bpftool: Fix control flow graph segfault during edge creation

JIRA: https://issues.redhat.com/browse/RHEL-85486

commit defac89
Author: Christoph Werle <christoph.werle@longjmp.de>
Date:   Wed Jan 8 23:09:37 2025 +0100

    bpftool: Fix control flow graph segfault during edge creation

    If the last instruction of a control flow graph building block is a
    BPF_CALL, an incorrect edge with e->dst set to NULL is created and
    results in a segfault during graph output.

    Ensure that BPF_CALL as last instruction of a building block is handled
    correctly and only generates a single edge unlike actual BPF_JUMP*
    instructions.

    Signed-off-by: Christoph Werle <christoph.werle@longjmp.de>
    Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
    Tested-by: Quentin Monnet <qmo@kernel.org>
    Reviewed-by: Quentin Monnet <qmo@kernel.org>
    Link: https://lore.kernel.org/bpf/20250108220937.1470029-1-christoph.werle@longjmp.de

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>

Author: jeromemarchand

tools/bpf/bpftool/cfg.c

@@ -302,6 +302,7 @@ static bool func_add_bb_edges(struct func_node *func)
 
 		insn = bb->tail;
 		if (!is_jmp_insn(insn->code) ||
+		    BPF_OP(insn->code) == BPF_CALL ||
 		    BPF_OP(insn->code) == BPF_EXIT) {
 			e->dst = bb_next(bb);
 			e->flags |= EDGE_FLAG_FALLTHROUGH;