bpf: verbose log bpf_line_info in verifier

This patch adds bpf_line_info during the verifier's verbose.
It can give error context for debug purpose.

~~~~~~~~~~
Here is the verbose log for backedge:
	while (a) {
		a += bpf_get_smp_processor_id();
		bpf_trace_printk(fmt, sizeof(fmt), a);
	}

~> bpftool prog load ./test_loop.o /sys/fs/bpf/test_loop type tracepoint
13: while (a) {
3: a += bpf_get_smp_processor_id();
back-edge from insn 13 to 3

~~~~~~~~~~
Here is the verbose log for invalid pkt access:
Modification to test_xdp_noinline.c:

	data = (void *)(long)xdp->data;
	data_end = (void *)(long)xdp->data_end;
/*
	if (data + 4 > data_end)
		return XDP_DROP;
*/
	*(u32 *)data = dst->dst;

~> bpftool prog load ./test_xdp_noinline.o /sys/fs/bpf/test_xdp_noinline type xdp
; data = (void *)(long)xdp->data;
224: (79) r2 = *(u64 *)(r10 -112)
225: (61) r2 = *(u32 *)(r2 +0)
; *(u32 *)data = dst->dst;
226: (63) *(u32 *)(r2 +0) = r1
invalid access to packet, off=0 size=4, R2(id=0,off=0,r=0)
R2 offset is outside of the packet

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c736945be7c5..548dcbdb7111 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -224,6 +224,7 @@ struct bpf_verifier_env {
 	bool allow_ptr_leaks;
 	bool seen_direct_write;
 	struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
+	const struct bpf_line_info *prev_linfo;
 	struct bpf_verifier_log log;
 	struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
 	u32 subprog_cnt;