arm64: support initrd outside kernel linear map

The use of mem= could leave part or all of the initrd outside of the
kernel linear map.  This will lead to an error when unpacking the initrd
and a probable failure to boot.  This patch catches that situation and
relocates the initrd to be fully within the linear map.
Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm64/kernel/setup.c

@@ -339,6 +339,67 @@ static void __init request_standard_resources(void)
 	}
 }
 
+#ifdef CONFIG_BLK_DEV_INITRD
+/*
+ * Relocate initrd if it is not completely within the linear mapping.
+ * This would be the case if mem= cuts out all or part of it.
+ */
+static void __init relocate_initrd(void)
+{
+	phys_addr_t orig_start = __virt_to_phys(initrd_start);
+	phys_addr_t orig_end = __virt_to_phys(initrd_end);
+	phys_addr_t ram_end = memblock_end_of_DRAM();
+	phys_addr_t new_start;
+	unsigned long size, to_free = 0;
+	void *dest;
+
+	if (orig_end <= ram_end)
+		return;
+
+	/*
+	 * Any of the original initrd which overlaps the linear map should
+	 * be freed after relocating.
+	 */
+	if (orig_start < ram_end)
+		to_free = ram_end - orig_start;
+
+	size = orig_end - orig_start;
+
+	/* initrd needs to be relocated completely inside linear mapping */
+	new_start = memblock_find_in_range(0, PFN_PHYS(max_pfn),
+					   size, PAGE_SIZE);
+	if (!new_start)
+		panic("Cannot relocate initrd of size %ld\n", size);
+	memblock_reserve(new_start, size);
+
+	initrd_start = __phys_to_virt(new_start);
+	initrd_end   = initrd_start + size;
+
+	pr_info("Moving initrd from [%llx-%llx] to [%llx-%llx]\n",
+		orig_start, orig_start + size - 1,
+		new_start, new_start + size - 1);
+
+	dest = (void *)initrd_start;
+
+	if (to_free) {
+		memcpy(dest, (void *)__phys_to_virt(orig_start), to_free);
+		dest += to_free;
+	}
+
+	copy_from_early_mem(dest, orig_start + to_free, size - to_free);
+
+	if (to_free) {
+		pr_info("Freeing original RAMDISK from [%llx-%llx]\n",
+			orig_start, orig_start + to_free - 1);
+		memblock_free(orig_start, to_free);
+	}
+}
+#else
+static inline void __init relocate_initrd(void)
+{
+}
+#endif
+
 u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };
 
 void __init setup_arch(char **cmdline_p)
@@ -372,6 +433,7 @@ void __init setup_arch(char **cmdline_p)
 	acpi_boot_table_init();
 
 	paging_init();
+	relocate_initrd();
 	request_standard_resources();
 
 	early_ioremap_reset();