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 static void ptrace_single_step(struct task_struct *tsk)
  32 {
  33         pr_debug("ptrace_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 /*
  53  * Called by kernel/ptrace.c when detaching
  54  *
  55  * Make sure any single step bits, etc. are not set
  56  */
  57 void ptrace_disable(struct task_struct *child)
  58 {
  59         clear_tsk_thread_flag(child, TIF_SINGLE_STEP);
  60         clear_tsk_thread_flag(child, TIF_BREAKPOINT);
  61         ocd_disable(child);
  62 }
  63
  64 /*
  65  * Read the word at offset "offset" into the task's "struct user". We
  66  * actually access the pt_regs struct stored on the kernel stack.
  67  */
  68 static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
  69                             unsigned long __user *data)
  70 {
  71         unsigned long *regs;
  72         unsigned long value;
  73
  74         if (offset & 3 || offset >= sizeof(struct user)) {
  75                 printk("ptrace_read_user: invalid offset 0x%08lx\n", offset);
  76                 return -EIO;
  77         }
  78
  79         regs = (unsigned long *)get_user_regs(tsk);
  80
  81         value = 0;
  82         if (offset < sizeof(struct pt_regs))
  83                 value = regs[offset / sizeof(regs[0])];
  84
  85         pr_debug("ptrace_read_user(%s[%u], %#lx, %p) -> %#lx\n",
  86                  tsk->comm, tsk->pid, offset, data, value);
  87
  88         return put_user(value, data);
  89 }
  90
  91 /*
  92  * Write the word "value" to offset "offset" into the task's "struct
  93  * user". We actually access the pt_regs struct stored on the kernel
  94  * stack.
  95  */
  96 static int ptrace_write_user(struct task_struct *tsk, unsigned long offset,
  97                              unsigned long value)
  98 {
  99         unsigned long *regs;
 100
 101         pr_debug("ptrace_write_user(%s[%u], %#lx, %#lx)\n",
 102                         tsk->comm, tsk->pid, offset, value);
 103
 104         if (offset & 3 || offset >= sizeof(struct user)) {
 105                 pr_debug("  invalid offset 0x%08lx\n", offset);
 106                 return -EIO;
 107         }
 108
 109         if (offset >= sizeof(struct pt_regs))
 110                 return 0;
 111
 112         regs = (unsigned long *)get_user_regs(tsk);
 113         regs[offset / sizeof(regs[0])] = value;
 114
 115         return 0;
 116 }
 117
 118 static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
 119 {
 120         struct pt_regs *regs = get_user_regs(tsk);
 121
 122         return copy_to_user(uregs, regs, sizeof(*regs)) ? -EFAULT : 0;
 123 }
 124
 125 static int ptrace_setregs(struct task_struct *tsk, const void __user *uregs)
 126 {
 127         struct pt_regs newregs;
 128         int ret;
 129
 130         ret = -EFAULT;
 131         if (copy_from_user(&newregs, uregs, sizeof(newregs)) == 0) {
 132                 struct pt_regs *regs = get_user_regs(tsk);
 133
 134                 ret = -EINVAL;
 135                 if (valid_user_regs(&newregs)) {
 136                         *regs = newregs;
 137                         ret = 0;
 138                 }
 139         }
 140
 141         return ret;
 142 }
 143
 144 long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 145 {
 146         int ret;
 147
 148         switch (request) {
 149         /* Read the word at location addr in the child process */
 150         case PTRACE_PEEKTEXT:
 151         case PTRACE_PEEKDATA:
 152                 ret = generic_ptrace_peekdata(child, addr, data);
 153                 break;
 154
 155         case PTRACE_PEEKUSR:
 156                 ret = ptrace_read_user(child, addr,
 157                                        (unsigned long __user *)data);
 158                 break;
 159
 160         /* Write the word in data at location addr */
 161         case PTRACE_POKETEXT:
 162         case PTRACE_POKEDATA:
 163                 ret = generic_ptrace_pokedata(child, addr, data);
 164                 break;
 165
 166         case PTRACE_POKEUSR:
 167                 ret = ptrace_write_user(child, addr, data);
 168                 break;
 169
 170         /* continue and stop at next (return from) syscall */
 171         case PTRACE_SYSCALL:
 172         /* restart after signal */
 173         case PTRACE_CONT:
 174                 ret = -EIO;
 175                 if (!valid_signal(data))
 176                         break;
 177                 if (request == PTRACE_SYSCALL)
 178                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 179                 else
 180                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 181                 child->exit_code = data;
 182                 /* XXX: Are we sure no breakpoints are active here? */
 183                 wake_up_process(child);
 184                 ret = 0;
 185                 break;
 186
 187         /*
 188          * Make the child exit. Best I can do is send it a
 189          * SIGKILL. Perhaps it should be put in the status that it
 190          * wants to exit.
 191          */
 192         case PTRACE_KILL:
 193                 ret = 0;
 194                 if (child->exit_state == EXIT_ZOMBIE)
 195                         break;
 196                 child->exit_code = SIGKILL;
 197                 wake_up_process(child);
 198                 break;
 199
 200         /*
 201          * execute single instruction.
 202          */
 203         case PTRACE_SINGLESTEP:
 204                 ret = -EIO;
 205                 if (!valid_signal(data))
 206                         break;
 207                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 208                 ptrace_single_step(child);
 209                 child->exit_code = data;
 210                 wake_up_process(child);
 211                 ret = 0;
 212                 break;
 213
 214         case PTRACE_GETREGS:
 215                 ret = ptrace_getregs(child, (void __user *)data);
 216                 break;
 217
 218         case PTRACE_SETREGS:
 219                 ret = ptrace_setregs(child, (const void __user *)data);
 220                 break;
 221
 222         default:
 223                 ret = ptrace_request(child, request, addr, data);
 224                 break;
 225         }
 226
 227         return ret;
 228 }
 229
 230 asmlinkage void syscall_trace(void)
 231 {
 232         if (!test_thread_flag(TIF_SYSCALL_TRACE))
 233                 return;
 234         if (!(current->ptrace & PT_PTRACED))
 235                 return;
 236
 237         /* The 0x80 provides a way for the tracing parent to
 238          * distinguish between a syscall stop and SIGTRAP delivery */
 239         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
 240                                  ? 0x80 : 0));
 241
 242         /*
 243          * this isn't the same as continuing with a signal, but it
 244          * will do for normal use.  strace only continues with a
 245          * signal if the stopping signal is not SIGTRAP.  -brl
 246          */
 247         if (current->exit_code) {
 248                 pr_debug("syscall_trace: sending signal %d to PID %u\n",
 249                          current->exit_code, current->pid);
 250                 send_sig(current->exit_code, current, 1);
 251                 current->exit_code = 0;
 252         }
 253 }
 254
 255 /*
 256  * debug_trampoline() is an assembly stub which will store all user
 257  * registers on the stack and execute a breakpoint instruction.
 258  *
 259  * If we single-step into an exception handler which runs with
 260  * interrupts disabled the whole time so it doesn't have to check for
 261  * pending work, its return address will be modified so that it ends
 262  * up returning to debug_trampoline.
 263  *
 264  * If the exception handler decides to store the user context and
 265  * enable interrupts after all, it will restore the original return
 266  * address and status register value. Before it returns, it will
 267  * notice that TIF_BREAKPOINT is set and execute a breakpoint
 268  * instruction.
 269  */
 270 extern void debug_trampoline(void);
 271
 272 asmlinkage struct pt_regs *do_debug(struct pt_regs *regs)
 273 {
 274         struct thread_info      *ti;
 275         unsigned long           trampoline_addr;
 276         u32                     status;
 277         u32                     ctrl;
 278         int                     code;
 279
 280         status = ocd_read(DS);
 281         ti = current_thread_info();
 282         code = TRAP_BRKPT;
 283
 284         pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n",
 285                         status, regs->pc, regs->sr, ti->flags);
 286
 287         if (!user_mode(regs)) {
 288                 unsigned long   die_val = DIE_BREAKPOINT;
 289
 290                 if (status & (1 << OCD_DS_SSS_BIT))
 291                         die_val = DIE_SSTEP;
 292
 293                 if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP)
 294                                 == NOTIFY_STOP)
 295                         return regs;
 296
 297                 if ((status & (1 << OCD_DS_SWB_BIT))
 298                                 && test_and_clear_ti_thread_flag(
 299                                         ti, TIF_BREAKPOINT)) {
 300                         /*
 301                          * Explicit breakpoint from trampoline or
 302                          * exception/syscall/interrupt handler.
 303                          *
 304                          * The real saved regs are on the stack right
 305                          * after the ones we saved on entry.
 306                          */
 307                         regs++;
 308                         pr_debug("  -> TIF_BREAKPOINT done, adjusted regs:"
 309                                         "PC=0x%08lx SR=0x%08lx\n",
 310                                         regs->pc, regs->sr);
 311                         BUG_ON(!user_mode(regs));
 312
 313                         if (test_thread_flag(TIF_SINGLE_STEP)) {
 314                                 pr_debug("Going to do single step...\n");
 315                                 return regs;
 316                         }
 317
 318                         /*
 319                          * No TIF_SINGLE_STEP means we're done
 320                          * stepping over a syscall. Do the trap now.
 321                          */
 322                         code = TRAP_TRACE;
 323                 } else if ((status & (1 << OCD_DS_SSS_BIT))
 324                                 && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) {
 325
 326                         pr_debug("Stepped into something, "
 327                                         "setting TIF_BREAKPOINT...\n");
 328                         set_ti_thread_flag(ti, TIF_BREAKPOINT);
 329
 330                         /*
 331                          * We stepped into an exception, interrupt or
 332                          * syscall handler. Some exception handlers
 333                          * don't check for pending work, so we need to
 334                          * set up a trampoline just in case.
 335                          *
 336                          * The exception entry code will undo the
 337                          * trampoline stuff if it does a full context
 338                          * save (which also means that it'll check for
 339                          * pending work later.)
 340                          */
 341                         if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) {
 342                                 trampoline_addr
 343                                         = (unsigned long)&debug_trampoline;
 344
 345                                 pr_debug("Setting up trampoline...\n");
 346                                 ti->rar_saved = sysreg_read(RAR_EX);
 347                                 ti->rsr_saved = sysreg_read(RSR_EX);
 348                                 sysreg_write(RAR_EX, trampoline_addr);
 349                                 sysreg_write(RSR_EX, (MODE_EXCEPTION
 350                                                         | SR_EM | SR_GM));
 351                                 BUG_ON(ti->rsr_saved & MODE_MASK);
 352                         }
 353
 354                         /*
 355                          * If we stepped into a system call, we
 356                          * shouldn't do a single step after we return
 357                          * since the return address is right after the
 358                          * "scall" instruction we were told to step
 359                          * over.
 360                          */
 361                         if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) {
 362                                 pr_debug("Supervisor; no single step\n");
 363                                 clear_ti_thread_flag(ti, TIF_SINGLE_STEP);
 364                         }
 365
 366                         ctrl = ocd_read(DC);
 367                         ctrl &= ~(1 << OCD_DC_SS_BIT);
 368                         ocd_write(DC, ctrl);
 369
 370                         return regs;
 371                 } else {
 372                         printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n",
 373                                         status);
 374                         printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags);
 375                         die("Unhandled debug trap in kernel mode",
 376                                         regs, SIGTRAP);
 377                 }
 378         } else if (status & (1 << OCD_DS_SSS_BIT)) {
 379                 /* Single step in user mode */
 380                 code = TRAP_TRACE;
 381
 382                 ctrl = ocd_read(DC);
 383                 ctrl &= ~(1 << OCD_DC_SS_BIT);
 384                 ocd_write(DC, ctrl);
 385         }
 386
 387         pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n",
 388                         code, regs->pc, regs->sr);
 389
 390         clear_thread_flag(TIF_SINGLE_STEP);
 391         _exception(SIGTRAP, regs, code, instruction_pointer(regs));
 392
 393         return regs;
 394 }