https://github.com/torvalds/linux
Tip revision: bb6d3fb354c5ee8d6bde2d576eb7220ea09862b9 authored by Linus Torvalds on 10 February 2020, 00:08:48 UTC
Linux 5.6-rc1
Linux 5.6-rc1
Tip revision: bb6d3fb
feature.c
// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (c) 2019 Netronome Systems, Inc. */
#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <net/if.h>
#include <sys/utsname.h>
#include <sys/vfs.h>
#include <linux/filter.h>
#include <linux/limits.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include <zlib.h>
#include "main.h"
#ifndef PROC_SUPER_MAGIC
# define PROC_SUPER_MAGIC 0x9fa0
#endif
enum probe_component {
COMPONENT_UNSPEC,
COMPONENT_KERNEL,
COMPONENT_DEVICE,
};
#define BPF_HELPER_MAKE_ENTRY(name) [BPF_FUNC_ ## name] = "bpf_" # name
static const char * const helper_name[] = {
__BPF_FUNC_MAPPER(BPF_HELPER_MAKE_ENTRY)
};
#undef BPF_HELPER_MAKE_ENTRY
/* Miscellaneous utility functions */
static bool check_procfs(void)
{
struct statfs st_fs;
if (statfs("/proc", &st_fs) < 0)
return false;
if ((unsigned long)st_fs.f_type != PROC_SUPER_MAGIC)
return false;
return true;
}
static void uppercase(char *str, size_t len)
{
size_t i;
for (i = 0; i < len && str[i] != '\0'; i++)
str[i] = toupper(str[i]);
}
/* Printing utility functions */
static void
print_bool_feature(const char *feat_name, const char *plain_name,
const char *define_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%sHAVE_%s\n", define_prefix,
res ? "" : "NO_", define_name);
else
printf("%s is %savailable\n", plain_name, res ? "" : "NOT ");
}
static void print_kernel_option(const char *name, const char *value)
{
char *endptr;
int res;
/* No support for C-style ouptut */
if (json_output) {
if (!value) {
jsonw_null_field(json_wtr, name);
return;
}
errno = 0;
res = strtol(value, &endptr, 0);
if (!errno && *endptr == '\n')
jsonw_int_field(json_wtr, name, res);
else
jsonw_string_field(json_wtr, name, value);
} else {
if (value)
printf("%s is set to %s\n", name, value);
else
printf("%s is not set\n", name);
}
}
static void
print_start_section(const char *json_title, const char *plain_title,
const char *define_comment, 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);
}
}
static void
print_end_then_start_section(const char *json_title, const char *plain_title,
const char *define_comment,
const char *define_prefix)
{
if (json_output)
jsonw_end_object(json_wtr);
else
printf("\n");
print_start_section(json_title, plain_title, define_comment,
define_prefix);
}
/* Probing functions */
static int read_procfs(const char *path)
{
char *endptr, *line = NULL;
size_t len = 0;
FILE *fd;
int res;
fd = fopen(path, "r");
if (!fd)
return -1;
res = getline(&line, &len, fd);
fclose(fd);
if (res < 0)
return -1;
errno = 0;
res = strtol(line, &endptr, 10);
if (errno || *line == '\0' || *endptr != '\n')
res = -1;
free(line);
return res;
}
static void probe_unprivileged_disabled(void)
{
int res;
/* No support for C-style ouptut */
res = read_procfs("/proc/sys/kernel/unprivileged_bpf_disabled");
if (json_output) {
jsonw_int_field(json_wtr, "unprivileged_bpf_disabled", res);
} else {
switch (res) {
case 0:
printf("bpf() syscall for unprivileged users is enabled\n");
break;
case 1:
printf("bpf() syscall restricted to privileged users\n");
break;
case -1:
printf("Unable to retrieve required privileges for bpf() syscall\n");
break;
default:
printf("bpf() syscall restriction has unknown value %d\n", res);
}
}
}
static void probe_jit_enable(void)
{
int res;
/* No support for C-style ouptut */
res = read_procfs("/proc/sys/net/core/bpf_jit_enable");
if (json_output) {
jsonw_int_field(json_wtr, "bpf_jit_enable", res);
} else {
switch (res) {
case 0:
printf("JIT compiler is disabled\n");
break;
case 1:
printf("JIT compiler is enabled\n");
break;
case 2:
printf("JIT compiler is enabled with debugging traces in kernel logs\n");
break;
case -1:
printf("Unable to retrieve JIT-compiler status\n");
break;
default:
printf("JIT-compiler status has unknown value %d\n",
res);
}
}
}
static void probe_jit_harden(void)
{
int res;
/* No support for C-style ouptut */
res = read_procfs("/proc/sys/net/core/bpf_jit_harden");
if (json_output) {
jsonw_int_field(json_wtr, "bpf_jit_harden", res);
} else {
switch (res) {
case 0:
printf("JIT compiler hardening is disabled\n");
break;
case 1:
printf("JIT compiler hardening is enabled for unprivileged users\n");
break;
case 2:
printf("JIT compiler hardening is enabled for all users\n");
break;
case -1:
printf("Unable to retrieve JIT hardening status\n");
break;
default:
printf("JIT hardening status has unknown value %d\n",
res);
}
}
}
static void probe_jit_kallsyms(void)
{
int res;
/* No support for C-style ouptut */
res = read_procfs("/proc/sys/net/core/bpf_jit_kallsyms");
if (json_output) {
jsonw_int_field(json_wtr, "bpf_jit_kallsyms", res);
} else {
switch (res) {
case 0:
printf("JIT compiler kallsyms exports are disabled\n");
break;
case 1:
printf("JIT compiler kallsyms exports are enabled for root\n");
break;
case -1:
printf("Unable to retrieve JIT kallsyms export status\n");
break;
default:
printf("JIT kallsyms exports status has unknown value %d\n", res);
}
}
}
static void probe_jit_limit(void)
{
int res;
/* No support for C-style ouptut */
res = read_procfs("/proc/sys/net/core/bpf_jit_limit");
if (json_output) {
jsonw_int_field(json_wtr, "bpf_jit_limit", res);
} else {
switch (res) {
case -1:
printf("Unable to retrieve global memory limit for JIT compiler for unprivileged users\n");
break;
default:
printf("Global memory limit for JIT compiler for unprivileged users is %d bytes\n", res);
}
}
}
static bool read_next_kernel_config_option(gzFile file, char *buf, size_t n,
char **value)
{
char *sep;
while (gzgets(file, buf, n)) {
if (strncmp(buf, "CONFIG_", 7))
continue;
sep = strchr(buf, '=');
if (!sep)
continue;
/* Trim ending '\n' */
buf[strlen(buf) - 1] = '\0';
/* Split on '=' and ensure that a value is present. */
*sep = '\0';
if (!sep[1])
continue;
*value = sep + 1;
return true;
}
return false;
}
static void probe_kernel_image_config(void)
{
static const char * const options[] = {
/* Enable BPF */
"CONFIG_BPF",
/* Enable bpf() syscall */
"CONFIG_BPF_SYSCALL",
/* Does selected architecture support eBPF JIT compiler */
"CONFIG_HAVE_EBPF_JIT",
/* Compile eBPF JIT compiler */
"CONFIG_BPF_JIT",
/* Avoid compiling eBPF interpreter (use JIT only) */
"CONFIG_BPF_JIT_ALWAYS_ON",
/* cgroups */
"CONFIG_CGROUPS",
/* BPF programs attached to cgroups */
"CONFIG_CGROUP_BPF",
/* bpf_get_cgroup_classid() helper */
"CONFIG_CGROUP_NET_CLASSID",
/* bpf_skb_{,ancestor_}cgroup_id() helpers */
"CONFIG_SOCK_CGROUP_DATA",
/* Tracing: attach BPF to kprobes, tracepoints, etc. */
"CONFIG_BPF_EVENTS",
/* Kprobes */
"CONFIG_KPROBE_EVENTS",
/* Uprobes */
"CONFIG_UPROBE_EVENTS",
/* Tracepoints */
"CONFIG_TRACING",
/* Syscall tracepoints */
"CONFIG_FTRACE_SYSCALLS",
/* bpf_override_return() helper support for selected arch */
"CONFIG_FUNCTION_ERROR_INJECTION",
/* bpf_override_return() helper */
"CONFIG_BPF_KPROBE_OVERRIDE",
/* Network */
"CONFIG_NET",
/* AF_XDP sockets */
"CONFIG_XDP_SOCKETS",
/* BPF_PROG_TYPE_LWT_* and related helpers */
"CONFIG_LWTUNNEL_BPF",
/* BPF_PROG_TYPE_SCHED_ACT, TC (traffic control) actions */
"CONFIG_NET_ACT_BPF",
/* BPF_PROG_TYPE_SCHED_CLS, TC filters */
"CONFIG_NET_CLS_BPF",
/* TC clsact qdisc */
"CONFIG_NET_CLS_ACT",
/* Ingress filtering with TC */
"CONFIG_NET_SCH_INGRESS",
/* bpf_skb_get_xfrm_state() helper */
"CONFIG_XFRM",
/* bpf_get_route_realm() helper */
"CONFIG_IP_ROUTE_CLASSID",
/* BPF_PROG_TYPE_LWT_SEG6_LOCAL and related helpers */
"CONFIG_IPV6_SEG6_BPF",
/* BPF_PROG_TYPE_LIRC_MODE2 and related helpers */
"CONFIG_BPF_LIRC_MODE2",
/* BPF stream parser and BPF socket maps */
"CONFIG_BPF_STREAM_PARSER",
/* xt_bpf module for passing BPF programs to netfilter */
"CONFIG_NETFILTER_XT_MATCH_BPF",
/* bpfilter back-end for iptables */
"CONFIG_BPFILTER",
/* bpftilter module with "user mode helper" */
"CONFIG_BPFILTER_UMH",
/* test_bpf module for BPF tests */
"CONFIG_TEST_BPF",
};
char *values[ARRAY_SIZE(options)] = { };
struct utsname utsn;
char path[PATH_MAX];
gzFile file = NULL;
char buf[4096];
char *value;
size_t i;
if (!uname(&utsn)) {
snprintf(path, sizeof(path), "/boot/config-%s", utsn.release);
/* gzopen also accepts uncompressed files. */
file = gzopen(path, "r");
}
if (!file) {
/* Some distributions build with CONFIG_IKCONFIG=y and put the
* config file at /proc/config.gz.
*/
file = gzopen("/proc/config.gz", "r");
}
if (!file) {
p_info("skipping kernel config, can't open file: %s",
strerror(errno));
goto end_parse;
}
/* Sanity checks */
if (!gzgets(file, buf, sizeof(buf)) ||
!gzgets(file, buf, sizeof(buf))) {
p_info("skipping kernel config, can't read from file: %s",
strerror(errno));
goto end_parse;
}
if (strcmp(buf, "# Automatically generated file; DO NOT EDIT.\n")) {
p_info("skipping kernel config, can't find correct file");
goto end_parse;
}
while (read_next_kernel_config_option(file, buf, sizeof(buf), &value)) {
for (i = 0; i < ARRAY_SIZE(options); i++) {
if (values[i] || strcmp(buf, options[i]))
continue;
values[i] = strdup(value);
}
}
end_parse:
if (file)
gzclose(file);
for (i = 0; i < ARRAY_SIZE(options); i++) {
print_kernel_option(options[i], values[i]);
free(values[i]);
}
}
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 void
probe_prog_type(enum bpf_prog_type prog_type, bool *supported_types,
const char *define_prefix, __u32 ifindex)
{
char feat_name[128], plain_desc[128], define_name[128];
const char *plain_comment = "eBPF program_type ";
size_t maxlen;
bool res;
if (ifindex)
/* Only test offload-able program types */
switch (prog_type) {
case BPF_PROG_TYPE_SCHED_CLS:
case BPF_PROG_TYPE_XDP:
break;
default:
return;
}
res = bpf_probe_prog_type(prog_type, ifindex);
supported_types[prog_type] |= res;
maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1;
if (strlen(prog_type_name[prog_type]) > maxlen) {
p_info("program type name too long");
return;
}
sprintf(feat_name, "have_%s_prog_type", prog_type_name[prog_type]);
sprintf(define_name, "%s_prog_type", prog_type_name[prog_type]);
uppercase(define_name, sizeof(define_name));
sprintf(plain_desc, "%s%s", plain_comment, prog_type_name[prog_type]);
print_bool_feature(feat_name, plain_desc, define_name, res,
define_prefix);
}
static void
probe_map_type(enum bpf_map_type map_type, const char *define_prefix,
__u32 ifindex)
{
char feat_name[128], plain_desc[128], define_name[128];
const char *plain_comment = "eBPF map_type ";
size_t maxlen;
bool res;
res = bpf_probe_map_type(map_type, ifindex);
maxlen = sizeof(plain_desc) - strlen(plain_comment) - 1;
if (strlen(map_type_name[map_type]) > maxlen) {
p_info("map type name too long");
return;
}
sprintf(feat_name, "have_%s_map_type", map_type_name[map_type]);
sprintf(define_name, "%s_map_type", map_type_name[map_type]);
uppercase(define_name, sizeof(define_name));
sprintf(plain_desc, "%s%s", plain_comment, map_type_name[map_type]);
print_bool_feature(feat_name, plain_desc, define_name, res,
define_prefix);
}
static void
probe_helpers_for_progtype(enum bpf_prog_type prog_type, bool supported_type,
const char *define_prefix, __u32 ifindex)
{
const char *ptype_name = prog_type_name[prog_type];
char feat_name[128];
unsigned int id;
bool res;
if (ifindex)
/* Only test helpers for offload-able program types */
switch (prog_type) {
case BPF_PROG_TYPE_SCHED_CLS:
case BPF_PROG_TYPE_XDP:
break;
default:
return;
}
if (json_output) {
sprintf(feat_name, "%s_available_helpers", ptype_name);
jsonw_name(json_wtr, feat_name);
jsonw_start_array(json_wtr);
} else if (!define_prefix) {
printf("eBPF helpers supported for program type %s:",
ptype_name);
}
for (id = 1; id < ARRAY_SIZE(helper_name); id++) {
if (!supported_type)
res = false;
else
res = bpf_probe_helper(id, prog_type, ifindex);
if (json_output) {
if (res)
jsonw_string(json_wtr, helper_name[id]);
} else if (define_prefix) {
printf("#define %sBPF__PROG_TYPE_%s__HELPER_%s %s\n",
define_prefix, ptype_name, helper_name[id],
res ? "1" : "0");
} else {
if (res)
printf("\n\t- %s", helper_name[id]);
}
}
if (json_output)
jsonw_end_array(json_wtr);
else if (!define_prefix)
printf("\n");
}
static void
probe_large_insn_limit(const char *define_prefix, __u32 ifindex)
{
bool res;
res = bpf_probe_large_insn_limit(ifindex);
print_bool_feature("have_large_insn_limit",
"Large program size limit",
"LARGE_INSN_LIMIT",
res, define_prefix);
}
static int do_probe(int argc, char **argv)
{
enum probe_component target = COMPONENT_UNSPEC;
const char *define_prefix = NULL;
bool supported_types[128] = {};
__u32 ifindex = 0;
unsigned int i;
char *ifname;
/* 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, "dev")) {
NEXT_ARG();
if (target != COMPONENT_UNSPEC || ifindex) {
p_err("component to probe already specified");
return -1;
}
if (!REQ_ARGS(1))
return -1;
target = COMPONENT_DEVICE;
ifname = GET_ARG();
ifindex = if_nametoindex(ifname);
if (!ifindex) {
p_err("unrecognized netdevice '%s': %s", ifname,
strerror(errno));
return -1;
}
} 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', 'dev', 'macros' or 'prefix', got: '%s'?",
*argv);
return -1;
}
}
if (json_output) {
define_prefix = NULL;
jsonw_start_object(json_wtr);
}
switch (target) {
case COMPONENT_KERNEL:
case COMPONENT_UNSPEC:
if (define_prefix)
break;
print_start_section("system_config",
"Scanning system configuration...",
NULL, /* define_comment never used here */
NULL); /* define_prefix always NULL here */
if (check_procfs()) {
probe_unprivileged_disabled();
probe_jit_enable();
probe_jit_harden();
probe_jit_kallsyms();
probe_jit_limit();
} else {
p_info("/* procfs not mounted, skipping related probes */");
}
probe_kernel_image_config();
if (json_output)
jsonw_end_object(json_wtr);
else
printf("\n");
break;
default:
break;
}
print_start_section("syscall_config",
"Scanning system call availability...",
"/*** System call availability ***/",
define_prefix);
if (!probe_bpf_syscall(define_prefix))
/* bpf() syscall unavailable, don't probe other BPF features */
goto exit_close_json;
print_end_then_start_section("program_types",
"Scanning eBPF program types...",
"/*** eBPF program types ***/",
define_prefix);
for (i = BPF_PROG_TYPE_UNSPEC + 1; i < ARRAY_SIZE(prog_type_name); i++)
probe_prog_type(i, supported_types, define_prefix, ifindex);
print_end_then_start_section("map_types",
"Scanning eBPF map types...",
"/*** eBPF map types ***/",
define_prefix);
for (i = BPF_MAP_TYPE_UNSPEC + 1; i < map_type_name_size; i++)
probe_map_type(i, define_prefix, ifindex);
print_end_then_start_section("helpers",
"Scanning eBPF helper functions...",
"/*** eBPF helper functions ***/",
define_prefix);
if (define_prefix)
printf("/*\n"
" * Use %sHAVE_PROG_TYPE_HELPER(prog_type_name, helper_name)\n"
" * to determine if <helper_name> is available for <prog_type_name>,\n"
" * e.g.\n"
" * #if %sHAVE_PROG_TYPE_HELPER(xdp, bpf_redirect)\n"
" * // do stuff with this helper\n"
" * #elif\n"
" * // use a workaround\n"
" * #endif\n"
" */\n"
"#define %sHAVE_PROG_TYPE_HELPER(prog_type, helper) \\\n"
" %sBPF__PROG_TYPE_ ## prog_type ## __HELPER_ ## helper\n",
define_prefix, define_prefix, define_prefix,
define_prefix);
for (i = BPF_PROG_TYPE_UNSPEC + 1; i < ARRAY_SIZE(prog_type_name); i++)
probe_helpers_for_progtype(i, supported_types[i],
define_prefix, ifindex);
print_end_then_start_section("misc",
"Scanning miscellaneous eBPF features...",
"/*** eBPF misc features ***/",
define_prefix);
probe_large_insn_limit(define_prefix, ifindex);
exit_close_json:
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 [COMPONENT] [macros [prefix PREFIX]]\n"
" %s %s help\n"
"\n"
" COMPONENT := { kernel | dev NAME }\n"
"",
bin_name, argv[-2], bin_name, argv[-2]);
return 0;
}
static const struct cmd cmds[] = {
{ "probe", do_probe },
{ "help", do_help },
{ 0 }
};
int do_feature(int argc, char **argv)
{
return cmd_select(cmds, argc, argv, do_help);
}