kernel/tools/lib/bpf/btf.c, branch linux-5.1.y

libbpf: fix btf_dedup equivalence check handling of different kinds

2019-03-27T15:01:24Z

btf_dedup_is_equiv() used to compare btf_type->info fields, before doing kind-specific equivalence check. This comparsion implicitly verified that candidate and canonical types are of the same kind. With enum fwd resolution logic this check couldn't be done generically anymore, as for enums info contains vlen, which differs between enum fwd and fully-defined enum, so this check was subsumed by kind-specific equivalence checks. This change caused btf_dedup_is_equiv() to let through VOID vs other types check to reach switch, which was never meant to be handing VOID kind, as VOID kind is always pre-resolved to itself and is only equivalent to itself, which is checked early in btf_dedup_is_equiv(). This change adds back BTF kind equality check in place of more generic btf_type->info check, still defering further kind-specific checks to a per-kind switch. Fixes: 9768095ba97c ("btf: resolve enum fwds in btf_dedup") Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

btf: resolve enum fwds in btf_dedup

2019-03-14T20:53:18Z

GCC and clang support enum forward declarations as an extension. Such forward-declared enums will be represented as normal BTF_KIND_ENUM types with vlen=0. This patch adds ability to resolve such enums to their corresponding fully defined enums. This helps to avoid duplicated BTF type graphs which only differ by some types referencing forward-declared enum vs full enum. One such example in kernel is enum irqchip_irq_state, defined in include/linux/interrupt.h and forward-declared in include/linux/irq.h. This causes entire struct task_struct and all referenced types to be duplicated in btf_dedup output. This patch eliminates such duplication cases. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

btf: fix bug with resolving STRUCT/UNION into corresponding FWD

2019-03-01T00:31:48Z

When checking available canonical candidates for struct/union algorithm utilizes btf_dedup_is_equiv to determine if candidate is suitable. This check is not enough when candidate is corresponding FWD for that struct/union, because according to equivalence logic they are equivalent. When it so happens that FWD and STRUCT/UNION end in hashing to the same bucket, it's possible to create remapping loop from FWD to STRUCT and STRUCT to same FWD, which will cause btf_dedup() to loop forever. This patch fixes the issue by additionally checking that type and canonical candidate are strictly equal (utilizing btf_equal_struct). Fixes: d5caef5b5655 ("btf: add BTF types deduplication algorithm") Reported-by: Arnaldo Carvalho de Melo Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann

btf: allow to customize dedup hash table size

2019-03-01T00:31:47Z

Default size of dedup table (16k) is good enough for most binaries, even typical vmlinux images. But there are cases of binaries with huge amount of BTF types (e.g., allyesconfig variants of kernel), which benefit from having bigger dedup table size to lower amount of unnecessary hash collisions. Tools like pahole, thus, can tune this parameter to reach optimal performance. This change also serves double purpose of allowing tests to force hash collisions to test some corner cases, used in follow up patch. Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Daniel Borkmann

tools/libbpf: signedness bug in btf_dedup_ref_type()

2019-02-28T23:56:06Z

The "ref_type_id" variable needs to be signed for the error handling to work. Fixes: d5caef5b5655 ("btf: add BTF types deduplication algorithm") Signed-off-by: Dan Carpenter Acked-by: Andrii Nakryiko Acked-by: Song Liu Signed-off-by: Daniel Borkmann

tools/libbpf: support bigger BTF data sizes

2019-02-17T02:47:18Z

While it's understandable why kernel limits number of BTF types to 65535 and size of string section to 64KB, in libbpf as user-space library it's too restrictive. E.g., pahole converting DWARF to BTF type information for Linux kernel generates more than 3 million BTF types and more than 3MB of strings, before deduplication. So to allow btf__dedup() to do its work, we need to be able to load bigger BTF sections using btf__new(). Singed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

tools/bpf: replace bzero with memset

2019-02-14T23:31:39Z

bzero() call is deprecated and superseded by memset(). Signed-off-by: Andrii Nakryiko Reported-by: David Laight Acked-by: Martin KaFai Lau Signed-off-by: Alexei Starovoitov

tools/bpf: remove btf__get_strings() superseded by raw data API

2019-02-08T20:04:13Z

Now that we have btf__get_raw_data() it's trivial for tests to iterate over all strings for testing purposes, which eliminates the need for btf__get_strings() API. Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Alexei Starovoitov

btf: expose API to work with raw btf_ext data

2019-02-08T20:04:13Z

This patch changes struct btf_ext to retain original data in sequential block of memory, which makes it possible to expose btf_ext__get_raw_data() interface similar to btf__get_raw_data(), allowing users of libbpf to get access to raw representation of .BTF.ext section. Signed-off-by: Andrii Nakryiko Acked-by: Yonghong Song Signed-off-by: Alexei Starovoitov

btf: expose API to work with raw btf data

2019-02-08T20:04:13Z

This patch exposes new API btf__get_raw_data() that allows to get a copy of raw BTF data out of struct btf. This is useful for external programs that need to manipulate raw data, e.g., pahole using btf__dedup() to deduplicate BTF type info and then writing it back to file. Signed-off-by: Andrii Nakryiko Acked-by: Song Liu Signed-off-by: Alexei Starovoitov