/*
 * Copyright (C) 1991, 1992  Linus Torvalds
 * Copyright 2010 Tilera Corporation. 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, version 2.
 *
 *   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.
 */

#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/suspend.h>
#include <linux/ptrace.h>
#include <linux/elf.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/sigframe.h>
#include <asm/syscalls.h>
#include <asm/vdso.h>
#include <arch/interrupts.h>

#define DEBUG_SIG 0

/*
 * Do a signal return; undo the signal stack.
 */

int restore_sigcontext(struct pt_regs *regs,
                       struct sigcontext __user *sc)
{
        int err;

        /* Always make any pending restarted system calls return -EINTR */
        current->restart_block.fn = do_no_restart_syscall;

        /*
         * Enforce that sigcontext is like pt_regs, and doesn't mess
         * up our stack alignment rules.
         */
        BUILD_BUG_ON(sizeof(struct sigcontext) != sizeof(struct pt_regs));
        BUILD_BUG_ON(sizeof(struct sigcontext) % 8 != 0);
        err = __copy_from_user(regs, sc, sizeof(*regs));

        /* Ensure that the PL is always set to USER_PL. */
        regs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(regs->ex1));

        regs->faultnum = INT_SWINT_1_SIGRETURN;

        return err;
}

void signal_fault(const char *type, struct pt_regs *regs,
                  void __user *frame, int sig)
{
        trace_unhandled_signal(type, regs, (unsigned long)frame, SIGSEGV);
        force_sigsegv(sig, current);
}

/* The assembly shim for this function arranges to ignore the return value. */
SYSCALL_DEFINE0(rt_sigreturn)
{
        struct pt_regs *regs = current_pt_regs();
        struct rt_sigframe __user *frame =
                (struct rt_sigframe __user *)(regs->sp);
        sigset_t set;

        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 (restore_sigcontext(regs, &frame->uc.uc_mcontext))
                goto badframe;

        if (restore_altstack(&frame->uc.uc_stack))
                goto badframe;

        return 0;

badframe:
        signal_fault("bad sigreturn frame", regs, frame, 0);
        return 0;
}

/*
 * Set up a signal frame.
 */

int setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
{
        return  __copy_to_user(sc, regs, sizeof(*regs));
}

/*
 * Determine which stack to use..
 */
static inline void __user *get_sigframe(struct k_sigaction *ka,
                                        struct pt_regs *regs,
                                        size_t frame_size)
{
        unsigned long sp;

        /* Default to using normal stack */
        sp = regs->sp;

        /*
         * If we are on the alternate signal stack and would overflow
         * it, don't.  Return an always-bogus address instead so we
         * will die with SIGSEGV.
         */
        if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
                return (void __user __force *)-1UL;

        /* This is the X/Open sanctioned signal stack switching.  */
        if (ka->sa.sa_flags & SA_ONSTACK) {
                if (sas_ss_flags(sp) == 0)
                        sp = current->sas_ss_sp + current->sas_ss_size;
        }

        sp -= frame_size;
        /*
         * Align the stack pointer according to the TILE ABI,
         * i.e. so that on function entry (sp & 15) == 0.
         */
        sp &= -16UL;
        return (void __user *) sp;
}

static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
                          struct pt_regs *regs)
{
        unsigned long restorer;
        struct rt_sigframe __user *frame;
        int err = 0, sig = ksig->sig;

        frame = get_sigframe(&ksig->ka, regs, sizeof(*frame));

        if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
                goto err;

        /* Always write at least the signal number for the stack backtracer. */
        if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
                /* At sigreturn time, restore the callee-save registers too. */
                err |= copy_siginfo_to_user(&frame->info, &ksig->info);
                regs->flags |= PT_FLAGS_RESTORE_REGS;
        } else {
                err |= __put_user(ksig->info.si_signo, &frame->info.si_signo);
        }

        /* Create the ucontext.  */
        err |= __clear_user(&frame->save_area, sizeof(frame->save_area));
        err |= __put_user(0, &frame->uc.uc_flags);
        err |= __put_user(NULL, &frame->uc.uc_link);
        err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
        err |= setup_sigcontext(&frame->uc.uc_mcontext, regs);
        err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
        if (err)
                goto err;

        restorer = VDSO_SYM(&__vdso_rt_sigreturn);
        if (ksig->ka.sa.sa_flags & SA_RESTORER)
                restorer = (unsigned long) ksig->ka.sa.sa_restorer;

        /*
         * Set up registers for signal handler.
         * Registers that we don't modify keep the value they had from
         * user-space at the time we took the signal.
         * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
         * since some things rely on this (e.g. glibc's debug/segfault.c).
         */
        regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
        regs->ex1 = PL_ICS_EX1(USER_PL, 1); /* set crit sec in handler */
        regs->sp = (unsigned long) frame;
        regs->lr = restorer;
        regs->regs[0] = (unsigned long) sig;
        regs->regs[1] = (unsigned long) &frame->info;
        regs->regs[2] = (unsigned long) &frame->uc;
        regs->flags |= PT_FLAGS_CALLER_SAVES;
        return 0;

err:
        trace_unhandled_signal("bad sigreturn frame", regs,
                              (unsigned long)frame, SIGSEGV);
        return -EFAULT;
}

/*
 * OK, we're invoking a handler
 */

static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
        sigset_t *oldset = sigmask_to_save();
        int ret;

        /* Are we from a system call? */
        if (regs->faultnum == INT_SWINT_1) {
                /* If so, check system call restarting.. */
                switch (regs->regs[0]) {
                case -ERESTART_RESTARTBLOCK:
                case -ERESTARTNOHAND:
                        regs->regs[0] = -EINTR;
                        break;

                case -ERESTARTSYS:
                        if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
                                regs->regs[0] = -EINTR;
                                break;
                        }
                        /* fallthrough */
                case -ERESTARTNOINTR:
                        /* Reload caller-saves to restore r0..r5 and r10. */
                        regs->flags |= PT_FLAGS_CALLER_SAVES;
                        regs->regs[0] = regs->orig_r0;
                        regs->pc -= 8;
                }
        }

        /* Set up the stack frame */
#ifdef CONFIG_COMPAT
        if (is_compat_task())
                ret = compat_setup_rt_frame(ksig, oldset, regs);
        else
#endif
                ret = setup_rt_frame(ksig, oldset, regs);

        signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
}

/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 */
void do_signal(struct pt_regs *regs)
{
        struct ksignal ksig;

        /*
         * i386 will check if we're coming from kernel mode and bail out
         * here.  In my experience this just turns weird crashes into
         * weird spin-hangs.  But if we find a case where this seems
         * helpful, we can reinstate the check on "!user_mode(regs)".
         */

        if (get_signal(&ksig)) {
                /* Whee! Actually deliver the signal.  */
                handle_signal(&ksig, regs);
                goto done;
        }

        /* Did we come from a system call? */
        if (regs->faultnum == INT_SWINT_1) {
                /* Restart the system call - no handlers present */
                switch (regs->regs[0]) {
                case -ERESTARTNOHAND:
                case -ERESTARTSYS:
                case -ERESTARTNOINTR:
                        regs->flags |= PT_FLAGS_CALLER_SAVES;
                        regs->regs[0] = regs->orig_r0;
                        regs->pc -= 8;
                        break;

                case -ERESTART_RESTARTBLOCK:
                        regs->flags |= PT_FLAGS_CALLER_SAVES;
                        regs->regs[TREG_SYSCALL_NR] = __NR_restart_syscall;
                        regs->pc -= 8;
                        break;
                }
        }

        /* If there's no signal to deliver, just put the saved sigmask back. */
        restore_saved_sigmask();

done:
        /* Avoid double syscall restart if there are nested signals. */
        regs->faultnum = INT_SWINT_1_SIGRETURN;
}

int show_unhandled_signals = 1;

static int __init crashinfo(char *str)
{
        const char *word;

        if (*str == '\0')
                show_unhandled_signals = 2;
        else if (*str != '=' || kstrtoint(++str, 0, &show_unhandled_signals) != 0)
                return 0;

        switch (show_unhandled_signals) {
        case 0:
                word = "No";
                break;
        case 1:
                word = "One-line";
                break;
        default:
                word = "Detailed";
                break;
        }
        pr_info("%s crash reports will be generated on the console\n", word);
        return 1;
}
__setup("crashinfo", crashinfo);

static void dump_mem(void __user *address)
{
        void __user *addr;
        enum { region_size = 256, bytes_per_line = 16 };
        int i, j, k;
        int found_readable_mem = 0;

        if (!access_ok(VERIFY_READ, address, 1)) {
                pr_err("Not dumping at address 0x%lx (kernel address)\n",
                       (unsigned long)address);
                return;
        }

        addr = (void __user *)
                (((unsigned long)address & -bytes_per_line) - region_size/2);
        if (addr > address)
                addr = NULL;
        for (i = 0; i < region_size;
             addr += bytes_per_line, i += bytes_per_line) {
                unsigned char buf[bytes_per_line];
                char line[100];
                if (copy_from_user(buf, addr, bytes_per_line))
                        continue;
                if (!found_readable_mem) {
                        pr_err("Dumping memory around address 0x%lx:\n",
                               (unsigned long)address);
                        found_readable_mem = 1;
                }
                j = sprintf(line, REGFMT ":", (unsigned long)addr);
                for (k = 0; k < bytes_per_line; ++k)
                        j += sprintf(&line[j], " %02x", buf[k]);
                pr_err("%s\n", line);
        }
        if (!found_readable_mem)
                pr_err("No readable memory around address 0x%lx\n",
                       (unsigned long)address);
}

void trace_unhandled_signal(const char *type, struct pt_regs *regs,
                            unsigned long address, int sig)
{
        struct task_struct *tsk = current;

        if (show_unhandled_signals == 0)
                return;

        /* If the signal is handled, don't show it here. */
        if (!is_global_init(tsk)) {
                void __user *handler =
                        tsk->sighand->action[sig-1].sa.sa_handler;
                if (handler != SIG_IGN && handler != SIG_DFL)
                        return;
        }

        /* Rate-limit the one-line output, not the detailed output. */
        if (show_unhandled_signals <= 1 && !printk_ratelimit())
                return;

        printk("%s%s[%d]: %s at %lx pc "REGFMT" signal %d",
               task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
               tsk->comm, task_pid_nr(tsk), type, address, regs->pc, sig);

        print_vma_addr(KERN_CONT " in ", regs->pc);

        printk(KERN_CONT "\n");

        if (show_unhandled_signals > 1) {
                switch (sig) {
                case SIGILL:
                case SIGFPE:
                case SIGSEGV:
                case SIGBUS:
                        pr_err("User crash: signal %d, trap %ld, address 0x%lx\n",
                               sig, regs->faultnum, address);
                        show_regs(regs);
                        dump_mem((void __user *)address);
                        break;
                default:
                        pr_err("User crash: signal %d, trap %ld\n",
                               sig, regs->faultnum);
                        break;
                }
        }
}