Stop sharing kernel boot PDPTs and linear boot PDPTs

ostd/src/arch/x86/boot/bsp_boot.S

@@ -56,7 +56,7 @@ __linux64_boot:
 
     // Set up the page table and load it.
     call page_table_setup_64
-    lea rdx, [rip + boot_pml4]
+    lea rdx, [rip + boot_l4pt]
     mov cr3, rdx
 
     // Prepare far return. The default operation size of
@@ -126,7 +126,7 @@ protected_mode:
     mov cr4, eax
 
     // Set the page table address.
-    lea eax, [boot_pml4]
+    lea eax, [boot_l4pt]
     mov cr3, eax
 
     // Enable long mode.
@@ -163,78 +163,77 @@ PTE_WRITE       = (1 << 1)
 PTE_HUGE        = (1 << 7)
 PTE_GLOBAL      = (1 << 8)
 
-    // PML4: 0x00000000_00000000 ~ 0x00000000_3fffffff
+    // L4PT: 0x00000000_00000000 ~ 0x00000000_3fffffff
     //       0x00000000_40000000 ~ 0x00000000_7fffffff
     //       0x00000000_80000000 ~ 0x00000000_bfffffff
     //       0x00000000_c0000000 ~ 0x00000000_ffffffff
-    lea edi, [boot_pml4]
-    lea eax, [boot_pdpt + (PTE_PRESENT | PTE_WRITE)]
+    lea edi, [boot_l4pt]
+    lea eax, [boot_l3pt_linear_id + (PTE_PRESENT | PTE_WRITE)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // PML4: 0xffff8000_00000000 ~ 0xffff8000_3fffffff
+    // L4PT: 0xffff8000_00000000 ~ 0xffff8000_3fffffff
     //       0xffff8000_40000000 ~ 0xffff8000_7fffffff
     //       0xffff8000_80000000 ~ 0xffff8000_bfffffff
     //       0xffff8000_c0000000 ~ 0xffff8000_ffffffff
-    //       0xffff8008_00000000 ~ 0xffff8008_3fffffff
-    lea edi, [boot_pml4 + 0x100 * 8]
-    lea eax, [boot_pdpt + (PTE_PRESENT | PTE_WRITE)]
+    lea edi, [boot_l4pt + 0x100 * 8]
+    lea eax, [boot_l3pt_linear_id + (PTE_PRESENT | PTE_WRITE)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // PML4: 0xffffffff_80000000 ~ 0xffffffff_bfffffff
+    // L4PT: 0xffffffff_80000000 ~ 0xffffffff_bfffffff
     //       0xffffffff_c0000000 ~ 0xffffffff_ffffffff
-    lea edi, [boot_pml4 + 0x1ff * 8]
-    lea eax, [boot_pdpt + (PTE_PRESENT | PTE_WRITE)]
+    lea edi, [boot_l4pt + 0x1ff * 8]
+    lea eax, [boot_l3pt_kernel + (PTE_PRESENT | PTE_WRITE)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // PDPT: 0x00000000_00000000 ~ 0x00000000_3fffffff
-    lea edi, [boot_pdpt]
-    lea eax, [boot_pd_0g_1g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
+    // L3PT: 0x00000000_00000000 ~ 0x00000000_3fffffff
+    lea edi, [boot_l3pt_linear_id]
+    lea eax, [boot_l2pt_0g_1g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // PDPT: 0x00000000_40000000 ~ 0x00000000_7fffffff
-    lea edi, [boot_pdpt + 0x1 * 8]
-    lea eax, [boot_pd_1g_2g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
+    // L3PT: 0x00000000_40000000 ~ 0x00000000_7fffffff
+    lea edi, [boot_l3pt_linear_id + 0x1 * 8]
+    lea eax, [boot_l2pt_1g_2g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // PDPT: 0x00000000_80000000 ~ 0x00000000_bfffffff
-    lea edi, [boot_pdpt + 0x2 * 8]
-    lea eax, [boot_pd_2g_3g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
+    // L3PT: 0x00000000_80000000 ~ 0x00000000_bfffffff
+    lea edi, [boot_l3pt_linear_id + 0x2 * 8]
+    lea eax, [boot_l2pt_2g_3g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // PDPT: 0x00000000_c0000000 ~ 0x00000000_ffffffff
-    lea edi, [boot_pdpt + 0x3 * 8]
-    lea eax, [boot_pd_3g_4g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
+    // L3PT: 0x00000000_c0000000 ~ 0x00000000_ffffffff
+    lea edi, [boot_l3pt_linear_id + 0x3 * 8]
+    lea eax, [boot_l2pt_3g_4g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // PDPT: 0xffffffff_80000000 ~ 0xffffffff_bfffffff
-    lea edi, [boot_pdpt + 0x1fe * 8]
-    lea eax, [boot_pd_0g_1g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
+    // L3PT: 0xffffffff_80000000 ~ 0xffffffff_bfffffff
+    lea edi, [boot_l3pt_kernel + 0x1fe * 8]
+    lea eax, [boot_l2pt_0g_1g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // PDPT: 0xffffffff_c0000000 ~ 0xffffffff_ffffffff
-    lea edi, [boot_pdpt + 0x1ff * 8]
-    lea eax, [boot_pd_1g_2g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
+    // L3PT: 0xffffffff_c0000000 ~ 0xffffffff_ffffffff
+    lea edi, [boot_l3pt_kernel + 0x1ff * 8]
+    lea eax, [boot_l2pt_1g_2g + (PTE_PRESENT | PTE_WRITE | PTE_GLOBAL)]
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
 
-    // Page Directory: map to low 1 GiB * 4 space
-    lea edi, [boot_pd]
+    // L2PT: map to low 1 GiB * 4 space
+    lea edi, [boot_l2pt]
     mov eax, PTE_PRESENT | PTE_WRITE | PTE_GLOBAL | PTE_HUGE
     mov ecx, 512 * 4 // (of entries in PD) * (number of PD)
-write_pd_entry_\bits:
+write_l2pt_entry_\bits:
     mov dword ptr [edi], eax
     mov dword ptr [edi + 4], 0
     add eax, 0x200000 // +2MiB
     add edi, 8
-    loop write_pd_entry_\bits
+    loop write_l2pt_entry_\bits
 
     ret
 .endm
@@ -263,18 +262,26 @@ gdt_end:
 
 .global boot_page_table_start
 boot_page_table_start:
-boot_pml4:
+boot_l4pt:
     .skip 4096
-boot_pdpt:
+// This L3PT is used for both identity mapping and linear mapping. Four lower
+// entries point to `boot_l2pt`s so that it maps to low 4G physical memory.
+boot_l3pt_linear_id:
     .skip 4096
-boot_pd:
-boot_pd_0g_1g:
+// This L3PT is used for kernel mapping, which is at highest 2G space. Two
+// higher entries point to `boot_l2pt`s so it maps to low 2G physical memory.
+boot_l3pt_kernel:
     .skip 4096
-boot_pd_1g_2g:
+// These L2PTs are used for identity mapping, linear mapping and kernel mapping.
+// They map to low 4G physical memory in 2MB huge pages.
+boot_l2pt:
+boot_l2pt_0g_1g:
     .skip 4096
-boot_pd_2g_3g:
+boot_l2pt_1g_2g:
     .skip 4096
-boot_pd_3g_4g:
+boot_l2pt_2g_3g:
+    .skip 4096
+boot_l2pt_3g_4g:
     .skip 4096
 boot_page_table_end: