arm64: kasan: abstract _text and _end to KERNEL_START/END

Arm64 provides defined macro for KERNEL_START and KERNEL_END,
thus replace them by the abstration instead of using _text and _end.
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210324040522.15548-3-lecopzer.chen@mediatek.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/kasan_init.c

@@ -218,8 +218,8 @@ static void __init kasan_init_shadow(void)
 	phys_addr_t pa_start, pa_end;
 	u64 i;
 
-	kimg_shadow_start = (u64)kasan_mem_to_shadow(_text) & PAGE_MASK;
-	kimg_shadow_end = PAGE_ALIGN((u64)kasan_mem_to_shadow(_end));
+	kimg_shadow_start = (u64)kasan_mem_to_shadow(KERNEL_START) & PAGE_MASK;
+	kimg_shadow_end = PAGE_ALIGN((u64)kasan_mem_to_shadow(KERNEL_END));
 
 	mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
 	mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
@@ -240,7 +240,7 @@ static void __init kasan_init_shadow(void)
 	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 
 	kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
-			   early_pfn_to_nid(virt_to_pfn(lm_alias(_text))));
+			   early_pfn_to_nid(virt_to_pfn(lm_alias(KERNEL_START))));
 
 	kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
 				   (void *)mod_shadow_start);