// 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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if (tgid) {
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wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
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umd_cleanup_helper(&umd_ops.info);
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}
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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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struct pid *tgid;
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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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tgid = umd_ops.info.tgid;
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if (tgid) {
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kill_pid(tgid, SIGKILL, 1);
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wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
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umd_cleanup_helper(&umd_ops.info);
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}
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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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