kernel/git/next/linux-next.git/tools/lib/bpf, branch akpm

bpf: Merge "types_are_compat" logic into relo_core.c

2022-06-24T21:15:37+00:00

BPF type compatibility checks (bpf_core_types_are_compat()) are currently duplicated between kernel and user space. That's a historical artifact more than intentional doing and can lead to subtle bugs where one implementation is adjusted but another is forgotten. That happened with the enum64 work, for example, where the libbpf side was changed (commit 23b2a3a8f63a ("libbpf: Add enum64 relocation support")) to use the btf_kind_core_compat() helper function but the kernel side was not (commit 6089fb325cf7 ("bpf: Add btf enum64 support")). This patch addresses both the duplication issue, by merging both implementations and moving them into relo_core.c, and fixes the alluded to kind check (by giving preference to libbpf's already adjusted logic). For discussion of the topic, please refer to: https://lore.kernel.org/bpf/CAADnVQKbWR7oarBdewgOBZUPzryhRYvEbkhyPJQHHuxq=0K1gw@mail.gmail.com/T/#mcc99f4a33ad9a322afaf1b9276fb1f0b7add9665 Changelog: v1 -> v2: - limited libbpf recursion limit to 32 - changed name to __bpf_core_types_are_compat - included warning previously present in libbpf version - merged kernel and user space changes into a single patch Signed-off-by: Daniel Müller Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20220623182934.2582827-1-deso@posteo.net

libbpf: add support for sleepable uprobe programs

2022-06-17T02:27:30+00:00

Add section mappings for u(ret)probe.s programs. Acked-by: Andrii Nakryiko Signed-off-by: Delyan Kratunov Link: https://lore.kernel.org/r/aedbc3b74f3523f00010a7b0df8f3388cca59f16.1655248076.git.delyank@fb.com Signed-off-by: Alexei Starovoitov

libbpf: Fix internal USDT address translation logic for shared libraries

2022-06-16T23:20:10+00:00

Perform the same virtual address to file offset translation that libbpf is doing for executable ELF binaries also for shared libraries. Currently libbpf is making a simplifying and sometimes wrong assumption that for shared libraries relative virtual addresses inside ELF are always equal to file offsets. Unfortunately, this is not always the case with LLVM's lld linker, which now by default generates quite more complicated ELF segments layout. E.g., for liburandom_read.so from selftests/bpf, here's an excerpt from readelf output listing ELF segments (a.k.a. program headers): Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align PHDR 0x000040 0x0000000000000040 0x0000000000000040 0x0001f8 0x0001f8 R 0x8 LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x0005e4 0x0005e4 R 0x1000 LOAD 0x0005f0 0x00000000000015f0 0x00000000000015f0 0x000160 0x000160 R E 0x1000 LOAD 0x000750 0x0000000000002750 0x0000000000002750 0x000210 0x000210 RW 0x1000 LOAD 0x000960 0x0000000000003960 0x0000000000003960 0x000028 0x000029 RW 0x1000 Compare that to what is generated by GNU ld (or LLVM lld's with extra -znoseparate-code argument which disables this cleverness in the name of file size reduction): Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x000550 0x000550 R 0x1000 LOAD 0x001000 0x0000000000001000 0x0000000000001000 0x000131 0x000131 R E 0x1000 LOAD 0x002000 0x0000000000002000 0x0000000000002000 0x0000ac 0x0000ac R 0x1000 LOAD 0x002dc0 0x0000000000003dc0 0x0000000000003dc0 0x000262 0x000268 RW 0x1000 You can see from the first example above that for executable (Flg == "R E") PT_LOAD segment (LOAD #2), Offset doesn't match VirtAddr columns. And it does in the second case (GNU ld output). This is important because all the addresses, including USDT specs, operate in a virtual address space, while kernel is expecting file offsets when performing uprobe attach. So such mismatches have to be properly taken care of and compensated by libbpf, which is what this patch is fixing. Also patch clarifies few function and variable names, as well as updates comments to reflect this important distinction (virtaddr vs file offset) and to ephasize that shared libraries are not all that different from executables in this regard. This patch also changes selftests/bpf Makefile to force urand_read and liburand_read.so to be built with Clang and LLVM's lld (and explicitly request this ELF file size optimization through -znoseparate-code linker parameter) to validate libbpf logic and ensure regressions don't happen in the future. I've bundled these selftests changes together with libbpf changes to keep the above description tied with both libbpf and selftests changes. Fixes: 74cc6311cec9 ("libbpf: Add USDT notes parsing and resolution logic") Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20220616055543.3285835-1-andrii@kernel.org

libbpf: Fix an unsigned < 0 bug

2022-06-14T15:01:54+00:00

Andrii reported a bug with the following information: 2859 if (enum64_placeholder_id == 0) { 2860 enum64_placeholder_id = btf__add_int(btf, "enum64_placeholder", 1, 0); >>> CID 394804: Control flow issues (NO_EFFECT) >>> This less-than-zero comparison of an unsigned value is never true. "enum64_placeholder_id < 0U". 2861 if (enum64_placeholder_id < 0) 2862 return enum64_placeholder_id; 2863 ... Here enum64_placeholder_id declared as '__u32' so enum64_placeholder_id < 0 is always false. Declare enum64_placeholder_id as 'int' in order to capture the potential error properly. Fixes: f2a625889bb8 ("libbpf: Add enum64 sanitization") Reported-by: Andrii Nakryiko Signed-off-by: Yonghong Song Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20220613054314.1251905-1-yhs@fb.com

libbpf: Fix uprobe symbol file offset calculation logic

2022-06-09T12:09:41+00:00

Fix libbpf's bpf_program__attach_uprobe() logic of determining function's *file offset* (which is what kernel is actually expecting) when attaching uprobe/uretprobe by function name. Previously calculation was determining virtual address offset relative to base load address, which (offset) is not always the same as file offset (though very frequently it is which is why this went unnoticed for a while). Fixes: 433966e3ae04 ("libbpf: Support function name-based attach uprobes") Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Cc: Riham Selim Cc: Alan Maguire Link: https://lore.kernel.org/bpf/20220606220143.3796908-1-andrii@kernel.org

libbpf: Add enum64 relocation support

2022-06-07T17:20:43+00:00

The enum64 relocation support is added. The bpf local type could be either enum or enum64 and the remote type could be either enum or enum64 too. The all combinations of local enum/enum64 and remote enum/enum64 are supported. Acked-by: Andrii Nakryiko Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20220607062647.3721719-1-yhs@fb.com Signed-off-by: Alexei Starovoitov

libbpf: Add enum64 support for bpf linking

2022-06-07T17:20:43+00:00

Add BTF_KIND_ENUM64 support for bpf linking, which is very similar to BTF_KIND_ENUM. Acked-by: Andrii Nakryiko Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20220607062642.3721494-1-yhs@fb.com Signed-off-by: Alexei Starovoitov

libbpf: Add enum64 sanitization

2022-06-07T17:20:43+00:00

When old kernel does not support enum64 but user space btf contains non-zero enum kflag or enum64, libbpf needs to do proper sanitization so modified btf can be accepted by the kernel. Sanitization for enum kflag can be achieved by clearing the kflag bit. For enum64, the type is replaced with an union of integer member types and the integer member size must be smaller than enum64 size. If such an integer type cannot be found, a new type is created and used for union members. Acked-by: Andrii Nakryiko Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20220607062636.3721375-1-yhs@fb.com Signed-off-by: Alexei Starovoitov

libbpf: Add enum64 support for btf_dump

2022-06-07T17:20:43+00:00

Add enum64 btf dumping support. For long long and unsigned long long dump, suffixes 'LL' and 'ULL' are added to avoid compilation errors in some cases. Acked-by: Andrii Nakryiko Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20220607062631.3720526-1-yhs@fb.com Signed-off-by: Alexei Starovoitov

libbpf: Add enum64 deduplication support

2022-06-07T17:20:43+00:00

Add enum64 deduplication support. BTF_KIND_ENUM64 handling is very similar to BTF_KIND_ENUM. Acked-by: Andrii Nakryiko Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20220607062626.3720166-1-yhs@fb.com Signed-off-by: Alexei Starovoitov