From: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
This set allows the subsystem to patch codes before BPF_EXIT.
The verifier ops, .gen_epilogue, is added for this purpose.
One of the use case will be in the bpf qdisc, the bpf qdisc
subsystem can ensure the skb->dev is in the correct value.
The bpf qdisc subsystem can either inline fixing it in the
epilogue or call another kernel function to handle it (e.g. drop)
in the epilogue. Another use case could be in bpf_tcp_ca.c to
enforce snd_cwnd has valid value (e.g. positive value).
v4:
* Fixed a bug in the memcpy in patch 3
The size in the memcpy should be
epilogue_cnt * sizeof(*epilogue_buf)
v3:
* Moved epilogue_buf[16] to env.
Patch 1 is added to move the existing insn_buf[16] to env.
* Fixed a case that the bpf prog has a BPF_JMP that goes back
to the first instruction of the main prog.
The jump back to 1st insn case also applies to the prologue.
Patch 2 is added to handle it.
* If the bpf main prog has multiple BPF_EXIT, use a BPF_JA
to goto the earlier patched epilogue.
Note that there are (BPF_JMP32 | BPF_JA) vs (BPF_JMP | BPF_JA)
details in the patch 3 commit message.
* There are subtle changes in patch 3, so I reset the Reviewed-by.
* Added patch 8 and patch 9 to cover the changes in patch 2 and patch 3.
* Dropped the kfunc call from pro/epilogue and its selftests.
v2:
* Remove the RFC tag. Keep the ordering at where .gen_epilogue is
called in the verifier relative to the check_max_stack_depth().
This will be consistent with the other extra stack_depth
usage like optimize_bpf_loop().
* Use __xlated check provided by the test_loader to
check the patched instructions after gen_pro/epilogue (Eduard).
* Added Patch 3 by Eduard (Thanks!).
Eduard Zingerman (1):
selftests/bpf: attach struct_ops maps before test prog runs
Martin KaFai Lau (8):
bpf: Move insn_buf[16] to bpf_verifier_env
bpf: Adjust BPF_JMP that jumps to the 1st insn of the prologue
bpf: Add gen_epilogue to bpf_verifier_ops
bpf: Export bpf_base_func_proto
selftests/bpf: Test gen_prologue and gen_epilogue
selftests/bpf: Add tailcall epilogue test
selftests/bpf: A pro/epilogue test when the main prog jumps back to
the 1st insn
selftests/bpf: Test epilogue patching when the main prog has multiple
BPF_EXIT
include/linux/bpf.h | 2 +
include/linux/bpf_verifier.h | 4 +
kernel/bpf/helpers.c | 1 +
kernel/bpf/verifier.c | 73 +++++--
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 190 ++++++++++++++++++
.../selftests/bpf/bpf_testmod/bpf_testmod.h | 11 +
.../bpf/bpf_testmod/bpf_testmod_kfunc.h | 6 +
.../selftests/bpf/prog_tests/pro_epilogue.c | 54 +++++
.../selftests/bpf/progs/epilogue_exit.c | 78 +++++++
.../selftests/bpf/progs/epilogue_tailcall.c | 58 ++++++
.../bpf/progs/pro_epilogue_goto_start.c | 149 ++++++++++++++
.../selftests/bpf/progs/pro_epilogue_kfunc.c | 156 ++++++++++++++
.../bpf/progs/pro_epilogue_subprog.c | 125 ++++++++++++
tools/testing/selftests/bpf/test_loader.c | 27 +++
14 files changed, 922 insertions(+), 12 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/pro_epilogue.c
create mode 100644 tools/testing/selftests/bpf/progs/epilogue_exit.c
create mode 100644 tools/testing/selftests/bpf/progs/epilogue_tailcall.c
create mode 100644 tools/testing/selftests/bpf/progs/pro_epilogue_goto_start.c
create mode 100644 tools/testing/selftests/bpf/progs/pro_epilogue_kfunc.c
create mode 100644 tools/testing/selftests/bpf/progs/pro_epilogue_subprog.c
--
2.43.5
