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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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25 changes: 24 additions & 1 deletion libbpf-tools/profile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
#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>
Expand Down Expand Up @@ -507,10 +508,30 @@ 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;

Expand Down Expand Up @@ -610,7 +631,9 @@ 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);

set_pidns(obj);
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) {
Expand Down
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