/*
 *  linux/arch/arm/kernel/ptrace.c
 *
 *  By Ross Biro 1/23/92
 * edited by Linus Torvalds
 * ARM modifications Copyright (C) 2000 Russell King
 *
 * 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.
 */
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/ptrace.h>
#include <linux/user.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/system.h>

#include "ptrace.h"

#define REG_PC  15
#define REG_PSR 16
/*
 * does not yet catch signals sent when the child dies.
 * in exit.c or in signal.c.
 */

/*
 * Breakpoint SWI instruction: SWI &9F0001
 */
#define BREAKINST       0xef9f0001

/*
 * Get the address of the live pt_regs for the specified task.
 * These are saved onto the top kernel stack when the process
 * is not running.
 */
static inline struct pt_regs *
get_user_regs(struct task_struct *task)
{
        return (struct pt_regs *)
                ((unsigned long)task + 8192 - sizeof(struct pt_regs));
}

/*
 * this routine will get a word off of the processes privileged stack.
 * the offset is how far from the base addr as stored in the THREAD.
 * this routine assumes that all the privileged stacks are in our
 * data space.
 */
static inline long get_stack_long(struct task_struct *task, int offset)
{
        return get_user_regs(task)->uregs[offset];
}

/*
 * this routine will put a word on the processes privileged stack.
 * the offset is how far from the base addr as stored in the THREAD.
 * this routine assumes that all the privileged stacks are in our
 * data space.
 */
static inline int
put_stack_long(struct task_struct *task, int offset, long data)
{
        struct pt_regs newregs, *regs = get_user_regs(task);
        int ret = -EINVAL;

        newregs = *regs;
        newregs.uregs[offset] = data;
        
        if (valid_user_regs(&newregs)) {
                regs->uregs[offset] = data;
                ret = 0;
        }

        return ret;
}

static inline int
read_tsk_long(struct task_struct *child, unsigned long addr, unsigned long *res)
{
        int copied;

        copied = access_process_vm(child, addr, res, sizeof(*res), 0);

        return copied != sizeof(*res) ? -EIO : 0;
}

static inline int
write_tsk_long(struct task_struct *child, unsigned long addr, unsigned long val)
{
        int copied;

        copied = access_process_vm(child, addr, &val, sizeof(val), 1);

        return copied != sizeof(val) ? -EIO : 0;
}

/*
 * Get value of register `rn' (in the instruction)
 */
static unsigned long
ptrace_getrn(struct task_struct *child, unsigned long insn)
{
        unsigned int reg = (insn >> 16) & 15;
        unsigned long val;

        val = get_stack_long(child, reg);
        if (reg == 15)
                val = pc_pointer(val + 8);

        return val;
}

/*
 * Get value of operand 2 (in an ALU instruction)
 */
static unsigned long
ptrace_getaluop2(struct task_struct *child, unsigned long insn)
{
        unsigned long val;
        int shift;
        int type;

        if (insn & 1 << 25) {
                val = insn & 255;
                shift = (insn >> 8) & 15;
                type = 3;
        } else {
                val = get_stack_long (child, insn & 15);

                if (insn & (1 << 4))
                        shift = (int)get_stack_long (child, (insn >> 8) & 15);
                else
                        shift = (insn >> 7) & 31;

                type = (insn >> 5) & 3;
        }

        switch (type) {
        case 0: val <<= shift;  break;
        case 1: val >>= shift;  break;
        case 2:
                val = (((signed long)val) >> shift);
                break;
        case 3:
                val = (val >> shift) | (val << (32 - shift));
                break;
        }
        return val;
}

/*
 * Get value of operand 2 (in a LDR instruction)
 */
static unsigned long
ptrace_getldrop2(struct task_struct *child, unsigned long insn)
{
        unsigned long val;
        int shift;
        int type;

        val = get_stack_long(child, insn & 15);
        shift = (insn >> 7) & 31;
        type = (insn >> 5) & 3;

        switch (type) {
        case 0: val <<= shift;  break;
        case 1: val >>= shift;  break;
        case 2:
                val = (((signed long)val) >> shift);
                break;
        case 3:
                val = (val >> shift) | (val << (32 - shift));
                break;
        }
        return val;
}

static unsigned long
get_branch_address(struct task_struct *child, unsigned long pc, unsigned long insn)
{
        unsigned long alt = 0;

        switch (insn & 0x0e000000) {
        case 0x00000000:
        case 0x02000000: {
                /*
                 * data processing
                 */
                long aluop1, aluop2, ccbit;

                if ((insn & 0xf000) != 0xf000)
                        break;

                aluop1 = ptrace_getrn(child, insn);
                aluop2 = ptrace_getaluop2(child, insn);
                ccbit  = get_stack_long(child, REG_PSR) & CC_C_BIT ? 1 : 0;

                switch (insn & 0x01e00000) {
                case 0x00000000: alt = aluop1 & aluop2;         break;
                case 0x00200000: alt = aluop1 ^ aluop2;         break;
                case 0x00400000: alt = aluop1 - aluop2;         break;
                case 0x00600000: alt = aluop2 - aluop1;         break;
                case 0x00800000: alt = aluop1 + aluop2;         break;
                case 0x00a00000: alt = aluop1 + aluop2 + ccbit; break;
                case 0x00c00000: alt = aluop1 - aluop2 + ccbit; break;
                case 0x00e00000: alt = aluop2 - aluop1 + ccbit; break;
                case 0x01800000: alt = aluop1 | aluop2;         break;
                case 0x01a00000: alt = aluop2;                  break;
                case 0x01c00000: alt = aluop1 & ~aluop2;        break;
                case 0x01e00000: alt = ~aluop2;                 break;
                }
                break;
        }

        case 0x04000000:
        case 0x06000000:
                /*
                 * ldr
                 */
                if ((insn & 0x0010f000) == 0x0010f000) {
                        unsigned long base;

                        base = ptrace_getrn(child, insn);
                        if (insn & 1 << 24) {
                                long aluop2;

                                if (insn & 0x02000000)
                                        aluop2 = ptrace_getldrop2(child, insn);
                                else
                                        aluop2 = insn & 0xfff;

                                if (insn & 1 << 23)
                                        base += aluop2;
                                else
                                        base -= aluop2;
                        }
                        if (read_tsk_long(child, base, &alt) == 0)
                                alt = pc_pointer(alt);
                }
                break;

        case 0x08000000:
                /*
                 * ldm
                 */
                if ((insn & 0x00108000) == 0x00108000) {
                        unsigned long base;
                        unsigned int nr_regs;

                        if (insn & (1 << 23)) {
                                nr_regs = insn & 65535;

                                nr_regs = (nr_regs & 0x5555) + ((nr_regs & 0xaaaa) >> 1);
                                nr_regs = (nr_regs & 0x3333) + ((nr_regs & 0xcccc) >> 2);
                                nr_regs = (nr_regs & 0x0707) + ((nr_regs & 0x7070) >> 4);
                                nr_regs = (nr_regs & 0x000f) + ((nr_regs & 0x0f00) >> 8);
                                nr_regs <<= 2;

                                if (!(insn & (1 << 24)))
                                        nr_regs -= 4;
                        } else {
                                if (insn & (1 << 24))
                                        nr_regs = -4;
                                else
                                        nr_regs = 0;
                        }

                        base = ptrace_getrn(child, insn);

                        if (read_tsk_long(child, base + nr_regs, &alt) == 0)
                                alt = pc_pointer (alt);
                        break;
                }
                break;

        case 0x0a000000: {
                /*
                 * bl or b
                 */
                signed long displ;
                /* It's a branch/branch link: instead of trying to
                 * figure out whether the branch will be taken or not,
                 * we'll put a breakpoint at both locations.  This is
                 * simpler, more reliable, and probably not a whole lot
                 * slower than the alternative approach of emulating the
                 * branch.
                 */
                displ = (insn & 0x00ffffff) << 8;
                displ = (displ >> 6) + 8;
                if (displ != 0 && displ != 4)
                        alt = pc + displ;
            }
            break;
        }

        return alt;
}

static int
add_breakpoint(struct task_struct *child, struct debug_info *dbg, unsigned long addr)
{
        int nr = dbg->nsaved;
        int res = -EINVAL;

        if (nr < 2) {
                res = read_tsk_long(child, addr, &dbg->bp[nr].insn);
                if (res == 0)
                        res = write_tsk_long(child, addr, BREAKINST);

                if (res == 0) {
                        dbg->bp[nr].address = addr;
                        dbg->nsaved += 1;
                }
        } else
                printk(KERN_ERR "ptrace: too many breakpoints\n");

        return res;
}

int ptrace_set_bpt(struct task_struct *child)
{
        struct pt_regs *regs;
        unsigned long pc, insn;
        int res;

        regs = get_user_regs(child);
        pc = instruction_pointer(regs);

        res = read_tsk_long(child, pc, &insn);
        if (!res) {
                struct debug_info *dbg = &child->thread.debug;
                unsigned long alt;

                dbg->nsaved = 0;

                alt = get_branch_address(child, pc, insn);
                if (alt)
                        res = add_breakpoint(child, dbg, alt);

                /*
                 * Note that we ignore the result of setting the above
                 * breakpoint since it may fail.  When it does, this is
                 * not so much an error, but a forewarning that we may
                 * be receiving a prefetch abort shortly.
                 *
                 * If we don't set this breakpoint here, then we can
                 * loose control of the thread during single stepping.
                 */
                if (!alt || predicate(insn) != PREDICATE_ALWAYS)
                        res = add_breakpoint(child, dbg, pc + 4);
        }

        return res;
}

/*
 * Ensure no single-step breakpoint is pending.  Returns non-zero
 * value if child was being single-stepped.
 */
void __ptrace_cancel_bpt(struct task_struct *child)
{
        struct debug_info *dbg = &child->thread.debug;
        int i, nsaved = dbg->nsaved;

        dbg->nsaved = 0;

        if (nsaved > 2) {
                printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
                nsaved = 2;
        }

        for (i = 0; i < nsaved; i++) {
                unsigned long tmp;

                read_tsk_long(child, dbg->bp[i].address, &tmp);
                write_tsk_long(child, dbg->bp[i].address, dbg->bp[i].insn);
                if (tmp != BREAKINST)
                        printk(KERN_ERR "ptrace_cancel_bpt: weirdness\n");
        }
}

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Make sure the single step bit is not set.
 */
void ptrace_disable(struct task_struct *child)
{
        __ptrace_cancel_bpt(child);
}

static int do_ptrace(int request, struct task_struct *child, long addr, long data)
{
        unsigned long tmp;
        int ret;

        switch (request) {
                /*
                 * read word at location "addr" in the child process.
                 */
                case PTRACE_PEEKTEXT:
                case PTRACE_PEEKDATA:
                        ret = read_tsk_long(child, addr, &tmp);
                        if (!ret)
                                ret = put_user(tmp, (unsigned long *) data);
                        break;

                /*
                 * read the word at location "addr" in the user registers.
                 */
                case PTRACE_PEEKUSR:
                        ret = -EIO;
                        if ((addr & 3) || addr < 0 || addr >= sizeof(struct user))
                                break;

                        tmp = 0;  /* Default return condition */
                        if (addr < sizeof(struct pt_regs))
                                tmp = get_stack_long(child, (int)addr >> 2);
                        ret = put_user(tmp, (unsigned long *)data);
                        break;

                /*
                 * write the word at location addr.
                 */
                case PTRACE_POKETEXT:
                case PTRACE_POKEDATA:
                        ret = write_tsk_long(child, addr, data);
                        break;

                /*
                 * write the word at location addr in the user registers.
                 */
                case PTRACE_POKEUSR:
                        ret = -EIO;
                        if ((addr & 3) || addr < 0 || addr >= sizeof(struct user))
                                break;

                        if (addr < sizeof(struct pt_regs))
                                ret = put_stack_long(child, (int)addr >> 2, data);
                        break;

                /*
                 * continue/restart and stop at next (return from) syscall
                 */
                case PTRACE_SYSCALL:
                case PTRACE_CONT:
                        ret = -EIO;
                        if ((unsigned long) data > _NSIG)
                                break;
                        if (request == PTRACE_SYSCALL)
                                child->ptrace |= PT_TRACESYS;
                        else
                                child->ptrace &= ~PT_TRACESYS;
                        child->exit_code = data;
                        /* make sure single-step breakpoint is gone. */
                        __ptrace_cancel_bpt(child);
                        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:
                        /* already dead */
                        ret = 0;
                        if (child->state == TASK_ZOMBIE)
                                break;
                        child->exit_code = SIGKILL;
                        /* make sure single-step breakpoint is gone. */
                        __ptrace_cancel_bpt(child);
                        wake_up_process(child);
                        ret = 0;
                        break;

                /*
                 * execute single instruction.
                 */
                case PTRACE_SINGLESTEP:
                        ret = -EIO;
                        if ((unsigned long) data > _NSIG)
                                break;
                        child->thread.debug.nsaved = -1;
                        child->ptrace &= ~PT_TRACESYS;
                        child->exit_code = data;
                        /* give it a chance to run. */
                        wake_up_process(child);
                        ret = 0;
                        break;

                /*
                 * detach a process that was attached.
                 */
                case PTRACE_DETACH:
                        ret = ptrace_detach(child, data);
                        break;

                /*
                 * Get all gp regs from the child.
                 */
                case PTRACE_GETREGS: {
                        struct pt_regs *regs = get_user_regs(child);

                        ret = 0;
                        if (copy_to_user((void *)data, regs,
                                         sizeof(struct pt_regs)))
                                ret = -EFAULT;

                        break;
                }

                /*
                 * Set all gp regs in the child.
                 */
                case PTRACE_SETREGS: {
                        struct pt_regs newregs;

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

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

                /*
                 * Get the child FPU state.
                 */
                case PTRACE_GETFPREGS:
                        ret = -EIO;
                        if (!access_ok(VERIFY_WRITE, (void *)data, sizeof(struct user_fp)))
                                break;

                        /* we should check child->used_math here */
                        ret = __copy_to_user((void *)data, &child->thread.fpstate,
                                             sizeof(struct user_fp)) ? -EFAULT : 0;
                        break;
                
                /*
                 * Set the child FPU state.
                 */
                case PTRACE_SETFPREGS:
                        ret = -EIO;
                        if (!access_ok(VERIFY_READ, (void *)data, sizeof(struct user_fp)))
                                break;

                        child->used_math = 1;
                        ret = __copy_from_user(&child->thread.fpstate, (void *)data,
                                           sizeof(struct user_fp)) ? -EFAULT : 0;
                        break;

                default:
                        ret = -EIO;
                        break;
        }

        return ret;
}

asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
{
        struct task_struct *child;
        int ret;

        lock_kernel();
        ret = -EPERM;
        if (request == PTRACE_TRACEME) {
                /* are we already being traced? */
                if (current->ptrace & PT_PTRACED)
                        goto out;
                /* set the ptrace bit in the process flags. */
                current->ptrace |= PT_PTRACED;
                ret = 0;
                goto out;
        }
        ret = -ESRCH;
        read_lock(&tasklist_lock);
        child = find_task_by_pid(pid);
        if (child)
                get_task_struct(child);
        read_unlock(&tasklist_lock);
        if (!child)
                goto out;

        ret = -EPERM;
        if (pid == 1)           /* you may not mess with init */
                goto out_tsk;

        if (request == PTRACE_ATTACH) {
                ret = ptrace_attach(child);
                goto out_tsk;
        }
        ret = -ESRCH;
        if (!(child->ptrace & PT_PTRACED))
                goto out_tsk;
        if (child->state != TASK_STOPPED && request != PTRACE_KILL)
                goto out_tsk;
        if (child->p_pptr != current)
                goto out_tsk;

        ret = do_ptrace(request, child, addr, data);

out_tsk:
        free_task_struct(child);
out:
        unlock_kernel();
        return ret;
}

asmlinkage void syscall_trace(int why, struct pt_regs *regs)
{
        unsigned long ip;

        if ((current->ptrace & (PT_PTRACED|PT_TRACESYS))
                        != (PT_PTRACED|PT_TRACESYS))
                return;

        /*
         * Save IP.  IP is used to denote syscall entry/exit:
         *  IP = 0 -> entry, = 1 -> exit
         */
        ip = regs->ARM_ip;
        regs->ARM_ip = why;

        /* the 0x80 provides a way for the tracing parent to distinguish
           between a syscall stop and SIGTRAP delivery */
        current->exit_code = SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
                                        ? 0x80 : 0);
        current->state = TASK_STOPPED;
        notify_parent(current, SIGCHLD);
        schedule();
        /*
         * 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) {
                send_sig(current->exit_code, current, 1);
                current->exit_code = 0;
        }
        regs->ARM_ip = ip;
}