Re: [XEN PATCH 2/5] docs: set DATE to SOURCE_DATE_EPOCH if available

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 30/12/2024 9:00 pm, Maximilian Engelhardt wrote:
> Use the solution described in [1] to replace the call to the 'date'
> command with a version that uses SOURCE_DATE_EPOCH if available. This
> is needed for reproducible builds.
>
> The -d "@..." syntax was introduced in GNU date about 2005 (but only
> added to the docuemntation in 2011), so I assume a version supporting
> this syntax is available, if SOURCE_DATE_EPOCH is defined. If
> SOURCE_DATE_EPOCH is not defined, nothing changes with respect to the
> current behavior.
>
> [1] https://reproducible-builds.org/docs/source-date-epoch/
>
> Signed-off-by: Maximilian Engelhardt <maxi@xxxxxxxxxxxxx>
> ---
>  docs/Makefile | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/docs/Makefile b/docs/Makefile
> index b30cc619f8..beba02a94f 100644
> --- a/docs/Makefile
> +++ b/docs/Makefile
> @@ -3,7 +3,13 @@ include $(XEN_ROOT)/Config.mk
>  -include $(XEN_ROOT)/config/Docs.mk
>  
>  VERSION              := $(shell $(MAKE) -C $(XEN_ROOT)/xen 
> --no-print-directory xenversion)
> -DATE         := $(shell date +%Y-%m-%d)
> +
> +DATE_FMT     := +%Y-%m-%d
> +ifdef SOURCE_DATE_EPOCH
> +DATE         := $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" "$(DATE_FMT)" 
> 2>/dev/null || date -u -r "$(SOURCE_DATE_EPOCH)" "$(DATE_FMT)" 2>/dev/null || 
> date -u "$(DATE_FMT)")
> +else
> +DATE         := $(shell date "$(DATE_FMT)")
> +endif
>  
>  DOC_ARCHES      := arm x86_32 x86_64
>  MAN_SECTIONS    := 1 5 7 8

While this looks fine for docs, there's another (identical) use of date
in tools/firmware/hvmloader/Makefile, as well as some differing uses to
construct XEN_BUILD_{DATE,TIME}.  INSTALL talks about VGABIOS_REL_DATE too.

Does something like this work for you?  It seems to DTRT for SMBIOS.  It
needs adapting a bit more for vgabios and Xen, but I think having one
common $(date) is going to be better than ad-hoc ones over the tree.

~Andrew

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