Commit eaaacd23 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov

bpf: Add task and task/file iterator targets

Only the tasks belonging to "current" pid namespace
are enumerated.

For task/file target, the bpf program will have access to
  struct task_struct *task
  u32 fd
  struct file *file
where fd/file is an open file for the task.
Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175911.2476407-1-yhs@fb.com
parent 138d0be3
...@@ -2,7 +2,7 @@ ...@@ -2,7 +2,7 @@
obj-y := core.o obj-y := core.o
CFLAGS_core.o += $(call cc-disable-warning, override-init) CFLAGS_core.o += $(call cc-disable-warning, override-init)
obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o
obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o
obj-$(CONFIG_BPF_SYSCALL) += disasm.o obj-$(CONFIG_BPF_SYSCALL) += disasm.o
......
// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2020 Facebook */
#include <linux/init.h>
#include <linux/namei.h>
#include <linux/pid_namespace.h>
#include <linux/fs.h>
#include <linux/fdtable.h>
#include <linux/filter.h>
struct bpf_iter_seq_task_common {
struct pid_namespace *ns;
};
struct bpf_iter_seq_task_info {
/* The first field must be struct bpf_iter_seq_task_common.
* this is assumed by {init, fini}_seq_pidns() callback functions.
*/
struct bpf_iter_seq_task_common common;
u32 tid;
};
static struct task_struct *task_seq_get_next(struct pid_namespace *ns,
u32 *tid)
{
struct task_struct *task = NULL;
struct pid *pid;
rcu_read_lock();
pid = idr_get_next(&ns->idr, tid);
if (pid)
task = get_pid_task(pid, PIDTYPE_PID);
rcu_read_unlock();
return task;
}
static void *task_seq_start(struct seq_file *seq, loff_t *pos)
{
struct bpf_iter_seq_task_info *info = seq->private;
struct task_struct *task;
task = task_seq_get_next(info->common.ns, &info->tid);
if (!task)
return NULL;
++*pos;
return task;
}
static void *task_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
struct bpf_iter_seq_task_info *info = seq->private;
struct task_struct *task;
++*pos;
++info->tid;
put_task_struct((struct task_struct *)v);
task = task_seq_get_next(info->common.ns, &info->tid);
if (!task)
return NULL;
return task;
}
struct bpf_iter__task {
__bpf_md_ptr(struct bpf_iter_meta *, meta);
__bpf_md_ptr(struct task_struct *, task);
};
DEFINE_BPF_ITER_FUNC(task, struct bpf_iter_meta *meta, struct task_struct *task)
static int __task_seq_show(struct seq_file *seq, struct task_struct *task,
bool in_stop)
{
struct bpf_iter_meta meta;
struct bpf_iter__task ctx;
struct bpf_prog *prog;
meta.seq = seq;
prog = bpf_iter_get_info(&meta, in_stop);
if (!prog)
return 0;
meta.seq = seq;
ctx.meta = &meta;
ctx.task = task;
return bpf_iter_run_prog(prog, &ctx);
}
static int task_seq_show(struct seq_file *seq, void *v)
{
return __task_seq_show(seq, v, false);
}
static void task_seq_stop(struct seq_file *seq, void *v)
{
if (!v)
(void)__task_seq_show(seq, v, true);
else
put_task_struct((struct task_struct *)v);
}
static const struct seq_operations task_seq_ops = {
.start = task_seq_start,
.next = task_seq_next,
.stop = task_seq_stop,
.show = task_seq_show,
};
struct bpf_iter_seq_task_file_info {
/* The first field must be struct bpf_iter_seq_task_common.
* this is assumed by {init, fini}_seq_pidns() callback functions.
*/
struct bpf_iter_seq_task_common common;
struct task_struct *task;
struct files_struct *files;
u32 tid;
u32 fd;
};
static struct file *
task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info,
struct task_struct **task, struct files_struct **fstruct)
{
struct pid_namespace *ns = info->common.ns;
u32 curr_tid = info->tid, max_fds;
struct files_struct *curr_files;
struct task_struct *curr_task;
int curr_fd = info->fd;
/* If this function returns a non-NULL file object,
* it held a reference to the task/files_struct/file.
* Otherwise, it does not hold any reference.
*/
again:
if (*task) {
curr_task = *task;
curr_files = *fstruct;
curr_fd = info->fd;
} else {
curr_task = task_seq_get_next(ns, &curr_tid);
if (!curr_task)
return NULL;
curr_files = get_files_struct(curr_task);
if (!curr_files) {
put_task_struct(curr_task);
curr_tid = ++(info->tid);
info->fd = 0;
goto again;
}
/* set *fstruct, *task and info->tid */
*fstruct = curr_files;
*task = curr_task;
if (curr_tid == info->tid) {
curr_fd = info->fd;
} else {
info->tid = curr_tid;
curr_fd = 0;
}
}
rcu_read_lock();
max_fds = files_fdtable(curr_files)->max_fds;
for (; curr_fd < max_fds; curr_fd++) {
struct file *f;
f = fcheck_files(curr_files, curr_fd);
if (!f)
continue;
/* set info->fd */
info->fd = curr_fd;
get_file(f);
rcu_read_unlock();
return f;
}
/* the current task is done, go to the next task */
rcu_read_unlock();
put_files_struct(curr_files);
put_task_struct(curr_task);
*task = NULL;
*fstruct = NULL;
info->fd = 0;
curr_tid = ++(info->tid);
goto again;
}
static void *task_file_seq_start(struct seq_file *seq, loff_t *pos)
{
struct bpf_iter_seq_task_file_info *info = seq->private;
struct files_struct *files = NULL;
struct task_struct *task = NULL;
struct file *file;
file = task_file_seq_get_next(info, &task, &files);
if (!file) {
info->files = NULL;
info->task = NULL;
return NULL;
}
++*pos;
info->task = task;
info->files = files;
return file;
}
static void *task_file_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
struct bpf_iter_seq_task_file_info *info = seq->private;
struct files_struct *files = info->files;
struct task_struct *task = info->task;
struct file *file;
++*pos;
++info->fd;
fput((struct file *)v);
file = task_file_seq_get_next(info, &task, &files);
if (!file) {
info->files = NULL;
info->task = NULL;
return NULL;
}
info->task = task;
info->files = files;
return file;
}
struct bpf_iter__task_file {
__bpf_md_ptr(struct bpf_iter_meta *, meta);
__bpf_md_ptr(struct task_struct *, task);
u32 fd __aligned(8);
__bpf_md_ptr(struct file *, file);
};
DEFINE_BPF_ITER_FUNC(task_file, struct bpf_iter_meta *meta,
struct task_struct *task, u32 fd,
struct file *file)
static int __task_file_seq_show(struct seq_file *seq, struct file *file,
bool in_stop)
{
struct bpf_iter_seq_task_file_info *info = seq->private;
struct bpf_iter__task_file ctx;
struct bpf_iter_meta meta;
struct bpf_prog *prog;
meta.seq = seq;
prog = bpf_iter_get_info(&meta, in_stop);
if (!prog)
return 0;
ctx.meta = &meta;
ctx.task = info->task;
ctx.fd = info->fd;
ctx.file = file;
return bpf_iter_run_prog(prog, &ctx);
}
static int task_file_seq_show(struct seq_file *seq, void *v)
{
return __task_file_seq_show(seq, v, false);
}
static void task_file_seq_stop(struct seq_file *seq, void *v)
{
struct bpf_iter_seq_task_file_info *info = seq->private;
if (!v) {
(void)__task_file_seq_show(seq, v, true);
} else {
fput((struct file *)v);
put_files_struct(info->files);
put_task_struct(info->task);
info->files = NULL;
info->task = NULL;
}
}
static int init_seq_pidns(void *priv_data)
{
struct bpf_iter_seq_task_common *common = priv_data;
common->ns = get_pid_ns(task_active_pid_ns(current));
return 0;
}
static void fini_seq_pidns(void *priv_data)
{
struct bpf_iter_seq_task_common *common = priv_data;
put_pid_ns(common->ns);
}
static const struct seq_operations task_file_seq_ops = {
.start = task_file_seq_start,
.next = task_file_seq_next,
.stop = task_file_seq_stop,
.show = task_file_seq_show,
};
static int __init task_iter_init(void)
{
struct bpf_iter_reg task_file_reg_info = {
.target = "task_file",
.seq_ops = &task_file_seq_ops,
.init_seq_private = init_seq_pidns,
.fini_seq_private = fini_seq_pidns,
.seq_priv_size = sizeof(struct bpf_iter_seq_task_file_info),
};
struct bpf_iter_reg task_reg_info = {
.target = "task",
.seq_ops = &task_seq_ops,
.init_seq_private = init_seq_pidns,
.fini_seq_private = fini_seq_pidns,
.seq_priv_size = sizeof(struct bpf_iter_seq_task_info),
};
int ret;
ret = bpf_iter_reg_target(&task_reg_info);
if (ret)
return ret;
return bpf_iter_reg_target(&task_file_reg_info);
}
late_initcall(task_iter_init);
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