kernel/linux.git/tools/bpf/bpftool/gen.c, branch linux-7.0.y

bpftool: Make skeleton C++ compatible with explicit casts

2026-01-09T19:01:54+00:00

Fix C++ compilation errors in generated skeleton by adding explicit pointer casts and use char * subtraction for offset calculation error: invalid conversion from 'void*' to '*' [-fpermissive] | skel = skel_alloc(sizeof(*skel)); | ~~~~~~~~~~^~~~~~~~~~~~~~~ | | | void* error: arithmetic on pointers to void | skel->ctx.sz = (void *)&skel->links - (void *)skel; | ~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~ error: assigning to 'struct __ *' from incompatible type 'void *' | skel-> = skel_prep_map_data((void *)data, 4096, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | sizeof(data) - 1); | ~~~~~~~~~~~~~~~~~ error: assigning to 'struct __ *' from incompatible type 'void *' | skel-> = skel_finalize_map_data(&skel->maps..initial_value, | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | 4096, PROT_READ | PROT_WRITE, skel->maps..map_fd); | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Minimum reproducer: $ cat test.bpf.c int val; // placed in .bss section #include "vmlinux.h" #include SEC("raw_tracepoint/sched_wakeup_new") int handle(void *ctx) { return 0; } $ cat test.cpp #include extern "C" { #include "test.bpf.skel.h" } $ bpftool btf dump file /sys/kernel/btf/vmlinux format c > vmlinux.h $ clang -g -O2 -target bpf -c test.bpf.c -o test.bpf.o $ bpftool gen skeleton test.bpf.o -L > test.bpf.skel.h $ g++ -c test.cpp -I. Co-developed-by: Menglong Dong Signed-off-by: WanLi Niu Signed-off-by: Menglong Dong Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260106023123.2928-1-kiraskyler@163.com

bpftool: Add support for signing BPF programs

2025-09-23T02:17:55+00:00

Two modes of operation being added: Add two modes of operation: * For prog load, allow signing a program immediately before loading. This is essential for command-line testing and administration. bpftool prog load -S -k -i fentry_test.bpf.o * For gen skeleton, embed a pre-generated signature into the C skeleton file. This supports the use of signed programs in compiled applications. bpftool gen skeleton -S -k -i fentry_test.bpf.o Generation of the loader program and its metadata map is implemented in libbpf (bpf_obj__gen_loader). bpftool generates a skeleton that loads the program and automates the required steps: freezing the map, creating an exclusive map, loading, and running. Users can use standard libbpf APIs directly or integrate loader program generation into their own toolchains. Signed-off-by: KP Singh Acked-by: Quentin Monnet Link: https://lore.kernel.org/r/20250921160120.9711-5-kpsingh@kernel.org Signed-off-by: Alexei Starovoitov

bpftool: Using the right format specifiers

2025-02-11T00:08:13+00:00

Fixed some formatting specifiers errors, such as using %d for int and %u for unsigned int, as well as other byte-length types. Signed-off-by: Jiayuan Chen Signed-off-by: Andrii Nakryiko Reviewed-by: Quentin Monnet Link: https://lore.kernel.org/bpf/20250207123706.727928-2-mrpre@163.com

bpftool: improve skeleton backwards compat with old buggy libbpfs

2024-07-10T02:03:05+00:00

Old versions of libbpf don't handle varying sizes of bpf_map_skeleton struct correctly. As such, BPF skeleton generated by newest bpftool might not be compatible with older libbpf (though only when libbpf is used as a shared library), even though it, by design, should. Going forward libbpf will be fixed, plus we'll release bug fixed versions of relevant old libbpfs, but meanwhile try to mitigate from bpftool side by conservatively assuming older and smaller definition of bpf_map_skeleton, if possible. Meaning, if there are no struct_ops maps. If there are struct_ops, then presumably user would like to have auto-attaching logic and struct_ops map link placeholders, so use the full bpf_map_skeleton definition in that case. Acked-by: Quentin Monnet Co-developed-by: Mykyta Yatsenko Signed-off-by: Mykyta Yatsenko Signed-off-by: Andrii Nakryiko Acked-by: Eduard Zingerman Link: https://lore.kernel.org/r/20240708204540.4188946-2-andrii@kernel.org Signed-off-by: Alexei Starovoitov

bpftool: Allow compile-time checks of BPF map auto-attach support in skeleton

2024-06-21T17:53:09+00:00

New versions of bpftool now emit additional link placeholders for BPF maps (struct_ops maps are the only maps right now that support attachment), and set up BPF skeleton in such a way that libbpf will auto-attach BPF maps automatically, assumming libbpf is recent enough (v1.5+). Old libbpf will do nothing with those links and won't attempt to auto-attach maps. This allows user code to handle both pre-v1.5 and v1.5+ versions of libbpf at runtime, if necessary. But if users don't have (or don't want to) control bpftool version that generates skeleton, then they can't just assume that skeleton will have link placeholders. To make this detection possible and easy, let's add the following to generated skeleton header file: #define BPF_SKEL_SUPPORTS_MAP_AUTO_ATTACH 1 This can be used during compilation time to guard code that accesses skel->links. slots. Note, if auto-attachment is undesirable, libbpf allows to disable this through bpf_map__set_autoattach(map, false). This is necessary only on libbpf v1.5+, older libbpf doesn't support map auto-attach anyways. Libbpf version can be detected at compilation time using LIBBPF_MAJOR_VERSION and LIBBPF_MINOR_VERSION macros, or at runtime with libbpf_major_version() and libbpf_minor_version() APIs. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Quentin Monnet Link: https://lore.kernel.org/bpf/20240618183832.2535876-1-andrii@kernel.org

libbpf: Auto-attach struct_ops BPF maps in BPF skeleton

2024-06-06T17:06:05+00:00

Similarly to `bpf_program`, support `bpf_map` automatic attachment in `bpf_object__attach_skeleton`. Currently only struct_ops maps could be attached. On bpftool side, code-generate links in skeleton struct for struct_ops maps. Similarly to `bpf_program_skeleton`, set links in `bpf_map_skeleton`. On libbpf side, extend `bpf_map` with new `autoattach` field to support enabling or disabling autoattach functionality, introducing getter/setter for this field. `bpf_object__(attach|detach)_skeleton` is extended with attaching/detaching struct_ops maps logic. Signed-off-by: Mykyta Yatsenko Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20240605175135.117127-1-yatsenko@meta.com

bpftool: Use BTF field iterator in btfgen

2024-06-05T14:54:41+00:00

Switch bpftool's code which is using libbpf-internal btf_type_visit_type_ids() helper to new btf_field_iter functionality. This makes bpftool code simpler, but also unblocks removing libbpf's btf_type_visit_type_ids() helper completely. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Tested-by: Alan Maguire Reviewed-by: Quentin Monnet Acked-by: Eduard Zingerman Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/20240605001629.4061937-5-andrii@kernel.org

bpftool: Use typeof() instead of typeof() in BPF skeleton

2024-04-02T14:20:49+00:00

When generated BPF skeleton header is included in C++ code base, some compiler setups will emit warning about using language extensions due to typeof() usage, resulting in something like: error: extension used [-Werror,-Wlanguage-extension-token] obj->struct_ops.empty_tcp_ca = (typeof(obj->struct_ops.empty_tcp_ca)) ^ It looks like __typeof__() is a preferred way to do typeof() with better C++ compatibility behavior, so switch to that. With __typeof__() we get no such warning. Fixes: c2a0257c1edf ("bpftool: Cast pointers for shadow types explicitly.") Fixes: 00389c58ffe9 ("bpftool: Add support for subskeletons") Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Kui-Feng Lee Acked-by: Quentin Monnet Acked-by: John Fastabend Link: https://lore.kernel.org/bpf/20240401170713.2081368-1-andrii@kernel.org

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2024-03-29T00:25:57+00:00

Cross-merge networking fixes after downstream PR. No conflicts, or adjacent changes. Signed-off-by: Jakub Kicinski

libbpf, selftests/bpf: Adjust libbpf, bpftool, selftests to match LLVM

2024-03-15T21:24:00+00:00

The selftests use to tell LLVM about special pointers. For LLVM there is nothing "arena" about them. They are simply pointers in a different address space. Hence LLVM diff https://github.com/llvm/llvm-project/pull/85161 renamed: . macro __BPF_FEATURE_ARENA_CAST -> __BPF_FEATURE_ADDR_SPACE_CAST . global variables in __attribute__((address_space(N))) are now placed in section named ".addr_space.N" instead of ".arena.N". Adjust libbpf, bpftool, and selftests to match LLVM. Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko Acked-by: Stanislav Fomichev Link: https://lore.kernel.org/bpf/20240315021834.62988-3-alexei.starovoitov@gmail.com