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bpf: Implement common macros/helpers for target iterators
Macro DEFINE_BPF_ITER_FUNC is implemented so target can define an init function to capture the BTF type which represents the target. The bpf_iter_meta is a structure holding meta data, common to all targets in the bpf program. Additional marker functions are called before or after bpf_seq_read() show()/next()/stop() callback functions to help calculate precise seq_num and whether call bpf_prog inside stop(). Two functions, bpf_iter_get_info() and bpf_iter_run_prog(), are implemented so target can get needed information from bpf_iter infrastructure and can run the program. Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/20200509175907.2475956-1-yhs@fb.com
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@ -1129,6 +1129,9 @@ 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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#define BPF_ITER_FUNC_PREFIX "__bpf_iter__"
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#define DEFINE_BPF_ITER_FUNC(target, args...) \
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extern int __bpf_iter__ ## target(args); \
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int __init __bpf_iter__ ## target(args) { return 0; }
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typedef int (*bpf_iter_init_seq_priv_t)(void *private_data);
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typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);
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@ -1141,12 +1144,20 @@ struct bpf_iter_reg {
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u32 seq_priv_size;
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};
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struct bpf_iter_meta {
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__bpf_md_ptr(struct seq_file *, seq);
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u64 session_id;
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u64 seq_num;
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};
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int bpf_iter_reg_target(struct bpf_iter_reg *reg_info);
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void bpf_iter_unreg_target(const char *target);
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bool bpf_iter_prog_supported(struct bpf_prog *prog);
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int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
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int bpf_iter_new_fd(struct bpf_link *link);
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bool bpf_link_is_iter(struct bpf_link *link);
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struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop);
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int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx);
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int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
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int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
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@ -41,6 +41,33 @@ static atomic64_t session_id;
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static int prepare_seq_file(struct file *file, struct bpf_iter_link *link);
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static void bpf_iter_inc_seq_num(struct seq_file *seq)
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{
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struct bpf_iter_priv_data *iter_priv;
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iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
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target_private);
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iter_priv->seq_num++;
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}
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static void bpf_iter_dec_seq_num(struct seq_file *seq)
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{
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struct bpf_iter_priv_data *iter_priv;
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iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
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target_private);
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iter_priv->seq_num--;
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}
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static void bpf_iter_done_stop(struct seq_file *seq)
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{
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struct bpf_iter_priv_data *iter_priv;
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iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
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target_private);
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iter_priv->done_stop = true;
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}
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/* bpf_seq_read, a customized and simpler version for bpf iterator.
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* no_llseek is assumed for this file.
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* The following are differences from seq_read():
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@ -93,6 +120,10 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
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err = seq->op->show(seq, p);
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if (err > 0) {
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/* object is skipped, decrease seq_num, so next
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* valid object can reuse the same seq_num.
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*/
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bpf_iter_dec_seq_num(seq);
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seq->count = 0;
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} else if (err < 0 || seq_has_overflowed(seq)) {
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if (!err)
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@ -117,11 +148,15 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
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if (IS_ERR_OR_NULL(p))
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break;
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/* got a valid next object, increase seq_num */
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bpf_iter_inc_seq_num(seq);
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if (seq->count >= size)
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break;
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err = seq->op->show(seq, p);
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if (err > 0) {
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bpf_iter_dec_seq_num(seq);
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seq->count = offs;
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} else if (err < 0 || seq_has_overflowed(seq)) {
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seq->count = offs;
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@ -138,11 +173,15 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
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offs = seq->count;
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/* bpf program called if !p */
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seq->op->stop(seq, p);
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if (!p && seq_has_overflowed(seq)) {
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seq->count = offs;
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if (offs == 0) {
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err = -E2BIG;
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goto done;
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if (!p) {
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if (!seq_has_overflowed(seq)) {
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bpf_iter_done_stop(seq);
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} else {
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seq->count = offs;
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if (offs == 0) {
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err = -E2BIG;
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goto done;
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}
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}
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}
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@ -453,3 +492,39 @@ int bpf_iter_new_fd(struct bpf_link *link)
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put_unused_fd(fd);
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return err;
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}
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struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop)
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{
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struct bpf_iter_priv_data *iter_priv;
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struct seq_file *seq;
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void *seq_priv;
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seq = meta->seq;
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if (seq->file->f_op != &bpf_iter_fops)
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return NULL;
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seq_priv = seq->private;
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iter_priv = container_of(seq_priv, struct bpf_iter_priv_data,
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target_private);
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if (in_stop && iter_priv->done_stop)
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return NULL;
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meta->session_id = iter_priv->session_id;
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meta->seq_num = iter_priv->seq_num;
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return iter_priv->prog;
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}
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int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx)
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{
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int ret;
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rcu_read_lock();
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migrate_disable();
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ret = BPF_PROG_RUN(prog, ctx);
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migrate_enable();
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rcu_read_unlock();
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return ret == 0 ? 0 : -EAGAIN;
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}
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