[PATCH AUTOSEL 5.7 322/388] modpost: fix -i (--ignore-errors) MAKEFLAGS detection

[Sasha Levin]

From: Masahiro Yamada <masahiroy@xxxxxxxxxx>

[ Upstream commit 91e6ee581270b8ae970f028b898314d73f16870b ]

$(filter -i,$(MAKEFLAGS)) works only in limited use-cases.

The representation of $(MAKEFLAGS) depends on various factors:
  - GNU Make version (version 3.8x or version 4.x)
  - The presence of other flags like -j

In my experiments, $(MAKEFLAGS) is expanded as follows:

  * GNU Make 3.8x:

    * without -j option:
      --no-print-directory -Rri

    * with -j option:
      --no-print-directory -Rr --jobserver-fds=3,4 -j -i

  * GNU Make 4.x:

    * without -j option:
      irR --no-print-directory

    * with -j option:
      irR -j --jobserver-fds=3,4 --no-print-directory

For GNU Make 4.x, the flags are grouped as 'irR', which does not work.

For the single thread build with GNU Make 3.8x, the flags are grouped
as '-Rri', which does not work either.

To make it work for all cases, do likewise as commit 6f0fa58e4596
("kbuild: simplify silent build (-s) detection").

BTW, since commit ff9b45c55b26 ("kbuild: modpost: read modules.order
instead of $(MODVERDIR)/*.mod"), you also need to pass -k option to
build final *.ko files. 'make -i -k' ignores compile errors in modules,
and build as many remaining *.ko as possible.

Please note this feature is kind of dangerous if other modules depend
on the broken module because the generated modules will lack the correct
module dependency or CRC. Honestly, I am not a big fan of it, but I am
keeping this feature.

Fixes: eed380f3f593 ("modpost: Optionally ignore secondary errors seen if a single module build fails")
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 scripts/Makefile.modpost | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 957eed6a17a5..33aaa572f686 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -66,7 +66,7 @@ __modpost:
 
 else
 
-MODPOST += $(subst -i,-n,$(filter -i,$(MAKEFLAGS))) -s -T - \
+MODPOST += -s -T - \
 	$(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS))
 
 ifeq ($(KBUILD_EXTMOD),)
@@ -82,6 +82,11 @@ include $(if $(wildcard $(KBUILD_EXTMOD)/Kbuild), \
              $(KBUILD_EXTMOD)/Kbuild, $(KBUILD_EXTMOD)/Makefile)
 endif
 
+# 'make -i -k' ignores compile errors, and builds as many modules as possible.
+ifneq ($(findstring i,$(filter-out --%,$(MAKEFLAGS))),)
+MODPOST += -n
+endif
+
 # find all modules listed in modules.order
 modules := $(sort $(shell cat $(MODORDER)))
 
-- 
2.25.1