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- // SPDX-License-Identifier: GPL-2.0
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/init.h>
- #include <linux/module.h>
- #include <linux/pid.h>
- #include <linux/fs.h>
- #include <linux/sched/signal.h>
- #include "bpf_preload.h"
- extern char bpf_preload_umd_start;
- extern char bpf_preload_umd_end;
- static int preload(struct bpf_preload_info *obj);
- static int finish(void);
- static struct bpf_preload_ops umd_ops = {
- .info.driver_name = "bpf_preload",
- .preload = preload,
- .finish = finish,
- .owner = THIS_MODULE,
- };
- static int preload(struct bpf_preload_info *obj)
- {
- int magic = BPF_PRELOAD_START;
- loff_t pos = 0;
- int i, err;
- ssize_t n;
- err = fork_usermode_driver(&umd_ops.info);
- if (err)
- return err;
- /* send the start magic to let UMD proceed with loading BPF progs */
- n = kernel_write(umd_ops.info.pipe_to_umh,
- &magic, sizeof(magic), &pos);
- if (n != sizeof(magic))
- return -EPIPE;
- /* receive bpf_link IDs and names from UMD */
- pos = 0;
- for (i = 0; i < BPF_PRELOAD_LINKS; i++) {
- n = kernel_read(umd_ops.info.pipe_from_umh,
- &obj[i], sizeof(*obj), &pos);
- if (n != sizeof(*obj))
- return -EPIPE;
- }
- return 0;
- }
- static int finish(void)
- {
- int magic = BPF_PRELOAD_END;
- struct pid *tgid;
- loff_t pos = 0;
- ssize_t n;
- /* send the last magic to UMD. It will do a normal exit. */
- n = kernel_write(umd_ops.info.pipe_to_umh,
- &magic, sizeof(magic), &pos);
- if (n != sizeof(magic))
- return -EPIPE;
- tgid = umd_ops.info.tgid;
- if (tgid) {
- wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
- umd_cleanup_helper(&umd_ops.info);
- }
- return 0;
- }
- static int __init load_umd(void)
- {
- int err;
- err = umd_load_blob(&umd_ops.info, &bpf_preload_umd_start,
- &bpf_preload_umd_end - &bpf_preload_umd_start);
- if (err)
- return err;
- bpf_preload_ops = &umd_ops;
- return err;
- }
- static void __exit fini_umd(void)
- {
- struct pid *tgid;
- bpf_preload_ops = NULL;
- /* kill UMD in case it's still there due to earlier error */
- tgid = umd_ops.info.tgid;
- if (tgid) {
- kill_pid(tgid, SIGKILL, 1);
- wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
- umd_cleanup_helper(&umd_ops.info);
- }
- umd_unload_blob(&umd_ops.info);
- }
- late_initcall(load_umd);
- module_exit(fini_umd);
- MODULE_LICENSE("GPL");
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