kernel/linux.git/tools/lib/bpf/libbpf_internal.h, branch v6.12.80

libbpf: Split BTF relocation

2024-06-17T21:38:31+00:00

Map distilled base BTF type ids referenced in split BTF and their references to the base BTF passed in, and if the mapping succeeds, reparent the split BTF to the base BTF. Relocation is done by first verifying that distilled base BTF only consists of named INT, FLOAT, ENUM, FWD, STRUCT and UNION kinds; then we sort these to speed lookups. Once sorted, the base BTF is iterated, and for each relevant kind we check for an equivalent in distilled base BTF. When found, the mapping from distilled -> base BTF id and string offset is recorded. In establishing mappings, we need to ensure we check STRUCT/UNION size when the STRUCT/UNION is embedded in a split BTF STRUCT/UNION, and when duplicate names exist for the same STRUCT/UNION. Otherwise size is ignored in matching STRUCT/UNIONs. Once all mappings are established, we can update type ids and string offsets in split BTF and reparent it to the new base. Signed-off-by: Alan Maguire Signed-off-by: Andrii Nakryiko Acked-by: Eduard Zingerman Link: https://lore.kernel.org/bpf/20240613095014.357981-4-alan.maguire@oracle.com

libbpf: Remove callback-based type/string BTF field visitor helpers

2024-06-05T14:54:45+00:00

Now that all libbpf/bpftool code switched to btf_field_iter, remove btf_type_visit_type_ids() and btf_type_visit_str_offs() callback-based helpers as not needed anymore. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Tested-by: Alan Maguire Acked-by: Eduard Zingerman Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/20240605001629.4061937-6-andrii@kernel.org

libbpf: Make use of BTF field iterator in BPF linker code

2024-06-05T14:54:32+00:00

Switch all BPF linker code dealing with iterating BTF type ID and string offset fields to new btf_field_iter facilities. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Tested-by: Alan Maguire Acked-by: Eduard Zingerman Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/20240605001629.4061937-3-andrii@kernel.org

libbpf: Add BTF field iterator

2024-06-05T14:54:26+00:00

Implement iterator-based type ID and string offset BTF field iterator. This is used extensively in BTF-handling code and BPF linker code for various sanity checks, rewriting IDs/offsets, etc. Currently this is implemented as visitor pattern calling custom callbacks, which makes the logic (especially in simple cases) unnecessarily obscure and harder to follow. Having equivalent functionality using iterator pattern makes for simpler to understand and maintain code. As we add more code for BTF processing logic in libbpf, it's best to switch to iterator pattern before adding more callback-based code. The idea for iterator-based implementation is to record offsets of necessary fields within fixed btf_type parts (which should be iterated just once), and, for kinds that have multiple members (based on vlen field), record where in each member necessary fields are located. Generic iteration code then just keeps track of last offset that was returned and handles N members correctly. Return type is just u32 pointer, where NULL is returned when all relevant fields were already iterated. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Tested-by: Alan Maguire Acked-by: Eduard Zingerman Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/20240605001629.4061937-2-andrii@kernel.org

libbpf: keep FD_CLOEXEC flag when dup()'ing FD

2024-06-01T03:35:55+00:00

Make sure to preserve and/or enforce FD_CLOEXEC flag on duped FDs. Use dup3() with O_CLOEXEC flag for that. Without this fix libbpf effectively clears FD_CLOEXEC flag on each of BPF map/prog FD, which is definitely not the right or expected behavior. Reported-by: Lennart Poettering Fixes: bc308d011ab8 ("libbpf: call dup2() syscall directly") Signed-off-by: Andrii Nakryiko Acked-by: Jiri Olsa Link: https://lore.kernel.org/r/20240529223239.504241-1-andrii@kernel.org Signed-off-by: Alexei Starovoitov

libbpf: Mark libbpf_kallsyms_parse static function

2024-03-29T01:31:41+00:00

Currently libbpf_kallsyms_parse() function is declared as a global function but actually it is not a API and there is no external users in bpftool/bpf-selftests. So let us mark the function as static. Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20240326041453.1197949-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov

libbpf: Rewrite btf datasec names starting from '?'

2024-03-06T23:18:16+00:00

Optional struct_ops maps are defined using question mark at the start of the section name, e.g.: SEC("?.struct_ops") struct test_ops optional_map = { ... }; This commit teaches libbpf to detect if kernel allows '?' prefix in datasec names, and if it doesn't then to rewrite such names by replacing '?' with '_', e.g.: DATASEC ?.struct_ops -> DATASEC _.struct_ops Signed-off-by: Eduard Zingerman Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20240306104529.6453-13-eddyz87@gmail.com

libbpf: integrate __arg_ctx feature detector into kernel_supports()

2024-01-29T20:34:13+00:00

Now that feature detection code is in bpf-next tree, integrate __arg_ctx kernel-side support into kernel_supports() framework. Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20240125205510.3642094-2-andrii@kernel.org Signed-off-by: Alexei Starovoitov

libbpf: Fix faccessat() usage on Android

2024-01-29T15:17:44+00:00

Android implementation of libc errors out with -EINVAL in faccessat() if passed AT_EACCESS ([0]), this leads to ridiculous issue with libbpf refusing to load /sys/kernel/btf/vmlinux on Androids ([1]). Fix by detecting Android and redefining AT_EACCESS to 0, it's equivalent on Android. [0] https://android.googlesource.com/platform/bionic/+/refs/heads/android13-release/libc/bionic/faccessat.cpp#50 [1] https://github.com/libbpf/libbpf-bootstrap/issues/250#issuecomment-1911324250 Fixes: 6a4ab8869d0b ("libbpf: Fix the case of running as non-root with capabilities") Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/20240126220944.2497665-1-andrii@kernel.org

libbpf: Wire up BPF token support at BPF object level

2024-01-25T00:21:02+00:00

Add BPF token support to BPF object-level functionality. BPF token is supported by BPF object logic either as an explicitly provided BPF token from outside (through BPF FS path), or implicitly (unless prevented through bpf_object_open_opts). Implicit mode is assumed to be the most common one for user namespaced unprivileged workloads. The assumption is that privileged container manager sets up default BPF FS mount point at /sys/fs/bpf with BPF token delegation options (delegate_{cmds,maps,progs,attachs} mount options). BPF object during loading will attempt to create BPF token from /sys/fs/bpf location, and pass it for all relevant operations (currently, map creation, BTF load, and program load). In this implicit mode, if BPF token creation fails due to whatever reason (BPF FS is not mounted, or kernel doesn't support BPF token, etc), this is not considered an error. BPF object loading sequence will proceed with no BPF token. In explicit BPF token mode, user provides explicitly custom BPF FS mount point path. In such case, BPF object will attempt to create BPF token from provided BPF FS location. If BPF token creation fails, that is considered a critical error and BPF object load fails with an error. Libbpf provides a way to disable implicit BPF token creation, if it causes any troubles (BPF token is designed to be completely optional and shouldn't cause any problems even if provided, but in the world of BPF LSM, custom security logic can be installed that might change outcome depending on the presence of BPF token). To disable libbpf's default BPF token creation behavior user should provide either invalid BPF token FD (negative), or empty bpf_token_path option. BPF token presence can influence libbpf's feature probing, so if BPF object has associated BPF token, feature probing is instructed to use BPF object-specific feature detection cache and token FD. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20240124022127.2379740-26-andrii@kernel.org