kernel/boot/bootx64.asm

@@ -364,6 +364,13 @@ proc main _efi_handle, _efi_table
         cld
         rep     stosq
 
+        ; Zero out the paging tables table_btr_p1-p3
+        mov     rdi, table_btr_p1
+        mov     rcx, 512*3
+        xor     rax, rax
+        cld
+        rep stosq
+
         ; P4[P4_OFFSET(VIRT_KERNEL_BASE)] = P3 or flags
         mov     rax, table_p3
         or      rax, 0x3 ; present, r/w
@@ -402,6 +409,61 @@ proc main _efi_handle, _efi_table
         cmp     rcx, [kernel_image_phys_end]
         jb      .fill_p1 
 
+        mov     r10, .map_btr_start
+        and     r10, -4096 ; get earliest page
+
+        ;TODO:very evil, doesn't respect if we somehow have the same upper
+        ; bits of addr as kernel
+        ;we probably need to separate this logic into map_region_lessthan2mb
+
+        ; P4[BTR_P4_OFFSET(.map_btr_start)] = BTR_P3
+        mov     rax, table_btr_p3
+        or      rax, 0x3 ; present, r/w
+        mov     rdi, table_p4
+        mov     r11, r10
+        shr     r11, (39 - 3)
+        and     r11, (0x1ff shl 3)
+        add     rdi, r11
+        stosq
+
+        ; BTR_P3[BTR_P3_OFFSET(.map_btr_start)] = BTR_P2
+        mov     rax, table_btr_p2
+        or      rax, 0x3 ; present, r/w
+        mov     rdi, table_btr_p3
+        mov     r11, r10
+        shr     r11, (30 - 3)
+        and     r11, (0x1ff shl 3)
+        add     rdi, r11
+        stosq
+
+        ; BTR_P2[BTR_P2_OFFSET(.map_btr_start)] = BTR_P1
+        mov     rax, table_btr_p1
+        or      rax, 0x3 ; present, r/w
+        mov     rdi, table_btr_p2
+        mov     r11, r10
+        shr     r11, (21 - 3)
+        and     r11, (0x1ff shl 3)
+        add     rdi, r11
+        stosq
+
+        mov     r11, .map_btr_end
+        and     r11, -4096
+        add     r11, 4096 ; get end page
+.fill_btr_p1:
+        mov     rax, r10
+        shr     rax, 12
+        and     rax, 0x1FF
+        shl     rax, BSF 8 ; *8
+        add     rax, table_btr_p1
+        mov     rdi, r10
+        or      rdi, 0x3
+        mov     [rax], rdi
+
+        add     r10, 4096
+        cmp     r10, r11
+        jb      .fill_btr_p1
+        ; hopefully .map_btr_start-.map_btr_end is mapped now
+
         ; Before performing ExitBootServces need to get fresh memory map
         mov     rbx, [efi_table]
         mov     r10, [rbx + EFI_SYSTEM_TABLE.BootServices]
@@ -427,18 +489,30 @@ proc main _efi_handle, _efi_table
         ; и через эту функу замаппить и ядро и этот кусок rip+N.
         ; А в ядре уже так будут функци маппинга любых регионов 
 
+        ; TODO: is there a way to minimize this?
+        mov     r10, [kernel_image_phys_end]
+        sub     r10, [kernel_image_phys_base]
+        add     r10, VIRT_KERNEL_BASE
+        ;prepared kernel sp reg
+
         mov     rax, table_p4
         mov     cr3, rax
-
+        ; WE CANNOT USE STACK AFTER .map_btr_start(STACK IS NOT MAPPED AFTER mov cr3, rax)
+.map_btr_start:
         ; lea     rax, [rip]
         ; jmp     rax
         ; fstcall efi_print_hex_fixed, table_p4
 
-        mov     rax, [kernel_image_phys_base]
-        mov     rax, [rax + KERNEL64_HEADER.entry_point_offset]
-        add     rax, [kernel_image_phys_base] ; jump to phys kernel for now
-        ; add     rax, VIRT_KERNEL_BASE
+        mov     rax, VIRT_KERNEL_BASE + KERNEL64_HEADER.entry_point_offset
+        mov     rax, [rax]
+        ; add     rax, [kernel_image_phys_base] ; jump to phys kernel for now
+        add     rax, VIRT_KERNEL_BASE
+        mov     rsp, r10
+        ; we have set the kernel's stack
+        ; now jump to it
+        ;TODO:we definitely need to think about the memory map stuff
         jmp     rax
+.map_btr_end:
 
         ; TODO
         ;; QUESTION: How to pass memory map to the kernel?
@@ -563,5 +637,8 @@ table_p2                 rq 512
 table_p3                 rq 512
 table_p4                 rq 512
 
+table_btr_p1             rq 512
+table_btr_p2             rq 512
+table_btr_p3             rq 512
 
 section '.reloc' fixups data discardable