Date:   Thu, 13 Dec 2018 12:19:15 +0000
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        Quentin Monnet <quentin.monnet@...ronome.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Stanislav Fomichev <sdf@...gle.com>
Subject: [PATCH bpf-next 1/8] tools: bpftool: add basic probe capability, probe syscall and kversion

Add a new component and command for bpftool, in order to probe the
system to dump a set of eBPF-related parameters so that users can know
what features are available on the system.

Parameters are dumped in plain or JSON output (with -j/-p options).
Additionally, a specific keyword can be used to provide a third possible
output so that the parameters are dumped as #define-d macros, ready to
be saved to a header file and included in an eBPF-based project.

The current patch introduces probing of two simple parameters:
availability of the bpf() system call, and kernel version. Later commits
will add other probes.

Sample output:

    # bpftool feature probe kernel
    Scanning system call and kernel version...
    Kernel release is 4.19.0
    bpf() syscall is available

    # bpftool --json --pretty feature probe kernel
    {
        "syscall_config": {
            "kernel_version_code": 267008,
            "have_bpf_syscall": true
        }
    }

    # bpftool feature probe kernel macros prefix BPFTOOL_
    /*** System call and kernel version ***/
    #define BPFTOOL_LINUX_VERSION_CODE 267008
    #define BPFTOOL_BPF_SYSCALL

The optional "kernel" keyword enforces probing of the current system,
which is the only possible behaviour at this stage. It can be safely
omitted.

The feature comes with the relevant man page, but bash completion will
come in a dedicated commit.

Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
---
 .../bpftool/Documentation/bpftool-cgroup.rst  |   1 +
 .../bpftool/Documentation/bpftool-feature.rst |  69 +++++++
 .../bpf/bpftool/Documentation/bpftool-map.rst |   1 +
 .../bpf/bpftool/Documentation/bpftool-net.rst |   1 +
 .../bpftool/Documentation/bpftool-perf.rst    |   1 +
 .../bpftool/Documentation/bpftool-prog.rst    |   1 +
 tools/bpf/bpftool/Documentation/bpftool.rst   |   1 +
 tools/bpf/bpftool/feature.c                   | 184 ++++++++++++++++++
 tools/bpf/bpftool/main.c                      |   3 +-
 tools/bpf/bpftool/main.h                      |   1 +
 10 files changed, 262 insertions(+), 1 deletion(-)
 create mode 100644 tools/bpf/bpftool/Documentation/bpftool-feature.rst
 create mode 100644 tools/bpf/bpftool/feature.c

diff --git a/tools/bpf/bpftool/Documentation/bpftool-cgroup.rst b/tools/bpf/bpftool/Documentation/bpftool-cgroup.rst
index d07ccf8a23f7..d43fce568ef7 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-cgroup.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-cgroup.rst
@@ -142,5 +142,6 @@ SEE ALSO
 	**bpftool**\ (8),
 	**bpftool-prog**\ (8),
 	**bpftool-map**\ (8),
+	**bpftool-feature**\ (8),
 	**bpftool-net**\ (8),
 	**bpftool-perf**\ (8)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-feature.rst b/tools/bpf/bpftool/Documentation/bpftool-feature.rst
new file mode 100644
index 000000000000..23920a7490e9
--- /dev/null
+++ b/tools/bpf/bpftool/Documentation/bpftool-feature.rst
@@ -0,0 +1,69 @@
+===============
+bpftool-feature
+===============
+-------------------------------------------------------------------------------
+tool for inspection of eBPF-related parameters for Linux kernel or net device
+-------------------------------------------------------------------------------
+
+:Manual section: 8
+
+SYNOPSIS
+========
+
+	**bpftool** [*OPTIONS*] **feature** *COMMAND*
+
+	*OPTIONS* := { { **-j** | **--json** } [{ **-p** | **--pretty** }] }
+
+	*COMMANDS* := { **probe** | **help** }
+
+MAP COMMANDS
+=============
+
+|	**bpftool** **feature probe** [**kernel**] [**macros** [**prefix** *PREFIX*]]
+|	**bpftool** **feature help**
+
+DESCRIPTION
+===========
+	**bpftool feature probe** [**kernel**] [**macros** [**prefix** *PREFIX*]]
+		  Probe the running kernel and dump a number of eBPF-related
+		  parameters, such as availability of the **bpf()** system call.
+
+		  Keyword **kernel** can be omitted.
+
+		  If the **macros** keyword (but not the **-j** option) is
+		  passed, output is dumped as a list of **#define** macros that
+		  are ready to be included in a C header file, for example.
+		  If, additionally, **prefix** is used to define a *PREFIX*,
+		  the provided string will be used as a prefix to the names of
+		  the macros: this can be used to avoid conflicts on macro
+		  names when including the output of this command as a header
+		  file.
+
+	**bpftool feature help**
+		  Print short help message.
+
+OPTIONS
+=======
+	-h, --help
+		  Print short generic help message (similar to **bpftool help**).
+
+	-v, --version
+		  Print version number (similar to **bpftool version**).
+
+	-j, --json
+		  Generate JSON output. For commands that cannot produce JSON, this
+		  option has no effect.
+
+	-p, --pretty
+		  Generate human-readable JSON output. Implies **-j**.
+
+SEE ALSO
+========
+	**bpf**\ (2),
+	**bpf-helpers**\ (7),
+	**bpftool**\ (8),
+	**bpftool-prog**\ (8),
+	**bpftool-map**\ (8),
+	**bpftool-cgroup**\ (8),
+	**bpftool-net**\ (8),
+	**bpftool-perf**\ (8)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index 5318dcb2085e..b432c5cc20c8 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -177,5 +177,6 @@ SEE ALSO
 	**bpftool**\ (8),
 	**bpftool-prog**\ (8),
 	**bpftool-cgroup**\ (8),
+	**bpftool-feature**\ (8),
 	**bpftool-net**\ (8),
 	**bpftool-perf**\ (8)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-net.rst b/tools/bpf/bpftool/Documentation/bpftool-net.rst
index ed87c9b619ad..779dab3650ee 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-net.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-net.rst
@@ -142,4 +142,5 @@ SEE ALSO
 	**bpftool-prog**\ (8),
 	**bpftool-map**\ (8),
 	**bpftool-cgroup**\ (8),
+	**bpftool-feature**\ (8),
 	**bpftool-perf**\ (8)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-perf.rst b/tools/bpf/bpftool/Documentation/bpftool-perf.rst
index f4c5e5538bb8..bca5590a80d0 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-perf.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-perf.rst
@@ -84,4 +84,5 @@ SEE ALSO
 	**bpftool-prog**\ (8),
 	**bpftool-map**\ (8),
 	**bpftool-cgroup**\ (8),
+	**bpftool-feature**\ (8),
 	**bpftool-net**\ (8)
diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
index bb1aeb98b6da..595b4538c0d7 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
@@ -243,5 +243,6 @@ SEE ALSO
 	**bpftool**\ (8),
 	**bpftool-map**\ (8),
 	**bpftool-cgroup**\ (8),
+	**bpftool-feature**\ (8),
 	**bpftool-net**\ (8),
 	**bpftool-perf**\ (8)
diff --git a/tools/bpf/bpftool/Documentation/bpftool.rst b/tools/bpf/bpftool/Documentation/bpftool.rst
index 129b7a9c0f9b..f6526b657677 100644
--- a/tools/bpf/bpftool/Documentation/bpftool.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool.rst
@@ -68,5 +68,6 @@ SEE ALSO
 	**bpftool-prog**\ (8),
 	**bpftool-map**\ (8),
 	**bpftool-cgroup**\ (8),
+	**bpftool-feature**\ (8),
 	**bpftool-net**\ (8),
 	**bpftool-perf**\ (8)
diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c
new file mode 100644
index 000000000000..e1784611575d
--- /dev/null
+++ b/tools/bpf/bpftool/feature.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/* Copyright (c) 2018 Netronome Systems, Inc. */
+
+#include <errno.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/utsname.h>
+
+#include <linux/filter.h>
+#include <linux/limits.h>
+
+#include <bpf.h>
+
+#include "main.h"
+
+enum probe_component {
+	COMPONENT_UNSPEC,
+	COMPONENT_KERNEL,
+};
+
+/* Printing utility functions */
+
+static void
+print_bool_feature(const char *feat_name, const char *define_name,
+		   const char *plain_name, bool res, const char *define_prefix)
+{
+	if (json_output)
+		jsonw_bool_field(json_wtr, feat_name, res);
+	else if (define_prefix)
+		printf("#define %s%s%s\n", define_prefix,
+		       res ? "" : "NO_", define_name);
+	else
+		printf("%s is %savailable\n", plain_name, res ? "" : "NOT ");
+}
+
+static void
+print_start_section(const char *json_title, const char *define_comment,
+		    const char *plain_title, const char *define_prefix)
+{
+	if (json_output) {
+		jsonw_name(json_wtr, json_title);
+		jsonw_start_object(json_wtr);
+	} else if (define_prefix) {
+		printf("%s\n", define_comment);
+	} else {
+		printf("%s\n", plain_title);
+	}
+}
+
+/* Probing functions */
+
+static int probe_kernel_version(const char *define_prefix)
+{
+	int version, subversion, patchlevel, code = 0;
+	struct utsname utsn;
+
+	if (!uname(&utsn))
+		if (sscanf(utsn.release, "%d.%d.%d",
+			   &version, &subversion, &patchlevel) == 3)
+			code = (version << 16) + (subversion << 8) + patchlevel;
+
+	if (json_output)
+		jsonw_uint_field(json_wtr, "kernel_version_code", code);
+	else if (define_prefix)
+		printf("#define %sLINUX_VERSION_CODE %d\n",
+		       define_prefix, code);
+	else if (code)
+		printf("Kernel release is %d.%d.%d\n",
+		       version, subversion, patchlevel);
+	else
+		printf("Unable to parse kernel release number\n");
+
+	return code;
+}
+
+static bool probe_bpf_syscall(const char *define_prefix)
+{
+	bool res;
+
+	bpf_load_program(BPF_PROG_TYPE_UNSPEC, NULL, 0, NULL, 0, NULL, 0);
+	res = (errno != ENOSYS);
+
+	print_bool_feature("have_bpf_syscall",
+			   "BPF_SYSCALL",
+			   "bpf() syscall",
+			   res, define_prefix);
+
+	return res;
+}
+
+static int do_probe(int argc, char **argv)
+{
+	enum probe_component target = COMPONENT_UNSPEC;
+	const char *define_prefix = NULL;
+
+	/* Detection assumes user has sufficient privileges (CAP_SYS_ADMIN).
+	 * Let's approximate, and restrict usage to root user only.
+	 */
+	if (geteuid()) {
+		p_err("please run this command as root user");
+		return -1;
+	}
+
+	set_max_rlimit();
+
+	while (argc) {
+		if (is_prefix(*argv, "kernel")) {
+			if (target != COMPONENT_UNSPEC) {
+				p_err("component to probe already specified");
+				return -1;
+			}
+			target = COMPONENT_KERNEL;
+			NEXT_ARG();
+		} else if (is_prefix(*argv, "macros") && !define_prefix) {
+			define_prefix = "";
+			NEXT_ARG();
+		} else if (is_prefix(*argv, "prefix")) {
+			if (!define_prefix) {
+				p_err("'prefix' argument can only be use after 'macros'");
+				return -1;
+			}
+			if (strcmp(define_prefix, "")) {
+				p_err("'prefix' already defined");
+				return -1;
+			}
+			NEXT_ARG();
+
+			if (!REQ_ARGS(1))
+				return -1;
+			define_prefix = GET_ARG();
+		} else {
+			p_err("expected no more arguments, 'kernel', 'macros' or 'prefix', got: '%s'?",
+			      *argv);
+			return -1;
+		}
+	}
+
+	if (json_output)
+		jsonw_start_object(json_wtr);
+
+	print_start_section("syscall_config",
+			    "/*** System call and kernel version ***/",
+			    "Scanning system call and kernel version...",
+			    define_prefix);
+
+	probe_kernel_version(define_prefix);
+	probe_bpf_syscall(define_prefix);
+
+	if (json_output) {
+		/* End current "section" of probes */
+		jsonw_end_object(json_wtr);
+		/* End root object */
+		jsonw_end_object(json_wtr);
+	}
+
+	return 0;
+}
+
+static int do_help(int argc, char **argv)
+{
+	if (json_output) {
+		jsonw_null(json_wtr);
+		return 0;
+	}
+
+	fprintf(stderr,
+		"Usage: %s %s probe [kernel] [macros [prefix PREFIX]]\n"
+		"       %s %s help\n"
+		"",
+		bin_name, argv[-2], bin_name, argv[-2]);
+
+	return 0;
+}
+
+static const struct cmd cmds[] = {
+	{ "help",	do_help },
+	{ "probe",	do_probe },
+	{ 0 }
+};
+
+int do_feature(int argc, char **argv)
+{
+	return cmd_select(cmds, argc, argv, do_help);
+}
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 9e657e7d5172..baf07f8be737 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -55,7 +55,7 @@ static int do_help(int argc, char **argv)
 		"       %s batch file FILE\n"
 		"       %s version\n"
 		"\n"
-		"       OBJECT := { prog | map | cgroup | perf | net }\n"
+		"       OBJECT := { prog | map | cgroup | perf | net | feature }\n"
 		"       " HELP_SPEC_OPTIONS "\n"
 		"",
 		bin_name, bin_name, bin_name);
@@ -186,6 +186,7 @@ static const struct cmd cmds[] = {
 	{ "cgroup",	do_cgroup },
 	{ "perf",	do_perf },
 	{ "net",	do_net },
+	{ "feature",	do_feature },
 	{ "version",	do_version },
 	{ 0 }
 };
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index d2beb88f0e2e..2acd8c08e8b6 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -141,6 +141,7 @@ int do_cgroup(int argc, char **arg);
 int do_perf(int argc, char **arg);
 int do_net(int argc, char **arg);
 int do_tracelog(int argc, char **arg);
+int do_feature(int argc, char **argv);
 
 int parse_u32_arg(int *argc, char ***argv, __u32 *val, const char *what);
 int prog_parse_fd(int *argc, char ***argv);
-- 
2.17.1

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