Add kernel module with user mode driver that populates bpffs with
BPF iterators.
$ mount bpffs /my/bpffs/ -t bpf
$ ls -la /my/bpffs/
total 4
drwxrwxrwt 2 root root 0 Jul 2 00:27 .
drwxr-xr-x 19 root root 4096 Jul 2 00:09 ..
-rw------- 1 root root 0 Jul 2 00:27 maps.debug
-rw------- 1 root root 0 Jul 2 00:27 progs.debug
The user mode driver will load BPF Type Formats, create BPF maps, populate BPF
maps, load two BPF programs, attach them to BPF iterators, and finally send two
bpf_link IDs back to the kernel.
The kernel will pin two bpf_links into newly mounted bpffs instance under
names "progs.debug" and "maps.debug". These two files become human readable.
$ cat /my/bpffs/progs.debug
id name attached
11 dump_bpf_map bpf_iter_bpf_map
12 dump_bpf_prog bpf_iter_bpf_prog
27 test_pkt_access
32 test_main test_pkt_access test_pkt_access
33 test_subprog1 test_pkt_access_subprog1 test_pkt_access
34 test_subprog2 test_pkt_access_subprog2 test_pkt_access
35 test_subprog3 test_pkt_access_subprog3 test_pkt_access
36 new_get_skb_len get_skb_len test_pkt_access
37 new_get_skb_ifindex get_skb_ifindex test_pkt_access
38 new_get_constant get_constant test_pkt_access
The BPF program dump_bpf_prog() in iterators.bpf.c is printing this data about
all BPF programs currently loaded in the system. This information is unstable
and will change from kernel to kernel as ".debug" suffix conveys.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200819042759.51280-4-alexei.starovoitov@gmail.com
def_bool ARCH_WANT_DEFAULT_BPF_JIT || BPF_JIT_ALWAYS_ON
depends on HAVE_EBPF_JIT && BPF_JIT
+source "kernel/bpf/preload/Kconfig"
+
config USERFAULTFD
bool "Enable userfaultfd() system call"
depends on MMU
notifier.o ksysfs.o cred.o reboot.o \
async.o range.o smpboot.o ucount.o regset.o
-obj-$(CONFIG_BPFILTER) += usermode_driver.o
+obj-$(CONFIG_USERMODE_DRIVER) += usermode_driver.o
obj-$(CONFIG_MODULES) += kmod.o
obj-$(CONFIG_MULTIUSER) += groups.o
obj-$(CONFIG_BPF_SYSCALL) += bpf_struct_ops.o
obj-${CONFIG_BPF_LSM} += bpf_lsm.o
endif
+obj-$(CONFIG_BPF_PRELOAD) += preload/
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/bpf_trace.h>
+#include "preload/bpf_preload.h"
enum bpf_type {
BPF_TYPE_UNSPEC = 0,
bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)
{
/* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future
- * extensions.
+ * extensions. That allows popoulate_bpffs() create special files.
*/
- if (strchr(dentry->d_name.name, '.'))
+ if ((dir->i_mode & S_IALLUGO) &&
+ strchr(dentry->d_name.name, '.'))
return ERR_PTR(-EPERM);
return simple_lookup(dir, dentry, flags);
.unlink = simple_unlink,
};
+/* pin iterator link into bpffs */
+static int bpf_iter_link_pin_kernel(struct dentry *parent,
+ const char *name, struct bpf_link *link)
+{
+ umode_t mode = S_IFREG | S_IRUSR;
+ struct dentry *dentry;
+ int ret;
+
+ inode_lock(parent->d_inode);
+ dentry = lookup_one_len(name, parent, strlen(name));
+ if (IS_ERR(dentry)) {
+ inode_unlock(parent->d_inode);
+ return PTR_ERR(dentry);
+ }
+ ret = bpf_mkobj_ops(dentry, mode, link, &bpf_link_iops,
+ &bpf_iter_fops);
+ dput(dentry);
+ inode_unlock(parent->d_inode);
+ return ret;
+}
+
static int bpf_obj_do_pin(const char __user *pathname, void *raw,
enum bpf_type type)
{
return 0;
}
+struct bpf_preload_ops *bpf_preload_ops;
+EXPORT_SYMBOL_GPL(bpf_preload_ops);
+
+static bool bpf_preload_mod_get(void)
+{
+ /* If bpf_preload.ko wasn't loaded earlier then load it now.
+ * When bpf_preload is built into vmlinux the module's __init
+ * function will populate it.
+ */
+ if (!bpf_preload_ops) {
+ request_module("bpf_preload");
+ if (!bpf_preload_ops)
+ return false;
+ }
+ /* And grab the reference, so the module doesn't disappear while the
+ * kernel is interacting with the kernel module and its UMD.
+ */
+ if (!try_module_get(bpf_preload_ops->owner)) {
+ pr_err("bpf_preload module get failed.\n");
+ return false;
+ }
+ return true;
+}
+
+static void bpf_preload_mod_put(void)
+{
+ if (bpf_preload_ops)
+ /* now user can "rmmod bpf_preload" if necessary */
+ module_put(bpf_preload_ops->owner);
+}
+
+static DEFINE_MUTEX(bpf_preload_lock);
+
+static int populate_bpffs(struct dentry *parent)
+{
+ struct bpf_preload_info objs[BPF_PRELOAD_LINKS] = {};
+ struct bpf_link *links[BPF_PRELOAD_LINKS] = {};
+ int err = 0, i;
+
+ /* grab the mutex to make sure the kernel interactions with bpf_preload
+ * UMD are serialized
+ */
+ mutex_lock(&bpf_preload_lock);
+
+ /* if bpf_preload.ko wasn't built into vmlinux then load it */
+ if (!bpf_preload_mod_get())
+ goto out;
+
+ if (!bpf_preload_ops->info.tgid) {
+ /* preload() will start UMD that will load BPF iterator programs */
+ err = bpf_preload_ops->preload(objs);
+ if (err)
+ goto out_put;
+ for (i = 0; i < BPF_PRELOAD_LINKS; i++) {
+ links[i] = bpf_link_by_id(objs[i].link_id);
+ if (IS_ERR(links[i])) {
+ err = PTR_ERR(links[i]);
+ goto out_put;
+ }
+ }
+ for (i = 0; i < BPF_PRELOAD_LINKS; i++) {
+ err = bpf_iter_link_pin_kernel(parent,
+ objs[i].link_name, links[i]);
+ if (err)
+ goto out_put;
+ /* do not unlink successfully pinned links even
+ * if later link fails to pin
+ */
+ links[i] = NULL;
+ }
+ /* finish() will tell UMD process to exit */
+ err = bpf_preload_ops->finish();
+ if (err)
+ goto out_put;
+ }
+out_put:
+ bpf_preload_mod_put();
+out:
+ mutex_unlock(&bpf_preload_lock);
+ for (i = 0; i < BPF_PRELOAD_LINKS && err; i++)
+ if (!IS_ERR_OR_NULL(links[i]))
+ bpf_link_put(links[i]);
+ return err;
+}
+
static int bpf_fill_super(struct super_block *sb, struct fs_context *fc)
{
static const struct tree_descr bpf_rfiles[] = { { "" } };
inode = sb->s_root->d_inode;
inode->i_op = &bpf_dir_iops;
inode->i_mode &= ~S_IALLUGO;
+ populate_bpffs(sb->s_root);
inode->i_mode |= S_ISVTX | opts->mode;
-
return 0;
}
{
int ret;
+ mutex_init(&bpf_preload_lock);
+
ret = sysfs_create_mount_point(fs_kobj, "bpf");
if (ret)
return ret;
--- /dev/null
+# SPDX-License-Identifier: GPL-2.0-only
+config USERMODE_DRIVER
+ bool
+ default n
+
+menuconfig BPF_PRELOAD
+ bool "Preload BPF file system with kernel specific program and map iterators"
+ depends on BPF
+ select USERMODE_DRIVER
+ help
+ This builds kernel module with several embedded BPF programs that are
+ pinned into BPF FS mount point as human readable files that are
+ useful in debugging and introspection of BPF programs and maps.
+
+if BPF_PRELOAD
+config BPF_PRELOAD_UMD
+ tristate "bpf_preload kernel module with user mode driver"
+ depends on CC_CAN_LINK
+ depends on m || CC_CAN_LINK_STATIC
+ default m
+ help
+ This builds bpf_preload kernel module with embedded user mode driver.
+endif
--- /dev/null
+# SPDX-License-Identifier: GPL-2.0
+
+LIBBPF_SRCS = $(srctree)/tools/lib/bpf/
+LIBBPF_A = $(obj)/libbpf.a
+LIBBPF_OUT = $(abspath $(obj))
+
+$(LIBBPF_A):
+ $(Q)$(MAKE) -C $(LIBBPF_SRCS) OUTPUT=$(LIBBPF_OUT)/ $(LIBBPF_OUT)/libbpf.a
+
+userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \
+ -I $(srctree)/tools/lib/ -Wno-unused-result
+
+userprogs := bpf_preload_umd
+
+bpf_preload_umd-objs := iterators/iterators.o
+bpf_preload_umd-userldlibs := $(LIBBPF_A) -lelf -lz
+
+$(obj)/bpf_preload_umd: $(LIBBPF_A)
+
+$(obj)/bpf_preload_umd_blob.o: $(obj)/bpf_preload_umd
+
+obj-$(CONFIG_BPF_PRELOAD_UMD) += bpf_preload.o
+bpf_preload-objs += bpf_preload_kern.o bpf_preload_umd_blob.o
--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BPF_PRELOAD_H
+#define _BPF_PRELOAD_H
+
+#include <linux/usermode_driver.h>
+#include "iterators/bpf_preload_common.h"
+
+struct bpf_preload_ops {
+ struct umd_info info;
+ int (*preload)(struct bpf_preload_info *);
+ int (*finish)(void);
+ struct module *owner;
+};
+extern struct bpf_preload_ops *bpf_preload_ops;
+#define BPF_PRELOAD_LINKS 2
+#endif
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/pid.h>
+#include <linux/fs.h>
+#include <linux/sched/signal.h>
+#include "bpf_preload.h"
+
+extern char bpf_preload_umd_start;
+extern char bpf_preload_umd_end;
+
+static int preload(struct bpf_preload_info *obj);
+static int finish(void);
+
+static struct bpf_preload_ops umd_ops = {
+ .info.driver_name = "bpf_preload",
+ .preload = preload,
+ .finish = finish,
+ .owner = THIS_MODULE,
+};
+
+static int preload(struct bpf_preload_info *obj)
+{
+ int magic = BPF_PRELOAD_START;
+ loff_t pos = 0;
+ int i, err;
+ ssize_t n;
+
+ err = fork_usermode_driver(&umd_ops.info);
+ if (err)
+ return err;
+
+ /* send the start magic to let UMD proceed with loading BPF progs */
+ n = kernel_write(umd_ops.info.pipe_to_umh,
+ &magic, sizeof(magic), &pos);
+ if (n != sizeof(magic))
+ return -EPIPE;
+
+ /* receive bpf_link IDs and names from UMD */
+ pos = 0;
+ for (i = 0; i < BPF_PRELOAD_LINKS; i++) {
+ n = kernel_read(umd_ops.info.pipe_from_umh,
+ &obj[i], sizeof(*obj), &pos);
+ if (n != sizeof(*obj))
+ return -EPIPE;
+ }
+ return 0;
+}
+
+static int finish(void)
+{
+ int magic = BPF_PRELOAD_END;
+ struct pid *tgid;
+ loff_t pos = 0;
+ ssize_t n;
+
+ /* send the last magic to UMD. It will do a normal exit. */
+ n = kernel_write(umd_ops.info.pipe_to_umh,
+ &magic, sizeof(magic), &pos);
+ if (n != sizeof(magic))
+ return -EPIPE;
+ tgid = umd_ops.info.tgid;
+ wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
+ umd_ops.info.tgid = NULL;
+ return 0;
+}
+
+static int __init load_umd(void)
+{
+ int err;
+
+ err = umd_load_blob(&umd_ops.info, &bpf_preload_umd_start,
+ &bpf_preload_umd_end - &bpf_preload_umd_start);
+ if (err)
+ return err;
+ bpf_preload_ops = &umd_ops;
+ return err;
+}
+
+static void __exit fini_umd(void)
+{
+ bpf_preload_ops = NULL;
+ /* kill UMD in case it's still there due to earlier error */
+ kill_pid(umd_ops.info.tgid, SIGKILL, 1);
+ umd_ops.info.tgid = NULL;
+ umd_unload_blob(&umd_ops.info);
+}
+late_initcall(load_umd);
+module_exit(fini_umd);
+MODULE_LICENSE("GPL");
--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 */
+ .section .init.rodata, "a"
+ .global bpf_preload_umd_start
+bpf_preload_umd_start:
+ .incbin "kernel/bpf/preload/bpf_preload_umd"
+ .global bpf_preload_umd_end
+bpf_preload_umd_end:
--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _BPF_PRELOAD_COMMON_H
+#define _BPF_PRELOAD_COMMON_H
+
+#define BPF_PRELOAD_START 0x5555
+#define BPF_PRELOAD_END 0xAAAA
+
+struct bpf_preload_info {
+ char link_name[16];
+ int link_id;
+};
+
+#endif
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include <argp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/resource.h>
+#include <bpf/libbpf.h>
+#include <bpf/bpf.h>
+#include <sys/mount.h>
+#include "iterators.skel.h"
+#include "bpf_preload_common.h"
+
+int to_kernel = -1;
+int from_kernel = 0;
+
+static int send_link_to_kernel(struct bpf_link *link, const char *link_name)
+{
+ struct bpf_preload_info obj = {};
+ struct bpf_link_info info = {};
+ __u32 info_len = sizeof(info);
+ int err;
+
+ err = bpf_obj_get_info_by_fd(bpf_link__fd(link), &info, &info_len);
+ if (err)
+ return err;
+ obj.link_id = info.id;
+ if (strlen(link_name) >= sizeof(obj.link_name))
+ return -E2BIG;
+ strcpy(obj.link_name, link_name);
+ if (write(to_kernel, &obj, sizeof(obj)) != sizeof(obj))
+ return -EPIPE;
+ return 0;
+}
+
+int main(int argc, char **argv)
+{
+ struct rlimit rlim = { RLIM_INFINITY, RLIM_INFINITY };
+ struct iterators_bpf *skel;
+ int err, magic;
+ int debug_fd;
+
+ debug_fd = open("/dev/console", O_WRONLY | O_NOCTTY | O_CLOEXEC);
+ if (debug_fd < 0)
+ return 1;
+ to_kernel = dup(1);
+ close(1);
+ dup(debug_fd);
+ /* now stdin and stderr point to /dev/console */
+
+ read(from_kernel, &magic, sizeof(magic));
+ if (magic != BPF_PRELOAD_START) {
+ printf("bad start magic %d\n", magic);
+ return 1;
+ }
+ setrlimit(RLIMIT_MEMLOCK, &rlim);
+ /* libbpf opens BPF object and loads it into the kernel */
+ skel = iterators_bpf__open_and_load();
+ if (!skel) {
+ /* iterators.skel.h is little endian.
+ * libbpf doesn't support automatic little->big conversion
+ * of BPF bytecode yet.
+ * The program load will fail in such case.
+ */
+ printf("Failed load could be due to wrong endianness\n");
+ return 1;
+ }
+ err = iterators_bpf__attach(skel);
+ if (err)
+ goto cleanup;
+
+ /* send two bpf_link IDs with names to the kernel */
+ err = send_link_to_kernel(skel->links.dump_bpf_map, "maps.debug");
+ if (err)
+ goto cleanup;
+ err = send_link_to_kernel(skel->links.dump_bpf_prog, "progs.debug");
+ if (err)
+ goto cleanup;
+
+ /* The kernel will proceed with pinnging the links in bpffs.
+ * UMD will wait on read from pipe.
+ */
+ read(from_kernel, &magic, sizeof(magic));
+ if (magic != BPF_PRELOAD_END) {
+ printf("bad final magic %d\n", magic);
+ err = -EINVAL;
+ }
+cleanup:
+ iterators_bpf__destroy(skel);
+
+ return err != 0;
+}
menuconfig BPFILTER
bool "BPF based packet filtering framework (BPFILTER)"
depends on NET && BPF && INET
+ select USERMODE_DRIVER
help
This builds experimental bpfilter framework that is aiming to
provide netfilter compatible functionality via BPF
# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
# Most of this file is copied from tools/lib/traceevent/Makefile
+RM ?= rm
+srctree = $(abs_srctree)
+
LIBBPF_VERSION := $(shell \
grep -oE '^LIBBPF_([0-9.]+)' libbpf.map | \
sort -rV | head -n1 | cut -d'_' -f2)
@ln -sf $(@F) $(OUTPUT)libbpf.so.$(LIBBPF_MAJOR_VERSION)
$(OUTPUT)libbpf.a: $(BPF_IN_STATIC)
- $(QUIET_LINK)$(RM) $@; $(AR) rcs $@ $^
+ $(QUIET_LINK)$(RM) -f $@; $(AR) rcs $@ $^
$(OUTPUT)libbpf.pc:
$(QUIET_GEN)sed -e "s|@PREFIX@|$(prefix)|" \
cscope -b -q -I $(srctree)/include -f cscope.out
tags:
- rm -f TAGS tags
+ $(RM) -f TAGS tags
ls *.c *.h | xargs $(TAGS_PROG) -a
# Declare the contents of the .PHONY variable as phony. We keep that
projects / platform / kernel / linux-rpi.git / commitdiff