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Date: Fri, 3 Jun 2022 13:59:05 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Roberto Sassu <roberto.sassu@...wei.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
KP Singh <kpsingh@...nel.org>, bpf <bpf@...r.kernel.org>,
Networking <netdev@...r.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 9/9] selftests/bpf: Add map access tests
On Thu, Jun 2, 2022 at 7:39 AM Roberto Sassu <roberto.sassu@...wei.com> wrote:
>
> Add some tests to ensure that read-like operations can be performed on a
> write-protected map, and that write-like operations fail with a read file
> descriptor.
>
> Do the tests programmatically, with the new functions
> bpf_map_get_fd_by_id_flags() and bpf_obj_get_flags(), added to libbpf, and
> with the bpftool binary.
>
> Also ensure that map search by name works when there is a write-protected
> map. Before, iteration over existing maps stopped due to not being able
> to get a file descriptor with full permissions.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> ---
> .../bpf/prog_tests/test_map_check_access.c | 264 ++++++++++++++++++
> .../selftests/bpf/progs/map_check_access.c | 65 +++++
> 2 files changed, 329 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/test_map_check_access.c
> create mode 100644 tools/testing/selftests/bpf/progs/map_check_access.c
general convention (not universally followed, unfortunately) is
opposite, progs/test_<something>.c and prog_tests/<something>.c. This
allows to not have weird test_test_<something> naming pattern
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/test_map_check_access.c b/tools/testing/selftests/bpf/prog_tests/test_map_check_access.c
> new file mode 100644
> index 000000000000..20ccadcdf10f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/test_map_check_access.c
> @@ -0,0 +1,264 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
> + *
> + * Author: Roberto Sassu <roberto.sassu@...wei.com>
> + */
> +
> +#include <test_progs.h>
> +
> +#include "map_check_access.skel.h"
> +
> +#define PINNED_MAP_PATH "/sys/fs/bpf/test_map_check_access_map"
> +#define BPFTOOL_PATH "./tools/build/bpftool/bpftool"
> +
> +enum check_types { CHECK_NONE, CHECK_PINNED, CHECK_METADATA };
> +
> +static int populate_argv(char *argv[], int max_args, char *cmdline)
> +{
> + char *arg;
> + int i = 0;
> +
> + argv[i++] = BPFTOOL_PATH;
> +
> + while ((arg = strsep(&cmdline, " "))) {
> + if (i == max_args - 1)
> + break;
> +
> + argv[i++] = arg;
> + }
> +
> + argv[i] = NULL;
> + return i;
> +}
> +
> +static void restore_cmdline(char *argv[], int num_args)
> +{
> + int i;
> +
> + for (i = 1; i < num_args - 1; i++)
> + argv[i][strlen(argv[i])] = ' ';
> +}
I'm missing the point of this cmdline restoration?..
> +
> +static int _run_bpftool(char *cmdline, enum check_types check)
> +{
> + char *argv[20];
> + char output[1024];
> + int ret, fd[2], num_args, child_pid, child_status;
> +
> + num_args = populate_argv(argv, ARRAY_SIZE(argv), cmdline);
> +
> + ret = pipe(fd);
> + if (ret < 0)
> + return ret;
> +
and popen() doesn't work instead of all this forking/execve sequence?
> + child_pid = fork();
> + if (child_pid == 0) {
> + close(fd[0]);
> + close(STDOUT_FILENO);
> + close(STDERR_FILENO);
> +
> + ret = dup2(fd[1], STDOUT_FILENO);
> + if (ret < 0) {
> + close(fd[1]);
> + exit(errno);
> + }
> +
> + execv(BPFTOOL_PATH, argv);
> + close(fd[1]);
> + exit(errno);
> + } else if (child_pid > 0) {
> + close(fd[1]);
> +
> + restore_cmdline(argv, num_args);
> +
> + waitpid(child_pid, &child_status, 0);
> + if (WEXITSTATUS(child_status)) {
> + close(fd[0]);
> + return WEXITSTATUS(child_status);
> + }
> +
> + ret = read(fd[0], output, sizeof(output) - 1);
> +
> + close(fd[0]);
> +
> + if (ret < 0)
> + return ret;
> +
> + output[ret] = '\0';
> + ret = 0;
> +
> + switch (check) {
> + case CHECK_PINNED:
> + if (!strstr(output, PINNED_MAP_PATH))
> + ret = -ENOENT;
> + break;
> + case CHECK_METADATA:
> + if (!strstr(output, "test_var"))
> + ret = -ENOENT;
> + break;
> + default:
> + break;
> + }
> +
> + return ret;
> + }
> +
> + close(fd[0]);
> + close(fd[1]);
> +
> + return -EINVAL;
> +}
> +
> +void test_test_map_check_access(void)
> +{
> + struct map_check_access *skel;
> + struct bpf_map_info info_m = { 0 };
> + struct bpf_map *map;
> + __u32 len = sizeof(info_m);
> + char cmdline[1024];
> + int ret, zero = 0, fd, duration = 0;
> +
> + skel = map_check_access__open_and_load();
> + if (CHECK(!skel, "skel", "open_and_load failed\n"))
> + goto close_prog;
> +
> + ret = map_check_access__attach(skel);
> + if (CHECK(ret < 0, "skel", "attach failed\n"))
> + goto close_prog;
> +
please don't use CHECK(), use ASSERT_xxx() macros instead
> + map = bpf_object__find_map_by_name(skel->obj, "data_input");
> + if (CHECK(!map, "bpf_object__find_map_by_name", "not found\n"))
> + goto close_prog;
> +
> + ret = bpf_obj_get_info_by_fd(bpf_map__fd(map), &info_m, &len);
> + if (CHECK(ret < 0, "bpf_obj_get_info_by_fd", "error: %d\n", ret))
> + goto close_prog;
> +
> + fd = bpf_map_get_fd_by_id(info_m.id);
> + if (CHECK(fd >= 0, "bpf_map_get_fd_by_id",
> + "should fail (map write-protected)\n"))
> + goto close_prog;
> +
[...]
> + snprintf(cmdline, sizeof(cmdline), "btf dump map name data_input");
> + ret = _run_bpftool(cmdline, CHECK_NONE);
> + if (CHECK(ret, "bpftool", "%s - error: %d\n", cmdline, ret))
> + goto close_prog;
> +
> + snprintf(cmdline, sizeof(cmdline), "map pin name data_input %s",
> + PINNED_MAP_PATH);
> + ret = _run_bpftool(cmdline, CHECK_NONE);
> + if (CHECK(ret, "bpftool", "%s - error: %d\n", cmdline, ret))
> + goto close_prog;
> +
> + snprintf(cmdline, sizeof(cmdline), "struct_ops show name dummy_2");
> + ret = _run_bpftool(cmdline, CHECK_NONE);
if you don't have to restore anything, you don't need snprintf()'ing,
just pass arguments as a string literal directly
> + if (CHECK(ret, "bpftool", "%s - error: %d\n", cmdline, ret))
> + goto close_prog;
> +
> + snprintf(cmdline, sizeof(cmdline), "struct_ops dump name dummy_2");
> + ret = _run_bpftool(cmdline, CHECK_NONE);
> +
> + CHECK(ret, "_run_bpftool", "%s - error: %d\n", cmdline, ret);
> +
> +close_prog:
> + map_check_access__destroy(skel);
> + unlink(PINNED_MAP_PATH);
> +}
[...]
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