Commit c04167ce authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

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
da2033c2 ("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: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 03e69b50

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -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
Original line number Diff line number Diff line
@@ -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
Original line number Diff line number Diff line
@@ -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
Original line number Diff line number Diff line
@@ -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
Original line number Diff line number Diff line
@@ -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;

	}

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