[PATCH V2] mkimage: zero fill alignment space

[Andrei Borzenkov]

This did not cause real problem but is good for reproducible builds. I hit
it with recent bootinfoscript that displays embedded config; I was puzzled
by random garbage at the end.

Prezero memory buffer used to assemble core.img. This makes individual
memset redundant. Also ensure buffer is filled with zeroes in several other
places.

Also remove redundant zeroing code where we fill in the whole memory block
anyway.

---
 util/grub-mkimagexx.c |  3 ++-
 util/mkimage.c        | 30 +++++++++---------------------
 2 files changed, 11 insertions(+), 22 deletions(-)

diff --git a/util/grub-mkimagexx.c b/util/grub-mkimagexx.c
index 3c76d07..a1ddc62 100644
--- a/util/grub-mkimagexx.c
+++ b/util/grub-mkimagexx.c
@@ -101,7 +101,7 @@ SUFFIX (generate_elf) (const struct 
grub_install_image_target_desc *image_target
   program_size = ALIGN_ADDR (*core_size);
 
   elf_img = xmalloc (program_size + header_size + footer_size);
-  memset (elf_img, 0, program_size + header_size);
+  memset (elf_img, 0, program_size + header_size + footer_size);
   memcpy (elf_img  + header_size, *core_img, *core_size);
   ehdr = (void *) elf_img;
   phdr = (void *) (elf_img + sizeof (*ehdr));
@@ -1587,6 +1587,7 @@ SUFFIX (load_image) (const char *kernel_path, size_t 
*exec_size,
     }
 
   out_img = xmalloc (*kernel_sz + total_module_size);
+  memset (out_img, 0, *kernel_sz + total_module_size);
 
   if (image_target->id == IMAGE_EFI)
     {
diff --git a/util/mkimage.c b/util/mkimage.c
index 35df998..dc40461 100644
--- a/util/mkimage.c
+++ b/util/mkimage.c
@@ -992,7 +992,7 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
 {
   char *kernel_img, *core_img;
   size_t kernel_size, total_module_size, core_size, exec_size;
-  size_t memdisk_size = 0, config_size = 0, config_size_pure = 0;
+  size_t memdisk_size = 0, config_size = 0;
   size_t prefix_size = 0;
   char *kernel_path;
   size_t offset;
@@ -1043,8 +1043,7 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
 
   if (config_path)
     {
-      config_size_pure = grub_util_get_image_size (config_path) + 1;
-      config_size = ALIGN_ADDR (config_size_pure);
+      config_size = ALIGN_ADDR (grub_util_get_image_size (config_path) + 1);
       grub_util_info ("the size of config file is 0x%" GRUB_HOST_PRIxLONG_LONG,
                      (unsigned long long) config_size);
       total_module_size += config_size + sizeof (struct grub_module_header);
@@ -1080,7 +1079,10 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
       = grub_host_to_target32 (total_module_size);
 
   if (image_target->flags & PLATFORM_FLAGS_MODULES_BEFORE_KERNEL)
-    memmove (kernel_img + total_module_size, kernel_img, kernel_size);
+    {
+      memmove (kernel_img + total_module_size, kernel_img, kernel_size);
+      memset (kernel_img, 0, total_module_size);
+    }
 
   if (image_target->voidp_sizeof == 8)
     {
@@ -1090,7 +1092,6 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
        modinfo = (struct grub_module_info64 *) kernel_img;
       else
        modinfo = (struct grub_module_info64 *) (kernel_img + kernel_size);
-      memset (modinfo, 0, sizeof (struct grub_module_info64));
       modinfo->magic = grub_host_to_target32 (GRUB_MODULE_MAGIC);
       modinfo->offset = grub_host_to_target_addr (sizeof (struct 
grub_module_info64));
       modinfo->size = grub_host_to_target_addr (total_module_size);
@@ -1107,7 +1108,6 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
        modinfo = (struct grub_module_info32 *) kernel_img;
       else
        modinfo = (struct grub_module_info32 *) (kernel_img + kernel_size);
-      memset (modinfo, 0, sizeof (struct grub_module_info32));
       modinfo->magic = grub_host_to_target32 (GRUB_MODULE_MAGIC);
       modinfo->offset = grub_host_to_target_addr (sizeof (struct 
grub_module_info32));
       modinfo->size = grub_host_to_target_addr (total_module_size);
@@ -1120,17 +1120,14 @@ grub_install_generate_image (const char *dir, const 
char *prefix,
   for (p = path_list; p; p = p->next)
     {
       struct grub_module_header *header;
-      size_t mod_size, orig_size;
+      size_t mod_size;
 
-      orig_size = grub_util_get_image_size (p->name);
-      mod_size = ALIGN_ADDR (orig_size);
+      mod_size = ALIGN_ADDR (grub_util_get_image_size (p->name));
 
       header = (struct grub_module_header *) (kernel_img + offset);
-      memset (header, 0, sizeof (struct grub_module_header));
       header->type = grub_host_to_target32 (OBJ_TYPE_ELF);
       header->size = grub_host_to_target32 (mod_size + sizeof (*header));
       offset += sizeof (*header);
-      memset (kernel_img + offset + orig_size, 0, mod_size - orig_size);
 
       grub_util_load_image (p->name, kernel_img + offset);
       offset += mod_size;
@@ -1146,7 +1143,6 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
        curs = grub_util_get_image_size (pubkey_paths[i]);
 
        header = (struct grub_module_header *) (kernel_img + offset);
-       memset (header, 0, sizeof (struct grub_module_header));
        header->type = grub_host_to_target32 (OBJ_TYPE_PUBKEY);
        header->size = grub_host_to_target32 (curs + sizeof (*header));
        offset += sizeof (*header);
@@ -1161,7 +1157,6 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
       struct grub_module_header *header;
 
       header = (struct grub_module_header *) (kernel_img + offset);
-      memset (header, 0, sizeof (struct grub_module_header));
       header->type = grub_host_to_target32 (OBJ_TYPE_MEMDISK);
       header->size = grub_host_to_target32 (memdisk_size + sizeof (*header));
       offset += sizeof (*header);
@@ -1175,13 +1170,11 @@ grub_install_generate_image (const char *dir, const 
char *prefix,
       struct grub_module_header *header;
 
       header = (struct grub_module_header *) (kernel_img + offset);
-      memset (header, 0, sizeof (struct grub_module_header));
       header->type = grub_host_to_target32 (OBJ_TYPE_CONFIG);
       header->size = grub_host_to_target32 (config_size + sizeof (*header));
       offset += sizeof (*header);
 
       grub_util_load_image (config_path, kernel_img + offset);
-      *(kernel_img + offset + config_size_pure - 1) = 0;
       offset += config_size;
     }
 
@@ -1190,12 +1183,10 @@ grub_install_generate_image (const char *dir, const 
char *prefix,
       struct grub_module_header *header;
 
       header = (struct grub_module_header *) (kernel_img + offset);
-      memset (header, 0, sizeof (struct grub_module_header));
       header->type = grub_host_to_target32 (OBJ_TYPE_PREFIX);
       header->size = grub_host_to_target32 (prefix_size + sizeof (*header));
       offset += sizeof (*header);
 
-      grub_memset (kernel_img + offset, 0, prefix_size);
       grub_strcpy (kernel_img + offset, prefix);
       offset += prefix_size;
     }
@@ -1269,15 +1260,11 @@ grub_install_generate_image (const char *dir, const 
char *prefix,
       full_size = core_size + decompress_size;
 
       full_img = xmalloc (full_size);
-      memset (full_img, 0, full_size); 
 
       memcpy (full_img, decompress_img, decompress_size);
 
       memcpy (full_img + decompress_size, core_img, core_size);
 
-      memset (full_img + decompress_size + core_size, 0,
-             full_size - (decompress_size + core_size));
-
       free (core_img);
       core_img = full_img;
       core_size = full_size;
@@ -1428,6 +1415,7 @@ grub_install_generate_image (const char *dir, const char 
*prefix,
        pe_img = xmalloc (reloc_addr + reloc_size);
        memset (pe_img, 0, header_size);
        memcpy ((char *) pe_img + header_size, core_img, core_size);
+       memset ((char *) pe_img + header_size + core_size, 0, reloc_addr - 
(header_size + core_size));
        memcpy ((char *) pe_img + reloc_addr, rel_section, reloc_size);
        header = pe_img;
 
-- 
tg: (2066766..) u/mkimage-zero-pad (depends on: master)