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;

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 50bf95e29a96f471afa88c5815c985513992b216..30bfd331882a520f953f03e79a05e64ea757b5bd 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -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 */

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1c2ca2b477c80172875e8ca48c1194bd7815fe7e..de1f63668daf50134c5b8b2de7173a7cd9b8faf0 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -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,
 };
 

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index c1dbbb5d289b65d0d661949b9008c878f5dfe8a7..4139a0f8b558e4e7db4f79adbd353c97c7fda553 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -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.

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 95eb59a045ea68fcad84a413eb52fcd11d3e6f5c..bd7f5988ed9cca0f4973388f68741444b0cbfcb8 100644 (file)
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -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,
+};

diff --git a/net/core/filter.c b/net/core/filter.c
index 4344db39af2e1038f23702a626a227d8d64aa4b2..33310eee613483398f35d44a33d67f537f0e883b 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -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;
        }