Commit 838e9690 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Introduce bpf_func_info 



This patch added interface to load a program with the following
additional information:
   . prog_btf_fd
   . func_info, func_info_rec_size and func_info_cnt
where func_info will provide function range and type_id
corresponding to each function.

The func_info_rec_size is introduced in the UAPI to specify
struct bpf_func_info size passed from user space. This
intends to make bpf_func_info structure growable in the future.
If the kernel gets a different bpf_func_info size from userspace,
it will try to handle user request with part of bpf_func_info
it can understand. In this patch, kernel can understand
  struct bpf_func_info {
       __u32   insn_offset;
       __u32   type_id;
  };
If user passed a bpf func_info record size of 16 bytes, the
kernel can still handle part of records with the above definition.

If verifier agrees with function range provided by the user,
the bpf_prog ksym for each function will use the func name
provided in the type_id, which is supposed to provide better
encoding as it is not limited by 16 bytes program name
limitation and this is better for bpf program which contains
multiple subprograms.

The bpf_prog_info interface is also extended to
return btf_id, func_info, func_info_rec_size and func_info_cnt
to userspace, so userspace can print out the function prototype
for each xlated function. The insn_offset in the returned
func_info corresponds to the insn offset for xlated functions.
With other jit related fields in bpf_prog_info, userspace can also
print out function prototypes for each jited function.

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 78a2540e

include/linux/bpf.h

+4 −1
Original line number Diff line number Diff line
@@ -316,6 +316,8 @@ struct bpf_prog_aux { 
	void *security;

#endif

	struct bpf_prog_offload *offload;

	struct btf *btf;

	u32 type_id; /* type id for this prog/func */

	union {

		struct work_struct work;

		struct rcu_head	rcu;
@@ -527,7 +529,8 @@ static inline void bpf_long_memcpy(void *dst, const void *src, u32 size) 
}



/* verify correctness of eBPF program */

int bpf_check(struct bpf_prog **fp, union bpf_attr *attr);

int bpf_check(struct bpf_prog **fp, union bpf_attr *attr,

	      union bpf_attr __user *uattr);

void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);



/* Map specifics */

include/linux/bpf_verifier.h

+1 −0
Original line number Diff line number Diff line
@@ -204,6 +204,7 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log) 
struct bpf_subprog_info {

	u32 start; /* insn idx of function entry point */

	u16 stack_depth; /* max. stack depth used by this function */

	u32 type_id; /* btf type_id for this subprog */

};



/* single container for all structs

include/linux/btf.h

+2 −0
Original line number Diff line number Diff line
@@ -46,5 +46,7 @@ void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj, 
		       struct seq_file *m);

int btf_get_fd_by_id(u32 id);

u32 btf_id(const struct btf *btf);

const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);

const char *btf_name_by_offset(const struct btf *btf, u32 offset);



#endif

include/uapi/linux/bpf.h

+13 −0
Original line number Diff line number Diff line
@@ -338,6 +338,10 @@ union bpf_attr { 
		 * (context accesses, allowed helpers, etc).

		 */

		__u32		expected_attach_type;

		__u32		prog_btf_fd;	/* fd pointing to BTF type data */

		__u32		func_info_rec_size;	/* userspace bpf_func_info size */

		__aligned_u64	func_info;	/* func info */

		__u32		func_info_cnt;	/* number of bpf_func_info records */

	};



	struct { /* anonymous struct used by BPF_OBJ_* commands */
@@ -2638,6 +2642,10 @@ struct bpf_prog_info { 
	__u32 nr_jited_func_lens;

	__aligned_u64 jited_ksyms;

	__aligned_u64 jited_func_lens;

	__u32 btf_id;

	__u32 func_info_rec_size;

	__aligned_u64 func_info;

	__u32 func_info_cnt;

} __attribute__((aligned(8)));



struct bpf_map_info {
@@ -2949,4 +2957,9 @@ struct bpf_flow_keys { 
	};

};



struct bpf_func_info {

	__u32	insn_offset;

	__u32	type_id;

};



#endif /* _UAPI__LINUX_BPF_H__ */

kernel/bpf/btf.c

+2 −2
Original line number Diff line number Diff line
@@ -474,7 +474,7 @@ static bool btf_name_valid_identifier(const struct btf *btf, u32 offset) 
	return !*src;

}



static const char *btf_name_by_offset(const struct btf *btf, u32 offset)

const char *btf_name_by_offset(const struct btf *btf, u32 offset)

{

	if (!offset)

		return "(anon)";
@@ -484,7 +484,7 @@ static const char *btf_name_by_offset(const struct btf *btf, u32 offset) 
		return "(invalid-name-offset)";

}



static const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)

const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)

{

	if (type_id > btf->nr_types)

		return NULL;

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