// 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>
#include <linux/btf_ids.h>
#include "mmap_unlock_work.h"
static const char * const iter_task_type_names[] = {
"ALL",
"TID",
"PID",
};
struct bpf_iter_seq_task_common {
struct pid_namespace *ns;
enum bpf_iter_task_type type;
u32 pid;
u32 pid_visiting;
};
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_group_seq_get_next(struct bpf_iter_seq_task_common *common,
u32 *tid,
bool skip_if_dup_files)
{
struct task_struct *task, *next_task;
struct pid *pid;
u32 saved_tid;
if (!*tid) {
/* The first time, the iterator calls this function. */
pid = find_pid_ns(common->pid, common->ns);
if (!pid)
return NULL;
task = get_pid_task(pid, PIDTYPE_TGID);
if (!task)
return NULL;
*tid = common->pid;
common->pid_visiting = common->pid;
return task;
}
/* If the control returns to user space and comes back to the
* kernel again, *tid and common->pid_visiting should be the
* same for task_seq_start() to pick up the correct task.
*/
if (*tid == common->pid_visiting) {
pid = find_pid_ns(common->pid_visiting, common->ns);
task = get_pid_task(pid, PIDTYPE_PID);
return task;
}
pid = find_pid_ns(common->pid_visiting, common->ns);
if (!pid)
return NULL;
task = get_pid_task(pid, PIDTYPE_PID);
if (!task)
return NULL;
retry:
if (!pid_alive(task)) {
put_task_struct(task);
return NULL;
}
next_task = next_thread(task);
put_task_struct(task);
if (!next_task)
return NULL;
saved_tid = *tid;
*tid = __task_pid_nr_ns(next_task, PIDTYPE_PID, common->ns);
if (!*tid || *tid == common->pid) {
/* Run out of tasks of a process. The tasks of a
* thread_group are linked as circular linked list.
*/
*tid = saved_tid;
return NULL;
}
get_task_struct(next_task);
common->pid_visiting = *tid;
if (skip_if_dup_files && task->files == task->group_leader->files) {
task = next_task;
goto retry;
}
return next_task;
}
static struct task_struct *task_seq_get_next(struct bpf_iter_seq_task_common *common,
u32 *tid,
bool skip_if_dup_files)
{
struct task_struct *task = NULL;
struct pid *pid;
if (common->type == BPF_TASK_ITER_TID) {
if (*tid && *tid != common->pid)
return NULL;
rcu_read_lock();
pid = find_pid_ns(common->pid, common->ns);
if (pid) {
task = get_pid_task(pid, PIDTYPE_TGID);
*tid = common->pid;
}
rcu_read_unlock();
return task;
}
if (common->type == BPF_TASK_ITER_TGID) {
rcu_read_lock();
task = task_group_seq_get_next(common, tid, skip_if_dup_files);
rcu_read_unlock();
return task;
}
rcu_read_lock();
retry:
pid = find_ge_pid(*tid, common->ns);
if (pid) {
*tid = pid_nr_ns(pid, common->ns);
task = get_pid_task(pid, PIDTYPE_PID);
if (!task) {
++*tid;
goto retry;
} else if (skip_if_dup_files && !thread_group_leader(task) &&
task->files == task->group_leader->files) {
put_task_struct(task);
task = NULL;
++*tid;
goto retry;
}
}
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, &info->tid, false);
if (!task)
return NULL;
if (*pos == 0)
++*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, &info->tid, false);
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;
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 int bpf_iter_attach_task(struct bpf_prog *prog,
union bpf_iter_link_info *linfo,
struct bpf_iter_aux_info *aux)
{
unsigned int flags;
struct pid *pid;
pid_t tgid;
if ((!!linfo->task.tid + !!linfo->task.pid + !!linfo->task.pid_fd) > 1)
return -EINVAL;
aux->task.type = BPF_TASK_ITER_ALL;
if (linfo->task.tid != 0) {
aux->task.type = BPF_TASK_ITER_TID;
aux->task.pid = linfo->task.tid;
}
if (linfo->task.pid != 0) {
aux->task.type = BPF_TASK_ITER_TGID;
aux->task.pid = linfo->task.pid;
}
if (linfo->task.pid_fd != 0) {
aux->task.type = BPF_TASK_ITER_TGID;
pid = pidfd_get_pid(linfo->task.pid_fd, &flags);
if (IS_ERR(pid))
return PTR_ERR(pid);
tgid = pid_nr_ns(pid, task_active_pid_ns(current));
aux->task.pid = tgid;
put_pid(pid);
}
return 0;
}
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;
u32 tid;
u32 fd;
};
static struct file *
task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info)
{
u32 saved_tid = info->tid;
struct task_struct *curr_task;
unsigned int curr_fd = info->fd;
/* If this function returns a non-NULL file object,
* it held a reference to the task/file.
* Otherwise, it does not hold any reference.
*/
again:
if (info->task) {
curr_task = info->task;
curr_fd = info->fd;
} else {
curr_task = task_seq_get_next(&info->common, &info->tid, true);
if (!curr_task) {
info->task = NULL;
return NULL;
}
/* set info->task */
info->task = curr_task;
if (saved_tid == info->tid)
curr_fd = info->fd;
else
curr_fd = 0;
}
rcu_read_lock();
for (;; curr_fd++) {
struct file *f;
f = task_lookup_next_fd_rcu(curr_task, &curr_fd);
if (!f)
break;
if (!get_file_rcu(f))
continue;
/* set info->fd */
info->fd = curr_fd;
rcu_read_unlock();
return f;
}
/* the current task is done, go to the next task */
rcu_read_unlock();
put_task_struct(curr_task);
if (info->common.type == BPF_TASK_ITER_TID) {
info->task = NULL;
return NULL;
}
info->task = NULL;
info->fd = 0;
saved_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 file *file;
info->task = NULL;
file = task_file_seq_get_next(info);
if (file && *pos == 0)
++*pos;
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;
++*pos;
++info->fd;
fput((struct file *)v);
return task_file_seq_get_next(info);
}
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_task_struct(info->task);
info->task = NULL;
}
}
static int init_seq_pidns(void *priv_data, struct bpf_iter_aux_info *aux)
{
struct bpf_iter_seq_task_common *common = priv_data;
common->ns = get_pid_ns(task_active_pid_ns(current));
common->type = aux->task.type;
common->pid = aux->task.pid;
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,
};
struct bpf_iter_seq_task_vma_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 mm_struct *mm;
struct vm_area_struct *vma;
u32 tid;
unsigned long prev_vm_start;
unsigned long prev_vm_end;
};
enum bpf_task_vma_iter_find_op {
task_vma_iter_first_vma, /* use find_vma() with addr 0 */
task_vma_iter_next_vma, /* use vma_next() with curr_vma */
task_vma_iter_find_vma, /* use find_vma() to find next vma */
};
static struct vm_area_struct *
task_vma_seq_get_next(struct bpf_iter_seq_task_vma_info *info)
{
enum bpf_task_vma_iter_find_op op;
struct vm_area_struct *curr_vma;
struct task_struct *curr_task;
struct mm_struct *curr_mm;
u32 saved_tid = info->tid;
/* If this function returns a non-NULL vma, it holds a reference to
* the task_struct, holds a refcount on mm->mm_users, and holds
* read lock on vma->mm->mmap_lock.
* If this function returns NULL, it does not hold any reference or
* lock.
*/
if (info->task) {
curr_task = info->task;
curr_vma = info->vma;
curr_mm = info->mm;
/* In case of lock contention, drop mmap_lock to unblock
* the writer.
*
* After relock, call find(mm, prev_vm_end - 1) to find
* new vma to process.
*
* +------+------+-----------+
* | VMA1 | VMA2 | VMA3 |
* +------+------+-----------+
* | | | |
* 4k 8k 16k 400k
*
* For example, curr_vma == VMA2. Before unlock, we set
*
* prev_vm_start = 8k
* prev_vm_end = 16k
*
* There are a few cases:
*
* 1) VMA2 is freed, but VMA3 exists.
*
* find_vma() will return VMA3, just process VMA3.
*
* 2) VMA2 still exists.
*
* find_vma() will return VMA2, process VMA2->next.
*
* 3) no more vma in this mm.
*
* Process the next task.
*
* 4) find_vma() returns a different vma, VMA2'.
*
* 4.1) If VMA2 covers same range as VMA2', skip VMA2',
* because we already covered the range;
* 4.2) VMA2 and VMA2' covers different ranges, process
* VMA2'.
*/
if (mmap_lock_is_contended(curr_mm)) {
info->prev_vm_start = curr_vma->vm_start;
info->prev_vm_end = curr_vma->vm_end;
op = task_vma_iter_find_vma;
mmap_read_unlock(curr_mm);
if (mmap_read_lock_killable(curr_mm)) {
mmput(curr_mm);
goto finish;
}
} else {
op = task_vma_iter_next_vma;
}
} else {
again:
curr_task = task_seq_get_next(&info->common, &info->tid, true);
if (!curr_task) {
info->tid++;
goto finish;
}
if (saved_tid != info->tid) {
/* new task, process the first vma */
op = task_vma_iter_first_vma;
} else {
/* Found the same tid, which means the user space
* finished data in previous buffer and read more.
* We dropped mmap_lock before returning to user
* space, so it is necessary to use find_vma() to
* find the next vma to process.
*/
op = task_vma_iter_find_vma;
}
curr_mm = get_task_mm(curr_task);
if (!curr_mm)
goto next_task;
if (mmap_read_lock_killable(curr_mm)) {
mmput(curr_mm);
goto finish;
}
}
switch (op) {
case task_vma_iter_first_vma:
curr_vma = find_vma(curr_mm, 0);
break;
case task_vma_iter_next_vma:
curr_vma = find_vma(curr_mm, curr_vma->vm_end);
break;
case task_vma_iter_find_vma:
/* We dropped mmap_lock so it is necessary to use find_vma
* to find the next vma. This is similar to the mechanism
* in show_smaps_rollup().
*/
curr_vma = find_vma(curr_mm, info->prev_vm_end - 1);
/* case 1) and 4.2) above just use curr_vma */
/* check for case 2) or case 4.1) above */
if (curr_vma &&
curr_vma->vm_start == info->prev_vm_start &&
curr_vma->vm_end == info->prev_vm_end)
curr_vma = find_vma(curr_mm, curr_vma->vm_end);
break;
}
if (!curr_vma) {
/* case 3) above, or case 2) 4.1) with vma->next == NULL */
mmap_read_unlock(curr_mm);
mmput(curr_mm);
goto next_task;
}
info->task = curr_task;
info->vma = curr_vma;
info->mm = curr_mm;
return curr_vma;
next_task:
if (info->common.type == BPF_TASK_ITER_TID)
goto finish;
put_task_struct(curr_task);
info->task = NULL;
info->mm = NULL;
info->tid++;
goto again;
finish:
if (curr_task)
put_task_struct(curr_task);
info->task = NULL;
info->vma = NULL;
info->mm = NULL;
return NULL;
}
static void *task_vma_seq_start(struct seq_file *seq, loff_t *pos)
{
struct bpf_iter_seq_task_vma_info *info = seq->private;
struct vm_area_struct *vma;
vma = task_vma_seq_get_next(info);
if (vma && *pos == 0)
++*pos;
return vma;
}
static void *task_vma_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
struct bpf_iter_seq_task_vma_info *info = seq->private;
++*pos;
return task_vma_seq_get_next(info);
}
struct bpf_iter__task_vma {
__bpf_md_ptr(struct bpf_iter_meta *, meta);
__bpf_md_ptr(struct task_struct *, task);
__bpf_md_ptr(struct vm_area_struct *, vma);
};
DEFINE_BPF_ITER_FUNC(task_vma, struct bpf_iter_meta *meta,
struct task_struct *task, struct vm_area_struct *vma)
static int __task_vma_seq_show(struct seq_file *seq, bool in_stop)
{
struct bpf_iter_seq_task_vma_info *info = seq->private;
struct bpf_iter__task_vma 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.vma = info->vma;
return bpf_iter_run_prog(prog, &ctx);
}
static int task_vma_seq_show(struct seq_file *seq, void *v)
{
return __task_vma_seq_show(seq, false);
}
static void task_vma_seq_stop(struct seq_file *seq, void *v)
{
struct bpf_iter_seq_task_vma_info *info = seq->private;
if (!v) {
(void)__task_vma_seq_show(seq, true);
} else {
/* info->vma has not been seen by the BPF program. If the
* user space reads more, task_vma_seq_get_next should
* return this vma again. Set prev_vm_start to ~0UL,
* so that we don't skip the vma returned by the next
* find_vma() (case task_vma_iter_find_vma in
* task_vma_seq_get_next()).
*/
info->prev_vm_start = ~0UL;
info->prev_vm_end = info->vma->vm_end;
mmap_read_unlock(info->mm);
mmput(info->mm);
info->mm = NULL;
put_task_struct(info->task);
info->task = NULL;
}
}
static const struct seq_operations task_vma_seq_ops = {
.start = task_vma_seq_start,
.next = task_vma_seq_next,
.stop = task_vma_seq_stop,
.show = task_vma_seq_show,
};
static const struct bpf_iter_seq_info task_seq_info = {
.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),
};
static int bpf_iter_fill_link_info(const struct bpf_iter_aux_info *aux, struct bpf_link_info *info)
{
switch (aux->task.type) {
case BPF_TASK_ITER_TID:
info->iter.task.tid = aux->task.pid;
break;
case BPF_TASK_ITER_TGID:
info->iter.task.pid = aux->task.pid;
break;
default:
break;
}
return 0;
}
static void bpf_iter_task_show_fdinfo(const struct bpf_iter_aux_info *aux, struct seq_file *seq)
{
seq_printf(seq, "task_type:\t%s\n", iter_task_type_names[aux->task.type]);
if (aux->task.type == BPF_TASK_ITER_TID)
seq_printf(seq, "tid:\t%u\n", aux->task.pid);
else if (aux->task.type == BPF_TASK_ITER_TGID)
seq_printf(seq, "pid:\t%u\n", aux->task.pid);
}
static struct bpf_iter_reg task_reg_info = {
.target = "task",
.attach_target = bpf_iter_attach_task,
.feature = BPF_ITER_RESCHED,
.ctx_arg_info_size = 1,
.ctx_arg_info = {
{ offsetof(struct bpf_iter__task, task),
PTR_TO_BTF_ID_OR_NULL },
},
.seq_info = &task_seq_info,
.fill_link_info = bpf_iter_fill_link_info,
.show_fdinfo = bpf_iter_task_show_fdinfo,
};
static const struct bpf_iter_seq_info task_file_seq_info = {
.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),
};
static struct bpf_iter_reg task_file_reg_info = {
.target = "task_file",
.attach_target = bpf_iter_attach_task,
.feature = BPF_ITER_RESCHED,
.ctx_arg_info_size = 2,
.ctx_arg_info = {
{ offsetof(struct bpf_iter__task_file, task),
PTR_TO_BTF_ID_OR_NULL },
{ offsetof(struct bpf_iter__task_file, file),
PTR_TO_BTF_ID_OR_NULL },
},
.seq_info = &task_file_seq_info,
.fill_link_info = bpf_iter_fill_link_info,
.show_fdinfo = bpf_iter_task_show_fdinfo,
};
static const struct bpf_iter_seq_info task_vma_seq_info = {
.seq_ops = &task_vma_seq_ops,
.init_seq_private = init_seq_pidns,
.fini_seq_private = fini_seq_pidns,
.seq_priv_size = sizeof(struct bpf_iter_seq_task_vma_info),
};
static struct bpf_iter_reg task_vma_reg_info = {
.target = "task_vma",
.attach_target = bpf_iter_attach_task,
.feature = BPF_ITER_RESCHED,
.ctx_arg_info_size = 2,
.ctx_arg_info = {
{ offsetof(struct bpf_iter__task_vma, task),
PTR_TO_BTF_ID_OR_NULL },
{ offsetof(struct bpf_iter__task_vma, vma),
PTR_TO_BTF_ID_OR_NULL },
},
.seq_info = &task_vma_seq_info,
.fill_link_info = bpf_iter_fill_link_info,
.show_fdinfo = bpf_iter_task_show_fdinfo,
};
BPF_CALL_5(bpf_find_vma, struct task_struct *, task, u64, start,
bpf_callback_t, callback_fn, void *, callback_ctx, u64, flags)
{
struct mmap_unlock_irq_work *work = NULL;
struct vm_area_struct *vma;
bool irq_work_busy = false;
struct mm_struct *mm;
int ret = -ENOENT;
if (flags)
return -EINVAL;
if (!task)
return -ENOENT;
mm = task->mm;
if (!mm)
return -ENOENT;
irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
if (irq_work_busy || !mmap_read_trylock(mm))
return -EBUSY;
vma = find_vma(mm, start);
if (vma && vma->vm_start <= start && vma->vm_end > start) {
callback_fn((u64)(long)task, (u64)(long)vma,
(u64)(long)callback_ctx, 0, 0);
ret = 0;
}
bpf_mmap_unlock_mm(work, mm);
return ret;
}
const struct bpf_func_proto bpf_find_vma_proto = {
.func = bpf_find_vma,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_BTF_ID,
.arg1_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
.arg2_type = ARG_ANYTHING,
.arg3_type = ARG_PTR_TO_FUNC,
.arg4_type = ARG_PTR_TO_STACK_OR_NULL,
.arg5_type = ARG_ANYTHING,
};
DEFINE_PER_CPU(struct mmap_unlock_irq_work, mmap_unlock_work);
static void do_mmap_read_unlock(struct irq_work *entry)
{
struct mmap_unlock_irq_work *work;
if (WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT)))
return;
work = container_of(entry, struct mmap_unlock_irq_work, irq_work);
mmap_read_unlock_non_owner(work->mm);
}
static int __init task_iter_init(void)
{
struct mmap_unlock_irq_work *work;
int ret, cpu;
for_each_possible_cpu(cpu) {
work = per_cpu_ptr(&mmap_unlock_work, cpu);
init_irq_work(&work->irq_work, do_mmap_read_unlock);
}
task_reg_info.ctx_arg_info[0].btf_id = btf_tracing_ids[BTF_TRACING_TYPE_TASK];
ret = bpf_iter_reg_target(&task_reg_info);
if (ret)
return ret;
task_file_reg_info.ctx_arg_info[0].btf_id = btf_tracing_ids[BTF_TRACING_TYPE_TASK];
task_file_reg_info.ctx_arg_info[1].btf_id = btf_tracing_ids[BTF_TRACING_TYPE_FILE];
ret = bpf_iter_reg_target(&task_file_reg_info);
if (ret)
return ret;
task_vma_reg_info.ctx_arg_info[0].btf_id = btf_tracing_ids[BTF_TRACING_TYPE_TASK];
task_vma_reg_info.ctx_arg_info[1].btf_id = btf_tracing_ids[BTF_TRACING_TYPE_VMA];
return bpf_iter_reg_target(&task_vma_reg_info);
}
late_initcall(task_iter_init);
