diff mbox series

[bpf-next,v4,3/6] bpf: Dynptr support for ring buffers

Message ID 20220509224257.3222614-4-joannelkoong@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Dynamic pointers | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1822 this patch: 1822
netdev/cc_maintainers warning 6 maintainers not CCed: netdev@vger.kernel.org kafai@fb.com john.fastabend@gmail.com yhs@fb.com kpsingh@kernel.org songliubraving@fb.com
netdev/build_clang success Errors and warnings before: 198 this patch: 198
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1832 this patch: 1832
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns WARNING: line length of 84 exceeds 80 columns WARNING: line length of 94 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-PR fail merge-conflict
bpf/vmtest-bpf-next-VM_Test-1 success Logs for Kernel LATEST on ubuntu-latest + selftests
bpf/vmtest-bpf-next-VM_Test-2 success Logs for Kernel LATEST on z15 + selftests

Commit Message

Joanne Koong May 9, 2022, 10:42 p.m. UTC 
Currently, our only way of writing dynamically-sized data into a ring
buffer is through bpf_ringbuf_output but this incurs an extra memcpy
cost. bpf_ringbuf_reserve + bpf_ringbuf_commit avoids this extra
memcpy, but it can only safely support reservation sizes that are
statically known since the verifier cannot guarantee that the bpf
program won’t access memory outside the reserved space.

The bpf_dynptr abstraction allows for dynamically-sized ring buffer
reservations without the extra memcpy.

There are 3 new APIs:

long bpf_ringbuf_reserve_dynptr(void *ringbuf, u32 size, u64 flags, struct bpf_dynptr *ptr);
void bpf_ringbuf_submit_dynptr(struct bpf_dynptr *ptr, u64 flags);
void bpf_ringbuf_discard_dynptr(struct bpf_dynptr *ptr, u64 flags);

These closely follow the functionalities of the original ringbuf APIs.
For example, all ringbuffer dynptrs that have been reserved must be
either submitted or discarded before the program exits.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/bpf.h            | 14 +++++-
 include/uapi/linux/bpf.h       | 35 +++++++++++++++
 kernel/bpf/helpers.c           |  6 +++
 kernel/bpf/ringbuf.c           | 78 ++++++++++++++++++++++++++++++++++
 kernel/bpf/verifier.c          | 16 ++++++-
 tools/include/uapi/linux/bpf.h | 35 +++++++++++++++
 6 files changed, 180 insertions(+), 4 deletions(-)

Comments

Andrii Nakryiko May 13, 2022, 9:02 p.m. UTC | #1 
On Mon, May 9, 2022 at 3:44 PM Joanne Koong <joannelkoong@gmail.com> wrote:
>
> Currently, our only way of writing dynamically-sized data into a ring
> buffer is through bpf_ringbuf_output but this incurs an extra memcpy
> cost. bpf_ringbuf_reserve + bpf_ringbuf_commit avoids this extra
> memcpy, but it can only safely support reservation sizes that are
> statically known since the verifier cannot guarantee that the bpf
> program won’t access memory outside the reserved space.
>
> The bpf_dynptr abstraction allows for dynamically-sized ring buffer
> reservations without the extra memcpy.
>
> There are 3 new APIs:
>
> long bpf_ringbuf_reserve_dynptr(void *ringbuf, u32 size, u64 flags, struct bpf_dynptr *ptr);
> void bpf_ringbuf_submit_dynptr(struct bpf_dynptr *ptr, u64 flags);
> void bpf_ringbuf_discard_dynptr(struct bpf_dynptr *ptr, u64 flags);
>
> These closely follow the functionalities of the original ringbuf APIs.
> For example, all ringbuffer dynptrs that have been reserved must be
> either submitted or discarded before the program exits.
>
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---

LGTM

Acked-by: Andrii Nakryiko <andrii@kernel.org>

>  include/linux/bpf.h            | 14 +++++-
>  include/uapi/linux/bpf.h       | 35 +++++++++++++++
>  kernel/bpf/helpers.c           |  6 +++
>  kernel/bpf/ringbuf.c           | 78 ++++++++++++++++++++++++++++++++++
>  kernel/bpf/verifier.c          | 16 ++++++-
>  tools/include/uapi/linux/bpf.h | 35 +++++++++++++++
>  6 files changed, 180 insertions(+), 4 deletions(-)
>

[...]
David Vernet May 16, 2022, 4:09 p.m. UTC | #2 
On Mon, May 09, 2022 at 03:42:54PM -0700, Joanne Koong wrote:
> Currently, our only way of writing dynamically-sized data into a ring
> buffer is through bpf_ringbuf_output but this incurs an extra memcpy
> cost. bpf_ringbuf_reserve + bpf_ringbuf_commit avoids this extra
> memcpy, but it can only safely support reservation sizes that are
> statically known since the verifier cannot guarantee that the bpf
> program won’t access memory outside the reserved space.
> 
> The bpf_dynptr abstraction allows for dynamically-sized ring buffer
> reservations without the extra memcpy.
> 
> There are 3 new APIs:
> 
> long bpf_ringbuf_reserve_dynptr(void *ringbuf, u32 size, u64 flags, struct bpf_dynptr *ptr);
> void bpf_ringbuf_submit_dynptr(struct bpf_dynptr *ptr, u64 flags);
> void bpf_ringbuf_discard_dynptr(struct bpf_dynptr *ptr, u64 flags);
> 
> These closely follow the functionalities of the original ringbuf APIs.
> For example, all ringbuffer dynptrs that have been reserved must be
> either submitted or discarded before the program exits.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>

Looks good!

Acked-by: David Vernet <void@manifault.com>
diff mbox series

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e078b8a911fe..8fbe739b0dec 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -394,10 +394,15 @@  enum bpf_type_flag {
 	/* DYNPTR points to dynamically allocated memory. */
 	DYNPTR_TYPE_MALLOC	= BIT(8 + BPF_BASE_TYPE_BITS),
 
-	__BPF_TYPE_LAST_FLAG	= DYNPTR_TYPE_MALLOC,
+	/* DYNPTR points to a ringbuf record. */
+	DYNPTR_TYPE_RINGBUF	= BIT(9 + BPF_BASE_TYPE_BITS),
+
+	__BPF_TYPE_FLAG_MAX,
+
+	__BPF_TYPE_LAST_FLAG	= __BPF_TYPE_FLAG_MAX - 1,
 };
 
-#define DYNPTR_TYPE_FLAG_MASK	DYNPTR_TYPE_MALLOC
+#define DYNPTR_TYPE_FLAG_MASK	(DYNPTR_TYPE_MALLOC | DYNPTR_TYPE_RINGBUF)
 
 /* Max number of base types. */
 #define BPF_BASE_TYPE_LIMIT	(1UL << BPF_BASE_TYPE_BITS)
@@ -2205,6 +2210,9 @@  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;
+extern const struct bpf_func_proto bpf_ringbuf_reserve_dynptr_proto;
+extern const struct bpf_func_proto bpf_ringbuf_submit_dynptr_proto;
+extern const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto;
 extern const struct bpf_func_proto bpf_skc_to_tcp6_sock_proto;
 extern const struct bpf_func_proto bpf_skc_to_tcp_sock_proto;
 extern const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto;
@@ -2372,6 +2380,8 @@  enum bpf_dynptr_type {
 	BPF_DYNPTR_TYPE_INVALID,
 	/* Memory allocated dynamically by the kernel for the dynptr */
 	BPF_DYNPTR_TYPE_MALLOC,
+	/* Underlying data is a ringbuf record */
+	BPF_DYNPTR_TYPE_RINGBUF,
 };
 
 /* Since the upper 8 bits of dynptr->size is reserved, the
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 5a87ed654016..679f960d2514 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5177,6 +5177,38 @@  union bpf_attr {
  *		After this operation, *ptr* will be an invalidated dynptr.
  *	Return
  *		Void.
+ *
+ * long bpf_ringbuf_reserve_dynptr(void *ringbuf, u32 size, u64 flags, struct bpf_dynptr *ptr)
+ *	Description
+ *		Reserve *size* bytes of payload in a ring buffer *ringbuf*
+ *		through the dynptr interface. *flags* must be 0.
+ *
+ *		Please note that a corresponding bpf_ringbuf_submit_dynptr or
+ *		bpf_ringbuf_discard_dynptr must be called on *ptr*, even if the
+ *		reservation fails. This is enforced by the verifier.
+ *	Return
+ *		0 on success, or a negative error in case of failure.
+ *
+ * void bpf_ringbuf_submit_dynptr(struct bpf_dynptr *ptr, u64 flags)
+ *	Description
+ *		Submit reserved ring buffer sample, pointed to by *data*,
+ *		through the dynptr interface. This is a no-op if the dynptr is
+ *		invalid/null.
+ *
+ *		For more information on *flags*, please see
+ *		'bpf_ringbuf_submit'.
+ *	Return
+ *		Nothing. Always succeeds.
+ *
+ * void bpf_ringbuf_discard_dynptr(struct bpf_dynptr *ptr, u64 flags)
+ *	Description
+ *		Discard reserved ring buffer sample through the dynptr
+ *		interface. This is a no-op if the dynptr is invalid/null.
+ *
+ *		For more information on *flags*, please see
+ *		'bpf_ringbuf_discard'.
+ *	Return
+ *		Nothing. Always succeeds.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5376,6 +5408,9 @@  union bpf_attr {
 	FN(kptr_xchg),			\
 	FN(dynptr_alloc),		\
 	FN(dynptr_put),			\
+	FN(ringbuf_reserve_dynptr),	\
+	FN(ringbuf_submit_dynptr),	\
+	FN(ringbuf_discard_dynptr),	\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index a4272e9239ea..2d6f2e28b580 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1513,6 +1513,12 @@  bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_ringbuf_discard_proto;
 	case BPF_FUNC_ringbuf_query:
 		return &bpf_ringbuf_query_proto;
+	case BPF_FUNC_ringbuf_reserve_dynptr:
+		return &bpf_ringbuf_reserve_dynptr_proto;
+	case BPF_FUNC_ringbuf_submit_dynptr:
+		return &bpf_ringbuf_submit_dynptr_proto;
+	case BPF_FUNC_ringbuf_discard_dynptr:
+		return &bpf_ringbuf_discard_dynptr_proto;
 	case BPF_FUNC_for_each_map_elem:
 		return &bpf_for_each_map_elem_proto;
 	case BPF_FUNC_loop:
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index 311264ab80c4..ded4faeca192 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -475,3 +475,81 @@  const struct bpf_func_proto bpf_ringbuf_query_proto = {
 	.arg1_type	= ARG_CONST_MAP_PTR,
 	.arg2_type	= ARG_ANYTHING,
 };
+
+BPF_CALL_4(bpf_ringbuf_reserve_dynptr, struct bpf_map *, map, u32, size, u64, flags,
+	   struct bpf_dynptr_kern *, ptr)
+{
+	struct bpf_ringbuf_map *rb_map;
+	void *sample;
+	int err;
+
+	if (unlikely(flags)) {
+		bpf_dynptr_set_null(ptr);
+		return -EINVAL;
+	}
+
+	err = bpf_dynptr_check_size(size);
+	if (err) {
+		bpf_dynptr_set_null(ptr);
+		return err;
+	}
+
+	rb_map = container_of(map, struct bpf_ringbuf_map, map);
+
+	sample = __bpf_ringbuf_reserve(rb_map->rb, size);
+	if (!sample) {
+		bpf_dynptr_set_null(ptr);
+		return -EINVAL;
+	}
+
+	bpf_dynptr_init(ptr, sample, BPF_DYNPTR_TYPE_RINGBUF, 0, size);
+
+	return 0;
+}
+
+const struct bpf_func_proto bpf_ringbuf_reserve_dynptr_proto = {
+	.func		= bpf_ringbuf_reserve_dynptr,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | MEM_UNINIT,
+};
+
+BPF_CALL_2(bpf_ringbuf_submit_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
+{
+	if (!ptr->data)
+		return 0;
+
+	bpf_ringbuf_commit(ptr->data, flags, false /* discard */);
+
+	bpf_dynptr_set_null(ptr);
+
+	return 0;
+}
+
+const struct bpf_func_proto bpf_ringbuf_submit_dynptr_proto = {
+	.func		= bpf_ringbuf_submit_dynptr,
+	.ret_type	= RET_VOID,
+	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
+	.arg2_type	= ARG_ANYTHING,
+};
+
+BPF_CALL_2(bpf_ringbuf_discard_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
+{
+	if (!ptr->data)
+		return 0;
+
+	bpf_ringbuf_commit(ptr->data, flags, true /* discard */);
+
+	bpf_dynptr_set_null(ptr);
+
+	return 0;
+}
+
+const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto = {
+	.func		= bpf_ringbuf_discard_dynptr,
+	.ret_type	= RET_VOID,
+	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
+	.arg2_type	= ARG_ANYTHING,
+};
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8cdedc776987..c17df5f17ba1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -676,6 +676,8 @@  static int arg_to_dynptr_type(enum bpf_arg_type arg_type)
 	switch (arg_type & DYNPTR_TYPE_FLAG_MASK) {
 	case DYNPTR_TYPE_MALLOC:
 		return BPF_DYNPTR_TYPE_MALLOC;
+	case DYNPTR_TYPE_RINGBUF:
+		return BPF_DYNPTR_TYPE_RINGBUF;
 	default:
 		return BPF_DYNPTR_TYPE_INVALID;
 	}
@@ -683,7 +685,7 @@  static int arg_to_dynptr_type(enum bpf_arg_type arg_type)
 
 static inline bool dynptr_type_refcounted(enum bpf_dynptr_type type)
 {
-	return type == BPF_DYNPTR_TYPE_MALLOC;
+	return type == BPF_DYNPTR_TYPE_MALLOC || type == BPF_DYNPTR_TYPE_RINGBUF;
 }
 
 static int mark_stack_slots_dynptr(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
@@ -6036,9 +6038,13 @@  static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			case DYNPTR_TYPE_MALLOC:
 				err_extra = "malloc ";
 				break;
+			case DYNPTR_TYPE_RINGBUF:
+				err_extra = "ringbuf ";
+				break;
 			default:
 				break;
 			}
+
 			verbose(env, "Expected an initialized %sdynptr as arg #%d\n",
 				err_extra, arg + BPF_REG_1);
 			return -EINVAL;
@@ -6164,7 +6170,10 @@  static int check_map_func_compatibility(struct bpf_verifier_env *env,
 	case BPF_MAP_TYPE_RINGBUF:
 		if (func_id != BPF_FUNC_ringbuf_output &&
 		    func_id != BPF_FUNC_ringbuf_reserve &&
-		    func_id != BPF_FUNC_ringbuf_query)
+		    func_id != BPF_FUNC_ringbuf_query &&
+		    func_id != BPF_FUNC_ringbuf_reserve_dynptr &&
+		    func_id != BPF_FUNC_ringbuf_submit_dynptr &&
+		    func_id != BPF_FUNC_ringbuf_discard_dynptr)
 			goto error;
 		break;
 	case BPF_MAP_TYPE_STACK_TRACE:
@@ -6280,6 +6289,9 @@  static int check_map_func_compatibility(struct bpf_verifier_env *env,
 	case BPF_FUNC_ringbuf_output:
 	case BPF_FUNC_ringbuf_reserve:
 	case BPF_FUNC_ringbuf_query:
+	case BPF_FUNC_ringbuf_reserve_dynptr:
+	case BPF_FUNC_ringbuf_submit_dynptr:
+	case BPF_FUNC_ringbuf_discard_dynptr:
 		if (map->map_type != BPF_MAP_TYPE_RINGBUF)
 			goto error;
 		break;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 5a87ed654016..679f960d2514 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5177,6 +5177,38 @@  union bpf_attr {
  *		After this operation, *ptr* will be an invalidated dynptr.
  *	Return
  *		Void.
+ *
+ * long bpf_ringbuf_reserve_dynptr(void *ringbuf, u32 size, u64 flags, struct bpf_dynptr *ptr)
+ *	Description
+ *		Reserve *size* bytes of payload in a ring buffer *ringbuf*
+ *		through the dynptr interface. *flags* must be 0.
+ *
+ *		Please note that a corresponding bpf_ringbuf_submit_dynptr or
+ *		bpf_ringbuf_discard_dynptr must be called on *ptr*, even if the
+ *		reservation fails. This is enforced by the verifier.
+ *	Return
+ *		0 on success, or a negative error in case of failure.
+ *
+ * void bpf_ringbuf_submit_dynptr(struct bpf_dynptr *ptr, u64 flags)
+ *	Description
+ *		Submit reserved ring buffer sample, pointed to by *data*,
+ *		through the dynptr interface. This is a no-op if the dynptr is
+ *		invalid/null.
+ *
+ *		For more information on *flags*, please see
+ *		'bpf_ringbuf_submit'.
+ *	Return
+ *		Nothing. Always succeeds.
+ *
+ * void bpf_ringbuf_discard_dynptr(struct bpf_dynptr *ptr, u64 flags)
+ *	Description
+ *		Discard reserved ring buffer sample through the dynptr
+ *		interface. This is a no-op if the dynptr is invalid/null.
+ *
+ *		For more information on *flags*, please see
+ *		'bpf_ringbuf_discard'.
+ *	Return
+ *		Nothing. Always succeeds.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5376,6 +5408,9 @@  union bpf_attr {
 	FN(kptr_xchg),			\
 	FN(dynptr_alloc),		\
 	FN(dynptr_put),			\
+	FN(ringbuf_reserve_dynptr),	\
+	FN(ringbuf_submit_dynptr),	\
+	FN(ringbuf_discard_dynptr),	\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper