x86/EFI: don't insert timestamp when SOURCE_DATE_EPOCH is defined

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@daemonizer.de>
Acked-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit ee41b5c450032ae7f2531e18cd0a73bf5fb48803)

diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
index 26ff2a9a3e69981e738c148ecb2440e57309e0f1..a51f9166b751a15da3941382ebe3eb82e8a05858 100644 (file)
--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -172,6 +172,12 @@ 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
 
 # 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)