[PATCH V4] Makefile: Add build time and compiler info string

[Bin Meng]

Hi Wei,

On Thu, Sep 30, 2021 at 6:12 PM <wefu at redhat.com> wrote:
>
> From: Wei Fu <wefu at redhat.com>
>
> When we are doing opensbi development, we want to know the build time and
> compiler info for debug purpose.
> To enable this message, please add "BUILD_INFO=y", like:
>
> ```
> make BUILD_INFO=y
> ```
>
> NOTE: `BUILD_INFO=y` will violate "reproducible builds".
> So it's ONLY for development and debug purpose, and should NOT be used
> in a product which follows "reproducible builds".
>
> Signed-off-by: Wei Fu <wefu at redhat.com>
> ---
>  Makefile           | 31 +++++++++++++++++++++++++++++++
>  README.md          | 23 +++++++++++++++++++++++
>  lib/sbi/sbi_init.c |  8 ++++++++
>  3 files changed, 62 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index 16d9dca..0158e89 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -150,6 +150,25 @@ endif
>  # Check whether the linker supports creating PIEs
>  OPENSBI_LD_PIE := $(shell $(CC) $(CLANG_TARGET) $(RELAX_FLAG) $(USE_LD_FLAG) -fPIE -nostdlib -Wl,-pie -x c /dev/null -o /dev/null >/dev/null 2>&1 && echo y || echo n)
>
> +# Build Info:
> +# OPENSBI_BUILD_TIME_STAMP -- the compilation time stamp
> +# OPENSBI_BUILD_COMPILER_VERSION -- the compiler version info
> +BUILD_INFO ?= n
> +ifeq ($(BUILD_INFO),y)
> +OPENSBI_BUILD_DATE_FMT = +%Y-%m-%d-%H-%M-%S %Z

This hour/minute/second format seems uncommon. Also for %Z it is
ambiguous and not better than %z, e.g.: CST could mean different time
zones.

I would vote for: +%Y-%m-%d %H:%M:%S %z

> +ifdef SOURCE_DATE_EPOCH

With this approach, I don't think we need this BUILD_INFO=y thing, as
this macro can be set by distributions to produce a reproducible
build.

> +    OPENSBI_BUILD_TIME_STAMP ?= $(shell date -u -d "@$(SOURCE_DATE_EPOCH)" \
> +        "$(OPENSBI_BUILD_DATE_FMT)" 2>/dev/null || \
> +        date -u -r "$(SOURCE_DATE_EPOCH)" \
> +       "$(OPENSBI_BUILD_DATE_FMT)" 2>/dev/null || \
> +       date -u "$(OPENSBI_BUILD_DATE_FMT)")
> +else
> +    OPENSBI_BUILD_TIME_STAMP ?= $(shell date "$(OPENSBI_BUILD_DATE_FMT)")
> +endif
> +OPENSBI_BUILD_COMPILER_VERSION=$(shell $(CC) -v 2>&1 | grep ' version ' | \
> +       sed 's/[[:space:]]*$$//')
> +endif
> +
>  # Setup list of objects.mk files
>  ifdef PLATFORM
>  platform-object-mks=$(shell if [ -d $(platform_src_dir)/ ]; then find $(platform_src_dir) -iname "objects.mk" | sort -r; fi)
> @@ -247,6 +266,10 @@ GENFLAGS   +=      -I$(include_dir)
>  ifneq ($(OPENSBI_VERSION_GIT),)
>  GENFLAGS       +=      -DOPENSBI_VERSION_GIT="\"$(OPENSBI_VERSION_GIT)\""
>  endif
> +ifeq ($(BUILD_INFO),y)
> +GENFLAGS       +=      -DOPENSBI_BUILD_TIME_STAMP="\"$(OPENSBI_BUILD_TIME_STAMP)\""
> +GENFLAGS       +=      -DOPENSBI_BUILD_COMPILER_VERSION="\"$(OPENSBI_BUILD_COMPILER_VERSION)\""
> +endif
>  GENFLAGS       +=      $(libsbiutils-genflags-y)
>  GENFLAGS       +=      $(platform-genflags-y)
>  GENFLAGS       +=      $(firmware-genflags-y)
> @@ -398,6 +421,11 @@ $(build_dir)/%.dep: $(src_dir)/%.c
>  $(build_dir)/%.o: $(src_dir)/%.c
>         $(call compile_cc,$@,$<)
>
> +ifeq ($(BUILD_INFO),y)
> +$(build_dir)/lib/sbi/sbi_init.o: $(libsbi_dir)/sbi_init.c FORCE
> +       $(call compile_cc,$@,$<)
> +endif
> +
>  $(build_dir)/%.dep: $(src_dir)/%.S
>         $(call compile_as_dep,$@,$<)
>
> @@ -551,3 +579,6 @@ ifeq ($(install_root_dir),$(install_root_dir_default)/usr)
>         $(if $(V), @echo " RM        $(install_root_dir_default)")
>         $(CMD_PREFIX)rm -rf $(install_root_dir_default)
>  endif
> +
> +.PHONY: FORCE
> +FORCE:
> diff --git a/README.md b/README.md
> index 9fdf097..c498af0 100644
> --- a/README.md
> +++ b/README.md
> @@ -254,6 +254,28 @@ to produce broken binaries with missing relocations; it is therefore currently
>  recommended that this combination be avoided or *FW_PIC=n* be used to disable
>  building OpenSBI as a position-independent binary.
>
> +Building with timestamp and compiler info
> +-----------------------------------------
> +
> +When doing development, we may want to know the build time and compiler info
> +for debug purpose. OpenSBI can also be built with timestamp and compiler info.
> +To build with those info and print it out at boot time, we can just simply add
> +`BUILD_INFO=y`, like:
> +```
> +make BUILD_INFO=y
> +```
> +
> +But if you have used `BUILD_INFO=y`, and want to switch back to `BUILD_INFO=n`,
> +you must do
> +```
> +make clean
> +```
> +before the next build.
> +
> +NOTE: Using `BUILD_INFO=y` will violate [reproducible builds]. This definition
> +is ONLY for development and debug purpose, and should NOT be used in a product
> +which follows "reproducible builds".
> +
>  Contributing to OpenSBI
>  -----------------------
>
> @@ -336,3 +358,4 @@ make I=<install_directory> install_docs
>  [Doxygen manual]: http://www.doxygen.nl/manual/index.html
>  [Kendryte standalone SDK]: https://github.com/kendryte/kendryte-standalone-sdk
>  [third party notices]: ThirdPartyNotices.md
> +[reproducible builds]: https://reproducible-builds.org
> diff --git a/lib/sbi/sbi_init.c b/lib/sbi/sbi_init.c
> index f0eb365..a8fcec5 100644
> --- a/lib/sbi/sbi_init.c
> +++ b/lib/sbi/sbi_init.c
> @@ -48,6 +48,14 @@ static void sbi_boot_print_banner(struct sbi_scratch *scratch)
>                    OPENSBI_VERSION_MINOR);
>  #endif
>
> +#ifdef OPENSBI_BUILD_TIME_STAMP
> +       sbi_printf("Build time: %s\n", OPENSBI_BUILD_TIME_STAMP);
> +#endif
> +
> +#ifdef OPENSBI_BUILD_COMPILER_VERSION
> +       sbi_printf("Build compiler: %s\n", OPENSBI_BUILD_COMPILER_VERSION);
> +#endif
> +
>         sbi_printf(BANNER);
>  }
>

Regards,
Bin