aarch64: move kernel stack top to 0x100000

kernel/src/arch/aarch64/boot/boot.S

@@ -2,8 +2,7 @@
 
 .section .text.boot
 
-.global _start
-_start:
+boot:
     # read cpu affinity, start core 0, halt rest
     mrs     x1, mpidr_el1
     and     x1, x1, #3
@@ -16,7 +15,7 @@ halt:
 
 setup:
     # store the desired EL1 stack pointer in x1
-    adr     x1, _start
+    ldr     x1, =_start
 
     # use SP_ELx for Exception level ELx
     msr     SPsel, #1
@@ -99,12 +98,17 @@ zero_bss:
 
 zero_bss_loop:
     # zero out the BSS section, 64-bits at a time
-    cbz     x2, go_kmain
+    cbz     x2, zero_bss_loop_end
     str     xzr, [x1], #8
     sub     x2, x2, #8
     cbnz    x2, zero_bss_loop
 
-go_kmain:
+zero_bss_loop_end:
+    b       _start
+
+.section .text.entry
+.globl _start
+_start:
     # jump to rust_main, which shouldn't return. halt if it does
     bl      rust_main
     b       halt

kernel/src/arch/aarch64/boot/linker.ld

@@ -3,11 +3,14 @@ ENTRY(_start)
 SECTIONS {
   . = 0x80000; /* Raspbery Pi 3 Aarch64 (kernel8.img) load address */
 
-  /* start of the binary */
-  _start = .;
+  .boot : {
+    KEEP(*(.text.boot)) /* from boot.S */
+  }
+
+  . = 0x100000; /* Load the kernel at this address. It's also kernel stack top address */
 
   .text : {
-    KEEP(*(.text.boot)) /* from boot.S */
+    *(.text.entry)
     *(.text .text.* .gnu.linkonce.t*)
   }