lwn.git/Documentation/bpf/bpf_devel_QA.rst, branch docs-mw

docs/bpf: Default cpu version changed from v1 to v3 in llvm 20

2025-06-12T23:52:44+00:00

The default cpu version is changed from v1 to v3 in llvm version 20. See [1] for more detailed reasoning. Update bpf_devel_QA.rst so developers can find such information easily. [1] https://github.com/llvm/llvm-project/pull/107008 Signed-off-by: Yonghong Song Link: https://lore.kernel.org/r/20250612043049.2411989-1-yonghong.song@linux.dev Signed-off-by: Alexei Starovoitov

bpf: Add namespace to BPF internal symbols

2025-04-25T16:21:23+00:00

Add namespace to BPF internal symbols used by light skeleton to prevent abuse and document with the code their allowed usage. Fixes: b1d18a7574d0 ("bpf: Extend sys_bpf commands for bpf_syscall programs.") Signed-off-by: Alexei Starovoitov Signed-off-by: Andrii Nakryiko Acked-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/bpf/20250425014542.62385-1-alexei.starovoitov@gmail.com

bpf: Replace deprecated -target with --target= for Clang

2023-06-29T13:46:17+00:00

The -target option has been deprecated since clang 3.4 in 2013. Therefore, use the preferred --target=bpf form instead. This also matches how we use --target= in scripts/Makefile.clang. Signed-off-by: Fangrui Song Signed-off-by: Daniel Borkmann Acked-by: Yonghong Song Acked-by: Quentin Monnet Link: https://github.com/llvm/llvm-project/commit/274b6f0c87a6a1798de0a68135afc7f95def6277 Link: https://lore.kernel.org/bpf/20230624001856.1903733-1-maskray@google.com

Daniel Borkmann says:

2023-04-13T23:43:38+00:00

==================== pull-request: bpf-next 2023-04-13 We've added 260 non-merge commits during the last 36 day(s) which contain a total of 356 files changed, 21786 insertions(+), 11275 deletions(-). The main changes are: 1) Rework BPF verifier log behavior and implement it as a rotating log by default with the option to retain old-style fixed log behavior, from Andrii Nakryiko. 2) Adds support for using {FOU,GUE} encap with an ipip device operating in collect_md mode and add a set of BPF kfuncs for controlling encap params, from Christian Ehrig. 3) Allow BPF programs to detect at load time whether a particular kfunc exists or not, and also add support for this in light skeleton, from Alexei Starovoitov. 4) Optimize hashmap lookups when key size is multiple of 4, from Anton Protopopov. 5) Enable RCU semantics for task BPF kptrs and allow referenced kptr tasks to be stored in BPF maps, from David Vernet. 6) Add support for stashing local BPF kptr into a map value via bpf_kptr_xchg(). This is useful e.g. for rbtree node creation for new cgroups, from Dave Marchevsky. 7) Fix BTF handling of is_int_ptr to skip modifiers to work around tracing issues where a program cannot be attached, from Feng Zhou. 8) Migrate a big portion of test_verifier unit tests over to test_progs -a verifier_* via inline asm to ease {read,debug}ability, from Eduard Zingerman. 9) Several updates to the instruction-set.rst documentation which is subject to future IETF standardization (https://lwn.net/Articles/926882/), from Dave Thaler. 10) Fix BPF verifier in the __reg_bound_offset's 64->32 tnum sub-register known bits information propagation, from Daniel Borkmann. 11) Add skb bitfield compaction work related to BPF with the overall goal to make more of the sk_buff bits optional, from Jakub Kicinski. 12) BPF selftest cleanups for build id extraction which stand on its own from the upcoming integration work of build id into struct file object, from Jiri Olsa. 13) Add fixes and optimizations for xsk descriptor validation and several selftest improvements for xsk sockets, from Kal Conley. 14) Add BPF links for struct_ops and enable switching implementations of BPF TCP cong-ctls under a given name by replacing backing struct_ops map, from Kui-Feng Lee. 15) Remove a misleading BPF verifier env->bypass_spec_v1 check on variable offset stack read as earlier Spectre checks cover this, from Luis Gerhorst. 16) Fix issues in copy_from_user_nofault() for BPF and other tracers to resemble copy_from_user_nmi() from safety PoV, from Florian Lehner and Alexei Starovoitov. 17) Add --json-summary option to test_progs in order for CI tooling to ease parsing of test results, from Manu Bretelle. 18) Batch of improvements and refactoring to prep for upcoming bpf_local_storage conversion to bpf_mem_cache_{alloc,free} allocator, from Martin KaFai Lau. 19) Improve bpftool's visual program dump which produces the control flow graph in a DOT format by adding C source inline annotations, from Quentin Monnet. 20) Fix attaching fentry/fexit/fmod_ret/lsm to modules by extracting the module name from BTF of the target and searching kallsyms of the correct module, from Viktor Malik. 21) Improve BPF verifier handling of ' ' to better detect whether in particular jmp32 branches are taken, from Yonghong Song. 22) Allow BPF TCP cong-ctls to write app_limited of struct tcp_sock. A built-in cc or one from a kernel module is already able to write to app_limited, from Yixin Shen. Conflicts: Documentation/bpf/bpf_devel_QA.rst b7abcd9c656b ("bpf, doc: Link to submitting-patches.rst for general patch submission info") 0f10f647f455 ("bpf, docs: Use internal linking for link to netdev subsystem doc") https://lore.kernel.org/all/20230307095812.236eb1be@canb.auug.org.au/ include/net/ip_tunnels.h bc9d003dc48c3 ("ip_tunnel: Preserve pointer const in ip_tunnel_info_opts") ac931d4cdec3d ("ipip,ip_tunnel,sit: Add FOU support for externally controlled ipip devices") https://lore.kernel.org/all/20230413161235.4093777-1-broonie@kernel.org/ net/bpf/test_run.c e5995bc7e2ba ("bpf, test_run: fix crashes due to XDP frame overwriting/corruption") 294635a8165a ("bpf, test_run: fix &xdp_frame misplacement for LIVE_FRAMES") https://lore.kernel.org/all/20230320102619.05b80a98@canb.auug.org.au/ ==================== Link: https://lore.kernel.org/r/20230413191525.7295-1-daniel@iogearbox.net Signed-off-by: Jakub Kicinski

bpf, docs: Use internal linking for link to netdev subsystem doc

2023-03-17T12:58:57+00:00

Commit d56b0c461d19da ("bpf, docs: Fix link to netdev-FAQ target") attempts to fix linking problem to undefined "netdev-FAQ" label introduced in 287f4fa99a5281 ("docs: Update references to netdev-FAQ") by changing internal cross reference to netdev subsystem documentation (Documentation/process/maintainer-netdev.rst) to external one at docs.kernel.org. However, the linking problem is still not resolved, as the generated link points to non-existent netdev-FAQ section of the external doc, which when clicked, will instead going to the top of the doc. Revert back to internal linking by simply mention the doc path while massaging the leading text to the link, since the netdev subsystem doc contains no FAQs but rather general information about the subsystem. Fixes: d56b0c461d19 ("bpf, docs: Fix link to netdev-FAQ target") Fixes: 287f4fa99a52 ("docs: Update references to netdev-FAQ") Signed-off-by: Bagas Sanjaya Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20230314074449.23620-1-bagasdotme@gmail.com

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

2023-03-10T06:22:11+00:00

Documentation/bpf/bpf_devel_QA.rst b7abcd9c656b ("bpf, doc: Link to submitting-patches.rst for general patch submission info") d56b0c461d19 ("bpf, docs: Fix link to netdev-FAQ target") https://lore.kernel.org/all/20230307095812.236eb1be@canb.auug.org.au/ Signed-off-by: Jakub Kicinski

bpf, doc: Link to submitting-patches.rst for general patch submission info

2023-03-06T15:44:39+00:00

The link for patch submission information in general refers to index page for "Working with the kernel development community" section of kernel docs, whereas the link should have been Documentation/process/submitting-patches.rst instead. Fix it by replacing the index target with the appropriate doc. Fixes: 542228384888f5 ("bpf, doc: convert bpf_devel_QA.rst to use RST formatting") Signed-off-by: Bagas Sanjaya Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20230228074523.11493-3-bagasdotme@gmail.com

bpf, doc: Do not link to docs.kernel.org for kselftest link

2023-03-06T15:44:34+00:00

The question on how to run BPF selftests have a reference link to kernel selftest documentation (Documentation/dev-tools/kselftest.rst). However, it uses external link to the documentation at kernel.org/docs (aka docs.kernel.org) instead, which requires Internet access. Fix this and replace the link with internal linking, by using :doc: directive while keeping the anchor text. Fixes: b7a27c3aafa252 ("bpf, doc: howto use/run the BPF selftests") Signed-off-by: Bagas Sanjaya Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20230228074523.11493-2-bagasdotme@gmail.com

bpf, docs: Fix link to netdev-FAQ target

2023-03-03T06:36:10+00:00

The BPF devel Q&A documentation page makes frequent reference to the netdev-QA page via the netdev-FAQ rst link. This link is currently broken, as is evidenced by the build output when making BPF docs: ./Documentation/bpf/bpf_devel_QA.rst:150: WARNING: undefined label: 'netdev-faq' ./Documentation/bpf/bpf_devel_QA.rst:206: WARNING: undefined label: 'netdev-faq' ./Documentation/bpf/bpf_devel_QA.rst:231: WARNING: undefined label: 'netdev-faq' ./Documentation/bpf/bpf_devel_QA.rst:396: WARNING: undefined label: 'netdev-faq' ./Documentation/bpf/bpf_devel_QA.rst:412: WARNING: undefined label: 'netdev-faq' Fix the links to point to the actual netdev-faq page. Signed-off-by: David Vernet Link: https://lore.kernel.org/r/20230302183918.54190-1-void@manifault.com Signed-off-by: Alexei Starovoitov

bpf, docs: Fix link to BTF doc

2023-02-27T20:54:14+00:00

Ross reported broken link to BTF documentation (Documentation/bpf/btf.rst) in Documentation/bpf/bpf_devel_QA.rst. The link in question is written using external link syntax, with the target refers to BTF doc in reST source (btf.rst), which doesn't exist in resulting HTML output. Fix the link by replacing external link syntax with simply writing out the target doc, which the link will be generated to the correct HTML doc target. Fixes: 6736aa793c2b5f ("selftests/bpf: Add general instructions for test execution") Reported-by: Ross Zwisler Signed-off-by: Bagas Sanjaya Signed-off-by: Daniel Borkmann Acked-by: Ross Zwisler Link: https://lore.kernel.org/linux-doc/Y++09LKx25dtR4Ow@google.com/ Link: https://lore.kernel.org/bpf/20230222083530.26136-1-bagasdotme@gmail.com