From 8efea21d333d21e1f9177579ffdc69556314f603 Mon Sep 17 00:00:00 2001 From: Edward Cree Date: Wed, 22 Aug 2018 20:02:44 +0100 Subject: [PATCH] bpf/verifier: display non-spill stack slot types in print_verifier_state If a stack slot does not hold a spilled register (STACK_SPILL), then each of its eight bytes could potentially have a different slot_type. This information can be important for debugging, and previously we either did not print anything for the stack slot, or just printed fp-X=0 in the case where its first byte was STACK_ZERO. Instead, print eight characters with either 0 (STACK_ZERO), m (STACK_MISC) or ? (STACK_INVALID) for any stack slot which is neither STACK_SPILL nor entirely STACK_INVALID. Signed-off-by: Edward Cree Signed-off-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 68568d22d6bd..f4ff0c569e54 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -263,6 +263,13 @@ static const char * const reg_type_str[] = { [PTR_TO_PACKET_END] = "pkt_end", }; +static char slot_type_char[] = { + [STACK_INVALID] = '?', + [STACK_SPILL] = 'r', + [STACK_MISC] = 'm', + [STACK_ZERO] = '0', +}; + static void print_liveness(struct bpf_verifier_env *env, enum bpf_reg_liveness live) { @@ -349,15 +356,26 @@ 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", - (-i - 1) * BPF_REG_SIZE); - print_liveness(env, state->stack[i].spilled_ptr.live); + char types_buf[BPF_REG_SIZE + 1]; + bool valid = false; + int j; + + for (j = 0; j < BPF_REG_SIZE; j++) { + if (state->stack[i].slot_type[j] != STACK_INVALID) + valid = true; + types_buf[j] = slot_type_char[ + state->stack[i].slot_type[j]]; + } + types_buf[BPF_REG_SIZE] = 0; + if (!valid) + continue; + verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE); + print_liveness(env, state->stack[i].spilled_ptr.live); + if (state->stack[i].slot_type[0] == STACK_SPILL) verbose(env, "=%s", reg_type_str[state->stack[i].spilled_ptr.type]); - } - if (state->stack[i].slot_type[0] == STACK_ZERO) - verbose(env, " fp%d=0", (-i - 1) * BPF_REG_SIZE); + else + verbose(env, "=%s", types_buf); } verbose(env, "\n"); }