Messages in this thread | | | From | Janne Karhunen <> | Date | Thu, 31 Jan 2019 14:40:07 +0200 | Subject | Re: [PATCH v2 2/3] bpfilter: include bpfilter_umh in assembly instead of using objcopy |
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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. > > > > > >
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