[xen staging-4.13] x86/EFI: suppress GNU ld 2.36'es creation of base relocs

[patchbot@xxxxxxx]

commit a4c4fc0de3bd5c6847a2b8077a02ea6e9d26bab0
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Mar 5 15:48:06 2021 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Mar 5 15:48:06 2021 +0100

    x86/EFI: suppress GNU ld 2.36'es creation of base relocs
    
    All of the sudden ld creates base relocations itself, for PE
    executables - as a result we now have two of them for every entity to
    be relocated. While we will likely want to use this down the road, it
    doesn't work quite right yet in corner cases, so rather than suppressing
    our own way of creating the relocations we need to tell ld to avoid
    doing so.
    
    Probe whether --disable-reloc-section (which was introduced by the same
    commit making relocation generation the default) is recognized by ld's PE
    emulation, and use the option if so. (To limit redundancy, move the first
    part of setting EFI_LDFLAGS earlier, and use it already while probing.)
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 76cbb9c3f4dd9ab6aa44eeacab84fb88b2e8bfc1
    master date: 2021-02-25 15:11:58 +0100
---
 xen/arch/x86/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 4212eb1d93..c57ae581dd 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -173,8 +173,13 @@ EFI_LDFLAGS += --major-subsystem-version=2 
--minor-subsystem-version=0
 # Check if the compiler supports the MS ABI.
 export XEN_BUILD_EFI := $(shell $(CC) $(filter-out $(CFLAGS-y) .%.d,$(CFLAGS)) 
-c efi/check.c -o efi/check.o 2>/dev/null && echo y)
 # Check if the linker supports PE.
-XEN_BUILD_PE := $(if $(XEN_BUILD_EFI),$(shell $(LD) -mi386pep --subsystem=10 
-S -o efi/check.efi efi/check.o 2>/dev/null && echo y))
+XEN_BUILD_PE := $(if $(XEN_BUILD_EFI),$(shell $(LD) $(call 
EFI_LDFLAGS,0x100000000) -o efi/check.efi efi/check.o 2>/dev/null && echo y))
 CFLAGS-$(XEN_BUILD_EFI) += -DXEN_BUILD_EFI
+# Check if the linker produces fixups in PE by default (we need to disable it 
doing so for now).
+XEN_NO_PE_FIXUPS := $(if $(XEN_BUILD_EFI), \
+                         $(shell $(LD) $(call EFI_LDFLAGS,0x100000000) 
--disable-reloc-section -o efi/check.efi efi/check.o 2>/dev/null && \
+                                 echo --disable-reloc-section))
+EFI_LDFLAGS += $(XEN_NO_PE_FIXUPS)
 
 $(TARGET).efi: VIRT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, A 
VIRT_START$$,,p')
 $(TARGET).efi: ALT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, A 
ALT_START$$,,p')
--
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