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