Messages in this thread |  | | From | KP Singh <> | Date | Mon, 30 Dec 2019 16:11:35 +0100 | Subject | Re: [PATCH bpf-next v1 09/13] bpf: lsm: Add a helper function bpf_lsm_event_output |
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On 23-Dec 22:36, Andrii Nakryiko wrote: > On Fri, Dec 20, 2019 at 7:43 AM KP Singh <kpsingh@chromium.org> wrote: > > > > From: KP Singh <kpsingh@google.com> > > > > This helper is similar to bpf_perf_event_output except that > > it does need a ctx argument which is more usable in the > > BTF based LSM programs where the context is converted to > > the signature of the attacthed BTF type. > > > > An example usage of this function would be: > > > > struct { > > __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY); > > __uint(key_size, sizeof(int)); > > __uint(value_size, sizeof(u32)); > > } perf_map SEC(".maps"); > > > > BPF_TRACE_1(bpf_prog1, "lsm/bprm_check_security, > > struct linux_binprm *, bprm) > > { > > char buf[BUF_SIZE]; > > int len; > > u64 flags = BPF_F_CURRENT_CPU; > > > > /* some logic that fills up buf with len data */ > > len = fill_up_buf(buf); > > if (len < 0) > > return len; > > if (len > BU) > > return 0; > > > > bpf_lsm_event_output(&perf_map, flags, buf, len); > > This seems to be generally useful and not LSM-specific, so maybe name > it more generically as bpf_event_output instead?
Agreed, I am happy to rename this.
> > I'm also curious why we needed both bpf_perf_event_output and > bpf_perf_event_output_raw_tp, if it could be done as simply as you did > it here. What's different between those three and why your > bpf_lsm_event_output doesn't need pt_regs passed into them?
That's because my implementation uses the following function from bpf_trace.c:
u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size, void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)
This does not require a pt_regs argument and handles fetching them internally:
regs = this_cpu_ptr(&bpf_pt_regs.regs[nest_level - 1]);
perf_fetch_caller_regs(regs); perf_sample_data_init(sd, 0, 0); sd->raw = &raw;
ret = __bpf_perf_event_output(regs, map, flags, sd);
- KP
> > > return 0; > > } > > > > Signed-off-by: KP Singh <kpsingh@google.com> > > --- > > include/uapi/linux/bpf.h | 10 +++++++++- > > kernel/bpf/verifier.c | 1 + > > security/bpf/ops.c | 21 +++++++++++++++++++++ > > tools/include/uapi/linux/bpf.h | 10 +++++++++- > > 4 files changed, 40 insertions(+), 2 deletions(-) > > > > [...]
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