linux/kernel/bpf/syscall.c, branch v6.17

bpf: Move bpf map owner out of common struct

2025-07-31T18:30:05Z

Given this is only relevant for BPF tail call maps, it is adding up space and penalizing other map types. We also need to extend this with further objects to track / compare to. Therefore, lets move this out into a separate structure and dynamically allocate it only for BPF tail call maps. Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/r/20250730234733.530041-2-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov

bpf: Add cookie object to bpf maps

2025-07-31T18:30:05Z

Add a cookie to BPF maps to uniquely identify BPF maps for the timespan when the node is up. This is different to comparing a pointer or BPF map id which could get rolled over and reused. Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/r/20250730234733.530041-1-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov

bpf: Add struct bpf_token_info

2025-07-17T01:38:05Z

The 'commit 35f96de04127 ("bpf: Introduce BPF token object")' added BPF token as a new kind of BPF kernel object. And BPF_OBJ_GET_INFO_BY_FD already used to get BPF object info, so we can also get token info with this cmd. One usage scenario, when program runs failed with token, because of the permission failure, we can report what BPF token is allowing with this API for debugging. Acked-by: Andrii Nakryiko Signed-off-by: Tao Chen Link: https://lore.kernel.org/r/20250716134654.1162635-1-chen.dylane@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Remove attach_type in bpf_tracing_link

2025-07-11T18:01:08Z

Use attach_type in bpf_link, and remove it in bpf_tracing_link. Signed-off-by: Tao Chen Signed-off-by: Andrii Nakryiko Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/20250710032038.888700-7-chen.dylane@linux.dev

bpf: Add attach_type field to bpf_link

2025-07-11T17:51:55Z

Attach_type will be set when a link is created by user. It is better to record attach_type in bpf_link generically and have it available universally for all link types. So add the attach_type field in bpf_link and move the sleepable field to avoid unnecessary gap padding. Signed-off-by: Tao Chen Signed-off-by: Andrii Nakryiko Acked-by: Daniel Borkmann Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/20250710032038.888700-2-chen.dylane@linux.dev

bpf: Clean code with bpf_copy_to_user()

2025-07-07T15:53:59Z

No logic change, use bpf_copy_to_user() to clean code. Signed-off-by: Tao Chen Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20250703163700.677628-1-chen.dylane@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Introduce BPF standard streams

2025-07-04T02:30:06Z

Add support for a stream API to the kernel and expose related kfuncs to BPF programs. Two streams are exposed, BPF_STDOUT and BPF_STDERR. These can be used for printing messages that can be consumed from user space, thus it's similar in spirit to existing trace_pipe interface. The kernel will use the BPF_STDERR stream to notify the program of any errors encountered at runtime. BPF programs themselves may use both streams for writing debug messages. BPF library-like code may use BPF_STDERR to print warnings or errors on misuse at runtime. The implementation of a stream is as follows. Everytime a message is emitted from the kernel (directly, or through a BPF program), a record is allocated by bump allocating from per-cpu region backed by a page obtained using alloc_pages_nolock(). This ensures that we can allocate memory from any context. The eventual plan is to discard this scheme in favor of Alexei's kmalloc_nolock() [0]. This record is then locklessly inserted into a list (llist_add()) so that the printing side doesn't require holding any locks, and works in any context. Each stream has a maximum capacity of 4MB of text, and each printed message is accounted against this limit. Messages from a program are emitted using the bpf_stream_vprintk kfunc, which takes a stream_id argument in addition to working otherwise similar to bpf_trace_vprintk. The bprintf buffer helpers are extracted out to be reused for printing the string into them before copying it into the stream, so that we can (with the defined max limit) format a string and know its true length before performing allocations of the stream element. For consuming elements from a stream, we expose a bpf(2) syscall command named BPF_PROG_STREAM_READ_BY_FD, which allows reading data from the stream of a given prog_fd into a user space buffer. The main logic is implemented in bpf_stream_read(). The log messages are queued in bpf_stream::log by the bpf_stream_vprintk kfunc, and then pulled and ordered correctly in the stream backlog. For this purpose, we hold a lock around bpf_stream_backlog_peek(), as llist_del_first() (if we maintained a second lockless list for the backlog) wouldn't be safe from multiple threads anyway. Then, if we fail to find something in the backlog log, we splice out everything from the lockless log, and place it in the backlog log, and then return the head of the backlog. Once the full length of the element is consumed, we will pop it and free it. The lockless list bpf_stream::log is a LIFO stack. Elements obtained using a llist_del_all() operation are in LIFO order, thus would break the chronological ordering if printed directly. Hence, this batch of messages is first reversed. Then, it is stashed into a separate list in the stream, i.e. the backlog_log. The head of this list is the actual message that should always be returned to the caller. All of this is done in bpf_stream_backlog_fill(). From the kernel side, the writing into the stream will be a bit more involved than the typical printk. First, the kernel typically may print a collection of messages into the stream, and parallel writers into the stream may suffer from interleaving of messages. To ensure each group of messages is visible atomically, we can lift the advantage of using a lockless list for pushing in messages. To enable this, we add a bpf_stream_stage() macro, and require kernel users to use bpf_stream_printk statements for the passed expression to write into the stream. Underneath the macro, we have a message staging API, where a bpf_stream_stage object on the stack accumulates the messages being printed into a local llist_head, and then a commit operation splices the whole batch into the stream's lockless log list. This is especially pertinent for rqspinlock deadlock messages printed to program streams. After this change, we see each deadlock invocation as a non-interleaving contiguous message without any confusion on the reader's part, improving their user experience in debugging the fault. While programs cannot benefit from this staged stream writing API, they could just as well hold an rqspinlock around their print statements to serialize messages, hence this is kept kernel-internal for now. Overall, this infrastructure provides NMI-safe any context printing of messages to two dedicated streams. Later patches will add support for printing splats in case of BPF arena page faults, rqspinlock deadlocks, and cond_break timeouts, and integration of this facility into bpftool for dumping messages to user space. [0]: https://lore.kernel.org/bpf/20250501032718.65476-1-alexei.starovoitov@gmail.com Reviewed-by: Eduard Zingerman Reviewed-by: Emil Tsalapatis Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20250703204818.925464-3-memxor@gmail.com Signed-off-by: Alexei Starovoitov

bpf: Show precise link_type for {uprobe,kprobe}_multi fdinfo

2025-07-04T02:29:42Z

Alexei suggested, 'link_type' can be more precise and differentiate for human in fdinfo. In fact BPF_LINK_TYPE_KPROBE_MULTI includes kretprobe_multi type, the same as BPF_LINK_TYPE_UPROBE_MULTI, so we can show it more concretely. link_type: kprobe_multi link_id: 1 prog_tag: d2b307e915f0dd37 ... link_type: kretprobe_multi link_id: 2 prog_tag: ab9ea0545870781d ... link_type: uprobe_multi link_id: 9 prog_tag: e729f789e34a8eca ... link_type: uretprobe_multi link_id: 10 prog_tag: 7db356c03e61a4d4 Co-developed-by: Jiri Olsa Signed-off-by: Jiri Olsa Signed-off-by: Tao Chen Link: https://lore.kernel.org/r/20250702153958.639852-1-chen.dylane@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Add cookie in fdinfo for raw_tp

2025-06-09T23:45:17Z

Add cookie in fdinfo for raw_tp, the info as follows: link_type: raw_tracepoint link_id: 31 prog_tag: 9dfdf8ef453843bf prog_id: 32 tp_name: sys_enter cookie: 23925373020405760 Signed-off-by: Tao Chen Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20250606165818.3394397-5-chen.dylane@linux.dev

bpf: Add cookie in fdinfo for tracing

2025-06-09T23:45:17Z

Add cookie in fdinfo for tracing, the info as follows: link_type: tracing link_id: 6 prog_tag: 9dfdf8ef453843bf prog_id: 35 attach_type: 25 target_obj_id: 1 target_btf_id: 60355 cookie: 9007199254740992 Signed-off-by: Tao Chen Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20250606165818.3394397-4-chen.dylane@linux.dev