git: 61f14f1da37b - main - arm64: Clean up finding our load address

From: Andrew Turner <andrew_at_FreeBSD.org>
Date: Wed, 15 Nov 2023 18:12:20 UTC
The branch main has been updated by andrew:

URL: https://cgit.FreeBSD.org/src/commit/?id=61f14f1da37b4e6db8f9efe40c6b544c855fb9bd

commit 61f14f1da37b4e6db8f9efe40c6b544c855fb9bd
Author:     Andrew Turner <andrew@FreeBSD.org>
AuthorDate: 2023-11-13 15:39:06 +0000
Commit:     Andrew Turner <andrew@FreeBSD.org>
CommitDate: 2023-11-15 18:05:08 +0000

    arm64: Clean up finding our load address
    
    Use the linker to pre-calculate the offset of a known symbol from
    KERNBASE, and use this to find the physical address KERNBASE should
    map to.
    
    Sponsored by:   Arm Ltd
    Differential Revision:  https://reviews.freebsd.org/D42568
---
 sys/arm64/arm64/locore.S | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

diff --git a/sys/arm64/arm64/locore.S b/sys/arm64/arm64/locore.S
index cea2f690b60f..ffd13610ec02 100644
--- a/sys/arm64/arm64/locore.S
+++ b/sys/arm64/arm64/locore.S
@@ -359,21 +359,13 @@ LEND(drop_to_el1)
  * Get the physical address the kernel was loaded at.
  */
 LENTRY(get_load_phys_addr)
+	/* Load the offset of get_load_phys_addr from KERNBASE */
+	ldr	x28, =(get_load_phys_addr - KERNBASE)
 	/* Load the physical address of virt_map */
-	adrp	x29, virt_map
-	add	x29, x29, :lo12:virt_map
-	/* Load the virtual address of virt_map stored in virt_map */
-	ldr	x28, [x29]
-	/* Find PA - VA as PA' = VA' - VA + PA = VA' + (PA - VA) = VA' + x29 */
-	sub	x29, x29, x28
-	/* Find the load address for the kernel */
-	mov	x28, #(KERNBASE)
-	add	x28, x28, x29
+	adr	x29, get_load_phys_addr
+	/* Find the physical address of KERNBASE, i.e. our load address */
+	sub	x28, x29, x28
 	ret
-
-	.align 3
-virt_map:
-	.quad	virt_map
 LEND(get_load_phys_addr)
 
 /*