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Merge branch 'file-descriptor-interface-for-bpf-streams'

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Kumar Kartikeya Dwivedi says:

====================
File descriptor interface for BPF streams

BPF program stdout and stderr streams can currently be consumed only
through BPF_PROG_STREAM_READ_BY_FD. This requires repeated bpf() calls and
provides no way to block for output or integrate with poll-based event
loops.

Add BPF_PROG_STREAM_OPEN to return a read-only, close-on-exec descriptor
for a program stream. Reads block by default, with an option for
non-blocking mode. poll and epoll report readable data and report hangup
when the program is freed, while allowing buffered data to be drained
before EOF. Stream descriptors retain the stream storage without retaining
the program itself. Waiters are notified through irq_work only when a
publication turns an empty stream readable, as bpf_ringbuf does, so a
program whose stream nobody drains pays for a single notification.

Expose the command through libbpf and add a -w/--wait option to bpftool
prog tracelog that blocks for new output until the program is unloaded or
bpftool is interrupted. The default dump keeps using
BPF_PROG_STREAM_READ_BY_FD and exits once buffered output is drained, so
existing scripts behave the same on old and new kernels. The legacy
command remains supported.

The first patch fixes a pre-existing issue where empty stream writes
allocate elements that escape capacity accounting; the readiness tracking
added later relies on every element carrying data.

See commit logs for details.

Changelog:
----------
v2 -> v3
v2: https://lore.kernel.org/bpf/20260924162641.1922423-1-memxor@gmail.com

 * Queue the wakeup irq_work only when a publication turns an empty stream
   readable instead of on every write, as bpf_ringbuf does. (Alexei)
 * Make waiting for stream output opt-in through a new bpftool -w/--wait
   option; the default dump keeps using BPF_PROG_STREAM_READ_BY_FD and
   exits as before. (Alexei)
 * Exit from the bpftool signal handlers like the trace pipe command instead
   of checking a stop flag that a signal arriving before read() blocks would
   miss, and drop the disposition save and restore. (Alexei)
 * Fail bpftool --wait with a clear error on kernels without
   BPF_PROG_STREAM_OPEN instead of degrading into a dump.
 * Test that output published after a full drain notifies an edge-triggered
   epoll waiter.
 * Rebase on bpf-next.

v1 -> v2
v1: https://lore.kernel.org/bpf/20260830093514.4105972-1-memxor@gmail.com

 * Fold the irq_work and readable-counter patches into the interface patch
   so no intermediate state wakes waiters directly or derives readiness
   from the capacity counter. (BPF CI)
 * Accept only BPF_F_STREAM_NONBLOCK; BPF_F_RDONLY is no longer accepted
   since the descriptor is always read-only.
 * Allocate streams only for programs loaded through BPF_PROG_LOAD, not for
   classic BPF filters, JIT subprograms or shim programs.
 * Add a patch that skips zero-length stream writes instead of allocating
   elements that bypass capacity accounting. (Emil, Sashiko)
 * Report EOF only when the stream was already dead before it was found
   empty, so data published right before program teardown is not lost.
   (Sashiko)
 * Document that POLLHUP follows program destruction, not the caller's own
   release, and that it may lag the final reference drop.
 * Drop the llseek operation so lseek fails with ESPIPE like other stream
   descriptors. (Emil)
 * Drop the unreachable length check in the file read path; the VFS caps
   read sizes below INT_MAX.
 * Let __bpf_prog_free() clean up after a failed stream allocation instead
   of freeing the streams twice, and drop redundant zeroing of the stream
   counters after kzalloc().
 * Explain why wakeups are always deferred through irq_work and drop the
   batching rationale. (Emil)
 * Skip irq_work_sync() at teardown for streams that never queued a
   notification; on PREEMPT_RT it waits for an RCU grace period that every
   program free, including cBPF filters, would otherwise pay. (Sashiko)
 * Qualify the POLLIN followed by EAGAIN claim to a single reader. (BPF CI)
 * Handle SIGINT, SIGHUP and SIGTERM in bpftool so a followed stream exits
   cleanly, and document the follow behavior. (Emil, BPF CI)
 * Drop bpftool's program reference once the stream is open so following
   ends with EOF when the program is unloaded, and restore the previous
   signal dispositions afterwards for batch mode. (Sashiko)
 * Report bpftool read errors on the fallback path as well.
 * Test lseek rejection and empty stream writes.
 * Retry the NMI test write on a later sample if the first attempt fails.
 * Drop Emil's Reviewed-by from the patches that changed.
 * Rebase on bpf-next.
====================

Link: https://patch.msgid.link/20260925045536.1480933-1-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2026-09-25 21:04:36 +00:00
commit 6ac134ec93
No known key found for this signature in database
16 changed files with 946 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/bpf.h
View File

@ -17,6 +17,7 @@
#include <linux/numa.h>
#include <linux/mm_types.h>
#include <linux/wait.h>
#include <linux/irq_work_types.h>
#include <linux/refcount.h>
#include <linux/mutex.h>
#include <linux/module.h>
@ -1771,12 +1772,18 @@ enum {
};
struct bpf_stream {
atomic_t capacity;
refcount_t refcnt;
atomic_t capacity; /* bytes reserved against the stream limit */
atomic_t readable; /* published bytes available to readers */
struct llist_head log; /* list of in-flight stream elements in LIFO order */
struct mutex lock; /* lock protecting backlog_{head,tail} */
struct llist_node *backlog_head; /* list of in-flight stream elements in FIFO order */
struct llist_node *backlog_tail; /* tail of the list above */
wait_queue_head_t waitq;
struct irq_work notify_work;
bool notify_used; /* notify_work was queued at least once */
bool dead;
};
struct bpf_stream_stage {
@ -1915,7 +1922,7 @@ struct bpf_prog_aux {
struct work_struct work;
struct rcu_head rcu;
};
struct bpf_stream stream[2];
struct bpf_stream *stream[2];
struct mutex st_ops_assoc_mutex;
struct bpf_map __rcu *st_ops_assoc;
};
@ -4224,9 +4231,10 @@ void bpf_bprintf_cleanup(struct bpf_bprintf_data *data);
int bpf_try_get_buffers(struct bpf_bprintf_buffers **bufs);
void bpf_put_buffers(void);
void bpf_prog_stream_init(struct bpf_prog *prog);
int bpf_prog_stream_init(struct bpf_prog *prog, gfp_t gfp_extra_flags);
void bpf_prog_stream_free(struct bpf_prog *prog);
int bpf_prog_stream_read(struct bpf_prog *prog, enum bpf_stream_id stream_id, void __user *buf, u32 len);
int bpf_prog_stream_new_fd(struct bpf_prog *prog, enum bpf_stream_id stream_id, u32 flags);
void bpf_stream_stage_init(struct bpf_stream_stage *ss);
void bpf_stream_stage_free(struct bpf_stream_stage *ss);
__printf(2, 3)

39
include/uapi/linux/bpf.h
View File

@ -936,6 +936,33 @@ union bpf_iter_link_info {
* 0 on success or -1 if an error occurred (in which case,
* *errno* is set appropriately).
*
* BPF_PROG_STREAM_OPEN
* Description
* Open a file descriptor for one of the BPF streams associated
* with the program identified by *prog_fd*. The stream is selected
* by *stream_id*.
*
* The returned file descriptor supports **read**\ (2) and
* **poll**\ (2). Reads block while the stream is empty unless
* **BPF_F_STREAM_NONBLOCK** is specified in *flags*. A non-blocking
* read of an empty stream fails with **EAGAIN**.
*
* **poll**\ (2) reports **POLLIN** when data is available and
* **POLLHUP** once the program has been freed, that is, after every
* reference to it, including links and other file descriptors, has
* been dropped. Hangup may lag the final release because program
* teardown is deferred. Buffered data remains readable after
* **POLLHUP** and a read returns zero after all such data has been
* consumed.
*
* The file descriptor is read-only and has the close-on-exec flag
* set. It is not seekable and **lseek**\ (2) fails with **ESPIPE**.
* *flags* may only contain **BPF_F_STREAM_NONBLOCK**.
*
* Return
* A new file descriptor (a nonnegative integer), or -1 if an
* error occurred (in which case, *errno* is set appropriately).
*
* NOTES
* eBPF objects (maps and programs) can be shared between processes.
*
@ -993,6 +1020,7 @@ enum bpf_cmd {
BPF_TOKEN_CREATE,
BPF_PROG_STREAM_READ_BY_FD,
BPF_PROG_ASSOC_STRUCT_OPS,
BPF_PROG_STREAM_OPEN,
__MAX_BPF_CMD,
BPF_COMMON_ATTRS = 1 << 16, /* Indicate carrying syscall common attrs. */
};
@ -1524,6 +1552,11 @@ enum {
BPF_STREAM_STDERR = 2,
};
/* flags for BPF_PROG_STREAM_OPEN command */
enum {
BPF_F_STREAM_NONBLOCK = (1U << 0),
};
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
__u32 map_type; /* one of enum bpf_map_type */
@ -1950,6 +1983,12 @@ union bpf_attr {
__u32 flags;
} prog_assoc_struct_ops;
struct {
__u32 prog_fd;
__u32 stream_id;
__u32 flags;
} prog_stream_open;
} __attribute__((aligned(8)));
/* The description below is an attempt at providing documentation to eBPF

8
kernel/bpf/core.c
View File

@ -142,10 +142,6 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flag
mutex_init(&fp->aux->dst_mutex);
mutex_init(&fp->aux->st_ops_assoc_mutex);
#ifdef CONFIG_BPF_SYSCALL
bpf_prog_stream_init(fp);
#endif
return fp;
}
@ -289,6 +285,9 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
void __bpf_prog_free(struct bpf_prog *fp)
{
if (fp->aux) {
#ifdef CONFIG_BPF_SYSCALL
bpf_prog_stream_free(fp);
#endif
mutex_destroy(&fp->aux->used_maps_mutex);
mutex_destroy(&fp->aux->dst_mutex);
mutex_destroy(&fp->aux->st_ops_assoc_mutex);
@ -3086,7 +3085,6 @@ static void bpf_prog_free_deferred(struct work_struct *work)
aux = container_of(work, struct bpf_prog_aux, work);
#ifdef CONFIG_BPF_SYSCALL
bpf_free_kfunc_btf_tab(aux->kfunc_btf_tab);
bpf_prog_stream_free(aux->prog);
#endif
#ifdef CONFIG_CGROUP_BPF
if (aux->cgroup_atype != CGROUP_BPF_ATTACH_TYPE_INVALID)

220
kernel/bpf/stream.c
View File

@ -2,11 +2,15 @@
/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
#include <linux/bpf.h>
#include <linux/anon_inodes.h>
#include <linux/filter.h>
#include <linux/bpf_mem_alloc.h>
#include <linux/gfp.h>
#include <linux/irq_work.h>
#include <linux/memory.h>
#include <linux/mutex.h>
#include <linux/poll.h>
#include <linux/refcount.h>
static void bpf_stream_elem_init(struct bpf_stream_elem *elem, int len)
{
@ -73,16 +77,68 @@ static void bpf_stream_release_capacity(struct bpf_stream *stream, int len)
atomic_sub(len, &stream->capacity);
}
static void bpf_stream_notify(struct irq_work *work)
{
struct bpf_stream *stream = container_of(work, struct bpf_stream, notify_work);
/*
* Writers run in arbitrary program contexts, including NMI and regions
* that already hold wait queue or epoll locks. Wake waiters from
* irq_work instead, where taking those locks is safe.
*/
wake_up_interruptible_poll(&stream->waitq, EPOLLIN | EPOLLRDNORM);
}
static void bpf_stream_queue_notify(struct bpf_stream *stream)
{
/*
* Record that the work has been used so that teardown only pays for
* irq_work_sync(), which may wait for an RCU grace period, when a
* callback could actually be in flight.
*/
if (!READ_ONCE(stream->notify_used))
WRITE_ONCE(stream->notify_used, true);
irq_work_queue(&stream->notify_work);
}
static int bpf_stream_readable_bytes(struct bpf_stream *stream)
{
return atomic_read_acquire(&stream->readable);
}
static void bpf_stream_publish(struct bpf_stream *stream, int len)
{
/*
* Pairs with atomic_read_acquire() in bpf_stream_readable_bytes().
*
* Notify only when the stream turns from empty to readable. Readers
* block and pollers wait only after finding it empty, and a read never
* takes the count below zero, so the publication that makes it positive
* is the one they wait for. Publishing into a stream that already holds
* data would only raise an interrupt for waiters that are being woken
* already, or for nobody at all.
*/
if (atomic_add_return_release(len, &stream->readable) == len)
bpf_stream_queue_notify(stream);
}
static int bpf_stream_push_str(struct bpf_stream *stream, const char *str, int len)
{
int ret = bpf_stream_consume_capacity(stream, len);
int ret;
/* Nothing to publish; do not allocate an element for it. */
if (!len)
return 0;
ret = bpf_stream_consume_capacity(stream, len);
if (ret)
return ret;
ret = __bpf_stream_push_str(&stream->log, str, len);
if (ret)
bpf_stream_release_capacity(stream, len);
else
bpf_stream_publish(stream, len);
return ret;
}
@ -91,7 +147,7 @@ static struct bpf_stream *bpf_stream_get(enum bpf_stream_id stream_id, struct bp
{
if (stream_id != BPF_STDOUT && stream_id != BPF_STDERR)
return NULL;
return &aux->stream[stream_id - 1];
return aux->stream[stream_id - 1];
}
static void bpf_stream_free_elem(struct bpf_stream_elem *elem)
@ -159,14 +215,16 @@ static bool bpf_stream_consume_elem(struct bpf_stream_elem *elem, int *len)
static int bpf_stream_read(struct bpf_stream *stream, void __user *buf, int len)
{
int rem_len = len, cons_len, ret = 0;
int read_len, rem_len, cons_len, ret = 0;
struct bpf_stream_elem *elem = NULL;
struct llist_node *node;
mutex_lock(&stream->lock);
read_len = min(len, bpf_stream_readable_bytes(stream));
rem_len = read_len;
while (rem_len) {
int pos = len - rem_len;
int pos = read_len - rem_len;
int chunk, n;
bool cont;
@ -188,7 +246,7 @@ static int bpf_stream_read(struct bpf_stream *stream, void __user *buf, int len)
/* Keep any successfully copied bytes; -EFAULT only if none. */
elem->consumed_len -= n;
rem_len += n;
ret = (len == rem_len) ? -EFAULT : 0;
ret = (read_len == rem_len) ? -EFAULT : 0;
break;
}
@ -199,8 +257,9 @@ static int bpf_stream_read(struct bpf_stream *stream, void __user *buf, int len)
bpf_stream_free_elem(elem);
}
atomic_sub(read_len - rem_len, &stream->readable);
mutex_unlock(&stream->lock);
return ret ? ret : len - rem_len;
return ret ? ret : read_len - rem_len;
}
int bpf_prog_stream_read(struct bpf_prog *prog, enum bpf_stream_id stream_id, void __user *buf, u32 len)
@ -215,6 +274,111 @@ int bpf_prog_stream_read(struct bpf_prog *prog, enum bpf_stream_id stream_id, vo
return bpf_stream_read(stream, buf, len);
}
static bool bpf_stream_has_data(struct bpf_stream *stream)
{
return bpf_stream_readable_bytes(stream) > 0;
}
static void bpf_stream_put(struct bpf_stream *stream)
{
if (refcount_dec_and_test(&stream->refcnt)) {
struct llist_node *list;
/* Only a stream that ever queued its work can have a callback in flight. */
if (READ_ONCE(stream->notify_used))
irq_work_sync(&stream->notify_work);
list = llist_del_all(&stream->log);
bpf_stream_free_list(list);
bpf_stream_free_list(stream->backlog_head);
mutex_destroy(&stream->lock);
kfree(stream);
}
}
static int bpf_stream_release(struct inode *inode, struct file *file)
{
bpf_stream_put(file->private_data);
return 0;
}
static ssize_t bpf_stream_file_read(struct file *file, char __user *buf, size_t len,
loff_t *ppos)
{
struct bpf_stream *stream = file->private_data;
bool dead;
int ret;
if (!len)
return 0;
for (;;) {
/*
* Sample teardown state before looking for data. Nothing is
* published once the program is gone, so finding the stream
* empty after observing dead means EOF. The opposite order could
* report EOF while data published just before teardown is still
* buffered.
*/
dead = smp_load_acquire(&stream->dead);
ret = bpf_stream_read(stream, buf, len);
if (ret)
return ret;
if (dead)
return 0;
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
ret = wait_event_interruptible(stream->waitq,
bpf_stream_has_data(stream) ||
READ_ONCE(stream->dead));
if (ret)
return ret;
}
}
static __poll_t bpf_stream_poll(struct file *file, struct poll_table_struct *pts)
{
struct bpf_stream *stream = file->private_data;
__poll_t events = 0;
/*
* poll_wait() only registers the wait queue callback. Register before
* checking persistent state so a concurrent publication or teardown is
* observed either by the callback or by the checks below.
*/
poll_wait(file, &stream->waitq, pts);
if (bpf_stream_has_data(stream))
events |= EPOLLIN | EPOLLRDNORM;
if (READ_ONCE(stream->dead))
events |= EPOLLHUP;
return events;
}
static const struct file_operations bpf_stream_fops = {
.release = bpf_stream_release,
.read = bpf_stream_file_read,
.poll = bpf_stream_poll,
};
int bpf_prog_stream_new_fd(struct bpf_prog *prog, enum bpf_stream_id stream_id, u32 flags)
{
struct bpf_stream *stream;
int fd_flags = O_RDONLY | O_CLOEXEC;
int fd;
stream = bpf_stream_get(stream_id, prog->aux);
if (!stream)
return -ENOENT;
if (flags & BPF_F_STREAM_NONBLOCK)
fd_flags |= O_NONBLOCK;
refcount_inc(&stream->refcnt);
fd = anon_inode_getfd("bpf-stream", &bpf_stream_fops, stream, fd_flags);
if (fd < 0)
bpf_stream_put(stream);
return fd;
}
__bpf_kfunc_start_defs();
/*
@ -282,28 +446,47 @@ __bpf_kfunc_end_defs();
/* Added kfunc to common_btf_ids */
void bpf_prog_stream_init(struct bpf_prog *prog)
int bpf_prog_stream_init(struct bpf_prog *prog, gfp_t gfp_extra_flags)
{
int i;
for (i = 0; i < ARRAY_SIZE(prog->aux->stream); i++) {
atomic_set(&prog->aux->stream[i].capacity, 0);
init_llist_head(&prog->aux->stream[i].log);
mutex_init(&prog->aux->stream[i].lock);
prog->aux->stream[i].backlog_head = NULL;
prog->aux->stream[i].backlog_tail = NULL;
struct bpf_stream *stream;
/* On failure, bpf_prog_stream_free() releases the streams allocated so far. */
stream = kzalloc_obj(*stream,
bpf_memcg_flags(GFP_KERNEL | gfp_extra_flags));
if (!stream)
return -ENOMEM;
refcount_set(&stream->refcnt, 1);
init_llist_head(&stream->log);
mutex_init(&stream->lock);
init_waitqueue_head(&stream->waitq);
init_irq_work(&stream->notify_work, bpf_stream_notify);
prog->aux->stream[i] = stream;
}
return 0;
}
void bpf_prog_stream_free(struct bpf_prog *prog)
{
struct llist_node *list;
int i;
for (i = 0; i < ARRAY_SIZE(prog->aux->stream); i++) {
list = llist_del_all(&prog->aux->stream[i].log);
bpf_stream_free_list(list);
bpf_stream_free_list(prog->aux->stream[i].backlog_head);
struct bpf_stream *stream = prog->aux->stream[i];
if (!stream)
continue;
/*
* Pairs with smp_load_acquire() in bpf_stream_file_read(): every
* publication precedes the dead flag, so a reader that observes
* it also observes all buffered data.
*/
smp_store_release(&stream->dead, true);
wake_up_interruptible_poll(&stream->waitq, EPOLLHUP);
bpf_stream_put(stream);
prog->aux->stream[i] = NULL;
}
}
@ -333,8 +516,8 @@ int bpf_stream_stage_printk(struct bpf_stream_stage *ss, const char *fmt, ...)
va_start(args, fmt);
len = vscnprintf(buf->buf, ARRAY_SIZE(buf->buf), fmt, args);
va_end(args);
/* Exclude NULL byte during push. */
ret = __bpf_stream_push_str(&ss->log, buf->buf, len);
/* Exclude NULL byte during push; skip empty output entirely. */
ret = len ? __bpf_stream_push_str(&ss->log, buf->buf, len) : 0;
if (!ret)
ss->len += len;
bpf_put_buffers();
@ -366,6 +549,7 @@ int bpf_stream_stage_commit(struct bpf_stream_stage *ss, struct bpf_prog *prog,
list = tail;
}
llist_add_batch(head, tail, &stream->log);
bpf_stream_publish(stream, ss->len);
return 0;
}

29
kernel/bpf/syscall.c
View File

@ -3080,6 +3080,10 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, struct bpf_log_at
prog->aux->user = get_current_user();
prog->len = attr->insn_cnt;
err = bpf_prog_stream_init(prog, GFP_USER);
if (err)
goto free_prog;
err = -EFAULT;
if (copy_from_bpfptr(prog->insns,
make_bpfptr(attr->insns, uattr.is_kernel),
@ -6316,6 +6320,28 @@ static int prog_assoc_struct_ops(union bpf_attr *attr)
return ret;
}
#define BPF_PROG_STREAM_OPEN_LAST_FIELD prog_stream_open.flags
static int prog_stream_open(union bpf_attr *attr)
{
struct bpf_prog *prog;
u32 flags = attr->prog_stream_open.flags;
int ret;
if (CHECK_ATTR(BPF_PROG_STREAM_OPEN))
return -EINVAL;
if (flags & ~BPF_F_STREAM_NONBLOCK)
return -EINVAL;
prog = bpf_prog_get(attr->prog_stream_open.prog_fd);
if (IS_ERR(prog))
return PTR_ERR(prog);
ret = bpf_prog_stream_new_fd(prog, attr->prog_stream_open.stream_id, flags);
bpf_prog_put(prog);
return ret;
}
static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
bpfptr_t uattr_common, unsigned int size_common)
{
@ -6488,6 +6514,9 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
case BPF_PROG_ASSOC_STRUCT_OPS:
err = prog_assoc_struct_ops(&attr);
break;
case BPF_PROG_STREAM_OPEN:
err = prog_stream_open(&attr);
break;
default:
err = -EINVAL;
break;

12
tools/bpf/bpftool/Documentation/bpftool-prog.rst
View File

@ -18,7 +18,8 @@ SYNOPSIS
*OPTIONS* := { |COMMON_OPTIONS| |
{ **-f** | **--bpffs** } | { **-m** | **--mapcompat** } | { **-n** | **--nomount** } |
{ **-L** | **--use-loader** } | [ { **-S** | **--sign** } **-k** <private_key.pem> **-i** <certificate.x509> ] }
{ **-L** | **--use-loader** } | [ { **-S** | **--sign** } **-k** <private_key.pem> **-i** <certificate.x509> ] |
{ **-w** | **--wait** } }
*COMMANDS* :=
{ **show** | **list** | **dump xlated** | **dump jited** | **pin** | **load** |
@ -186,6 +187,11 @@ bpftool prog tracelog { stdout | stderr } *PROG*
error messages to the standard error stream. This facility should be used
only for debugging purposes.
By default, bpftool prints the output buffered so far and exits. With
**-w** or **--wait**, it keeps printing new output as the program produces
it, until the program is unloaded or <Ctrl+C> is hit. Waiting requires a
kernel that supports opening a stream as a file descriptor.
bpftool prog run *PROG* data_in *FILE* [data_out *FILE* [data_size_out *L*]] [ctx_in *FILE* [ctx_out *FILE* [ctx_size_out *M*]]] [repeat *N*]
Run BPF program *PROG* in the kernel testing infrastructure for BPF,
meaning that the program works on the data and context provided by the
@ -267,6 +273,10 @@ OPTIONS
Path to the X.509 certificate file in PEM or DER format, required when
signing.
-w, --wait
When dumping a program stream with **bpftool prog tracelog**, wait for new
output instead of exiting once the buffered output has been printed.
EXAMPLES
========
**# bpftool prog show**

2
tools/bpf/bpftool/bash-completion/bpftool
View File

@ -269,7 +269,7 @@ _bpftool()
# Deal with options
if [[ ${words[cword]} == -* ]]; then
local c='--version --json --pretty --bpffs --mapcompat --debug \
--use-loader --base-btf --sign -i -k'
--use-loader --base-btf --sign -i -k --wait'
COMPREPLY=( $( compgen -W "$c" -- "$cur" ) )
return 0
fi

7
tools/bpf/bpftool/main.c
View File

@ -31,6 +31,7 @@ bool block_mount;
bool verifier_logs;
bool relaxed_maps;
bool use_loader;
bool wait_output;
struct btf *base_btf;
struct hashmap *refs_table;
bool sign_progs;
@ -462,6 +463,7 @@ int main(int argc, char **argv)
{ "nomount", no_argument, NULL, 'n' },
{ "debug", no_argument, NULL, 'd' },
{ "use-loader", no_argument, NULL, 'L' },
{ "wait", no_argument, NULL, 'w' },
{ "sign", no_argument, NULL, 'S' },
{ "base-btf", required_argument, NULL, 'B' },
{ 0 }
@ -480,7 +482,7 @@ int main(int argc, char **argv)
bin_name = "bpftool";
opterr = 0;
while ((opt = getopt_long(argc, argv, "VhpjfLmndSi:k:B:l",
while ((opt = getopt_long(argc, argv, "VhpjfLmndSi:k:B:lw",
options, NULL)) >= 0) {
switch (opt) {
case 'V':
@ -530,6 +532,9 @@ int main(int argc, char **argv)
case 'L':
use_loader = true;
break;
case 'w':
wait_output = true;
break;
case 'S':
sign_progs = true;
use_loader = true;

1
tools/bpf/bpftool/main.h
View File

@ -89,6 +89,7 @@ extern bool block_mount;
extern bool verifier_logs;
extern bool relaxed_maps;
extern bool use_loader;
extern bool wait_output;
extern struct btf *base_btf;
extern struct hashmap *refs_table;
extern bool sign_progs;

62
tools/bpf/bpftool/prog.c
View File

@ -1119,21 +1119,66 @@ enum prog_tracelog_mode {
TRACE_STDERR,
};
static void exit_stream(int signo)
{
exit(0);
}
/* Consumes prog_fd. */
static int
prog_tracelog_stream(int prog_fd, enum prog_tracelog_mode mode)
{
const struct sigaction act = { .sa_handler = exit_stream };
const int signals[] = { SIGHUP, SIGINT, SIGTERM };
FILE *file = mode == TRACE_STDOUT ? stdout : stderr;
int stream_id = mode == TRACE_STDOUT ? 1 : 2;
char buf[512];
int ret;
unsigned int i;
int fd, ret;
ret = 0;
do {
ret = bpf_prog_stream_read(prog_fd, stream_id, buf, sizeof(buf), NULL);
if (ret > 0)
fwrite(buf, sizeof(buf[0]), ret, file);
} while (ret > 0);
if (!wait_output) {
do {
ret = bpf_prog_stream_read(prog_fd, stream_id, buf, sizeof(buf), NULL);
if (ret > 0)
fwrite(buf, sizeof(buf[0]), ret, file);
} while (ret > 0);
if (ret < 0)
p_err("failed to read stream: %s", strerror(-ret));
close(prog_fd);
goto out;
}
fd = bpf_prog_stream_open(prog_fd, stream_id, NULL);
/*
* The stream descriptor does not keep the program alive. Drop the
* program reference so that reads return EOF once the program is gone.
*/
close(prog_fd);
if (fd == -EINVAL) {
/* The bpf() syscall rejects unknown commands with EINVAL. */
p_err("waiting for stream output is not supported by this kernel");
return -1;
}
if (fd < 0) {
p_err("failed to open stream: %s", strerror(-fd));
return -1;
}
/*
* Exit from the handler like the trace pipe variant does. A flag checked
* between reads would miss a signal that lands before read() blocks and
* only end the loop at the next print.
*/
for (i = 0; i < ARRAY_SIZE(signals); i++)
sigaction(signals[i], &act, NULL);
while ((ret = read(fd, buf, sizeof(buf))) > 0) {
fwrite(buf, sizeof(buf[0]), ret, file);
fflush(file);
}
if (ret < 0)
p_err("failed to read stream: %s", strerror(errno));
close(fd);
out:
fflush(file);
return ret ? -1 : 0;
}
@ -2659,7 +2704,8 @@ static int do_help(int argc, char **argv)
" METRIC := { cycles | instructions | l1d_loads | llc_misses | itlb_misses | dtlb_misses }\n"
" " HELP_SPEC_OPTIONS " |\n"
" {-f|--bpffs} | {-m|--mapcompat} | {-n|--nomount} |\n"
" {-L|--use-loader} | [ {-S|--sign } {-k} <private_key.pem> {-i} <certificate.x509> ] \n"
" {-L|--use-loader} | [ {-S|--sign } {-k} <private_key.pem> {-i} <certificate.x509> ] |\n"
" {-w|--wait} }\n"
"",
bin_name, argv[-2]);

39
tools/include/uapi/linux/bpf.h
View File

@ -936,6 +936,33 @@ union bpf_iter_link_info {
* 0 on success or -1 if an error occurred (in which case,
* *errno* is set appropriately).
*
* BPF_PROG_STREAM_OPEN
* Description
* Open a file descriptor for one of the BPF streams associated
* with the program identified by *prog_fd*. The stream is selected
* by *stream_id*.
*
* The returned file descriptor supports **read**\ (2) and
* **poll**\ (2). Reads block while the stream is empty unless
* **BPF_F_STREAM_NONBLOCK** is specified in *flags*. A non-blocking
* read of an empty stream fails with **EAGAIN**.
*
* **poll**\ (2) reports **POLLIN** when data is available and
* **POLLHUP** once the program has been freed, that is, after every
* reference to it, including links and other file descriptors, has
* been dropped. Hangup may lag the final release because program
* teardown is deferred. Buffered data remains readable after
* **POLLHUP** and a read returns zero after all such data has been
* consumed.
*
* The file descriptor is read-only and has the close-on-exec flag
* set. It is not seekable and **lseek**\ (2) fails with **ESPIPE**.
* *flags* may only contain **BPF_F_STREAM_NONBLOCK**.
*
* Return
* A new file descriptor (a nonnegative integer), or -1 if an
* error occurred (in which case, *errno* is set appropriately).
*
* NOTES
* eBPF objects (maps and programs) can be shared between processes.
*
@ -993,6 +1020,7 @@ enum bpf_cmd {
BPF_TOKEN_CREATE,
BPF_PROG_STREAM_READ_BY_FD,
BPF_PROG_ASSOC_STRUCT_OPS,
BPF_PROG_STREAM_OPEN,
__MAX_BPF_CMD,
BPF_COMMON_ATTRS = 1 << 16, /* Indicate carrying syscall common attrs. */
};
@ -1524,6 +1552,11 @@ enum {
BPF_STREAM_STDERR = 2,
};
/* flags for BPF_PROG_STREAM_OPEN command */
enum {
BPF_F_STREAM_NONBLOCK = (1U << 0),
};
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
__u32 map_type; /* one of enum bpf_map_type */
@ -1950,6 +1983,12 @@ union bpf_attr {
__u32 flags;
} prog_assoc_struct_ops;
struct {
__u32 prog_fd;
__u32 stream_id;
__u32 flags;
} prog_stream_open;
} __attribute__((aligned(8)));
/* The description below is an attempt at providing documentation to eBPF

19
tools/lib/bpf/bpf.c
View File

@ -1466,6 +1466,25 @@ int bpf_prog_stream_read(int prog_fd, __u32 stream_id, void *buf, __u32 buf_len,
return libbpf_err_errno(err);
}
int bpf_prog_stream_open(int prog_fd, __u32 stream_id,
const struct bpf_prog_stream_open_opts *opts)
{
const size_t attr_sz = offsetofend(union bpf_attr, prog_stream_open);
union bpf_attr attr;
int fd;
if (!OPTS_VALID(opts, bpf_prog_stream_open_opts))
return libbpf_err(-EINVAL);
memset(&attr, 0, attr_sz);
attr.prog_stream_open.prog_fd = prog_fd;
attr.prog_stream_open.stream_id = stream_id;
attr.prog_stream_open.flags = OPTS_GET(opts, flags, 0);
fd = sys_bpf_fd(BPF_PROG_STREAM_OPEN, &attr, attr_sz);
return libbpf_err_errno(fd);
}
int bpf_prog_assoc_struct_ops(int prog_fd, int map_fd,
struct bpf_prog_assoc_struct_ops_opts *opts)
{

24
tools/lib/bpf/bpf.h
View File

@ -759,10 +759,34 @@ struct bpf_prog_stream_read_opts {
*
* @return The number of bytes read, on success; negative error code, otherwise
* (errno is also set to the error code)
*
* For blocking reads and polling, prefer **bpf_prog_stream_open**.
*/
LIBBPF_API int bpf_prog_stream_read(int prog_fd, __u32 stream_id, void *buf, __u32 buf_len,
struct bpf_prog_stream_read_opts *opts);
struct bpf_prog_stream_open_opts {
size_t sz;
__u32 flags;
size_t :0;
};
#define bpf_prog_stream_open_opts__last_field flags
/**
* @brief **bpf_prog_stream_open** opens a file descriptor for a BPF stream of
* a given BPF program.
*
* @param prog_fd FD for the BPF program whose BPF stream is to be opened.
* @param stream_id ID of the BPF stream to be opened.
* @param opts optional options, can be NULL. BPF_F_STREAM_NONBLOCK requests a
* non-blocking descriptor.
*
* @return A new stream FD, on success; negative error code, otherwise (errno
* is also set to the error code)
*/
LIBBPF_API int bpf_prog_stream_open(int prog_fd, __u32 stream_id,
const struct bpf_prog_stream_open_opts *opts);
struct bpf_prog_assoc_struct_ops_opts {
size_t sz;
__u32 flags;

1
tools/lib/bpf/libbpf.map
View File

@ -459,6 +459,7 @@ LIBBPF_1.7.0 {
LIBBPF_1.8.0 {
global:
bpf_map__attach_cgroup_opts;
bpf_prog_stream_open;
bpf_program__add_flags;
bpf_program__attach_tracing_multi;
bpf_program__clear_flags;

486
tools/testing/selftests/bpf/prog_tests/stream.c
View File

@ -1,11 +1,17 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
#include <test_progs.h>
#include <linux/perf_event.h>
#include <poll.h>
#include <sys/epoll.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include "stream.skel.h"
#include "stream_fail.skel.h"
#define NMI_TIMEOUT_NS (5ULL * 1000 * 1000 * 1000)
void test_stream_failure(void)
{
RUN_TESTS(stream_fail);
@ -62,6 +68,486 @@ void test_stream_syscall(void)
stream__destroy(skel);
}
static bool stream_fd_trigger(struct bpf_program *prog)
{
LIBBPF_OPTS(bpf_test_run_opts, opts);
int ret;
ret = bpf_prog_test_run_opts(bpf_program__fd(prog), &opts);
return ASSERT_OK(ret, "test_run") && ASSERT_OK(opts.retval, "retval");
}
static void test_stream_fd_open(void)
{
LIBBPF_OPTS(bpf_prog_stream_open_opts, opts);
struct stream *skel;
int fd, prog_fd;
skel = stream__open_and_load();
if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
return;
prog_fd = bpf_program__fd(skel->progs.stream_syscall);
fd = bpf_prog_stream_open(0, BPF_STREAM_STDOUT, NULL);
ASSERT_EQ(fd, -EINVAL, "bad_prog_fd");
fd = bpf_prog_stream_open(prog_fd, 0, NULL);
ASSERT_EQ(fd, -ENOENT, "bad_stream_id");
opts.flags = BPF_F_RDONLY;
fd = bpf_prog_stream_open(prog_fd, BPF_STREAM_STDOUT, &opts);
ASSERT_EQ(fd, -EINVAL, "access_flag");
opts.flags = 1U << 31;
fd = bpf_prog_stream_open(prog_fd, BPF_STREAM_STDOUT, &opts);
ASSERT_EQ(fd, -EINVAL, "unknown_flag");
fd = bpf_prog_stream_open(prog_fd, BPF_STREAM_STDERR, NULL);
if (ASSERT_OK_FD(fd, "stderr"))
close(fd);
stream__destroy(skel);
}
static void test_stream_fd_nonblock(void)
{
LIBBPF_OPTS(bpf_prog_stream_open_opts, opts,
.flags = BPF_F_STREAM_NONBLOCK,
);
struct pollfd pfd = { .events = POLLIN | POLLHUP };
struct stream *skel;
char buf[4] = {};
int fd, flags, ret;
skel = stream__open_and_load();
if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
return;
fd = bpf_prog_stream_open(bpf_program__fd(skel->progs.stream_syscall),
BPF_STREAM_STDOUT, &opts);
if (!ASSERT_OK_FD(fd, "stream_open"))
goto out_destroy;
pfd.fd = fd;
flags = fcntl(fd, F_GETFD);
ASSERT_GE(flags, 0, "getfd");
ASSERT_NEQ(flags & FD_CLOEXEC, 0, "cloexec");
flags = fcntl(fd, F_GETFL);
ASSERT_GE(flags, 0, "getfl");
ASSERT_EQ(flags & O_ACCMODE, O_RDONLY, "readonly");
ASSERT_NEQ(flags & O_NONBLOCK, 0, "nonblock");
ret = write(fd, "x", 1);
ASSERT_EQ(ret, -1, "write");
ASSERT_EQ(errno, EBADF, "write_errno");
ret = lseek(fd, 0, SEEK_SET);
ASSERT_EQ(ret, -1, "lseek");
ASSERT_EQ(errno, ESPIPE, "lseek_errno");
ret = poll(&pfd, 1, 0);
ASSERT_EQ(ret, 0, "poll_empty");
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, -1, "read_empty");
ASSERT_EQ(errno, EAGAIN, "read_empty_errno");
if (!stream_fd_trigger(skel->progs.stream_syscall))
goto out_close;
ret = poll(&pfd, 1, 0);
ASSERT_EQ(ret, 1, "poll_data");
ASSERT_NEQ(pfd.revents & POLLIN, 0, "pollin");
ASSERT_EQ(pfd.revents & POLLHUP, 0, "no_pollhup");
ret = read(fd, buf, 2);
ASSERT_EQ(ret, 2, "read_first");
ASSERT_OK(memcmp(buf, "fo", 2), "read_first_data");
pfd.revents = 0;
ret = poll(&pfd, 1, 0);
ASSERT_EQ(ret, 1, "poll_partial");
ASSERT_NEQ(pfd.revents & POLLIN, 0, "pollin_partial");
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, 1, "read_rest");
ASSERT_EQ(buf[0], 'o', "read_rest_data");
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, -1, "read_drained");
ASSERT_EQ(errno, EAGAIN, "read_drained_errno");
out_close:
close(fd);
out_destroy:
stream__destroy(skel);
}
static void test_stream_fd_empty(void)
{
LIBBPF_OPTS(bpf_prog_stream_open_opts, opts,
.flags = BPF_F_STREAM_NONBLOCK,
);
struct pollfd pfd = { .events = POLLIN | POLLHUP };
struct stream *skel;
char buf[4];
int fd, ret;
skel = stream__open_and_load();
if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
return;
fd = bpf_prog_stream_open(bpf_program__fd(skel->progs.stream_empty),
BPF_STREAM_STDOUT, &opts);
if (!ASSERT_OK_FD(fd, "stream_open"))
goto out_destroy;
pfd.fd = fd;
/* Empty output produces neither data nor readiness. */
if (!stream_fd_trigger(skel->progs.stream_empty))
goto out_close;
ret = poll(&pfd, 1, 0);
ASSERT_EQ(ret, 0, "poll_empty_write");
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, -1, "read_empty_write");
ASSERT_EQ(errno, EAGAIN, "read_empty_write_errno");
out_close:
close(fd);
out_destroy:
stream__destroy(skel);
}
struct stream_fd_read_ctx {
int fd;
ssize_t ret;
char buf[4];
};
static void *stream_fd_read_thread(void *arg)
{
struct stream_fd_read_ctx *ctx = arg;
ctx->ret = read(ctx->fd, ctx->buf, sizeof(ctx->buf));
return NULL;
}
static int stream_fd_timed_join(pthread_t thread)
{
struct timespec timeout;
clock_gettime(CLOCK_REALTIME, &timeout);
timeout.tv_sec += 5;
return pthread_timedjoin_np(thread, NULL, &timeout);
}
static void test_stream_fd_blocking(void)
{
struct stream_fd_read_ctx ctx = {};
struct stream *skel;
pthread_t thread;
bool thread_live = false;
int fd, flags, ret;
skel = stream__open_and_load();
if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
return;
fd = bpf_prog_stream_open(bpf_program__fd(skel->progs.stream_syscall),
BPF_STREAM_STDOUT, NULL);
if (!ASSERT_OK_FD(fd, "stream_open"))
goto out_destroy;
ctx.fd = fd;
flags = fcntl(fd, F_GETFL);
ASSERT_GE(flags, 0, "getfl");
ASSERT_EQ(flags & O_NONBLOCK, 0, "blocking");
ret = pthread_create(&thread, NULL, stream_fd_read_thread, &ctx);
if (!ASSERT_OK(ret, "pthread_create"))
goto out_close;
thread_live = true;
usleep(50000);
ret = pthread_tryjoin_np(thread, NULL);
if (!ASSERT_EQ(ret, EBUSY, "read_blocks")) {
thread_live = ret != 0;
goto out_thread;
}
if (!stream_fd_trigger(skel->progs.stream_syscall))
goto out_thread;
ret = stream_fd_timed_join(thread);
if (!ASSERT_OK(ret, "pthread_join"))
goto out_thread;
thread_live = false;
ASSERT_EQ(ctx.ret, 3, "read_len");
ASSERT_OK(memcmp(ctx.buf, "foo", 3), "read_data");
memset(&ctx, 0, sizeof(ctx));
ctx.fd = fd;
ret = pthread_create(&thread, NULL, stream_fd_read_thread, &ctx);
if (!ASSERT_OK(ret, "pthread_create_eof"))
goto out_close;
thread_live = true;
usleep(50000);
ret = pthread_tryjoin_np(thread, NULL);
if (!ASSERT_EQ(ret, EBUSY, "read_eof_blocks")) {
thread_live = ret != 0;
goto out_thread;
}
stream__destroy(skel);
skel = NULL;
ret = stream_fd_timed_join(thread);
if (!ASSERT_OK(ret, "pthread_join_eof"))
goto out_thread;
thread_live = false;
ASSERT_EQ(ctx.ret, 0, "read_eof");
out_thread:
if (thread_live) {
stream__destroy(skel);
skel = NULL;
ret = stream_fd_timed_join(thread);
if (ret) {
pthread_cancel(thread);
pthread_join(thread, NULL);
}
}
out_close:
close(fd);
out_destroy:
stream__destroy(skel);
}
static void test_stream_fd_hup(void)
{
LIBBPF_OPTS(bpf_prog_stream_open_opts, opts,
.flags = BPF_F_STREAM_NONBLOCK,
);
struct epoll_event event = {
.events = EPOLLIN | EPOLLET,
};
struct pollfd pfd = { .events = POLLIN | POLLHUP };
struct stream *skel;
char buf[4] = {};
int epfd = -1, fd, ret;
skel = stream__open_and_load();
if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
return;
fd = bpf_prog_stream_open(bpf_program__fd(skel->progs.stream_syscall),
BPF_STREAM_STDOUT, &opts);
if (!ASSERT_OK_FD(fd, "stream_open"))
goto out_destroy;
pfd.fd = fd;
epfd = epoll_create1(EPOLL_CLOEXEC);
if (!ASSERT_OK_FD(epfd, "epoll_create"))
goto out_close;
event.data.fd = fd;
ret = epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &event);
if (!ASSERT_OK(ret, "epoll_ctl"))
goto out_close;
if (!stream_fd_trigger(skel->progs.stream_syscall))
goto out_close;
ret = epoll_wait(epfd, &event, 1, 5000);
if (!ASSERT_EQ(ret, 1, "epoll_wait_data"))
goto out_close;
ASSERT_NEQ(event.events & EPOLLIN, 0, "epollin");
ASSERT_EQ(event.events & EPOLLHUP, 0, "no_epollhup");
stream__destroy(skel);
skel = NULL;
event.events = 0;
ret = epoll_wait(epfd, &event, 1, 5000);
if (!ASSERT_EQ(ret, 1, "epoll_wait_hup"))
goto out_close;
ASSERT_NEQ(event.events & EPOLLIN, 0, "epollin_with_hup");
ASSERT_NEQ(event.events & EPOLLHUP, 0, "epollhup");
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, 3, "read_buffered");
ASSERT_OK(memcmp(buf, "foo", 3), "read_buffered_data");
pfd.revents = 0;
ret = poll(&pfd, 1, 0);
ASSERT_EQ(ret, 1, "poll_drained_hup");
ASSERT_EQ(pfd.revents & POLLIN, 0, "no_pollin_after_drain");
ASSERT_NEQ(pfd.revents & POLLHUP, 0, "pollhup_after_drain");
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, 0, "read_eof");
out_close:
if (epfd >= 0)
close(epfd);
close(fd);
out_destroy:
stream__destroy(skel);
}
static void test_stream_fd_edge(void)
{
LIBBPF_OPTS(bpf_prog_stream_open_opts, opts,
.flags = BPF_F_STREAM_NONBLOCK,
);
struct epoll_event event = {
.events = EPOLLIN | EPOLLET,
};
struct stream *skel;
char buf[8] = {};
int epfd = -1, fd, ret;
skel = stream__open_and_load();
if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
return;
fd = bpf_prog_stream_open(bpf_program__fd(skel->progs.stream_syscall),
BPF_STREAM_STDOUT, &opts);
if (!ASSERT_OK_FD(fd, "stream_open"))
goto out_destroy;
epfd = epoll_create1(EPOLL_CLOEXEC);
if (!ASSERT_OK_FD(epfd, "epoll_create"))
goto out_close;
event.data.fd = fd;
ret = epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &event);
if (!ASSERT_OK(ret, "epoll_ctl"))
goto out_close;
/* Output into an empty stream raises an edge. */
if (!stream_fd_trigger(skel->progs.stream_syscall))
goto out_close;
ret = epoll_wait(epfd, &event, 1, 5000);
if (!ASSERT_EQ(ret, 1, "epoll_wait_first"))
goto out_close;
ASSERT_NEQ(event.events & EPOLLIN, 0, "epollin_first");
/*
* Leave data behind, add more, then drain everything. Whether output
* into a non-empty stream raises an edge of its own is not part of the
* contract, so discard any pending event before re-arming the stream.
*/
ret = read(fd, buf, 2);
ASSERT_EQ(ret, 2, "read_partial");
if (!stream_fd_trigger(skel->progs.stream_syscall))
goto out_close;
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, 4, "read_rest");
ASSERT_OK(memcmp(buf, "ofoo", 4), "read_rest_data");
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, -1, "read_drained");
ASSERT_EQ(errno, EAGAIN, "read_drained_errno");
epoll_wait(epfd, &event, 1, 0);
/* Output into the drained stream raises an edge again. */
if (!stream_fd_trigger(skel->progs.stream_syscall))
goto out_close;
ret = epoll_wait(epfd, &event, 1, 5000);
if (!ASSERT_EQ(ret, 1, "epoll_wait_after_drain"))
goto out_close;
ASSERT_NEQ(event.events & EPOLLIN, 0, "epollin_after_drain");
out_close:
if (epfd >= 0)
close(epfd);
close(fd);
out_destroy:
stream__destroy(skel);
}
static void test_stream_fd_nmi_epoll(void)
{
LIBBPF_OPTS(bpf_prog_stream_open_opts, opts,
.flags = BPF_F_STREAM_NONBLOCK,
);
struct perf_event_attr attr = {
.size = sizeof(attr),
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_CPU_CYCLES,
.freq = 1,
.sample_freq = 10,
};
struct epoll_event event = {
.events = EPOLLIN,
};
struct bpf_link *link = NULL;
struct stream *skel;
__u64 deadline;
char buf[4] = {};
int epfd = -1, fd = -1, pmu_fd = -1;
int ret;
skel = stream__open_and_load();
if (!ASSERT_OK_PTR(skel, "stream__open_and_load"))
return;
fd = bpf_prog_stream_open(bpf_program__fd(skel->progs.stream_nmi),
BPF_STREAM_STDOUT, &opts);
if (!ASSERT_OK_FD(fd, "stream_open"))
goto out;
epfd = epoll_create1(EPOLL_CLOEXEC);
if (!ASSERT_OK_FD(epfd, "epoll_create"))
goto out;
event.data.fd = fd;
ret = epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &event);
if (!ASSERT_OK(ret, "epoll_ctl"))
goto out;
pmu_fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1,
PERF_FLAG_FD_CLOEXEC);
if (pmu_fd < 0 && (errno == ENOENT || errno == EOPNOTSUPP)) {
printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n", __func__);
test__skip();
goto out;
}
if (!ASSERT_GE(pmu_fd, 0, "perf_event_open"))
goto out;
link = bpf_program__attach_perf_event(skel->progs.stream_nmi, pmu_fd);
if (!ASSERT_OK_PTR(link, "attach_perf_event")) {
link = NULL;
goto out;
}
pmu_fd = -1;
deadline = get_time_ns() + NMI_TIMEOUT_NS;
do {
ret = epoll_wait(epfd, &event, 1, 0);
} while (ret == 0 && get_time_ns() < deadline);
if (!ASSERT_EQ(ret, 1, "epoll_wait"))
goto out;
ASSERT_NEQ(event.events & EPOLLIN, 0, "epollin");
ret = read(fd, buf, sizeof(buf));
ASSERT_EQ(ret, 3, "read_len");
ASSERT_OK(memcmp(buf, "nmi", 3), "read_data");
out:
bpf_link__destroy(link);
if (pmu_fd >= 0)
close(pmu_fd);
if (epfd >= 0)
close(epfd);
if (fd >= 0)
close(fd);
stream__destroy(skel);
}
void test_stream_fd(void)
{
if (test__start_subtest("open"))
test_stream_fd_open();
if (test__start_subtest("nonblock"))
test_stream_fd_nonblock();
if (test__start_subtest("empty"))
test_stream_fd_empty();
if (test__start_subtest("blocking"))
test_stream_fd_blocking();
if (test__start_subtest("hup"))
test_stream_fd_hup();
if (test__start_subtest("edge"))
test_stream_fd_edge();
if (test__start_subtest("nmi_epoll"))
test_stream_fd_nmi_epoll();
}
void test_stream_oversize(void)
{
LIBBPF_OPTS(bpf_test_run_opts, opts);

20
tools/testing/selftests/bpf/progs/stream.c
View File

@ -44,6 +44,7 @@ struct {
_X64 _X64 _X64 _X64 _X64 _X64 _X64 _X64)
int size;
int nmi_stream_prints;
u64 fault_addr;
void *arena_ptr;
@ -124,6 +125,25 @@ int stream_syscall(void *ctx)
return 0;
}
SEC("syscall")
__success __retval(0)
int stream_empty(void *ctx)
{
return bpf_stream_printk(BPF_STDOUT, "");
}
SEC("perf_event")
int stream_nmi(void *ctx)
{
if (nmi_stream_prints)
return 0;
/* Retry on a later sample if the write failed, e.g. with -EBUSY. */
if (bpf_stream_printk(BPF_STDOUT, "nmi"))
return 0;
nmi_stream_prints = 1;
return 0;
}
SEC("syscall")
__success __retval(0)
int stream_oversize(void *ctx)