linux-kernel - Re: Odd build breakage in 4.9-rc7

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Message-ID: <1480599966.19457.4.camel@tiscali.nl>
Date:   Thu, 01 Dec 2016 14:46:06 +0100
From:   Paul Bolle <pebolle@...cali.nl>
To:     Jarod Wilson <jarod@...hat.com>,
        Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:     Tony Luck <tony.luck@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Prarit Bhargava <prarit@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: Odd build breakage in 4.9-rc7

On Thu, 2016-12-01 at 10:01 +0100, Paul Bolle wrote:
> Perhaps this is all documented somewhere. But even then it would be nice if
> the build would fail right at the start. Ie, the build probably should fail if
> one does "make bzImage" while having a .config with
>     CONFIG_TRIM_UNUSED_KSYMS=y
>     CONFIG_MODULES=y
>     # CONFIG_MODVERSIONS is not set
> 
> Because it seems in that case the subsequent "make modules" will then end in
> this flood of ERRORs. 

Or, alternatively, we could use something like the following hack to keep a
two step build (ie, "make bzImage" and "make modules") do the right thing even
if CONFING_MODVERSIONS is not set.

The hack was cobbled together with a fair amount of cargo-cult coding so
perhaps a hunk or two aren't really needed. We'll see.

Paul Bolle

diff --git a/Makefile b/Makefile
index 694111b43cf8..5820f803ca64 100644
--- a/Makefile
+++ b/Makefile
@@ -321,7 +321,7 @@ KBUILD_BUILTIN := 1
 # make sure the checksums are up to date before we record them.
 
 ifeq ($(MAKECMDGOALS),modules)
-  KBUILD_BUILTIN := $(if $(CONFIG_MODVERSIONS),1)
+  KBUILD_BUILTIN := $(if $(or $(CONFIG_MODVERSIONS),$(CONFIG_TRIM_UNUSED_KSYMS)),1)
 endif
 
 # If we have "make <whatever> modules", compile modules
diff --git a/scripts/Makefile b/scripts/Makefile
index 1d80897a9644..f23e5c4f2496 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -40,7 +40,9 @@ build_docproc: $(obj)/docproc
 build_check-lc_ctype: $(obj)/check-lc_ctype
 	@:
 
-subdir-$(CONFIG_MODVERSIONS) += genksyms
+ifeq ($(or $(CONFIG_MODVERSIONS),$(CONFIG_TRIM_UNUSED_KSYMS)),y)
+subdir-y                     += genksyms
+endif
 subdir-y                     += mod
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
 subdir-$(CONFIG_DTC)         += dtc
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 7675d11ee65e..50ce2cf86b7c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -182,7 +182,7 @@ $(obj)/%.symtypes : $(src)/%.c FORCE
 
 quiet_cmd_cc_o_c = CC $(quiet_modtag)  $@
 
-ifndef CONFIG_MODVERSIONS
+ifneq ($(if $(CONFIG_MODVERSIONS),1,$(if $(CONFIG_TRIM_UNUSED_KSYMS),1)),1)
 cmd_cc_o_c = $(CC) $(c_flags) -c -o $@ $<
 
 else
@@ -358,7 +358,7 @@ $(obj)/%.s: $(src)/%.S FORCE
 
 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 
-ifndef CONFIG_MODVERSIONS
+ifneq ($(if $(CONFIG_MODVERSIONS),1,$(if $(CONFIG_TRIM_UNUSED_KSYMS),1)),1)
 cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
 
 else
diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh
index 8dc1918b6783..7525da1cc2f7 100755
--- a/scripts/adjust_autoksyms.sh
+++ b/scripts/adjust_autoksyms.sh
@@ -68,7 +68,7 @@ while read sym; do
 done >> "$new_ksyms_file"
 
 # Special case for modversions (see modpost.c)
-if [ -n "$CONFIG_MODVERSIONS" ]; then
+if [ -n "$CONFIG_MODVERSIONS" -o -n "$CONFIG_TRIM_UNUSED_KSYMS" ]; then
 	echo "#define __KSYM_module_layout 1" >> "$new_ksyms_file"
 fi