// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (c) 2019 Netronome Systems, Inc. */
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/utsname.h>
#include <sys/vfs.h>
#include <linux/filter.h>
#include <linux/limits.h>
#include <bpf.h>
#include "main.h"
#ifndef PROC_SUPER_MAGIC
# define PROC_SUPER_MAGIC 0x9fa0
#endif
enum probe_component {
COMPONENT_UNSPEC,
COMPONENT_KERNEL,
};
/* 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;
}
/* Printing utility functions */
static void
print_bool_feature(const char *feat_name, const char *plain_name, bool res)
{
if (json_output)
jsonw_bool_field(json_wtr, feat_name, res);
else
printf("%s is %savailable\n", plain_name, res ? "" : "NOT ");
}
static void
print_start_section(const char *json_title, const char *plain_title)
{
if (json_output) {
jsonw_name(json_wtr, json_title);
jsonw_start_object(json_wtr);
} else {
printf("%s\n", plain_title);
}
}
/* 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;
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;
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;
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;
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;
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 probe_bpf_syscall(void)
{
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",
res);
return res;
}
static int do_probe(int argc, char **argv)
{
enum probe_component target = COMPONENT_UNSPEC;
/* 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 {
p_err("expected no more arguments, 'kernel', got: '%s'?",
*argv);
return -1;
}
}
if (json_output)
jsonw_start_object(json_wtr);
switch (target) {
case COMPONENT_KERNEL:
case COMPONENT_UNSPEC:
print_start_section("system_config",
"Scanning system configuration...");
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 */");
}
if (json_output)
jsonw_end_object(json_wtr);
else
printf("\n");
break;
}
print_start_section("syscall_config",
"Scanning system call availability...");
probe_bpf_syscall();
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]\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);
}
