[Xen-devel] [GRUB2 PATCH v6 3/4 - FOR REVIEW ONLY] multiboot2: Do not pass memory maps to image if EFI boot services are enabled

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

If image requested EFI boot services then skip multiboot2 memory maps.
Main reason for not providing maps is because they will likely be
invalid. We do a few allocations after filling them, e.g. for relocator
needs. Usually we do not care as we would have finished boot services.
If we keep boot services then it is easier/safer to not provide maps.
However, if image needs memory maps and they are not provided by bootloader
then it should get itself just before ExitBootServices() call.

Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
v5 - suggestions/fixes:
   - improve commit message
     (suggested by Konrad Rzeszutek Wilk).

v3 - suggestions/fixes:
   - improve commit message
     (suggested by Konrad Rzeszutek Wilk and Vladimir 'phcoder' Serbinenko).
---
 grub-core/loader/multiboot_mbi2.c |   17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/grub-core/loader/multiboot_mbi2.c 
b/grub-core/loader/multiboot_mbi2.c
index 6c04402..ad1553b 100644
--- a/grub-core/loader/multiboot_mbi2.c
+++ b/grub-core/loader/multiboot_mbi2.c
@@ -390,7 +390,7 @@ static grub_size_t
 grub_multiboot_get_mbi_size (void)
 {
 #ifdef GRUB_MACHINE_EFI
-  if (!efi_mmap_size)
+  if (!keep_bs && !efi_mmap_size)
     find_efi_mmap_size ();    
 #endif
   return 2 * sizeof (grub_uint32_t) + sizeof (struct multiboot_tag)
@@ -755,6 +755,7 @@ grub_multiboot_make_mbi (grub_uint32_t *target)
       }
   }
 
+  if (!keep_bs)
     {
       struct multiboot_tag_mmap *tag = (struct multiboot_tag_mmap *) ptrorig;
       grub_fill_multiboot_mmap (tag);
@@ -776,6 +777,7 @@ grub_multiboot_make_mbi (grub_uint32_t *target)
       / sizeof (grub_properly_aligned_t);
   }
 
+  if (!keep_bs)
     {
       struct multiboot_tag_basic_meminfo *tag
        = (struct multiboot_tag_basic_meminfo *) ptrorig;
@@ -886,21 +888,17 @@ grub_multiboot_make_mbi (grub_uint32_t *target)
     grub_efi_uintn_t efi_desc_size;
     grub_efi_uint32_t efi_desc_version;
 
+    if (!keep_bs)
+      {
        tag->type = MULTIBOOT_TAG_TYPE_EFI_MMAP;
        tag->size = sizeof (*tag) + efi_mmap_size;
 
-    if (!keep_bs)
        err = grub_efi_finish_boot_services (&efi_mmap_size, tag->efi_mmap, 
NULL,
                                             &efi_desc_size, &efi_desc_version);
-    else
-      {
-       if (grub_efi_get_memory_map (&efi_mmap_size, (void *) tag->efi_mmap,
-                                    NULL,
-                                    &efi_desc_size, &efi_desc_version) <= 0)
-         err = grub_error (GRUB_ERR_IO, "couldn't retrieve memory map");
-      }
+
        if (err)
          return err;
+
        tag->descr_size = efi_desc_size;
        tag->descr_vers = efi_desc_version;
        tag->size = sizeof (*tag) + efi_mmap_size;
@@ -908,6 +906,7 @@ grub_multiboot_make_mbi (grub_uint32_t *target)
        ptrorig += ALIGN_UP (tag->size, MULTIBOOT_TAG_ALIGN)
          / sizeof (grub_properly_aligned_t);
       }
+  }
 
   if (keep_bs)
     {
-- 
1.7.10.4


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