tools, bpf_asm: Hard error on out of range jumps

Per discussion at [0] this was originally introduced as a warning due
to concerns about breaking existing code, but a hard error probably
makes more sense, especially given that concerns about breakage were
only speculation.

  [0] https://lore.kernel.org/bpf/c964892195a6b91d20a67691448567ef528ffa6d.camel@linux.ibm.com/T/#t

Signed-off-by: Ian Denhardt <ian@zenhack.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/bpf/a6b6c7516f5d559049d669968e953b4a8d7adea3.1614201868.git.ian@zenhack.net

diff --git a/tools/bpf/bpf_exp.y b/tools/bpf/bpf_exp.y
index 8d48e89..8d03e52 100644 (file)
--- a/tools/bpf/bpf_exp.y
+++ b/tools/bpf/bpf_exp.y
@@ -549,9 +549,11 @@ static uint8_t bpf_encode_jt_jf_offset(int off, int i)
 {
        int delta = off - i - 1;
 
-       if (delta < 0 || delta > 255)
-               fprintf(stderr, "warning: insn #%d jumps to insn #%d, "
+       if (delta < 0 || delta > 255) {
+               fprintf(stderr, "error: insn #%d jumps to insn #%d, "
                                "which is out of range\n", i, off);
+               exit(1);
+       }
        return (uint8_t) delta;
 }