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 kfunc to handle (e.g. drop) it in the epilogue. Another use case could be in bpf_tcp_ca.c to enforce snd_cwnd has sane value (e.g. non zero). The existing .gen_prologue can call bpf helper. This set also allows the existing .gen_prologue and the new .gen_epilogue to call kfunc. Other than the skb drop mentioned above, the bpf qdisc subsystem can call kfunc to enforce initializing / releasing resources (e.g. qdisc_watchdog_init/cancel) in some of the qdisc_ops. It is under RFC because the .gen_epilogue will need 8 extra bytes in the stack to save the ctx pointer. It is now done after the check_max_stack_depth. The ctx pointer saving will need to be done earlier before check_max_stack_depth. Martin KaFai Lau (6): bpf: Add gen_epilogue to bpf_verifier_ops bpf: Export bpf_base_func_proto selftests/test: test gen_prologue and gen_epilogue bpf: Add module parameter to gen_prologue and gen_epilogue bpf: Allow pro/epilogue to call kfunc selftests/bpf: Add kfunc call test in gen_prologue and gen_epilogue include/linux/bpf.h | 4 +- include/linux/btf.h | 1 + kernel/bpf/btf.c | 2 +- kernel/bpf/cgroup.c | 3 +- kernel/bpf/helpers.c | 1 + kernel/bpf/verifier.c | 146 ++++++++++- net/core/filter.c | 6 +- .../selftests/bpf/bpf_testmod/bpf_testmod.c | 228 ++++++++++++++++++ .../selftests/bpf/bpf_testmod/bpf_testmod.h | 11 + .../bpf/bpf_testmod/bpf_testmod_kfunc.h | 6 + .../bpf/prog_tests/struct_ops_syscall.c | 92 +++++++ .../selftests/bpf/progs/struct_ops_syscall.c | 113 +++++++++ 12 files changed, 604 insertions(+), 9 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/struct_ops_syscall.c create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_syscall.c -- 2.43.5
