2018-12-20 09:40 UTC-0800 ~ Stanislav Fomichev <s...@fomichev.me>
On 12/20, Quentin Monnet wrote:
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",
...
}
}
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 <quentin.mon...@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicin...@netronome.com>
---
tools/bpf/bpftool/feature.c | 137 ++++++++++++++++++++++++++++++++++++
1 file changed, 137 insertions(+)
+static void probe_kernel_image_config(void)
+{
+ const char * const options[] = {
+ "CONFIG_BPF",
+ "CONFIG_BPF_SYSCALL",
+ "CONFIG_HAVE_EBPF_JIT",
+ "CONFIG_BPF_JIT",
+ "CONFIG_BPF_JIT_ALWAYS_ON",
+ "CONFIG_NET",
+ "CONFIG_XDP_SOCKETS",
+ "CONFIG_CGROUPS",
+ "CONFIG_CGROUP_BPF",
+ "CONFIG_CGROUP_NET_CLASSID",
+ "CONFIG_BPF_EVENTS",
+ "CONFIG_LWTUNNEL_BPF",
+ "CONFIG_NET_ACT_BPF",
+ "CONFIG_NET_CLS_ACT",
+ "CONFIG_NET_CLS_BPF",
+ "CONFIG_NET_SCH_INGRESS",
+ "CONFIG_XFRM",
+ "CONFIG_SOCK_CGROUP_DATA",
+ "CONFIG_IP_ROUTE_CLASSID",
+ "CONFIG_IPV6_SEG6_BPF",
+ "CONFIG_FUNCTION_ERROR_INJECTION",
+ "CONFIG_BPF_KPROBE_OVERRIDE",
+ "CONFIG_BPF_LIRC_MODE2",
+ "CONFIG_NETFILTER_XT_MATCH_BPF",
+ "CONFIG_TEST_BPF",
+ "CONFIG_BPFILTER",
+ "CONFIG_BPFILTER_UMH",
+ "CONFIG_BPF_STREAM_PARSER",
+ };
+ 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) {
+ /* Sometimes config is at /proc/config */
+ fd = fopen("/proc/config", "r");
I wonder whether the order here should be reversed?
1. try /proc/config.gz (CONFIG_IKCONFIG_PROC)
2. if not avail, try /boot/config-$(uname -r)
Because, at the end, /proc/config.gz is the real source of truth (if
available).
What is /proc/config btw? I can see only /proc/config.gz being exported.
Hi Stanislav,
Cilium checks for /proc/config (apparently this is where CoreOS puts its
config file), /proc/config.gz and /boot/config-$(uname -r) [0]. I took
inspiration on that but didn't implement the /proc/config.gz file,
because it would require linking with the libz and I'm not sure this is
worth it. Could be added as a follow-up if necessary.
[0] https://github.com/cilium/cilium/blob/master/bpf/run_probes.sh#L42
