systemd-boot: Try harder not to add ourselves to the list

We don't need to check if we are adding ourselves to the list
if we know that it's the windows or EFI shell loaders.

If we are adding the EFI default loader, additionally try to
see if we can find the systemd-boot magic string and skip
this entry if we do.

1 files changed, 24 insertions, 4 deletions

diff --git a/src/boot/efi/boot.c b/src/boot/efi/boot.c
index e0438281e1..4768366c1e 100644
--- a/src/boot/efi/boot.c
+++ b/src/boot/efi/boot.c
@@ -1458,8 +1458,28 @@ static BOOLEAN config_entry_add_loader_auto(Config *config, EFI_HANDLE *device,
                 return FALSE;
 
         /* do not add an entry for ourselves */
-        if (loaded_image_path && StriCmp(loader, loaded_image_path) == 0)
-                return FALSE;
+        if (loaded_image_path) {
+                UINTN len;
+                CHAR8 *content;
+
+                if (StriCmp(loader, loaded_image_path) == 0)
+                        return FALSE;
+
+                /* look for systemd-boot magic string */
+                err = file_read(root_dir, loader, 0, 100*1024, &content, &len);
+                if (!EFI_ERROR(err)) {
+                        CHAR8 *start = content;
+                        CHAR8 *last = content + len - sizeof(magic) - 1;
+
+                        for (; start <= last; start++)
+                                if (start[0] == magic[0] && CompareMem(start, magic, sizeof(magic) - 1) == 0) {
+                                        FreePool(content);
+                                        return FALSE;
+                                }
+
+                        FreePool(content);
+                }
+        }
 
         /* check existence */
         err = uefi_call_wrapper(root_dir->Open, 5, root_dir, &handle, loader, EFI_FILE_MODE_READ, 0ULL);
@@ -1785,9 +1805,9 @@ EFI_STATUS efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *sys_table) {
         config_sort_entries(&config);
 
         /* if we find some well-known loaders, add them to the end of the list */
-        config_entry_add_loader_auto(&config, loaded_image->DeviceHandle, root_dir, loaded_image_path,
+        config_entry_add_loader_auto(&config, loaded_image->DeviceHandle, root_dir, NULL,
                                      L"auto-windows", 'w', L"Windows Boot Manager", L"\\EFI\\Microsoft\\Boot\\bootmgfw.efi");
-        config_entry_add_loader_auto(&config, loaded_image->DeviceHandle, root_dir, loaded_image_path,
+        config_entry_add_loader_auto(&config, loaded_image->DeviceHandle, root_dir, NULL,
                                      L"auto-efi-shell", 's', L"EFI Shell", L"\\shell" EFI_MACHINE_TYPE_NAME ".efi");
         config_entry_add_loader_auto(&config, loaded_image->DeviceHandle, root_dir, loaded_image_path,
                                      L"auto-efi-default", '\0', L"EFI Default Loader", L"\\EFI\\Boot\\boot" EFI_MACHINE_TYPE_NAME ".efi");