svn commit: r366670 - head/stand/efi/loader/arch/arm64

[Andrew Turner]

Author: andrew
Date: Tue Oct 13 16:51:05 2020
New Revision: 366670
URL: https://svnweb.freebsd.org/changeset/base/366670

Log:
  Use adrp in the arm64 efi loader
  
  On startup the arm64 efi loaders need to know PC-relative addresses.
  Previously we used the adr instruction to find this address, however this
  instruction is limited to +/- 1MiB.
  
  Switch to adrp to find the 4k page the address is within and an add to
  set the bottom 12 bits. This lets us address +/- 4GiB which should be
  large enough for now.
  
  Reported by:	imp
  MFC after:	2 weeks
  Sponsored by:	Innovate UK

Modified:
  head/stand/efi/loader/arch/arm64/start.S

Modified: head/stand/efi/loader/arch/arm64/start.S
==============================================================================
--- head/stand/efi/loader/arch/arm64/start.S	Tue Oct 13 16:19:21 2020	(r366669)
+++ head/stand/efi/loader/arch/arm64/start.S	Tue Oct 13 16:51:05 2020	(r366670)
@@ -142,8 +142,10 @@ _start:
 	/* Save the boot params to the stack */
 	stp	x0, x1, [sp, #-16]!
 
-	adr	x0, __bss_start
-	adr	x1, __bss_end
+	adrp	x0, __bss_start
+	add	x0, x0, :lo12:__bss_start
+	adrp	x1, __bss_end
+	add	x1, x1, :lo12:__bss_end
 
 	b 2f
 
@@ -153,8 +155,10 @@ _start:
 	cmp	x0, x1
 	b.lo	1b
 
-	adr	x0, ImageBase
-	adr	x1, _DYNAMIC
+	adrp	x0, ImageBase
+	add	x0, x0, :lo12:ImageBase
+	adrp	x1, _DYNAMIC
+	add	x1, x1, :lo12:_DYNAMIC
 
 	bl	self_reloc
 
@@ -165,7 +169,8 @@ _start:
 	 * Load the stack to use. The default stack may be too small for
 	 * the lua loader.
 	 */
-	adr	x2, initstack_end
+	adrp	x2, initstack_end
+	add	x2, x2, :lo12:initstack_end
 	mov	sp, x2
 #endif