Add a new sysctl in order to diffrentiate UEFI architectures

With the new 32-bit UEFI loader, it's convenient to have a sysctl to
figure out how we booted. Can be accessed at machdep.efi_arch

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1098

stand/efi/loader/bootinfo.c

@@ -447,9 +447,15 @@ bi_load(char *args, vm_offset_t *modulep, vm_offset_t *kernendp, bool exit_bs)
 	module = *modulep;
 	file_addmetadata(kfp, MODINFOMD_MODULEP, sizeof(module), &module);
 #endif
-#if defined(EFI) && !defined(__i386__)
+#ifdef EFI
+#ifndef __i386__
 	file_addmetadata(kfp, MODINFOMD_FW_HANDLE, sizeof(ST), &ST);
 #endif
+#if defined(__amd64__) || defined(__i386__)
+	file_addmetadata(kfp, MODINFOMD_EFI_ARCH, sizeof(MACHINE_ARCH),
+	    MACHINE_ARCH);
+#endif
+#endif
 #ifdef LOADER_GELI_SUPPORT
 	geli_export_key_metadata(kfp);
 #endif

sys/amd64/amd64/machdep.c

@@ -1689,6 +1689,27 @@ SYSCTL_PROC(_machdep, OID_AUTO, efi_map,
     efi_map_sysctl_handler, "S,efi_map_header",
     "Raw EFI Memory Map");
 
+static int
+efi_arch_sysctl_handler(SYSCTL_HANDLER_ARGS)
+{
+	char *arch;
+	caddr_t kmdp;
+
+	kmdp = preload_search_by_type("elf kernel");
+	if (kmdp == NULL)
+		kmdp = preload_search_by_type("elf64 kernel");
+
+	arch = (char *)preload_search_info(kmdp,
+	    MODINFO_METADATA | MODINFOMD_EFI_ARCH);
+	if (arch == NULL)
+		return (0);
+
+	return (SYSCTL_OUT_STR(req, arch));
+}
+SYSCTL_PROC(_machdep, OID_AUTO, efi_arch,
+    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
+    efi_arch_sysctl_handler, "A", "EFI Firmware Architecture");
+
 void
 spinlock_enter(void)
 {

sys/x86/include/metadata.h

@@ -34,6 +34,7 @@
 #define	MODINFOMD_EFI_FB	0x1005
 #define	MODINFOMD_MODULEP	0x1006
 #define	MODINFOMD_VBE_FB	0x1007
+#define	MODINFOMD_EFI_ARCH	0x1008
 
 struct efi_map_header {
 	uint64_t	memory_size;