linux-kernel - [PATCH v3 6/6] percpu/x86: Enable strict percpu checks via named AS qualifiers

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Message-ID: <20241208204708.3742696-7-ubizjak@gmail.com>
Date: Sun,  8 Dec 2024 21:45:21 +0100
From: Uros Bizjak <ubizjak@...il.com>
To: x86@...nel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	linux-bcachefs@...r.kernel.org,
	linux-arch@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	Nadav Amit <nadav.amit@...il.com>,
	Dennis Zhou <dennis@...nel.org>,
	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v3 6/6] percpu/x86: Enable strict percpu checks via named AS qualifiers

This patch declares percpu variables in __seg_gs/__seg_fs named AS
and keeps them named AS qualified until they are dereferenced with
percpu accessor. This approach enables various compiler check
for cross-namespace variable assignments.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Acked-by: Nadav Amit <nadav.amit@...il.com>
Cc: Dennis Zhou <dennis@...nel.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
v2: - Add comment to remove test for __CHECKER__ once sparse learns
      about __typeof_unqual__.
---
 arch/x86/include/asm/percpu.h | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 27f668660abe..1ef08289e667 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -95,9 +95,23 @@
 
 #endif /* CONFIG_SMP */
 
-#define __my_cpu_type(var)	typeof(var) __percpu_seg_override
-#define __my_cpu_ptr(ptr)	(__my_cpu_type(*(ptr))*)(__force uintptr_t)(ptr)
-#define __my_cpu_var(var)	(*__my_cpu_ptr(&(var)))
+/*
+ * XXX: Remove test for __CHECKER__ once
+ * sparse learns about __typeof_unqual__.
+ */
+#if defined(CONFIG_USE_X86_SEG_SUPPORT) && \
+    defined(CONFIG_CC_HAS_TYPEOF_UNQUAL) && !defined(__CHECKER__)
+# define __my_cpu_type(var)	typeof(var)
+# define __my_cpu_ptr(ptr)	(ptr)
+# define __my_cpu_var(var)	(var)
+
+# define __percpu_qual		__percpu_seg_override
+#else
+# define __my_cpu_type(var)	typeof(var) __percpu_seg_override
+# define __my_cpu_ptr(ptr)	(__my_cpu_type(*(ptr))*)(__force uintptr_t)(ptr)
+# define __my_cpu_var(var)	(*__my_cpu_ptr(&(var)))
+#endif
+
 #define __percpu_arg(x)		__percpu_prefix "%" #x
 #define __force_percpu_arg(x)	__force_percpu_prefix "%" #x
 
-- 
2.42.0