The following commit has been merged into the x86/mm branch of tip:
Commit-ID: 91c17d7b04498ffb52939a18eb7e28fd23c9b654
Gitweb: https://git.kernel.org/tip/91c17d7b04498ffb52939a18eb7e28fd23c9b654
Author: Uros Bizjak <ubizjak@xxxxxxxxx>
AuthorDate: Wed, 13 Dec 2023 16:03:15 +01:00
Committer: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Fri, 15 Dec 2023 09:50:14 -08:00
x86/percpu: Use %RIP-relative address in untagged_addr()
%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.
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20231213150357.5942-1-ubizjak%40gmail.com
---
arch/x86/include/asm/uaccess_64.h | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index f2c02e4..01455c0 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -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;
}
|