This is a note to let you know that I've just added the patch titled kbuild: sink stdout from cmd for silent build to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kbuild-sink-stdout-from-cmd-for-silent-build.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit f268cf5e0faf747dd7dcdb32ca3c2e45b404b09e Author: Masahiro Yamada <masahiroy@xxxxxxxxxx> Date: Mon May 17 16:03:13 2021 +0900 kbuild: sink stdout from cmd for silent build [ Upstream commit 174a1dcc96429efce4ef7eb2f5c4506480da2182 ] When building with 'make -s', no output to stdout should be printed. As Arnd Bergmann reported [1], mkimage shows the detailed information of the generated images. I think this should be suppressed by the 'cmd' macro instead of by individual scripts. Insert 'exec >/dev/null;' in order to redirect stdout to /dev/null for silent builds. [Note about this implementation] 'exec >/dev/null;' may look somewhat tricky, but this has a reason. Appending '>/dev/null' at the end of command line is a common way for redirection, so I first tried this: cmd = @set -e; $(echo-cmd) $(cmd_$(1)) >/dev/null ... but it would not work if $(cmd_$(1)) itself contains a redirection. For example, cmd_wrap in scripts/Makefile.asm-generic redirects the output from the 'echo' command into the target file. It would be expanded into: echo "#include <asm-generic/$*.h>" > $@ >/dev/null Then, the target file gets empty because the string will go to /dev/null instead of $@. Next, I tried this: cmd = @set -e; $(echo-cmd) { $(cmd_$(1)); } >/dev/null The form above would be expanded into: { echo "#include <asm-generic/$*.h>" > $@; } >/dev/null This works as expected. However, it would be a syntax error if $(cmd_$(1)) is empty. When CONFIG_TRIM_UNUSED_KSYMS is disabled, $(call cmd,gen_ksymdeps) in scripts/Makefile.build would be expanded into: set -e; { ; } >/dev/null ..., which causes an syntax error. I also tried this: cmd = @set -e; $(echo-cmd) ( $(cmd_$(1)) ) >/dev/null ... but this causes a syntax error for the same reason. So, finally I adopted: cmd = @set -e; $(echo-cmd) exec >/dev/null; $(cmd_$(1)) [1]: https://lore.kernel.org/lkml/20210514135752.2910387-1-arnd@xxxxxxxxxx/ Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 7da10afc92c6..b14a7d4a2f05 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -182,8 +182,13 @@ clean := -f $(srctree)/scripts/Makefile.clean obj echo-cmd = $(if $($(quiet)cmd_$(1)),\ echo ' $(call escsq,$($(quiet)cmd_$(1)))$(echo-why)';) +# sink stdout for 'make -s' + redirect := + quiet_redirect := +silent_redirect := exec >/dev/null; + # printing commands -cmd = @set -e; $(echo-cmd) $(cmd_$(1)) +cmd = @set -e; $(echo-cmd) $($(quiet)redirect) $(cmd_$(1)) ### # if_changed - execute command if any prerequisite is newer than