ptrace.c

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/*
 * Copyright (C) 2000-2003, Axis Communications AB.
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/signal.h>
#include <linux/security.h>

#include <asm/uaccess.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/processor.h>

/* 
 * Determines which bits in DCCR the user has access to.
 * 1 = access, 0 = no access.
 */
#define DCCR_MASK 0x0000001f     /* XNZVC */

/*
 * Get contents of register REGNO in task TASK.
 */
inline long get_reg(struct task_struct *task, unsigned int regno)
{
    /* USP is a special case, it's not in the pt_regs struct but
     * in the tasks thread struct
     */

    if (regno == PT_USP)
        return task->thread.usp;
    else if (regno < PT_MAX)
        return ((unsigned long *)task_pt_regs(task))[regno];
    else
        return 0;
}

/*
 * Write contents of register REGNO in task TASK.
 */
inline int put_reg(struct task_struct *task, unsigned int regno,
              unsigned long data)
{
    if (regno == PT_USP)
        task->thread.usp = data;
    else if (regno < PT_MAX)
        ((unsigned long *)task_pt_regs(task))[regno] = data;
    else
        return -1;
    return 0;
}

/*
 * Called by kernel/ptrace.c when detaching.
 *
 * Make sure the single step bit is not set.
 */
void 
ptrace_disable(struct task_struct *child)
{
       /* Todo - pending singlesteps? */
       clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
}

/* 
 * Note that this implementation of ptrace behaves differently from vanilla
 * ptrace.  Contrary to what the man page says, in the PTRACE_PEEKTEXT,
 * PTRACE_PEEKDATA, and PTRACE_PEEKUSER requests the data variable is not
 * ignored.  Instead, the data variable is expected to point at a location
 * (in user space) where the result of the ptrace call is written (instead of
 * being returned).
 */
long arch_ptrace(struct task_struct *child, long request,
         unsigned long addr, unsigned long data)
{
    int ret;
    unsigned int regno = addr >> 2;
    unsigned long __user *datap = (unsigned long __user *)data;

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

        /* Read the word at location address in the USER area. */
        case PTRACE_PEEKUSR: {
            unsigned long tmp;

            ret = -EIO;
            if ((addr & 3) || regno > PT_MAX)
                break;

            tmp = get_reg(child, regno);
            ret = put_user(tmp, datap);
            break;
        }
        
        /* Write the word at location address. */
        case PTRACE_POKETEXT:
        case PTRACE_POKEDATA:
            ret = generic_ptrace_pokedata(child, addr, data);
            break;
 
        /* Write the word at location address in the USER area. */
        case PTRACE_POKEUSR:
            ret = -EIO;
            if ((addr & 3) || regno > PT_MAX)
                break;

            if (regno == PT_DCCR) {
                /* don't allow the tracing process to change stuff like
                 * interrupt enable, kernel/user bit, dma enables etc.
                 */
                data &= DCCR_MASK;
                data |= get_reg(child, PT_DCCR) & ~DCCR_MASK;
            }
            if (put_reg(child, regno, data))
                break;
            ret = 0;
            break;

        /* Get all GP registers from the child. */
        case PTRACE_GETREGS: {
            int i;
            unsigned long tmp;
            
            ret = 0;
            for (i = 0; i <= PT_MAX; i++) {
                tmp = get_reg(child, i);
                
                if (put_user(tmp, datap)) {
                    ret = -EFAULT;
                    break;
                }
                
                datap++;
            }

            break;
        }

        /* Set all GP registers in the child. */
        case PTRACE_SETREGS: {
            int i;
            unsigned long tmp;
            
            ret = 0;
            for (i = 0; i <= PT_MAX; i++) {
                if (get_user(tmp, datap)) {
                    ret = -EFAULT;
                    break;
                }
                
                if (i == PT_DCCR) {
                    tmp &= DCCR_MASK;
                    tmp |= get_reg(child, PT_DCCR) & ~DCCR_MASK;
                }
                
                put_reg(child, i, tmp);
                datap++;
            }
            
            break;
        }

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

    return ret;
}

void do_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.
     */
    if (current->exit_code) {
        send_sig(current->exit_code, current, 1);
        current->exit_code = 0;
    }
}