[PATCH 7/8] powerpc/signal64: Rewrite handle_rt_signal64() to minimise uaccess switches

["Christopher M. Riedl" <cmr@codefail.de>]

From: Daniel Axtens <dja@axtens.net>

Add uaccess blocks and use the 'unsafe' versions of functions doing user
access where possible to reduce the number of times uaccess has to be
opened/closed.

There is no 'unsafe' version of copy_siginfo_to_user, so move it
slightly to allow for a "longer" uaccess block.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
---
 arch/powerpc/kernel/signal_64.c | 54 ++++++++++++++++-----------------
 1 file changed, 27 insertions(+), 27 deletions(-)

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 6d4f7a5c4fbf..3b97e3681a8f 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -843,46 +843,42 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 	/* Save the thread's msr before get_tm_stackpointer() changes it */
 	unsigned long msr = regs->msr;
 #endif
-
 	frame = get_sigframe(ksig, tsk, sizeof(*frame), 0);
-	if (!access_ok(frame, sizeof(*frame)))
+	if (!user_write_access_begin(frame, sizeof(*frame)))
 		goto badframe;
 
-	err |= __put_user(&frame->info, &frame->pinfo);
-	err |= __put_user(&frame->uc, &frame->puc);
-	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
-	if (err)
-		goto badframe;
+	unsafe_put_user(&frame->info, &frame->pinfo, badframe_block);
+	unsafe_put_user(&frame->uc, &frame->puc, badframe_block);
 
 	/* Create the ucontext.  */
-	err |= __put_user(0, &frame->uc.uc_flags);
-	err |= __save_altstack(&frame->uc.uc_stack, regs->gpr[1]);
+	unsafe_put_user(0, &frame->uc.uc_flags, badframe_block);
+	unsafe_save_altstack(&frame->uc.uc_stack, regs->gpr[1], badframe_block);
+
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	if (MSR_TM_ACTIVE(msr)) {
 		/* The ucontext_t passed to userland points to the second
 		 * ucontext_t (for transactional state) with its uc_link ptr.
 		 */
-		err |= __put_user(&frame->uc_transact, &frame->uc.uc_link);
+		unsafe_put_user(&frame->uc_transact, &frame->uc.uc_link, badframe_block);
+		user_write_access_end();
 		err |= setup_tm_sigcontexts(&frame->uc.uc_mcontext,
 					    &frame->uc_transact.uc_mcontext,
 					    tsk, ksig->sig, NULL,
 					    (unsigned long)ksig->ka.sa.sa_handler,
 					    msr);
+		if (!user_write_access_begin(frame, sizeof(struct rt_sigframe)))
+			goto badframe;
+
 	} else
 #endif
 	{
-		err |= __put_user(0, &frame->uc.uc_link);
-
-		if (!user_write_access_begin(frame, sizeof(struct rt_sigframe)))
-			return -EFAULT;
-		err |= __unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk,
-						ksig->sig, NULL,
-						(unsigned long)ksig->ka.sa.sa_handler, 1);
-		user_write_access_end();
+		unsafe_put_user(0, &frame->uc.uc_link, badframe_block);
+		unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig,
+					NULL, (unsigned long)ksig->ka.sa.sa_handler,
+					1, badframe_block);
 	}
-	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
-	if (err)
-		goto badframe;
+
+	unsafe_copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set), badframe_block);
 
 	/* Make sure signal handler doesn't get spurious FP exceptions */
 	tsk->thread.fp_state.fpscr = 0;
@@ -891,15 +887,17 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 	if (vdso64_rt_sigtramp && tsk->mm->context.vdso_base) {
 		regs->nip = tsk->mm->context.vdso_base + vdso64_rt_sigtramp;
 	} else {
-		if (!user_write_access_begin(frame, sizeof(struct rt_sigframe)))
-			return -EFAULT;
-		err |= __unsafe_setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
-		user_write_access_end();
-		if (err)
-			goto badframe;
+		unsafe_setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0],
+					badframe_block);
 		regs->nip = (unsigned long) &frame->tramp[0];
 	}
 
+	user_write_access_end();
+
+	/* Save the siginfo outside of the unsafe block. */
+	if (copy_siginfo_to_user(&frame->info, &ksig->info))
+		goto badframe;
+
 	/* Allocate a dummy caller frame for the signal handler. */
 	newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
 	err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
@@ -939,6 +937,8 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 
 	return 0;
 
+badframe_block:
+	user_write_access_end();
 badframe:
 	signal_fault(current, regs, "handle_rt_signal64", frame);
 
-- 
2.28.0