[PATCH] kbuild: Improved external module support
From: Sam Ravnborg
Date: Tue Apr 20 2004 - 17:39:32 EST
The external module support recently introduced caused a number of problems:
- To build an external module the Module.symvers file was needed
- To create the Module.symvers file a module was required
- If Module.symvers was missing kbuild boiled out with an error
- If vmlinux was missing also the stage 2 of module build failed (make -k)
- It was not documented what was needed to actually bauild a module
The following patch addresses this by adding the following functionality:
- Always generate the Module.symvers file
- Ignore a missing Module.symvers file
- Add a new target modules_prepare, it prepares the kernel for building
external modules, and is also usefull with O=
- And it adds some more comments to Makefile.modpost, so others may follow
it with some luck
- .modpost.cmd is no longer generated
This should close all reports on issues with respect to building
external modules with current kernel - which has been identified
as kernel problems.
Sam
===== Makefile 1.480 vs edited =====
--- 1.480/Makefile Thu Apr 15 03:31:15 2004
+++ edited/Makefile Tue Apr 20 22:32:25 2004
@@ -715,8 +715,12 @@
@echo ' Building modules, stage 2.';
$(Q)$(MAKE) -rR -f $(srctree)/scripts/Makefile.modpost
-# Install modules
+# Target to prepare building external modules
+.PHONY: modules_prepare
+modules_prepare: prepare-all scripts
+
+# Target to install modules
.PHONY: modules_install
modules_install: _modinst_ _modinst_post
===== scripts/Makefile.modpost 1.9 vs edited =====
--- 1.9/scripts/Makefile.modpost Mon Apr 12 19:55:33 2004
+++ edited/scripts/Makefile.modpost Tue Apr 20 22:25:35 2004
@@ -1,34 +1,71 @@
# ===========================================================================
# Module versions
# ===========================================================================
+#
+# Stage one of module building created the following:
+# a) The individual .o files used for the module
+# b) A <module>.o file wich is the .o files above linked together
+# c) A <module>.mod file in $(MODVERDIR)/, listing the name of the
+# the preliminary <module>.o file, plus all .o files
+
+# Stage 2 is handled by this file and does the following
+# 1) Find all modules from the files listed in $(MODVERDIR)/
+# 2) modpost is then used to
+# 3) create one <module>.mod.c file pr. module
+# 4) create one Module.symvers file with CRC for all exported symbols
+# 5) compile all <module>.mod.c files
+# 6) final link of the module to a <module.ko> file
+
+# Step 3 is used to place certain information in the module's ELF
+# section, including information such as:
+# Version magic (see include/vermagic.h for full details)
+# - Kernel release
+# - SMP is CONFIG_SMP
+# - PREEMPT is CONFIG_PREEMPT
+# - GCC Version
+# Module info
+# - Module version (MODULE_VERSION)
+# - Module alias'es (MODULE_ALIAS)
+# - Module license (MODULE_LICENSE)
+# - See include/linux/module.h for more details
+
+# Step 4 is solely used to allow module versioning in external modules,
+# where the CRC of each module is retreived from the Module.symers file.
-.PHONY: __modversions
-__modversions:
+.PHONY: _modpost
+_modpost: __modpost
include .config
include scripts/Makefile.lib
-#
+symverfile := $(objtree)/Module.symvers
+# Step 1), find all modules listed in $(MODVERDIR)/
__modules := $(shell head -q -n1 /dev/null $(wildcard $(MODVERDIR)/*.mod))
-modules := $(patsubst %.o,%.ko,$(wildcard $(__modules:.ko=.o)))
+modules := $(patsubst %.o,%.ko, $(wildcard $(__modules:.ko=.o)))
-__modversions: $(modules)
- @:
+_modpost: $(modules)
-# The final module link
-quiet_cmd_ld_ko_o = LD [M] $@
- cmd_ld_ko_o = $(LD) $(LDFLAGS) $(LDFLAGS_MODULE) -o $@ \
- $(filter-out FORCE,$^)
+# Step 2), invoke modpost
+# Includes step 3,4
+quiet_cmd_modpost = MODPOST
+ cmd_modpost = scripts/modpost \
+ $(if $(KBUILD_EXTMOD),-i,-o) $(symverfile) \
+ $(filter-out FORCE,$^)
-$(modules): %.ko :%.o %.mod.o FORCE
- $(call if_changed,ld_ko_o)
+.PHONY: __modpost
+__modpost: $(wildcard vmlinux) $(modules:.ko=.o) FORCE
+ $(call cmd,modpost)
+
+# Declare generated files as targets for modpost
+$(symverfile): __modpost ;
+$(modules:.ko=.mod.c): __modpost ;
-targets += $(modules)
-# Compile version info for unresolved symbols
+# Step 5), compile all *.mod.c files
+# modname is set to make c_flags define KBUILD_MODNAME
modname = $(*F)
quiet_cmd_cc_o_c = CC $@
@@ -40,23 +77,16 @@
targets += $(modules:.ko=.mod.o)
-# All the .mod.c files are generated using the helper "modpost"
-
-.PHONY: __modpost
-
-$(modules:.ko=.mod.c): __modpost ;
-
-# Extract all checksums for all exported symbols
+# Step 6), final link of the modules
+quiet_cmd_ld_ko_o = LD [M] $@
+ cmd_ld_ko_o = $(LD) $(LDFLAGS) $(LDFLAGS_MODULE) -o $@ \
+ $(filter-out FORCE,$^)
-quiet_cmd_modpost = MODPOST
- cmd_modpost = scripts/modpost \
- $(if $(filter vmlinux,$^),-o,-i) $(objtree)/Module.symvers \
- $(filter-out FORCE,$^)
+$(modules): %.ko :%.o %.mod.o FORCE
+ $(call if_changed,ld_ko_o)
-__modpost: $(if $(KBUILD_EXTMOD),,$(wildcard vmlinux)) $(modules:.ko=.o) FORCE
- $(call if_changed,modpost)
+targets += $(modules)
-targets += __modpost
# Add FORCE to the prequisites of a target to force it to be always rebuilt.
# ---------------------------------------------------------------------------
===== scripts/modpost.c 1.27 vs edited =====
--- 1.27/scripts/modpost.c Sun Apr 18 18:13:09 2004
+++ edited/scripts/modpost.c Tue Apr 20 22:28:29 2004
@@ -625,10 +625,9 @@
void *file = grab_file(fname, &size);
char *line;
- if (!file) {
- perror(fname);
- abort();
- }
+ if (!file)
+ /* No symbol versions, silently ignore */
+ return;
while ((line = get_next_line(&pos, file, size))) {
char *symname, *modname, *d;
-
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