arch/alpha/kernel/ptrace.c

   1 /* ptrace.c */
   2 /* By Ross Biro 1/23/92 */
   3 /* edited by Linus Torvalds */
   4 /* mangled further by Bob Manson (manson@santafe.edu) */
   5 /* more mutilation by David Mosberger (davidm@azstarnet.com) */
   6
   7 #include <linux/kernel.h>
   8 #include <linux/sched.h>
   9 #include <linux/mm.h>
  10 #include <linux/smp.h>
  11 #include <linux/smp_lock.h>
  12 #include <linux/errno.h>
  13 #include <linux/ptrace.h>
  14 #include <linux/user.h>
  15 #include <linux/slab.h>
  16 #include <linux/security.h>
  17 #include <linux/signal.h>
  18
  19 #include <asm/uaccess.h>
  20 #include <asm/pgtable.h>
  21 #include <asm/system.h>
  22 #include <asm/fpu.h>
  23
  24 #include "proto.h"
  25
  26 #define DEBUG   DBG_MEM
  27 #undef DEBUG
  28
  29 #ifdef DEBUG
  30 enum {
  31         DBG_MEM         = (1<<0),
  32         DBG_BPT         = (1<<1),
  33         DBG_MEM_ALL     = (1<<2)
  34 };
  35 #define DBG(fac,args)   {if ((fac) & DEBUG) printk args;}
  36 #else
  37 #define DBG(fac,args)
  38 #endif
  39
  40 #define BREAKINST       0x00000080      /* call_pal bpt */
  41
  42 /*
  43  * does not yet catch signals sent when the child dies.
  44  * in exit.c or in signal.c.
  45  */
  46
  47 /*
  48  * Processes always block with the following stack-layout:
  49  *
  50  *  +================================+ <---- task + 2*PAGE_SIZE
  51  *  | PALcode saved frame (ps, pc,   | ^
  52  *  | gp, a0, a1, a2)                | |
  53  *  +================================+ | struct pt_regs
  54  *  |                                | |
  55  *  | frame generated by SAVE_ALL    | |
  56  *  |                                | v
  57  *  +================================+
  58  *  |                                | ^
  59  *  | frame saved by do_switch_stack | | struct switch_stack
  60  *  |                                | v
  61  *  +================================+
  62  */
  63
  64 /*
  65  * The following table maps a register index into the stack offset at
  66  * which the register is saved.  Register indices are 0-31 for integer
  67  * regs, 32-63 for fp regs, and 64 for the pc.  Notice that sp and
  68  * zero have no stack-slot and need to be treated specially (see
  69  * get_reg/put_reg below).
  70  */
  71 enum {
  72         REG_R0 = 0, REG_F0 = 32, REG_FPCR = 63, REG_PC = 64
  73 };
  74
  75 static int regoff[] = {
  76         PT_REG(    r0), PT_REG(    r1), PT_REG(    r2), PT_REG(   r3),
  77         PT_REG(    r4), PT_REG(    r5), PT_REG(    r6), PT_REG(   r7),
  78         PT_REG(    r8), SW_REG(    r9), SW_REG(   r10), SW_REG(  r11),
  79         SW_REG(   r12), SW_REG(   r13), SW_REG(   r14), SW_REG(  r15),
  80         PT_REG(   r16), PT_REG(   r17), PT_REG(   r18), PT_REG(  r19),
  81         PT_REG(   r20), PT_REG(   r21), PT_REG(   r22), PT_REG(  r23),
  82         PT_REG(   r24), PT_REG(   r25), PT_REG(   r26), PT_REG(  r27),
  83         PT_REG(   r28), PT_REG(    gp),            -1,             -1,
  84         SW_REG(fp[ 0]), SW_REG(fp[ 1]), SW_REG(fp[ 2]), SW_REG(fp[ 3]),
  85         SW_REG(fp[ 4]), SW_REG(fp[ 5]), SW_REG(fp[ 6]), SW_REG(fp[ 7]),
  86         SW_REG(fp[ 8]), SW_REG(fp[ 9]), SW_REG(fp[10]), SW_REG(fp[11]),
  87         SW_REG(fp[12]), SW_REG(fp[13]), SW_REG(fp[14]), SW_REG(fp[15]),
  88         SW_REG(fp[16]), SW_REG(fp[17]), SW_REG(fp[18]), SW_REG(fp[19]),
  89         SW_REG(fp[20]), SW_REG(fp[21]), SW_REG(fp[22]), SW_REG(fp[23]),
  90         SW_REG(fp[24]), SW_REG(fp[25]), SW_REG(fp[26]), SW_REG(fp[27]),
  91         SW_REG(fp[28]), SW_REG(fp[29]), SW_REG(fp[30]), SW_REG(fp[31]),
  92         PT_REG(    pc)
  93 };
  94
  95 static unsigned long zero;
  96
  97 /*
  98  * Get address of register REGNO in task TASK.
  99  */
 100 static unsigned long *
 101 get_reg_addr(struct task_struct * task, unsigned long regno)
 102 {
 103         unsigned long *addr;
 104
 105         if (regno == 30) {
 106                 addr = &task->thread_info->pcb.usp;
 107         } else if (regno == 65) {
 108                 addr = &task->thread_info->pcb.unique;
 109         } else if (regno == 31 || regno > 65) {
 110                 zero = 0;
 111                 addr = &zero;
 112         } else {
 113                 addr = (void *)task->thread_info + regoff[regno];
 114         }
 115         return addr;
 116 }
 117
 118 /*
 119  * Get contents of register REGNO in task TASK.
 120  */
 121 static unsigned long
 122 get_reg(struct task_struct * task, unsigned long regno)
 123 {
 124         /* Special hack for fpcr -- combine hardware and software bits.  */
 125         if (regno == 63) {
 126                 unsigned long fpcr = *get_reg_addr(task, regno);
 127                 unsigned long swcr
 128                   = task->thread_info->ieee_state & IEEE_SW_MASK;
 129                 swcr = swcr_update_status(swcr, fpcr);
 130                 return fpcr | swcr;
 131         }
 132         return *get_reg_addr(task, regno);
 133 }
 134
 135 /*
 136  * Write contents of register REGNO in task TASK.
 137  */
 138 static int
 139 put_reg(struct task_struct *task, unsigned long regno, unsigned long data)
 140 {
 141         if (regno == 63) {
 142                 task->thread_info->ieee_state
 143                   = ((task->thread_info->ieee_state & ~IEEE_SW_MASK)
 144                      | (data & IEEE_SW_MASK));
 145                 data = (data & FPCR_DYN_MASK) | ieee_swcr_to_fpcr(data);
 146         }
 147         *get_reg_addr(task, regno) = data;
 148         return 0;
 149 }
 150
 151 static inline int
 152 read_int(struct task_struct *task, unsigned long addr, int * data)
 153 {
 154         int copied = access_process_vm(task, addr, data, sizeof(int), 0);
 155         return (copied == sizeof(int)) ? 0 : -EIO;
 156 }
 157
 158 static inline int
 159 write_int(struct task_struct *task, unsigned long addr, int data)
 160 {
 161         int copied = access_process_vm(task, addr, &data, sizeof(int), 1);
 162         return (copied == sizeof(int)) ? 0 : -EIO;
 163 }
 164
 165 /*
 166  * Set breakpoint.
 167  */
 168 int
 169 ptrace_set_bpt(struct task_struct * child)
 170 {
 171         int displ, i, res, reg_b, nsaved = 0;
 172         unsigned int insn, op_code;
 173         unsigned long pc;
 174
 175         pc  = get_reg(child, REG_PC);
 176         res = read_int(child, pc, (int *) &insn);
 177         if (res < 0)
 178                 return res;
 179
 180         op_code = insn >> 26;
 181         if (op_code >= 0x30) {
 182                 /*
 183                  * It's a branch: instead of trying to figure out
 184                  * whether the branch will be taken or not, we'll put
 185                  * a breakpoint at either location.  This is simpler,
 186                  * more reliable, and probably not a whole lot slower
 187                  * than the alternative approach of emulating the
 188                  * branch (emulation can be tricky for fp branches).
 189                  */
 190                 displ = ((s32)(insn << 11)) >> 9;
 191                 child->thread_info->bpt_addr[nsaved++] = pc + 4;
 192                 if (displ)              /* guard against unoptimized code */
 193                         child->thread_info->bpt_addr[nsaved++]
 194                           = pc + 4 + displ;
 195                 DBG(DBG_BPT, ("execing branch\n"));
 196         } else if (op_code == 0x1a) {
 197                 reg_b = (insn >> 16) & 0x1f;
 198                 child->thread_info->bpt_addr[nsaved++] = get_reg(child, reg_b);
 199                 DBG(DBG_BPT, ("execing jump\n"));
 200         } else {
 201                 child->thread_info->bpt_addr[nsaved++] = pc + 4;
 202                 DBG(DBG_BPT, ("execing normal insn\n"));
 203         }
 204
 205         /* install breakpoints: */
 206         for (i = 0; i < nsaved; ++i) {
 207                 res = read_int(child, child->thread_info->bpt_addr[i],
 208                                (int *) &insn);
 209                 if (res < 0)
 210                         return res;
 211                 child->thread_info->bpt_insn[i] = insn;
 212                 DBG(DBG_BPT, ("    -> next_pc=%lx\n",
 213                               child->thread_info->bpt_addr[i]));
 214                 res = write_int(child, child->thread_info->bpt_addr[i],
 215                                 BREAKINST);
 216                 if (res < 0)
 217                         return res;
 218         }
 219         child->thread_info->bpt_nsaved = nsaved;
 220         return 0;
 221 }
 222
 223 /*
 224  * Ensure no single-step breakpoint is pending.  Returns non-zero
 225  * value if child was being single-stepped.
 226  */
 227 int
 228 ptrace_cancel_bpt(struct task_struct * child)
 229 {
 230         int i, nsaved = child->thread_info->bpt_nsaved;
 231
 232         child->thread_info->bpt_nsaved = 0;
 233
 234         if (nsaved > 2) {
 235                 printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
 236                 nsaved = 2;
 237         }
 238
 239         for (i = 0; i < nsaved; ++i) {
 240                 write_int(child, child->thread_info->bpt_addr[i],
 241                           child->thread_info->bpt_insn[i]);
 242         }
 243         return (nsaved != 0);
 244 }
 245
 246 /*
 247  * Called by kernel/ptrace.c when detaching..
 248  *
 249  * Make sure the single step bit is not set.
 250  */
 251 void ptrace_disable(struct task_struct *child)
 252 {
 253         ptrace_cancel_bpt(child);
 254 }
 255
 256 asmlinkage long
 257 do_sys_ptrace(long request, long pid, long addr, long data,
 258               struct pt_regs *regs)
 259 {
 260         struct task_struct *child;
 261         unsigned long tmp;
 262         size_t copied;
 263         long ret;
 264
 265         lock_kernel();
 266         DBG(DBG_MEM, ("request=%ld pid=%ld addr=0x%lx data=0x%lx\n",
 267                       request, pid, addr, data));
 268         ret = -EPERM;
 269         if (request == PTRACE_TRACEME) {
 270                 /* are we already being traced? */
 271                 if (current->ptrace & PT_PTRACED)
 272                         goto out_notsk;
 273                 ret = security_ptrace(current->parent, current);
 274                 if (ret)
 275                         goto out_notsk;
 276                 /* set the ptrace bit in the process ptrace flags. */
 277                 current->ptrace |= PT_PTRACED;
 278                 ret = 0;
 279                 goto out_notsk;
 280         }
 281         if (pid == 1)           /* you may not mess with init */
 282                 goto out_notsk;
 283
 284         ret = -ESRCH;
 285         read_lock(&tasklist_lock);
 286         child = find_task_by_pid(pid);
 287         if (child)
 288                 get_task_struct(child);
 289         read_unlock(&tasklist_lock);
 290         if (!child)
 291                 goto out_notsk;
 292
 293         if (request == PTRACE_ATTACH) {
 294                 ret = ptrace_attach(child);
 295                 goto out;
 296         }
 297
 298         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 299         if (ret < 0)
 300                 goto out;
 301
 302         switch (request) {
 303         /* When I and D space are separate, these will need to be fixed.  */
 304         case PTRACE_PEEKTEXT: /* read word at location addr. */
 305         case PTRACE_PEEKDATA:
 306                 copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 307                 ret = -EIO;
 308                 if (copied != sizeof(tmp))
 309                         break;
 310
 311                 regs->r0 = 0;   /* special return: no errors */
 312                 ret = tmp;
 313                 break;
 314
 315         /* Read register number ADDR. */
 316         case PTRACE_PEEKUSR:
 317                 regs->r0 = 0;   /* special return: no errors */
 318                 ret = get_reg(child, addr);
 319                 DBG(DBG_MEM, ("peek $%ld->%#lx\n", addr, ret));
 320                 break;
 321
 322         /* When I and D space are separate, this will have to be fixed.  */
 323         case PTRACE_POKETEXT: /* write the word at location addr. */
 324         case PTRACE_POKEDATA:
 325                 tmp = data;
 326                 copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 1);
 327                 ret = (copied == sizeof(tmp)) ? 0 : -EIO;
 328                 break;
 329
 330         case PTRACE_POKEUSR: /* write the specified register */
 331                 DBG(DBG_MEM, ("poke $%ld<-%#lx\n", addr, data));
 332                 ret = put_reg(child, addr, data);
 333                 break;
 334
 335         case PTRACE_SYSCALL:
 336                 /* continue and stop at next (return from) syscall */
 337         case PTRACE_CONT:    /* restart after signal. */
 338                 ret = -EIO;
 339                 if (!valid_signal(data))
 340                         break;
 341                 if (request == PTRACE_SYSCALL)
 342                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 343                 else
 344                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 345                 child->exit_code = data;
 346                 /* make sure single-step breakpoint is gone. */
 347                 ptrace_cancel_bpt(child);
 348                 wake_up_process(child);
 349                 ret = 0;
 350                 break;
 351
 352         /*
 353          * Make the child exit.  Best I can do is send it a sigkill.
 354          * perhaps it should be put in the status that it wants to
 355          * exit.
 356          */
 357         case PTRACE_KILL:
 358                 ret = 0;
 359                 if (child->exit_state == EXIT_ZOMBIE)
 360                         break;
 361                 child->exit_code = SIGKILL;
 362                 /* make sure single-step breakpoint is gone. */
 363                 ptrace_cancel_bpt(child);
 364                 wake_up_process(child);
 365                 goto out;
 366
 367         case PTRACE_SINGLESTEP:  /* execute single instruction. */
 368                 ret = -EIO;
 369                 if (!valid_signal(data))
 370                         break;
 371                 /* Mark single stepping.  */
 372                 child->thread_info->bpt_nsaved = -1;
 373                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 374                 child->exit_code = data;
 375                 wake_up_process(child);
 376                 /* give it a chance to run. */
 377                 ret = 0;
 378                 goto out;
 379
 380         case PTRACE_DETACH:      /* detach a process that was attached. */
 381                 ret = ptrace_detach(child, data);
 382                 goto out;
 383
 384         default:
 385                 ret = ptrace_request(child, request, addr, data);
 386                 goto out;
 387         }
 388  out:
 389         put_task_struct(child);
 390  out_notsk:
 391         unlock_kernel();
 392         return ret;
 393 }
 394
 395 asmlinkage void
 396 syscall_trace(void)
 397 {
 398         if (!test_thread_flag(TIF_SYSCALL_TRACE))
 399                 return;
 400         if (!(current->ptrace & PT_PTRACED))
 401                 return;
 402         /* The 0x80 provides a way for the tracing parent to distinguish
 403            between a syscall stop and SIGTRAP delivery */
 404         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
 405                                  ? 0x80 : 0));
 406
 407         /*
 408          * This isn't the same as continuing with a signal, but it will do
 409          * for normal use.  strace only continues with a signal if the
 410          * stopping signal is not SIGTRAP.  -brl
 411          */
 412         if (current->exit_code) {
 413                 send_sig(current->exit_code, current, 1);
 414                 current->exit_code = 0;
 415         }
 416 }