bpf: Introduce pinnable bpf_link abstraction
Introduce bpf_link abstraction, representing an attachment of BPF program to a BPF hook point (e.g., tracepoint, perf event, etc). bpf_link encapsulates ownership of attached BPF program, reference counting of a link itself, when reference from multiple anonymous inodes, as well as ensures that release callback will be called from a process context, so that users can safely take mutex locks and sleep. Additionally, with a new abstraction it's now possible to generalize pinning of a link object in BPF FS, allowing to explicitly prevent BPF program detachment on process exit by pinning it in a BPF FS and let it open from independent other process to keep working with it. Convert two existing bpf_link-like objects (raw tracepoint and tracing BPF program attachments) into utilizing bpf_link framework, making them pinnable in BPF FS. More FD-based bpf_links will be added in follow up patches. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200303043159.323675-2-andriin@fb.com
This commit is contained in:
Andrii Nakryiko
Alexei Starovoitov
parent
775a2be52d
commit
70ed506c3b
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@ -1056,6 +1056,19 @@ extern int sysctl_unprivileged_bpf_disabled;
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int bpf_map_new_fd(struct bpf_map *map, int flags);
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int bpf_prog_new_fd(struct bpf_prog *prog);
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struct bpf_link;
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struct bpf_link_ops {
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void (*release)(struct bpf_link *link);
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};
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void bpf_link_init(struct bpf_link *link, const struct bpf_link_ops *ops,
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struct bpf_prog *prog);
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void bpf_link_inc(struct bpf_link *link);
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void bpf_link_put(struct bpf_link *link);
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int bpf_link_new_fd(struct bpf_link *link);
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struct bpf_link *bpf_link_get_from_fd(u32 ufd);
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int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
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int bpf_obj_get_user(const char __user *pathname, int flags);
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@ -25,6 +25,7 @@ enum bpf_type {
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BPF_TYPE_UNSPEC = 0,
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BPF_TYPE_PROG,
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BPF_TYPE_MAP,
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BPF_TYPE_LINK,
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};
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static void *bpf_any_get(void *raw, enum bpf_type type)
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@ -36,6 +37,9 @@ static void *bpf_any_get(void *raw, enum bpf_type type)
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case BPF_TYPE_MAP:
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bpf_map_inc_with_uref(raw);
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break;
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case BPF_TYPE_LINK:
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bpf_link_inc(raw);
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break;
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default:
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WARN_ON_ONCE(1);
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break;
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@ -53,6 +57,9 @@ static void bpf_any_put(void *raw, enum bpf_type type)
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case BPF_TYPE_MAP:
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bpf_map_put_with_uref(raw);
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break;
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case BPF_TYPE_LINK:
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bpf_link_put(raw);
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break;
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default:
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WARN_ON_ONCE(1);
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break;
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@ -63,20 +70,32 @@ static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type)
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{
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void *raw;
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*type = BPF_TYPE_MAP;
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raw = bpf_map_get_with_uref(ufd);
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if (IS_ERR(raw)) {
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*type = BPF_TYPE_PROG;
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raw = bpf_prog_get(ufd);
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if (!IS_ERR(raw)) {
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*type = BPF_TYPE_MAP;
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return raw;
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}
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raw = bpf_prog_get(ufd);
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if (!IS_ERR(raw)) {
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*type = BPF_TYPE_PROG;
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return raw;
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}
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raw = bpf_link_get_from_fd(ufd);
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if (!IS_ERR(raw)) {
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*type = BPF_TYPE_LINK;
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return raw;
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}
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return ERR_PTR(-EINVAL);
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}
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static const struct inode_operations bpf_dir_iops;
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static const struct inode_operations bpf_prog_iops = { };
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static const struct inode_operations bpf_map_iops = { };
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static const struct inode_operations bpf_link_iops = { };
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static struct inode *bpf_get_inode(struct super_block *sb,
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const struct inode *dir,
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@ -114,6 +133,8 @@ static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)
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*type = BPF_TYPE_PROG;
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else if (inode->i_op == &bpf_map_iops)
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*type = BPF_TYPE_MAP;
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else if (inode->i_op == &bpf_link_iops)
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*type = BPF_TYPE_LINK;
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else
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return -EACCES;
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@ -335,6 +356,12 @@ static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
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&bpffs_map_fops : &bpffs_obj_fops);
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}
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static int bpf_mklink(struct dentry *dentry, umode_t mode, void *arg)
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{
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return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops,
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&bpffs_obj_fops);
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}
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static struct dentry *
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bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)
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{
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@ -411,6 +438,9 @@ static int bpf_obj_do_pin(const char __user *pathname, void *raw,
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case BPF_TYPE_MAP:
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ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw);
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break;
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case BPF_TYPE_LINK:
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ret = vfs_mkobj(dentry, mode, bpf_mklink, raw);
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break;
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default:
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ret = -EPERM;
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}
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@ -487,6 +517,8 @@ int bpf_obj_get_user(const char __user *pathname, int flags)
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ret = bpf_prog_new_fd(raw);
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else if (type == BPF_TYPE_MAP)
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ret = bpf_map_new_fd(raw, f_flags);
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else if (type == BPF_TYPE_LINK)
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ret = bpf_link_new_fd(raw);
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else
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return -ENOENT;
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@ -504,6 +536,8 @@ static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type
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if (inode->i_op == &bpf_map_iops)
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return ERR_PTR(-EINVAL);
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if (inode->i_op == &bpf_link_iops)
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return ERR_PTR(-EINVAL);
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if (inode->i_op != &bpf_prog_iops)
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return ERR_PTR(-EACCES);
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@ -2173,24 +2173,154 @@ static int bpf_obj_get(const union bpf_attr *attr)
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attr->file_flags);
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}
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static int bpf_tracing_prog_release(struct inode *inode, struct file *filp)
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{
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struct bpf_prog *prog = filp->private_data;
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struct bpf_link {
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atomic64_t refcnt;
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const struct bpf_link_ops *ops;
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struct bpf_prog *prog;
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struct work_struct work;
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};
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WARN_ON_ONCE(bpf_trampoline_unlink_prog(prog));
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void bpf_link_init(struct bpf_link *link, const struct bpf_link_ops *ops,
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struct bpf_prog *prog)
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{
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atomic64_set(&link->refcnt, 1);
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link->ops = ops;
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link->prog = prog;
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}
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void bpf_link_inc(struct bpf_link *link)
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{
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atomic64_inc(&link->refcnt);
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}
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/* bpf_link_free is guaranteed to be called from process context */
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static void bpf_link_free(struct bpf_link *link)
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{
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struct bpf_prog *prog;
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/* remember prog locally, because release below will free link memory */
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prog = link->prog;
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/* extra clean up and kfree of container link struct */
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link->ops->release(link);
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/* no more accesing of link members after this point */
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bpf_prog_put(prog);
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}
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static void bpf_link_put_deferred(struct work_struct *work)
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{
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struct bpf_link *link = container_of(work, struct bpf_link, work);
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bpf_link_free(link);
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}
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/* bpf_link_put can be called from atomic context, but ensures that resources
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* are freed from process context
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*/
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void bpf_link_put(struct bpf_link *link)
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{
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if (!atomic64_dec_and_test(&link->refcnt))
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return;
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if (in_atomic()) {
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INIT_WORK(&link->work, bpf_link_put_deferred);
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schedule_work(&link->work);
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} else {
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bpf_link_free(link);
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}
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}
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static int bpf_link_release(struct inode *inode, struct file *filp)
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{
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struct bpf_link *link = filp->private_data;
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bpf_link_put(link);
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return 0;
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}
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static const struct file_operations bpf_tracing_prog_fops = {
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.release = bpf_tracing_prog_release,
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#ifdef CONFIG_PROC_FS
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static const struct bpf_link_ops bpf_raw_tp_lops;
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static const struct bpf_link_ops bpf_tracing_link_lops;
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static const struct bpf_link_ops bpf_xdp_link_lops;
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static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
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{
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const struct bpf_link *link = filp->private_data;
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const struct bpf_prog *prog = link->prog;
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char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
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const char *link_type;
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if (link->ops == &bpf_raw_tp_lops)
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link_type = "raw_tracepoint";
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else if (link->ops == &bpf_tracing_link_lops)
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link_type = "tracing";
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else
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link_type = "unknown";
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bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
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seq_printf(m,
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"link_type:\t%s\n"
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"prog_tag:\t%s\n"
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"prog_id:\t%u\n",
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link_type,
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prog_tag,
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prog->aux->id);
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}
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#endif
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const struct file_operations bpf_link_fops = {
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#ifdef CONFIG_PROC_FS
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.show_fdinfo = bpf_link_show_fdinfo,
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#endif
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.release = bpf_link_release,
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.read = bpf_dummy_read,
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.write = bpf_dummy_write,
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};
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int bpf_link_new_fd(struct bpf_link *link)
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{
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return anon_inode_getfd("bpf-link", &bpf_link_fops, link, O_CLOEXEC);
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}
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struct bpf_link *bpf_link_get_from_fd(u32 ufd)
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{
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struct fd f = fdget(ufd);
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struct bpf_link *link;
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if (!f.file)
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return ERR_PTR(-EBADF);
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if (f.file->f_op != &bpf_link_fops) {
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fdput(f);
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return ERR_PTR(-EINVAL);
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}
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link = f.file->private_data;
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bpf_link_inc(link);
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fdput(f);
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return link;
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}
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struct bpf_tracing_link {
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struct bpf_link link;
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};
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static void bpf_tracing_link_release(struct bpf_link *link)
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{
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struct bpf_tracing_link *tr_link =
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container_of(link, struct bpf_tracing_link, link);
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WARN_ON_ONCE(bpf_trampoline_unlink_prog(link->prog));
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kfree(tr_link);
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}
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static const struct bpf_link_ops bpf_tracing_link_lops = {
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.release = bpf_tracing_link_release,
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};
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static int bpf_tracing_prog_attach(struct bpf_prog *prog)
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{
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int tr_fd, err;
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struct bpf_tracing_link *link;
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int link_fd, err;
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if (prog->expected_attach_type != BPF_TRACE_FENTRY &&
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prog->expected_attach_type != BPF_TRACE_FEXIT &&
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@ -2199,58 +2329,61 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog)
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goto out_put_prog;
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}
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err = bpf_trampoline_link_prog(prog);
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if (err)
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goto out_put_prog;
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tr_fd = anon_inode_getfd("bpf-tracing-prog", &bpf_tracing_prog_fops,
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prog, O_CLOEXEC);
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if (tr_fd < 0) {
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WARN_ON_ONCE(bpf_trampoline_unlink_prog(prog));
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err = tr_fd;
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link = kzalloc(sizeof(*link), GFP_USER);
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if (!link) {
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err = -ENOMEM;
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goto out_put_prog;
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}
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return tr_fd;
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bpf_link_init(&link->link, &bpf_tracing_link_lops, prog);
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err = bpf_trampoline_link_prog(prog);
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if (err)
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goto out_free_link;
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link_fd = bpf_link_new_fd(&link->link);
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if (link_fd < 0) {
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WARN_ON_ONCE(bpf_trampoline_unlink_prog(prog));
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err = link_fd;
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goto out_free_link;
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}
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return link_fd;
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out_free_link:
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kfree(link);
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out_put_prog:
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bpf_prog_put(prog);
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return err;
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}
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struct bpf_raw_tracepoint {
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struct bpf_raw_tp_link {
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struct bpf_link link;
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struct bpf_raw_event_map *btp;
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struct bpf_prog *prog;
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};
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static int bpf_raw_tracepoint_release(struct inode *inode, struct file *filp)
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static void bpf_raw_tp_link_release(struct bpf_link *link)
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{
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struct bpf_raw_tracepoint *raw_tp = filp->private_data;
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struct bpf_raw_tp_link *raw_tp =
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container_of(link, struct bpf_raw_tp_link, link);
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if (raw_tp->prog) {
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bpf_probe_unregister(raw_tp->btp, raw_tp->prog);
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bpf_prog_put(raw_tp->prog);
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}
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bpf_probe_unregister(raw_tp->btp, raw_tp->link.prog);
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bpf_put_raw_tracepoint(raw_tp->btp);
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kfree(raw_tp);
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return 0;
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}
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static const struct file_operations bpf_raw_tp_fops = {
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.release = bpf_raw_tracepoint_release,
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.read = bpf_dummy_read,
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.write = bpf_dummy_write,
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static const struct bpf_link_ops bpf_raw_tp_lops = {
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.release = bpf_raw_tp_link_release,
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};
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#define BPF_RAW_TRACEPOINT_OPEN_LAST_FIELD raw_tracepoint.prog_fd
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static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
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{
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struct bpf_raw_tracepoint *raw_tp;
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struct bpf_raw_tp_link *raw_tp;
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struct bpf_raw_event_map *btp;
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struct bpf_prog *prog;
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const char *tp_name;
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char buf[128];
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int tp_fd, err;
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int link_fd, err;
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if (CHECK_ATTR(BPF_RAW_TRACEPOINT_OPEN))
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return -EINVAL;
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@ -2302,21 +2435,20 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr)
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err = -ENOMEM;
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goto out_put_btp;
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}
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bpf_link_init(&raw_tp->link, &bpf_raw_tp_lops, prog);
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raw_tp->btp = btp;
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raw_tp->prog = prog;
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err = bpf_probe_register(raw_tp->btp, prog);
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if (err)
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goto out_free_tp;
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tp_fd = anon_inode_getfd("bpf-raw-tracepoint", &bpf_raw_tp_fops, raw_tp,
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O_CLOEXEC);
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if (tp_fd < 0) {
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link_fd = bpf_link_new_fd(&raw_tp->link);
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if (link_fd < 0) {
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bpf_probe_unregister(raw_tp->btp, prog);
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err = tp_fd;
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err = link_fd;
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goto out_free_tp;
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}
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return tp_fd;
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return link_fd;
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out_free_tp:
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kfree(raw_tp);
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@ -3266,16 +3398,22 @@ static int bpf_task_fd_query(const union bpf_attr *attr,
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if (err)
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goto out;
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if (file->f_op == &bpf_raw_tp_fops) {
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struct bpf_raw_tracepoint *raw_tp = file->private_data;
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if (file->f_op == &bpf_link_fops) {
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struct bpf_link *link = file->private_data;
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if (link->ops == &bpf_raw_tp_lops) {
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struct bpf_raw_tp_link *raw_tp =
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container_of(link, struct bpf_raw_tp_link, link);
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struct bpf_raw_event_map *btp = raw_tp->btp;
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err = bpf_task_fd_query_copy(attr, uattr,
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raw_tp->prog->aux->id,
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raw_tp->link.prog->aux->id,
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BPF_FD_TYPE_RAW_TRACEPOINT,
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btp->tp->name, 0, 0);
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goto put_file;
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}
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||||
goto out_not_supp;
|
||||
}
|
||||
|
||||
event = perf_get_event(file);
|
||||
if (!IS_ERR(event)) {
|
||||
|
|
@ -3294,6 +3432,7 @@ static int bpf_task_fd_query(const union bpf_attr *attr,
|
|||
goto put_file;
|
||||
}
|
||||
|
||||
out_not_supp:
|
||||
err = -ENOTSUPP;
|
||||
put_file:
|
||||
fput(file);
|
||||
|
|
|
|||
Loading…
Reference in New Issue