[lib][uefi] Make exit_boot_service weak link

This allows different platforms to provide their own implementation
of exit_boot_service

lib/uefi/boot_service_provider.cpp

@@ -28,6 +28,7 @@
 #include "protocols/dt_fixup_protocol.h"
 #include "protocols/gbl_efi_os_configuration_protocol.h"
 #include "protocols/loaded_image_protocol.h"
+#include <lk/compiler.h>
 
 #include "switch_stack.h"
 #include "types.h"
@@ -36,6 +37,11 @@
 #include <string.h>
 #include <sys/types.h>
 
+__WEAK EfiStatus exit_boot_services(EfiHandle image_handle, size_t map_key) {
+  printf("%s is called\n", __FUNCTION__);
+  return SUCCESS;
+}
+
 namespace {
 
 EfiStatus unload(EfiHandle handle) { return SUCCESS; }
@@ -164,11 +170,6 @@ EfiStatus install_configuration_table(const EfiGuid *guid, void *table) {
   return UNSUPPORTED;
 }
 
-EfiStatus exit_boot_services(EfiHandle image_handle, size_t map_key) {
-  printf("%s is called\n", __FUNCTION__);
-  return SUCCESS;
-}
-
 void copy_mem(void *dest, const void *src, size_t len) {
   memcpy(dest, src, len);
 }

lib/uefi/boot_service_provider.h

@@ -121,4 +121,9 @@ struct EFI_LOADED_IMAGE_PROTOCOL {
 
 static constexpr size_t EFI_LOADED_IMAGE_PROTOCOL_REVISION = 0x1000;
 
+// This function would be called from GBL before jumping into android kernel
+// LK provides a default no-op implementation that is weakly linked,
+// different platforms can override with their own implementation.
+EfiStatus exit_boot_services(EfiHandle image_handle, size_t map_key);
+
 #endif