Revert rewrite because it does not zero bss correctly

This reverts commit 3d78371.

Author: phil-opp

Cargo.lock

@@ -19,5 +19,4 @@ panic = "abort"
 
 [profile.release]
 panic = "abort"
-lto = false
-debug = true
+lto = true

Cargo.toml

@@ -7,24 +7,17 @@ SECTIONS {
     . += 512;
     /* page tables */
     . = ALIGN(0x1000);
-    __page_table_start = .;
     _p4 = .;
     . += 0x1000;
     _p3 = .;
     . += 0x1000;
     _p2 = .;
     . += 0x1000;
-    _p1 = .;
-    . += 0x1000;
-    __page_table_end = .;
-    __bootloader_start = .;
     _memory_map = .;
     . += 0x1000;
 
-    _stack_start = .;
+    /* bootloader */
     . = 0x7c00;
-    _stack_end = .;
-
     .bootloader :
     {
         /* first stage */
@@ -46,6 +39,5 @@ SECTIONS {
     . += 512; /* kernel info block */
     _kernel_info_block_end = .;
 
-    __bootloader_end = .;
     _kernel_start_addr = .;
 }

linker.ld

@@ -2,14 +2,19 @@
 .code64
 
 # Expected arguments:
-# - boot info ptr in `rdi`
+# - p4 address in `rdi`
 # - entry point address in `rsi`
 # - stack pointer in `rdx`
+# - boot info ptr in `rcx`
 context_switch:
+    # load new P4 table
+    mov cr3, rdi
 
     # load stack pointer
     mov rsp, rdx
 
+    mov rdi, rcx
+
     # jump to entry point
     jmp rsi
 context_switch_spin: