arm64: head: use relative references to the RELA and RELR tables

Formerly, we had to access the RELA and RELR tables via the kernel
mapping that was being relocated, and so deriving the start and end
addresses using ADRP/ADD references was not possible, as the relocation
code runs from the ID map.

Now that we map the entire kernel image via the ID map, we can simplify
this, and just load the entries via the ID map as well.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220624150651.1358849-14-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/head.S

@@ -757,13 +757,10 @@ SYM_FUNC_START_LOCAL(__relocate_kernel)
 	 * Iterate over each entry in the relocation table, and apply the
 	 * relocations in place.
 	 */
-	ldr	w9, =__rela_offset		// offset to reloc table
-	ldr	w10, =__rela_size		// size of reloc table
-
+	adr_l	x9, __rela_start
+	adr_l	x10, __rela_end
 	mov_q	x11, KIMAGE_VADDR		// default virtual offset
 	add	x11, x11, x23			// actual virtual offset
-	add	x9, x9, x11			// __va(.rela)
-	add	x10, x9, x10			// __va(.rela) + sizeof(.rela)
 
 0:	cmp	x9, x10
 	b.hs	1f
@@ -813,10 +810,8 @@ SYM_FUNC_START_LOCAL(__relocate_kernel)
 	 * __relocate_kernel is called twice with non-zero displacements (i.e.
 	 * if there is both a physical misalignment and a KASLR displacement).
 	 */
-	ldr	w9, =__relr_offset		// offset to reloc table
-	ldr	w10, =__relr_size		// size of reloc table
-	add	x9, x9, x11			// __va(.relr)
-	add	x10, x9, x10			// __va(.relr) + sizeof(.relr)
+	adr_l	x9, __relr_start
+	adr_l	x10, __relr_end
 
 	sub	x15, x23, x24			// delta from previous offset
 	cbz	x15, 7f				// nothing to do if unchanged

arch/arm64/kernel/vmlinux.lds.S

@@ -256,21 +256,17 @@ SECTIONS
 	HYPERVISOR_RELOC_SECTION
 
 	.rela.dyn : ALIGN(8) {
+		__rela_start = .;
 		*(.rela .rela*)
+		__rela_end = .;
 	}
 
-	__rela_offset	= ABSOLUTE(ADDR(.rela.dyn) - KIMAGE_VADDR);
-	__rela_size	= SIZEOF(.rela.dyn);
-
-#ifdef CONFIG_RELR
 	.relr.dyn : ALIGN(8) {
+		__relr_start = .;
 		*(.relr.dyn)
+		__relr_end = .;
 	}
 
-	__relr_offset	= ABSOLUTE(ADDR(.relr.dyn) - KIMAGE_VADDR);
-	__relr_size	= SIZEOF(.relr.dyn);
-#endif
-
 	. = ALIGN(SEGMENT_ALIGN);
 	__initdata_end = .;
 	__init_end = .;