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libbpf: Clean up and improve CO-RE reloc logging

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Add logging of local/target type kind (struct/union/typedef/etc). Preserve
unresolved root type ID (for cases of typedef). Improve the format of CO-RE
reloc spec output format to contain only relevant and succinct info.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200818223921.2911963-3-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-08-18 15:39:14 -07:00 • committed by Alexei Starovoitov
parent 81ba088902
commit 28b93c6449
4 changed files with 169 additions and 129 deletions
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78
tools/lib/bpf/libbpf_internal.h
View file

@ -138,6 +138,44 @@ struct btf_ext_info {
i < (sec)->num_info; \
i++, rec = (void *)rec + (seg)->rec_size)
/*
* The .BTF.ext ELF section layout defined as
* struct btf_ext_header
* func_info subsection
*
* The func_info subsection layout:
* record size for struct bpf_func_info in the func_info subsection
* struct btf_sec_func_info for section #1
* a list of bpf_func_info records for section #1
* where struct bpf_func_info mimics one in include/uapi/linux/bpf.h
* but may not be identical
* struct btf_sec_func_info for section #2
* a list of bpf_func_info records for section #2
* ......
*
* Note that the bpf_func_info record size in .BTF.ext may not
* be the same as the one defined in include/uapi/linux/bpf.h.
* The loader should ensure that record_size meets minimum
* requirement and pass the record as is to the kernel. The
* kernel will handle the func_info properly based on its contents.
*/
struct btf_ext_header {
__u16 magic;
__u8 version;
__u8 flags;
__u32 hdr_len;
/* All offsets are in bytes relative to the end of this header */
__u32 func_info_off;
__u32 func_info_len;
__u32 line_info_off;
__u32 line_info_len;
/* optional part of .BTF.ext header */
__u32 core_relo_off;
__u32 core_relo_len;
};
struct btf_ext {
union {
struct btf_ext_header *hdr;
@ -145,7 +183,7 @@ struct btf_ext {
};
struct btf_ext_info func_info;
struct btf_ext_info line_info;
struct btf_ext_info field_reloc_info;
struct btf_ext_info core_relo_info;
__u32 data_size;
};
@ -170,32 +208,34 @@ struct bpf_line_info_min {
__u32 line_col;
};
/* bpf_field_info_kind encodes which aspect of captured field has to be
* adjusted by relocations. Currently supported values are:
* - BPF_FIELD_BYTE_OFFSET: field offset (in bytes);
* - BPF_FIELD_EXISTS: field existence (1, if field exists; 0, otherwise);
/* bpf_core_relo_kind encodes which aspect of captured field/type/enum value
* has to be adjusted by relocations.
*/
enum bpf_field_info_kind {
enum bpf_core_relo_kind {
BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */
BPF_FIELD_BYTE_SIZE = 1,
BPF_FIELD_BYTE_SIZE = 1, /* field size in bytes */
BPF_FIELD_EXISTS = 2, /* field existence in target kernel */
BPF_FIELD_SIGNED = 3,
BPF_FIELD_LSHIFT_U64 = 4,
BPF_FIELD_RSHIFT_U64 = 5,
BPF_FIELD_SIGNED = 3, /* field signedness (0 - unsigned, 1 - signed) */
BPF_FIELD_LSHIFT_U64 = 4, /* bitfield-specific left bitshift */
BPF_FIELD_RSHIFT_U64 = 5, /* bitfield-specific right bitshift */
};
/* The minimum bpf_field_reloc checked by the loader
/* The minimum bpf_core_relo checked by the loader
*
* Field relocation captures the following data:
* CO-RE relocation captures the following data:
* - insn_off - instruction offset (in bytes) within a BPF program that needs
* its insn->imm field to be relocated with actual field info;
* - type_id - BTF type ID of the "root" (containing) entity of a relocatable
* field;
* type or field;
* - access_str_off - offset into corresponding .BTF string section. String
* itself encodes an accessed field using a sequence of field and array
* indicies, separated by colon (:). It's conceptually very close to LLVM's
* getelementptr ([0]) instruction's arguments for identifying offset to
* a field.
* interpretation depends on specific relocation kind:
* - for field-based relocations, string encodes an accessed field using
* a sequence of field and array indices, separated by colon (:). It's
* conceptually very close to LLVM's getelementptr ([0]) instruction's
* arguments for identifying offset to a field.
* - for type-based relocations, strings is expected to be just "0";
* - for enum value-based relocations, string contains an index of enum
* value within its enum type;
*
* Example to provide a better feel.
*
@ -226,11 +266,11 @@ enum bpf_field_info_kind {
*
* [0] https://llvm.org/docs/LangRef.html#getelementptr-instruction
*/
struct bpf_field_reloc {
struct bpf_core_relo {
__u32 insn_off;
__u32 type_id;
__u32 access_str_off;
enum bpf_field_info_kind kind;
enum bpf_core_relo_kind kind;
};
#endif /* __LIBBPF_LIBBPF_INTERNAL_H */