[Xen-changelog] [xen stable-4.7] x86/EFI: don't apply relocations to l{2, 3}_bootmap

[patchbot@xxxxxxx]

commit fd7306fc6a134fb2db648406dd720a34f3e5d231
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Aug 26 10:20:20 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Aug 26 10:20:20 2016 +0200

    x86/EFI: don't apply relocations to l{2,3}_bootmap
    
    Other than claimed in commit 2ce5963727's ("x86: construct the
    {l2,l3}_bootmap at compile time") the initialization of the two page
    tables doesn't take care of everything without furher adjustment: The
    compile time initialization obviously requires base relocations, and
    those get processed after efi_arch_memory_setup(). Hence without
    additional care the correctly initialized values may then get wrongly
    "adjusted" again. Except the two table from being subject to base
    relocation.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper@xxxxxxxxxx>
    master commit: c5b4805bcd6bc749a8717e7406faa4a0e95468b4
    master date: 2016-08-19 17:03:33 +0200
---
 xen/arch/x86/efi/efi-boot.h | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index 1fa9e47..2ae4de1 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -47,11 +47,23 @@ static void __init efi_arch_relocate_image(unsigned long 
delta)
 
     for ( base_relocs = __base_relocs_start; base_relocs < __base_relocs_end; )
     {
-        unsigned int i, n;
+        unsigned int i = 0, n;
 
         n = (base_relocs->size - sizeof(*base_relocs)) /
             sizeof(*base_relocs->entries);
-        for ( i = 0; i < n; ++i )
+
+        /*
+         * Relevant l{2,3}_bootmap entries get initialized explicitly in
+         * efi_arch_memory_setup(), so we must not apply relocations there.
+         * l2_identmap's first slot, otoh, should be handled normally, as
+         * efi_arch_memory_setup() won't touch it (xen_phys_start should
+         * never be zero).
+         */
+        if ( xen_phys_start + base_relocs->rva == (unsigned long)l3_bootmap ||
+             xen_phys_start + base_relocs->rva == (unsigned long)l2_bootmap )
+            i = n;
+
+        for ( ; i < n; ++i )
         {
             unsigned long addr = xen_phys_start + base_relocs->rva +
                                  (base_relocs->entries[i] & 0xfff);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.7

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