3 files changed, 22 insertions, 2 deletions
diff --git a/libc/Android.mk b/libc/Android.mk
index 59a4c6b..12d5c92 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -366,6 +366,16 @@ endif
 ifeq ($(TARGET_ARCH),arm)
   libc_common_cflags += -fstrict-aliasing
   libc_crt_target_cflags := -mthumb-interwork
+  #
+  # Define HAVE_ARM_TLS_REGISTER macro to indicate to the C library
+  # that it should access the hardware TLS register directly in
+  # private/bionic_tls.h
+  #
+  # The value must match your kernel configuration
+  #
+  ifeq ($(ARCH_ARM_HAVE_TLS_REGISTER),true)
+    libc_common_cflags += -DHAVE_ARM_TLS_REGISTER
+  endif
 else # !arm
   ifeq ($(TARGET_ARCH),x86)
     libc_crt_target_cflags := -m32
diff --git a/libc/arch-arm/include/machine/cpu-features.h b/libc/arch-arm/include/machine/cpu-features.h
index f836006..925067e 100644
--- a/libc/arch-arm/include/machine/cpu-features.h
+++ b/libc/arch-arm/include/machine/cpu-features.h
@@ -149,7 +149,6 @@
 #  define __ARM_HAVE_PC_INTERWORK
 #endif
 
-
 /* Assembly-only macros */
 
 /* define a handy PLD(address) macro since the cache preload
diff --git a/libc/private/bionic_tls.h b/libc/private/bionic_tls.h
index 82c8cd9..2e7a82b 100644
--- a/libc/private/bionic_tls.h
+++ b/libc/private/bionic_tls.h
@@ -88,7 +88,18 @@ extern int __set_tls(void *ptr);
 
 /* get the TLS */
 #ifdef __arm__
-#  define __get_tls() ( *((volatile void **) 0xffff0ff0) )
+/* For performance reasons, avoid calling the kernel helper
+ * Note that HAVE_ARM_TLS_REGISTER is build-specific
+ * (it must match your kernel configuration)
+ */
+#  ifdef HAVE_ARM_TLS_REGISTER
+#    define __get_tls() \
+    ({ register unsigned int __val asm("r0"); \
+       asm ("mrc p15, 0, r0, c13, c0, 3" : "=r"(__val) ); \
+       (volatile void*)__val; })
+#  else /* !HAVE_ARM_TLS_REGISTER */
+#    define __get_tls() ( *((volatile void **) 0xffff0ff0) )
+#  endif
 #else
 extern void*  __get_tls( void );
 #endif