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This patch does the followings:
1. Limit BTF_MAX_TYPES and BTF_MAX_NAME_OFFSET to 64k. We can
raise it later.
2. Remove the BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID. They are
currently encoded at the highest bit of a u32.
It is because the current use case does not require supporting
parent type (i.e type_id referring to a type in another BTF file).
It also does not support referring to a string in ELF.
The BTF_TYPE_PARENT and BTF_STR_TBL_ELF_ID checks are replaced
by BTF_TYPE_ID_CHECK and BTF_STR_OFFSET_CHECK which are
defined in btf.c instead of uapi/linux/btf.h.
3. Limit the BTF_INFO_KIND from 5 bits to 4 bits which is enough.
There is unused bits headroom if we ever needed it later.
4. The root bit in BTF_INFO is also removed because it is not
used in the current use case.
5. Remove BTF_INT_VARARGS since func type is not supported now.
The BTF_INT_ENCODING is limited to 4 bits instead of 8 bits.
The above can be added back later because the verifier
ensures the unused bits are zeros.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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There are currently unused section descriptions in the btf_header. Those
sections are here to support future BTF use cases. For example, the
func section (func_off) is to support function signature (e.g. the BPF
prog function signature).
Instead of spelling out all potential sections up-front in the btf_header.
This patch makes changes to btf_header such that extending it (e.g. adding
a section) is possible later. The unused ones can be removed for now and
they can be added back later.
This patch:
1. adds a hdr_len to the btf_header. It will allow adding
sections (and other info like parent_label and parent_name)
later. The check is similar to the existing bpf_attr.
If a user passes in a longer hdr_len, the kernel
ensures the extra tailing bytes are 0.
2. allows the section order in the BTF object to be
different from its sec_off order in btf_header.
3. each sec_off is followed by a sec_len. It must not have gap or
overlapping among sections.
The string section is ensured to be at the end due to the 4 bytes
alignment requirement of the type section.
The above changes will allow enough flexibility to
add new sections (and other info) to the btf_header later.
This patch also removes an unnecessary !err check
at the end of btf_parse().
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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This patch cleans up btf.h in uapi:
1) Rename "name" to "name_off" to better reflect it is an offset to the
string section instead of a char array.
2) Remove unused value BTF_FLAGS_COMPR and BTF_MAGIC_SWAP
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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This patch introduces BPF type Format (BTF).
BTF (BPF Type Format) is the meta data format which describes
the data types of BPF program/map. Hence, it basically focus
on the C programming language which the modern BPF is primary
using. The first use case is to provide a generic pretty print
capability for a BPF map.
BTF has its root from CTF (Compact C-Type format). To simplify
the handling of BTF data, BTF removes the differences between
small and big type/struct-member. Hence, BTF consistently uses u32
instead of supporting both "one u16" and "two u32 (+padding)" in
describing type and struct-member.
It also raises the number of types (and functions) limit
from 0x7fff to 0x7fffffff.
Due to the above changes, the format is not compatible to CTF.
Hence, BTF starts with a new BTF_MAGIC and version number.
This patch does the first verification pass to the BTF. The first
pass checks:
1. meta-data size (e.g. It does not go beyond the total btf's size)
2. name_offset is valid
3. Each BTF_KIND (e.g. int, enum, struct....) does its
own check of its meta-data.
Some other checks, like checking a struct's member is referring
to a valid type, can only be done in the second pass. The second
verification pass will be implemented in the next patch.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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