The main change is a move of the single line #include "iterators.lskel.h" from iterators/iterators.c to bpf_preload_kern.c. Which means that generated light skeleton can be used from user space or user mode driver like iterators.c or from the kernel module or the kernel itself. The direct use of light skeleton from the kernel module simplifies the code, since UMD is no longer necessary. The libbpf.a required user space and UMD. The CO-RE in the kernel and generated "loader bpf program" used by the light skeleton are capable to perform complex loading operations traditionally provided by libbpf. In addition UMD approach was launching UMD process every time bpffs has to be mounted. With light skeleton in the kernel the bpf_preload kernel module loads bpf iterators once and pins them multiple times into different bpffs mounts.
Showing the changes to kernel/bpf/inode.c (1 of 9 files). Show all
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| @@ -710,11 +710,10 @@ static DEFINE_MUTEX(bpf_preload_lock); · 709 unmodified lines | ||
| 710 | 710 | static int populate_bpffs(struct dentry *parent) |
| 711 | 711 | { |
| 712 | 712 | struct bpf_preload_info objs[BPF_PRELOAD_LINKS] = {}; |
| 713 | − struct bpf_link *links[BPF_PRELOAD_LINKS] = {}; | |
| 714 | 713 | int err = 0, i; |
| 715 | 714 | |
| 716 | 715 | /* grab the mutex to make sure the kernel interactions with bpf_preload |
| 717 | − * UMD are serialized | |
| 716 | + * are serialized | |
| 718 | 717 | */ |
| 719 | 718 | mutex_lock(&bpf_preload_lock); |
| 720 | 719 | |
| @@ -722,40 +721,22 @@ static int populate_bpffs(struct dentry *parent) · 1 unmodified line | ||
| 722 | 721 | if (!bpf_preload_mod_get()) |
| 723 | 722 | goto out; |
| 724 | 723 | |
| 725 | − if (!bpf_preload_ops->info.tgid) { | |
| 726 | − /* preload() will start UMD that will load BPF iterator programs */ | |
| 727 | − err = bpf_preload_ops->preload(objs); | |
| 728 | − if (err) | |
| 724 | + err = bpf_preload_ops->preload(objs); | |
| 725 | + if (err) | |
| 726 | + goto out_put; | |
| 727 | + for (i = 0; i < BPF_PRELOAD_LINKS; i++) { | |
| 728 | + bpf_link_inc(objs[i].link); | |
| 729 | + err = bpf_iter_link_pin_kernel(parent, | |
| 730 | + objs[i].link_name, objs[i].link); | |
| 731 | + if (err) { | |
| 732 | + bpf_link_put(objs[i].link); | |
| 729 | 733 | goto out_put; |
| 730 | − for (i = 0; i < BPF_PRELOAD_LINKS; i++) { | |
| 731 | − links[i] = bpf_link_by_id(objs[i].link_id); | |
| 732 | − if (IS_ERR(links[i])) { | |
| 733 | − err = PTR_ERR(links[i]); | |
| 734 | − goto out_put; | |
| 735 | − } | |
| 736 | 734 | } |
| 737 | − for (i = 0; i < BPF_PRELOAD_LINKS; i++) { | |
| 738 | − err = bpf_iter_link_pin_kernel(parent, | |
| 739 | − objs[i].link_name, links[i]); | |
| 740 | − if (err) | |
| 741 | − goto out_put; | |
| 742 | − /* do not unlink successfully pinned links even | |
| 743 | − * if later link fails to pin | |
| 744 | − */ | |
| 745 | − links[i] = NULL; | |
| 746 | − } | |
| 747 | − /* finish() will tell UMD process to exit */ | |
| 748 | − err = bpf_preload_ops->finish(); | |
| 749 | − if (err) | |
| 750 | − goto out_put; | |
| 751 | 735 | } |
| 752 | 736 | out_put: |
| 753 | 737 | bpf_preload_mod_put(); |
| 754 | 738 | out: |
| 755 | 739 | mutex_unlock(&bpf_preload_lock); |
| 756 | − for (i = 0; i < BPF_PRELOAD_LINKS && err; i++) | |
| 757 | − if (!IS_ERR_OR_NULL(links[i])) | |
| 758 | − bpf_link_put(links[i]); | |
| 759 | 740 | return err; |
| 760 | 741 | } |
| 761 | 742 | |