This helper obtains the active namespace from current and returns pid, tgid,
device and namespace id as seen from that namespace, allowing to instrument
a process inside a container.
Device is read from /proc/self/ns/pid, as in the future it's possible that
different pid_ns files may belong to different devices, according
to the discussion between Eric Biederman and Yonghong in 2017 linux plumbers
conference.
Currently bpf_get_current_pid_tgid(), is used to do pid filtering in bcc's
scripts but this helper returns the pid as seen by the root namespace which is
fine when a bcc script is not executed inside a container.
When the process of interest is inside a container, pid filtering will not work
if bpf_get_current_pid_tgid() is used. This helper addresses this limitation
returning the pid as it's seen by the current namespace where the script is
executing.
This helper has the same use cases as bpf_get_current_pid_tgid() as it can be
used to do pid filtering even inside a container.
For example a bcc script using bpf_get_current_pid_tgid() (tools/funccount.py):
u32 pid = bpf_get_current_pid_tgid() >> 32;
if (pid != <pid_arg_passed_in>)
return 0;
Could be modified to use bpf_get_current_pidns_info() as follows:
struct bpf_pidns pidns;
bpf_get_current_pidns_info(&pidns, sizeof(struct bpf_pidns));
u32 pid = pidns.tgid;
u32 nsid = pidns.nsid;
if ((pid != <pid_arg_passed_in>) && (nsid != <nsid_arg_passed_in>))
return 0;
To find out the name PID namespace id of a process, you could use this command:
$ ps -h -o pidns -p <pid_of_interest>
Or this other command:
$ ls -Li /proc/<pid_of_interest>/ns/pid
Signed-off-by: Carlos Antonio Neira Bustos <cneirabus...@gmail.com>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 24 +++++++++++-
kernel/bpf/core.c | 1 +
kernel/bpf/helpers.c | 64 +++++++++++++++++++++++++++++++
kernel/trace/bpf_trace.c | 2 +
samples/bpf/Makefile | 3 ++
samples/bpf/trace_ns_info_user.c | 35 +++++++++++++++++
samples/bpf/trace_ns_info_user_kern.c | 45 ++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 24 +++++++++++-
tools/testing/selftests/bpf/bpf_helpers.h | 3 ++
10 files changed, 200 insertions(+), 2 deletions(-)
create mode 100644 samples/bpf/trace_ns_info_user.c
create mode 100644 samples/bpf/trace_ns_info_user_kern.c
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index cd8790d2c6ed..3f4b999f7c99 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -787,6 +787,7 @@ extern const struct bpf_func_proto bpf_get_stack_proto;
extern const struct bpf_func_proto bpf_sock_map_update_proto;
extern const struct bpf_func_proto bpf_sock_hash_update_proto;
extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;
+extern const struct bpf_func_proto bpf_get_current_pidns_info_proto;
extern const struct bpf_func_proto bpf_get_local_storage_proto;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index dd5758dc35d3..8462f9881465 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2113,6 +2113,18 @@ union bpf_attr {
* the shared data.
* Return
* Pointer to the local storage area.
+ *
+ * int bpf_get_current_pidns_info(struct bpf_pidns_info *pidns, u32
size_of_pidns)
+ * Description
+ * Copies into *pidns* pid, namespace id and tgid as seen by the
+ * current namespace and also device from /proc/self/ns/pid.
+ * *size_of_pidns* must be the size of *pidns*
+ *
+ * This helper is used when pid filtering is needed inside a
+ * container as bpf_get_current_tgid() helper returns always the
+ * pid id as seen by the root namespace.
+ * Return
+ * 0 on success -EINVAL on error.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -2196,7 +2208,8 @@ union bpf_attr {
FN(rc_keydown), \
FN(skb_cgroup_id), \
FN(get_current_cgroup_id), \
- FN(get_local_storage),
+ FN(get_local_storage), \
+ FN(get_current_pidns_info),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -2724,4 +2737,13 @@ enum bpf_task_fd_type {
BPF_FD_TYPE_URETPROBE, /* filename + offset */
};
+/* helper bpf_get_current_pidns_info will store the following
+ * data, dev will contain major/minor from /proc/self/ns/pid.
+ */
+struct bpf_pidns_info {
+ __u32 dev;
+ __u32 nsid;
+ __u32 tgid;
+ __u32 pid;
+};
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 4d09e610777f..98ce53ce2ea6 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1796,6 +1796,7 @@ const struct bpf_func_proto bpf_sock_map_update_proto
__weak;
const struct bpf_func_proto bpf_sock_hash_update_proto __weak;
const struct bpf_func_proto bpf_get_current_cgroup_id_proto __weak;
const struct bpf_func_proto bpf_get_local_storage_proto __weak;
+const struct bpf_func_proto bpf_get_current_pidns_info __weak;
const struct bpf_func_proto * __weak bpf_get_trace_printk_proto(void)
{
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 1991466b8327..d06d723b9cff 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -18,6 +18,9 @@
#include <linux/sched.h>
#include <linux/uidgid.h>
#include <linux/filter.h>
+#include <linux/pid_namespace.h>
+#include <linux/major.h>
+#include <linux/stat.h>
/* If kernel subsystem is allowing eBPF programs to call this function,
* inside its own verifier_ops->get_func_proto() callback it should return
@@ -214,3 +217,64 @@ const struct bpf_func_proto bpf_get_local_storage_proto = {
.arg2_type = ARG_ANYTHING,
};
#endif
+
+BPF_CALL_2(bpf_get_current_pidns_info, struct bpf_pidns_info *, pidns_info,
u32,
+ size)
+{
+ const char *ppath = "/proc/self/ns/pid";
+ struct pid_namespace *pidns = NULL;
+ mm_segment_t oldsegfs;
+ struct kstat stat;
+ pid_t tgid = 0;
+ pid_t pid = 0;
+ int res = 0;
+
+ if (unlikely(size != sizeof(struct bpf_pidns_info)))
+ goto clear;
+
+ pidns = task_active_pid_ns(current);
+
+ if (unlikely(!pidns))
+ goto clear;
+
+ pidns_info->nsid = pidns->ns.inum;
+ pid = task_pid_nr_ns(current, pidns);
+
+ if (unlikely(!pid))
+ goto clear;
+
+ tgid = task_tgid_nr_ns(current, pidns);
+
+ if (unlikely(!tgid))
+ goto clear;
+
+ pidns_info->tgid = (u32) tgid;
+ pidns_info->pid = (u32) pid;
+
+ oldsegfs = get_fs();
+ set_fs(KERNEL_DS);
+ res = vfs_stat((const char __user *)ppath, &stat);
+ set_fs(oldsegfs);
+
+ if (unlikely(res))
+ goto clear;
+
+ pidns_info->dev = stat.dev;
+
+ return 0;
+
+clear:
+ if (pidns_info)
+ memset((void *)pidns, 0, (size_t) size);
+
+ return -EINVAL;
+}
+
+const struct bpf_func_proto bpf_get_current_pidns_info_proto = {
+ .func = bpf_get_current_pidns_info,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_UNINIT_MEM,
+ .arg2_type = ARG_CONST_SIZE,
+};
+
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0ae6829804bc..f70be29e49ab 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -568,6 +568,8 @@ tracing_func_proto(enum bpf_func_id func_id, const struct
bpf_prog *prog)
case BPF_FUNC_get_current_cgroup_id:
return &bpf_get_current_cgroup_id_proto;
#endif
+ case BPF_FUNC_get_current_pidns_info:
+ return &bpf_get_current_pidns_info_proto;
default:
return NULL;
}
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index f88d5683d6ee..fdcde00554ce 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -53,6 +53,7 @@ hostprogs-y += xdpsock
hostprogs-y += xdp_fwd
hostprogs-y += task_fd_query
hostprogs-y += xdp_sample_pkts
+hostprogs-y += trace_ns_info
# Libbpf dependencies
LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a
@@ -109,6 +110,7 @@ xdpsock-objs := xdpsock_user.o
xdp_fwd-objs := xdp_fwd_user.o
task_fd_query-objs := bpf_load.o task_fd_query_user.o $(TRACE_HELPERS)
xdp_sample_pkts-objs := xdp_sample_pkts_user.o $(TRACE_HELPERS)
+trace_ns_info-objs := bpf_load.o trace_ns_info_user.o
# Tell kbuild to always build the programs
always := $(hostprogs-y)
@@ -166,6 +168,7 @@ always += xdpsock_kern.o
always += xdp_fwd_kern.o
always += task_fd_query_kern.o
always += xdp_sample_pkts_kern.o
+always += trace_ns_info_user_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS += -I$(srctree)/tools/lib/
diff --git a/samples/bpf/trace_ns_info_user.c b/samples/bpf/trace_ns_info_user.c
new file mode 100644
index 000000000000..e06d08db6f30
--- /dev/null
+++ b/samples/bpf/trace_ns_info_user.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2018 Carlos Neira cneirabus...@gmail.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+
+#include <stdio.h>
+#include <linux/bpf.h>
+#include <unistd.h>
+#include "bpf/libbpf.h"
+#include "bpf_load.h"
+
+/* This code was taken verbatim from tracex1_user.c, it's used
+ * to exercize bpf_get_current_pidns_info() helper call.
+ */
+int main(int ac, char **argv)
+{
+ FILE *f;
+ char filename[256];
+
+ snprintf(filename, sizeof(filename), "%s_user_kern.o", argv[0]);
+ printf("loading %s\n", filename);
+
+ if (load_bpf_file(filename)) {
+ printf("%s", bpf_log_buf);
+ return 1;
+ }
+
+ f = popen("taskset 1 ping localhost", "r");
+ (void) f;
+ read_trace_pipe();
+ return 0;
+}
diff --git a/samples/bpf/trace_ns_info_user_kern.c
b/samples/bpf/trace_ns_info_user_kern.c
new file mode 100644
index 000000000000..ceaf3e83c8e7
--- /dev/null
+++ b/samples/bpf/trace_ns_info_user_kern.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2018 Carlos Neira cneirabus...@gmail.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/version.h>
+#include <uapi/linux/bpf.h>
+#include "bpf_helpers.h"
+
+typedef __u64 u64;
+typedef __u32 u32;
+
+
+/* kprobe is NOT a stable ABI
+ * kernel functions can be removed, renamed or completely change semantics.
+ * Number of arguments and their positions can change, etc.
+ * In such case this bpf+kprobe example will no longer be meaningful
+ */
+
+/* This will call bpf_get_current_pidns_info() to display pid and ns values
+ * as seen by the current namespace, on the far left you will see the pid as
+ * seen as by the root namespace.
+ */
+
+SEC("kprobe/__netif_receive_skb_core")
+int bpf_prog1(struct pt_regs *ctx)
+{
+ char fmt[] = "nsid:%u, dev: %u, pid:%u\n";
+ struct bpf_pidns_info nsinfo;
+ int ok = 0;
+
+ ok = bpf_get_current_pidns_info(&nsinfo, sizeof(nsinfo));
+ if (ok == 0)
+ bpf_trace_printk(fmt, sizeof(fmt), (u32)nsinfo.nsid,
+ (u32) nsinfo.dev, (u32)nsinfo.pid);
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index dd5758dc35d3..8462f9881465 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2113,6 +2113,18 @@ union bpf_attr {
* the shared data.
* Return
* Pointer to the local storage area.
+ *
+ * int bpf_get_current_pidns_info(struct bpf_pidns_info *pidns, u32
size_of_pidns)
+ * Description
+ * Copies into *pidns* pid, namespace id and tgid as seen by the
+ * current namespace and also device from /proc/self/ns/pid.
+ * *size_of_pidns* must be the size of *pidns*
+ *
+ * This helper is used when pid filtering is needed inside a
+ * container as bpf_get_current_tgid() helper returns always the
+ * pid id as seen by the root namespace.
+ * Return
+ * 0 on success -EINVAL on error.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -2196,7 +2208,8 @@ union bpf_attr {
FN(rc_keydown), \
FN(skb_cgroup_id), \
FN(get_current_cgroup_id), \
- FN(get_local_storage),
+ FN(get_local_storage), \
+ FN(get_current_pidns_info),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
@@ -2724,4 +2737,13 @@ enum bpf_task_fd_type {
BPF_FD_TYPE_URETPROBE, /* filename + offset */
};
+/* helper bpf_get_current_pidns_info will store the following
+ * data, dev will contain major/minor from /proc/self/ns/pid.
+ */
+struct bpf_pidns_info {
+ __u32 dev;
+ __u32 nsid;
+ __u32 tgid;
+ __u32 pid;
+};
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/tools/testing/selftests/bpf/bpf_helpers.h
b/tools/testing/selftests/bpf/bpf_helpers.h
index cb9fcfbc9307..c3060f3284e0 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -137,6 +137,9 @@ static unsigned long long
(*bpf_get_current_cgroup_id)(void) =
(void *) BPF_FUNC_get_current_cgroup_id;
static void *(*bpf_get_local_storage)(void *map, unsigned long long flags) =
(void *) BPF_FUNC_get_local_storage;
+static int (*bpf_get_current_pidns_info)(struct bpf_pidns_info *buf,
+ unsigned int buf_size) =
+ (void *) BPF_FUNC_get_current_pidns_info;
/* llvm builtin functions that eBPF C program may use to
* emit BPF_LD_ABS and BPF_LD_IND instructions
--
2.11.0
