[PATCH v3 17/19] multiboot: Make GRUB_MULTIBOOT(make_mbi) return MBI's size

[Sergii Dmytruk]

GRUB_MULTIBOOT(get_mbi_size) returns an upper bound on MBI's size
instead of the actual size.  It could also be used for measurements
after zeroing unused parts of the buffer, but using an actual size seems
like a better option as the same MBI will always have the same hash
regardless of the amount of extra memory that follows it.

Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
---
 grub-core/loader/i386/multiboot_mbi.c | 4 +++-
 grub-core/loader/multiboot.c          | 3 ++-
 grub-core/loader/multiboot_mbi2.c     | 6 ++++--
 include/grub/multiboot.h              | 2 +-
 include/grub/multiboot2.h             | 3 ++-
 5 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/grub-core/loader/i386/multiboot_mbi.c 
b/grub-core/loader/i386/multiboot_mbi.c
index bdaf67ad0..f058f4645 100644
--- a/grub-core/loader/i386/multiboot_mbi.c
+++ b/grub-core/loader/i386/multiboot_mbi.c
@@ -453,7 +453,7 @@ retrieve_video_parameters (struct multiboot_info *mbi,
 }
 
 grub_err_t
-grub_multiboot_make_mbi (grub_uint32_t *target)
+grub_multiboot_make_mbi (grub_uint32_t *target, grub_uint32_t *size)
 {
   struct multiboot_info *mbi;
   struct multiboot_mod_list *modlist;
@@ -621,6 +621,8 @@ grub_multiboot_make_mbi (grub_uint32_t *target)
     return err;
 #endif
 
+  *size = (char *) ptrorig - (char *) mbi;
+
   return GRUB_ERR_NONE;
 }
 
diff --git a/grub-core/loader/multiboot.c b/grub-core/loader/multiboot.c
index ec29f1b58..98c1d5e99 100644
--- a/grub-core/loader/multiboot.c
+++ b/grub-core/loader/multiboot.c
@@ -177,6 +177,7 @@ static grub_err_t
 grub_multiboot_boot (void)
 {
   grub_err_t err;
+  grub_uint32_t mbi_size;
 
 #ifdef GRUB_USE_MULTIBOOT2
   struct grub_relocator32_state state = MULTIBOOT2_INITIAL_STATE;
@@ -185,7 +186,7 @@ grub_multiboot_boot (void)
 #endif
   state.MULTIBOOT_ENTRY_REGISTER = GRUB_MULTIBOOT (payload_eip);
 
-  err = GRUB_MULTIBOOT (make_mbi) (&state.MULTIBOOT_MBI_REGISTER);
+  err = GRUB_MULTIBOOT (make_mbi) (&state.MULTIBOOT_MBI_REGISTER, &mbi_size);
 
   if (err)
     return err;
diff --git a/grub-core/loader/multiboot_mbi2.c 
b/grub-core/loader/multiboot_mbi2.c
index 00a48413c..1945b3ac6 100644
--- a/grub-core/loader/multiboot_mbi2.c
+++ b/grub-core/loader/multiboot_mbi2.c
@@ -701,7 +701,7 @@ retrieve_video_parameters (grub_properly_aligned_t 
**ptrorig)
 }
 
 grub_err_t
-grub_multiboot2_make_mbi (grub_uint32_t *target)
+grub_multiboot2_make_mbi (grub_uint32_t *target, grub_uint32_t *size)
 {
   grub_properly_aligned_t *ptrorig;
   grub_properly_aligned_t *mbistart;
@@ -1002,7 +1002,9 @@ grub_multiboot2_make_mbi (grub_uint32_t *target)
       / sizeof (grub_properly_aligned_t);
   }
 
-  ((grub_uint32_t *) mbistart)[0] = (char *) ptrorig - (char *) mbistart;
+  *size = (char *) ptrorig - (char *) mbistart;
+
+  ((grub_uint32_t *) mbistart)[0] = *size;
   ((grub_uint32_t *) mbistart)[1] = 0;
 
   return GRUB_ERR_NONE;
diff --git a/include/grub/multiboot.h b/include/grub/multiboot.h
index d8847f753..020c54847 100644
--- a/include/grub/multiboot.h
+++ b/include/grub/multiboot.h
@@ -41,7 +41,7 @@ void grub_multiboot (int argc, char *argv[]);
 void grub_module (int argc, char *argv[]);
 
 void grub_multiboot_set_accepts_video (int val);
-grub_err_t grub_multiboot_make_mbi (grub_uint32_t *target);
+grub_err_t grub_multiboot_make_mbi (grub_uint32_t *target, grub_uint32_t 
*size);
 void grub_multiboot_free_mbi (void);
 grub_err_t grub_multiboot_init_mbi (int argc, char *argv[]);
 grub_err_t grub_multiboot_add_module (grub_addr_t start, grub_size_t size,
diff --git a/include/grub/multiboot2.h b/include/grub/multiboot2.h
index b90aa6989..3417a1447 100644
--- a/include/grub/multiboot2.h
+++ b/include/grub/multiboot2.h
@@ -33,7 +33,8 @@ void grub_multiboot2 (int argc, char *argv[]);
 void grub_module2 (int argc, char *argv[]);
 
 void grub_multiboot2_set_accepts_video (int val);
-grub_err_t grub_multiboot2_make_mbi (grub_uint32_t *target);
+grub_err_t grub_multiboot2_make_mbi (grub_uint32_t *target,
+                                     grub_uint32_t *size);
 void grub_multiboot2_free_mbi (void);
 grub_err_t grub_multiboot2_init_mbi (int argc, char *argv[]);
 grub_err_t grub_multiboot2_add_module (grub_addr_t start, grub_size_t size,
-- 
2.47.1