kbuild: do section mismatch check on full vmlinux

Previously we did do the check on the .o files used to link
vmlinux but that failed to find questionable references across
the .o files.
Create a dedicated vmlinux.o file used only for section mismatch checks
that uses the defualt linker script so section does not get renamed.

The vmlinux.o may later be used as part of the the final link of vmlinux
but for now it is used fo section mismatch only.
For a defconfig build this is instant but for an allyesconfig this
add two minutes to a full build (that anyways takes ~2 hours).

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

2 files changed, 4 insertions, 3 deletions

diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index d5bbbcce31ef..c6fcc597b3be 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -70,10 +70,10 @@ __modpost: $(modules:.ko=.o) FORCE
         $(call cmd,modpost) $(wildcard vmlinux) $(filter-out FORCE,$^)
 
 quiet_cmd_kernel-mod = MODPOST $@
-      cmd_kernel-mod = $(cmd_modpost) $(KBUILD_VMLINUX_OBJS)
+      cmd_kernel-mod = $(cmd_modpost) $@
 
 PHONY += vmlinux
-vmlinux: FORCE
+vmlinux.o: FORCE
         $(call cmd,kernel-mod)
 
 # Declare generated files as targets for modpost
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index bb895b13c170..ec036c261fb1 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -75,7 +75,8 @@ static int is_vmlinux(const char *modname)
         else
                 myname = modname;
 
-        return strcmp(myname, "vmlinux") == 0;
+        return (strcmp(myname, "vmlinux") == 0) ||
+               (strcmp(myname, "vmlinux.o") == 0);
 }
 
 void *do_nofail(void *ptr, const char *expr)