seitan: add op_cmp

The operation op_cmp allows to compare 2 areas of memory and if they
don't match to jump to an operation.

2 files changed, 15 insertions, 0 deletions

diff --git a/gluten.h b/gluten.h
index 69a6b6b..570d82a 100644
--- a/gluten.h
+++ b/gluten.h
@@ -52,6 +52,7 @@ enum op_type {
 	OP_RETURN,
 	OP_COPY_ARGS,
 	OP_END,
+	OP_CMP,
 };
 
 enum value_type {
@@ -106,6 +107,13 @@ struct op_copy_args {
 	struct copy_arg args[6];
 };
 
+struct op_cmp {
+	uint16_t s1_off;
+	uint16_t s2_off;
+	size_t size;
+	unsigned int jmp;
+};
+
 struct op {
 	enum op_type type;
 	union {
@@ -115,6 +123,7 @@ struct op {
 		struct op_return ret;
 		struct op_inject inj;
 		struct op_copy_args copy;
+		struct op_cmp cmp;
 	};
 };
 #endif /* GLUTEN_H */
diff --git a/operations.c b/operations.c
index 8cd0828..afc4b00 100644
--- a/operations.c
+++ b/operations.c
@@ -313,6 +313,12 @@ int do_operations(void *data, struct op operations[], struct seccomp_notif *req,
 			break;
 		case OP_END:
 			return 0;
+		case OP_CMP:
+			if (memcmp((uint16_t *)data + operations[i].cmp.s1_off,
+				   (uint16_t *)data + operations[i].cmp.s2_off,
+				   operations[i].cmp.size) != 0) {
+				i = operations[i].cmp.jmp;
+			}
 			break;
 		default:
 			fprintf(stderr, "unknow operation %d \n",