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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 <ecree@solarflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Edward Cree 2018-08-22 20:02:44 +01:00 committed by Alexei Starovoitov
parent 679c782de1
commit 8efea21d33
1 changed files with 25 additions and 7 deletions
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32
kernel/bpf/verifier.c
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@ -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");
}