efi: Support showing tables

Add a command (for the app and payload) to display the tables provided
by EFI. Note that for the payload the tables should always be present, so
an error message is unnecessary and would bloat the code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/efi.c b/cmd/efi.c
index c0384e0..6cd5361 100644
--- a/cmd/efi.c
+++ b/cmd/efi.c
@@ -7,10 +7,12 @@
 #include <common.h>
 #include <command.h>
 #include <efi.h>
+#include <efi_api.h>
 #include <errno.h>
 #include <log.h>
 #include <malloc.h>
 #include <sort.h>
+#include <uuid.h>
 #include <asm/global_data.h>
 
 DECLARE_GLOBAL_DATA_PTR;
@@ -273,8 +275,34 @@
 	return ret ? CMD_RET_FAILURE : 0;
 }
 
+static int do_efi_tables(struct cmd_tbl *cmdtp, int flag, int argc,
+			 char *const argv[])
+{
+	struct efi_system_table *systab;
+
+	if (IS_ENABLED(CONFIG_EFI_APP)) {
+		systab = efi_get_sys_table();
+		if (!systab) {
+			printf("Cannot read system table\n");
+			return CMD_RET_FAILURE;
+		}
+	} else {
+		int size;
+		int ret;
+
+		ret = efi_info_get(EFIET_SYS_TABLE, (void **)&systab, &size);
+		if (ret)  /* this should not happen */
+			return CMD_RET_FAILURE;
+	}
+
+	efi_show_tables(systab);
+
+	return 0;
+}
+
 static struct cmd_tbl efi_commands[] = {
 	U_BOOT_CMD_MKENT(mem, 1, 1, do_efi_mem, "", ""),
+	U_BOOT_CMD_MKENT(tables, 1, 1, do_efi_tables, "", ""),
 };
 
 static int do_efi(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
@@ -298,5 +326,6 @@
 U_BOOT_CMD(
 	efi,     3,      1,      do_efi,
 	"EFI access",
-	"mem [all]        Dump memory information [include boot services]"
+	"mem [all]        Dump memory information [include boot services]\n"
+	"tables               Dump tables"
 );