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PATCH New Daniel Borkmann 1 participant 3 messages Mar 14, 2015

Subsystems (5)
Networking Network drivers BPF BPF core +1 more subsystems
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Daniel Borkmann

author maintainer
#0 lore raw

v2 cover eBPF updates

Two small eBPF helper additions to better match up with ancillary classic BPF functionality.

Daniel Borkmann (2):
ebpf: add prandom helper for packet sampling
ebpf: add helper for obtaining current processor id

 include/linux/bpf.h      |  3 +++
 include/uapi/linux/bpf.h |  2 ++
 kernel/bpf/core.c        |  3 +++
 kernel/bpf/helpers.c     | 24 ++++++++++++++++++++++++
 net/core/filter.c        |  4 ++++
 5 files changed, 36 insertions(+)
Signature · 1 line
1.9.3
author maintainer
#1 lore raw

PATCH v2 1/2 ebpf: add prandom helper for packet sampling

This work is similar to commit 4cd3675ebf74 ("filter: added BPF random opcode") and adds a possibility for packet sampling in eBPF.

Currently, this is only possible in classic BPF and useful to combine sampling with f.e. packet sockets, possible also with tc.

Example function proto-type looks like:

  u32 (*prandom_u32)(void) = (void *)BPF_FUNC_get_prandom_u32;
Signed-off-by Daniel Borkmann <[email protected]>

---
v1->v2:
- Changed function name
- Only u32-wide result

 include/linux/bpf.h      |  2 ++
 include/uapi/linux/bpf.h |  1 +
 kernel/bpf/core.c        |  2 ++
 kernel/bpf/helpers.c     | 12 ++++++++++++
 net/core/filter.c        |  2 ++
 5 files changed, 19 insertions(+)
include/linux/bpf.h +2 -0
index 80f2e0f..50bf95e 100644
@@ -154,4 +154,6 @@ extern const struct bpf_func_proto bpf_map_lookup_elem_proto;
 extern const struct bpf_func_proto bpf_map_update_elem_proto;
 extern const struct bpf_func_proto bpf_map_delete_elem_proto;
 
+extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
+
 #endif /* _LINUX_BPF_H */
include/uapi/linux/bpf.h +1 -0
index 3fa1af8..1c2ca2b 100644
@@ -165,6 +165,7 @@ enum bpf_func_id {
 	BPF_FUNC_map_lookup_elem, /* void *map_lookup_elem(&map, &key) */
 	BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */
 	BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
+	BPF_FUNC_get_prandom_u32, /* u32 prandom_u32(void) */
 	__BPF_FUNC_MAX_ID,
 };
kernel/bpf/core.c +2 -0
index 50603ae..c1dbbb5d 100644
@@ -661,6 +661,8 @@ const struct bpf_func_proto bpf_map_lookup_elem_proto __weak;
 const struct bpf_func_proto bpf_map_update_elem_proto __weak;
 const struct bpf_func_proto bpf_map_delete_elem_proto __weak;
 
+const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
+
 /* To execute LD_ABS/LD_IND instructions __bpf_prog_run() may call
  * skb_copy_bits(), so provide a weak definition of it for NET-less config.
  */
kernel/bpf/helpers.c +12 -0
index a3c7701..95eb59a 100644
@@ -11,6 +11,7 @@
  */
 #include <linux/bpf.h>
 #include <linux/rcupdate.h>
+#include <linux/random.h>
 
 /* If kernel subsystem is allowing eBPF programs to call this function,
  * inside its own verifier_ops->get_func_proto() callback it should return

@@ -87,3 +88,14 @@ const struct bpf_func_proto bpf_map_delete_elem_proto = {
 	.arg1_type = ARG_CONST_MAP_PTR,
 	.arg2_type = ARG_PTR_TO_MAP_KEY,
 };
+
+static u64 bpf_get_prandom_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	return prandom_u32();
+}
+
+const struct bpf_func_proto bpf_get_prandom_u32_proto = {
+	.func		= bpf_get_prandom_u32,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+};
net/core/filter.c +2 -0
index 7a4eb70..4344db3 100644
@@ -1139,6 +1139,8 @@ sk_filter_func_proto(enum bpf_func_id func_id)
 		return &bpf_map_update_elem_proto;
 	case BPF_FUNC_map_delete_elem:
 		return &bpf_map_delete_elem_proto;
+	case BPF_FUNC_get_prandom_u32:
+		return &bpf_get_prandom_u32_proto;
 	default:
 		return NULL;
 	}
Signature · 1 line
1.9.3
author maintainer
#2 lore raw

PATCH v2 2/2 ebpf: add helper for obtaining current processor id

In reply to Daniel Borkmann

This patch adds the possibility to obtain raw_smp_processor_id() in eBPF. Currently, this is only possible in classic BPF where commit da2033c28226 ("filter: add SKF_AD_RXHASH and SKF_AD_CPU") has added facilities for this.

Perhaps most importantly, this would also allow us to track per CPU statistics with eBPF maps, or to implement a poor-man's per CPU data structure through eBPF maps.

Example function proto-type looks like:

  u32 (*smp_processor_id)(void) = (void *)BPF_FUNC_get_smp_processor_id;
Signed-off-by Daniel Borkmann <[email protected]>

---
v1->v2:
- Changed function name

 include/linux/bpf.h      |  1 +
 include/uapi/linux/bpf.h |  1 +
 kernel/bpf/core.c        |  1 +
 kernel/bpf/helpers.c     | 12 ++++++++++++
 net/core/filter.c        |  2 ++
 5 files changed, 17 insertions(+)
include/linux/bpf.h +1 -0
index 50bf95e..30bfd33 100644
@@ -155,5 +155,6 @@ extern const struct bpf_func_proto bpf_map_update_elem_proto;
 extern const struct bpf_func_proto bpf_map_delete_elem_proto;
 
 extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
+extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
 
 #endif /* _LINUX_BPF_H */
include/uapi/linux/bpf.h +1 -0
index 1c2ca2b..de1f636 100644
@@ -166,6 +166,7 @@ enum bpf_func_id {
 	BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */
 	BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
 	BPF_FUNC_get_prandom_u32, /* u32 prandom_u32(void) */
+	BPF_FUNC_get_smp_processor_id, /* u32 raw_smp_processor_id(void) */
 	__BPF_FUNC_MAX_ID,
 };
kernel/bpf/core.c +1 -0
index c1dbbb5d..4139a0f 100644
@@ -662,6 +662,7 @@ const struct bpf_func_proto bpf_map_update_elem_proto __weak;
 const struct bpf_func_proto bpf_map_delete_elem_proto __weak;
 
 const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
+const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
 
 /* To execute LD_ABS/LD_IND instructions __bpf_prog_run() may call
  * skb_copy_bits(), so provide a weak definition of it for NET-less config.
kernel/bpf/helpers.c +12 -0
index 95eb59a..bd7f598 100644
@@ -12,6 +12,7 @@
 #include <linux/bpf.h>
 #include <linux/rcupdate.h>
 #include <linux/random.h>
+#include <linux/smp.h>
 
 /* If kernel subsystem is allowing eBPF programs to call this function,
  * inside its own verifier_ops->get_func_proto() callback it should return

@@ -99,3 +100,14 @@ const struct bpf_func_proto bpf_get_prandom_u32_proto = {
 	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 };
+
+static u64 bpf_get_smp_processor_id(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	return raw_smp_processor_id();
+}
+
+const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
+	.func		= bpf_get_smp_processor_id,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+};
net/core/filter.c +2 -0
index 4344db3..33310ee 100644
@@ -1141,6 +1141,8 @@ sk_filter_func_proto(enum bpf_func_id func_id)
 		return &bpf_map_delete_elem_proto;
 	case BPF_FUNC_get_prandom_u32:
 		return &bpf_get_prandom_u32_proto;
+	case BPF_FUNC_get_smp_processor_id:
+		return &bpf_get_smp_processor_id_proto;
 	default:
 		return NULL;
 	}
Signature · 1 line
1.9.3