kernel/ptrace.c

   1 /*
   2  * linux/kernel/ptrace.c
   3  *
   4  * (C) Copyright 1999 Linus Torvalds
   5  *
   6  * Common interfaces for "ptrace()" which we do not want
   7  * to continually duplicate across every architecture.
   8  */
   9
  10 #include <linux/sched.h>
  11 #include <linux/errno.h>
  12 #include <linux/mm.h>
  13 #include <linux/highmem.h>
  14 #include <linux/pagemap.h>
  15 #include <linux/smp_lock.h>
  16 #include <linux/ptrace.h>
  17
  18 #include <asm/pgtable.h>
  19 #include <asm/uaccess.h>
  20
  21 /*
  22  * ptrace a task: make the debugger its new parent and
  23  * move it to the ptrace list.
  24  *
  25  * Must be called with the tasklist lock write-held.
  26  */
  27 void __ptrace_link(task_t *child, task_t *new_parent)
  28 {
  29         if (!list_empty(&child->ptrace_list))
  30                 BUG();
  31         if (child->parent == new_parent)
  32                 return;
  33         list_add(&child->ptrace_list, &child->parent->ptrace_children);
  34         REMOVE_LINKS(child);
  35         child->parent = new_parent;
  36         SET_LINKS(child);
  37 }
  38
  39 /*
  40  * unptrace a task: move it back to its original parent and
  41  * remove it from the ptrace list.
  42  *
  43  * Must be called with the tasklist lock write-held.
  44  */
  45 void __ptrace_unlink(task_t *child)
  46 {
  47         if (!child->ptrace)
  48                 BUG();
  49         child->ptrace = 0;
  50         if (list_empty(&child->ptrace_list))
  51                 return;
  52         list_del_init(&child->ptrace_list);
  53         REMOVE_LINKS(child);
  54         child->parent = child->real_parent;
  55         SET_LINKS(child);
  56 }
  57
  58 /*
  59  * Check that we have indeed attached to the thing..
  60  */
  61 int ptrace_check_attach(struct task_struct *child, int kill)
  62 {
  63         if (!(child->ptrace & PT_PTRACED))
  64                 return -ESRCH;
  65
  66         if (child->parent != current)
  67                 return -ESRCH;
  68
  69         if (!kill) {
  70                 if (child->state != TASK_STOPPED)
  71                         return -ESRCH;
  72                 wait_task_inactive(child);
  73         }
  74
  75         /* All systems go.. */
  76         return 0;
  77 }
  78
  79 int ptrace_attach(struct task_struct *task)
  80 {
  81         int retval;
  82         task_lock(task);
  83         retval = -EPERM;
  84         if (task->pid <= 1)
  85                 goto bad;
  86         if (task == current)
  87                 goto bad;
  88         if (!task->mm)
  89                 goto bad;
  90         if(((current->uid != task->euid) ||
  91             (current->uid != task->suid) ||
  92             (current->uid != task->uid) ||
  93             (current->gid != task->egid) ||
  94             (current->gid != task->sgid) ||
  95             (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
  96                 goto bad;
  97         rmb();
  98         if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
  99                 goto bad;
 100         /* the same process cannot be attached many times */
 101         if (task->ptrace & PT_PTRACED)
 102                 goto bad;
 103         retval = security_ops->ptrace(current, task);
 104         if (retval)
 105                 goto bad;
 106
 107         /* Go */
 108         task->ptrace |= PT_PTRACED;
 109         if (capable(CAP_SYS_PTRACE))
 110                 task->ptrace |= PT_PTRACE_CAP;
 111         task_unlock(task);
 112
 113         write_lock_irq(&tasklist_lock);
 114         __ptrace_link(task, current);
 115         write_unlock_irq(&tasklist_lock);
 116
 117         send_sig(SIGSTOP, task, 1);
 118         return 0;
 119
 120 bad:
 121         task_unlock(task);
 122         return retval;
 123 }
 124
 125 int ptrace_detach(struct task_struct *child, unsigned int data)
 126 {
 127         if ((unsigned long) data > _NSIG)
 128                 return  -EIO;
 129
 130         /* Architecture-specific hardware disable .. */
 131         ptrace_disable(child);
 132
 133         /* .. re-parent .. */
 134         child->exit_code = data;
 135
 136         write_lock_irq(&tasklist_lock);
 137         __ptrace_unlink(child);
 138         /* .. and wake it up. */
 139         if (child->state != TASK_ZOMBIE)
 140                 wake_up_process(child);
 141         write_unlock_irq(&tasklist_lock);
 142
 143         return 0;
 144 }
 145
 146 /*
 147  * Access another process' address space.
 148  * Source/target buffer must be kernel space,
 149  * Do not walk the page table directly, use get_user_pages
 150  */
 151
 152 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
 153 {
 154         struct mm_struct *mm;
 155         struct vm_area_struct *vma;
 156         struct page *page;
 157         void *old_buf = buf;
 158
 159         mm = get_task_mm(tsk);
 160         if (!mm)
 161                 return 0;
 162
 163         down_read(&mm->mmap_sem);
 164         /* ignore errors, just check how much was sucessfully transfered */
 165         while (len) {
 166                 int bytes, ret, offset;
 167                 void *maddr;
 168
 169                 ret = get_user_pages(current, mm, addr, 1,
 170                                 write, 1, &page, &vma);
 171                 if (ret <= 0)
 172                         break;
 173
 174                 bytes = len;
 175                 offset = addr & (PAGE_SIZE-1);
 176                 if (bytes > PAGE_SIZE-offset)
 177                         bytes = PAGE_SIZE-offset;
 178
 179                 flush_cache_page(vma, addr);
 180
 181                 maddr = kmap(page);
 182                 if (write) {
 183                         memcpy(maddr + offset, buf, bytes);
 184                         flush_page_to_ram(page);
 185                         flush_icache_user_range(vma, page, addr, bytes);
 186                 } else {
 187                         memcpy(buf, maddr + offset, bytes);
 188                         flush_page_to_ram(page);
 189                 }
 190                 kunmap(page);
 191                 page_cache_release(page);
 192                 len -= bytes;
 193                 buf += bytes;
 194                 addr += bytes;
 195         }
 196         up_read(&mm->mmap_sem);
 197         mmput(mm);
 198
 199         return buf - old_buf;
 200 }
 201
 202 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char *dst, int len)
 203 {
 204         int copied = 0;
 205
 206         while (len > 0) {
 207                 char buf[128];
 208                 int this_len, retval;
 209
 210                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 211                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 212                 if (!retval) {
 213                         if (copied)
 214                                 break;
 215                         return -EIO;
 216                 }
 217                 if (copy_to_user(dst, buf, retval))
 218                         return -EFAULT;
 219                 copied += retval;
 220                 src += retval;
 221                 dst += retval;
 222                 len -= retval;
 223         }
 224         return copied;
 225 }
 226
 227 int ptrace_writedata(struct task_struct *tsk, char * src, unsigned long dst, int len)
 228 {
 229         int copied = 0;
 230
 231         while (len > 0) {
 232                 char buf[128];
 233                 int this_len, retval;
 234
 235                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 236                 if (copy_from_user(buf, src, this_len))
 237                         return -EFAULT;
 238                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 239                 if (!retval) {
 240                         if (copied)
 241                                 break;
 242                         return -EIO;
 243                 }
 244                 copied += retval;
 245                 src += retval;
 246                 dst += retval;
 247                 len -= retval;
 248         }
 249         return copied;
 250 }