Re: [PATCH] bpf: Allow bpf_skb_event_output for a few prog types

From: Daniel Borkmann
Date: Tue Jun 25 2019 - 08:06:56 EST

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Hello,

On 06/25/2019 02:13 AM, allanzhang wrote:
> Software event output is only enabled by a few prog types right now (TC,
> LWT out, XDP, sockops). Many other skb based prog types need
> bpf_skb_event_output to produce software event.
>
> Added socket_filter, cg_skb, sk_skb prog types to generate sw event.
>
> Test bpf code is generated from code snippet:
>
> struct TMP {
> uint64_t tmp;
> } tt;
> tt.tmp = 5;
> bpf_perf_event_output(skb, &connection_tracking_event_map, 0,
> &tt, sizeof(tt));
> return 1;
>
> the bpf assembly from llvm is:
> 0: b7 02 00 00 05 00 00 00 r2 = 5
> 1: 7b 2a f8 ff 00 00 00 00 *(u64 *)(r10 - 8) = r2
> 2: bf a4 00 00 00 00 00 00 r4 = r10
> 3: 07 04 00 00 f8 ff ff ff r4 += -8
> 4: 18 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r2 = 0ll
> 6: b7 03 00 00 00 00 00 00 r3 = 0
> 7: b7 05 00 00 08 00 00 00 r5 = 8
> 8: 85 00 00 00 19 00 00 00 call 25
> 9: b7 00 00 00 01 00 00 00 r0 = 1
> 10: 95 00 00 00 00 00 00 00 exit
>
> Patch 1 is enabling code.
> Patch 2 is fullly covered selftest code.
>
> Signed-off-by: allanzhang <allanzhang@xxxxxxxxxx>

Thanks for the contribution! I'm a bit confused given the many submissions,
some are versioned in the subject (which is the correct way), but this patch
here was sent after v3 (?) but without a version. Which is the right one to
consider for review, I presume v3?

> ---
> tools/testing/selftests/bpf/test_verifier.c | 38 +++++++-
> .../selftests/bpf/verifier/event_output.c | 94 +++++++++++++++++++
> 2 files changed, 130 insertions(+), 2 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/verifier/event_output.c
>
> diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> index c5514daf8865..45ce9dd4323f 100644
> --- a/tools/testing/selftests/bpf/test_verifier.c
> +++ b/tools/testing/selftests/bpf/test_verifier.c
> @@ -1,10 +1,13 @@
> -// SPDX-License-Identifier: GPL-2.0-only
> /*
> * Testsuite for eBPF verifier
> *
> * Copyright (c) 2014 PLUMgrid, http://plumgrid.com
> * Copyright (c) 2017 Facebook
> * Copyright (c) 2018 Covalent IO, Inc. http://covalent.io
> + *
> + * 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.

This removal of SPDX probably slipped in as well here ..

> */
>
> #include <endian.h>
> @@ -50,7 +53,7 @@
> #define MAX_INSNS BPF_MAXINSNS
> #define MAX_TEST_INSNS 1000000
> #define MAX_FIXUPS 8
> -#define MAX_NR_MAPS 18
> +#define MAX_NR_MAPS 19
> #define MAX_TEST_RUNS 8
> #define POINTER_VALUE 0xcafe4all
> #define TEST_DATA_LEN 64
> @@ -84,6 +87,7 @@ struct bpf_test {
> int fixup_map_array_wo[MAX_FIXUPS];
> int fixup_map_array_small[MAX_FIXUPS];
> int fixup_sk_storage_map[MAX_FIXUPS];
> + int fixup_map_event_output[MAX_FIXUPS];
> const char *errstr;
> const char *errstr_unpriv;
> uint32_t retval, retval_unpriv, insn_processed;
> @@ -604,6 +608,28 @@ static int create_sk_storage_map(void)
> return fd;
> }
>
> +static int create_event_output_map(void)
> +{
> + struct bpf_create_map_attr attr = {
> + .name = "test_map",
> + .map_type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
> + .key_size = 4,
> + .value_size = 4,
> + .max_entries = 1,
> + };
> + int fd, btf_fd;
> +
> + btf_fd = load_btf();
> + if (btf_fd < 0)
> + return -1;
> + attr.btf_fd = btf_fd;
> + fd = bpf_create_map_xattr(&attr);
> + close(attr.btf_fd);
> + if (fd < 0)
> + printf("Failed to create event_output\n");
> + return fd;
> +}
> +
> static char bpf_vlog[UINT_MAX >> 8];
>
> static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
> @@ -627,6 +653,7 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
> int *fixup_map_array_wo = test->fixup_map_array_wo;
> int *fixup_map_array_small = test->fixup_map_array_small;
> int *fixup_sk_storage_map = test->fixup_sk_storage_map;
> + int *fixup_map_event_output = test->fixup_map_event_output;
>
> if (test->fill_helper) {
> test->fill_insns = calloc(MAX_TEST_INSNS, sizeof(struct bpf_insn));
> @@ -788,6 +815,13 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
> fixup_sk_storage_map++;
> } while (*fixup_sk_storage_map);
> }
> + if (*fixup_map_event_output) {
> + map_fds[18] = create_event_output_map();
> + do {
> + prog[*fixup_map_event_output].imm = map_fds[18];
> + fixup_map_event_output++;
> + } while (*fixup_map_event_output);
> + }
> }
>
> static int set_admin(bool admin)
> diff --git a/tools/testing/selftests/bpf/verifier/event_output.c b/tools/testing/selftests/bpf/verifier/event_output.c
> new file mode 100644
> index 000000000000..b25eabcfaa56
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/verifier/event_output.c
> @@ -0,0 +1,94 @@
> +/* instructions used to output a skb based software event, produced
> + * from code snippet:
> +struct TMP {
> + uint64_t tmp;
> +} tt;
> +tt.tmp = 5;
> +bpf_perf_event_output(skb, &connection_tracking_event_map, 0,
> + &tt, sizeof(tt));
> +return 1;
> +
> +the bpf assembly from llvm is:
> + 0: b7 02 00 00 05 00 00 00 r2 = 5
> + 1: 7b 2a f8 ff 00 00 00 00 *(u64 *)(r10 - 8) = r2
> + 2: bf a4 00 00 00 00 00 00 r4 = r10
> + 3: 07 04 00 00 f8 ff ff ff r4 += -8
> + 4: 18 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r2 = 0ll
> + 6: b7 03 00 00 00 00 00 00 r3 = 0
> + 7: b7 05 00 00 08 00 00 00 r5 = 8
> + 8: 85 00 00 00 19 00 00 00 call 25
> + 9: b7 00 00 00 01 00 00 00 r0 = 1
> + 10: 95 00 00 00 00 00 00 00 exit
> +
> + The reason I put the code here instead of fill_helpers is that map fixup is
> + against the insns, instead of filled prog.
> +*/
> +
> +#define __PERF_EVENT_INSNS__ \
> + BPF_MOV64_IMM(BPF_REG_2, 5), \
> + BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -8), \
> + BPF_MOV64_REG(BPF_REG_4, BPF_REG_10), \
> + BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, -8), \
> + BPF_LD_MAP_FD(BPF_REG_2, 0), \
> + BPF_MOV64_IMM(BPF_REG_3, 0), \
> + BPF_MOV64_IMM(BPF_REG_5, 8), \
> + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, \
> + BPF_FUNC_perf_event_output), \
> + BPF_MOV64_IMM(BPF_REG_0, 1), \
> + BPF_EXIT_INSN(),
> +{
> + "perfevent for sockops",
> + .insns = { __PERF_EVENT_INSNS__ },
> + .prog_type = BPF_PROG_TYPE_SOCK_OPS,
> + .fixup_map_event_output = { 4 },
> + .result = ACCEPT,
> + .retval = 1,
> +},
> +{
> + "perfevent for tc",
> + .insns = { __PERF_EVENT_INSNS__ },
> + .prog_type = BPF_PROG_TYPE_SCHED_CLS,
> + .fixup_map_event_output = { 4 },
> + .result = ACCEPT,
> + .retval = 1,
> +},
> +{
> + "perfevent for lwt out",
> + .insns = { __PERF_EVENT_INSNS__ },
> + .prog_type = BPF_PROG_TYPE_LWT_OUT,
> + .fixup_map_event_output = { 4 },
> + .result = ACCEPT,
> + .retval = 1,
> +},
> +{
> + "perfevent for xdp",
> + .insns = { __PERF_EVENT_INSNS__ },
> + .prog_type = BPF_PROG_TYPE_XDP,
> + .fixup_map_event_output = { 4 },
> + .result = ACCEPT,
> + .retval = 1,
> +},
> +{
> + "perfevent for socket filter",
> + .insns = { __PERF_EVENT_INSNS__ },
> + .prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
> + .fixup_map_event_output = { 4 },
> + .result = ACCEPT,
> + .retval = 1,
> +},
> +{
> + "perfevent for sk_skb",
> + .insns = { __PERF_EVENT_INSNS__ },
> + .prog_type = BPF_PROG_TYPE_SK_SKB,
> + .fixup_map_event_output = { 4 },
> + .result = ACCEPT,
> + .retval = 1,
> +},
> +{
> + "perfevent for cgroup skb",
> + .insns = { __PERF_EVENT_INSNS__ },
> + .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
> + .fixup_map_event_output = { 4 },
> + .result = ACCEPT,
> + .retval = 1,
> +},
>

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