arm64: acpi: Honour firmware_signature field of FACS, if it exists

If the firmware_signature changes then OSPM should not attempt to resume
from hibernate, but should instead perform a clean reboot. Set the global
swsusp_hardware_signature to allow the generic code to include the value
in the swsusp header on disk, and perform the appropriate check on resume.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20240412073530.2222496-3-dwmw2@infradead.orgSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/kernel/acpi.c

@@ -26,6 +26,7 @@
 #include <linux/libfdt.h>
 #include <linux/smp.h>
 #include <linux/serial_core.h>
+#include <linux/suspend.h>
 #include <linux/pgtable.h>
 
 #include <acpi/ghes.h>
@@ -227,6 +228,15 @@ void __init acpi_boot_table_init(void)
 		if (earlycon_acpi_spcr_enable)
 			early_init_dt_scan_chosen_stdout();
 	} else {
+#ifdef CONFIG_HIBERNATION
+		struct acpi_table_header *facs = NULL;
+		acpi_get_table(ACPI_SIG_FACS, 1, &facs);
+		if (facs) {
+			swsusp_hardware_signature =
+				((struct acpi_table_facs *)facs)->hardware_signature;
+			acpi_put_table(facs);
+		}
+#endif
 		acpi_parse_spcr(earlycon_acpi_spcr_enable, true);
 		if (IS_ENABLED(CONFIG_ACPI_BGRT))
 			acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);