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Commit 740baecd authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

Merge branch 'btf-func-info' 

Martin KaFai Lau says:

====================
The BTF support was added to kernel by Commit 69b693f0
("bpf: btf: Introduce BPF Type Format (BTF)"), which introduced
.BTF section into ELF file and is primarily
used for map pretty print.
pahole is used to convert dwarf to BTF for ELF files.

This patch added func info support to the kernel so we can
get better ksym's for bpf function calls. Basically,
function call types are passed to kernel and the kernel
extract function names from these types in order to contruct ksym
for these functions.

The llvm patch at https://reviews.llvm.org/D53736


will generate .BTF section and one more section .BTF.ext.
The .BTF.ext section encodes function type
information. The following is a sample output for selftests
test_btf with file test_btf_haskv.o for translated insns
and jited insns respectively.

  $ bpftool prog dump xlated id 1
  int _dummy_tracepoint(struct dummy_tracepoint_args * arg):
     0: (85) call pc+2#bpf_prog_2dcecc18072623fc_test_long_fname_1
     1: (b7) r0 = 0
     2: (95) exit
  int test_long_fname_1(struct dummy_tracepoint_args * arg):
     3: (85) call pc+1#bpf_prog_89d64e4abf0f0126_test_long_fname_2
     4: (95) exit
  int test_long_fname_2(struct dummy_tracepoint_args * arg):
     5: (b7) r2 = 0
     6: (63) *(u32 *)(r10 -4) = r2
     7: (79) r1 = *(u64 *)(r1 +8)
     ...
     22: (07) r1 += 1
     23: (63) *(u32 *)(r0 +4) = r1
     24: (95) exit

  $ bpftool prog dump jited id 1
  int _dummy_tracepoint(struct dummy_tracepoint_args * arg):
  bpf_prog_b07ccb89267cf242__dummy_tracepoint:
     0:   push   %rbp
     1:   mov    %rsp,%rbp
    ......
    3c:   add    $0x28,%rbp
    40:   leaveq
    41:   retq

  int test_long_fname_1(struct dummy_tracepoint_args * arg):
  bpf_prog_2dcecc18072623fc_test_long_fname_1:
     0:   push   %rbp
     1:   mov    %rsp,%rbp
    ......
    3a:   add    $0x28,%rbp
    3e:   leaveq
    3f:   retq

  int test_long_fname_2(struct dummy_tracepoint_args * arg):
  bpf_prog_89d64e4abf0f0126_test_long_fname_2:
     0:   push   %rbp
     1:   mov    %rsp,%rbp
    ......
    80:   add    $0x28,%rbp
    84:   leaveq
    85:   retq

Changelogs:
  v4 -> v5:
    . Add back BTF_KIND_FUNC_PROTO as v1 did.  The difference
      is BTF_KIND_FUNC_PROTO cannot have t->name_off now.
      All param metadata is defined in BTF_KIND_FUNC_PROTO.
      BTF_KIND_FUNC must have t->name_off != 0 and t->type
      refers to a BTF_KIND_FUNC_PROTO.

      The above is the conclusion after the discussion between
      Edward Cree, Alexei, Daniel, Yonghong and Martin.
  v3 -> v4:
    . Remove BTF_KIND_FUNC_PROTO. BTF_KIND_FUNC is used for
      both function pointer and subprogram. The name_off field
      is used to distinguish both.
    . The record size is added to the func_info subsection
      in .BTF.ext to enable future extension.
    . The bpf_prog_info interface change to make it similar
      bpf_prog_load.
    . Related kernel and libbpf changes to accommodate the
      new .BTF.ext and kernel interface changes.
  v2 -> v3:
    . Removed kernel btf extern functions btf_type_id_func()
      and btf_get_name_by_id(). Instead, exposing existing
      functions btf_type_by_id() and btf_name_by_offset().
    . Added comments about ELF section .BTF.ext layout.
    . Better codes in btftool as suggested by Edward Cree.
  v1 -> v2:
    . Added missing sign-off.
    . Limited the func_name/struct_member_name length for validity test.
    . Removed/changed several verifier messages.
    . Modified several commit messages to remove line_off reference.
====================

Acked-by: default avatarEdward Cree <ecree@solarflare.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parents bbe5d311 254471e5

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__ */

include/uapi/linux/btf.h

+15 −3
Original line number Diff line number Diff line
@@ -40,7 +40,8 @@ struct btf_type { 
	/* "size" is used by INT, ENUM, STRUCT and UNION.

	 * "size" tells the size of the type it is describing.

	 *

	 * "type" is used by PTR, TYPEDEF, VOLATILE, CONST and RESTRICT.

	 * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,

	 * FUNC and FUNC_PROTO.

	 * "type" is a type_id referring to another type.

	 */

	union {
@@ -64,8 +65,10 @@ struct btf_type { 
#define BTF_KIND_VOLATILE	9	/* Volatile	*/

#define BTF_KIND_CONST		10	/* Const	*/

#define BTF_KIND_RESTRICT	11	/* Restrict	*/

#define BTF_KIND_MAX		11

#define NR_BTF_KINDS		12

#define BTF_KIND_FUNC		12	/* Function	*/

#define BTF_KIND_FUNC_PROTO	13	/* Function Proto	*/

#define BTF_KIND_MAX		13

#define NR_BTF_KINDS		14



/* For some specific BTF_KIND, "struct btf_type" is immediately

 * followed by extra data.
@@ -110,4 +113,13 @@ struct btf_member { 
	__u32	offset;	/* offset in bits */

};



/* BTF_KIND_FUNC_PROTO is followed by multiple "struct btf_param".

 * The exact number of btf_param is stored in the vlen (of the

 * info in "struct btf_type").

 */

struct btf_param {

	__u32	name_off;

	__u32	type;

};



#endif /* _UAPI__LINUX_BTF_H__ */