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Message-Id: <20210930062948.1843919-1-memxor@gmail.com>
Date: Thu, 30 Sep 2021 11:59:39 +0530
From: Kumar Kartikeya Dwivedi <memxor@...il.com>
To: bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Toke Høiland-Jørgensen <toke@...hat.com>,
netdev@...r.kernel.org
Subject: [PATCH bpf-next v6 0/9] Support kernel module function calls from eBPF
This set enables kernel module function calls, and also modifies verifier logic
to permit invalid kernel function calls as long as they are pruned as part of
dead code elimination. This is done to provide better runtime portability for
BPF objects, which can conditionally disable parts of code that are pruned later
by the verifier (e.g. const volatile vars, kconfig options). libbpf
modifications are made along with kernel changes to support module function
calls.
It also converts TCP congestion control objects to use the module kfunc support
instead of relying on IS_BUILTIN ifdef.
Changelog:
----------
v5 -> v6
v5: https://lore.kernel.org/bpf/20210927145941.1383001-1-memxor@gmail.com
* Rework gen_loader relocation emits
* Only emit bpf_btf_find_by_name_kind call when required (Alexei)
* Refactor code to emit ksym var and func relo into separate helpers, this
will be easier to add future weak/typeless ksym support to (for my followup)
* Count references for both ksym var and funcs, and avoid calling helpers
unless required for both of them. This also means we share fds between
ksym vars for the module BTFs. Also be careful with this when closing
BTF fd so that we only close one instance of the fd for each ksym
v4 -> v5
v4: https://lore.kernel.org/bpf/20210920141526.3940002-1-memxor@gmail.com
* Address comments from Alexei
* Use reserved fd_array area in loader map instead of creating a new map
* Drop selftest testing the 256 kfunc limit, however selftest testing reuse
of BTF fd for same kfunc in gen_loader and libbpf is kept
* Address comments from Andrii
* Make --no-fail the default for resolve_btfids, i.e. only fail if we find
BTF section and cannot process it
* Use obj->btf_modules array to store index in the fd_array, so that we don't
have to do any searching to reuse the index, instead only set it the first
time a module BTF's fd is used
* Make find_ksym_btf_id to return struct module_btf * in last parameter
* Improve logging when index becomes bigger than INT16_MAX
* Add btf__find_by_name_kind_own internal helper to only start searching for
kfunc ID in module BTF, since find_ksym_btf_id already checks vmlinux BTF
before iterating over module BTFs.
* Fix various other nits
* Fixes for failing selftests on BPF CI
* Rearrange/cleanup selftests
* Avoid testing kfunc limit (Alexei)
* Do test gen_loader and libbpf BTF fd index dedup with 256 calls
* Move invalid kfunc failure test to verifier selftest
* Minimize duplication
* Use consistent bpf_<type>_check_kfunc_call naming for module kfunc callback
* Since we try to add fd using add_data while we can, cherry pick Alexei's
patch from CO-RE RFC series to align gen_loader data.
v3 -> v4
v3: https://lore.kernel.org/bpf/20210915050943.679062-1-memxor@gmail.com
* Address comments from Alexei
* Drop MAX_BPF_STACK change, instead move map_fd and BTF fd to BPF array map
and pass fd_array using BPF_PSEUDO_MAP_IDX_VALUE
* Address comments from Andrii
* Fix selftest to store to variable for observing function call instead of
printk and polluting CI logs
* Drop use of raw_tp for testing, instead reuse classifier based prog_test_run
* Drop index + 1 based insn->off convention for kfunc module calls
* Expand selftests to cover more corner cases
* Misc cleanups
v2 -> v3
v2: https://lore.kernel.org/bpf/20210914123750.460750-1-memxor@gmail.com
* Fix issues pointed out by Kernel Test Robot
* Fix find_kfunc_desc to also take offset into consideration when comparing
RFC v1 -> v2
v1: https://lore.kernel.org/bpf/20210830173424.1385796-1-memxor@gmail.com
* Address comments from Alexei
* Reuse fd_array instead of introducing kfunc_btf_fds array
* Take btf and module reference as needed, instead of preloading
* Add BTF_KIND_FUNC relocation support to gen_loader infrastructure
* Address comments from Andrii
* Drop hashmap in libbpf for finding index of existing BTF in fd_array
* Preserve invalid kfunc calls only when the symbol is weak
* Adjust verifier selftests
Kumar Kartikeya Dwivedi (9):
bpf: Introduce BPF support for kernel module function calls
bpf: Be conservative while processing invalid kfunc calls
bpf: btf: Introduce helpers for dynamic BTF set registration
tools: Allow specifying base BTF file in resolve_btfids
bpf: Enable TCP congestion control kfunc from modules
libbpf: Support kernel module function calls
libbpf: Resolve invalid weak kfunc calls with imm = 0, off = 0
libbpf: Update gen_loader to emit BTF_KIND_FUNC relocations
bpf: selftests: Add selftests for module kfunc support
include/linux/bpf.h | 8 +-
include/linux/bpf_verifier.h | 2 +
include/linux/bpfptr.h | 1 +
include/linux/btf.h | 37 ++
kernel/bpf/btf.c | 56 +++
kernel/bpf/core.c | 4 +
kernel/bpf/verifier.c | 220 ++++++++++--
net/bpf/test_run.c | 7 +-
net/ipv4/bpf_tcp_ca.c | 36 +-
net/ipv4/tcp_bbr.c | 28 +-
net/ipv4/tcp_cubic.c | 26 +-
net/ipv4/tcp_dctcp.c | 26 +-
scripts/Makefile.modfinal | 1 +
tools/bpf/resolve_btfids/main.c | 28 +-
tools/lib/bpf/bpf.c | 1 +
tools/lib/bpf/bpf_gen_internal.h | 16 +-
tools/lib/bpf/btf.c | 19 +-
tools/lib/bpf/gen_loader.c | 323 +++++++++++++++---
tools/lib/bpf/libbpf.c | 110 +++---
tools/lib/bpf/libbpf_internal.h | 3 +
tools/testing/selftests/bpf/Makefile | 10 +-
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 23 +-
.../selftests/bpf/prog_tests/ksyms_module.c | 29 +-
.../bpf/prog_tests/ksyms_module_libbpf.c | 28 ++
.../selftests/bpf/progs/test_ksyms_module.c | 46 ++-
tools/testing/selftests/bpf/verifier/calls.c | 23 ++
26 files changed, 912 insertions(+), 199 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c
--
2.33.0
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