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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH 6/8] x86/EFI: avoid use of GNU ld's --disable-reloc-section when possible
As of commit 6fa7408d72b3 ("ld: don't generate base relocations in PE
output for absolute symbols") I'm feeling sufficiently confident in GNU
ld to use its logic for generating base relocations, which was enabled
for executables at some point last year (prior to that this would have
got done only for DLLs).
GNU ld, seeing the original relocations coming from the ELF object files,
generates different relocation types for our page tables (64-bit ones,
while mkreloc produces 32-bit ones). This requires also permitting and
handling that type in efi_arch_relocate_image().
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -120,18 +120,37 @@ $(TARGET): $(TARGET)-syms $(efi-y) boot/
mv $(TMP) $(TARGET)
ifneq ($(efi-y),)
+
# Check if the compiler supports the MS ABI.
export XEN_BUILD_EFI := $(shell $(CC) $(XEN_CFLAGS) -c efi/check.c -o
efi/check.o 2>/dev/null && echo y)
+CFLAGS-$(XEN_BUILD_EFI) += -DXEN_BUILD_EFI
+
# Check if the linker supports PE.
EFI_LDFLAGS = $(patsubst -m%,-mi386pep,$(XEN_LDFLAGS)) --subsystem=10
--strip-debug
XEN_BUILD_PE := $(if $(XEN_BUILD_EFI),$(shell $(LD) $(EFI_LDFLAGS) -o
efi/check.efi efi/check.o 2>/dev/null && echo y))
-CFLAGS-$(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) $(EFI_LDFLAGS) --disable-reloc-section
-o efi/check.efi efi/check.o 2>/dev/null && \
- echo --disable-reloc-section))
+
+ifeq ($(XEN_BUILD_PE),y)
+
+# Check if the linker produces fixups in PE by default
+nr-fixups := $(shell $(OBJDUMP) -p efi/check.efi | grep
'^[[:blank:]]*reloc[[:blank:]]*[0-9][[:blank:]].*DIR64$$' | wc -l)
+ifeq ($(nr-fixups),2)
+MKRELOC := :
+relocs-dummy :=
+else
+MKRELOC := efi/mkreloc
+relocs-dummy := efi/relocs-dummy.o
+# If the linker produced fixups but not precisely two of them, we need to
+# disable it doing so. But if it didn't produce any fixups, it also wouldn't
+# recognize the option.
+ifneq ($(nr-fixups),0)
+EFI_LDFLAGS += --disable-reloc-section
+endif
endif
+endif # $(XEN_BUILD_PE)
+
+endif # $(efi-y)
+
ALL_OBJS := $(BASEDIR)/arch/x86/boot/built_in.o
$(BASEDIR)/arch/x86/efi/built_in.o $(ALL_OBJS)
ifeq ($(CONFIG_LTO),y)
@@ -175,7 +194,7 @@ note.o: $(TARGET)-syms
--rename-section=.data=.note.gnu.build-id -S $@.bin $@
rm -f $@.bin
-EFI_LDFLAGS += --image-base=$(1) --stack=0,0 --heap=0,0 $(XEN_NO_PE_FIXUPS)
+EFI_LDFLAGS += --image-base=$(1) --stack=0,0 --heap=0,0
EFI_LDFLAGS += --section-alignment=0x200000 --file-alignment=0x20
EFI_LDFLAGS += --major-image-version=$(XEN_VERSION)
EFI_LDFLAGS += --minor-image-version=$(XEN_SUBVERSION)
@@ -189,7 +208,11 @@ EFI_LDFLAGS += --no-insert-timestamp
endif
$(TARGET).efi: VIRT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, A
VIRT_START$$,,p')
+ifeq ($(MKRELOC),:)
+$(TARGET).efi: ALT_BASE :=
+else
$(TARGET).efi: ALT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, A
ALT_START$$,,p')
+endif
ifneq ($(build_id_linker),)
ifeq ($(call ld-ver-build-id,$(LD) $(filter -m%,$(EFI_LDFLAGS))),y)
@@ -210,16 +233,16 @@ note_file_option ?= $(note_file)
ifeq ($(XEN_BUILD_PE),y)
$(TARGET).efi: prelink.o $(note_file) efi.lds efi/relocs-dummy.o efi/mkreloc
$(foreach base, $(VIRT_BASE) $(ALT_BASE), \
- $(LD) $(call EFI_LDFLAGS,$(base)) -T efi.lds -N $<
efi/relocs-dummy.o \
+ $(LD) $(call EFI_LDFLAGS,$(base)) -T efi.lds -N $<
$(relocs-dummy) \
$(BASEDIR)/common/symbols-dummy.o $(note_file_option)
-o $(@D)/.$(@F).$(base).0 &&) :
- efi/mkreloc $(foreach base,$(VIRT_BASE)
$(ALT_BASE),$(@D)/.$(@F).$(base).0) >$(@D)/.$(@F).0r.S
+ $(MKRELOC) $(foreach base,$(VIRT_BASE)
$(ALT_BASE),$(@D)/.$(@F).$(base).0) >$(@D)/.$(@F).0r.S
$(NM) -pa --format=sysv $(@D)/.$(@F).$(VIRT_BASE).0 \
| $(BASEDIR)/tools/symbols $(all_symbols) --sysv --sort
>$(@D)/.$(@F).0s.S
$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).0r.o $(@D)/.$(@F).0s.o
$(foreach base, $(VIRT_BASE) $(ALT_BASE), \
$(LD) $(call EFI_LDFLAGS,$(base)) -T efi.lds -N $< \
$(@D)/.$(@F).0r.o $(@D)/.$(@F).0s.o $(note_file_option)
-o $(@D)/.$(@F).$(base).1 &&) :
- efi/mkreloc $(foreach base,$(VIRT_BASE)
$(ALT_BASE),$(@D)/.$(@F).$(base).1) >$(@D)/.$(@F).1r.S
+ $(MKRELOC) $(foreach base,$(VIRT_BASE)
$(ALT_BASE),$(@D)/.$(@F).$(base).1) >$(@D)/.$(@F).1r.S
$(NM) -pa --format=sysv $(@D)/.$(@F).$(VIRT_BASE).1 \
| $(BASEDIR)/tools/symbols $(all_symbols) --sysv --sort
>$(@D)/.$(@F).1s.S
$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).1r.o $(@D)/.$(@F).1s.o
--- a/xen/arch/x86/efi/check.c
+++ b/xen/arch/x86/efi/check.c
@@ -2,3 +2,17 @@ int __attribute__((__ms_abi__)) test(int
{
return i;
}
+
+/*
+ * Populate an array with "addresses" of relocatable and absolute values.
+ * This is to probe ld for (a) emitting base relocations at all and (b) not
+ * emitting base relocations for absolute symbols.
+ */
+extern const unsigned char __image_base__[], __file_alignment__[],
+ __section_alignment__[];
+const void *const data[] = {
+ __image_base__,
+ __file_alignment__,
+ __section_alignment__,
+ data,
+};
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -86,10 +86,12 @@ static void __init efi_arch_relocate_ima
}
break;
case PE_BASE_RELOC_DIR64:
- if ( in_page_tables(addr) )
- blexit(L"Unexpected relocation type");
if ( delta )
+ {
*(u64 *)addr += delta;
+ if ( in_page_tables(addr) )
+ *(u64 *)addr += xen_phys_start;
+ }
break;
default:
blexit(L"Unsupported relocation type");
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