[ 005/103] powerpc/tm: Fix writing top half of MSR on 32 bit signals

[Greg Kroah-Hartman]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Neuling <mikey@xxxxxxxxxxx>

commit 1d25f11fdbcc5390d68efd98c28900bfd29b264c upstream.

The MSR TM controls are in the top 32 bits of the MSR hence on 32 bit signals,
we stick the top half of the MSR in the checkpointed signal context so that the
user can access it.

Unfortunately, we don't currently write anything to the checkpointed signal
context when coming in a from a non transactional process and hence the top MSR
bits can contain junk.

This updates the 32 bit signal handling code to always write something to the
top MSR bits so that users know if the process is transactional or not and the
kernel can use it on signal return.

Signed-off-by: Michael Neuling <mikey@xxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/powerpc/kernel/signal_32.c |   29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -407,7 +407,8 @@ inline unsigned long copy_transact_fpr_f
  * altivec/spe instructions at some point.
  */
 static int save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
-		int sigret, int ctx_has_vsx_region)
+			  struct mcontext __user *tm_frame, int sigret,
+			  int ctx_has_vsx_region)
 {
 	unsigned long msr = regs->msr;
 
@@ -475,6 +476,12 @@ static int save_user_regs(struct pt_regs
 
 	if (__put_user(msr, &frame->mc_gregs[PT_MSR]))
 		return 1;
+	/* We need to write 0 the MSR top 32 bits in the tm frame so that we
+	 * can check it on the restore to see if TM is active
+	 */
+	if (tm_frame && __put_user(0, &tm_frame->mc_gregs[PT_MSR]))
+		return 1;
+
 	if (sigret) {
 		/* Set up the sigreturn trampoline: li r0,sigret; sc */
 		if (__put_user(0x38000000UL + sigret, &frame->tramp[0])
@@ -952,6 +959,7 @@ int handle_rt_signal32(unsigned long sig
 {
 	struct rt_sigframe __user *rt_sf;
 	struct mcontext __user *frame;
+	struct mcontext __user *tm_frame = NULL;
 	void __user *addr;
 	unsigned long newsp = 0;
 	int sigret;
@@ -985,23 +993,24 @@ int handle_rt_signal32(unsigned long sig
 	}
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+	tm_frame = &rt_sf->uc_transact.uc_mcontext;
 	if (MSR_TM_ACTIVE(regs->msr)) {
-		if (save_tm_user_regs(regs, &rt_sf->uc.uc_mcontext,
-				      &rt_sf->uc_transact.uc_mcontext, sigret))
+		if (save_tm_user_regs(regs, frame, tm_frame, sigret))
 			goto badframe;
 	}
 	else
 #endif
-		if (save_user_regs(regs, frame, sigret, 1))
+	{
+		if (save_user_regs(regs, frame, tm_frame, sigret, 1))
 			goto badframe;
+	}
 	regs->link = tramp;
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	if (MSR_TM_ACTIVE(regs->msr)) {
 		if (__put_user((unsigned long)&rt_sf->uc_transact,
 			       &rt_sf->uc.uc_link)
-		    || __put_user(to_user_ptr(&rt_sf->uc_transact.uc_mcontext),
-				  &rt_sf->uc_transact.uc_regs))
+		    || __put_user((unsigned long)tm_frame, &rt_sf->uc_transact.uc_regs))
 			goto badframe;
 	}
 	else
@@ -1170,7 +1179,7 @@ long sys_swapcontext(struct ucontext __u
 		mctx = (struct mcontext __user *)
 			((unsigned long) &old_ctx->uc_mcontext & ~0xfUL);
 		if (!access_ok(VERIFY_WRITE, old_ctx, ctx_size)
-		    || save_user_regs(regs, mctx, 0, ctx_has_vsx_region)
+		    || save_user_regs(regs, mctx, NULL, 0, ctx_has_vsx_region)
 		    || put_sigset_t(&old_ctx->uc_sigmask, &current->blocked)
 		    || __put_user(to_user_ptr(mctx), &old_ctx->uc_regs))
 			return -EFAULT;
@@ -1392,6 +1401,7 @@ int handle_signal32(unsigned long sig, s
 {
 	struct sigcontext __user *sc;
 	struct sigframe __user *frame;
+	struct mcontext __user *tm_mctx = NULL;
 	unsigned long newsp = 0;
 	int sigret;
 	unsigned long tramp;
@@ -1425,6 +1435,7 @@ int handle_signal32(unsigned long sig, s
 	}
 
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+	tm_mctx = &frame->mctx_transact;
 	if (MSR_TM_ACTIVE(regs->msr)) {
 		if (save_tm_user_regs(regs, &frame->mctx, &frame->mctx_transact,
 				      sigret))
@@ -1432,8 +1443,10 @@ int handle_signal32(unsigned long sig, s
 	}
 	else
 #endif
-		if (save_user_regs(regs, &frame->mctx, sigret, 1))
+	{
+		if (save_user_regs(regs, &frame->mctx, tm_mctx, sigret, 1))
 			goto badframe;
+	}
 
 	regs->link = tramp;
 


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