[XEN PATCH 1/3] xen/arch/x86: don't insert timestamp when SOURCE_DATE_EPOCH is defined

[Maximilian Engelhardt <maxi@xxxxxxxxxxxxx>]

By default a timestamp gets added to the xen efi binary. Unfortunately
ld doesn't seem to provide a way to set a custom date, like from
SOURCE_DATE_EPOCH, so set a zero value for the timestamp (option
--no-insert-timestamp) if SOURCE_DATE_EPOCH is defined. This makes
reproducible builds possible.

This is an alternative to the patch suggested in [1]. This patch only
omits the timestamp when SOURCE_DATE_EPOCH is defined.

[1] https://lists.xenproject.org/archives/html/xen-devel/2020-10/msg02161.html

Signed-off-by: Maximilian Engelhardt <maxi@xxxxxxxxxxxxx>
---
 xen/arch/x86/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 8f2180485b..863aed043f 100644
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -184,6 +184,12 @@ EFI_LDFLAGS += --major-image-version=$(XEN_VERSION)
 EFI_LDFLAGS += --minor-image-version=$(XEN_SUBVERSION)
 EFI_LDFLAGS += --major-os-version=2 --minor-os-version=0
 EFI_LDFLAGS += --major-subsystem-version=2 --minor-subsystem-version=0
+# It seems ld unfortunately can't set a custom timestamp, so add a zero value
+# for the timestamp (option --no-insert-timestamp) if SOURCE_DATE_EPOCH is
+# defined to make reproducible builds possible.
+ifdef SOURCE_DATE_EPOCH
+EFI_LDFLAGS += --no-insert-timestamp
+endif
 
 $(TARGET).efi: VIRT_BASE = 0x$(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')
-- 
2.20.1