Merge branch 'bpf-bounded-loops'

Alexei Starovoitov says:

====================
v2->v3: fixed issues in backtracking pointed out by Andrii.
The next step is to add a lot more tests for backtracking.

v1->v2: addressed Andrii's feedback.

this patch set introduces verifier support for bounded loops and
adds several other improvements.
Ideally they would be introduced one at a time,
but to support bounded loop the verifier needs to 'step back'
in the patch 1. That patch introduces tracking of spill/fill
of constants through the stack. Though it's a useful feature
it hurts cilium tests.
Patch 3 introduces another feature by extending is_branch_taken
logic to 'if rX op rY' conditions. This feature is also
necessary to support bounded loops.
Then patch 4 adds support for the loops while adding
key heuristics with jmp_processed.
Introduction of parentage chain of verifier states in patch 4
allows patch 9 to add backtracking of precise scalar registers
which finally resolves degradation from patch 1.

The end result is much faster verifier for existing programs
and new support for loops.
See patch 8 for many kinds of loops that are now validated.
Patch 9 is the most tricky one and could be rewritten with
a different algorithm in the future.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 22 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/loop3.c b/tools/testing/selftests/bpf/progs/loop3.c
new file mode 100644
index 000000000000..30a0f6cba080
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/loop3.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("raw_tracepoint/consume_skb")
+int while_true(volatile struct pt_regs* ctx)
+{
+	__u64 i = 0, sum = 0;
+	do {
+		i++;
+		sum += ctx->rax;
+	} while (i < 0x100000000ULL);
+	return sum;
+}