kernel/tools/lib/bpf/libbpf.c, branch linux-4.16.y

tools/libbpf: Avoid possibly using uninitialized variable

2018-02-20T20:08:20Z

Fixes a GCC maybe-uninitialized warning introduced by 48cca7e44f9f. "text" is only initialized inside the if statement so only print debug info there. Fixes: 48cca7e44f9f ("libbpf: add support for bpf_call") Signed-off-by: Jeremy Cline Signed-off-by: Daniel Borkmann

tools/libbpf: handle issues with bpf ELF objects containing .eh_frames

2018-02-08T23:25:12Z

V3: More generic skipping of relo-section (suggested by Daniel) If clang >= 4.0.1 is missing the option '-target bpf', it will cause llc/llvm to create two ELF sections for "Exception Frames", with section names '.eh_frame' and '.rel.eh_frame'. The BPF ELF loader library libbpf fails when loading files with these sections. The other in-kernel BPF ELF loader in samples/bpf/bpf_load.c, handle this gracefully. And iproute2 loader also seems to work with these "eh" sections. The issue in libbpf is caused by bpf_object__elf_collect() skipping some sections, and later when performing relocation it will be pointing to a skipped section, as these sections cannot be found by bpf_object__find_prog_by_idx() in bpf_object__collect_reloc(). This is a general issue that also occurs for other sections, like debug sections which are also skipped and can have relo section. As suggested by Daniel. To avoid keeping state about all skipped sections, instead perform a direct qlookup in the ELF object. Lookup the section that the relo-section points to and check if it contains executable machine instructions (denoted by the sh_flags SHF_EXECINSTR). Use this check to also skip irrelevant relo-sections. Note, for samples/bpf/ the '-target bpf' parameter to clang cannot be used due to incompatibility with asm embedded headers, that some of the samples include. This is explained in more details by Yonghong Song in bpf_devel_QA. Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Daniel Borkmann

tools/libbpf: improve the pr_debug statements to contain section numbers

2018-02-08T23:24:38Z

While debugging a bpf ELF loading issue, I needed to correlate the ELF section number with the failed relocation section reference. Thus, add section numbers/index to the pr_debug. In debug mode, also print section that were skipped. This helped me identify that a section (.eh_frame) was skipped, and this was the reason the relocation section (.rel.eh_frame) could not find that section number. The section numbers corresponds to the readelf tools Section Headers [Nr]. Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Daniel Borkmann

libbpf: complete list of strings for guessing program type

2018-02-08T10:59:50Z

It seems that the type guessing feature for libbpf, based on the name of the ELF section the program is located in, was inspired from samples/bpf/prog_load.c, which was not used by any sample for loading programs of certain types such as TC actions and classifiers, or LWT-related types. As a consequence, libbpf is not able to guess the type of such programs and to load them automatically if type is not provided to the `bpf_load_prog()` function. Add ELF section names associated to those eBPF program types so that they can be loaded with e.g. bpftool as well. Signed-off-by: Quentin Monnet Reviewed-by: Jakub Kicinski Signed-off-by: Daniel Borkmann

libbpf: add missing SPDX-License-Identifier

2018-02-03T01:53:48Z

Signed-off-by: Eric Leblond Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov

libbpf: add function to setup XDP

2018-02-03T01:53:48Z

Most of the code is taken from set_link_xdp_fd() in bpf_load.c and slightly modified to be library compliant. Signed-off-by: Eric Leblond Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov

libbpf: fix string comparison for guessing eBPF program type

2018-01-17T00:15:05Z

libbpf is able to deduce the type of a program from the name of the ELF section in which it is located. However, the comparison is made on the first n characters, n being determined with sizeof() applied to the reference string (e.g. "xdp"). When such section names are supposed to receive a suffix separated with a slash (e.g. "kprobe/"), using sizeof() takes the final NUL character of the reference string into account, which implies that both strings must be equal. Instead, the desired behaviour would consist in taking the length of the string, *without* accounting for the ending NUL character, and to make sure the reference string is a prefix to the ELF section name. Subtract 1 to the total size of the string for obtaining the length for the comparison. Fixes: 583c90097f72 ("libbpf: add ability to guess program type based on section name") Signed-off-by: Quentin Monnet Acked-by: Jakub Kicinski Signed-off-by: Daniel Borkmann

libbpf: Fix build errors.

2017-12-20T00:33:25Z

These elf object pieces are of type Elf64_Xword and therefore could be "long long" on some builds. Cast to "long long" and use printf format %lld to deal with this since we are building with -Werror=format. Signed-off-by: David S. Miller Signed-off-by: Daniel Borkmann

libbpf: add support for bpf_call

2017-12-17T19:34:35Z

- recognize relocation emitted by llvm - since all regular function will be kept in .text section and llvm takes care of pc-relative offsets in bpf_call instruction simply copy all of .text to relevant program section while adjusting bpf_call instructions in program section to point to newly copied body of instructions from .text - do so for all programs in the elf file - set all programs types to the one passed to bpf_prog_load() Note for elf files with multiple programs that use different functions in .text section we need to do 'linker' style logic. This work is still TBD Signed-off-by: Alexei Starovoitov Acked-by: Daniel Borkmann Signed-off-by: Daniel Borkmann

libbpf: prefer global symbols as bpf program name source

2017-12-14T12:37:13Z

Libbpf picks the name of the first symbol in the corresponding elf section to use as a program name. But without taking symbol's scope into account it may end's up with some local label as a program name. E.g.: $ bpftool prog 1: type 15 name LBB0_10 tag 0390a5136ba23f5c loaded_at Dec 07/17:22 uid 0 xlated 456B not jited memlock 4096B Fix this by preferring global symbols as program name. For instance: $ bpftool prog 1: type 15 name bpf_prog1 tag 0390a5136ba23f5c loaded_at Dec 07/17:26 uid 0 xlated 456B not jited memlock 4096B Signed-off-by: Roman Gushchin Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Jakub Kicinski Cc: Martin KaFai Lau Cc: Quentin Monnet Cc: David Ahern Signed-off-by: Daniel Borkmann