[PATCH v11 02/27] powerpc/process: Add the function flush_tmregs_to_thread

[wei.guo.simon at gmail.com]

From: Anshuman Khandual <khandual at linux.vnet.ibm.com>

This patch creates a function flush_tmregs_to_thread which
will then be used by subsequent patches in this series. The
function checks for self tracing ptrace interface attempts
while in the TM context and logs appropriate warning message.

Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Shuah Khan <shuahkh at osg.samsung.com>
Cc: Anton Blanchard <anton at samba.org>
Cc: Cyril Bur <cyrilbur at gmail.com>
Cc: Anshuman Khandual <khandual at linux.vnet.ibm.com>
Cc: Simon Guo <wei.guo.simon at gmail.com>
Cc: Ulrich Weigand <ulrich.weigand at de.ibm.com>
Cc: Michael Neuling <mikey at neuling.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Kees Cook <keescook at chromium.org>
Cc: Rashmica Gupta <rashmicy at gmail.com>
Cc: Khem Raj <raj.khem at gmail.com>
Cc: Jessica Yu <jeyu at redhat.com>
Cc: Jiri Kosina <jkosina at suse.cz>
Cc: Miroslav Benes <mbenes at suse.cz>
Cc: Suraj Jitindar Singh <sjitindarsingh at gmail.com>
Cc: Chris Smart <chris at distroguy.com>
Cc: linuxppc-dev at lists.ozlabs.org
Cc: linux-kernel at vger.kernel.org
Cc: linux-kselftest at vger.kernel.org
Signed-off-by: Anshuman Khandual <khandual at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/switch_to.h |  8 ++++++++
 arch/powerpc/kernel/process.c        | 20 ++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 17c8380..0a74ebe 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -75,6 +75,14 @@ static inline void disable_kernel_spe(void)
 static inline void __giveup_spe(struct task_struct *t) { }
 #endif
 
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+extern void flush_tmregs_to_thread(struct task_struct *);
+#else
+static inline void flush_tmregs_to_thread(struct task_struct *t)
+{
+}
+#endif
+
 static inline void clear_task_ebb(struct task_struct *t)
 {
 #ifdef CONFIG_PPC_BOOK3S_64
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 852f257..36d44ec 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1027,6 +1027,26 @@ static inline void restore_sprs(struct thread_struct *old_thread,
 #endif
 }
 
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+void flush_tmregs_to_thread(struct task_struct *tsk)
+{
+	/*
+	 * Process self tracing is not yet supported through
+	 * ptrace interface. Ptrace generic code should have
+	 * prevented this from happening in the first place.
+	 * Warn once here with the message, if some how it
+	 * is attempted.
+	 */
+	WARN_ONCE(tsk == current,
+		"Not expecting ptrace on self: TM regs may be incorrect\n");
+
+	/*
+	 * If task is not current, it should have been flushed
+	 * already to it's thread_struct during __switch_to().
+	 */
+}
+#endif
+
 struct task_struct *__switch_to(struct task_struct *prev,
 	struct task_struct *new)
 {
-- 
1.8.3.1