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bpf: Implement common macros/helpers for target iterators

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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
This commit is contained in:
Yonghong Song 2020-05-09 10:59:07 -07:00 committed by Alexei Starovoitov
parent 367ec3e483
commit e5158d987b
2 changed files with 91 additions and 5 deletions
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11
include/linux/bpf.h
View file

@ -1129,6 +1129,9 @@ int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
int bpf_obj_get_user(const char __user *pathname, int flags);
#define BPF_ITER_FUNC_PREFIX "__bpf_iter__"
#define DEFINE_BPF_ITER_FUNC(target, args...) \
extern int __bpf_iter__ ## target(args); \
int __init __bpf_iter__ ## target(args) { return 0; }
typedef int (*bpf_iter_init_seq_priv_t)(void *private_data);
typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);
@ -1141,12 +1144,20 @@ struct bpf_iter_reg {
u32 seq_priv_size;
};
struct bpf_iter_meta {
__bpf_md_ptr(struct seq_file *, seq);
u64 session_id;
u64 seq_num;
};
int bpf_iter_reg_target(struct bpf_iter_reg *reg_info);
void bpf_iter_unreg_target(const char *target);
bool bpf_iter_prog_supported(struct bpf_prog *prog);
int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
int bpf_iter_new_fd(struct bpf_link *link);
bool bpf_link_is_iter(struct bpf_link *link);
struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop);
int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx);
int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);

85
kernel/bpf/bpf_iter.c
View file

@ -41,6 +41,33 @@ static atomic64_t session_id;
static int prepare_seq_file(struct file *file, struct bpf_iter_link *link);
static void bpf_iter_inc_seq_num(struct seq_file *seq)
{
struct bpf_iter_priv_data *iter_priv;
iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
target_private);
iter_priv->seq_num++;
}
static void bpf_iter_dec_seq_num(struct seq_file *seq)
{
struct bpf_iter_priv_data *iter_priv;
iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
target_private);
iter_priv->seq_num--;
}
static void bpf_iter_done_stop(struct seq_file *seq)
{
struct bpf_iter_priv_data *iter_priv;
iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
target_private);
iter_priv->done_stop = true;
}
/* bpf_seq_read, a customized and simpler version for bpf iterator.
* no_llseek is assumed for this file.
* The following are differences from seq_read():
@ -93,6 +120,10 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
err = seq->op->show(seq, p);
if (err > 0) {
/* object is skipped, decrease seq_num, so next
* valid object can reuse the same seq_num.
*/
bpf_iter_dec_seq_num(seq);
seq->count = 0;
} else if (err < 0 || seq_has_overflowed(seq)) {
if (!err)
@ -117,11 +148,15 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
if (IS_ERR_OR_NULL(p))
break;
/* got a valid next object, increase seq_num */
bpf_iter_inc_seq_num(seq);
if (seq->count >= size)
break;
err = seq->op->show(seq, p);
if (err > 0) {
bpf_iter_dec_seq_num(seq);
seq->count = offs;
} else if (err < 0 || seq_has_overflowed(seq)) {
seq->count = offs;
@ -138,11 +173,15 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
offs = seq->count;
/* bpf program called if !p */
seq->op->stop(seq, p);
if (!p && seq_has_overflowed(seq)) {
seq->count = offs;
if (offs == 0) {
err = -E2BIG;
goto done;
if (!p) {
if (!seq_has_overflowed(seq)) {
bpf_iter_done_stop(seq);
} else {
seq->count = offs;
if (offs == 0) {
err = -E2BIG;
goto done;
}
}
}
@ -453,3 +492,39 @@ int bpf_iter_new_fd(struct bpf_link *link)
put_unused_fd(fd);
return err;
}
struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop)
{
struct bpf_iter_priv_data *iter_priv;
struct seq_file *seq;
void *seq_priv;
seq = meta->seq;
if (seq->file->f_op != &bpf_iter_fops)
return NULL;
seq_priv = seq->private;
iter_priv = container_of(seq_priv, struct bpf_iter_priv_data,
target_private);
if (in_stop && iter_priv->done_stop)
return NULL;
meta->session_id = iter_priv->session_id;
meta->seq_num = iter_priv->seq_num;
return iter_priv->prog;
}
int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx)
{
int ret;
rcu_read_lock();
migrate_disable();
ret = BPF_PROG_RUN(prog, ctx);
migrate_enable();
rcu_read_unlock();
return ret == 0 ? 0 : -EAGAIN;
}