bpf: correct use/def for may_goto instruction

may_goto instruction does not use any registers,
but in compute_insn_live_regs() it was treated as a regular
conditional jump of kind BPF_K with r0 as source register.
Thus unnecessarily marking r0 as used.

Fixes: 14c8552 ("bpf: simple DFA-based live registers analysis")
Signed-off-by: Eduard Zingerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: eddyz87

kernel/bpf/verifier.c

@@ -23567,6 +23567,7 @@ static void compute_insn_live_regs(struct bpf_verifier_env *env,
 	case BPF_JMP32:
 		switch (code) {
 		case BPF_JA:
+		case BPF_JCOND:
 			def = 0;
 			use = 0;
 			break;

tools/testing/selftests/bpf/progs/compute_live_registers.c

@@ -294,9 +294,9 @@ __naked void gotol(void)
 
 SEC("socket")
 __log_level(2)
-__msg("0: 0......... (b7) r1 = 1")
-__msg("1: 01........ (e5) may_goto pc+1")
-__msg("2: 0......... (05) goto pc-3")
+__msg("0: .......... (b7) r1 = 1")
+__msg("1: .1........ (e5) may_goto pc+1")
+__msg("2: .......... (05) goto pc-3")
 __msg("3: .1........ (bf) r0 = r1")
 __msg("4: 0......... (95) exit")
 __naked void may_goto(void)