[PATCH v4 4/7] bpf/validate: add jump notification events

[Marat Khalili <qm2k21@gmail.com>]

From: Marat Khalili <marat.khalili@huawei.com>

Add events notifying validate debug client of instructions that may
change program counter. This is particularly useful to an interactive
debugger to track conditional and unconditional jumps without trying to
parse the program and interpret instructions independently.

Signed-off-by: Marat Khalili <marat.khalili@huawei.com>
---
 lib/bpf/bpf_validate.c           | 10 ++++++++--
 lib/bpf/bpf_validate_debug.c     |  2 ++
 lib/bpf/rte_bpf_validate_debug.h |  5 +++++
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/lib/bpf/bpf_validate.c b/lib/bpf/bpf_validate.c
index f4258c2fb5..d503db8361 100644
--- a/lib/bpf/bpf_validate.c
+++ b/lib/bpf/bpf_validate.c
@@ -2899,13 +2899,19 @@ is_branch_start(const struct inst_node *node)
 }
 
 static uint64_t
-step_events(const struct inst_node *node)
+step_events(const struct inst_node *node, uint8_t op)
 {
 	uint64_t events = RTE_BIT64(RTE_BPF_VALIDATE_DEBUG_EVENT_STEP);
 
 	if (is_branch_start(node))
 		events |= RTE_BIT64(RTE_BPF_VALIDATE_DEBUG_EVENT_BRANCH_ENTER);
 
+	if (op == (BPF_JMP | BPF_JA))
+		events |= RTE_BIT64(RTE_BPF_VALIDATE_DEBUG_EVENT_JUMP_ALWAYS);
+
+	if (node->nb_edge > 1)
+		events |= RTE_BIT64(RTE_BPF_VALIDATE_DEBUG_EVENT_JUMP_CONDITIONAL);
+
 	return events;
 }
 
@@ -3005,7 +3011,7 @@ evaluate(struct bpf_verifier *bvf)
 			}
 
 			rc = __rte_bpf_validate_debug_evaluate_update(debug, idx,
-				step_events(node));
+				step_events(node, op));
 			if (rc < 0)
 				break;
 
diff --git a/lib/bpf/bpf_validate_debug.c b/lib/bpf/bpf_validate_debug.c
index db6d13f9cb..098a88026d 100644
--- a/lib/bpf/bpf_validate_debug.c
+++ b/lib/bpf/bpf_validate_debug.c
@@ -600,6 +600,8 @@ __rte_bpf_validate_debug_evaluate_update(struct rte_bpf_validate_debug *debug,
 		RTE_BPF_VALIDATE_DEBUG_EVENT_BRANCH_PRUNE,
 		RTE_BPF_VALIDATE_DEBUG_EVENT_BRANCH_RETURN,
 		RTE_BPF_VALIDATE_DEBUG_EVENT_BRANCH_UNREACHABLE,
+		RTE_BPF_VALIDATE_DEBUG_EVENT_JUMP_ALWAYS,
+		RTE_BPF_VALIDATE_DEBUG_EVENT_JUMP_CONDITIONAL,
 		RTE_BPF_VALIDATE_DEBUG_EVENT_STEP,
 		RTE_BPF_VALIDATE_DEBUG_EVENT_VALIDATION_SUCCESS,
 		RTE_BPF_VALIDATE_DEBUG_EVENT_VALIDATION_FAILURE,
diff --git a/lib/bpf/rte_bpf_validate_debug.h b/lib/bpf/rte_bpf_validate_debug.h
index b3fedd5428..f1ee8769d0 100644
--- a/lib/bpf/rte_bpf_validate_debug.h
+++ b/lib/bpf/rte_bpf_validate_debug.h
@@ -35,6 +35,7 @@ extern "C" {
  * At any given evaluation step, callbacks are fired in the following order:
  * - Validation start event;
  * - Branching and invalid-state events (can be interleaved);
+ * - Jump-instruction events (before evaluating jump instruction);
  * - Instruction breakpoints (before evaluating instruction);
  * - Step (before evaluating instruction) or validation result (if done) event;
  */
@@ -57,6 +58,10 @@ enum rte_bpf_validate_debug_event {
 	RTE_BPF_VALIDATE_DEBUG_EVENT_BRANCH_RETURN,
 	/* Pruning branch as dynamically unreachable (pc points to branch start). */
 	RTE_BPF_VALIDATE_DEBUG_EVENT_BRANCH_UNREACHABLE,
+	/* Program counter points to a jump-always instruction. */
+	RTE_BPF_VALIDATE_DEBUG_EVENT_JUMP_ALWAYS,
+	/* Program counter points to a conditional jump instruction. */
+	RTE_BPF_VALIDATE_DEBUG_EVENT_JUMP_CONDITIONAL,
 	/* Number of valid event values. */
 	RTE_BPF_VALIDATE_DEBUG_EVENT_END,
 };
-- 
2.43.0