[PATCH net-next 3/4] net: ipa: introduce ipa_assert()

[Alex Elder]

Create a new macro ipa_assert() to verify that a condition is true.
This produces a build-time error if the condition can be evaluated
at build time; otherwise __ipa_assert_runtime() is called (described
below).

Another macro, ipa_assert_always() verifies that an expression
yields true at runtime, and if it does not, reports an error
message.

When IPA validation is enabled, __ipa_assert_runtime() becomes a
call to ipa_assert_always(), resulting in runtime verification of
the asserted condition.  Otherwise __ipa_assert_runtime() has no
effect, so such ipa_assert() calls are effectively ignored.

IPA assertion errors will be reported using the IPA device if
possible.

Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
---
 drivers/net/ipa/ipa_assert.h | 50 ++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 drivers/net/ipa/ipa_assert.h

diff --git a/drivers/net/ipa/ipa_assert.h b/drivers/net/ipa/ipa_assert.h
new file mode 100644
index 0000000000000..7e5b9d487f69d
--- /dev/null
+++ b/drivers/net/ipa/ipa_assert.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2021 Linaro Ltd.
+ */
+#ifndef _IPA_ASSERT_H_
+#define _IPA_ASSERT_H_
+
+#include <linux/compiler.h>
+#include <linux/printk.h>
+#include <linux/device.h>
+
+/* Verify the expression yields true, and fail at build time if possible */
+#define ipa_assert(dev, expr) \
+	do { \
+		if (__builtin_constant_p(expr)) \
+			compiletime_assert(expr, __ipa_failure_msg(expr)); \
+		else \
+			__ipa_assert_runtime(dev, expr); \
+	} while (0)
+
+/* Report an error if the given expression evaluates to false at runtime */
+#define ipa_assert_always(dev, expr) \
+	do { \
+		if (unlikely(!(expr))) { \
+			struct device *__dev = (dev); \
+			\
+			if (__dev) \
+				dev_err(__dev, __ipa_failure_msg(expr)); \
+			else  \
+				pr_err(__ipa_failure_msg(expr)); \
+		} \
+	} while (0)
+
+/* Constant message used when an assertion fails */
+#define __ipa_failure_msg(expr)	"IPA assertion failed: " #expr "\n"
+
+#ifdef IPA_VALIDATION
+
+/* Only do runtime checks for "normal" assertions if validating the code */
+#define __ipa_assert_runtime(dev, expr)	ipa_assert_always(dev, expr)
+
+#else /* !IPA_VALIDATION */
+
+/* "Normal" assertions aren't checked when validation is disabled */
+#define __ipa_assert_runtime(dev, expr)	\
+	do { (void)(dev); (void)(expr); } while (0)
+
+#endif /* !IPA_VALIDATION */
+
+#endif /* _IPA_ASSERT_H_ */
-- 
2.27.0