Messages in this thread | | | From | Masahiro Yamada <> | Date | Sat, 9 Jun 2018 21:45:23 +0900 | Subject | Re: [PATCH 2/3] bpfilter: include bpfilter_umh in assembly instead of using objcopy |
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2018-06-09 5:47 GMT+09:00 Alexei Starovoitov <alexei.starovoitov@gmail.com>: > On Sat, Jun 09, 2018 at 02:12:09AM +0900, Masahiro Yamada wrote: >> Do not use the troublesome ELF magic. What is happening here is to >> embed a user-space program into the kernel. Simply wrap it in the >> assembly with the '.incbin' directive. >> >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> >> --- >> >> net/bpfilter/Makefile | 15 ++------------- >> net/bpfilter/bpfilter_kern.c | 11 +++++------ >> net/bpfilter/bpfilter_umh_blob.S | 7 +++++++ >> 3 files changed, 14 insertions(+), 19 deletions(-) >> create mode 100644 net/bpfilter/bpfilter_umh_blob.S >> >> diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile >> index aafa720..39c6980 100644 >> --- a/net/bpfilter/Makefile >> +++ b/net/bpfilter/Makefile >> @@ -15,18 +15,7 @@ ifeq ($(CONFIG_BPFILTER_UMH), y) >> HOSTLDFLAGS += -static >> endif >> >> -# a bit of elf magic to convert bpfilter_umh binary into a binary blob >> -# inside bpfilter_umh.o elf file referenced by >> -# _binary_net_bpfilter_bpfilter_umh_start symbol >> -# which bpfilter_kern.c passes further into umh blob loader at run-time >> -quiet_cmd_copy_umh = GEN $@ >> - cmd_copy_umh = echo ':' > $(obj)/.bpfilter_umh.o.cmd; \ >> - $(OBJCOPY) -I binary -O $(CONFIG_OUTPUT_FORMAT) \ >> - -B `$(OBJDUMP) -f $<|grep architecture|cut -d, -f1|cut -d' ' -f2` \ >> - --rename-section .data=.init.rodata $< $@ >> - >> -$(obj)/bpfilter_umh.o: $(obj)/bpfilter_umh >> - $(call cmd,copy_umh) >> +$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh >> >> obj-$(CONFIG_BPFILTER_UMH) += bpfilter.o >> -bpfilter-objs += bpfilter_kern.o bpfilter_umh.o >> +bpfilter-objs += bpfilter_kern.o bpfilter_umh_blob.o >> diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c >> index b13d058..fcc1a7c 100644 >> --- a/net/bpfilter/bpfilter_kern.c >> +++ b/net/bpfilter/bpfilter_kern.c >> @@ -10,11 +10,8 @@ >> #include <linux/file.h> >> #include "msgfmt.h" >> >> -#define UMH_start _binary_net_bpfilter_bpfilter_umh_start >> -#define UMH_end _binary_net_bpfilter_bpfilter_umh_end >> - >> -extern char UMH_start; >> -extern char UMH_end; >> +extern char bpfilter_umh_start; >> +extern char bpfilter_umh_end; >> >> static struct umh_info info; >> /* since ip_getsockopt() can run in parallel, serialize access to umh */ >> @@ -89,7 +86,9 @@ static int __init load_umh(void) >> int err; >> >> /* fork usermode process */ >> - err = fork_usermode_blob(&UMH_start, &UMH_end - &UMH_start, &info); >> + err = fork_usermode_blob(&bpfilter_umh_end, >> + &bpfilter_umh_end - &bpfilter_umh_start, >> + &info); >> if (err) >> return err; >> pr_info("Loaded bpfilter_umh pid %d\n", info.pid); >> diff --git a/net/bpfilter/bpfilter_umh_blob.S b/net/bpfilter/bpfilter_umh_blob.S >> new file mode 100644 >> index 0000000..40311d1 >> --- /dev/null >> +++ b/net/bpfilter/bpfilter_umh_blob.S >> @@ -0,0 +1,7 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> + .section .init.rodata, "a" >> + .global bpfilter_umh_start >> +bpfilter_umh_start: >> + .incbin "net/bpfilter/bpfilter_umh" > > Interesting. I think this is good idea. Looks cleaner than objcopy magic. > btw CONFIG_OUTPUT_FORMAT already fixed by > commit 8d97ca6b6755 ("bpfilter: fix OUTPUT_FORMAT") in net tree. > Could you please rebase on top of that tree? >
OK, I will rebase it.
BTW, I only compile-tested this patch. Could you check if it really works?
-- Best Regards Masahiro Yamada
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