release/src-rt-6.x.4708/linux/linux-2.6.36/arch/avr32/kernel/ptrace.c

   1 /*
   2  * Copyright (C) 2004-2006 Atmel Corporation
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8 #undef DEBUG
   9 #include <linux/kernel.h>
  10 #include <linux/sched.h>
  11 #include <linux/mm.h>
  12 #include <linux/ptrace.h>
  13 #include <linux/errno.h>
  14 #include <linux/user.h>
  15 #include <linux/security.h>
  16 #include <linux/unistd.h>
  17 #include <linux/notifier.h>
  18
  19 #include <asm/traps.h>
  20 #include <asm/uaccess.h>
  21 #include <asm/ocd.h>
  22 #include <asm/mmu_context.h>
  23 #include <linux/kdebug.h>
  24
  25 static struct pt_regs *get_user_regs(struct task_struct *tsk)
  26 {
  27         return (struct pt_regs *)((unsigned long)task_stack_page(tsk) +
  28                                   THREAD_SIZE - sizeof(struct pt_regs));
  29 }
  30
  31 void user_enable_single_step(struct task_struct *tsk)
  32 {
  33         pr_debug("user_enable_single_step: pid=%u, PC=0x%08lx, SR=0x%08lx\n",
  34                  tsk->pid, task_pt_regs(tsk)->pc, task_pt_regs(tsk)->sr);
  35
  36         /*
  37          * We can't schedule in Debug mode, so when TIF_BREAKPOINT is
  38          * set, the system call or exception handler will do a
  39          * breakpoint to enter monitor mode before returning to
  40          * userspace.
  41          *
  42          * The monitor code will then notice that TIF_SINGLE_STEP is
  43          * set and return to userspace with single stepping enabled.
  44          * The CPU will then enter monitor mode again after exactly
  45          * one instruction has been executed, and the monitor code
  46          * will then send a SIGTRAP to the process.
  47          */
  48         set_tsk_thread_flag(tsk, TIF_BREAKPOINT);
  49         set_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
  50 }
  51
  52 void user_disable_single_step(struct task_struct *child)
  53 {
  54 }
  55
  56 /*
  57  * Called by kernel/ptrace.c when detaching
  58  *
  59  * Make sure any single step bits, etc. are not set
  60  */
  61 void ptrace_disable(struct task_struct *child)
  62 {
  63         clear_tsk_thread_flag(child, TIF_SINGLE_STEP);
  64         clear_tsk_thread_flag(child, TIF_BREAKPOINT);
  65         ocd_disable(child);
  66 }
  67
  68 /*
  69  * Read the word at offset "offset" into the task's "struct user". We
  70  * actually access the pt_regs struct stored on the kernel stack.
  71  */
  72 static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
  73                             unsigned long __user *data)
  74 {
  75         unsigned long *regs;
  76         unsigned long value;
  77
  78         if (offset & 3 || offset >= sizeof(struct user)) {
  79                 printk("ptrace_read_user: invalid offset 0x%08lx\n", offset);
  80                 return -EIO;
  81         }
  82
  83         regs = (unsigned long *)get_user_regs(tsk);
  84
  85         value = 0;
  86         if (offset < sizeof(struct pt_regs))
  87                 value = regs[offset / sizeof(regs[0])];
  88
  89         pr_debug("ptrace_read_user(%s[%u], %#lx, %p) -> %#lx\n",
  90                  tsk->comm, tsk->pid, offset, data, value);
  91
  92         return put_user(value, data);
  93 }
  94
  95 /*
  96  * Write the word "value" to offset "offset" into the task's "struct
  97  * user". We actually access the pt_regs struct stored on the kernel
  98  * stack.
  99  */
 100 static int ptrace_write_user(struct task_struct *tsk, unsigned long offset,
 101                              unsigned long value)
 102 {
 103         unsigned long *regs;
 104
 105         pr_debug("ptrace_write_user(%s[%u], %#lx, %#lx)\n",
 106                         tsk->comm, tsk->pid, offset, value);
 107
 108         if (offset & 3 || offset >= sizeof(struct user)) {
 109                 pr_debug("  invalid offset 0x%08lx\n", offset);
 110                 return -EIO;
 111         }
 112
 113         if (offset >= sizeof(struct pt_regs))
 114                 return 0;
 115
 116         regs = (unsigned long *)get_user_regs(tsk);
 117         regs[offset / sizeof(regs[0])] = value;
 118
 119         return 0;
 120 }
 121
 122 static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
 123 {
 124         struct pt_regs *regs = get_user_regs(tsk);
 125
 126         return copy_to_user(uregs, regs, sizeof(*regs)) ? -EFAULT : 0;
 127 }
 128
 129 static int ptrace_setregs(struct task_struct *tsk, const void __user *uregs)
 130 {
 131         struct pt_regs newregs;
 132         int ret;
 133
 134         ret = -EFAULT;
 135         if (copy_from_user(&newregs, uregs, sizeof(newregs)) == 0) {
 136                 struct pt_regs *regs = get_user_regs(tsk);
 137
 138                 ret = -EINVAL;
 139                 if (valid_user_regs(&newregs)) {
 140                         *regs = newregs;
 141                         ret = 0;
 142                 }
 143         }
 144
 145         return ret;
 146 }
 147
 148 long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 149 {
 150         int ret;
 151
 152         switch (request) {
 153         /* Read the word at location addr in the child process */
 154         case PTRACE_PEEKTEXT:
 155         case PTRACE_PEEKDATA:
 156                 ret = generic_ptrace_peekdata(child, addr, data);
 157                 break;
 158
 159         case PTRACE_PEEKUSR:
 160                 ret = ptrace_read_user(child, addr,
 161                                        (unsigned long __user *)data);
 162                 break;
 163
 164         /* Write the word in data at location addr */
 165         case PTRACE_POKETEXT:
 166         case PTRACE_POKEDATA:
 167                 ret = generic_ptrace_pokedata(child, addr, data);
 168                 break;
 169
 170         case PTRACE_POKEUSR:
 171                 ret = ptrace_write_user(child, addr, data);
 172                 break;
 173
 174         case PTRACE_GETREGS:
 175                 ret = ptrace_getregs(child, (void __user *)data);
 176                 break;
 177
 178         case PTRACE_SETREGS:
 179                 ret = ptrace_setregs(child, (const void __user *)data);
 180                 break;
 181
 182         default:
 183                 ret = ptrace_request(child, request, addr, data);
 184                 break;
 185         }
 186
 187         return ret;
 188 }
 189
 190 asmlinkage void syscall_trace(void)
 191 {
 192         if (!test_thread_flag(TIF_SYSCALL_TRACE))
 193                 return;
 194         if (!(current->ptrace & PT_PTRACED))
 195                 return;
 196
 197         /* The 0x80 provides a way for the tracing parent to
 198          * distinguish between a syscall stop and SIGTRAP delivery */
 199         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
 200                                  ? 0x80 : 0));
 201
 202         /*
 203          * this isn't the same as continuing with a signal, but it
 204          * will do for normal use.  strace only continues with a
 205          * signal if the stopping signal is not SIGTRAP.  -brl
 206          */
 207         if (current->exit_code) {
 208                 pr_debug("syscall_trace: sending signal %d to PID %u\n",
 209                          current->exit_code, current->pid);
 210                 send_sig(current->exit_code, current, 1);
 211                 current->exit_code = 0;
 212         }
 213 }
 214
 215 /*
 216  * debug_trampoline() is an assembly stub which will store all user
 217  * registers on the stack and execute a breakpoint instruction.
 218  *
 219  * If we single-step into an exception handler which runs with
 220  * interrupts disabled the whole time so it doesn't have to check for
 221  * pending work, its return address will be modified so that it ends
 222  * up returning to debug_trampoline.
 223  *
 224  * If the exception handler decides to store the user context and
 225  * enable interrupts after all, it will restore the original return
 226  * address and status register value. Before it returns, it will
 227  * notice that TIF_BREAKPOINT is set and execute a breakpoint
 228  * instruction.
 229  */
 230 extern void debug_trampoline(void);
 231
 232 asmlinkage struct pt_regs *do_debug(struct pt_regs *regs)
 233 {
 234         struct thread_info      *ti;
 235         unsigned long           trampoline_addr;
 236         u32                     status;
 237         u32                     ctrl;
 238         int                     code;
 239
 240         status = ocd_read(DS);
 241         ti = current_thread_info();
 242         code = TRAP_BRKPT;
 243
 244         pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n",
 245                         status, regs->pc, regs->sr, ti->flags);
 246
 247         if (!user_mode(regs)) {
 248                 unsigned long   die_val = DIE_BREAKPOINT;
 249
 250                 if (status & (1 << OCD_DS_SSS_BIT))
 251                         die_val = DIE_SSTEP;
 252
 253                 if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP)
 254                                 == NOTIFY_STOP)
 255                         return regs;
 256
 257                 if ((status & (1 << OCD_DS_SWB_BIT))
 258                                 && test_and_clear_ti_thread_flag(
 259                                         ti, TIF_BREAKPOINT)) {
 260                         /*
 261                          * Explicit breakpoint from trampoline or
 262                          * exception/syscall/interrupt handler.
 263                          *
 264                          * The real saved regs are on the stack right
 265                          * after the ones we saved on entry.
 266                          */
 267                         regs++;
 268                         pr_debug("  -> TIF_BREAKPOINT done, adjusted regs:"
 269                                         "PC=0x%08lx SR=0x%08lx\n",
 270                                         regs->pc, regs->sr);
 271                         BUG_ON(!user_mode(regs));
 272
 273                         if (test_thread_flag(TIF_SINGLE_STEP)) {
 274                                 pr_debug("Going to do single step...\n");
 275                                 return regs;
 276                         }
 277
 278                         /*
 279                          * No TIF_SINGLE_STEP means we're done
 280                          * stepping over a syscall. Do the trap now.
 281                          */
 282                         code = TRAP_TRACE;
 283                 } else if ((status & (1 << OCD_DS_SSS_BIT))
 284                                 && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) {
 285
 286                         pr_debug("Stepped into something, "
 287                                         "setting TIF_BREAKPOINT...\n");
 288                         set_ti_thread_flag(ti, TIF_BREAKPOINT);
 289
 290                         /*
 291                          * We stepped into an exception, interrupt or
 292                          * syscall handler. Some exception handlers
 293                          * don't check for pending work, so we need to
 294                          * set up a trampoline just in case.
 295                          *
 296                          * The exception entry code will undo the
 297                          * trampoline stuff if it does a full context
 298                          * save (which also means that it'll check for
 299                          * pending work later.)
 300                          */
 301                         if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) {
 302                                 trampoline_addr
 303                                         = (unsigned long)&debug_trampoline;
 304
 305                                 pr_debug("Setting up trampoline...\n");
 306                                 ti->rar_saved = sysreg_read(RAR_EX);
 307                                 ti->rsr_saved = sysreg_read(RSR_EX);
 308                                 sysreg_write(RAR_EX, trampoline_addr);
 309                                 sysreg_write(RSR_EX, (MODE_EXCEPTION
 310                                                         | SR_EM | SR_GM));
 311                                 BUG_ON(ti->rsr_saved & MODE_MASK);
 312                         }
 313
 314                         /*
 315                          * If we stepped into a system call, we
 316                          * shouldn't do a single step after we return
 317                          * since the return address is right after the
 318                          * "scall" instruction we were told to step
 319                          * over.
 320                          */
 321                         if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) {
 322                                 pr_debug("Supervisor; no single step\n");
 323                                 clear_ti_thread_flag(ti, TIF_SINGLE_STEP);
 324                         }
 325
 326                         ctrl = ocd_read(DC);
 327                         ctrl &= ~(1 << OCD_DC_SS_BIT);
 328                         ocd_write(DC, ctrl);
 329
 330                         return regs;
 331                 } else {
 332                         printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n",
 333                                         status);
 334                         printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags);
 335                         die("Unhandled debug trap in kernel mode",
 336                                         regs, SIGTRAP);
 337                 }
 338         } else if (status & (1 << OCD_DS_SSS_BIT)) {
 339                 /* Single step in user mode */
 340                 code = TRAP_TRACE;
 341
 342                 ctrl = ocd_read(DC);
 343                 ctrl &= ~(1 << OCD_DC_SS_BIT);
 344                 ocd_write(DC, ctrl);
 345         }
 346
 347         pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n",
 348                         code, regs->pc, regs->sr);
 349
 350         clear_thread_flag(TIF_SINGLE_STEP);
 351         _exception(SIGTRAP, regs, code, instruction_pointer(regs));
 352
 353         return regs;
 354 }