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, long addr, long data)
 150 {
 151         int ret;
 152
 153         switch (request) {
 154         /* Read the word at location addr in the child process */
 155         case PTRACE_PEEKTEXT:
 156         case PTRACE_PEEKDATA:
 157                 ret = generic_ptrace_peekdata(child, addr, data);
 158                 break;
 159
 160         case PTRACE_PEEKUSR:
 161                 ret = ptrace_read_user(child, addr,
 162                                        (unsigned long __user *)data);
 163                 break;
 164
 165         /* Write the word in data at location addr */
 166         case PTRACE_POKETEXT:
 167         case PTRACE_POKEDATA:
 168                 ret = generic_ptrace_pokedata(child, addr, data);
 169                 break;
 170
 171         case PTRACE_POKEUSR:
 172                 ret = ptrace_write_user(child, addr, data);
 173                 break;
 174
 175         case PTRACE_GETREGS:
 176                 ret = ptrace_getregs(child, (void __user *)data);
 177                 break;
 178
 179         case PTRACE_SETREGS:
 180                 ret = ptrace_setregs(child, (const void __user *)data);
 181                 break;
 182
 183         default:
 184                 ret = ptrace_request(child, request, addr, data);
 185                 break;
 186         }
 187
 188         return ret;
 189 }
 190
 191 asmlinkage void syscall_trace(void)
 192 {
 193         if (!test_thread_flag(TIF_SYSCALL_TRACE))
 194                 return;
 195         if (!(current->ptrace & PT_PTRACED))
 196                 return;
 197
 198         /* The 0x80 provides a way for the tracing parent to
 199          * distinguish between a syscall stop and SIGTRAP delivery */
 200         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
 201                                  ? 0x80 : 0));
 202
 203         /*
 204          * this isn't the same as continuing with a signal, but it
 205          * will do for normal use.  strace only continues with a
 206          * signal if the stopping signal is not SIGTRAP.  -brl
 207          */
 208         if (current->exit_code) {
 209                 pr_debug("syscall_trace: sending signal %d to PID %u\n",
 210                          current->exit_code, current->pid);
 211                 send_sig(current->exit_code, current, 1);
 212                 current->exit_code = 0;
 213         }
 214 }
 215
 216 /*
 217  * debug_trampoline() is an assembly stub which will store all user
 218  * registers on the stack and execute a breakpoint instruction.
 219  *
 220  * If we single-step into an exception handler which runs with
 221  * interrupts disabled the whole time so it doesn't have to check for
 222  * pending work, its return address will be modified so that it ends
 223  * up returning to debug_trampoline.
 224  *
 225  * If the exception handler decides to store the user context and
 226  * enable interrupts after all, it will restore the original return
 227  * address and status register value. Before it returns, it will
 228  * notice that TIF_BREAKPOINT is set and execute a breakpoint
 229  * instruction.
 230  */
 231 extern void debug_trampoline(void);
 232
 233 asmlinkage struct pt_regs *do_debug(struct pt_regs *regs)
 234 {
 235         struct thread_info      *ti;
 236         unsigned long           trampoline_addr;
 237         u32                     status;
 238         u32                     ctrl;
 239         int                     code;
 240
 241         status = ocd_read(DS);
 242         ti = current_thread_info();
 243         code = TRAP_BRKPT;
 244
 245         pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n",
 246                         status, regs->pc, regs->sr, ti->flags);
 247
 248         if (!user_mode(regs)) {
 249                 unsigned long   die_val = DIE_BREAKPOINT;
 250
 251                 if (status & (1 << OCD_DS_SSS_BIT))
 252                         die_val = DIE_SSTEP;
 253
 254                 if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP)
 255                                 == NOTIFY_STOP)
 256                         return regs;
 257
 258                 if ((status & (1 << OCD_DS_SWB_BIT))
 259                                 && test_and_clear_ti_thread_flag(
 260                                         ti, TIF_BREAKPOINT)) {
 261                         /*
 262                          * Explicit breakpoint from trampoline or
 263                          * exception/syscall/interrupt handler.
 264                          *
 265                          * The real saved regs are on the stack right
 266                          * after the ones we saved on entry.
 267                          */
 268                         regs++;
 269                         pr_debug("  -> TIF_BREAKPOINT done, adjusted regs:"
 270                                         "PC=0x%08lx SR=0x%08lx\n",
 271                                         regs->pc, regs->sr);
 272                         BUG_ON(!user_mode(regs));
 273
 274                         if (test_thread_flag(TIF_SINGLE_STEP)) {
 275                                 pr_debug("Going to do single step...\n");
 276                                 return regs;
 277                         }
 278
 279                         /*
 280                          * No TIF_SINGLE_STEP means we're done
 281                          * stepping over a syscall. Do the trap now.
 282                          */
 283                         code = TRAP_TRACE;
 284                 } else if ((status & (1 << OCD_DS_SSS_BIT))
 285                                 && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) {
 286
 287                         pr_debug("Stepped into something, "
 288                                         "setting TIF_BREAKPOINT...\n");
 289                         set_ti_thread_flag(ti, TIF_BREAKPOINT);
 290
 291                         /*
 292                          * We stepped into an exception, interrupt or
 293                          * syscall handler. Some exception handlers
 294                          * don't check for pending work, so we need to
 295                          * set up a trampoline just in case.
 296                          *
 297                          * The exception entry code will undo the
 298                          * trampoline stuff if it does a full context
 299                          * save (which also means that it'll check for
 300                          * pending work later.)
 301                          */
 302                         if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) {
 303                                 trampoline_addr
 304                                         = (unsigned long)&debug_trampoline;
 305
 306                                 pr_debug("Setting up trampoline...\n");
 307                                 ti->rar_saved = sysreg_read(RAR_EX);
 308                                 ti->rsr_saved = sysreg_read(RSR_EX);
 309                                 sysreg_write(RAR_EX, trampoline_addr);
 310                                 sysreg_write(RSR_EX, (MODE_EXCEPTION
 311                                                         | SR_EM | SR_GM));
 312                                 BUG_ON(ti->rsr_saved & MODE_MASK);
 313                         }
 314
 315                         /*
 316                          * If we stepped into a system call, we
 317                          * shouldn't do a single step after we return
 318                          * since the return address is right after the
 319                          * "scall" instruction we were told to step
 320                          * over.
 321                          */
 322                         if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) {
 323                                 pr_debug("Supervisor; no single step\n");
 324                                 clear_ti_thread_flag(ti, TIF_SINGLE_STEP);
 325                         }
 326
 327                         ctrl = ocd_read(DC);
 328                         ctrl &= ~(1 << OCD_DC_SS_BIT);
 329                         ocd_write(DC, ctrl);
 330
 331                         return regs;
 332                 } else {
 333                         printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n",
 334                                         status);
 335                         printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags);
 336                         die("Unhandled debug trap in kernel mode",
 337                                         regs, SIGTRAP);
 338                 }
 339         } else if (status & (1 << OCD_DS_SSS_BIT)) {
 340                 /* Single step in user mode */
 341                 code = TRAP_TRACE;
 342
 343                 ctrl = ocd_read(DC);
 344                 ctrl &= ~(1 << OCD_DC_SS_BIT);
 345                 ocd_write(DC, ctrl);
 346         }
 347
 348         pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n",
 349                         code, regs->pc, regs->sr);
 350
 351         clear_thread_flag(TIF_SINGLE_STEP);
 352         _exception(SIGTRAP, regs, code, instruction_pointer(regs));
 353
 354         return regs;
 355 }