bpf: Implement BPF ring buffer and verifier support for it

This commit adds a new MPSC ring buffer implementation into BPF ecosystem,
which allows multiple CPUs to submit data to a single shared ring buffer. On
the consumption side, only single consumer is assumed.

Motivation
----------
There are two distinctive motivators for this work, which are not satisfied by
existing perf buffer, which prompted creation of a new ring buffer
implementation.
  - more efficient memory utilization by sharing ring buffer across CPUs;
  - preserving ordering of events that happen sequentially in time, even
  across multiple CPUs (e.g., fork/exec/exit events for a task).

These two problems are independent, but perf buffer fails to satisfy both.
Both are a result of a choice to have per-CPU perf ring buffer.  Both can be
also solved by having an MPSC implementation of ring buffer. The ordering
problem could technically be solved for perf buffer with some in-kernel
counting, but given the first one requires an MPSC buffer, the same solution
would solve the second problem automatically.

Semantics and APIs
------------------
Single ring buffer is presented to BPF programs as an instance of BPF map of
type BPF_MAP_TYPE_RINGBUF. Two other alternatives considered, but ultimately
rejected.

One way would be to, similar to BPF_MAP_TYPE_PERF_EVENT_ARRAY, make
BPF_MAP_TYPE_RINGBUF could represent an array of ring buffers, but not enforce
"same CPU only" rule. This would be more familiar interface compatible with
existing perf buffer use in BPF, but would fail if application needed more
advanced logic to lookup ring buffer by arbitrary key. HASH_OF_MAPS addresses
this with current approach. Additionally, given the performance of BPF
ringbuf, many use cases would just opt into a simple single ring buffer shared
among all CPUs, for which current approach would be an overkill.

Another approach could introduce a new concept, alongside BPF map, to
represent generic "container" object, which doesn't necessarily have key/value
interface with lookup/update/delete operations. This approach would add a lot
of extra infrastructure that has to be built for observability and verifier
support. It would also add another concept that BPF developers would have to
familiarize themselves with, new syntax in libbpf, etc. But then would really
provide no additional benefits over the approach of using a map.
BPF_MAP_TYPE_RINGBUF doesn't support lookup/update/delete operations, but so
doesn't few other map types (e.g., queue and stack; array doesn't support
delete, etc).

The approach chosen has an advantage of re-using existing BPF map
infrastructure (introspection APIs in kernel, libbpf support, etc), being
familiar concept (no need to teach users a new type of object in BPF program),
and utilizing existing tooling (bpftool). For common scenario of using
a single ring buffer for all CPUs, it's as simple and straightforward, as
would be with a dedicated "container" object. On the other hand, by being
a map, it can be combined with ARRAY_OF_MAPS and HASH_OF_MAPS map-in-maps to
implement a wide variety of topologies, from one ring buffer for each CPU
(e.g., as a replacement for perf buffer use cases), to a complicated
application hashing/sharding of ring buffers (e.g., having a small pool of
ring buffers with hashed task's tgid being a look up key to preserve order,
but reduce contention).

Key and value sizes are enforced to be zero. max_entries is used to specify
the size of ring buffer and has to be a power of 2 value.

There are a bunch of similarities between perf buffer
(BPF_MAP_TYPE_PERF_EVENT_ARRAY) and new BPF ring buffer semantics:
  - variable-length records;
  - if there is no more space left in ring buffer, reservation fails, no
    blocking;
  - memory-mappable data area for user-space applications for ease of
    consumption and high performance;
  - epoll notifications for new incoming data;
  - but still the ability to do busy polling for new data to achieve the
    lowest latency, if necessary.

BPF ringbuf provides two sets of APIs to BPF programs:
  - bpf_ringbuf_output() allows to *copy* data from one place to a ring
    buffer, similarly to bpf_perf_event_output();
  - bpf_ringbuf_reserve()/bpf_ringbuf_commit()/bpf_ringbuf_discard() APIs
    split the whole process into two steps. First, a fixed amount of space is
    reserved. If successful, a pointer to a data inside ring buffer data area
    is returned, which BPF programs can use similarly to a data inside
    array/hash maps. Once ready, this piece of memory is either committed or
    discarded. Discard is similar to commit, but makes consumer ignore the
    record.

bpf_ringbuf_output() has disadvantage of incurring extra memory copy, because
record has to be prepared in some other place first. But it allows to submit
records of the length that's not known to verifier beforehand. It also closely
matches bpf_perf_event_output(), so will simplify migration significantly.

bpf_ringbuf_reserve() avoids the extra copy of memory by providing a memory
pointer directly to ring buffer memory. In a lot of cases records are larger
than BPF stack space allows, so many programs have use extra per-CPU array as
a temporary heap for preparing sample. bpf_ringbuf_reserve() avoid this needs
completely. But in exchange, it only allows a known constant size of memory to
be reserved, such that verifier can verify that BPF program can't access
memory outside its reserved record space. bpf_ringbuf_output(), while slightly
slower due to extra memory copy, covers some use cases that are not suitable
for bpf_ringbuf_reserve().

The difference between commit and discard is very small. Discard just marks
a record as discarded, and such records are supposed to be ignored by consumer
code. Discard is useful for some advanced use-cases, such as ensuring
all-or-nothing multi-record submission, or emulating temporary malloc()/free()
within single BPF program invocation.

Each reserved record is tracked by verifier through existing
reference-tracking logic, similar to socket ref-tracking. It is thus
impossible to reserve a record, but forget to submit (or discard) it.

bpf_ringbuf_query() helper allows to query various properties of ring buffer.
Currently 4 are supported:
  - BPF_RB_AVAIL_DATA returns amount of unconsumed data in ring buffer;
  - BPF_RB_RING_SIZE returns the size of ring buffer;
  - BPF_RB_CONS_POS/BPF_RB_PROD_POS returns current logical possition of
    consumer/producer, respectively.
Returned values are momentarily snapshots of ring buffer state and could be
off by the time helper returns, so this should be used only for
debugging/reporting reasons or for implementing various heuristics, that take
into account highly-changeable nature of some of those characteristics.

One such heuristic might involve more fine-grained control over poll/epoll
notifications about new data availability in ring buffer. Together with
BPF_RB_NO_WAKEUP/BPF_RB_FORCE_WAKEUP flags for output/commit/discard helpers,
it allows BPF program a high degree of control and, e.g., more efficient
batched notifications. Default self-balancing strategy, though, should be
adequate for most applications and will work reliable and efficiently already.

Design and implementation
-------------------------
This reserve/commit schema allows a natural way for multiple producers, either
on different CPUs or even on the same CPU/in the same BPF program, to reserve
independent records and work with them without blocking other producers. This
means that if BPF program was interruped by another BPF program sharing the
same ring buffer, they will both get a record reserved (provided there is
enough space left) and can work with it and submit it independently. This
applies to NMI context as well, except that due to using a spinlock during
reservation, in NMI context, bpf_ringbuf_reserve() might fail to get a lock,
in which case reservation will fail even if ring buffer is not full.

The ring buffer itself internally is implemented as a power-of-2 sized
circular buffer, with two logical and ever-increasing counters (which might
wrap around on 32-bit architectures, that's not a problem):
  - consumer counter shows up to which logical position consumer consumed the
    data;
  - producer counter denotes amount of data reserved by all producers.

Each time a record is reserved, producer that "owns" the record will
successfully advance producer counter. At that point, data is still not yet
ready to be consumed, though. Each record has 8 byte header, which contains
the length of reserved record, as well as two extra bits: busy bit to denote
that record is still being worked on, and discard bit, which might be set at
commit time if record is discarded. In the latter case, consumer is supposed
to skip the record and move on to the next one. Record header also encodes
record's relative offset from the beginning of ring buffer data area (in
pages). This allows bpf_ringbuf_commit()/bpf_ringbuf_discard() to accept only
the pointer to the record itself, without requiring also the pointer to ring
buffer itself. Ring buffer memory location will be restored from record
metadata header. This significantly simplifies verifier, as well as improving
API usability.

Producer counter increments are serialized under spinlock, so there is
a strict ordering between reservations. Commits, on the other hand, are
completely lockless and independent. All records become available to consumer
in the order of reservations, but only after all previous records where
already committed. It is thus possible for slow producers to temporarily hold
off submitted records, that were reserved later.

Reservation/commit/consumer protocol is verified by litmus tests in
Documentation/litmus-test/bpf-rb.

One interesting implementation bit, that significantly simplifies (and thus
speeds up as well) implementation of both producers and consumers is how data
area is mapped twice contiguously back-to-back in the virtual memory. This
allows to not take any special measures for samples that have to wrap around
at the end of the circular buffer data area, because the next page after the
last data page would be first data page again, and thus the sample will still
appear completely contiguous in virtual memory. See comment and a simple ASCII
diagram showing this visually in bpf_ringbuf_area_alloc().

Another feature that distinguishes BPF ringbuf from perf ring buffer is
a self-pacing notifications of new data being availability.
bpf_ringbuf_commit() implementation will send a notification of new record
being available after commit only if consumer has already caught up right up
to the record being committed. If not, consumer still has to catch up and thus
will see new data anyways without needing an extra poll notification.
Benchmarks (see tools/testing/selftests/bpf/benchs/bench_ringbuf.c) show that
this allows to achieve a very high throughput without having to resort to
tricks like "notify only every Nth sample", which are necessary with perf
buffer. For extreme cases, when BPF program wants more manual control of
notifications, commit/discard/output helpers accept BPF_RB_NO_WAKEUP and
BPF_RB_FORCE_WAKEUP flags, which give full control over notifications of data
availability, but require extra caution and diligence in using this API.

Comparison to alternatives
--------------------------
Before considering implementing BPF ring buffer from scratch existing
alternatives in kernel were evaluated, but didn't seem to meet the needs. They
largely fell into few categores:
  - per-CPU buffers (perf, ftrace, etc), which don't satisfy two motivations
    outlined above (ordering and memory consumption);
  - linked list-based implementations; while some were multi-producer designs,
    consuming these from user-space would be very complicated and most
    probably not performant; memory-mapping contiguous piece of memory is
    simpler and more performant for user-space consumers;
  - io_uring is SPSC, but also requires fixed-sized elements. Naively turning
    SPSC queue into MPSC w/ lock would have subpar performance compared to
    locked reserve + lockless commit, as with BPF ring buffer. Fixed sized
    elements would be too limiting for BPF programs, given existing BPF
    programs heavily rely on variable-sized perf buffer already;
  - specialized implementations (like a new printk ring buffer, [0]) with lots
    of printk-specific limitations and implications, that didn't seem to fit
    well for intended use with BPF programs.

  [0] https://lwn.net/Articles/779550/

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200529075424.3139988-2-andriin@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf.h

@@ -90,6 +90,8 @@ struct bpf_map_ops {
 	int (*map_direct_value_meta)(const struct bpf_map *map,
 				     u64 imm, u32 *off);
 	int (*map_mmap)(struct bpf_map *map, struct vm_area_struct *vma);
+	__poll_t (*map_poll)(struct bpf_map *map, struct file *filp,
+			     struct poll_table_struct *pts);
 };
 
 struct bpf_map_memory {
@@ -244,6 +246,9 @@ enum bpf_arg_type {
 	ARG_PTR_TO_LONG,	/* pointer to long */
 	ARG_PTR_TO_SOCKET,	/* pointer to bpf_sock (fullsock) */
 	ARG_PTR_TO_BTF_ID,	/* pointer to in-kernel struct */
+	ARG_PTR_TO_ALLOC_MEM,	/* pointer to dynamically allocated memory */
+	ARG_PTR_TO_ALLOC_MEM_OR_NULL,	/* pointer to dynamically allocated memory or NULL */
+	ARG_CONST_ALLOC_SIZE_OR_ZERO,	/* number of allocated bytes requested */
 };
 
 /* type of values returned from helper functions */
@@ -255,6 +260,7 @@ enum bpf_return_type {
 	RET_PTR_TO_SOCKET_OR_NULL,	/* returns a pointer to a socket or NULL */
 	RET_PTR_TO_TCP_SOCK_OR_NULL,	/* returns a pointer to a tcp_sock or NULL */
 	RET_PTR_TO_SOCK_COMMON_OR_NULL,	/* returns a pointer to a sock_common or NULL */
+	RET_PTR_TO_ALLOC_MEM_OR_NULL,	/* returns a pointer to dynamically allocated memory or NULL */
 };
 
 /* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs
@@ -322,6 +328,8 @@ enum bpf_reg_type {
 	PTR_TO_XDP_SOCK,	 /* reg points to struct xdp_sock */
 	PTR_TO_BTF_ID,		 /* reg points to kernel struct */
 	PTR_TO_BTF_ID_OR_NULL,	 /* reg points to kernel struct or NULL */
+	PTR_TO_MEM,		 /* reg points to valid memory region */
+	PTR_TO_MEM_OR_NULL,	 /* reg points to valid memory region or NULL */
 };
 
 /* The information passed from prog-specific *_is_valid_access
@@ -1611,6 +1619,11 @@ extern const struct bpf_func_proto bpf_tcp_sock_proto;
 extern const struct bpf_func_proto bpf_jiffies64_proto;
 extern const struct bpf_func_proto bpf_get_ns_current_pid_tgid_proto;
 extern const struct bpf_func_proto bpf_event_output_data_proto;
+extern const struct bpf_func_proto bpf_ringbuf_output_proto;
+extern const struct bpf_func_proto bpf_ringbuf_reserve_proto;
+extern const struct bpf_func_proto bpf_ringbuf_submit_proto;
+extern const struct bpf_func_proto bpf_ringbuf_discard_proto;
+extern const struct bpf_func_proto bpf_ringbuf_query_proto;
 
 const struct bpf_func_proto *bpf_tracing_func_proto(
 	enum bpf_func_id func_id, const struct bpf_prog *prog);

include/linux/bpf_types.h

@@ -118,6 +118,7 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_STACK, stack_map_ops)
 #if defined(CONFIG_BPF_JIT)
 BPF_MAP_TYPE(BPF_MAP_TYPE_STRUCT_OPS, bpf_struct_ops_map_ops)
 #endif
+BPF_MAP_TYPE(BPF_MAP_TYPE_RINGBUF, ringbuf_map_ops)
 
 BPF_LINK_TYPE(BPF_LINK_TYPE_RAW_TRACEPOINT, raw_tracepoint)
 BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING, tracing)

include/linux/bpf_verifier.h

@@ -54,6 +54,8 @@ struct bpf_reg_state {
 
 		u32 btf_id; /* for PTR_TO_BTF_ID */
 
+		u32 mem_size; /* for PTR_TO_MEM | PTR_TO_MEM_OR_NULL */
+
 		/* Max size from any of the above. */
 		unsigned long raw;
 	};
@@ -63,6 +65,8 @@ struct bpf_reg_state {
 	 * offset, so they can share range knowledge.
 	 * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
 	 * came from, when one is tested for != NULL.
+	 * For PTR_TO_MEM_OR_NULL this is used to identify memory allocation
+	 * for the purpose of tracking that it's freed.
 	 * For PTR_TO_SOCKET this is used to share which pointers retain the
 	 * same reference to the socket, to determine proper reference freeing.
 	 */

include/uapi/linux/bpf.h

@@ -147,6 +147,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_SK_STORAGE,
 	BPF_MAP_TYPE_DEVMAP_HASH,
 	BPF_MAP_TYPE_STRUCT_OPS,
+	BPF_MAP_TYPE_RINGBUF,
 };
 
 /* Note that tracing related programs such as
@@ -3157,6 +3158,59 @@ union bpf_attr {
  *		**bpf_sk_cgroup_id**\ ().
  *	Return
  *		The id is returned or 0 in case the id could not be retrieved.
+ *
+ * void *bpf_ringbuf_output(void *ringbuf, void *data, u64 size, u64 flags)
+ * 	Description
+ * 		Copy *size* bytes from *data* into a ring buffer *ringbuf*.
+ * 		If BPF_RB_NO_WAKEUP is specified in *flags*, no notification of
+ * 		new data availability is sent.
+ * 		IF BPF_RB_FORCE_WAKEUP is specified in *flags*, notification of
+ * 		new data availability is sent unconditionally.
+ * 	Return
+ * 		0, on success;
+ * 		< 0, on error.
+ *
+ * void *bpf_ringbuf_reserve(void *ringbuf, u64 size, u64 flags)
+ * 	Description
+ * 		Reserve *size* bytes of payload in a ring buffer *ringbuf*.
+ * 	Return
+ * 		Valid pointer with *size* bytes of memory available; NULL,
+ * 		otherwise.
+ *
+ * void bpf_ringbuf_submit(void *data, u64 flags)
+ * 	Description
+ * 		Submit reserved ring buffer sample, pointed to by *data*.
+ * 		If BPF_RB_NO_WAKEUP is specified in *flags*, no notification of
+ * 		new data availability is sent.
+ * 		IF BPF_RB_FORCE_WAKEUP is specified in *flags*, notification of
+ * 		new data availability is sent unconditionally.
+ * 	Return
+ * 		Nothing. Always succeeds.
+ *
+ * void bpf_ringbuf_discard(void *data, u64 flags)
+ * 	Description
+ * 		Discard reserved ring buffer sample, pointed to by *data*.
+ * 		If BPF_RB_NO_WAKEUP is specified in *flags*, no notification of
+ * 		new data availability is sent.
+ * 		IF BPF_RB_FORCE_WAKEUP is specified in *flags*, notification of
+ * 		new data availability is sent unconditionally.
+ * 	Return
+ * 		Nothing. Always succeeds.
+ *
+ * u64 bpf_ringbuf_query(void *ringbuf, u64 flags)
+ *	Description
+ *		Query various characteristics of provided ring buffer. What
+ *		exactly is queries is determined by *flags*:
+ *		  - BPF_RB_AVAIL_DATA - amount of data not yet consumed;
+ *		  - BPF_RB_RING_SIZE - the size of ring buffer;
+ *		  - BPF_RB_CONS_POS - consumer position (can wrap around);
+ *		  - BPF_RB_PROD_POS - producer(s) position (can wrap around);
+ *		Data returned is just a momentary snapshots of actual values
+ *		and could be inaccurate, so this facility should be used to
+ *		power heuristics and for reporting, not to make 100% correct
+ *		calculation.
+ *	Return
+ *		Requested value, or 0, if flags are not recognized.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3288,7 +3342,12 @@ union bpf_attr {
 	FN(seq_printf),			\
 	FN(seq_write),			\
 	FN(sk_cgroup_id),		\
-	FN(sk_ancestor_cgroup_id),
+	FN(sk_ancestor_cgroup_id),	\
+	FN(ringbuf_output),		\
+	FN(ringbuf_reserve),		\
+	FN(ringbuf_submit),		\
+	FN(ringbuf_discard),		\
+	FN(ringbuf_query),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -3398,6 +3457,29 @@ enum {
 	BPF_F_GET_BRANCH_RECORDS_SIZE	= (1ULL << 0),
 };
 
+/* BPF_FUNC_bpf_ringbuf_commit, BPF_FUNC_bpf_ringbuf_discard, and
+ * BPF_FUNC_bpf_ringbuf_output flags.
+ */
+enum {
+	BPF_RB_NO_WAKEUP		= (1ULL << 0),
+	BPF_RB_FORCE_WAKEUP		= (1ULL << 1),
+};
+
+/* BPF_FUNC_bpf_ringbuf_query flags */
+enum {
+	BPF_RB_AVAIL_DATA = 0,
+	BPF_RB_RING_SIZE = 1,
+	BPF_RB_CONS_POS = 2,
+	BPF_RB_PROD_POS = 3,
+};
+
+/* BPF ring buffer constants */
+enum {
+	BPF_RINGBUF_BUSY_BIT		= (1U << 31),
+	BPF_RINGBUF_DISCARD_BIT		= (1U << 30),
+	BPF_RINGBUF_HDR_SZ		= 8,
+};
+
 /* Mode for BPF_FUNC_skb_adjust_room helper. */
 enum bpf_adj_room_mode {
 	BPF_ADJ_ROOM_NET,

kernel/bpf/Makefile

@@ -4,7 +4,7 @@ CFLAGS_core.o += $(call cc-disable-warning, override-init)
 
 obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o task_iter.o
 obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
-obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o
+obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o
 obj-$(CONFIG_BPF_SYSCALL) += disasm.o
 obj-$(CONFIG_BPF_JIT) += trampoline.o
 obj-$(CONFIG_BPF_SYSCALL) += btf.o

kernel/bpf/helpers.c

@@ -635,6 +635,16 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_ktime_get_ns_proto;
 	case BPF_FUNC_ktime_get_boot_ns:
 		return &bpf_ktime_get_boot_ns_proto;
+	case BPF_FUNC_ringbuf_output:
+		return &bpf_ringbuf_output_proto;
+	case BPF_FUNC_ringbuf_reserve:
+		return &bpf_ringbuf_reserve_proto;
+	case BPF_FUNC_ringbuf_submit:
+		return &bpf_ringbuf_submit_proto;
+	case BPF_FUNC_ringbuf_discard:
+		return &bpf_ringbuf_discard_proto;
+	case BPF_FUNC_ringbuf_query:
+		return &bpf_ringbuf_query_proto;
 	default:
 		break;
 	}

kernel/bpf/ringbuf.c

@@ -0,0 +1,501 @@
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/err.h>
+#include <linux/irq_work.h>
+#include <linux/slab.h>
+#include <linux/filter.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/wait.h>
+#include <linux/poll.h>
+#include <uapi/linux/btf.h>
+
+#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE)
+
+/* non-mmap()'able part of bpf_ringbuf (everything up to consumer page) */
+#define RINGBUF_PGOFF \
+	(offsetof(struct bpf_ringbuf, consumer_pos) >> PAGE_SHIFT)
+/* consumer page and producer page */
+#define RINGBUF_POS_PAGES 2
+
+#define RINGBUF_MAX_RECORD_SZ (UINT_MAX/4)
+
+/* Maximum size of ring buffer area is limited by 32-bit page offset within
+ * record header, counted in pages. Reserve 8 bits for extensibility, and take
+ * into account few extra pages for consumer/producer pages and
+ * non-mmap()'able parts. This gives 64GB limit, which seems plenty for single
+ * ring buffer.
+ */
+#define RINGBUF_MAX_DATA_SZ \
+	(((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)
+
+struct bpf_ringbuf {
+	wait_queue_head_t waitq;
+	struct irq_work work;
+	u64 mask;
+	struct page **pages;
+	int nr_pages;
+	spinlock_t spinlock ____cacheline_aligned_in_smp;
+	/* Consumer and producer counters are put into separate pages to allow
+	 * mapping consumer page as r/w, but restrict producer page to r/o.
+	 * This protects producer position from being modified by user-space
+	 * application and ruining in-kernel position tracking.
+	 */
+	unsigned long consumer_pos __aligned(PAGE_SIZE);
+	unsigned long producer_pos __aligned(PAGE_SIZE);
+	char data[] __aligned(PAGE_SIZE);
+};
+
+struct bpf_ringbuf_map {
+	struct bpf_map map;
+	struct bpf_map_memory memory;
+	struct bpf_ringbuf *rb;
+};
+
+/* 8-byte ring buffer record header structure */
+struct bpf_ringbuf_hdr {
+	u32 len;
+	u32 pg_off;
+};
+
+static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
+{
+	const gfp_t flags = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN |
+			    __GFP_ZERO;
+	int nr_meta_pages = RINGBUF_PGOFF + RINGBUF_POS_PAGES;
+	int nr_data_pages = data_sz >> PAGE_SHIFT;
+	int nr_pages = nr_meta_pages + nr_data_pages;
+	struct page **pages, *page;
+	struct bpf_ringbuf *rb;
+	size_t array_size;
+	int i;
+
+	/* Each data page is mapped twice to allow "virtual"
+	 * continuous read of samples wrapping around the end of ring
+	 * buffer area:
+	 * ------------------------------------------------------
+	 * | meta pages |  real data pages  |  same data pages  |
+	 * ------------------------------------------------------
+	 * |            | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
+	 * ------------------------------------------------------
+	 * |            | TA             DA | TA             DA |
+	 * ------------------------------------------------------
+	 *                               ^^^^^^^
+	 *                                  |
+	 * Here, no need to worry about special handling of wrapped-around
+	 * data due to double-mapped data pages. This works both in kernel and
+	 * when mmap()'ed in user-space, simplifying both kernel and
+	 * user-space implementations significantly.
+	 */
+	array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
+	if (array_size > PAGE_SIZE)
+		pages = vmalloc_node(array_size, numa_node);
+	else
+		pages = kmalloc_node(array_size, flags, numa_node);
+	if (!pages)
+		return NULL;
+
+	for (i = 0; i < nr_pages; i++) {
+		page = alloc_pages_node(numa_node, flags, 0);
+		if (!page) {
+			nr_pages = i;
+			goto err_free_pages;
+		}
+		pages[i] = page;
+		if (i >= nr_meta_pages)
+			pages[nr_data_pages + i] = page;
+	}
+
+	rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
+		  VM_ALLOC | VM_USERMAP, PAGE_KERNEL);
+	if (rb) {
+		rb->pages = pages;
+		rb->nr_pages = nr_pages;
+		return rb;
+	}
+
+err_free_pages:
+	for (i = 0; i < nr_pages; i++)
+		__free_page(pages[i]);
+	kvfree(pages);
+	return NULL;
+}
+
+static void bpf_ringbuf_notify(struct irq_work *work)
+{
+	struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
+
+	wake_up_all(&rb->waitq);
+}
+
+static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
+{
+	struct bpf_ringbuf *rb;
+
+	if (!data_sz || !PAGE_ALIGNED(data_sz))
+		return ERR_PTR(-EINVAL);
+
+#ifdef CONFIG_64BIT
+	/* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
+	if (data_sz > RINGBUF_MAX_DATA_SZ)
+		return ERR_PTR(-E2BIG);
+#endif
+
+	rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
+	if (!rb)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock_init(&rb->spinlock);
+	init_waitqueue_head(&rb->waitq);
+	init_irq_work(&rb->work, bpf_ringbuf_notify);
+
+	rb->mask = data_sz - 1;
+	rb->consumer_pos = 0;
+	rb->producer_pos = 0;
+
+	return rb;
+}
+
+static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
+{
+	struct bpf_ringbuf_map *rb_map;
+	u64 cost;
+	int err;
+
+	if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
+		return ERR_PTR(-EINVAL);
+
+	if (attr->key_size || attr->value_size ||
+	    attr->max_entries == 0 || !PAGE_ALIGNED(attr->max_entries))
+		return ERR_PTR(-EINVAL);
+
+	rb_map = kzalloc(sizeof(*rb_map), GFP_USER);
+	if (!rb_map)
+		return ERR_PTR(-ENOMEM);
+
+	bpf_map_init_from_attr(&rb_map->map, attr);
+
+	cost = sizeof(struct bpf_ringbuf_map) +
+	       sizeof(struct bpf_ringbuf) +
+	       attr->max_entries;
+	err = bpf_map_charge_init(&rb_map->map.memory, cost);
+	if (err)
+		goto err_free_map;
+
+	rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
+	if (IS_ERR(rb_map->rb)) {
+		err = PTR_ERR(rb_map->rb);
+		goto err_uncharge;
+	}
+
+	return &rb_map->map;
+
+err_uncharge:
+	bpf_map_charge_finish(&rb_map->map.memory);
+err_free_map:
+	kfree(rb_map);
+	return ERR_PTR(err);
+}
+
+static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
+{
+	/* copy pages pointer and nr_pages to local variable, as we are going
+	 * to unmap rb itself with vunmap() below
+	 */
+	struct page **pages = rb->pages;
+	int i, nr_pages = rb->nr_pages;
+
+	vunmap(rb);
+	for (i = 0; i < nr_pages; i++)
+		__free_page(pages[i]);
+	kvfree(pages);
+}
+
+static void ringbuf_map_free(struct bpf_map *map)
+{
+	struct bpf_ringbuf_map *rb_map;
+
+	/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
+	 * so the programs (can be more than one that used this map) were
+	 * disconnected from events. Wait for outstanding critical sections in
+	 * these programs to complete
+	 */
+	synchronize_rcu();
+
+	rb_map = container_of(map, struct bpf_ringbuf_map, map);
+	bpf_ringbuf_free(rb_map->rb);
+	kfree(rb_map);
+}
+
+static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+
+static int ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
+				   u64 flags)
+{
+	return -ENOTSUPP;
+}
+
+static int ringbuf_map_delete_elem(struct bpf_map *map, void *key)
+{
+	return -ENOTSUPP;
+}
+
+static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
+				    void *next_key)
+{
+	return -ENOTSUPP;
+}
+
+static size_t bpf_ringbuf_mmap_page_cnt(const struct bpf_ringbuf *rb)
+{
+	size_t data_pages = (rb->mask + 1) >> PAGE_SHIFT;
+
+	/* consumer page + producer page + 2 x data pages */
+	return RINGBUF_POS_PAGES + 2 * data_pages;
+}
+
+static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
+{
+	struct bpf_ringbuf_map *rb_map;
+	size_t mmap_sz;
+
+	rb_map = container_of(map, struct bpf_ringbuf_map, map);
+	mmap_sz = bpf_ringbuf_mmap_page_cnt(rb_map->rb) << PAGE_SHIFT;
+
+	if (vma->vm_pgoff * PAGE_SIZE + (vma->vm_end - vma->vm_start) > mmap_sz)
+		return -EINVAL;
+
+	return remap_vmalloc_range(vma, rb_map->rb,
+				   vma->vm_pgoff + RINGBUF_PGOFF);
+}
+
+static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
+{
+	unsigned long cons_pos, prod_pos;
+
+	cons_pos = smp_load_acquire(&rb->consumer_pos);
+	prod_pos = smp_load_acquire(&rb->producer_pos);
+	return prod_pos - cons_pos;
+}
+
+static __poll_t ringbuf_map_poll(struct bpf_map *map, struct file *filp,
+				 struct poll_table_struct *pts)
+{
+	struct bpf_ringbuf_map *rb_map;
+
+	rb_map = container_of(map, struct bpf_ringbuf_map, map);
+	poll_wait(filp, &rb_map->rb->waitq, pts);
+
+	if (ringbuf_avail_data_sz(rb_map->rb))
+		return EPOLLIN | EPOLLRDNORM;
+	return 0;
+}
+
+const struct bpf_map_ops ringbuf_map_ops = {
+	.map_alloc = ringbuf_map_alloc,
+	.map_free = ringbuf_map_free,
+	.map_mmap = ringbuf_map_mmap,
+	.map_poll = ringbuf_map_poll,
+	.map_lookup_elem = ringbuf_map_lookup_elem,
+	.map_update_elem = ringbuf_map_update_elem,
+	.map_delete_elem = ringbuf_map_delete_elem,
+	.map_get_next_key = ringbuf_map_get_next_key,
+};
+
+/* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
+ * calculate offset from record metadata to ring buffer in pages, rounded
+ * down. This page offset is stored as part of record metadata and allows to
+ * restore struct bpf_ringbuf * from record pointer. This page offset is
+ * stored at offset 4 of record metadata header.
+ */
+static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
+				     struct bpf_ringbuf_hdr *hdr)
+{
+	return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
+}
+
+/* Given pointer to ring buffer record header, restore pointer to struct
+ * bpf_ringbuf itself by using page offset stored at offset 4
+ */
+static struct bpf_ringbuf *
+bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
+{
+	unsigned long addr = (unsigned long)(void *)hdr;
+	unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
+
+	return (void*)((addr & PAGE_MASK) - off);
+}
+
+static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
+{
+	unsigned long cons_pos, prod_pos, new_prod_pos, flags;
+	u32 len, pg_off;
+	struct bpf_ringbuf_hdr *hdr;
+
+	if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
+		return NULL;
+
+	len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
+	cons_pos = smp_load_acquire(&rb->consumer_pos);
+
+	if (in_nmi()) {
+		if (!spin_trylock_irqsave(&rb->spinlock, flags))
+			return NULL;
+	} else {
+		spin_lock_irqsave(&rb->spinlock, flags);
+	}
+
+	prod_pos = rb->producer_pos;
+	new_prod_pos = prod_pos + len;
+
+	/* check for out of ringbuf space by ensuring producer position
+	 * doesn't advance more than (ringbuf_size - 1) ahead
+	 */
+	if (new_prod_pos - cons_pos > rb->mask) {
+		spin_unlock_irqrestore(&rb->spinlock, flags);
+		return NULL;
+	}
+
+	hdr = (void *)rb->data + (prod_pos & rb->mask);
+	pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
+	hdr->len = size | BPF_RINGBUF_BUSY_BIT;
+	hdr->pg_off = pg_off;
+
+	/* pairs with consumer's smp_load_acquire() */
+	smp_store_release(&rb->producer_pos, new_prod_pos);
+
+	spin_unlock_irqrestore(&rb->spinlock, flags);
+
+	return (void *)hdr + BPF_RINGBUF_HDR_SZ;
+}
+
+BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
+{
+	struct bpf_ringbuf_map *rb_map;
+
+	if (unlikely(flags))
+		return 0;
+
+	rb_map = container_of(map, struct bpf_ringbuf_map, map);
+	return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
+}
+
+const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
+	.func		= bpf_ringbuf_reserve,
+	.ret_type	= RET_PTR_TO_ALLOC_MEM_OR_NULL,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_CONST_ALLOC_SIZE_OR_ZERO,
+	.arg3_type	= ARG_ANYTHING,
+};
+
+static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
+{
+	unsigned long rec_pos, cons_pos;
+	struct bpf_ringbuf_hdr *hdr;
+	struct bpf_ringbuf *rb;
+	u32 new_len;
+
+	hdr = sample - BPF_RINGBUF_HDR_SZ;
+	rb = bpf_ringbuf_restore_from_rec(hdr);
+	new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
+	if (discard)
+		new_len |= BPF_RINGBUF_DISCARD_BIT;
+
+	/* update record header with correct final size prefix */
+	xchg(&hdr->len, new_len);
+
+	/* if consumer caught up and is waiting for our record, notify about
+	 * new data availability
+	 */
+	rec_pos = (void *)hdr - (void *)rb->data;
+	cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
+
+	if (flags & BPF_RB_FORCE_WAKEUP)
+		irq_work_queue(&rb->work);
+	else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
+		irq_work_queue(&rb->work);
+}
+
+BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
+{
+	bpf_ringbuf_commit(sample, flags, false /* discard */);
+	return 0;
+}
+
+const struct bpf_func_proto bpf_ringbuf_submit_proto = {
+	.func		= bpf_ringbuf_submit,
+	.ret_type	= RET_VOID,
+	.arg1_type	= ARG_PTR_TO_ALLOC_MEM,
+	.arg2_type	= ARG_ANYTHING,
+};
+
+BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
+{
+	bpf_ringbuf_commit(sample, flags, true /* discard */);
+	return 0;
+}
+
+const struct bpf_func_proto bpf_ringbuf_discard_proto = {
+	.func		= bpf_ringbuf_discard,
+	.ret_type	= RET_VOID,
+	.arg1_type	= ARG_PTR_TO_ALLOC_MEM,
+	.arg2_type	= ARG_ANYTHING,
+};
+
+BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
+	   u64, flags)
+{
+	struct bpf_ringbuf_map *rb_map;
+	void *rec;
+
+	if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
+		return -EINVAL;
+
+	rb_map = container_of(map, struct bpf_ringbuf_map, map);
+	rec = __bpf_ringbuf_reserve(rb_map->rb, size);
+	if (!rec)
+		return -EAGAIN;
+
+	memcpy(rec, data, size);
+	bpf_ringbuf_commit(rec, flags, false /* discard */);
+	return 0;
+}
+
+const struct bpf_func_proto bpf_ringbuf_output_proto = {
+	.func		= bpf_ringbuf_output,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
+	.arg4_type	= ARG_ANYTHING,
+};
+
+BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags)
+{
+	struct bpf_ringbuf *rb;
+
+	rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
+
+	switch (flags) {
+	case BPF_RB_AVAIL_DATA:
+		return ringbuf_avail_data_sz(rb);
+	case BPF_RB_RING_SIZE:
+		return rb->mask + 1;
+	case BPF_RB_CONS_POS:
+		return smp_load_acquire(&rb->consumer_pos);
+	case BPF_RB_PROD_POS:
+		return smp_load_acquire(&rb->producer_pos);
+	default:
+		return 0;
+	}
+}
+
+const struct bpf_func_proto bpf_ringbuf_query_proto = {
+	.func		= bpf_ringbuf_query,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_ANYTHING,
+};

kernel/bpf/syscall.c

@@ -26,6 +26,7 @@
 #include <linux/audit.h>
 #include <uapi/linux/btf.h>
 #include <linux/bpf_lsm.h>
+#include <linux/poll.h>
 
 #define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY || \
 			  (map)->map_type == BPF_MAP_TYPE_CGROUP_ARRAY || \
@@ -662,6 +663,16 @@ out:
 	return err;
 }
 
+static __poll_t bpf_map_poll(struct file *filp, struct poll_table_struct *pts)
+{
+	struct bpf_map *map = filp->private_data;
+
+	if (map->ops->map_poll)
+		return map->ops->map_poll(map, filp, pts);
+
+	return EPOLLERR;
+}
+
 const struct file_operations bpf_map_fops = {
 #ifdef CONFIG_PROC_FS
 	.show_fdinfo	= bpf_map_show_fdinfo,
@@ -670,6 +681,7 @@ const struct file_operations bpf_map_fops = {
 	.read		= bpf_dummy_read,
 	.write		= bpf_dummy_write,
 	.mmap		= bpf_map_mmap,
+	.poll		= bpf_map_poll,
 };
 
 int bpf_map_new_fd(struct bpf_map *map, int flags)

kernel/bpf/verifier.c

@@ -233,6 +233,7 @@ struct bpf_call_arg_meta {
 	bool pkt_access;
 	int regno;
 	int access_size;
+	int mem_size;
 	u64 msize_max_value;
 	int ref_obj_id;
 	int func_id;
@@ -408,7 +409,8 @@ static bool reg_type_may_be_null(enum bpf_reg_type type)
 	       type == PTR_TO_SOCKET_OR_NULL ||
 	       type == PTR_TO_SOCK_COMMON_OR_NULL ||
 	       type == PTR_TO_TCP_SOCK_OR_NULL ||
-	       type == PTR_TO_BTF_ID_OR_NULL;
+	       type == PTR_TO_BTF_ID_OR_NULL ||
+	       type == PTR_TO_MEM_OR_NULL;
 }
 
 static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
@@ -422,7 +424,9 @@ static bool reg_type_may_be_refcounted_or_null(enum bpf_reg_type type)
 	return type == PTR_TO_SOCKET ||
 		type == PTR_TO_SOCKET_OR_NULL ||
 		type == PTR_TO_TCP_SOCK ||
-		type == PTR_TO_TCP_SOCK_OR_NULL;
+		type == PTR_TO_TCP_SOCK_OR_NULL ||
+		type == PTR_TO_MEM ||
+		type == PTR_TO_MEM_OR_NULL;
 }
 
 static bool arg_type_may_be_refcounted(enum bpf_arg_type type)
@@ -436,7 +440,9 @@ static bool arg_type_may_be_refcounted(enum bpf_arg_type type)
  */
 static bool is_release_function(enum bpf_func_id func_id)
 {
-	return func_id == BPF_FUNC_sk_release;
+	return func_id == BPF_FUNC_sk_release ||
+	       func_id == BPF_FUNC_ringbuf_submit ||
+	       func_id == BPF_FUNC_ringbuf_discard;
 }
 
 static bool may_be_acquire_function(enum bpf_func_id func_id)
@@ -444,7 +450,8 @@ static bool may_be_acquire_function(enum bpf_func_id func_id)
 	return func_id == BPF_FUNC_sk_lookup_tcp ||
 		func_id == BPF_FUNC_sk_lookup_udp ||
 		func_id == BPF_FUNC_skc_lookup_tcp ||
-		func_id == BPF_FUNC_map_lookup_elem;
+		func_id == BPF_FUNC_map_lookup_elem ||
+	        func_id == BPF_FUNC_ringbuf_reserve;
 }
 
 static bool is_acquire_function(enum bpf_func_id func_id,
@@ -454,7 +461,8 @@ static bool is_acquire_function(enum bpf_func_id func_id,
 
 	if (func_id == BPF_FUNC_sk_lookup_tcp ||
 	    func_id == BPF_FUNC_sk_lookup_udp ||
-	    func_id == BPF_FUNC_skc_lookup_tcp)
+	    func_id == BPF_FUNC_skc_lookup_tcp ||
+	    func_id == BPF_FUNC_ringbuf_reserve)
 		return true;
 
 	if (func_id == BPF_FUNC_map_lookup_elem &&
@@ -494,6 +502,8 @@ static const char * const reg_type_str[] = {
 	[PTR_TO_XDP_SOCK]	= "xdp_sock",
 	[PTR_TO_BTF_ID]		= "ptr_",
 	[PTR_TO_BTF_ID_OR_NULL]	= "ptr_or_null_",
+	[PTR_TO_MEM]		= "mem",
+	[PTR_TO_MEM_OR_NULL]	= "mem_or_null",
 };
 
 static char slot_type_char[] = {
@@ -2468,32 +2478,49 @@ static int check_map_access_type(struct bpf_verifier_env *env, u32 regno,
 	return 0;
 }
 
-/* check read/write into map element returned by bpf_map_lookup_elem() */
-static int __check_map_access(struct bpf_verifier_env *env, u32 regno, int off,
-			      int size, bool zero_size_allowed)
+/* check read/write into memory region (e.g., map value, ringbuf sample, etc) */
+static int __check_mem_access(struct bpf_verifier_env *env, int regno,
+			      int off, int size, u32 mem_size,
+			      bool zero_size_allowed)
 {
-	struct bpf_reg_state *regs = cur_regs(env);
-	struct bpf_map *map = regs[regno].map_ptr;
+	bool size_ok = size > 0 || (size == 0 && zero_size_allowed);
+	struct bpf_reg_state *reg;
 
-	if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) ||
-	    off + size > map->value_size) {
+	if (off >= 0 && size_ok && (u64)off + size <= mem_size)
+		return 0;
+
+	reg = &cur_regs(env)[regno];
+	switch (reg->type) {
+	case PTR_TO_MAP_VALUE:
 		verbose(env, "invalid access to map value, value_size=%d off=%d size=%d\n",
-			map->value_size, off, size);
-		return -EACCES;
+			mem_size, off, size);
+		break;
+	case PTR_TO_PACKET:
+	case PTR_TO_PACKET_META:
+	case PTR_TO_PACKET_END:
+		verbose(env, "invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
+			off, size, regno, reg->id, off, mem_size);
+		break;
+	case PTR_TO_MEM:
+	default:
+		verbose(env, "invalid access to memory, mem_size=%u off=%d size=%d\n",
+			mem_size, off, size);
 	}
-	return 0;
+
+	return -EACCES;
 }
 
-/* check read/write into a map element with possible variable offset */
-static int check_map_access(struct bpf_verifier_env *env, u32 regno,
-			    int off, int size, bool zero_size_allowed)
+/* check read/write into a memory region with possible variable offset */
+static int check_mem_region_access(struct bpf_verifier_env *env, u32 regno,
+				   int off, int size, u32 mem_size,
+				   bool zero_size_allowed)
 {
 	struct bpf_verifier_state *vstate = env->cur_state;
 	struct bpf_func_state *state = vstate->frame[vstate->curframe];
 	struct bpf_reg_state *reg = &state->regs[regno];
 	int err;
 
-	/* We may have adjusted the register to this map value, so we
+	/* We may have adjusted the register pointing to memory region, so we
 	 * need to try adding each of min_value and max_value to off
 	 * to make sure our theoretical access will be safe.
 	 */
@@ -2514,10 +2541,10 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 			regno);
 		return -EACCES;
 	}
-	err = __check_map_access(env, regno, reg->smin_value + off, size,
-				 zero_size_allowed);
+	err = __check_mem_access(env, regno, reg->smin_value + off, size,
+				 mem_size, zero_size_allowed);
 	if (err) {
-		verbose(env, "R%d min value is outside of the array range\n",
+		verbose(env, "R%d min value is outside of the allowed memory range\n",
 			regno);
 		return err;
 	}
@@ -2527,18 +2554,38 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 	 * If reg->umax_value + off could overflow, treat that as unbounded too.
 	 */
 	if (reg->umax_value >= BPF_MAX_VAR_OFF) {
-		verbose(env, "R%d unbounded memory access, make sure to bounds check any array access into a map\n",
+		verbose(env, "R%d unbounded memory access, make sure to bounds check any such access\n",
 			regno);
 		return -EACCES;
 	}
-	err = __check_map_access(env, regno, reg->umax_value + off, size,
-				 zero_size_allowed);
-	if (err)
-		verbose(env, "R%d max value is outside of the array range\n",
+	err = __check_mem_access(env, regno, reg->umax_value + off, size,
+				 mem_size, zero_size_allowed);
+	if (err) {
+		verbose(env, "R%d max value is outside of the allowed memory range\n",
 			regno);
+		return err;
+	}
 
-	if (map_value_has_spin_lock(reg->map_ptr)) {
-		u32 lock = reg->map_ptr->spin_lock_off;
+	return 0;
+}
+
+/* check read/write into a map element with possible variable offset */
+static int check_map_access(struct bpf_verifier_env *env, u32 regno,
+			    int off, int size, bool zero_size_allowed)
+{
+	struct bpf_verifier_state *vstate = env->cur_state;
+	struct bpf_func_state *state = vstate->frame[vstate->curframe];
+	struct bpf_reg_state *reg = &state->regs[regno];
+	struct bpf_map *map = reg->map_ptr;
+	int err;
+
+	err = check_mem_region_access(env, regno, off, size, map->value_size,
+				      zero_size_allowed);
+	if (err)
+		return err;
+
+	if (map_value_has_spin_lock(map)) {
+		u32 lock = map->spin_lock_off;
 
 		/* if any part of struct bpf_spin_lock can be touched by
 		 * load/store reject this program.
@@ -2596,21 +2643,6 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
 	}
 }
 
-static int __check_packet_access(struct bpf_verifier_env *env, u32 regno,
-				 int off, int size, bool zero_size_allowed)
-{
-	struct bpf_reg_state *regs = cur_regs(env);
-	struct bpf_reg_state *reg = &regs[regno];
-
-	if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) ||
-	    (u64)off + size > reg->range) {
-		verbose(env, "invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
-			off, size, regno, reg->id, reg->off, reg->range);
-		return -EACCES;
-	}
-	return 0;
-}
-
 static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
 			       int size, bool zero_size_allowed)
 {
@@ -2631,16 +2663,17 @@ static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
 			regno);
 		return -EACCES;
 	}
-	err = __check_packet_access(env, regno, off, size, zero_size_allowed);
+	err = __check_mem_access(env, regno, off, size, reg->range,
+				 zero_size_allowed);
 	if (err) {
 		verbose(env, "R%d offset is outside of the packet\n", regno);
 		return err;
 	}
 
-	/* __check_packet_access has made sure "off + size - 1" is within u16.
+	/* __check_mem_access has made sure "off + size - 1" is within u16.
 	 * reg->umax_value can't be bigger than MAX_PACKET_OFF which is 0xffff,
 	 * otherwise find_good_pkt_pointers would have refused to set range info
-	 * that __check_packet_access would have rejected this pkt access.
+	 * that __check_mem_access would have rejected this pkt access.
 	 * Therefore, "off + reg->umax_value + size - 1" won't overflow u32.
 	 */
 	env->prog->aux->max_pkt_offset =
@@ -3220,6 +3253,16 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 				mark_reg_unknown(env, regs, value_regno);
 			}
 		}
+	} else if (reg->type == PTR_TO_MEM) {
+		if (t == BPF_WRITE && value_regno >= 0 &&
+		    is_pointer_value(env, value_regno)) {
+			verbose(env, "R%d leaks addr into mem\n", value_regno);
+			return -EACCES;
+		}
+		err = check_mem_region_access(env, regno, off, size,
+					      reg->mem_size, false);
+		if (!err && t == BPF_READ && value_regno >= 0)
+			mark_reg_unknown(env, regs, value_regno);
 	} else if (reg->type == PTR_TO_CTX) {
 		enum bpf_reg_type reg_type = SCALAR_VALUE;
 		u32 btf_id = 0;
@@ -3557,6 +3600,10 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
 			return -EACCES;
 		return check_map_access(env, regno, reg->off, access_size,
 					zero_size_allowed);
+	case PTR_TO_MEM:
+		return check_mem_region_access(env, regno, reg->off,
+					       access_size, reg->mem_size,
+					       zero_size_allowed);
 	default: /* scalar_value|ptr_to_stack or invalid ptr */
 		return check_stack_boundary(env, regno, access_size,
 					    zero_size_allowed, meta);
@@ -3661,6 +3708,17 @@ static bool arg_type_is_mem_size(enum bpf_arg_type type)
 	       type == ARG_CONST_SIZE_OR_ZERO;
 }
 
+static bool arg_type_is_alloc_mem_ptr(enum bpf_arg_type type)
+{
+	return type == ARG_PTR_TO_ALLOC_MEM ||
+	       type == ARG_PTR_TO_ALLOC_MEM_OR_NULL;
+}
+
+static bool arg_type_is_alloc_size(enum bpf_arg_type type)
+{
+	return type == ARG_CONST_ALLOC_SIZE_OR_ZERO;
+}
+
 static bool arg_type_is_int_ptr(enum bpf_arg_type type)
 {
 	return type == ARG_PTR_TO_INT ||
@@ -3720,7 +3778,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 			 type != expected_type)
 			goto err_type;
 	} else if (arg_type == ARG_CONST_SIZE ||
-		   arg_type == ARG_CONST_SIZE_OR_ZERO) {
+		   arg_type == ARG_CONST_SIZE_OR_ZERO ||
+		   arg_type == ARG_CONST_ALLOC_SIZE_OR_ZERO) {
 		expected_type = SCALAR_VALUE;
 		if (type != expected_type)
 			goto err_type;
@@ -3791,13 +3850,29 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 		 * happens during stack boundary checking.
 		 */
 		if (register_is_null(reg) &&
-		    arg_type == ARG_PTR_TO_MEM_OR_NULL)
+		    (arg_type == ARG_PTR_TO_MEM_OR_NULL ||
+		     arg_type == ARG_PTR_TO_ALLOC_MEM_OR_NULL))
 			/* final test in check_stack_boundary() */;
 		else if (!type_is_pkt_pointer(type) &&
 			 type != PTR_TO_MAP_VALUE &&
+			 type != PTR_TO_MEM &&
 			 type != expected_type)
 			goto err_type;
 		meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM;
+	} else if (arg_type_is_alloc_mem_ptr(arg_type)) {
+		expected_type = PTR_TO_MEM;
+		if (register_is_null(reg) &&
+		    arg_type == ARG_PTR_TO_ALLOC_MEM_OR_NULL)
+			/* final test in check_stack_boundary() */;
+		else if (type != expected_type)
+			goto err_type;
+		if (meta->ref_obj_id) {
+			verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
+				regno, reg->ref_obj_id,
+				meta->ref_obj_id);
+			return -EFAULT;
+		}
+		meta->ref_obj_id = reg->ref_obj_id;
 	} else if (arg_type_is_int_ptr(arg_type)) {
 		expected_type = PTR_TO_STACK;
 		if (!type_is_pkt_pointer(type) &&
@@ -3893,6 +3968,13 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
 					      zero_size_allowed, meta);
 		if (!err)
 			err = mark_chain_precision(env, regno);
+	} else if (arg_type_is_alloc_size(arg_type)) {
+		if (!tnum_is_const(reg->var_off)) {
+			verbose(env, "R%d unbounded size, use 'var &= const' or 'if (var < const)'\n",
+				regno);
+			return -EACCES;
+		}
+		meta->mem_size = reg->var_off.value;
 	} else if (arg_type_is_int_ptr(arg_type)) {
 		int size = int_ptr_type_to_size(arg_type);
 
@@ -3929,6 +4011,14 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
 		    func_id != BPF_FUNC_xdp_output)
 			goto error;
 		break;
+	case BPF_MAP_TYPE_RINGBUF:
+		if (func_id != BPF_FUNC_ringbuf_output &&
+		    func_id != BPF_FUNC_ringbuf_reserve &&
+		    func_id != BPF_FUNC_ringbuf_submit &&
+		    func_id != BPF_FUNC_ringbuf_discard &&
+		    func_id != BPF_FUNC_ringbuf_query)
+			goto error;
+		break;
 	case BPF_MAP_TYPE_STACK_TRACE:
 		if (func_id != BPF_FUNC_get_stackid)
 			goto error;
@@ -4655,6 +4745,11 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 		mark_reg_known_zero(env, regs, BPF_REG_0);
 		regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;
 		regs[BPF_REG_0].id = ++env->id_gen;
+	} else if (fn->ret_type == RET_PTR_TO_ALLOC_MEM_OR_NULL) {
+		mark_reg_known_zero(env, regs, BPF_REG_0);
+		regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
+		regs[BPF_REG_0].id = ++env->id_gen;
+		regs[BPF_REG_0].mem_size = meta.mem_size;
 	} else {
 		verbose(env, "unknown return type %d of func %s#%d\n",
 			fn->ret_type, func_id_name(func_id), func_id);
@@ -6611,6 +6706,8 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
 			reg->type = PTR_TO_TCP_SOCK;
 		} else if (reg->type == PTR_TO_BTF_ID_OR_NULL) {
 			reg->type = PTR_TO_BTF_ID;
+		} else if (reg->type == PTR_TO_MEM_OR_NULL) {
+			reg->type = PTR_TO_MEM;
 		}
 		if (is_null) {
 			/* We don't need id and ref_obj_id from this point

kernel/trace/bpf_trace.c

@@ -1088,6 +1088,16 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_perf_event_read_value_proto;
 	case BPF_FUNC_get_ns_current_pid_tgid:
 		return &bpf_get_ns_current_pid_tgid_proto;
+	case BPF_FUNC_ringbuf_output:
+		return &bpf_ringbuf_output_proto;
+	case BPF_FUNC_ringbuf_reserve:
+		return &bpf_ringbuf_reserve_proto;
+	case BPF_FUNC_ringbuf_submit:
+		return &bpf_ringbuf_submit_proto;
+	case BPF_FUNC_ringbuf_discard:
+		return &bpf_ringbuf_discard_proto;
+	case BPF_FUNC_ringbuf_query:
+		return &bpf_ringbuf_query_proto;
 	default:
 		return NULL;
 	}

tools/include/uapi/linux/bpf.h

@@ -147,6 +147,7 @@ enum bpf_map_type {
 	BPF_MAP_TYPE_SK_STORAGE,
 	BPF_MAP_TYPE_DEVMAP_HASH,
 	BPF_MAP_TYPE_STRUCT_OPS,
+	BPF_MAP_TYPE_RINGBUF,
 };
 
 /* Note that tracing related programs such as
@@ -3157,6 +3158,59 @@ union bpf_attr {
  *		**bpf_sk_cgroup_id**\ ().
  *	Return
  *		The id is returned or 0 in case the id could not be retrieved.
+ *
+ * void *bpf_ringbuf_output(void *ringbuf, void *data, u64 size, u64 flags)
+ * 	Description
+ * 		Copy *size* bytes from *data* into a ring buffer *ringbuf*.
+ * 		If BPF_RB_NO_WAKEUP is specified in *flags*, no notification of
+ * 		new data availability is sent.
+ * 		IF BPF_RB_FORCE_WAKEUP is specified in *flags*, notification of
+ * 		new data availability is sent unconditionally.
+ * 	Return
+ * 		0, on success;
+ * 		< 0, on error.
+ *
+ * void *bpf_ringbuf_reserve(void *ringbuf, u64 size, u64 flags)
+ * 	Description
+ * 		Reserve *size* bytes of payload in a ring buffer *ringbuf*.
+ * 	Return
+ * 		Valid pointer with *size* bytes of memory available; NULL,
+ * 		otherwise.
+ *
+ * void bpf_ringbuf_submit(void *data, u64 flags)
+ * 	Description
+ * 		Submit reserved ring buffer sample, pointed to by *data*.
+ * 		If BPF_RB_NO_WAKEUP is specified in *flags*, no notification of
+ * 		new data availability is sent.
+ * 		IF BPF_RB_FORCE_WAKEUP is specified in *flags*, notification of
+ * 		new data availability is sent unconditionally.
+ * 	Return
+ * 		Nothing. Always succeeds.
+ *
+ * void bpf_ringbuf_discard(void *data, u64 flags)
+ * 	Description
+ * 		Discard reserved ring buffer sample, pointed to by *data*.
+ * 		If BPF_RB_NO_WAKEUP is specified in *flags*, no notification of
+ * 		new data availability is sent.
+ * 		IF BPF_RB_FORCE_WAKEUP is specified in *flags*, notification of
+ * 		new data availability is sent unconditionally.
+ * 	Return
+ * 		Nothing. Always succeeds.
+ *
+ * u64 bpf_ringbuf_query(void *ringbuf, u64 flags)
+ *	Description
+ *		Query various characteristics of provided ring buffer. What
+ *		exactly is queries is determined by *flags*:
+ *		  - BPF_RB_AVAIL_DATA - amount of data not yet consumed;
+ *		  - BPF_RB_RING_SIZE - the size of ring buffer;
+ *		  - BPF_RB_CONS_POS - consumer position (can wrap around);
+ *		  - BPF_RB_PROD_POS - producer(s) position (can wrap around);
+ *		Data returned is just a momentary snapshots of actual values
+ *		and could be inaccurate, so this facility should be used to
+ *		power heuristics and for reporting, not to make 100% correct
+ *		calculation.
+ *	Return
+ *		Requested value, or 0, if flags are not recognized.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -3288,7 +3342,12 @@ union bpf_attr {
 	FN(seq_printf),			\
 	FN(seq_write),			\
 	FN(sk_cgroup_id),		\
-	FN(sk_ancestor_cgroup_id),
+	FN(sk_ancestor_cgroup_id),	\
+	FN(ringbuf_output),		\
+	FN(ringbuf_reserve),		\
+	FN(ringbuf_submit),		\
+	FN(ringbuf_discard),		\
+	FN(ringbuf_query),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
@@ -3398,6 +3457,29 @@ enum {
 	BPF_F_GET_BRANCH_RECORDS_SIZE	= (1ULL << 0),
 };
 
+/* BPF_FUNC_bpf_ringbuf_commit, BPF_FUNC_bpf_ringbuf_discard, and
+ * BPF_FUNC_bpf_ringbuf_output flags.
+ */
+enum {
+	BPF_RB_NO_WAKEUP		= (1ULL << 0),
+	BPF_RB_FORCE_WAKEUP		= (1ULL << 1),
+};
+
+/* BPF_FUNC_bpf_ringbuf_query flags */
+enum {
+	BPF_RB_AVAIL_DATA = 0,
+	BPF_RB_RING_SIZE = 1,
+	BPF_RB_CONS_POS = 2,
+	BPF_RB_PROD_POS = 3,
+};
+
+/* BPF ring buffer constants */
+enum {
+	BPF_RINGBUF_BUSY_BIT		= (1U << 31),
+	BPF_RINGBUF_DISCARD_BIT		= (1U << 30),
+	BPF_RINGBUF_HDR_SZ		= 8,
+};
+
 /* Mode for BPF_FUNC_skb_adjust_room helper. */
 enum bpf_adj_room_mode {
 	BPF_ADJ_ROOM_NET,

tools/testing/selftests/bpf/verifier/and.c

@@ -15,7 +15,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_48b = { 3 },
-	.errstr = "R0 max value is outside of the array range",
+	.errstr = "R0 max value is outside of the allowed memory range",
 	.result = REJECT,
 	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
 },
@@ -44,7 +44,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_48b = { 3 },
-	.errstr = "R0 max value is outside of the array range",
+	.errstr = "R0 max value is outside of the allowed memory range",
 	.result = REJECT,
 	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
 },

tools/testing/selftests/bpf/verifier/array_access.c

@@ -117,7 +117,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_48b = { 3 },
-	.errstr = "R0 min value is outside of the array range",
+	.errstr = "R0 min value is outside of the allowed memory range",
 	.result = REJECT,
 	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
 },
@@ -137,7 +137,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_48b = { 3 },
-	.errstr = "R0 unbounded memory access, make sure to bounds check any array access into a map",
+	.errstr = "R0 unbounded memory access, make sure to bounds check any such access",
 	.result = REJECT,
 	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
 },

tools/testing/selftests/bpf/verifier/bounds.c

@@ -20,7 +20,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_8b = { 3 },
-	.errstr = "R0 max value is outside of the array range",
+	.errstr = "R0 max value is outside of the allowed memory range",
 	.result = REJECT,
 },
 {
@@ -146,7 +146,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_8b = { 3 },
-	.errstr = "R0 min value is outside of the array range",
+	.errstr = "R0 min value is outside of the allowed memory range",
 	.result = REJECT
 },
 {
@@ -354,7 +354,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_8b = { 3 },
-	.errstr = "R0 max value is outside of the array range",
+	.errstr = "R0 max value is outside of the allowed memory range",
 	.result = REJECT
 },
 {

tools/testing/selftests/bpf/verifier/calls.c

@@ -105,7 +105,7 @@
 	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	.fixup_map_hash_8b = { 16 },
 	.result = REJECT,
-	.errstr = "R0 min value is outside of the array range",
+	.errstr = "R0 min value is outside of the allowed memory range",
 },
 {
 	"calls: overlapping caller/callee",

tools/testing/selftests/bpf/verifier/direct_value_access.c

@@ -68,7 +68,7 @@
 	},
 	.fixup_map_array_48b = { 1 },
 	.result = REJECT,
-	.errstr = "R1 min value is outside of the array range",
+	.errstr = "R1 min value is outside of the allowed memory range",
 },
 {
 	"direct map access, write test 7",
@@ -220,7 +220,7 @@
 	},
 	.fixup_map_array_small = { 1 },
 	.result = REJECT,
-	.errstr = "R1 min value is outside of the array range",
+	.errstr = "R1 min value is outside of the allowed memory range",
 },
 {
 	"direct map access, write test 19",

tools/testing/selftests/bpf/verifier/helper_access_var_len.c

@@ -318,7 +318,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_48b = { 4 },
-	.errstr = "R1 min value is outside of the array range",
+	.errstr = "R1 min value is outside of the allowed memory range",
 	.result = REJECT,
 	.prog_type = BPF_PROG_TYPE_TRACEPOINT,
 },

tools/testing/selftests/bpf/verifier/helper_value_access.c

@@ -280,7 +280,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_48b = { 3 },
-	.errstr = "R1 min value is outside of the array range",
+	.errstr = "R1 min value is outside of the allowed memory range",
 	.result = REJECT,
 	.prog_type = BPF_PROG_TYPE_TRACEPOINT,
 },
@@ -415,7 +415,7 @@
 	BPF_EXIT_INSN(),
 	},
 	.fixup_map_hash_48b = { 3 },
-	.errstr = "R1 min value is outside of the array range",
+	.errstr = "R1 min value is outside of the allowed memory range",
 	.result = REJECT,
 	.prog_type = BPF_PROG_TYPE_TRACEPOINT,
 },
@@ -926,7 +926,7 @@
 	},
 	.fixup_map_hash_16b = { 3, 10 },
 	.result = REJECT,
-	.errstr = "R2 unbounded memory access, make sure to bounds check any array access into a map",
+	.errstr = "R2 unbounded memory access, make sure to bounds check any such access",
 	.prog_type = BPF_PROG_TYPE_TRACEPOINT,
 },
 {

tools/testing/selftests/bpf/verifier/value_ptr_arith.c

@@ -50,7 +50,7 @@
 	.fixup_map_array_48b = { 8 },
 	.result = ACCEPT,
 	.result_unpriv = REJECT,
-	.errstr_unpriv = "R0 min value is outside of the array range",
+	.errstr_unpriv = "R0 min value is outside of the allowed memory range",
 	.retval = 1,
 },
 {
@@ -325,7 +325,7 @@
 	},
 	.fixup_map_array_48b = { 3 },
 	.result = REJECT,
-	.errstr = "R0 min value is outside of the array range",
+	.errstr = "R0 min value is outside of the allowed memory range",
 	.result_unpriv = REJECT,
 	.errstr_unpriv = "R0 pointer arithmetic of map value goes out of range",
 },
@@ -601,7 +601,7 @@
 	},
 	.fixup_map_array_48b = { 3 },
 	.result = REJECT,
-	.errstr = "R1 max value is outside of the array range",
+	.errstr = "R1 max value is outside of the allowed memory range",
 	.errstr_unpriv = "R1 pointer arithmetic of map value goes out of range",
 	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
 },
@@ -726,7 +726,7 @@
 	},
 	.fixup_map_array_48b = { 3 },
 	.result = REJECT,
-	.errstr = "R0 min value is outside of the array range",
+	.errstr = "R0 min value is outside of the allowed memory range",
 },
 {
 	"map access: value_ptr -= known scalar, 2",