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Date:	Fri, 18 Jul 2014 10:04:54 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Ley Foon Tan <lftan@...era.com>
Cc:	Linux-Arch <linux-arch@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	LeyFoon Tan <lftan.linux@...il.com>, cltang@...esourcery.com
Subject: Re: [PATCH v2 16/29] nios2: Signal handling support

On Tue, Jul 15, 2014 at 10:45 AM, Ley Foon Tan <lftan@...era.com> wrote:
> This patch adds support for signal handling.
>
> Signed-off-by: Ley Foon Tan <lftan@...era.com>
> ---
>  arch/nios2/include/asm/signal.h          |  22 +++
>  arch/nios2/include/asm/ucontext.h        |  34 ++++
>  arch/nios2/include/uapi/asm/sigcontext.h |  30 +++
>  arch/nios2/include/uapi/asm/signal.h     |  23 +++
>  arch/nios2/kernel/signal.c               | 316 +++++++++++++++++++++++++++++++
>  5 files changed, 425 insertions(+)
>  create mode 100644 arch/nios2/include/asm/signal.h
>  create mode 100644 arch/nios2/include/asm/ucontext.h
>  create mode 100644 arch/nios2/include/uapi/asm/sigcontext.h
>  create mode 100644 arch/nios2/include/uapi/asm/signal.h
>  create mode 100644 arch/nios2/kernel/signal.c
>
> diff --git a/arch/nios2/include/asm/signal.h b/arch/nios2/include/asm/signal.h
> new file mode 100644
> index 0000000..bbcf11e
> --- /dev/null
> +++ b/arch/nios2/include/asm/signal.h
> @@ -0,0 +1,22 @@
> +/*
> + * 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 */
> diff --git a/arch/nios2/include/asm/ucontext.h b/arch/nios2/include/asm/ucontext.h
> new file mode 100644
> index 0000000..5870ef4
> --- /dev/null
> +++ b/arch/nios2/include/asm/ucontext.h
> @@ -0,0 +1,34 @@
> +/*
> + * Copyright (C) 2010 Tobias Klauser <tklauser@...tanz.ch>
> + * Copyright (C) 2004 Microtronix Datacom Ltd
> + *
> + * derived from m68knommu
> + *
> + * 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
> diff --git a/arch/nios2/include/uapi/asm/sigcontext.h b/arch/nios2/include/uapi/asm/sigcontext.h
> new file mode 100644
> index 0000000..6bfd880
> --- /dev/null
> +++ b/arch/nios2/include/uapi/asm/sigcontext.h
> @@ -0,0 +1,30 @@
> +/*
> + * Taken from the m68knommu.
> + *
> + * 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
> diff --git a/arch/nios2/include/uapi/asm/signal.h b/arch/nios2/include/uapi/asm/signal.h
> new file mode 100644
> index 0000000..f29ee63
> --- /dev/null
> +++ b/arch/nios2/include/uapi/asm/signal.h
> @@ -0,0 +1,23 @@
> +/*
> + * 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 */
> diff --git a/arch/nios2/kernel/signal.c b/arch/nios2/kernel/signal.c
> new file mode 100644
> index 0000000..3f649d8
> --- /dev/null
> +++ b/arch/nios2/kernel/signal.c
> @@ -0,0 +1,316 @@
> +/*
> + * Copyright (C) 2013 Altera Corporation
> + * Copyright (C) 2011-2012 Tobias Klauser <tklauser@...tanz.ch>
> + * Copyright (C) 2004 Microtronix Datacom Ltd
> + * Copyright (C) 1991, 1992 Linus Torvalds
> + *
> + * This file is based on kernel/signal.c from m68knommu.
> + *
> + * 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)))
> +
> +static int do_signal(struct pt_regs *regs, int in_syscall);

Do you really need this prototype?

> +/*
> + * 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;
> +
> +       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->estatus = (regs->estatus & 0xffffffff);
> +       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;
> +
> +       sigdelsetmask(&set, ~_BLOCKABLE);
> +       spin_lock_irq(&current->sighand->siglock);
> +       current->blocked = set;
> +       recalc_sigpending();
> +       spin_unlock_irq(&current->sighand->siglock);

Why aren't you using set_current_blocked() here?

> +       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 push_cache(unsigned long vaddr)
> +{
> +       flush_dcache_range(vaddr, vaddr + 12);
> +       flush_icache_range(vaddr, vaddr + 12);
> +}
> +
> +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));

You neither check nor propagate this error code.

> +       /* 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;
> +}
> +
> +static inline void handle_restart(struct pt_regs *regs, struct k_sigaction *ka,
> +                                 int has_handler)
> +{
> +       switch (regs->r2) {
> +       case ERESTART_RESTARTBLOCK:
> +       case ERESTARTNOHAND:
> +               regs->r2 = EINTR;
> +               regs->r7 = 1;
> +               break;
> +       case ERESTARTSYS:
> +               if (has_handler && !(ka->sa.sa_flags & SA_RESTART)) {
> +                       regs->r2 = EINTR;
> +                       regs->r7 = 1;
> +                       break;
> +               }
> +       /* fallthrough */
> +       case ERESTARTNOINTR:
> +               regs->r2 = regs->orig_r2;
> +               regs->r7 = regs->orig_r7;
> +               regs->ea -= 4;
> +               break;
> +       }
> +}
> +
> +/*
> + * 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, int in_syscall)
> +{
> +       struct ksignal ksig;
> +
> +       current->thread.kregs = regs;
> +
> +       if (get_signal(&ksig)) {
> +               /*
> +                * Are we from a system call? If so, check system call
> +                * restarting.
> +                */
> +               if (in_syscall)
> +                       handle_restart(regs, &ksig.ka, 1);
> +               /* Whee!  Actually deliver the signal.  */
> +               handle_signal(&ksig, regs);
> +               return 1;
> +       }
> +
> +       /*
> +        * No signal to deliver to the process - restart the syscall.
> +        */
> +       if (in_syscall) {
> +               /* Did the syscall return an error code */
> +               if (regs->r7 == 1) {
> +                       if (regs->r2 == ERESTARTNOHAND ||
> +                               regs->r2 == ERESTARTSYS ||
> +                               regs->r2 == ERESTARTNOINTR) {
> +                               regs->r2 = regs->orig_r2;
> +                               regs->r7 = regs->orig_r7;
> +                               regs->ea -= 4;
> +                       } else if (regs->r2 == ERESTART_RESTARTBLOCK) {
> +                               regs->r2 = __NR_restart_syscall;
> +                               regs->ea -= 4;
> +                       }
> +               }
> +       }
> +
> +       return 0;
> +}
> +
> +asmlinkage void do_notify_resume(struct pt_regs *regs, int in_syscall)
> +{
> +       /*
> +        * 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;
> +
> +       if (test_thread_flag(TIF_SIGPENDING))
> +               do_signal(regs, in_syscall);
> +
> +       if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
> +               tracehook_notify_resume(regs);
> +}
> --
> 1.8.2.1
>
> --
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-- 
Thanks,
//richard
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