[PATCH] ARM: 2663/1: straightify TLS register emulation a bit more

Patch from Nicolas Pitre

This better express things, and should cover RMK's weird SMP toys.

Signed-off-by: Nicolas Pitre
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 15 insertions, 9 deletions

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 27892e34b060..c4fc6be629de 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -410,17 +410,23 @@ config CPU_BPREDICT_DISABLE
         help
           Say Y here to disable branch prediction.  If unsure, say N.
 
+config TLS_REG_EMUL
+        bool
+        default y if (SMP || CPU_32v6) && (CPU_32v5 || CPU_32v4 || CPU_32v3)
+        help
+          We might be running on an ARMv6+ processor which should have the TLS
+          register but for some reason we can't use it, or maybe an SMP system
+          using a pre-ARMv6 processor (there are apparently a few prototypes
+          like that in existence) and therefore access to that register must
+          be emulated.
+
 config HAS_TLS_REG
         bool
-        depends on CPU_32v6 && !CPU_32v5 && !CPU_32v4 && !CPU_32v3
-        default y
+        depends on CPU_32v6
+        default y if !TLS_REG_EMUL
         help
           This selects support for the CP15 thread register.
-          It is defined to be available on ARMv6 or later.  However
-          if the kernel is configured to support multiple CPUs including
-          a pre-ARMv6 processors, or if a given ARMv6 processor doesn't
-          implement the thread register for some reason, then access to
-          this register from user space must be trapped and emulated.
-          If user space is relying on the __kuser_get_tls code then
-          there should not be any impact.
+          It is defined to be available on ARMv6 or later.  If a particular
+          ARMv6 or later CPU doesn't support it then it must omc;ide "select
+          TLS_REG_EMUL" along with its other caracteristics.