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 corss-namespace variable assignments.
RFH: The patch hijacks __percpu tag and repurposes it as a named
address space qualifier. While this works surprisingly well in
this RFC patchset, I would really appreciate some help on how
to rewrite this hack into some "production ready" code.
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Cc: Dennis Zhou <dennis@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
arch/x86/include/asm/percpu.h | 15 ++++++++++++---
include/linux/compiler_types.h | 2 +-
2 files changed, 13 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 4d31203eb0d2..40916bbd2f11 100644
--- 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(CONFIG_CC_HAS_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)))
+# define __percpu_qual
+#endif
+
#define __percpu_arg(x) __percpu_prefix "%" #x
#define __force_percpu_arg(x) __force_percpu_prefix "%" #x
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index f14c275950b5..47c95a06a0ec 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -57,7 +57,7 @@ static inline void __chk_io_ptr(const volatile void __iomem *ptr) { }
# define __user BTF_TYPE_TAG(user)
# endif
# define __iomem
-# define __percpu BTF_TYPE_TAG(percpu)
+# define __percpu __percpu_qual BTF_TYPE_TAG(percpu)
# define __rcu BTF_TYPE_TAG(rcu)
# define __chk_user_ptr(x) (void)0
--
2.45.2
