[PATCH net-next 2/7] bpf: print liveness info to verifier log

[Alexei Starovoitov]

let verifier print register and stack liveness information
into verifier log

Signed-off-by: Alexei Starovoitov <a...@kernel.org>
Acked-by: John Fastabend <john.fastab...@gmail.com>
Acked-by: Daniel Borkmann <dan...@iogearbox.net>
---
 kernel/bpf/verifier.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 71a9429fdbb5..f7229390c279 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -216,6 +216,17 @@ static const char * const reg_type_str[] = {
        [PTR_TO_PACKET_END]     = "pkt_end",
 };
 
+static void print_liveness(struct bpf_verifier_env *env,
+                          enum bpf_reg_liveness live)
+{
+       if (live & (REG_LIVE_READ | REG_LIVE_WRITTEN))
+           verbose(env, "_");
+       if (live & REG_LIVE_READ)
+               verbose(env, "r");
+       if (live & REG_LIVE_WRITTEN)
+               verbose(env, "w");
+}
+
 static void print_verifier_state(struct bpf_verifier_env *env,
                                 struct bpf_verifier_state *state)
 {
@@ -228,7 +239,9 @@ static void print_verifier_state(struct bpf_verifier_env 
*env,
                t = reg->type;
                if (t == NOT_INIT)
                        continue;
-               verbose(env, " R%d=%s", i, reg_type_str[t]);
+               verbose(env, " R%d", i);
+               print_liveness(env, reg->live);
+               verbose(env, "=%s", reg_type_str[t]);
                if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
                    tnum_is_const(reg->var_off)) {
                        /* reg->off should be 0 for SCALAR_VALUE */
@@ -277,10 +290,13 @@ static void print_verifier_state(struct bpf_verifier_env 
*env,
                }
        }
        for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
-               if (state->stack[i].slot_type[0] == STACK_SPILL)
-                       verbose(env, " fp%d=%s",
-                               (-i - 1) * BPF_REG_SIZE,
+               if (state->stack[i].slot_type[0] == STACK_SPILL) {
+                       verbose(env, " fp%d",
+                               (-i - 1) * BPF_REG_SIZE);
+                       print_liveness(env, state->stack[i].spilled_ptr.live);
+                       verbose(env, "=%s",
                                reg_type_str[state->stack[i].spilled_ptr.type]);
+               }
        }
        verbose(env, "\n");
 }
-- 
2.9.5