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
