[PATCH] efi_loader: replace a u16_strdup with alloc + memcpy

[Ilias Apalodimas]

Heinrich reports that on RISC-V unaligned access is emulated by OpenSBI
which is very slow.  Performance wise it's better if we skip the calls
to u16_strdup() -- which in turn calls u16_strsize() and just allocate/copy the
memory directly.  The access to dp.length may still be unaligned, but that's
way less than what u16_strsize() would do

Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---
 lib/efi_loader/efi_file.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/lib/efi_loader/efi_file.c b/lib/efi_loader/efi_file.c
index 750d380ad967..ff731db6cb8c 100644
--- a/lib/efi_loader/efi_file.c
+++ b/lib/efi_loader/efi_file.c
@@ -1128,6 +1128,7 @@ struct efi_file_handle *efi_file_from_path(struct efi_device_path *fp)
 			container_of(fp, struct efi_device_path_file_path, dp);
 		struct efi_file_handle *f2;
 		u16 *filename;
+		size_t filename_sz;
 
 		if (!EFI_DP_TYPE(fp, MEDIA_DEVICE, FILE_PATH)) {
 			printf("bad file path!\n");
@@ -1140,9 +1141,14 @@ struct efi_file_handle *efi_file_from_path(struct efi_device_path *fp)
 		 * protocol member functions to be aligned.  So memcpy it
 		 * unconditionally
 		 */
-		filename = u16_strdup(fdp->str);
+		if (fdp->dp.length <= offsetof(struct efi_device_path_file_path, str))
+			return NULL;
+		filename_sz = fdp->dp.length -
+			offsetof(struct efi_device_path_file_path, str);
+		filename = calloc(1, filename_sz);
 		if (!filename)
 			return NULL;
+		memcpy(filename, fdp->str, filename_sz);
 		EFI_CALL(ret = f->open(f, &f2, filename,
 				       EFI_FILE_MODE_READ, 0));
 		free(filename);
-- 
2.38.1