = 0xfffffffffff01000;
+  static constexpr uint64_t syscall_stack_top = 0xfffffffffffff000;
+  static constexpr uint64_t interrupt_stack_bottom = 0xffffffffffe01000;
+  static constexpr uint64_t interrupt_stack_top = 0xffffffffffeff000;
 
   static constexpr uint64_t pram_pages = 1 << 23;
   static uint64_t pram_usage_bitmap[pram_pages / 64];
@@ -32,25 +36,29 @@ namespace mercury::kernel::paging {
   [[gnu::aligned(4096)]] uint64_t kernel_p2[512];
   [[gnu::aligned(4096)]] uint64_t kernel_p1s[512 * 512];
 
-  static uint64_t encode_pte(
-      uint64_t addr, bool user, bool write, bool execute) {
+  uint64_t kernel_p4e;
+
+  uint64_t encode_pte(
+    uint64_t addr, bool user, bool write, bool execute, bool ps
+  ) {
     return (addr & 0x0000ffffffffffff) | (execute ? 0 : (1ULL << 63))
-         | (user << 2) | (write << 1) | 1;
+         | (ps << 7) | (user << 2) | (write << 1) | 1;
   }
 
   void init_kernel_page_tables(uint64_t kernel_offset) {
     __kernel_p4_paddr = (uint64_t)kernel_p4 - kernel_offset;
     for (int i = 0; i < 511; ++i)
       kernel_p4[i] = 0;
-    kernel_p4[511] = encode_pte(
-      (uint64_t)kernel_p3 - kernel_offset, false, true, true);
+    kernel_p4e = encode_pte(
+      (uint64_t)kernel_p3 - kernel_offset, false, true, true, false);
+    kernel_p4[511] = kernel_p4e;
     for (int i = 0; i < 511; ++i)
       kernel_p3[i] = 0;
     kernel_p3[511] = encode_pte(
-      (uint64_t)kernel_p2 - kernel_offset, false, true, true);
+      (uint64_t)kernel_p2 - kernel_offset, false, true, true, false);
     for (int i = 0; i < 512; ++i)
       kernel_p2[i] = encode_pte(
-        (uint64_t)kernel_p1s + 4096 * i - kernel_offset, false, true, true);
+        (uint64_t)kernel_p1s + 4096 * i - kernel_offset, false, true, true, false);
     for (int i = 0; i < 512 * 512; ++i)
       kernel_p1s[i] = 0;
   }
@@ -58,14 +66,22 @@ namespace mercury::kernel::paging {
   void map_kernel_page(
       uint64_t paddr, uint64_t vaddr, bool write, bool execute) {
     uint64_t i = (vaddr - kernel_vram_start) / 4096;
-    kernel_p1s[i] = encode_pte(paddr, false, write, execute);
+    kernel_p1s[i] = encode_pte(paddr, false, write, execute, false);
+  }
+
+  void unmap_kernel_page(uint64_t vaddr) {
+    uint64_t i = (vaddr - kernel_vram_start) / 4096;
+    kernel_p1s[i] = 0;
+    asm volatile (
+      "mov %%cr3, %%rax\nmov %%rax, %%cr3" ::: "%rax"
+    );
   }
 
   static uint64_t take_pram_page() {
     for (uint64_t i = 0; i < pram_pages / 64; ++i)
-      if (pram_usage_bitmap[i] != 0xffffffffffffffff)
+      if (~pram_usage_bitmap[i] != 0)
         for (int j = 0; j < 64; ++j)
-          if (!(pram_usage_bitmap[i] & (1ULL << j))) {
+          if (~pram_usage_bitmap[i] & (1ULL << j)) {
             pram_usage_bitmap[i] |= (1ULL << j);
             return 4096 * (i * 64 + j);
           }
@@ -73,9 +89,27 @@ namespace mercury::kernel::paging {
     return 0;
   }
 
-  void map_kernel_stack() {
-    for (uint64_t vaddr = kernel_stack_bottom;
-         vaddr < kernel_stack_top; vaddr += 4096)
+  uint64_t take_2mib_pram_page() {
+    for (uint64_t i = 0; i < pram_pages / 512; ++i) {
+      for (int j = 0; j < 8; ++j)
+        if (pram_usage_bitmap[i * 8 + j] != 0)
+          goto next_i;
+      for (int j = 0; j < 8; ++j)
+        pram_usage_bitmap[i * 8 + j] = ~0ULL;
+      return 0x200000 * i;
+    next_i:
+      ;
+    }
+    //TODO: handle error
+    return 0;
+  }
+
+  void map_kernel_stacks() {
+    for (uint64_t vaddr = syscall_stack_bottom;
+         vaddr < syscall_stack_top; vaddr += 4096)
+      map_kernel_page(take_pram_page(), vaddr, true, false);
+    for (uint64_t vaddr = interrupt_stack_bottom;
+         vaddr < interrupt_stack_top; vaddr += 4096)
       map_kernel_page(take_pram_page(), vaddr, true, false);
   }
 
@@ -103,6 +137,12 @@ namespace mercury::kernel::paging {
     return (void *)vaddr;
   }
 
+  void map_new_kernel_page(uint64_t &vaddr_out, uint64_t &paddr_out) {
+    vaddr_out = find_unmapped_vram_region(1);
+    paddr_out = take_pram_page();
+    map_kernel_page(paddr_out, vaddr_out, true, false);
+  }
+
   uint64_t get_used_vram_page_count() {
     uint64_t count = 0;
     for (uint64_t i = 0; i < kernel_vram_pages; ++i)