Commit 8e4597c6 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
Browse files

bpf: Allow using bpf_sk_storage in FENTRY/FEXIT/RAW_TP 



This patch enables the FENTRY/FEXIT/RAW_TP tracing program to use
the bpf_sk_storage_(get|delete) helper, so those tracing programs
can access the sk's bpf_local_storage and the later selftest
will show some examples.

The bpf_sk_storage is currently used in bpf-tcp-cc, tc,
cg sockops...etc which is running either in softirq or
task context.

This patch adds bpf_sk_storage_get_tracing_proto and
bpf_sk_storage_delete_tracing_proto.  They will check
in runtime that the helpers can only be called when serving
softirq or running in a task context.  That should enable
most common tracing use cases on sk.

During the load time, the new tracing_allowed() function
will ensure the tracing prog using the bpf_sk_storage_(get|delete)
helper is not tracing any bpf_sk_storage*() function itself.
The sk is passed as "void *" when calling into bpf_local_storage.

This patch only allows tracing a kernel function.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201112211313.2587383-1-kafai@fb.com
parent e794bfdd

include/net/bpf_sk_storage.h

+2 −0
Original line number Diff line number Diff line
@@ -20,6 +20,8 @@ void bpf_sk_storage_free(struct sock *sk); 


extern const struct bpf_func_proto bpf_sk_storage_get_proto;

extern const struct bpf_func_proto bpf_sk_storage_delete_proto;

extern const struct bpf_func_proto bpf_sk_storage_get_tracing_proto;

extern const struct bpf_func_proto bpf_sk_storage_delete_tracing_proto;



struct bpf_local_storage_elem;

struct bpf_sk_storage_diag;

kernel/trace/bpf_trace.c

+5 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/syscalls.h>

#include <linux/error-injection.h>

#include <linux/btf_ids.h>

#include <net/bpf_sk_storage.h>



#include <uapi/linux/bpf.h>

#include <uapi/linux/btf.h>
@@ -1735,6 +1736,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
		return &bpf_skc_to_tcp_request_sock_proto;

	case BPF_FUNC_skc_to_udp6_sock:

		return &bpf_skc_to_udp6_sock_proto;

	case BPF_FUNC_sk_storage_get:

		return &bpf_sk_storage_get_tracing_proto;

	case BPF_FUNC_sk_storage_delete:

		return &bpf_sk_storage_delete_tracing_proto;

#endif

	case BPF_FUNC_seq_printf:

		return prog->expected_attach_type == BPF_TRACE_ITER ?

net/core/bpf_sk_storage.c

+74 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include <linux/types.h>

#include <linux/spinlock.h>

#include <linux/bpf.h>

#include <linux/btf.h>

#include <linux/btf_ids.h>

#include <linux/bpf_local_storage.h>

#include <net/bpf_sk_storage.h>
@@ -378,6 +379,79 @@ const struct bpf_func_proto bpf_sk_storage_delete_proto = { 
	.arg2_type	= ARG_PTR_TO_BTF_ID_SOCK_COMMON,

};



static bool bpf_sk_storage_tracing_allowed(const struct bpf_prog *prog)

{

	const struct btf *btf_vmlinux;

	const struct btf_type *t;

	const char *tname;

	u32 btf_id;



	if (prog->aux->dst_prog)

		return false;



	/* Ensure the tracing program is not tracing

	 * any bpf_sk_storage*() function and also

	 * use the bpf_sk_storage_(get|delete) helper.

	 */

	switch (prog->expected_attach_type) {

	case BPF_TRACE_RAW_TP:

		/* bpf_sk_storage has no trace point */

		return true;

	case BPF_TRACE_FENTRY:

	case BPF_TRACE_FEXIT:

		btf_vmlinux = bpf_get_btf_vmlinux();

		btf_id = prog->aux->attach_btf_id;

		t = btf_type_by_id(btf_vmlinux, btf_id);

		tname = btf_name_by_offset(btf_vmlinux, t->name_off);

		return !!strncmp(tname, "bpf_sk_storage",

				 strlen("bpf_sk_storage"));

	default:

		return false;

	}



	return false;

}



BPF_CALL_4(bpf_sk_storage_get_tracing, struct bpf_map *, map, struct sock *, sk,

	   void *, value, u64, flags)

{

	if (!in_serving_softirq() && !in_task())

		return (unsigned long)NULL;



	return (unsigned long)____bpf_sk_storage_get(map, sk, value, flags);

}



BPF_CALL_2(bpf_sk_storage_delete_tracing, struct bpf_map *, map,

	   struct sock *, sk)

{

	if (!in_serving_softirq() && !in_task())

		return -EPERM;



	return ____bpf_sk_storage_delete(map, sk);

}



const struct bpf_func_proto bpf_sk_storage_get_tracing_proto = {

	.func		= bpf_sk_storage_get_tracing,

	.gpl_only	= false,

	.ret_type	= RET_PTR_TO_MAP_VALUE_OR_NULL,

	.arg1_type	= ARG_CONST_MAP_PTR,

	.arg2_type	= ARG_PTR_TO_BTF_ID,

	.arg2_btf_id	= &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],

	.arg3_type	= ARG_PTR_TO_MAP_VALUE_OR_NULL,

	.arg4_type	= ARG_ANYTHING,

	.allowed	= bpf_sk_storage_tracing_allowed,

};



const struct bpf_func_proto bpf_sk_storage_delete_tracing_proto = {

	.func		= bpf_sk_storage_delete_tracing,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_CONST_MAP_PTR,

	.arg2_type	= ARG_PTR_TO_BTF_ID,

	.arg2_btf_id	= &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],

	.allowed	= bpf_sk_storage_tracing_allowed,

};



struct bpf_sk_storage_diag {

	u32 nr_maps;

	struct bpf_map *maps[];

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