efi_loader: Add exit support

Some times you may want to exit an EFI payload again, for example
to default boot into a PXE installation and decide that you would
rather want to boot from the local disk instead.

This patch adds exit functionality to the EFI implementation, allowing
EFI payloads to exit.

Signed-off-by: Alexander Graf <agraf@suse.de>

3 files changed, 32 insertions, 5 deletions

diff --git a/cmd/bootefi.c b/cmd/bootefi.c
index d3a23318702..2a62dce702b 100644
--- a/cmd/bootefi.c
+++ b/cmd/bootefi.c
@@ -209,6 +209,12 @@ static unsigned long do_bootefi_exec(void *efi, void *fdt)
 #ifdef DEBUG_EFI
 	printf("%s:%d Jumping to 0x%lx\n", __func__, __LINE__, (long)entry);
 #endif
+
+	if (setjmp(&loaded_image_info.exit_jmp)) {
+		efi_status_t status = loaded_image_info.exit_status;
+		return status == EFI_SUCCESS ? 0 : -EINVAL;
+	}
+
 	return entry(&loaded_image_info, &systab);
 }
 
diff --git a/include/efi_api.h b/include/efi_api.h
index 20035d72727..f572b880798 100644
--- a/include/efi_api.h
+++ b/include/efi_api.h
@@ -17,6 +17,10 @@
 
 #include <efi.h>
 
+#ifdef CONFIG_EFI_LOADER
+#include <asm/setjmp.h>
+#endif
+
 /* Types and defines for EFI CreateEvent */
 enum efi_event_type {
 	EFI_TIMER_STOP = 0,
@@ -239,6 +243,12 @@ struct efi_loaded_image {
 	unsigned int image_code_type;
 	unsigned int image_data_type;
 	unsigned long unload;
+
+	/* Below are efi loader private fields */
+#ifdef CONFIG_EFI_LOADER
+	efi_status_t exit_status;
+	struct jmp_buf_data exit_jmp;
+#endif
 };
 
 #define DEVICE_PATH_GUID \
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index 9daca50a72f..15a1b90d65a 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -458,19 +458,30 @@ static efi_status_t EFIAPI efi_start_image(efi_handle_t image_handle,
 	efi_is_direct_boot = false;
 
 	/* call the image! */
+	if (setjmp(&info->exit_jmp)) {
+		/* We returned from the child image */
+		return EFI_EXIT(info->exit_status);
+	}
+
 	entry(image_handle, &systab);
 
 	/* Should usually never get here */
 	return EFI_EXIT(EFI_SUCCESS);
 }
 
-static efi_status_t EFIAPI efi_exit(void *image_handle, long exit_status,
-				    unsigned long exit_data_size,
-				    uint16_t *exit_data)
+static efi_status_t EFIAPI efi_exit(efi_handle_t image_handle,
+			efi_status_t exit_status, unsigned long exit_data_size,
+			int16_t *exit_data)
 {
+	struct efi_loaded_image *loaded_image_info = (void*)image_handle;
+
 	EFI_ENTRY("%p, %ld, %ld, %p", image_handle, exit_status,
 		  exit_data_size, exit_data);
-	return EFI_EXIT(efi_unsupported(__func__));
+
+	loaded_image_info->exit_status = exit_status;
+	longjmp(&loaded_image_info->exit_jmp);
+
+	panic("EFI application exited");
 }
 
 static struct efi_object *efi_search_obj(void *handle)
@@ -746,7 +757,7 @@ static const struct efi_boot_services efi_boot_services = {
 	.install_configuration_table = efi_install_configuration_table,
 	.load_image = efi_load_image,
 	.start_image = efi_start_image,
-	.exit = (void*)efi_exit,
+	.exit = efi_exit,
 	.unload_image = efi_unload_image,
 	.exit_boot_services = efi_exit_boot_services,
 	.get_next_monotonic_count = efi_get_next_monotonic_count,