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| struct bpf_probes *p; | ||
| struct ring_buffer_opts ringbuf_opts; | ||
| int cgroup_fd, i, off, ringbuf_fd; | ||
| char *cgroup_unmount; |
| } | ||
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| /* | ||
| * No cgroup2 mount found, try mountint it ourselves at |
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| * No cgroup2 mount found, try mountint it ourselves at | |
| * No cgroup2 mount found, try to mount it ourselves at |
| char template[] = "/tmp/quark_cgroup2_mount.XXXXXX"; | ||
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| if ((path = mkdtemp(template)) == NULL) { | ||
| qwarn("mktemp %s", template); |
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| qwarn("mktemp %s", template); | |
| qwarn("mkdtemp %s", template); |
| goto fail; | ||
| } | ||
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| *unmount_path = strdup(path); |
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we check for strdup failures on line 585. should make them consistent. if it fails (and all other code miraculously works) we will fail to umount the custom cgroup2 mount.
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I thought about it, it would basically just leave it dangling, while in practice that strdup will never fail, so I just ignored. I can add some print at least
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nicholasberlin
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Sep 24, 2025
| free(path); | ||
| if (fd != -1) | ||
| close(fd); | ||
| cgroup2_umount_tmp(umount_path); |
This looks up the path for cgroup2, in case it's not in /sys/fs/cgroup, but more importantly, it makes sure /sys/fs/cgroup is a cgroup2, and if not, it attempts to mount a temporary cgroup2 for loading the DNS probes. On some systems, cgroup2 is not mounted by default, even though the kernel supports it. For DNS and/or every future cgroup probe to function, we need to fetch the cgroup mounting point pass it to bpf_probes__load(). After that the fd is not really needed, we can close and also unmount the temporary cgroup2 mount we might have created. Idea from Nick.
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his looks up the path for cgroup2, in case it's not in /sys/fs/cgroup, but more
importantly, it makes sure /sys/fs/cgroup is a cgroup2, and if not, it attempts
to mount a temporary cgroup2 for loading the DNS probes.
On some systems, cgroup2 is not mounted by default, even though the kernel
supports it.
For DNS and/or every future cgroup probe to function, we need to fetch the
cgroup mounting point pass it to bpf_probes__load(). After that the fd is not
really needed, we can close and also unmount the temporary cgroup2 mount we
might have created.
Idea from Nick.