i386/skinit: don't allocate TPM event log low

Do allocation in the same way as it's done for TXT (preferring high
addresses), otherwise Xen loads Dom0 kernel over the TPM even log and
Linux ends up panicking when it detects conflict with e820 map in
Xen-specific code (why wouldn't Xen check it?  who knows).

Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>

Author: SergiiDmytruk

grub-core/loader/i386/skinit.c

@@ -106,10 +106,10 @@ grub_skinit_boot_prepare (struct grub_relocator *rel,
   if (slb == NULL)
     return grub_error (GRUB_ERR_BAD_ARGUMENT, "SLB module is missing");
 
-  err = grub_relocator_alloc_chunk_align (rel, &ch, 0x1000000,
-                                          0xffffffff - GRUB_SLAUNCH_TPM_EVT_LOG_SIZE,
-                                          GRUB_SLAUNCH_TPM_EVT_LOG_SIZE, GRUB_PAGE_SIZE,
-                                          GRUB_RELOCATOR_PREFERENCE_NONE, 1);
+  err = grub_relocator_alloc_chunk_align_safe (rel, &ch, 0x1000000,
+                                               UP_TO_TOP32(GRUB_SLAUNCH_TPM_EVT_LOG_SIZE),
+                                               GRUB_SLAUNCH_TPM_EVT_LOG_SIZE, GRUB_PAGE_SIZE,
+                                               GRUB_RELOCATOR_PREFERENCE_HIGH, 1);
 
   if (err != GRUB_ERR_NONE)
     return grub_error (err, "cannot alloc memory for TPM event log");