[ARM] Rehash iwmmxt signal handling.

In the near future, VFP will want to save state onto the user stack.
Therefore, separate out the iwmmxt specific parts, and implement
a generic "safe copy to user space using random CPU instructions".
This is necessary because iwmmxt and VFP both use special CPU
instructions to load and/or save their state.

arch/arm/kernel/signal.c

@@ -126,25 +126,6 @@ sys_sigaction(int sig, const struct old_sigaction __user *act,
 	return ret;
 }
 
-/*
- * Do a signal return; undo the signal stack.
- */
-struct sigframe
-{
-	struct sigcontext sc;
-	unsigned long extramask[_NSIG_WORDS-1];
-	unsigned long retcode;
-};
-
-struct rt_sigframe
-{
-	struct siginfo __user *pinfo;
-	void __user *puc;
-	struct siginfo info;
-	struct ucontext uc;
-	unsigned long retcode;
-};
-
 #ifdef CONFIG_IWMMXT
 
 /* iwmmxt_area is 0x98 bytes long, preceeded by 8 bytes of signature */
@@ -152,8 +133,15 @@ struct rt_sigframe
 #define IWMMXT_MAGIC0		0x12ef842a
 #define IWMMXT_MAGIC1		0x1c07ca71
 
-static int page_present(struct mm_struct *mm, unsigned long addr, int wr)
+struct iwmmxt_sigframe {
+	unsigned long	magic0;
+	unsigned long	magic1;
+	unsigned long	storage[0x98/4];
+};
+
+static int page_present(struct mm_struct *mm, void __user *uptr, int wr)
 {
+	unsigned long addr = (unsigned long)uptr;
 	pgd_t *pgd = pgd_offset(mm, addr);
 	if (pgd_present(*pgd)) {
 		pmd_t *pmd = pmd_offset(pgd, addr);
@@ -165,49 +153,66 @@ static int page_present(struct mm_struct *mm, unsigned long addr, int wr)
 	return 0;
 }
 
-static int
-preserve_iwmmxt_context(void *iwmmxt_save_area)
+static int copy_locked(void __user *uptr, void *kptr, size_t size, int write,
+		       void (*copyfn)(void *, void __user *))
+{
+	unsigned char v, __user *userptr = uptr;
+	int err = 0;
+
+	do {
+		struct mm_struct *mm;
+
+		if (write) {
+			__put_user_error(0, userptr, err);
+			__put_user_error(0, userptr + size - 1, err);
+		} else {
+			__get_user_error(v, userptr, err);
+			__get_user_error(v, userptr + size - 1, err);
+		}
+
+		if (err)
+			break;
+
+		mm = current->mm;
+		spin_lock(&mm->page_table_lock);
+		if (page_present(mm, userptr, write) &&
+		    page_present(mm, userptr + size - 1, write)) {
+		    	copyfn(kptr, uptr);
+		} else
+			err = 1;
+		spin_unlock(&mm->page_table_lock);
+	} while (err);
+
+	return err;
+}
+
+static int preserve_iwmmxt_context(struct iwmmxt_sigframe *frame)
 {
 	int err = 0;
 
 	/* the iWMMXt context must be 64 bit aligned */
-	long *iwmmxt_storage = (long *)(((long)iwmmxt_save_area + 4) & ~7);
+	WARN_ON((unsigned long)frame & 7);
+
+	__put_user_error(IWMMXT_MAGIC0, &frame->magic0, err);
+	__put_user_error(IWMMXT_MAGIC1, &frame->magic1, err);
 
-again:
-	__put_user_error(IWMMXT_MAGIC0, iwmmxt_storage+0, err);
-	__put_user_error(IWMMXT_MAGIC1, iwmmxt_storage+1, err);
 	/*
 	 * iwmmxt_task_copy() doesn't check user permissions.
 	 * Let's do a dummy write on the upper boundary to ensure
 	 * access to user mem is OK all way up.
 	 */
-	__put_user_error(0, iwmmxt_storage+IWMMXT_STORAGE_SIZE/4-1, err);
-	if (!err) {
-		/* Let's make sure the user mapping won't disappear under us */
-		struct mm_struct *mm = current->mm;
-		unsigned long addr = (unsigned long)iwmmxt_storage;
-		spin_lock(&mm->page_table_lock);
-		if ( !page_present(mm, addr, 1) ||
-		     !page_present(mm, addr+IWMMXT_STORAGE_SIZE-1, 1) ) {
-			/* our user area has gone before grabbing the lock */
-			spin_unlock(&mm->page_table_lock);
-			goto again;
-		}
-		iwmmxt_task_copy(current_thread_info(), iwmmxt_storage+2);
-		spin_unlock(&mm->page_table_lock);
-		return 0;
-	}
+	err |= copy_locked(&frame->storage, current_thread_info(),
+			   sizeof(frame->storage), 1, iwmmxt_task_copy);
 	return err;
 }
 
-static int
-restore_iwmmxt_context(void *iwmmxt_save_area)
+static int restore_iwmmxt_context(struct iwmmxt_sigframe *frame)
 {
+	unsigned long magic0, magic1;
 	int err = 0;
-	long *iwmmxt_storage, magic0, magic1, dummy;
 
 	/* the iWMMXt context is 64 bit aligned */
-	iwmmxt_storage = (long *)(((long)iwmmxt_save_area + 4) & ~7);
+	WARN_ON((unsigned long)frame & 7);
 
 	/*
 	 * Validate iWMMXt context signature.
@@ -215,32 +220,51 @@ restore_iwmmxt_context(void *iwmmxt_save_area)
 	 * Let's do a dummy write on the upper boundary to ensure
 	 * access to user mem is OK all way up.
 	 */
-again:
-	__get_user_error(magic0, iwmmxt_storage+0, err);
-	__get_user_error(magic1, iwmmxt_storage+1, err);
-	if (!err && magic0 == IWMMXT_MAGIC0 && magic1 == IWMMXT_MAGIC1 &&
-	    !__get_user(dummy, iwmmxt_storage+IWMMXT_STORAGE_SIZE/4-1)) {
-		/* Let's make sure the user mapping won't disappear under us */
-		struct mm_struct *mm = current->mm;
-		unsigned long addr = (unsigned long)iwmmxt_storage;
-		spin_lock(&mm->page_table_lock);
-		if ( !page_present(mm, addr, 0) ||
-		     !page_present(mm, addr+IWMMXT_STORAGE_SIZE-1, 0) ) {
-			/* our user area has gone before grabbing the lock */
-			spin_unlock(&mm->page_table_lock);
-			goto again;
-		}
-		iwmmxt_task_restore(current_thread_info(), iwmmxt_storage+2);
-		spin_unlock(&mm->page_table_lock);
-		return 0;
-	}
-	return -1;
+	__get_user_error(magic0, &frame->magic0, err);
+	__get_user_error(magic1, &frame->magic1, err);
+	if (!err && magic0 == IWMMXT_MAGIC0 && magic1 == IWMMXT_MAGIC1)
+		err = copy_locked(&frame->storage, current_thread_info(),
+				  sizeof(frame->storage), 0, iwmmxt_task_restore);
+	return err;
 }
 
 #endif
 
+/*
+ * Auxiliary signal frame.  This saves stuff like FP state.
+ * The layout of this structure is not part of the user ABI.
+ */
+struct aux_sigframe {
+#ifdef CONFIG_IWMMXT
+	struct iwmmxt_sigframe	iwmmxt;
+#endif
+#ifdef CONFIG_VFP
+	union vfp_state		vfp;
+#endif
+};
+
+/*
+ * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
+ */
+struct sigframe {
+	struct sigcontext sc;
+	unsigned long extramask[_NSIG_WORDS-1];
+	unsigned long retcode;
+	struct aux_sigframe aux __attribute__((aligned(8)));
+};
+
+struct rt_sigframe {
+	struct siginfo __user *pinfo;
+	void __user *puc;
+	struct siginfo info;
+	struct ucontext uc;
+	unsigned long retcode;
+	struct aux_sigframe aux __attribute__((aligned(8)));
+};
+
 static int
-restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
+restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
+		   struct aux_sigframe __user *aux)
 {
 	int err = 0;
 
@@ -264,6 +288,15 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 
 	err |= !valid_user_regs(regs);
 
+#ifdef CONFIG_IWMMXT
+	if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
+		err |= restore_iwmmxt_context(&aux->iwmmxt);
+#endif
+#ifdef CONFIG_VFP
+//	if (err == 0)
+//		err |= vfp_restore_state(&aux->vfp);
+#endif
+
 	return err;
 }
 
@@ -299,13 +332,8 @@ asmlinkage int sys_sigreturn(struct pt_regs *regs)
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext(regs, &frame->sc))
-		goto badframe;
-
-#ifdef CONFIG_IWMMXT
-	if (test_thread_flag(TIF_USING_IWMMXT) && restore_iwmmxt_context(frame+1))
+	if (restore_sigcontext(regs, &frame->sc, &frame->aux))
 		goto badframe;
-#endif
 
 	/* Send SIGTRAP if we're single-stepping */
 	if (current->ptrace & PT_SINGLESTEP) {
@@ -349,17 +377,12 @@ asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 
-	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
+	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &frame->aux))
 		goto badframe;
 
 	if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->ARM_sp) == -EFAULT)
 		goto badframe;
 
-#ifdef CONFIG_IWMMXT
-	if (test_thread_flag(TIF_USING_IWMMXT) && restore_iwmmxt_context(frame+1))
-		goto badframe;
-#endif
-
 	/* Send SIGTRAP if we're single-stepping */
 	if (current->ptrace & PT_SINGLESTEP) {
 		ptrace_cancel_bpt(current);
@@ -374,7 +397,7 @@ asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
 }
 
 static int
-setup_sigcontext(struct sigcontext __user *sc, /*struct _fpstate *fpstate,*/
+setup_sigcontext(struct sigcontext __user *sc, struct aux_sigframe __user *aux,
 		 struct pt_regs *regs, unsigned long mask)
 {
 	int err = 0;
@@ -402,6 +425,15 @@ setup_sigcontext(struct sigcontext __user *sc, /*struct _fpstate *fpstate,*/
 	__put_user_error(current->thread.address, &sc->fault_address, err);
 	__put_user_error(mask, &sc->oldmask, err);
 
+#ifdef CONFIG_IWMMXT
+	if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
+		err |= preserve_iwmmxt_context(&aux->iwmmxt);
+#endif
+#ifdef CONFIG_VFP
+//	if (err == 0)
+//		err |= vfp_save_state(&aux->vfp);
+#endif
+
 	return err;
 }
 
@@ -411,11 +443,6 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, int framesize)
 	unsigned long sp = regs->ARM_sp;
 	void __user *frame;
 
-#ifdef CONFIG_IWMMXT
-	if (test_thread_flag(TIF_USING_IWMMXT))
-		framesize = (framesize + 4 + IWMMXT_STORAGE_SIZE) & ~7;
-#endif
-
 	/*
 	 * This is the X/Open sanctioned signal stack switching.
 	 */
@@ -505,18 +532,13 @@ setup_frame(int usig, struct k_sigaction *ka, sigset_t *set, struct pt_regs *reg
 	if (!frame)
 		return 1;
 
-	err |= setup_sigcontext(&frame->sc, /*&frame->fpstate,*/ regs, set->sig[0]);
+	err |= setup_sigcontext(&frame->sc, &frame->aux, regs, set->sig[0]);
 
 	if (_NSIG_WORDS > 1) {
 		err |= __copy_to_user(frame->extramask, &set->sig[1],
 				      sizeof(frame->extramask));
 	}
 
-#ifdef CONFIG_IWMMXT
-	if (test_thread_flag(TIF_USING_IWMMXT))
-		err |= preserve_iwmmxt_context(frame+1);
-#endif
-
 	if (err == 0)
 		err = setup_return(regs, ka, &frame->retcode, frame, usig);
 
@@ -547,15 +569,10 @@ setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
 	stack.ss_size = current->sas_ss_size;
 	err |= __copy_to_user(&frame->uc.uc_stack, &stack, sizeof(stack));
 
-	err |= setup_sigcontext(&frame->uc.uc_mcontext, /*&frame->fpstate,*/
+	err |= setup_sigcontext(&frame->uc.uc_mcontext, &frame->aux,
 				regs, set->sig[0]);
 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 
-#ifdef CONFIG_IWMMXT
-	if (test_thread_flag(TIF_USING_IWMMXT))
-		err |= preserve_iwmmxt_context(frame+1);
-#endif
-
 	if (err == 0)
 		err = setup_return(regs, ka, &frame->retcode, frame, usig);