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authorMasahiro Yamada <yamada.masahiro@socionext.com>2019-07-17 15:17:57 +0900
committerMasahiro Yamada <yamada.masahiro@socionext.com>2019-07-18 02:19:31 +0900
commitb7dca6dd1e591ad19a9aae716f3898be8063f880 (patch)
tree34d1ad73abe2f2c3a9f359927718e1604cf8ff58 /Makefile
parent7deb55f57159f9de696ef8d5e93b201a6aba871c (diff)
kbuild: create *.mod with full directory path and remove MODVERDIR
While descending directories, Kbuild produces objects for modules, but do not link final *.ko files; it is done in the modpost. To keep track of modules, Kbuild creates a *.mod file in $(MODVERDIR) for every module it is building. Some post-processing steps read the necessary information from *.mod files. This avoids descending into directories again. This mechanism was introduced in 2003 or so. Later, commit 551559e13af1 ("kbuild: implement modules.order") added modules.order. So, we can simply read it out to know all the modules with directory paths. This is easier than parsing the first line of *.mod files. $(MODVERDIR) has a flat directory structure, that is, *.mod files are named only with base names. This is based on the assumption that the module name is unique across the tree. This assumption is really fragile. Stephen Rothwell reported a race condition caused by a module name conflict: https://lkml.org/lkml/2019/5/13/991 In parallel building, two different threads could write to the same $(MODVERDIR)/*.mod simultaneously. Non-unique module names are the source of all kind of troubles, hence commit 3a48a91901c5 ("kbuild: check uniqueness of module names") introduced a new checker script. However, it is still fragile in the build system point of view because this race happens before scripts/modules-check.sh is invoked. If it happens again, the modpost will emit unclear error messages. To fix this issue completely, create *.mod with full directory path so that two threads never attempt to write to the same file. $(MODVERDIR) is no longer needed. Since modules with directory paths are listed in modules.order, Kbuild is still able to find *.mod files without additional descending. I also killed cmd_secanalysis; scripts/mod/sumversion.c computes MD4 hash for modules with MODULE_VERSION(). When CONFIG_DEBUG_SECTION_MISMATCH=y, it occurs not only in the modpost stage, but also during directory descending, where sumversion.c may parse stale *.mod files. It would emit 'No such file or directory' warning when an object consisting a module is renamed, or when a single-obj module is turned into a multi-obj module or vice versa. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> Acked-by: Nicolas Pitre <nico@fluxnic.net>
Diffstat (limited to 'Makefile')
-rw-r--r--Makefile20
1 files changed, 3 insertions, 17 deletions
diff --git a/Makefile b/Makefile
index d9103e731187..6308c8cea121 100644
--- a/Makefile
+++ b/Makefile
@@ -486,11 +486,6 @@ export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
export KBUILD_ARFLAGS
-# When compiling out-of-tree modules, put MODVERDIR in the module
-# tree rather than in the kernel tree. The kernel tree might
-# even be read-only.
-export MODVERDIR := $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/).tmp_versions
-
# Files to ignore in find ... statements
export RCS_FIND_IGNORE := \( -name SCCS -o -name BitKeeper -o -name .svn -o \
@@ -1029,8 +1024,8 @@ vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_OBJS) $(KBUILD_VMLINUX_LIBS)
# Recurse until adjust_autoksyms.sh is satisfied
PHONY += autoksyms_recursive
-autoksyms_recursive: $(vmlinux-deps)
ifdef CONFIG_TRIM_UNUSED_KSYMS
+autoksyms_recursive: $(vmlinux-deps) modules.order
$(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \
"$(MAKE) -f $(srctree)/Makefile vmlinux"
endif
@@ -1113,7 +1108,6 @@ endif
prepare1: prepare3 outputmakefile asm-generic $(version_h) $(autoksyms_h) \
include/generated/utsrelease.h
- $(cmd_crmodverdir)
archprepare: archheaders archscripts prepare1 scripts
@@ -1371,7 +1365,7 @@ endif # CONFIG_MODULES
# make distclean Remove editor backup files, patch leftover files and the like
# Directories & files removed with 'make clean'
-CLEAN_DIRS += $(MODVERDIR) include/ksym
+CLEAN_DIRS += include/ksym
CLEAN_FILES += modules.builtin.modinfo
# Directories & files removed with 'make mrproper'
@@ -1641,7 +1635,6 @@ PHONY += $(clean-dirs) clean
$(clean-dirs):
$(Q)$(MAKE) $(clean)=$(patsubst _clean_%,%,$@)
-clean: rm-dirs := $(MODVERDIR)
clean: rm-files := $(KBUILD_EXTMOD)/Module.symvers
PHONY += help
@@ -1655,8 +1648,6 @@ help:
@echo ''
PHONY += prepare
-prepare:
- $(cmd_crmodverdir)
endif # KBUILD_EXTMOD
clean: $(clean-dirs)
@@ -1667,7 +1658,7 @@ clean: $(clean-dirs)
-o -name '*.ko.*' \
-o -name '*.dtb' -o -name '*.dtb.S' -o -name '*.dt.yaml' \
-o -name '*.dwo' -o -name '*.lst' \
- -o -name '*.su' \
+ -o -name '*.su' -o -name '*.mod' \
-o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
-o -name '*.lex.c' -o -name '*.tab.[ch]' \
-o -name '*.asn1.[ch]' \
@@ -1794,11 +1785,6 @@ quiet_cmd_depmod = DEPMOD $(KERNELRELEASE)
cmd_depmod = $(CONFIG_SHELL) $(srctree)/scripts/depmod.sh $(DEPMOD) \
$(KERNELRELEASE)
-# Create temporary dir for module support files
-# clean it up only when building all modules
-cmd_crmodverdir = $(Q)mkdir -p $(MODVERDIR) \
- $(if $(KBUILD_MODULES),; rm -f $(MODVERDIR)/*)
-
# read saved command lines for existing targets
existing-targets := $(wildcard $(sort $(targets)))