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Add kernel module with user mode driver that populates bpffs with BPF iterators. $ mount bpffs /my/bpffs/ -t bpf $ ls -la /my/bpffs/ total 4 drwxrwxrwt 2 root root 0 Jul 2 00:27 . drwxr-xr-x 19 root root 4096 Jul 2 00:09 .. -rw------- 1 root root 0 Jul 2 00:27 maps.debug -rw------- 1 root root 0 Jul 2 00:27 progs.debug The user mode driver will load BPF Type Formats, create BPF maps, populate BPF maps, load two BPF programs, attach them to BPF iterators, and finally send two bpf_link IDs back to the kernel. The kernel will pin two bpf_links into newly mounted bpffs instance under names "progs.debug" and "maps.debug". These two files become human readable. $ cat /my/bpffs/progs.debug id name attached 11 dump_bpf_map bpf_iter_bpf_map 12 dump_bpf_prog bpf_iter_bpf_prog 27 test_pkt_access 32 test_main test_pkt_access test_pkt_access 33 test_subprog1 test_pkt_access_subprog1 test_pkt_access 34 test_subprog2 test_pkt_access_subprog2 test_pkt_access 35 test_subprog3 test_pkt_access_subprog3 test_pkt_access 36 new_get_skb_len get_skb_len test_pkt_access 37 new_get_skb_ifindex get_skb_ifindex test_pkt_access 38 new_get_constant get_constant test_pkt_access The BPF program dump_bpf_prog() in iterators.bpf.c is printing this data about all BPF programs currently loaded in the system. This information is unstable and will change from kernel to kernel as ".debug" suffix conveys. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20200819042759.51280-4-alexei.starovoitov@gmail.com
91 lines
2 KiB
C
91 lines
2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/pid.h>
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#include <linux/fs.h>
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#include <linux/sched/signal.h>
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#include "bpf_preload.h"
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extern char bpf_preload_umd_start;
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extern char bpf_preload_umd_end;
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static int preload(struct bpf_preload_info *obj);
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static int finish(void);
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static struct bpf_preload_ops umd_ops = {
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.info.driver_name = "bpf_preload",
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.preload = preload,
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.finish = finish,
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.owner = THIS_MODULE,
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};
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static int preload(struct bpf_preload_info *obj)
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{
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int magic = BPF_PRELOAD_START;
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loff_t pos = 0;
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int i, err;
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ssize_t n;
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err = fork_usermode_driver(&umd_ops.info);
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if (err)
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return err;
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/* send the start magic to let UMD proceed with loading BPF progs */
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n = kernel_write(umd_ops.info.pipe_to_umh,
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&magic, sizeof(magic), &pos);
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if (n != sizeof(magic))
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return -EPIPE;
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/* receive bpf_link IDs and names from UMD */
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pos = 0;
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for (i = 0; i < BPF_PRELOAD_LINKS; i++) {
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n = kernel_read(umd_ops.info.pipe_from_umh,
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&obj[i], sizeof(*obj), &pos);
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if (n != sizeof(*obj))
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return -EPIPE;
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}
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return 0;
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}
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static int finish(void)
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{
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int magic = BPF_PRELOAD_END;
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struct pid *tgid;
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loff_t pos = 0;
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ssize_t n;
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/* send the last magic to UMD. It will do a normal exit. */
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n = kernel_write(umd_ops.info.pipe_to_umh,
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&magic, sizeof(magic), &pos);
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if (n != sizeof(magic))
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return -EPIPE;
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tgid = umd_ops.info.tgid;
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wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
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umd_ops.info.tgid = NULL;
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return 0;
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}
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static int __init load_umd(void)
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{
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int err;
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err = umd_load_blob(&umd_ops.info, &bpf_preload_umd_start,
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&bpf_preload_umd_end - &bpf_preload_umd_start);
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if (err)
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return err;
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bpf_preload_ops = &umd_ops;
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return err;
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}
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static void __exit fini_umd(void)
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{
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bpf_preload_ops = NULL;
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/* kill UMD in case it's still there due to earlier error */
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kill_pid(umd_ops.info.tgid, SIGKILL, 1);
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umd_ops.info.tgid = NULL;
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umd_unload_blob(&umd_ops.info);
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}
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late_initcall(load_umd);
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module_exit(fini_umd);
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MODULE_LICENSE("GPL");
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