efi_loader: correctly apply relocations from the .reloc section

Instead of difference between preferred and actual image base, the
actual base is added to the fields specified in the .reloc section.

Use ImageBase from PE optional header to compute the delta,
exit early if the image is loaded at the preferred address.

Signed-off-by: Ivan Gorinov <ivan.gorinov@intel.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>

lib/efi_loader/efi_image_loader.c

@@ -90,11 +90,16 @@ void efi_print_image_infos(void *pc)
 }
 
 static efi_status_t efi_loader_relocate(const IMAGE_BASE_RELOCATION *rel,
-			unsigned long rel_size, void *efi_reloc)
+			unsigned long rel_size, void *efi_reloc,
+			unsigned long pref_address)
 {
+	unsigned long delta = (unsigned long)efi_reloc - pref_address;
 	const IMAGE_BASE_RELOCATION *end;
 	int i;
 
+	if (delta == 0)
+		return EFI_SUCCESS;
+
 	end = (const IMAGE_BASE_RELOCATION *)((const char *)rel + rel_size);
 	while (rel < end - 1 && rel->SizeOfBlock) {
 		const uint16_t *relocs = (const uint16_t *)(rel + 1);
@@ -103,7 +108,6 @@ static efi_status_t efi_loader_relocate(const IMAGE_BASE_RELOCATION *rel,
 			uint32_t offset = (uint32_t)(*relocs & 0xfff) +
 					  rel->VirtualAddress;
 			int type = *relocs >> EFI_PAGE_SHIFT;
-			unsigned long delta = (unsigned long)efi_reloc;
 			uint64_t *x64 = efi_reloc + offset;
 			uint32_t *x32 = efi_reloc + offset;
 			uint16_t *x16 = efi_reloc + offset;
@@ -191,6 +195,7 @@ void *efi_load_pe(void *efi, struct efi_loaded_image *loaded_image_info)
 	unsigned long rel_size;
 	int rel_idx = IMAGE_DIRECTORY_ENTRY_BASERELOC;
 	void *entry;
+	uint64_t image_base;
 	uint64_t image_size;
 	unsigned long virt_size = 0;
 	int supported = 0;
@@ -234,6 +239,7 @@ void *efi_load_pe(void *efi, struct efi_loaded_image *loaded_image_info)
 	if (nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR64_MAGIC) {
 		IMAGE_NT_HEADERS64 *nt64 = (void *)nt;
 		IMAGE_OPTIONAL_HEADER64 *opt = &nt64->OptionalHeader;
+		image_base = opt->ImageBase;
 		image_size = opt->SizeOfImage;
 		efi_set_code_and_data_type(loaded_image_info, opt->Subsystem);
 		efi_reloc = efi_alloc(virt_size,
@@ -249,6 +255,7 @@ void *efi_load_pe(void *efi, struct efi_loaded_image *loaded_image_info)
 		virt_size = ALIGN(virt_size, opt->SectionAlignment);
 	} else if (nt->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR32_MAGIC) {
 		IMAGE_OPTIONAL_HEADER32 *opt = &nt->OptionalHeader;
+		image_base = opt->ImageBase;
 		image_size = opt->SizeOfImage;
 		efi_set_code_and_data_type(loaded_image_info, opt->Subsystem);
 		efi_reloc = efi_alloc(virt_size,
@@ -279,7 +286,8 @@ void *efi_load_pe(void *efi, struct efi_loaded_image *loaded_image_info)
 	}
 
 	/* Run through relocations */
-	if (efi_loader_relocate(rel, rel_size, efi_reloc) != EFI_SUCCESS) {
+	if (efi_loader_relocate(rel, rel_size, efi_reloc,
+				(unsigned long)image_base) != EFI_SUCCESS) {
 		efi_free_pages((uintptr_t) efi_reloc,
 			       (virt_size + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT);
 		return NULL;