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libbpf-tools/profile: Add support for PID-namespacing #5152

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libbpf-tools/profile: Add support for PID-namespacing #5152

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71ba640
libbpf-tools/profile: Add support for PID-namespacing
ekyooo Nov 20, 2024
b0a1119
libbpf_tools/profile: Skip pid ns mapping on pre-5.7 kernels
ekyooo Nov 21, 2024
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20 changes: 17 additions & 3 deletions libbpf-tools/profile.bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,9 @@ const volatile bool user_stacks_only = false;
const volatile bool include_idle = false;
const volatile bool filter_by_pid = false;
const volatile bool filter_by_tid = false;
const volatile bool use_pidns = false;
const volatile __u64 pidns_dev = 0;
const volatile __u64 pidns_ino = 0;

struct {
__uint(type, BPF_MAP_TYPE_STACK_TRACE);
Expand Down Expand Up @@ -47,12 +50,23 @@ struct {
SEC("perf_event")
int do_perf_event(struct bpf_perf_event_data *ctx)
{
u64 id = bpf_get_current_pid_tgid();
u32 pid = id >> 32;
u32 tid = id;
u64 *valp;
static const u64 zero;
struct key_t key = {};
u64 id;
u32 pid;
u32 tid;
struct bpf_pidns_info ns = {};

if (use_pidns && !bpf_get_ns_current_pid_tgid(pidns_dev, pidns_ino, &ns,
sizeof(struct bpf_pidns_info))) {
pid = ns.tgid;
tid = ns.pid;
} else {
id = bpf_get_current_pid_tgid();
pid = id >> 32;
tid = id;
}

if (!include_idle && tid == 0)
return 0;
Expand Down
40 changes: 40 additions & 0 deletions libbpf-tools/profile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,10 @@
#include <time.h>
#include <linux/perf_event.h>
#include <asm/unistd.h>
#include <sys/utsname.h>
#include <bpf/libbpf.h>
#include <bpf/bpf.h>
#include <sys/stat.h>
#include "profile.h"
#include "profile.skel.h"
#include "trace_helpers.h"
Expand Down Expand Up @@ -506,6 +508,40 @@ static int print_counts(int counts_map, int stack_map)
return ret;
}

static int kernel_at_least(int req_major, int req_minor) {
struct utsname u;
int major, minor;

if (uname(&u) == -1)
return -errno;

if (sscanf(u.release, "%d.%d", &major, &minor) != 2)
return -errno;

return !((major > req_major) || (major == req_major && minor >= req_minor));
}

static int set_pidns(const struct profile_bpf *obj)
{
struct stat statbuf;

/*
* Available on Linux version 5.7 and above, which includes
* the helper function bpf_get_ns_current_pid_tgid().
*/
if (kernel_at_least(5, 7))
return -EPERM;
Comment on lines +532 to +533
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The problem with fixed version check is that they will not work on kernel where a specific patch could have been backported.
Is there a way to rather check for the existence of a given bpf helper?

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In bcc/tools, we have a few cases (including profile) checking kernel version for bpf_get_ns_current_pid_tgid() availability. But for libbpf-tools, I think we can do better.
See trace_helpers.c. There are a few probe_*() functions which tries to detect whether a particular feature (prog_type, map_type) is supported or not. I think we can have another probe function to check whether bpf_get_ns_current_pid_tgid() is supported or not.


if (stat("/proc/self/ns/pid", &statbuf) == -1)
return -errno;

obj->rodata->use_pidns = true;
obj->rodata->pidns_dev = statbuf.st_dev;
obj->rodata->pidns_ino = statbuf.st_ino;

return 0;
}

static void print_headers()
{
int i;
Expand Down Expand Up @@ -595,6 +631,10 @@ int main(int argc, char **argv)
env.perf_max_stack_depth * sizeof(unsigned long));
bpf_map__set_max_entries(obj->maps.stackmap, env.stack_storage_size);

err = set_pidns(obj);
if (err)
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Let us do 'err && env.verbose' here. We want to print out the below information under verbose mode.

fprintf(stderr, "failed to translate pidns: %s\n", strerror(-err));

err = profile_bpf__load(obj);
if (err) {
fprintf(stderr, "failed to load BPF programs\n");
Expand Down
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