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Date: Tue, 9 Aug 2016 17:29:05 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Sargun Dhillon <sargun@...gun.me>
Cc: netdev@...r.kernel.org, daniel@...earbox.net
Subject: Re: [net-next v2 v2 2/2] samples/bpf: Add opensnoop example that
uses current_task_in_cgroup helper
On Tue, Aug 09, 2016 at 05:00:58PM -0700, Sargun Dhillon wrote:
> This example adds the trace_opensnoop BPF sample. This example program
> prints all activities of files being opened for all programs in the
> provided cgroupsv2 cgroup and it's descendants in the cgroupv2 hierarchy.
>
> It populate a cgroups arraymap prior to execution in userspace. This means
> that the program must be run in the same cgroups namespace as the programs
> that are being traced.
>
> Signed-off-by: Sargun Dhillon <sargun@...gun.me>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> ---
> samples/bpf/Makefile | 4 +++
> samples/bpf/bpf_helpers.h | 2 ++
> samples/bpf/trace_opensnoop_kern.c | 35 +++++++++++++++++++
> samples/bpf/trace_opensnoop_user.c | 69 ++++++++++++++++++++++++++++++++++++++
> 4 files changed, 110 insertions(+)
> create mode 100644 samples/bpf/trace_opensnoop_kern.c
> create mode 100644 samples/bpf/trace_opensnoop_user.c
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 90ebf7d..d9c37a4 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -24,6 +24,7 @@ hostprogs-y += test_overhead
> hostprogs-y += test_cgrp2_array_pin
> hostprogs-y += xdp1
> hostprogs-y += xdp2
> +hostprogs-y += trace_opensnoop
>
> test_verifier-objs := test_verifier.o libbpf.o
> test_maps-objs := test_maps.o libbpf.o
> @@ -49,6 +50,7 @@ test_cgrp2_array_pin-objs := libbpf.o test_cgrp2_array_pin.o
> xdp1-objs := bpf_load.o libbpf.o xdp1_user.o
> # reuse xdp1 source intentionally
> xdp2-objs := bpf_load.o libbpf.o xdp1_user.o
> +trace_opensnoop-objs := bpf_load.o libbpf.o trace_opensnoop_user.o
>
> # Tell kbuild to always build the programs
> always := $(hostprogs-y)
> @@ -74,6 +76,7 @@ always += parse_varlen.o parse_simple.o parse_ldabs.o
> always += test_cgrp2_tc_kern.o
> always += xdp1_kern.o
> always += xdp2_kern.o
> +always += trace_opensnoop_kern.o
>
> HOSTCFLAGS += -I$(objtree)/usr/include
>
> @@ -97,6 +100,7 @@ HOSTLOADLIBES_map_perf_test += -lelf -lrt
> HOSTLOADLIBES_test_overhead += -lelf -lrt
> HOSTLOADLIBES_xdp1 += -lelf
> HOSTLOADLIBES_xdp2 += -lelf
> +HOSTLOADLIBES_trace_opensnoop += -lelf
>
> # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
> # make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
> diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h
> index 217c8d5..d409cbb 100644
> --- a/samples/bpf/bpf_helpers.h
> +++ b/samples/bpf/bpf_helpers.h
> @@ -43,6 +43,8 @@ static int (*bpf_get_stackid)(void *ctx, void *map, int flags) =
> (void *) BPF_FUNC_get_stackid;
> static int (*bpf_probe_write_user)(void *dst, void *src, int size) =
> (void *) BPF_FUNC_probe_write_user;
> +static int (*bpf_current_task_in_cgroup)(void *map, int index) =
> + (void *) BPF_FUNC_current_task_in_cgroup;
>
> /* llvm builtin functions that eBPF C program may use to
> * emit BPF_LD_ABS and BPF_LD_IND instructions
> diff --git a/samples/bpf/trace_opensnoop_kern.c b/samples/bpf/trace_opensnoop_kern.c
> new file mode 100644
> index 0000000..dade471
> --- /dev/null
> +++ b/samples/bpf/trace_opensnoop_kern.c
> @@ -0,0 +1,35 @@
> +/* Copyright (c) 2016 Sargun Dhillon <sargun@...gun.me>
> + *
> + * 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/ptrace.h>
> +#include <uapi/linux/bpf.h>
> +#include <linux/version.h>
> +#include "bpf_helpers.h"
> +
> +struct bpf_map_def SEC("maps") cgroup_map = {
> + .type = BPF_MAP_TYPE_CGROUP_ARRAY,
> + .key_size = sizeof(u32),
> + .value_size = sizeof(u32),
> + .max_entries = 1,
> +};
> +
> +SEC("kprobe/sys_open")
> +int bpf_prog1(struct pt_regs *ctx)
> +{
> + const char *filename = (char *)PT_REGS_PARM1(ctx);
> + char fmt[] = "Opening file: %s\n";
> +
> + if (!bpf_current_task_in_cgroup(&cgroup_map, 0))
> + return 0;
> +
> + bpf_trace_printk(fmt, sizeof(fmt), filename);
> +
> + return 1;
what is the point of return 1 here?
Could you also add a bit more meat in here like real opensnoop does?
Computing sys_open time delta and capturing return code?
Then it will be a solid example and test.
> +++ b/samples/bpf/trace_opensnoop_user.c
> @@ -0,0 +1,69 @@
> +#include <stdio.h>
license banner pls.
> + ret = bpf_update_elem(map_fd[0],
> + &array_index,
> + &cg2_fd, BPF_ANY);
couldn't it be on the same line?
> + if (ret) {
> + perror("bpf_update_elem");
> + return 1;
> + }
> +
> + read_trace_pipe();
could you make it into test instead?
The examples that have to be ctrl-c are not friendly for automatic testing.
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