efi/arm: libstub: add a root memreserve config table

Installing UEFI configuration tables can only be done before calling
ExitBootServices(), so if we want to use the new MEMRESRVE config table
from the kernel proper, we need to install a dummy entry from the stub.
Tested-by: NJeremy Linton <jeremy.linton@arm.com>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>

drivers/firmware/efi/libstub/arm-stub.c

@@ -69,6 +69,31 @@ static struct screen_info *setup_graphics(efi_system_table_t *sys_table_arg)
 	return si;
 }
 
+void install_memreserve_table(efi_system_table_t *sys_table_arg)
+{
+	struct linux_efi_memreserve *rsv;
+	efi_guid_t memreserve_table_guid = LINUX_EFI_MEMRESERVE_TABLE_GUID;
+	efi_status_t status;
+
+	status = efi_call_early(allocate_pool, EFI_LOADER_DATA, sizeof(*rsv),
+				(void **)&rsv);
+	if (status != EFI_SUCCESS) {
+		pr_efi_err(sys_table_arg, "Failed to allocate memreserve entry!\n");
+		return;
+	}
+
+	rsv->next = 0;
+	rsv->base = 0;
+	rsv->size = 0;
+
+	status = efi_call_early(install_configuration_table,
+				&memreserve_table_guid,
+				rsv);
+	if (status != EFI_SUCCESS)
+		pr_efi_err(sys_table_arg, "Failed to install memreserve config table!\n");
+}
+
+
 /*
  * This function handles the architcture specific differences between arm and
  * arm64 regarding where the kernel image must be loaded and any memory that
@@ -235,6 +260,8 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
 		}
 	}
 
+	install_memreserve_table(sys_table);
+
 	new_fdt_addr = fdt_addr;
 	status = allocate_new_fdt_and_exit_boot(sys_table, handle,
 				&new_fdt_addr, efi_get_max_fdt_addr(dram_base),