compat-includes/compat.h can usually be used to solve compatibility problems with older kernels. This works well for functions, defines/enums and sometimes even structures that were introduced.
But this can fail when structs changed. Some of these can be solved in crude ways but sometimes it is unavoidable to have a version specific code. Unfortunately, this kind of code is not acceptable in the kernel and thus the compat infrastructure of the external module has to do add it automatically before the source is compiled.
This process works by creating a build directory which is prefilled with the source from net/batman-adv/. The patches from compat-patches/ will be applied on top of this copy and then the code is compiled.
Signed-off-by: Sven Eckelmann sven@narfation.org --- v2: - Rebased on top of current next
.gitignore | 10 ++++------ Makefile | 31 +++++++++++++++++++++++++++---- compat-patches/README | 23 +++++++++++++++++++++++ compat-sources/Makefile | 6 +++--- 4 files changed, 57 insertions(+), 13 deletions(-) create mode 100644 compat-patches/README
diff --git a/.gitignore b/.gitignore index 4c03561..15a99aa 100644 --- a/.gitignore +++ b/.gitignore @@ -1,10 +1,8 @@ +/build/ /compat-autoconf.h /compat-autoconf.h.tmp /compat-sources/**/.* /compat-sources/**/*.o -/net/batman-adv/.* -/net/batman-adv/batman-adv.ko -/net/batman-adv/batman-adv.mod.c -/net/batman-adv/modules.order -/net/batman-adv/Module.symvers -/net/batman-adv/*.o +/modules.order +/Module.symvers +/.tmp_versions diff --git a/Makefile b/Makefile index d42bb56..b105290 100644 --- a/Makefile +++ b/Makefile @@ -33,6 +33,7 @@ export CONFIG_BATMAN_ADV_MCAST=y export CONFIG_BATMAN_ADV_BATMAN_V=n
PWD:=$(shell pwd) +BUILD_DIR=$(PWD)/build KERNELPATH ?= /lib/modules/$(shell uname -r)/build # sanity check: does KERNELPATH exist? ifeq ($(shell cd $(KERNELPATH) && pwd),) @@ -41,6 +42,14 @@ endif
export KERNELPATH RM ?= rm -f +MKDIR := mkdir -p +PATCH_FLAGS = --batch --fuzz=0 --forward --strip=1 --unified --version-control=never -g0 --remove-empty-files --no-backup-if-mismatch --reject-file=- +PATCH := patch $(PATCH_FLAGS) -i +CP := cp -fpR + +SOURCE = $(wildcard net/batman-adv/*.[ch]) net/batman-adv/Makefile +SOURCE_BUILD = $(wildcard $(BUILD_DIR)/net/batman-adv/*.[ch]) $(BUILD_DIR)/net/batman-adv/Makefile +SOURCE_STAMP = $(BUILD_DIR)/net/batman-adv/.compat-prepared
REVISION= $(shell if [ -d "$(PWD)/.git" ]; then \ echo $$(git --git-dir="$(PWD)/.git" describe --always --dirty --match "v*" |sed 's/^v//' 2> /dev/null || echo "[unknown]"); \ @@ -57,7 +66,7 @@ endif
include $(PWD)/compat-sources/Makefile
-obj-y += net/batman-adv/ +obj-y += build/net/batman-adv/
export batman-adv-y
@@ -76,18 +85,32 @@ BUILD_FLAGS := \ CONFIG_BATMAN_ADV_BATMAN_V=$(CONFIG_BATMAN_ADV_BATMAN_V) \ INSTALL_MOD_DIR=updates/
-all: config +all: config $(SOURCE_STAMP) $(MAKE) -C $(KERNELPATH) $(BUILD_FLAGS) modules
clean: $(RM) compat-autoconf.h* - $(MAKE) -C $(KERNELPATH) $(BUILD_FLAGS) clean + $(RM) -r $(BUILD_DIR)
-install: config +install: config $(SOURCE_STAMP) $(MAKE) -C $(KERNELPATH) $(BUILD_FLAGS) modules_install depmod -a
config: $(PWD)/gen-compat-autoconf.sh $(PWD)/compat-autoconf.h
+$(SOURCE_STAMP): $(SOURCE) compat-patches/* + $(MKDIR) $(BUILD_DIR)/net/batman-adv/ + @$(RM) $(SOURCE_BUILD) + @$(CP) $(SOURCE) $(BUILD_DIR)/net/batman-adv/ + @set -e; \ + patches="$$(ls -1 compat-patches/|grep '.patch$$'|sort)"; \ + for i in $${patches}; do \ + echo ' COMPAT_PATCH '$${i};\ + cd $(BUILD_DIR); \ + $(PATCH) ../compat-patches/$${i}; \ + cd - > /dev/null; \ + done + touch $(SOURCE_STAMP) + .PHONY: all clean install config diff --git a/compat-patches/README b/compat-patches/README new file mode 100644 index 0000000..3bbddb3 --- /dev/null +++ b/compat-patches/README @@ -0,0 +1,23 @@ +WARNING +======= + +Please avoid using the compat-patches/ to implement support for old kernels. +This should be the last resort. + + * it is nearly always possible to use compat-includes/ to do the same with a + lot less problems + + * maintaining these patches is *censored* + +GENERATING A PATCH +================== + +If it not possible to avoid a patch then please make the patch as small as +possible. Even refactor the code which has to be patched to reduce the +size/number of the changes. + +Please use git-format-patches to generate them and order same inside via the +XXXX- prefix of the patch name. + + git format-patch --abbrev=7 -U3 --diff-algorithm=histogram --no-signature \ + --format=format:'From: %an <%ae>%nDate: %aD%nSubject: [PATCH] %B' -1 diff --git a/compat-sources/Makefile b/compat-sources/Makefile index a45c202..c8bae49 100644 --- a/compat-sources/Makefile +++ b/compat-sources/Makefile @@ -1,3 +1,3 @@ -batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += ../../compat-sources/net/core/skbuff.o -batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += ../../compat-sources/net/ipv4/igmp.o -batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += ../../compat-sources/net/ipv6/mcast_snoop.o +batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += ../../../compat-sources/net/core/skbuff.o +batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += ../../../compat-sources/net/ipv4/igmp.o +batman-adv-$(CONFIG_BATMAN_ADV_MCAST) += ../../../compat-sources/net/ipv6/mcast_snoop.o
Unified diff base patches have the problem that they fix only a single line and depend on the surrounding. This approach can fail relative often when the surrounding code will be changed often. Thus semantic patches (like spatch from coccinelle) or simple find+replace scripts are better for this approach.
Introduce a simple script file which will store these kind of find+replace instructions.
Signed-off-by: Sven Eckelmann sven@narfation.org --- v2: - introduce this patch to support the patch 3
Makefile | 3 ++- compat-patches/replacements.sh | 3 +++ 2 files changed, 5 insertions(+), 1 deletion(-) create mode 100755 compat-patches/replacements.sh
diff --git a/Makefile b/Makefile index b105290..7ef2569 100644 --- a/Makefile +++ b/Makefile @@ -99,7 +99,7 @@ install: config $(SOURCE_STAMP) config: $(PWD)/gen-compat-autoconf.sh $(PWD)/compat-autoconf.h
-$(SOURCE_STAMP): $(SOURCE) compat-patches/* +$(SOURCE_STAMP): $(SOURCE) compat-patches/* compat-patches/replacements.sh $(MKDIR) $(BUILD_DIR)/net/batman-adv/ @$(RM) $(SOURCE_BUILD) @$(CP) $(SOURCE) $(BUILD_DIR)/net/batman-adv/ @@ -111,6 +111,7 @@ $(SOURCE_STAMP): $(SOURCE) compat-patches/* $(PATCH) ../compat-patches/$${i}; \ cd - > /dev/null; \ done + compat-patches/replacements.sh touch $(SOURCE_STAMP)
.PHONY: all clean install config diff --git a/compat-patches/replacements.sh b/compat-patches/replacements.sh new file mode 100755 index 0000000..c7875c0 --- /dev/null +++ b/compat-patches/replacements.sh @@ -0,0 +1,3 @@ +#! /bin/sh + +set -e
On Donnerstag, 15. September 2016 15:52:48 CEST Sven Eckelmann wrote:
Unified diff base patches have the problem that they fix only a single line and depend on the surrounding. This approach can fail relative often when the surrounding code will be changed often. Thus semantic patches (like spatch from coccinelle) or simple find+replace scripts are better for this approach.
Introduce a simple script file which will store these kind of find+replace instructions.
Signed-off-by: Sven Eckelmann sven@narfation.org
We could also skip this step and directly use coccinelle. I started a branch some examples to cleanup our compat hacks [1]. The change for the netlink const change is also already available [2].
Kind regards, Sven
[1] https://git.open-mesh.org/batman-adv.git/shortlog/refs/heads/ecsv/buildpatch [2] https://git.open-mesh.org/batman-adv.git/commitdiff/2895226999760f2f2b34b506...
From: stephen hemminger stephen@networkplumber.org
Signed-off-by: Stephen Hemminger stephen@networkplumber.org [sven@narfation.org: Add compat-patch script] Signed-off-by: Sven Eckelmann sven@narfation.org --- v2: - new patch picked from the net-next.git
compat-patches/replacements.sh | 6 ++++++ net/batman-adv/netlink.c | 4 ++-- 2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/compat-patches/replacements.sh b/compat-patches/replacements.sh index c7875c0..974aa96 100755 --- a/compat-patches/replacements.sh +++ b/compat-patches/replacements.sh @@ -1,3 +1,9 @@ #! /bin/sh
set -e + +# for kernel < 3.13 to make netlink compat code work +sed -i \ + -e 's/^static const struct genl_multicast_group batadv_netlink_mcgrps/static struct genl_multicast_group batadv_netlink_mcgrps/' \ + -e 's/^static const struct nla_policy batadv_netlink_policy/static const struct nla_policy batadv_netlink_policy/' \ + build/net/batman-adv/netlink.c diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c index 18831e7..64cb6ac 100644 --- a/net/batman-adv/netlink.c +++ b/net/batman-adv/netlink.c @@ -62,11 +62,11 @@ enum batadv_netlink_multicast_groups { BATADV_NL_MCGRP_TPMETER, };
-static struct genl_multicast_group batadv_netlink_mcgrps[] = { +static const struct genl_multicast_group batadv_netlink_mcgrps[] = { [BATADV_NL_MCGRP_TPMETER] = { .name = BATADV_NL_MCAST_GROUP_TPMETER }, };
-static struct nla_policy batadv_netlink_policy[NUM_BATADV_ATTR] = { +static const struct nla_policy batadv_netlink_policy[NUM_BATADV_ATTR] = { [BATADV_ATTR_VERSION] = { .type = NLA_STRING }, [BATADV_ATTR_ALGO_NAME] = { .type = NLA_STRING }, [BATADV_ATTR_MESH_IFINDEX] = { .type = NLA_U32 },
On Thu, Sep 15, 2016 at 03:52:49PM +0200, Sven Eckelmann wrote:
+sed -i \
- -e 's/^static const struct genl_multicast_group batadv_netlink_mcgrps/static struct genl_multicast_group batadv_netlink_mcgrps/' \
- -e 's/^static const struct nla_policy batadv_netlink_policy/static const struct nla_policy batadv_netlink_policy/' \
For the second thing: Replacing the string with itself?
Just wondering... I simply tried casting the const away and that seems to compile without a warning:
----- static inline int batadv_genl_register_family_with_ops_grps(struct genl_family *family, struct genl_ops *ops, size_t n_ops, - struct genl_multicast_group *mcgrps, + const struct genl_multicast_group *mcgrps, size_t n_mcgrps) { family->ops = ops; family->n_ops = n_ops; - family->mcgrps = mcgrps; + family->mcgrps = (struct genl_multicast_group *)mcgrps; family->n_mcgrps = n_mcgrps; family->module = THIS_MODULE; -----
Or does this lead to some dangerous behaviour on the compiler side?
On Sonntag, 9. Oktober 2016 04:07:10 CEST Linus Lüssing wrote:
On Thu, Sep 15, 2016 at 03:52:49PM +0200, Sven Eckelmann wrote:
+sed -i \
- -e 's/^static const struct genl_multicast_group batadv_netlink_mcgrps/static struct genl_multicast_group batadv_netlink_mcgrps/' \
- -e 's/^static const struct nla_policy batadv_netlink_policy/static const struct nla_policy batadv_netlink_policy/' \
For the second thing: Replacing the string with itself?
Damn, you are right. This line can be removed anyway. So it is not "a big problem" but ugly as hell :)
Just wondering... I simply tried casting the const away and that seems to compile without a warning:
[...]
Or does this lead to some dangerous behaviour on the compiler side?
Yes, this will crash because it is const aka read-only and the compat code cannot write to the struct (actually, the read-only page).
Kind regards, Sven
b.a.t.m.a.n@lists.open-mesh.org
-
Linus Lüssing -
Sven Eckelmann