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    Subject[PATCH] kbuild: implement modules.order
    When multiple built-in modules (especially drivers) provide the same
    capability, they're prioritized by link order specified by the order
    listed in Makefile. This implicit ordering is lost for loadable
    modules.

    When driver modules are loaded by udev, what comes first in
    modules.alias file is selected. However, the order in this file is
    indeterministic (depends on filesystem listing order of installed
    modules). This causes confusion.

    The solution is two-parted. This patch updates kbuild such that it
    generates and installs modules.order which contains the name of
    modules ordered according to Makefile. The second part is update to
    depmod such that it generates output files according to this file.

    Note that both obj-y and obj-m subdirs can contain modules and
    ordering information between those two are lost from beginning.
    Currently obj-y subdirs are put before obj-m subdirs.

    Signed-off-by: Tejun Heo <htejun@gmail.com>
    Cc: Bill Nottingham <notting@redhat.com>
    Cc: Rusty Russell <rusty@rustcorp.com.au>
    Cc: Greg Kroah-Hartman <gregkh@suse.de>
    Cc: Kay Sievers <kay.sievers@vrfy.org>
    ---
    Makefile | 5 ++
    scripts/Makefile | 1
    scripts/Makefile.build | 16 +++++++-
    scripts/Makefile.lib | 10 +++++
    scripts/remove-dup.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++
    5 files changed, 128 insertions(+), 2 deletions(-)

    diff --git a/Makefile b/Makefile
    index a65ffd2..1c020c7 100644
    --- a/Makefile
    +++ b/Makefile
    @@ -311,6 +311,7 @@ DEPMOD = /sbin/depmod
    KALLSYMS = scripts/kallsyms
    PERL = perl
    CHECK = sparse
    +REMOVE_DUP = scripts/remove-dup

    CHECKFLAGS := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ -Wbitwise $(CF)
    MODFLAGS = -DMODULE
    @@ -1023,6 +1024,7 @@ all: modules

    PHONY += modules
    modules: $(vmlinux-dirs) $(if $(KBUILD_BUILTIN),vmlinux)
    + @$(REMOVE_DUP) $(vmlinux-dirs:%=$(objtree)/%/modules.order) > $(objtree)/modules.order
    @echo ' Building modules, stage 2.';
    $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost

    @@ -1050,6 +1052,7 @@ _modinst_:
    rm -f $(MODLIB)/build ; \
    ln -s $(objtree) $(MODLIB)/build ; \
    fi
    + @cp -f $(objtree)/modules.order $(MODLIB)/
    $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modinst

    # This depmod is only for convenience to give the initial
    @@ -1109,7 +1112,7 @@ clean: archclean $(clean-dirs)
    @find . $(RCS_FIND_IGNORE) \
    \( -name '*.[oas]' -o -name '*.ko' -o -name '.*.cmd' \
    -o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
    - -o -name '*.symtypes' \) \
    + -o -name '*.symtypes' -o -name 'modules.order' \) \
    -type f -print | xargs rm -f

    # mrproper - Delete all generated files, including .config
    diff --git a/scripts/Makefile b/scripts/Makefile
    index 1c73c5a..1c82547 100644
    --- a/scripts/Makefile
    +++ b/scripts/Makefile
    @@ -12,6 +12,7 @@ hostprogs-$(CONFIG_LOGO) += pnmtologo
    hostprogs-$(CONFIG_VT) += conmakehash
    hostprogs-$(CONFIG_PROM_CONSOLE) += conmakehash
    hostprogs-$(CONFIG_IKCONFIG) += bin2c
    +hostprogs-$(CONFIG_MODULES) += remove-dup

    always := $(hostprogs-y) $(hostprogs-m)

    diff --git a/scripts/Makefile.build b/scripts/Makefile.build
    index de9836e..816a955 100644
    --- a/scripts/Makefile.build
    +++ b/scripts/Makefile.build
    @@ -83,10 +83,12 @@ ifneq ($(strip $(obj-y) $(obj-m) $(obj-n) $(obj-) $(lib-target)),)
    builtin-target := $(obj)/built-in.o
    endif

    +modorder-target := $(obj)/modules.order
    +
    # We keep a list of all modules in $(MODVERDIR)

    __build: $(if $(KBUILD_BUILTIN),$(builtin-target) $(lib-target) $(extra-y)) \
    - $(if $(KBUILD_MODULES),$(obj-m)) \
    + $(if $(KBUILD_MODULES),$(obj-m) $(modorder-target)) \
    $(subdir-ym) $(always)
    @:

    @@ -276,6 +278,18 @@ targets += $(builtin-target)
    endif # builtin-target

    #
    +# Rule to create modules.order file
    +#
    +$(modorder-target): $(subdir-ym) FORCE
    + @{ for m in $(modorder); do \
    + if echo $$m | grep -q '.*/modules.order'; then \
    + cat $$m; \
    + else \
    + echo kernel/$$m; \
    + fi; \
    + done } > $@
    +
    +#
    # Rule to compile a set of .o files into one .a file
    #
    ifdef lib-target
    diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
    index 3c5e88b..4563c96 100644
    --- a/scripts/Makefile.lib
    +++ b/scripts/Makefile.lib
    @@ -25,6 +25,15 @@ lib-y := $(filter-out $(obj-y), $(sort $(lib-y) $(lib-m)))
    # o if we encounter foo/ in $(obj-m), remove it from $(obj-m)
    # and add the directory to the list of dirs to descend into: $(subdir-m)

    +# make sure '/' follows subdirs
    +subdir-y := $(patsubst %//,%/, $(addsuffix, /,$subdir-y))
    +subdir-m := $(patsubst %//,%/, $(addsuffix, /,$subdir-m))
    +
    +# Determine modorder. Both -y and -m subdirs can contain modules and
    +# unfortunately we don't have information about ordering between -y
    +# and -m subdirs. Just put -y's first.
    +modorder := $(patsubst %/,%/modules.order, $(subdir-y) $(subdir-m) $(filter %/, $(obj-y)) $(obj-m:.o=.ko))
    +
    __subdir-y := $(patsubst %/,%,$(filter %/, $(obj-y)))
    subdir-y += $(__subdir-y)
    __subdir-m := $(patsubst %/,%,$(filter %/, $(obj-m)))
    @@ -64,6 +73,7 @@ real-objs-m := $(foreach m, $(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y)
    extra-y := $(addprefix $(obj)/,$(extra-y))
    always := $(addprefix $(obj)/,$(always))
    targets := $(addprefix $(obj)/,$(targets))
    +modorder := $(addprefix $(obj)/,$(modorder))
    obj-y := $(addprefix $(obj)/,$(obj-y))
    obj-m := $(addprefix $(obj)/,$(obj-m))
    lib-y := $(addprefix $(obj)/,$(lib-y))
    diff --git a/scripts/remove-dup.c b/scripts/remove-dup.c
    new file mode 100644
    index 0000000..3a7a402
    --- /dev/null
    +++ b/scripts/remove-dup.c
    @@ -0,0 +1,98 @@
    +/*
    + * remove-dup - Drop duplicate lines from unsorted input files
    + *
    + * Dec 2007 Tejun Heo <teheo@suse.de>
    + *
    + * This software is released under GPLv2.
    + */
    +
    +#include <stdio.h>
    +#include <string.h>
    +#include <stdlib.h>
    +
    +struct hash_ent {
    + struct hash_ent *next;
    + char str[];
    +};
    +
    +#define fatal(fmt, args...) do { \
    + fprintf(stderr, fmt , ##args); \
    + exit(1); \
    + } while (0)
    +
    +static inline unsigned int sdb_hash(const char *str)
    +{
    + unsigned int hash = 0;
    + int c;
    +
    + while ((c = *str++))
    + hash = c + (hash << 6) + (hash << 16) - hash;
    +
    + return hash;
    +}
    +
    +int main(int argc, char **argv)
    +{
    + unsigned int nr_entries = 0;
    + struct hash_ent **hash_tbl;
    + char line[10240];
    + int i;
    +
    + /* first pass, count lines */
    + for (i = 1; i < argc; i++) {
    + FILE *fp = fopen(argv[i], "r");
    +
    + if (!fp)
    + fatal("failed to open %s for reading\n", argv[i]);
    +
    + while (fgets(line, sizeof(line), fp))
    + nr_entries++;
    +
    + fclose(fp);
    + }
    +
    + nr_entries = nr_entries * 10 / 8;
    + hash_tbl = calloc(nr_entries, sizeof(struct hash_ent *));
    + if (!hash_tbl)
    + fatal("failed to allocate hash table for %u entries\n",
    + nr_entries);
    +
    + /* second pass, hash and print unique lines */
    + for (i = 1; i < argc; i++) {
    + FILE *fp = fopen(argv[i], "r");
    +
    + if (!fp)
    + fatal("failed to open %s for reading\n", argv[i]);
    +
    + while (fgets(line, sizeof(line), fp)) {
    + int len = strlen(line);
    + struct hash_ent **ppos, *new_ent;
    +
    + if (line[len - 1] == '\n')
    + line[--len] = '\0';
    +
    + ppos = hash_tbl + (sdb_hash(line) % nr_entries);
    + while (*ppos) {
    + if (strcmp((*ppos)->str, line) == 0)
    + break;
    + ppos = &(*ppos)->next;
    + }
    + if (*ppos)
    + continue;
    +
    + new_ent = malloc(sizeof(struct hash_ent) + len + 1);
    + if (!new_ent)
    + fatal("failed to allocate hash entry\n");
    + new_ent->next = NULL;
    + memcpy(new_ent->str, line, len + 1);
    +
    + *ppos = new_ent;
    +
    + printf("%s\n", line);
    + }
    +
    + fclose(fp);
    + }
    +
    + return 0;
    +}

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