[RESEND,-tip] x86/percpu: Use %RIP-relative address in untagged_addr()
Commit Message
%RIP-relative addresses are nowadays correctly handled in alternative
instructions, so remove misleading comment and improve assembly to
use %RIP-relative address.
Also, explicitly using %gs: prefix will segfault for non-SMP builds.
Use macros from percpu.h which will DTRT with segment prefix register
as far as SMP/non-SMP builds are concerned.
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>
Acked-by: Peter Zijlstra (Intel) <peterz@infradaed.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
---
arch/x86/include/asm/uaccess_64.h | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
@@ -11,6 +11,7 @@
#include <asm/alternative.h>
#include <asm/cpufeatures.h>
#include <asm/page.h>
+#include <asm/percpu.h>
#ifdef CONFIG_ADDRESS_MASKING
/*
@@ -18,14 +19,10 @@
*/
static inline unsigned long __untagged_addr(unsigned long addr)
{
- /*
- * Refer tlbstate_untag_mask directly to avoid RIP-relative relocation
- * in alternative instructions. The relocation gets wrong when gets
- * copied to the target place.
- */
asm (ALTERNATIVE("",
- "and %%gs:tlbstate_untag_mask, %[addr]\n\t", X86_FEATURE_LAM)
- : [addr] "+r" (addr) : "m" (tlbstate_untag_mask));
+ "and " __percpu_arg([mask]) ", %[addr]", X86_FEATURE_LAM)
+ : [addr] "+r" (addr)
+ : [mask] "m" (__my_cpu_var(tlbstate_untag_mask)));
return addr;
}