Re: [PATCH bpf-next v4 0/3] Add btf_custom_path in bpf_obj_open_opts
From: Andrii Nakryiko <hidden>
Date: 2021-07-16 04:49:58
Also in:
bpf, kernel-janitors, lkml
On Tue, Jul 13, 2021 at 5:43 AM Shuyi Cheng [off-list ref] wrote:
This patch set adds the ability to point to a custom BTF for the purposes of BPF CO-RE relocations. This is useful for using BPF CO-RE on old kernels that don't yet natively support kernel (vmlinux) BTF and thus libbpf needs application's help in locating kernel BTF generated separately from the kernel itself. This was already possible to do through bpf_object__load's attribute struct, but that makes it inconvenient to use with BPF skeleton, which only allows to specify bpf_object_open_opts during the open step. Thus, add the ability to override vmlinux BTF at open time. Patch #1 adds libbpf changes. Patch #2 fixes pre-existing memory leak detected during the code review. Patch #3 switches existing selftests to using open_opts for custom BTF.
LGTM with some minor things I'll adjust while applying (which I'll point out in respective patches). So no need to re-send anything. Thanks.
quoted hunk ↗ jump to hunk
Changelog: ---------- v3: https://lore.kernel.org/bpf/CAEf4BzY2cdT44bfbMus=gei27ViqGE1BtGo6XrErSsOCnqtVJg@mail.gmail.com/T/#m877eed1d4cf0a1d3352d3f3d6c5ff158be45c542 (local) v3->v4:--- Follow Andrii's suggestion to modify cover letter description. --- Delete function bpf_object__load_override_btf. --- Follow Dan's suggestion to add fixes tag and modify commit msg to patch #2. --- Add pathch #3 to switch existing selftests to using open_opts.v2: https://lore.kernel.org/bpf/CAEf4Bza_ua+tjxdhyy4nZ8Boeo+scipWmr_1xM1pC6N5wyuhAA@mail.gmail.com/T/#mf9cf86ae0ffa96180ac29e4fd12697eb70eccd0f (local) v2->v3:--- Load the BTF specified by btf_custom_path to btf_vmlinux_override instead of btf_bmlinux. --- Fix the memory leak that may be introduced by the second version of the patch. --- Add a new patch to fix the possible memory leak caused by obj->kconfig.v1: https://lore.kernel.org/bpf/CAEf4BzaGjEC4t1OefDo11pj2-HfNy0BLhs_G2UREjRNTmb2u=A@mail.gmail.com/t/#m4d9f7c6761fbd2b436b5dfe491cd864b70225804 (local) v1->v2: -- Change custom_btf_path to btf_custom_path. -- If the length of btf_custom_path of bpf_obj_open_opts is too long, return ERR_PTR(-ENAMETOOLONG). -- Add `custom BTF is in addition to vmlinux BTF` with btf_custom_path field. Shuyi Cheng (3): libbpf: Introduce 'btf_custom_path' to 'bpf_obj_open_opts' libbpf: Fix the possible memory leak on error selftests/bpf: switches existing selftests to using open_opts for custom BTF tools/lib/bpf/libbpf.c | 42 +++++++++++++++++----- tools/lib/bpf/libbpf.h | 9 ++++- .../selftests/bpf/prog_tests/core_autosize.c | 22 ++++++------ .../testing/selftests/bpf/prog_tests/core_reloc.c | 28 +++++++-------- 4 files changed, 66 insertions(+), 35 deletions(-) -- 1.8.3.1