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bpf: Add bpf_skc_to_unix_sock() helper

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The helper is used in tracing programs to cast a socket
pointer to a unix_sock pointer.
The return value could be NULL if the casting is illegal.

Suggested-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211021134752.1223426-2-hengqi.chen@gmail.com
This commit is contained in:
Hengqi Chen 2021-10-21 21:47:51 +08:00 committed by Alexei Starovoitov
parent 44ce0ac11e
commit 9eeb3aa33a
6 changed files with 42 additions and 0 deletions
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1
include/linux/bpf.h
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@ -2093,6 +2093,7 @@ extern const struct bpf_func_proto bpf_skc_to_tcp_sock_proto;
extern const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto;
extern const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto;
extern const struct bpf_func_proto bpf_skc_to_udp6_sock_proto;
extern const struct bpf_func_proto bpf_skc_to_unix_sock_proto;
extern const struct bpf_func_proto bpf_copy_from_user_proto;
extern const struct bpf_func_proto bpf_snprintf_btf_proto;
extern const struct bpf_func_proto bpf_snprintf_proto;

7
include/uapi/linux/bpf.h
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@ -4909,6 +4909,12 @@ union bpf_attr {
* Return
* The number of bytes written to the buffer, or a negative error
* in case of failure.
*
* struct unix_sock *bpf_skc_to_unix_sock(void *sk)
* Description
* Dynamically cast a *sk* pointer to a *unix_sock* pointer.
* Return
* *sk* if casting is valid, or **NULL** otherwise.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -5089,6 +5095,7 @@ union bpf_attr {
FN(task_pt_regs), \
FN(get_branch_snapshot), \
FN(trace_vprintk), \
FN(skc_to_unix_sock), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper

2
kernel/trace/bpf_trace.c
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@ -1608,6 +1608,8 @@ 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_skc_to_unix_sock:
return &bpf_skc_to_unix_sock_proto;
case BPF_FUNC_sk_storage_get:
return &bpf_sk_storage_get_tracing_proto;
case BPF_FUNC_sk_storage_delete:

23
net/core/filter.c
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@ -10723,6 +10723,26 @@ const struct bpf_func_proto bpf_skc_to_udp6_sock_proto = {
.ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_UDP6],
};
BPF_CALL_1(bpf_skc_to_unix_sock, struct sock *, sk)
{
/* unix_sock type is not generated in dwarf and hence btf,
* trigger an explicit type generation here.
*/
BTF_TYPE_EMIT(struct unix_sock);
if (sk && sk_fullsock(sk) && sk->sk_family == AF_UNIX)
return (unsigned long)sk;
return (unsigned long)NULL;
}
const struct bpf_func_proto bpf_skc_to_unix_sock_proto = {
.func = bpf_skc_to_unix_sock,
.gpl_only = false,
.ret_type = RET_PTR_TO_BTF_ID_OR_NULL,
.arg1_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
.ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_UNIX],
};
BPF_CALL_1(bpf_sock_from_file, struct file *, file)
{
return (unsigned long)sock_from_file(file);
@ -10762,6 +10782,9 @@ bpf_sk_base_func_proto(enum bpf_func_id func_id)
case BPF_FUNC_skc_to_udp6_sock:
func = &bpf_skc_to_udp6_sock_proto;
break;
case BPF_FUNC_skc_to_unix_sock:
func = &bpf_skc_to_unix_sock_proto;
break;
default:
return bpf_base_func_proto(func_id);
}

2
scripts/bpf_doc.py
View File

@ -537,6 +537,7 @@ class PrinterHelpers(Printer):
'struct tcp_timewait_sock',
'struct tcp_request_sock',
'struct udp6_sock',
'struct unix_sock',
'struct task_struct',
'struct __sk_buff',
@ -589,6 +590,7 @@ class PrinterHelpers(Printer):
'struct tcp_timewait_sock',
'struct tcp_request_sock',
'struct udp6_sock',
'struct unix_sock',
'struct task_struct',
'struct path',
'struct btf_ptr',

7
tools/include/uapi/linux/bpf.h
View File

@ -4909,6 +4909,12 @@ union bpf_attr {
* Return
* The number of bytes written to the buffer, or a negative error
* in case of failure.
*
* struct unix_sock *bpf_skc_to_unix_sock(void *sk)
* Description
* Dynamically cast a *sk* pointer to a *unix_sock* pointer.
* Return
* *sk* if casting is valid, or **NULL** otherwise.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -5089,6 +5095,7 @@ union bpf_attr {
FN(task_pt_regs), \
FN(get_branch_snapshot), \
FN(trace_vprintk), \
FN(skc_to_unix_sock), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper