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

[Daniel Borkmann <daniel@iogearbox.net>]

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@google.com>

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,
> +},
>