xtensa: add support for TLS
The Xtensa architecture provides a global register called THREADPTR
for the purpose of Thread Local Storage (TLS) support. This allows us
to use a fairly simple implementation, keeping the thread pointer in
the regset and simply saving and restoring it upon entering/exiting
the from user space.
Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 70d5a9e..63845f9 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -130,6 +130,11 @@
s32i a3, a1, PT_SAR
s32i a2, a1, PT_ICOUNTLEVEL
+#if XCHAL_HAVE_THREADPTR
+ rur a2, threadptr
+ s32i a2, a1, PT_THREADPTR
+#endif
+
/* Rotate ws so that the current windowbase is at bit0. */
/* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */
@@ -510,6 +515,11 @@
* (if we have restored WSBITS-1 frames).
*/
+#if XCHAL_HAVE_THREADPTR
+ l32i a3, a1, PT_THREADPTR
+ wur a3, threadptr
+#endif
+
2: j common_exception_exit
/* This is the kernel exception exit.
@@ -1955,7 +1965,7 @@
s32i a6, a3, EXC_TABLE_FIXUP
s32i a7, a3, EXC_TABLE_KSTK
- /* restore context of the task that 'next' addresses */
+ /* restore context of the task 'next' */
l32i a0, a13, THREAD_RA # restore return address
l32i a1, a13, THREAD_SP # restore stack pointer