nios2: Signal handling support

This patch adds support for signal handling.
Signed-off-by: Ley Foon Tan <lftan@altera.com>

arch/nios2/include/asm/signal.h

+/*
+ * Copyright Altera Corporation (C) 2013. All rights reserved
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+#ifndef _NIOS2_SIGNAL_H
+#define _NIOS2_SIGNAL_H
+
+#include <uapi/asm/signal.h>
+
+#endif	/* _NIOS2_SIGNAL_H */

arch/nios2/include/asm/ucontext.h

+/*
+ * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2004 Microtronix Datacom Ltd
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef _ASM_NIOS2_UCONTEXT_H
+#define _ASM_NIOS2_UCONTEXT_H
+
+typedef int greg_t;
+#define NGREG 32
+typedef greg_t gregset_t[NGREG];
+
+struct mcontext {
+	int version;
+	gregset_t gregs;
+};
+
+#define MCONTEXT_VERSION 2
+
+struct ucontext {
+	unsigned long	  uc_flags;
+	struct ucontext  *uc_link;
+	stack_t		  uc_stack;
+	struct mcontext	  uc_mcontext;
+	sigset_t	  uc_sigmask;	/* mask last for extensibility */
+};
+
+#endif

arch/nios2/include/uapi/asm/sigcontext.h

+/*
+ * Copyright (C) 2004, Microtronix Datacom Ltd.
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ */
+
+#ifndef _ASM_NIOS2_SIGCONTEXT_H
+#define _ASM_NIOS2_SIGCONTEXT_H
+
+#include <asm/ptrace.h>
+
+struct sigcontext {
+	struct pt_regs regs;
+	unsigned long  sc_mask;	/* old sigmask */
+};
+
+#endif

arch/nios2/include/uapi/asm/signal.h

+/*
+ * Copyright Altera Corporation (C) 2013. All rights reserved
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+#ifndef _ASM_NIOS2_SIGNAL_H
+#define _ASM_NIOS2_SIGNAL_H
+
+#define SA_RESTORER 0x04000000
+#include <asm-generic/signal.h>
+
+#endif /* _ASM_NIOS2_SIGNAL_H */

arch/nios2/kernel/signal.c

+/*
+ * Copyright (C) 2013-2014 Altera Corporation
+ * Copyright (C) 2011-2012 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2004 Microtronix Datacom Ltd
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/signal.h>
+#include <linux/errno.h>
+#include <linux/ptrace.h>
+#include <linux/uaccess.h>
+#include <linux/unistd.h>
+#include <linux/personality.h>
+#include <linux/tracehook.h>
+
+#include <asm/ucontext.h>
+#include <asm/cacheflush.h>
+
+#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
+
+/*
+ * Do a signal return; undo the signal stack.
+ *
+ * Keep the return code on the stack quadword aligned!
+ * That makes the cache flush below easier.
+ */
+
+struct rt_sigframe {
+	struct siginfo info;
+	struct ucontext uc;
+};
+
+static inline int rt_restore_ucontext(struct pt_regs *regs,
+					struct switch_stack *sw,
+					struct ucontext *uc, int *pr2)
+{
+	int temp;
+	greg_t *gregs = uc->uc_mcontext.gregs;
+	int err;
+
+	/* Always make any pending restarted system calls return -EINTR */
+	current_thread_info()->restart_block.fn = do_no_restart_syscall;
+
+	err = __get_user(temp, &uc->uc_mcontext.version);
+	if (temp != MCONTEXT_VERSION)
+		goto badframe;
+	/* restore passed registers */
+	err |= __get_user(regs->r1, &gregs[0]);
+	err |= __get_user(regs->r2, &gregs[1]);
+	err |= __get_user(regs->r3, &gregs[2]);
+	err |= __get_user(regs->r4, &gregs[3]);
+	err |= __get_user(regs->r5, &gregs[4]);
+	err |= __get_user(regs->r6, &gregs[5]);
+	err |= __get_user(regs->r7, &gregs[6]);
+	err |= __get_user(regs->r8, &gregs[7]);
+	err |= __get_user(regs->r9, &gregs[8]);
+	err |= __get_user(regs->r10, &gregs[9]);
+	err |= __get_user(regs->r11, &gregs[10]);
+	err |= __get_user(regs->r12, &gregs[11]);
+	err |= __get_user(regs->r13, &gregs[12]);
+	err |= __get_user(regs->r14, &gregs[13]);
+	err |= __get_user(regs->r15, &gregs[14]);
+	err |= __get_user(sw->r16, &gregs[15]);
+	err |= __get_user(sw->r17, &gregs[16]);
+	err |= __get_user(sw->r18, &gregs[17]);
+	err |= __get_user(sw->r19, &gregs[18]);
+	err |= __get_user(sw->r20, &gregs[19]);
+	err |= __get_user(sw->r21, &gregs[20]);
+	err |= __get_user(sw->r22, &gregs[21]);
+	err |= __get_user(sw->r23, &gregs[22]);
+	/* gregs[23] is handled below */
+	err |= __get_user(sw->fp, &gregs[24]);  /* Verify, should this be
+							settable */
+	err |= __get_user(sw->gp, &gregs[25]);  /* Verify, should this be
+							settable */
+
+	err |= __get_user(temp, &gregs[26]);  /* Not really necessary no user
+							settable bits */
+	err |= __get_user(regs->ea, &gregs[27]);
+
+	err |= __get_user(regs->ra, &gregs[23]);
+	err |= __get_user(regs->sp, &gregs[28]);
+
+	regs->orig_r2 = -1;		/* disable syscall checks */
+
+	err |= restore_altstack(&uc->uc_stack);
+	if (err)
+		goto badframe;
+
+	*pr2 = regs->r2;
+	return err;
+
+badframe:
+	return 1;
+}
+
+asmlinkage int do_rt_sigreturn(struct switch_stack *sw)
+{
+	struct pt_regs *regs = (struct pt_regs *)(sw + 1);
+	/* Verify, can we follow the stack back */
+	struct rt_sigframe *frame = (struct rt_sigframe *) regs->sp;
+	sigset_t set;
+	int rval;
+
+	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
+		goto badframe;
+
+	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
+		goto badframe;
+
+	set_current_blocked(&set);
+
+	if (rt_restore_ucontext(regs, sw, &frame->uc, &rval))
+		goto badframe;
+
+	return rval;
+
+badframe:
+	force_sig(SIGSEGV, current);
+	return 0;
+}
+
+static inline int rt_setup_ucontext(struct ucontext *uc, struct pt_regs *regs)
+{
+	struct switch_stack *sw = (struct switch_stack *)regs - 1;
+	greg_t *gregs = uc->uc_mcontext.gregs;
+	int err = 0;
+
+	err |= __put_user(MCONTEXT_VERSION, &uc->uc_mcontext.version);
+	err |= __put_user(regs->r1, &gregs[0]);
+	err |= __put_user(regs->r2, &gregs[1]);
+	err |= __put_user(regs->r3, &gregs[2]);
+	err |= __put_user(regs->r4, &gregs[3]);
+	err |= __put_user(regs->r5, &gregs[4]);
+	err |= __put_user(regs->r6, &gregs[5]);
+	err |= __put_user(regs->r7, &gregs[6]);
+	err |= __put_user(regs->r8, &gregs[7]);
+	err |= __put_user(regs->r9, &gregs[8]);
+	err |= __put_user(regs->r10, &gregs[9]);
+	err |= __put_user(regs->r11, &gregs[10]);
+	err |= __put_user(regs->r12, &gregs[11]);
+	err |= __put_user(regs->r13, &gregs[12]);
+	err |= __put_user(regs->r14, &gregs[13]);
+	err |= __put_user(regs->r15, &gregs[14]);
+	err |= __put_user(sw->r16, &gregs[15]);
+	err |= __put_user(sw->r17, &gregs[16]);
+	err |= __put_user(sw->r18, &gregs[17]);
+	err |= __put_user(sw->r19, &gregs[18]);
+	err |= __put_user(sw->r20, &gregs[19]);
+	err |= __put_user(sw->r21, &gregs[20]);
+	err |= __put_user(sw->r22, &gregs[21]);
+	err |= __put_user(sw->r23, &gregs[22]);
+	err |= __put_user(regs->ra, &gregs[23]);
+	err |= __put_user(sw->fp, &gregs[24]);
+	err |= __put_user(sw->gp, &gregs[25]);
+	err |= __put_user(regs->ea, &gregs[27]);
+	err |= __put_user(regs->sp, &gregs[28]);
+	return err;
+}
+
+static inline void *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
+				 size_t frame_size)
+{
+	unsigned long usp;
+
+	/* Default to using normal stack.  */
+	usp = regs->sp;
+
+	/* This is the X/Open sanctioned signal stack switching.  */
+	usp = sigsp(usp, ksig);
+
+	/* Verify, is it 32 or 64 bit aligned */
+	return (void *)((usp - frame_size) & -8UL);
+}
+
+static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
+			  struct pt_regs *regs)
+{
+	struct rt_sigframe *frame;
+	int err = 0;
+
+	frame = get_sigframe(ksig, regs, sizeof(*frame));
+
+	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
+		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
+
+	/* Create the ucontext.  */
+	err |= __put_user(0, &frame->uc.uc_flags);
+	err |= __put_user(0, &frame->uc.uc_link);
+	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
+	err |= rt_setup_ucontext(&frame->uc, regs);
+	err |= copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
+
+	if (err)
+		goto give_sigsegv;
+
+	/* Set up to return from userspace; jump to fixed address sigreturn
+	   trampoline on kuser page.  */
+	regs->ra = (unsigned long) (0x1040);
+
+	/* Set up registers for signal handler */
+	regs->sp = (unsigned long) frame;
+	regs->r4 = (unsigned long) ksig->sig;
+	regs->r5 = (unsigned long) &frame->info;
+	regs->r6 = (unsigned long) &frame->uc;
+	regs->ea = (unsigned long) ksig->ka.sa.sa_handler;
+	return 0;
+
+give_sigsegv:
+	force_sigsegv(ksig->sig, current);
+	return -EFAULT;
+}
+
+/*
+ * OK, we're invoking a handler
+ */
+static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
+{
+	int ret;
+	sigset_t *oldset = sigmask_to_save();
+
+	/* set up the stack frame */
+	ret = setup_rt_frame(ksig, oldset, regs);
+
+	signal_setup_done(ret, ksig, 0);
+}
+
+static int do_signal(struct pt_regs *regs)
+{
+	unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
+	int restart = 0;
+	struct ksignal ksig;
+
+	current->thread.kregs = regs;
+
+	/*
+	 * If we were from a system call, check for system call restarting...
+	 */
+	if (regs->orig_r2 >= 0) {
+		continue_addr = regs->ea;
+		restart_addr = continue_addr - 4;
+		retval = regs->r2;
+
+		/*
+		 * Prepare for system call restart. We do this here so that a
+		 * debugger will see the already changed PC.
+		 */
+		switch (retval) {
+		case ERESTART_RESTARTBLOCK:
+			restart = -2;
+		case ERESTARTNOHAND:
+		case ERESTARTSYS:
+		case ERESTARTNOINTR:
+			restart++;
+			regs->r2 = regs->orig_r2;
+			regs->r7 = regs->orig_r7;
+			regs->ea = restart_addr;
+			break;
+		}
+	}
+
+	if (get_signal(&ksig)) {
+		/* handler */
+		if (unlikely(restart && regs->ea == restart_addr)) {
+			if (retval == ERESTARTNOHAND ||
+			    retval == ERESTART_RESTARTBLOCK ||
+			     (retval == ERESTARTSYS
+				&& !(ksig.ka.sa.sa_flags & SA_RESTART))) {
+				regs->r2 = EINTR;
+				regs->r7 = 1;
+				regs->ea = continue_addr;
+			}
+		}
+		handle_signal(&ksig, regs);
+		return 0;
+	}
+
+	/*
+	 * No handler present
+	 */
+	if (unlikely(restart) && regs->ea == restart_addr) {
+		regs->ea = continue_addr;
+		regs->r2 = __NR_restart_syscall;
+	}
+
+	/*
+	* If there's no signal to deliver, we just put the saved sigmask back.
+	*/
+	restore_saved_sigmask();
+
+	return restart;
+}
+
+asmlinkage int do_notify_resume(struct pt_regs *regs)
+{
+	/*
+	 * We want the common case to go fast, which is why we may in certain
+	 * cases get here from kernel mode. Just return without doing anything
+	 * if so.
+	 */
+	if (!user_mode(regs))
+		return 0;
+
+	if (test_thread_flag(TIF_SIGPENDING)) {
+		int restart = do_signal(regs);
+
+		if (unlikely(restart)) {
+			/*
+			 * Restart without handlers.
+			 * Deal with it without leaving
+			 * the kernel space.
+			 */
+			return restart;
+		}
+	} else if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
+		tracehook_notify_resume(regs);
+
+	return 0;
+}