[v3,2/2] Makefile: add check of binaries architecture

As shown recently by the firejail example, it is easy to miss that a
package builds and installs binaries without actually cross-compiling
them: they are built for the host architecture instead of the target
architecture.

This commit adds a small helper script, check-bin-arch, called as a
GLOBAL_INSTRUMENTATION_HOOKS at the end of the target installation of
each package, to verify that the files installed by this package have
been built for the correct architecture.

Being called as a GLOBAL_INSTRUMENTATION_HOOKS allows the build to error
out right after the installation of the faulty package, and therefore
get autobuilder error detection properly assigned to this specific
package.

Example output with the firejail package enabled, when building for an
ARM target:

ERROR: ./usr/lib/firejail/libconnect.so (from firejail) architecture is Advanced Micro Devices X86-64, should be ARM
ERROR: ./usr/bin/firejail (from firejail) architecture is Advanced Micro Devices X86-64, should be ARM
ERROR: ./usr/lib/firejail/libtrace.so (from firejail) architecture is Advanced Micro Devices X86-64, should be ARM
ERROR: ./usr/lib/firejail/libtracelog.so (from firejail) architecture is Advanced Micro Devices X86-64, should be ARM
ERROR: ./usr/lib/firejail/ftee (from firejail) architecture is Advanced Micro Devices X86-64, should be ARM
ERROR: ./usr/lib/firejail/faudit (from firejail) architecture is Advanced Micro Devices X86-64, should be ARM
ERROR: ./usr/bin/firemon (from firejail) architecture is Advanced Micro Devices X86-64, should be ARM
ERROR: ./usr/bin/firecfg (from firejail) architecture is Advanced Micro Devices X86-64, should be ARM
package/pkg-generic.mk:306: recipe for target '/home/thomas/projets/buildroot/output/build/firejail-0.9.44.8/.stamp_target_installed' failed
make[1]: *** [/home/thomas/projets/buildroot/output/build/firejail-0.9.44.8/.stamp_target_installed] Error 1

Many thanks to Yann E. Morin and Arnout Vandecappelle for their reviews
and suggestions.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
Changes since v2:
 - Moved as a per-package check, so that we detect the faulty package
   earlier, and get correct autobuilder notifications.
 - Use TARGET_DIR from the environment and use BR2_CONFIG to retrieve
   the value of BR2_READELF_ARCH_NAME.
 - Skip firmware files in /lib/firmware and /usr/lib/firmware.
 - Simply ignore files for which readelf returned an empty Machine
   field, as a way to quickly detect non-ELF files.

Changes since v1:
 - Following Yann E. Morin's comment, restrict the check to bin, lib,
   sbin, usr/bin, usr/lib and usr/sbin, in order to avoid matching
   firmware files that could use the ELF format but be targeted for
   other architectures.
---
 package/pkg-generic.mk         |  8 ++++++++
 support/scripts/check-bin-arch | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100755 support/scripts/check-bin-arch

Thomas, All,

On 2017-03-12 22:55 +0100, Thomas Petazzoni spake thusly:
> As shown recently by the firejail example, it is easy to miss that a
> package builds and installs binaries without actually cross-compiling
> them: they are built for the host architecture instead of the target
> architecture.
> 
> This commit adds a small helper script, check-bin-arch, called as a
> GLOBAL_INSTRUMENTATION_HOOKS at the end of the target installation of
> each package, to verify that the files installed by this package have
> been built for the correct architecture.
[--SNIP--]
> diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
> index e8a8021..71e3033 100644
> --- a/package/pkg-generic.mk
> +++ b/package/pkg-generic.mk
> @@ -87,6 +87,14 @@ define step_pkg_size
>  endef
>  GLOBAL_INSTRUMENTATION_HOOKS += step_pkg_size
>  
> +define check_bin_arch
> +	$(if $(filter end-install-target,$(1)-$(2)),\
> +		support/scripts/check-bin-arch $(3) \
> +			$(BUILD_DIR)/packages-file-list.txt $(TARGET_CROSS))

Also pass $(BR2_READELF_ARCH_NAME) directly from here, since we have it
in the Makefile, which would allow you...

> +endef
> +
> +GLOBAL_INSTRUMENTATION_HOOKS += check_bin_arch
> +
>  # This hook checks that host packages that need libraries that we build
>  # have a proper DT_RPATH or DT_RUNPATH tag
>  define check_host_rpath
> diff --git a/support/scripts/check-bin-arch b/support/scripts/check-bin-arch
> new file mode 100755
> index 0000000..4c94abe
> --- /dev/null
> +++ b/support/scripts/check-bin-arch
> @@ -0,0 +1,39 @@
> +#!/bin/bash
> +
> +PACKAGE=$1
> +PACKAGE_FILE_LIST=$2
> +TARGET_CROSS=$3
> +
> +exitcode=0
> +
> +READELF_ARCH_NAME=$(sed -r -e "/^BR2_READELF_ARCH_NAME=\"(.+)\"$/!d; s//\1/;" ${BR2_CONFIG})

... to get rid of this ugly code. ;-)

> +PKG_FILES=$(sed -r -e "/^${PACKAGE},(.+)$/!d; s//\1/;" ${PACKAGE_FILE_LIST})
> +
> +for f in ${PKG_FILES} ; do
> +	# Skip firmware files, they could be ELF files for other
> +	# architectures
> +	if [[ "${f}" =~ ^\./(usr/)?lib/firmware/.* ]]; then
> +		continue
> +	fi
> +
> +	# Get architecture using readelf
> +	arch=$(${TARGET_CROSS}readelf -h "${TARGET_DIR}/${f}" 2>&1 | \

As already said, runn that with LC_ALL=C.

> +		       sed -r -e '/^  Machine: +(.+)/!d; s//\1/;')
> +
> +	# If no architecture found, assume it was not an ELF file
> +	if test "${arch}" = "" ; then
> +		continue
> +	fi
> +
> +	# Architecture is correct
> +	if test "${arch}" = "${READELF_ARCH_NAME}" ; then
> +		continue
> +	fi
> +
> +	printf 'ERROR: %s (from %s) architecture is %s, should be %s\n' \

The grammar is not nice here. What about:

    "ERROR: architecture for %s (from %s) is %s, should be %s\n"

Otherwise, looks good. :-)

Regards,
Yann E. MORIN.

> +	       "${f}" "${PACKAGE}" "${arch}" "${READELF_ARCH_NAME}"
> +
> +	exitcode=1
> +done
> +
> +exit ${exitcode}
> -- 
> 2.7.4
>