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.

Link: https://lkml.kernel.org/r/20250127160709.80604-7-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Acked-by: Nadav Amit <nadav.amit@gmail.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 27f668660abe5667b854c7e74c764d3eda316869..474d648bca9a185d5f0c3abc3a9b1d64e19103cd 100644 (file)
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -95,9 +95,18 @@
 
 #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)))
+#if defined(CONFIG_USE_X86_SEG_SUPPORT) && defined(USE_TYPEOF_UNQUAL)
+# 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