From 4567b983f78c8c496d09868a3b108fb496c8d2c9 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Thu, 17 Jan 2019 15:27:52 +0000 Subject: [PATCH] tools: bpftool: add probes for kernel configuration options Add probes to dump a number of options set (or not set) for compiling the kernel image. These parameters provide information about what BPF components should be available on the system. A number of them are not directly related to eBPF, but are in fact used in the kernel as conditions on which to compile, or not to compile, some of the eBPF helper functions. Sample output: # bpftool feature probe kernel Scanning system configuration... ... CONFIG_BPF is set to y CONFIG_BPF_SYSCALL is set to y CONFIG_HAVE_EBPF_JIT is set to y ... # bpftool --pretty --json feature probe kernel { "system_config": { ... "CONFIG_BPF": "y", "CONFIG_BPF_SYSCALL": "y", "CONFIG_HAVE_EBPF_JIT": "y", ... } } v5: - Declare options[] array in probe_kernel_image_config() as static. v4: - Add some options to the list: - CONFIG_TRACING - CONFIG_KPROBE_EVENTS - CONFIG_UPROBE_EVENTS - CONFIG_FTRACE_SYSCALLS - Add comments about those options in the source code. v3: - Add a comment about /proc/config.gz not being supported as a path for the config file at this time. - Use p_info() instead of p_err() on failure to get options from config file, as bpftool keeps probing other parameters and that would possibly create duplicate "error" entries for JSON. v2: - Remove C-style macros output from this patch. - NOT addressed: grouping of those config options into subsections (I don't see an easy way of grouping them at the moment, please see also the discussion on v1 thread). Signed-off-by: Quentin Monnet Reviewed-by: Jakub Kicinski Reviewed-by: Stanislav Fomichev Signed-off-by: Alexei Starovoitov --- tools/bpf/bpftool/feature.c | 182 ++++++++++++++++++++++++++++++++++++ 1 file changed, 182 insertions(+) diff --git a/tools/bpf/bpftool/feature.c b/tools/bpf/bpftool/feature.c index cedc44a61c6e..4a2867439ab7 100644 --- a/tools/bpf/bpftool/feature.c +++ b/tools/bpf/bpftool/feature.c @@ -48,6 +48,30 @@ print_bool_feature(const char *feat_name, const char *plain_name, bool res) printf("%s is %savailable\n", plain_name, res ? "" : "NOT "); } +static void print_kernel_option(const char *name, const char *value) +{ + char *endptr; + int res; + + 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) { @@ -208,6 +232,163 @@ static void probe_jit_limit(void) } } +static char *get_kernel_config_option(FILE *fd, const char *option) +{ + size_t line_n = 0, optlen = strlen(option); + char *res, *strval, *line = NULL; + ssize_t n; + + rewind(fd); + while ((n = getline(&line, &line_n, fd)) > 0) { + if (strncmp(line, option, optlen)) + continue; + /* Check we have at least '=', value, and '\n' */ + if (strlen(line) < optlen + 3) + continue; + if (*(line + optlen) != '=') + continue; + + /* Trim ending '\n' */ + line[strlen(line) - 1] = '\0'; + + /* Copy and return config option value */ + strval = line + optlen + 1; + res = strdup(strval); + free(line); + return res; + } + free(line); + + return NULL; +} + +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 *value, *buf = NULL; + struct utsname utsn; + char path[PATH_MAX]; + size_t i, n; + ssize_t ret; + FILE *fd; + + if (uname(&utsn)) + goto no_config; + + snprintf(path, sizeof(path), "/boot/config-%s", utsn.release); + + fd = fopen(path, "r"); + if (!fd && errno == ENOENT) { + /* Some distributions put the config file at /proc/config, give + * it a try. + * Sometimes it is also at /proc/config.gz but we do not try + * this one for now, it would require linking against libz. + */ + fd = fopen("/proc/config", "r"); + } + if (!fd) { + p_info("skipping kernel config, can't open file: %s", + strerror(errno)); + goto no_config; + } + /* Sanity checks */ + ret = getline(&buf, &n, fd); + ret = getline(&buf, &n, fd); + if (!buf || !ret) { + p_info("skipping kernel config, can't read from file: %s", + strerror(errno)); + free(buf); + goto no_config; + } + if (strcmp(buf, "# Automatically generated file; DO NOT EDIT.\n")) { + p_info("skipping kernel config, can't find correct file"); + free(buf); + goto no_config; + } + free(buf); + + for (i = 0; i < ARRAY_SIZE(options); i++) { + value = get_kernel_config_option(fd, options[i]); + print_kernel_option(options[i], value); + free(value); + } + fclose(fd); + return; + +no_config: + for (i = 0; i < ARRAY_SIZE(options); i++) + print_kernel_option(options[i], NULL); +} + static bool probe_bpf_syscall(void) { bool res; @@ -268,6 +449,7 @@ static int do_probe(int argc, char **argv) } else { p_info("/* procfs not mounted, skipping related probes */"); } + probe_kernel_image_config(); if (json_output) jsonw_end_object(json_wtr); else