[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.