From 9df1c28bb75217b244257152ab7d788bb2a386d0 Mon Sep 17 00:00:00 2001 From: Matt Mullins Date: Fri, 26 Apr 2019 11:49:47 -0700 Subject: bpf: add writable context for raw tracepoints This is an opt-in interface that allows a tracepoint to provide a safe buffer that can be written from a BPF_PROG_TYPE_RAW_TRACEPOINT program. The size of the buffer must be a compile-time constant, and is checked before allowing a BPF program to attach to a tracepoint that uses this feature. The pointer to this buffer will be the first argument of tracepoints that opt in; the pointer is valid and can be bpf_probe_read() by both BPF_PROG_TYPE_RAW_TRACEPOINT and BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that attach to such a tracepoint, but the buffer to which it points may only be written by the latter. Signed-off-by: Matt Mullins Acked-by: Yonghong Song Signed-off-by: Alexei Starovoitov --- kernel/trace/bpf_trace.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) (limited to 'kernel/trace') diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 91800be0c8eb..8607aba1d882 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -915,6 +915,27 @@ const struct bpf_verifier_ops raw_tracepoint_verifier_ops = { const struct bpf_prog_ops raw_tracepoint_prog_ops = { }; +static bool raw_tp_writable_prog_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + if (off == 0) { + if (size != sizeof(u64) || type != BPF_READ) + return false; + info->reg_type = PTR_TO_TP_BUFFER; + } + return raw_tp_prog_is_valid_access(off, size, type, prog, info); +} + +const struct bpf_verifier_ops raw_tracepoint_writable_verifier_ops = { + .get_func_proto = raw_tp_prog_func_proto, + .is_valid_access = raw_tp_writable_prog_is_valid_access, +}; + +const struct bpf_prog_ops raw_tracepoint_writable_prog_ops = { +}; + static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type, const struct bpf_prog *prog, struct bpf_insn_access_aux *info) @@ -1204,6 +1225,9 @@ static int __bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog * if (prog->aux->max_ctx_offset > btp->num_args * sizeof(u64)) return -EINVAL; + if (prog->aux->max_tp_access > btp->writable_size) + return -EINVAL; + return tracepoint_probe_register(tp, (void *)btp->bpf_func, prog); } -- cgit