| Message ID | 1528987172-19810-3-git-send-email-yamada.masahiro@socionext.com |
|---|---|
| State | New |
| Headers | show |
| Series | net: bpfilter: clean-up build rules | expand |
On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote: > What we want here is to embed a user-space program into the kernel. > Instead of the complex ELF magic, let's simply wrap it in the assembly > with the '.incbin' directive. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > --- > > Changes in v2: > - Rebase > > 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 e0bbe75..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; \ > - $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \ > - -B `$(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 0952257..6de3ae5 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 */ > @@ -93,7 +90,9 @@ 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" > + .global bpfilter_umh_end > +bpfilter_umh_end: for some reason it doesn't work. fork_usermode_blob() returns ENOEXEC You should be able to test it simply running 'iptables -L'. Without this patch you should see: [ 12.696937] bpfilter: Loaded bpfilter_umh pid 225 Started bpfilter where first line comes from kernel module and second from umh.
Hi Alexei, 2018-06-15 9:47 GMT+09:00 Alexei Starovoitov <alexei.starovoitov@gmail.com>: > On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote: >> What we want here is to embed a user-space program into the kernel. >> Instead of the complex ELF magic, let's simply wrap it in the assembly >> with the '.incbin' directive. >> >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> >> --- >> >> Changes in v2: >> - Rebase >> >> 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 e0bbe75..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; \ >> - $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \ >> - -B `$(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 0952257..6de3ae5 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 */ >> @@ -93,7 +90,9 @@ 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" >> + .global bpfilter_umh_end >> +bpfilter_umh_end: > > for some reason it doesn't work. > fork_usermode_blob() returns ENOEXEC > You should be able to test it simply running 'iptables -L'. > Without this patch you should see: > [ 12.696937] bpfilter: Loaded bpfilter_umh pid 225 > Started bpfilter > > where first line comes from kernel module and second from umh. Sorry for the late reply. Unfortunately, I will be busy for a while. I will come back eventually to check it out, but I cannot tell when. Somebody else sent a patch equivalent to 1/3, so it is fine. 3/3 can go independently, so it will send it as a separate patch for now. -- Best Regards Masahiro Yamada
Hi, Hmm, does this approach work if the code is not in a kernel module? I tried to use it as part of the kernel image and looks to me the bounding symbols _start and _end are not correctly relocated? -- Janne On Fri, Jun 15, 2018 at 3:48 AM Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > > On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote: > > What we want here is to embed a user-space program into the kernel. > > Instead of the complex ELF magic, let's simply wrap it in the assembly > > with the '.incbin' directive. > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > --- > > > > Changes in v2: > > - Rebase > > > > 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 e0bbe75..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; \ > > - $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \ > > - -B `$(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 0952257..6de3ae5 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 */ > > @@ -93,7 +90,9 @@ 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" > > + .global bpfilter_umh_end > > +bpfilter_umh_end: > > for some reason it doesn't work. > fork_usermode_blob() returns ENOEXEC > You should be able to test it simply running 'iptables -L'. > Without this patch you should see: > [ 12.696937] bpfilter: Loaded bpfilter_umh pid 225 > Started bpfilter > > where first line comes from kernel module and second from umh. > >
Hi, Never mind, not enough coffee for the morning. Looks good addressing wise, but something goes haywire with the copy. Some size limitation? [ 84.402647] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 [ 84.403899] RIP: 0010:__memcpy+0x12/0x20 [ 84.404441] Code: c1 e2 20 48 09 d0 48 31 c3 e9 76 ff ff ff 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 48 89 f8 48 89 d1 48 c1 e9 03 83 e2 07 <f3> 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 f3 a4 [ 84.407004] RSP: 0018:ffffc90000ac39c0 EFLAGS: 00010246 [ 84.407714] RAX: ffff888041709000 RBX: 0000000000001000 RCX: 0000000000000200 [ 84.408667] RDX: 0000000000000000 RSI: ffffffff82a7cb4d RDI: ffff888041709000 [ 84.409668] RBP: ffffc90000ac3a08 R08: ffff888041709000 R09: 0000000000000000 [ 84.410621] R10: 0000000000000000 R11: 000015fffefa3dbf R12: 0000000000001000 [ 84.411710] R13: 0000000000001000 R14: ffffc90000ac3b28 R15: 0000000000001000 [ 84.412675] FS: 00007f6cd3a35740(0000) GS:ffff88807da00000(0000) knlGS:0000000000000000 [ 84.413805] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 84.414655] CR2: ffffffff82a7cb4d CR3: 0000000031344000 CR4: 00000000000006f0 [ 84.415656] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 84.416647] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 84.417619] Call Trace: [ 84.417996] ? iov_iter_copy_from_user_atomic+0x21b/0x360 [ 84.418754] ? shmem_write_begin+0x4a/0x80 [ 84.419396] generic_perform_write+0xdd/0x1b0 [ 84.419897] __generic_file_write_iter+0x1ab/0x1d0 [ 84.420453] ? apparmor_file_alloc_security+0x4c/0x230 [ 84.421082] ? kmem_cache_alloc+0x1b5/0x1d0 [ 84.421677] generic_file_write_iter+0xb3/0x150 [ 84.422353] __vfs_write+0x145/0x1d0 [ 84.422907] vfs_write+0xae/0x1a0 [ 84.423435] kernel_write+0x55/0x70 [ 84.423996] fork_usermode_blob+0x85/0x11b .. ret = fork_usermode_blob(&test_umh_start, &test_umh_end - &test_umh_start, &um_info); Addresses indeed seem ok and the '-fpic -fpie -fPIE -static' compiled user mode blob sits in between those symbols correctly. Hummm ? -- Janne On Thu, Jan 31, 2019 at 12:48 PM Janne Karhunen <janne.karhunen@gmail.com> wrote: > > Hi, > > Hmm, does this approach work if the code is not in a kernel module? I > tried to use it as part of the kernel image and looks to me the > bounding symbols _start and _end are not correctly relocated? > > -- > Janne > > On Fri, Jun 15, 2018 at 3:48 AM Alexei Starovoitov > <alexei.starovoitov@gmail.com> wrote: > > > > On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote: > > > What we want here is to embed a user-space program into the kernel. > > > Instead of the complex ELF magic, let's simply wrap it in the assembly > > > with the '.incbin' directive. > > > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > > --- > > > > > > Changes in v2: > > > - Rebase > > > > > > 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 e0bbe75..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; \ > > > - $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \ > > > - -B `$(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 0952257..6de3ae5 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 */ > > > @@ -93,7 +90,9 @@ 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" > > > + .global bpfilter_umh_end > > > +bpfilter_umh_end: > > > > for some reason it doesn't work. > > fork_usermode_blob() returns ENOEXEC > > You should be able to test it simply running 'iptables -L'. > > Without this patch you should see: > > [ 12.696937] bpfilter: Loaded bpfilter_umh pid 225 > > Started bpfilter > > > > where first line comes from kernel module and second from umh. > > > >
Hi, Okay my bad, proper __initconst declarations would do the trick, cool stuff. -- Janne On Thu, Jan 31, 2019 at 1:09 PM Janne Karhunen <janne.karhunen@gmail.com> wrote: > > Hi, > > Never mind, not enough coffee for the morning. Looks good addressing > wise, but something goes haywire with the copy. Some size limitation? > > [ 84.402647] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), > BIOS 1.10.2-1ubuntu1 04/01/2014 > [ 84.403899] RIP: 0010:__memcpy+0x12/0x20 > [ 84.404441] Code: c1 e2 20 48 09 d0 48 31 c3 e9 76 ff ff ff 90 90 > 90 90 90 90 90 90 90 90 0f 1f 44 00 00 48 89 f8 48 89 d1 48 c1 e9 03 > 83 e2 07 <f3> 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48 89 d1 > f3 a4 > [ 84.407004] RSP: 0018:ffffc90000ac39c0 EFLAGS: 00010246 > [ 84.407714] RAX: ffff888041709000 RBX: 0000000000001000 RCX: 0000000000000200 > [ 84.408667] RDX: 0000000000000000 RSI: ffffffff82a7cb4d RDI: ffff888041709000 > [ 84.409668] RBP: ffffc90000ac3a08 R08: ffff888041709000 R09: 0000000000000000 > [ 84.410621] R10: 0000000000000000 R11: 000015fffefa3dbf R12: 0000000000001000 > [ 84.411710] R13: 0000000000001000 R14: ffffc90000ac3b28 R15: 0000000000001000 > [ 84.412675] FS: 00007f6cd3a35740(0000) GS:ffff88807da00000(0000) > knlGS:0000000000000000 > [ 84.413805] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 84.414655] CR2: ffffffff82a7cb4d CR3: 0000000031344000 CR4: 00000000000006f0 > [ 84.415656] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 84.416647] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 84.417619] Call Trace: > [ 84.417996] ? iov_iter_copy_from_user_atomic+0x21b/0x360 > [ 84.418754] ? shmem_write_begin+0x4a/0x80 > [ 84.419396] generic_perform_write+0xdd/0x1b0 > [ 84.419897] __generic_file_write_iter+0x1ab/0x1d0 > [ 84.420453] ? apparmor_file_alloc_security+0x4c/0x230 > [ 84.421082] ? kmem_cache_alloc+0x1b5/0x1d0 > [ 84.421677] generic_file_write_iter+0xb3/0x150 > [ 84.422353] __vfs_write+0x145/0x1d0 > [ 84.422907] vfs_write+0xae/0x1a0 > [ 84.423435] kernel_write+0x55/0x70 > [ 84.423996] fork_usermode_blob+0x85/0x11b > .. > > ret = fork_usermode_blob(&test_umh_start, > &test_umh_end - &test_umh_start, &um_info); > > Addresses indeed seem ok and the '-fpic -fpie -fPIE -static' compiled > user mode blob sits in between those symbols correctly. Hummm ? > > > -- > Janne > > On Thu, Jan 31, 2019 at 12:48 PM Janne Karhunen > <janne.karhunen@gmail.com> wrote: > > > > Hi, > > > > Hmm, does this approach work if the code is not in a kernel module? I > > tried to use it as part of the kernel image and looks to me the > > bounding symbols _start and _end are not correctly relocated? > > > > -- > > Janne > > > > On Fri, Jun 15, 2018 at 3:48 AM Alexei Starovoitov > > <alexei.starovoitov@gmail.com> wrote: > > > > > > On Thu, Jun 14, 2018 at 11:39:31PM +0900, Masahiro Yamada wrote: > > > > What we want here is to embed a user-space program into the kernel. > > > > Instead of the complex ELF magic, let's simply wrap it in the assembly > > > > with the '.incbin' directive. > > > > > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > > > --- > > > > > > > > Changes in v2: > > > > - Rebase > > > > > > > > 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 e0bbe75..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; \ > > > > - $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \ > > > > - -B `$(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 0952257..6de3ae5 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 */ > > > > @@ -93,7 +90,9 @@ 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" > > > > + .global bpfilter_umh_end > > > > +bpfilter_umh_end: > > > > > > for some reason it doesn't work. > > > fork_usermode_blob() returns ENOEXEC > > > You should be able to test it simply running 'iptables -L'. > > > Without this patch you should see: > > > [ 12.696937] bpfilter: Loaded bpfilter_umh pid 225 > > > Started bpfilter > > > > > > where first line comes from kernel module and second from umh. > > > > > >
diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile index e0bbe75..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; \ - $(OBJCOPY) -I binary -O `$(OBJDUMP) -f $<|grep format|cut -d' ' -f8` \ - -B `$(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 0952257..6de3ae5 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 */ @@ -93,7 +90,9 @@ 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" + .global bpfilter_umh_end +bpfilter_umh_end:
What we want here is to embed a user-space program into the kernel. Instead of the complex ELF magic, let's simply wrap it in the assembly with the '.incbin' directive. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- Changes in v2: - Rebase 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 -- 2.7.4