linux-kernel - [PATCH 3/3] percpu: Cast percpu pointer in PERCPU

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Message-ID: <20241021080856.48746-3-ubizjak@gmail.com>
Date: Mon, 21 Oct 2024 10:07:38 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	Dennis Zhou <dennis@...nel.org>,
	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 3/3] percpu: Cast percpu pointer in PERCPU_PTR() via unsigned long

Cast pointer from percpu address space to generic (kernel) address
space in PERCPU_PTR() macro via unsigned long intermediate cast [1].
This intermediate cast is also required to avoid build failure
when GCC's strict named address space checks for x86 targets [2]
are enabled.

Found by GCC's named address space checks.

[1] https://sparse.docs.kernel.org/en/latest/annotations.html#address-space-name
[2] https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html#x86-Named-Address-Spaces

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Dennis Zhou <dennis@...nel.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
---
 include/linux/percpu-defs.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
index e1cf7982424f..35842d1e3879 100644
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -221,7 +221,10 @@ do {									\
 } while (0)
 
 #define PERCPU_PTR(__p)							\
-	(typeof(*(__p)) __force __kernel *)(__p);
+({									\
+	unsigned long __pcpu_ptr = (__force unsigned long)(__p);	\
+	(typeof(*(__p)) __force __kernel *)(__pcpu_ptr);		\
+})
 
 #ifdef CONFIG_SMP
 
-- 
2.47.0