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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;
wait_event(tgid->wait_pidfd, thread_group_exited(tgid));
umd_ops.info.tgid = NULL;
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)
{
bpf_preload_ops = NULL;
/* kill UMD in case it's still there due to earlier error */
kill_pid(umd_ops.info.tgid, SIGKILL, 1);
umd_ops.info.tgid = NULL;
umd_unload_blob(&umd_ops.info);
}
late_initcall(load_umd);
module_exit(fini_umd);
MODULE_LICENSE("GPL");
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