linux-kernel - [PATCH v4 03/35] compiler-context-analysis: Add test stub

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Message-ID: <20251120145835.3833031-5-elver@google.com>
Date: Thu, 20 Nov 2025 15:49:05 +0100
From: Marco Elver <elver@...gle.com>
To: elver@...gle.com, Peter Zijlstra <peterz@...radead.org>, 
	Boqun Feng <boqun.feng@...il.com>, Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>, Luc Van Oostenryck <luc.vanoostenryck@...il.com>, 
	Chris Li <sparse@...isli.org>, "Paul E. McKenney" <paulmck@...nel.org>, 
	Alexander Potapenko <glider@...gle.com>, Arnd Bergmann <arnd@...db.de>, Bart Van Assche <bvanassche@....org>, 
	Christoph Hellwig <hch@....de>, Dmitry Vyukov <dvyukov@...gle.com>, Eric Dumazet <edumazet@...gle.com>, 
	Frederic Weisbecker <frederic@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Herbert Xu <herbert@...dor.apana.org.au>, Ian Rogers <irogers@...gle.com>, 
	Jann Horn <jannh@...gle.com>, Joel Fernandes <joelagnelf@...dia.com>, 
	Johannes Berg <johannes.berg@...el.com>, Jonathan Corbet <corbet@....net>, 
	Josh Triplett <josh@...htriplett.org>, Justin Stitt <justinstitt@...gle.com>, 
	Kees Cook <kees@...nel.org>, Kentaro Takeda <takedakn@...data.co.jp>, 
	Lukas Bulwahn <lukas.bulwahn@...il.com>, Mark Rutland <mark.rutland@....com>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Miguel Ojeda <ojeda@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Neeraj Upadhyay <neeraj.upadhyay@...nel.org>, 
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>, Thomas Gleixner <tglx@...utronix.de>, 
	Thomas Graf <tgraf@...g.ch>, Uladzislau Rezki <urezki@...il.com>, Waiman Long <longman@...hat.com>, 
	kasan-dev@...glegroups.com, linux-crypto@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	linux-security-module@...r.kernel.org, linux-sparse@...r.kernel.org, 
	linux-wireless@...r.kernel.org, llvm@...ts.linux.dev, rcu@...r.kernel.org
Subject: [PATCH v4 03/35] compiler-context-analysis: Add test stub

Add a simple test stub where we will add common supported patterns that
should not generate false positive of each new supported context guard.

Signed-off-by: Marco Elver <elver@...gle.com>
---
v4:
* Rename capability -> context analysis.
---
 lib/Kconfig.debug           | 14 ++++++++++++++
 lib/Makefile                |  3 +++
 lib/test_context-analysis.c | 18 ++++++++++++++++++
 3 files changed, 35 insertions(+)
 create mode 100644 lib/test_context-analysis.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 696e2a148a15..0c499d22407c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2833,6 +2833,20 @@ config LINEAR_RANGES_TEST
 
 	  If unsure, say N.
 
+config CONTEXT_ANALYSIS_TEST
+	bool "Compiler context-analysis warnings test"
+	depends on EXPERT
+	help
+	  This builds the test for compiler-based context analysis. The test
+	  does not add executable code to the kernel, but is meant to test that
+	  common patterns supported by the analysis do not result in false
+	  positive warnings.
+
+	  When adding support for new context guards, it is strongly recommended
+	  to add supported patterns to this test.
+
+	  If unsure, say N.
+
 config CMDLINE_KUNIT_TEST
 	tristate "KUnit test for cmdline API" if !KUNIT_ALL_TESTS
 	depends on KUNIT
diff --git a/lib/Makefile b/lib/Makefile
index 1ab2c4be3b66..59ed5f881bcb 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -329,4 +329,7 @@ obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
 
 obj-$(CONFIG_FIRMWARE_TABLE) += fw_table.o
 
+CONTEXT_ANALYSIS_test_context-analysis.o := y
+obj-$(CONFIG_CONTEXT_ANALYSIS_TEST) += test_context-analysis.o
+
 subdir-$(CONFIG_FORTIFY_SOURCE) += test_fortify
diff --git a/lib/test_context-analysis.c b/lib/test_context-analysis.c
new file mode 100644
index 000000000000..68f075dec0e0
--- /dev/null
+++ b/lib/test_context-analysis.c
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Compile-only tests for common patterns that should not generate false
+ * positive errors when compiled with Clang's context analysis.
+ */
+
+#include <linux/build_bug.h>
+
+/*
+ * Test that helper macros work as expected.
+ */
+static void __used test_common_helpers(void)
+{
+	BUILD_BUG_ON(context_unsafe(3) != 3); /* plain expression */
+	BUILD_BUG_ON(context_unsafe((void)2; 3) != 3); /* does not swallow semi-colon */
+	BUILD_BUG_ON(context_unsafe((void)2, 3) != 3); /* does not swallow commas */
+	context_unsafe(do { } while (0)); /* works with void statements */
+}
-- 
2.52.0.rc1.455.g30608eb744-goog