/*
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#undef DEBUG
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/errno.h>
#include <linux/user.h>
#include <linux/security.h>
#include <linux/unistd.h>
#include <linux/notifier.h>

#include <asm/traps.h>
#include <asm/uaccess.h>
#include <asm/ocd.h>
#include <asm/mmu_context.h>
#include <linux/kdebug.h>

static struct pt_regs *get_user_regs(struct task_struct *tsk)
{
        return (struct pt_regs *)((unsigned long)task_stack_page(tsk) +
                                  THREAD_SIZE - sizeof(struct pt_regs));
}

static void ptrace_single_step(struct task_struct *tsk)
{
        pr_debug("ptrace_single_step: pid=%u, PC=0x%08lx, SR=0x%08lx\n",
                 tsk->pid, task_pt_regs(tsk)->pc, task_pt_regs(tsk)->sr);

        /*
         * We can't schedule in Debug mode, so when TIF_BREAKPOINT is
         * set, the system call or exception handler will do a
         * breakpoint to enter monitor mode before returning to
         * userspace.
         *
         * The monitor code will then notice that TIF_SINGLE_STEP is
         * set and return to userspace with single stepping enabled.
         * The CPU will then enter monitor mode again after exactly
         * one instruction has been executed, and the monitor code
         * will then send a SIGTRAP to the process.
         */
        set_tsk_thread_flag(tsk, TIF_BREAKPOINT);
        set_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
}

/*
 * Called by kernel/ptrace.c when detaching
 *
 * Make sure any single step bits, etc. are not set
 */
void ptrace_disable(struct task_struct *child)
{
        clear_tsk_thread_flag(child, TIF_SINGLE_STEP);
        clear_tsk_thread_flag(child, TIF_BREAKPOINT);
        ocd_disable(child);
}

/*
 * Read the word at offset "offset" into the task's "struct user". We
 * actually access the pt_regs struct stored on the kernel stack.
 */
static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
                            unsigned long __user *data)
{
        unsigned long *regs;
        unsigned long value;

        if (offset & 3 || offset >= sizeof(struct user)) {
                printk("ptrace_read_user: invalid offset 0x%08lx\n", offset);
                return -EIO;
        }

        regs = (unsigned long *)get_user_regs(tsk);

        value = 0;
        if (offset < sizeof(struct pt_regs))
                value = regs[offset / sizeof(regs[0])];

        pr_debug("ptrace_read_user(%s[%u], %#lx, %p) -> %#lx\n",
                 tsk->comm, tsk->pid, offset, data, value);

        return put_user(value, data);
}

/*
 * Write the word "value" to offset "offset" into the task's "struct
 * user". We actually access the pt_regs struct stored on the kernel
 * stack.
 */
static int ptrace_write_user(struct task_struct *tsk, unsigned long offset,
                             unsigned long value)
{
        unsigned long *regs;

        pr_debug("ptrace_write_user(%s[%u], %#lx, %#lx)\n",
                        tsk->comm, tsk->pid, offset, value);

        if (offset & 3 || offset >= sizeof(struct user)) {
                pr_debug("  invalid offset 0x%08lx\n", offset);
                return -EIO;
        }

        if (offset >= sizeof(struct pt_regs))
                return 0;

        regs = (unsigned long *)get_user_regs(tsk);
        regs[offset / sizeof(regs[0])] = value;

        return 0;
}

static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
{
        struct pt_regs *regs = get_user_regs(tsk);

        return copy_to_user(uregs, regs, sizeof(*regs)) ? -EFAULT : 0;
}

static int ptrace_setregs(struct task_struct *tsk, const void __user *uregs)
{
        struct pt_regs newregs;
        int ret;

        ret = -EFAULT;
        if (copy_from_user(&newregs, uregs, sizeof(newregs)) == 0) {
                struct pt_regs *regs = get_user_regs(tsk);

                ret = -EINVAL;
                if (valid_user_regs(&newregs)) {
                        *regs = newregs;
                        ret = 0;
                }
        }

        return ret;
}

long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
        int ret;

        switch (request) {
        /* Read the word at location addr in the child process */
        case PTRACE_PEEKTEXT:
        case PTRACE_PEEKDATA:
                ret = generic_ptrace_peekdata(child, addr, data);
                break;

        case PTRACE_PEEKUSR:
                ret = ptrace_read_user(child, addr,
                                       (unsigned long __user *)data);
                break;

        /* Write the word in data at location addr */
        case PTRACE_POKETEXT:
        case PTRACE_POKEDATA:
                ret = generic_ptrace_pokedata(child, addr, data);
                break;

        case PTRACE_POKEUSR:
                ret = ptrace_write_user(child, addr, data);
                break;

        /* continue and stop at next (return from) syscall */
        case PTRACE_SYSCALL:
        /* restart after signal */
        case PTRACE_CONT:
                ret = -EIO;
                if (!valid_signal(data))
                        break;
                if (request == PTRACE_SYSCALL)
                        set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                else
                        clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                child->exit_code = data;
                /* XXX: Are we sure no breakpoints are active here? */
                wake_up_process(child);
                ret = 0;
                break;

        /*
         * Make the child exit. Best I can do is send it a
         * SIGKILL. Perhaps it should be put in the status that it
         * wants to exit.
         */
        case PTRACE_KILL:
                ret = 0;
                if (child->exit_state == EXIT_ZOMBIE)
                        break;
                child->exit_code = SIGKILL;
                wake_up_process(child);
                break;

        /*
         * execute single instruction.
         */
        case PTRACE_SINGLESTEP:
                ret = -EIO;
                if (!valid_signal(data))
                        break;
                clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                ptrace_single_step(child);
                child->exit_code = data;
                wake_up_process(child);
                ret = 0;
                break;

        case PTRACE_GETREGS:
                ret = ptrace_getregs(child, (void __user *)data);
                break;

        case PTRACE_SETREGS:
                ret = ptrace_setregs(child, (const void __user *)data);
                break;

        default:
                ret = ptrace_request(child, request, addr, data);
                break;
        }

        return ret;
}

asmlinkage void syscall_trace(void)
{
        if (!test_thread_flag(TIF_SYSCALL_TRACE))
                return;
        if (!(current->ptrace & PT_PTRACED))
                return;

        /* The 0x80 provides a way for the tracing parent to
         * distinguish between a syscall stop and SIGTRAP delivery */
        ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
                                 ? 0x80 : 0));

        /*
         * this isn't the same as continuing with a signal, but it
         * will do for normal use.  strace only continues with a
         * signal if the stopping signal is not SIGTRAP.  -brl
         */
        if (current->exit_code) {
                pr_debug("syscall_trace: sending signal %d to PID %u\n",
                         current->exit_code, current->pid);
                send_sig(current->exit_code, current, 1);
                current->exit_code = 0;
        }
}

/*
 * debug_trampoline() is an assembly stub which will store all user
 * registers on the stack and execute a breakpoint instruction.
 *
 * If we single-step into an exception handler which runs with
 * interrupts disabled the whole time so it doesn't have to check for
 * pending work, its return address will be modified so that it ends
 * up returning to debug_trampoline.
 *
 * If the exception handler decides to store the user context and
 * enable interrupts after all, it will restore the original return
 * address and status register value. Before it returns, it will
 * notice that TIF_BREAKPOINT is set and execute a breakpoint
 * instruction.
 */
extern void debug_trampoline(void);

asmlinkage struct pt_regs *do_debug(struct pt_regs *regs)
{
        struct thread_info      *ti;
        unsigned long           trampoline_addr;
        u32                     status;
        u32                     ctrl;
        int                     code;

        status = ocd_read(DS);
        ti = current_thread_info();
        code = TRAP_BRKPT;

        pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n",
                        status, regs->pc, regs->sr, ti->flags);

        if (!user_mode(regs)) {
                unsigned long   die_val = DIE_BREAKPOINT;

                if (status & (1 << OCD_DS_SSS_BIT))
                        die_val = DIE_SSTEP;

                if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP)
                                == NOTIFY_STOP)
                        return regs;

                if ((status & (1 << OCD_DS_SWB_BIT))
                                && test_and_clear_ti_thread_flag(
                                        ti, TIF_BREAKPOINT)) {
                        /*
                         * Explicit breakpoint from trampoline or
                         * exception/syscall/interrupt handler.
                         *
                         * The real saved regs are on the stack right
                         * after the ones we saved on entry.
                         */
                        regs++;
                        pr_debug("  -> TIF_BREAKPOINT done, adjusted regs:"
                                        "PC=0x%08lx SR=0x%08lx\n",
                                        regs->pc, regs->sr);
                        BUG_ON(!user_mode(regs));

                        if (test_thread_flag(TIF_SINGLE_STEP)) {
                                pr_debug("Going to do single step...\n");
                                return regs;
                        }

                        /*
                         * No TIF_SINGLE_STEP means we're done
                         * stepping over a syscall. Do the trap now.
                         */
                        code = TRAP_TRACE;
                } else if ((status & (1 << OCD_DS_SSS_BIT))
                                && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) {

                        pr_debug("Stepped into something, "
                                        "setting TIF_BREAKPOINT...\n");
                        set_ti_thread_flag(ti, TIF_BREAKPOINT);

                        /*
                         * We stepped into an exception, interrupt or
                         * syscall handler. Some exception handlers
                         * don't check for pending work, so we need to
                         * set up a trampoline just in case.
                         *
                         * The exception entry code will undo the
                         * trampoline stuff if it does a full context
                         * save (which also means that it'll check for
                         * pending work later.)
                         */
                        if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) {
                                trampoline_addr
                                        = (unsigned long)&debug_trampoline;

                                pr_debug("Setting up trampoline...\n");
                                ti->rar_saved = sysreg_read(RAR_EX);
                                ti->rsr_saved = sysreg_read(RSR_EX);
                                sysreg_write(RAR_EX, trampoline_addr);
                                sysreg_write(RSR_EX, (MODE_EXCEPTION
                                                        | SR_EM | SR_GM));
                                BUG_ON(ti->rsr_saved & MODE_MASK);
                        }

                        /*
                         * If we stepped into a system call, we
                         * shouldn't do a single step after we return
                         * since the return address is right after the
                         * "scall" instruction we were told to step
                         * over.
                         */
                        if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) {
                                pr_debug("Supervisor; no single step\n");
                                clear_ti_thread_flag(ti, TIF_SINGLE_STEP);
                        }

                        ctrl = ocd_read(DC);
                        ctrl &= ~(1 << OCD_DC_SS_BIT);
                        ocd_write(DC, ctrl);

                        return regs;
                } else {
                        printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n",
                                        status);
                        printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags);
                        die("Unhandled debug trap in kernel mode",
                                        regs, SIGTRAP);
                }
        } else if (status & (1 << OCD_DS_SSS_BIT)) {
                /* Single step in user mode */
                code = TRAP_TRACE;

                ctrl = ocd_read(DC);
                ctrl &= ~(1 << OCD_DC_SS_BIT);
                ocd_write(DC, ctrl);
        }

        pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n",
                        code, regs->pc, regs->sr);

        clear_thread_flag(TIF_SINGLE_STEP);
        _exception(SIGTRAP, regs, code, instruction_pointer(regs));

        return regs;
}