ebpf: add helper for obtaining current processor id

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;

Daniel Borkmann committed 11 years ago

Commit c04167c1 parent 03e69b55 files · +17 −0Browse files

Unified · Split

5 files

include/linux/bpf.h +1 −0
include/uapi/linux/bpf.h +1 −0
kernel/bpf/core.c +1 −0
kernel/bpf/helpers.c +12 −0
net/core/filter.c +2 −0

include/linux/bpf.h+1−0

@@ -155,5 +155,6 @@ extern const struct bpf_func_proto bpf_map_update_elem_proto; · 154 unmodified lines
155	extern const struct bpf_func_proto bpf_map_delete_elem_proto;	155	extern const struct bpf_func_proto bpf_map_delete_elem_proto;
156		156
157	extern const struct bpf_func_proto bpf_get_prandom_u32_proto;	157	extern const struct bpf_func_proto bpf_get_prandom_u32_proto;
		158	extern const struct bpf_func_proto bpf_get_smp_processor_id_proto;
158		159
159	#endif /* _LINUX_BPF_H */	160	#endif /* _LINUX_BPF_H */

include/uapi/linux/bpf.h+1−0

@@ -166,6 +166,7 @@ enum bpf_func_id { · 165 unmodified lines
166	BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */	166	BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */
167	BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */	167	BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
168	BPF_FUNC_get_prandom_u32, /* u32 prandom_u32(void) */	168	BPF_FUNC_get_prandom_u32, /* u32 prandom_u32(void) */
		169	BPF_FUNC_get_smp_processor_id, /* u32 raw_smp_processor_id(void) */
169	__BPF_FUNC_MAX_ID,	170	__BPF_FUNC_MAX_ID,
170	};	171	};
171		172

kernel/bpf/core.c+1−0

@@ -662,6 +662,7 @@ const struct bpf_func_proto bpf_map_update_elem_proto __weak; · 661 unmodified lines
662	const struct bpf_func_proto bpf_map_delete_elem_proto __weak;	662	const struct bpf_func_proto bpf_map_delete_elem_proto __weak;
663		663
664	const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;	664	const struct bpf_func_proto bpf_get_prandom_u32_proto __weak;
		665	const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak;
665		666
666	/* To execute LD_ABS/LD_IND instructions __bpf_prog_run() may call	667	/* To execute LD_ABS/LD_IND instructions __bpf_prog_run() may call
667	* skb_copy_bits(), so provide a weak definition of it for NET-less config.	668	* skb_copy_bits(), so provide a weak definition of it for NET-less config.

kernel/bpf/helpers.c+12−0

@@ -12,6 +12,7 @@ · 11 unmodified lines
12	#include <linux/bpf.h>	12	#include <linux/bpf.h>
13	#include <linux/rcupdate.h>	13	#include <linux/rcupdate.h>
14	#include <linux/random.h>	14	#include <linux/random.h>
		15	#include <linux/smp.h>
15		16
16	/* If kernel subsystem is allowing eBPF programs to call this function,	17	/* If kernel subsystem is allowing eBPF programs to call this function,
17	* inside its own verifier_ops->get_func_proto() callback it should return	18	* 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 = { · 81 unmodified lines
99	.gpl_only = false,	100	.gpl_only = false,
100	.ret_type = RET_INTEGER,	101	.ret_type = RET_INTEGER,
101	};	102	};
		103
		104	static u64 bpf_get_smp_processor_id(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
		105	{
		106	return raw_smp_processor_id();
		107	}
		108
		109	const struct bpf_func_proto bpf_get_smp_processor_id_proto = {
		110	.func = bpf_get_smp_processor_id,
		111	.gpl_only = false,
		112	.ret_type = RET_INTEGER,
		113	};

net/core/filter.c+2−0

 		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;
 	}

ebpf: add helper for obtaining current processor id

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