Add save_tar() function to save the Target Address Register (TAR). This will
be used in a future patch to save the TAR earlier than it currently is.
Signed-off-by: Michael Neuling <mi...@neuling.org>
Cc: <sta...@vger.kernel.org>
---
arch/powerpc/include/asm/switch_to.h | 5 +++++
arch/powerpc/kernel/entry_64.S | 12 ++++++++++++
2 files changed, 17 insertions(+)
diff --git a/arch/powerpc/include/asm/switch_to.h
b/arch/powerpc/include/asm/switch_to.h
index 49a13e0..4531068 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -15,6 +15,11 @@ extern struct task_struct *__switch_to(struct task_struct *,
struct thread_struct;
extern struct task_struct *_switch(struct thread_struct *prev,
struct thread_struct *next);
+#ifdef CONFIG_PPC_BOOK3S_64
+extern void _save_tar(struct thread_struct *prev);
+#else
+static inline void _save_tar(struct thread_struct *prev) {}
+#endif
extern void giveup_fpu(struct task_struct *);
extern void load_up_fpu(void);
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 4674fe6..32e18f3 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -389,6 +389,18 @@ DSCR_DEFAULT:
.tc dscr_default[TC],dscr_default
.section ".text"
+#ifdef CONFIG_PPC_BOOK3S_64
+_GLOBAL(_save_tar)
+ /*
+ * Back up the TAR across context switches. Note that the TAR is not
+ * available for use in the kernel. (To provide this, the TAR should
+ * be backed up/restored on exception entry/exit instead, and be in
+ * pt_regs. FIXME, this should be in pt_regs anyway (for debug).)
+ */
+ mfspr r0,SPRN_TAR
+ std r0,THREAD_TAR(r3)
+ blr
+#endif
/*
* This routine switches between two different tasks. The process
--
1.8.1.2
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