kernel/linux.git/tools/lib/bpf/linker.c, branch v6.18.22

libbpf: Fix invalid write loop logic in bpf_linker__add_buf()

2026-02-26T22:59:38+00:00

[ Upstream commit 04999b99e81eaa7b6223ec1c03af3bcb4ac57aaa ] Fix bpf_linker__add_buf()'s logic of copying data from memory buffer into memfd. In the event of short write not writing entire buf_sz bytes into memfd file, we'll append bytes from the beginning of buf *again* (corrupting ELF file contents) instead of correctly appending the rest of not-yet-read buf contents. Closes: https://github.com/libbpf/libbpf/issues/945 Fixes: 6d5e5e5d7ce1 ("libbpf: Extend linker API to support in-memory ELF files") Signed-off-by: Amery Hung Signed-off-by: Andrii Nakryiko Acked-by: Jiri Olsa Link: https://lore.kernel.org/bpf/20260209230134.3530521-1-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin

libbpf: move libbpf_errstr() into libbpf_utils.c

2025-10-01T22:27:25+00:00

Get rid of str_err.{c,h} by moving implementation of libbpf_errstr() into libbpf_utils.c and declarations into libbpf_internal.h. Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20251001171326.3883055-4-andrii@kernel.org Signed-off-by: Alexei Starovoitov Acked-by: Eduard Zingerman

libbpf: Use proper errno value in linker

2025-04-30T16:04:20+00:00

Return values of the linker_append_sec_data() and the linker_append_elf_relos() functions are propagated all the way up to users of libbpf API. In some error cases these functions return -1 which will be seen as -EPERM from user's point of view. Instead, return a more reasonable -EINVAL. Fixes: faf6ed321cf6 ("libbpf: Add BPF static linker APIs") Signed-off-by: Anton Protopopov Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20250430120820.2262053-1-a.s.protopopov@gmail.com

libbpf: Fix implicit memfd_create() for bionic

2025-04-04T15:52:37+00:00

Since memfd_create() is not consistently available across different bionic libc implementations, using memfd_create() directly can break some Android builds: tools/lib/bpf/linker.c:576:7: error: implicit declaration of function 'memfd_create' [-Werror,-Wimplicit-function-declaration] 576 | fd = memfd_create(filename, 0); | ^ To fix this, relocate and inline the sys_memfd_create() helper so that it can be used in "linker.c". Similar issues were previously fixed by commit 9fa5e1a180aa ("libbpf: Call memfd_create() syscall directly"). Fixes: 6d5e5e5d7ce1 ("libbpf: Extend linker API to support in-memory ELF files") Signed-off-by: Carlos Llamas Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20250330211325.530677-1-cmllamas@google.com

libbpf: Fix hypothetical STT_SECTION extern NULL deref case

2025-02-21T02:42:16+00:00

Fix theoretical NULL dereference in linker when resolving *extern* STT_SECTION symbol against not-yet-existing ELF section. Not sure if it's possible in practice for valid ELF object files (this would require embedded assembly manipulations, at which point BTF will be missing), but fix the s/dst_sym/dst_sec/ typo guarding this condition anyways. Fixes: faf6ed321cf6 ("libbpf: Add BPF static linker APIs") Fixes: a46349227cd8 ("libbpf: Add linker extern resolution support for functions and global variables") Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20250220002821.834400-1-andrii@kernel.org Signed-off-by: Alexei Starovoitov

libbpf: Extend linker API to support in-memory ELF files

2024-12-12T23:16:53+00:00

The new_fd and add_fd functions correspond to the original new and add_file functions, but accept an FD instead of a file name. This gives API consumers the option of using anonymous files/memfds to avoid writing ELFs to disk. This new API will be useful for performing linking as part of bpftrace's JIT compilation. The add_buf function is a convenience wrapper that does the work of creating a memfd for the caller. Signed-off-by: Alastair Robertson Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20241211164030.573042-3-ajor@meta.com

libbpf: Pull file-opening logic up to top-level functions

2024-12-12T23:09:21+00:00

Move the filename arguments and file-descriptor handling from init_output_elf() and linker_load_obj_file() and instead handle them at the top-level in bpf_linker__new() and bpf_linker__add_file(). This will allow the inner functions to be shared with a new, non-filename-based, API in the next commit. Signed-off-by: Alastair Robertson Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20241211164030.573042-2-ajor@meta.com

libbpf: Fix segfault due to libelf functions not setting errno

2024-12-05T23:19:00+00:00

Libelf functions do not set errno on failure. Instead, it relies on its internal _elf_errno value, that can be retrieved via elf_errno (or the corresponding message via elf_errmsg()). From "man libelf": If a libelf function encounters an error it will set an internal error code that can be retrieved with elf_errno. Each thread maintains its own separate error code. The meaning of each error code can be determined with elf_errmsg, which returns a string describing the error. As a consequence, libbpf should not return -errno when a function from libelf fails, because an empty value will not be interpreted as an error and won't prevent the program to stop. This is visible in bpf_linker__add_file(), for example, where we call a succession of functions that rely on libelf: err = err ?: linker_load_obj_file(linker, filename, opts, &obj); err = err ?: linker_append_sec_data(linker, &obj); err = err ?: linker_append_elf_syms(linker, &obj); err = err ?: linker_append_elf_relos(linker, &obj); err = err ?: linker_append_btf(linker, &obj); err = err ?: linker_append_btf_ext(linker, &obj); If the object file that we try to process is not, in fact, a correct object file, linker_load_obj_file() may fail with errno not being set, and return 0. In this case we attempt to run linker_append_elf_sysms() and may segfault. This can happen (and was discovered) with bpftool: $ bpftool gen object output.o sample_ret0.bpf.c libbpf: failed to get ELF header for sample_ret0.bpf.c: invalid `Elf' handle zsh: segmentation fault (core dumped) bpftool gen object output.o sample_ret0.bpf.c Fix the issue by returning a non-null error code (-EINVAL) when libelf functions fail. Fixes: faf6ed321cf6 ("libbpf: Add BPF static linker APIs") Signed-off-by: Quentin Monnet Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20241205135942.65262-1-qmo@kernel.org

libbpf: Stringify errno in log messages in the remaining code

2024-11-12T04:29:45+00:00

Convert numeric error codes into the string representations in log messages in the rest of libbpf source files. Signed-off-by: Mykyta Yatsenko Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20241111212919.368971-5-mykyta.yatsenko5@gmail.com

libbpf: Do not resolve size on duplicate FUNCs

2024-10-08T03:28:53+00:00

FUNCs do not have sizes, thus currently btf__resolve_size will fail with -EINVAL. Add conditions so that we only update size when the BTF object is not function or function prototype. Signed-off-by: Eric Long Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20241002-libbpf-dup-extern-funcs-v4-1-560eb460ff90@hack3r.moe