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/malloc.h>
  16
  17 #include <asm/uaccess.h>
  18 #include <asm/pgtable.h>
  19 #include <asm/system.h>
  20
  21 #include "proto.h"
  22
  23 #define DEBUG   DBG_MEM
  24 #undef DEBUG
  25
  26 #ifdef DEBUG
  27 enum {
  28         DBG_MEM         = (1<<0),
  29         DBG_BPT         = (1<<1),
  30         DBG_MEM_ALL     = (1<<2)
  31 };
  32 #define DBG(fac,args)   {if ((fac) & DEBUG) printk args;}
  33 #else
  34 #define DBG(fac,args)
  35 #endif
  36
  37 #define BREAKINST       0x00000080      /* call_pal bpt */
  38
  39 /*
  40  * does not yet catch signals sent when the child dies.
  41  * in exit.c or in signal.c.
  42  */
  43
  44 /*
  45  * Processes always block with the following stack-layout:
  46  *
  47  *  +================================+ <---- task + 2*PAGE_SIZE
  48  *  | PALcode saved frame (ps, pc,   | ^
  49  *  | gp, a0, a1, a2)                | |
  50  *  +================================+ | struct pt_regs
  51  *  |                                | |
  52  *  | frame generated by SAVE_ALL    | |
  53  *  |                                | v
  54  *  +================================+
  55  *  |                                | ^
  56  *  | frame saved by do_switch_stack | | struct switch_stack
  57  *  |                                | v
  58  *  +================================+
  59  */
  60 #define PT_REG(reg)     (PAGE_SIZE*2 - sizeof(struct pt_regs)           \
  61                          + (long)&((struct pt_regs *)0)->reg)
  62
  63 #define SW_REG(reg)     (PAGE_SIZE*2 - sizeof(struct pt_regs)           \
  64                          - sizeof(struct switch_stack)                  \
  65                          + (long)&((struct switch_stack *)0)->reg)
  66
  67 /*
  68  * The following table maps a register index into the stack offset at
  69  * which the register is saved.  Register indices are 0-31 for integer
  70  * regs, 32-63 for fp regs, and 64 for the pc.  Notice that sp and
  71  * zero have no stack-slot and need to be treated specially (see
  72  * get_reg/put_reg below).
  73  */
  74 enum {
  75         REG_R0 = 0, REG_F0 = 32, REG_FPCR = 63, REG_PC = 64
  76 };
  77
  78 static int regoff[] = {
  79         PT_REG(    r0), PT_REG(    r1), PT_REG(    r2), PT_REG(   r3),
  80         PT_REG(    r4), PT_REG(    r5), PT_REG(    r6), PT_REG(   r7),
  81         PT_REG(    r8), SW_REG(    r9), SW_REG(   r10), SW_REG(  r11),
  82         SW_REG(   r12), SW_REG(   r13), SW_REG(   r14), SW_REG(  r15),
  83         PT_REG(   r16), PT_REG(   r17), PT_REG(   r18), PT_REG(  r19),
  84         PT_REG(   r20), PT_REG(   r21), PT_REG(   r22), PT_REG(  r23),
  85         PT_REG(   r24), PT_REG(   r25), PT_REG(   r26), PT_REG(  r27),
  86         PT_REG(   r28), PT_REG(    gp),            -1,             -1,
  87         SW_REG(fp[ 0]), SW_REG(fp[ 1]), SW_REG(fp[ 2]), SW_REG(fp[ 3]),
  88         SW_REG(fp[ 4]), SW_REG(fp[ 5]), SW_REG(fp[ 6]), SW_REG(fp[ 7]),
  89         SW_REG(fp[ 8]), SW_REG(fp[ 9]), SW_REG(fp[10]), SW_REG(fp[11]),
  90         SW_REG(fp[12]), SW_REG(fp[13]), SW_REG(fp[14]), SW_REG(fp[15]),
  91         SW_REG(fp[16]), SW_REG(fp[17]), SW_REG(fp[18]), SW_REG(fp[19]),
  92         SW_REG(fp[20]), SW_REG(fp[21]), SW_REG(fp[22]), SW_REG(fp[23]),
  93         SW_REG(fp[24]), SW_REG(fp[25]), SW_REG(fp[26]), SW_REG(fp[27]),
  94         SW_REG(fp[28]), SW_REG(fp[29]), SW_REG(fp[30]), SW_REG(fp[31]),
  95         PT_REG(    pc)
  96 };
  97
  98 static long zero;
  99
 100 /*
 101  * Get address of register REGNO in task TASK.
 102  */
 103 static long *
 104 get_reg_addr(struct task_struct * task, unsigned long regno)
 105 {
 106         long *addr;
 107
 108         if (regno == 30) {
 109                 addr = &task->thread.usp;
 110         } else if (regno == 31 || regno > 64) {
 111                 zero = 0;
 112                 addr = &zero;
 113         } else {
 114                 addr = (long *)((long)task + regoff[regno]);
 115         }
 116         return addr;
 117 }
 118
 119 /*
 120  * Get contents of register REGNO in task TASK.
 121  */
 122 static inline long
 123 get_reg(struct task_struct * task, unsigned long regno)
 124 {
 125         return *get_reg_addr(task, regno);
 126 }
 127
 128 /*
 129  * Write contents of register REGNO in task TASK.
 130  */
 131 static inline int
 132 put_reg(struct task_struct *task, unsigned long regno, long data)
 133 {
 134         *get_reg_addr(task, regno) = data;
 135         return 0;
 136 }
 137
 138 static inline int
 139 read_int(struct task_struct *task, unsigned long addr, int * data)
 140 {
 141         int copied = access_process_vm(task, addr, data, sizeof(int), 0);
 142         return (copied == sizeof(int)) ? 0 : -EIO;
 143 }
 144
 145 static inline int
 146 write_int(struct task_struct *task, unsigned long addr, int data)
 147 {
 148         int copied = access_process_vm(task, addr, &data, sizeof(int), 1);
 149         return (copied == sizeof(int)) ? 0 : -EIO;
 150 }
 151
 152 /*
 153  * Set breakpoint.
 154  */
 155 int
 156 ptrace_set_bpt(struct task_struct * child)
 157 {
 158         int displ, i, res, reg_b, nsaved = 0;
 159         u32 insn, op_code;
 160         unsigned long pc;
 161
 162         pc  = get_reg(child, REG_PC);
 163         res = read_int(child, pc, &insn);
 164         if (res < 0)
 165                 return res;
 166
 167         op_code = insn >> 26;
 168         if (op_code >= 0x30) {
 169                 /*
 170                  * It's a branch: instead of trying to figure out
 171                  * whether the branch will be taken or not, we'll put
 172                  * a breakpoint at either location.  This is simpler,
 173                  * more reliable, and probably not a whole lot slower
 174                  * than the alternative approach of emulating the
 175                  * branch (emulation can be tricky for fp branches).
 176                  */
 177                 displ = ((s32)(insn << 11)) >> 9;
 178                 child->thread.bpt_addr[nsaved++] = pc + 4;
 179                 if (displ)              /* guard against unoptimized code */
 180                         child->thread.bpt_addr[nsaved++] = pc + 4 + displ;
 181                 DBG(DBG_BPT, ("execing branch\n"));
 182         } else if (op_code == 0x1a) {
 183                 reg_b = (insn >> 16) & 0x1f;
 184                 child->thread.bpt_addr[nsaved++] = get_reg(child, reg_b);
 185                 DBG(DBG_BPT, ("execing jump\n"));
 186         } else {
 187                 child->thread.bpt_addr[nsaved++] = pc + 4;
 188                 DBG(DBG_BPT, ("execing normal insn\n"));
 189         }
 190
 191         /* install breakpoints: */
 192         for (i = 0; i < nsaved; ++i) {
 193                 res = read_int(child, child->thread.bpt_addr[i], &insn);
 194                 if (res < 0)
 195                         return res;
 196                 child->thread.bpt_insn[i] = insn;
 197                 DBG(DBG_BPT, ("    -> next_pc=%lx\n", child->thread.bpt_addr[i]));
 198                 res = write_int(child, child->thread.bpt_addr[i], BREAKINST);
 199                 if (res < 0)
 200                         return res;
 201         }
 202         child->thread.bpt_nsaved = nsaved;
 203         return 0;
 204 }
 205
 206 /*
 207  * Ensure no single-step breakpoint is pending.  Returns non-zero
 208  * value if child was being single-stepped.
 209  */
 210 int
 211 ptrace_cancel_bpt(struct task_struct * child)
 212 {
 213         int i, nsaved = child->thread.bpt_nsaved;
 214
 215         child->thread.bpt_nsaved = 0;
 216
 217         if (nsaved > 2) {
 218                 printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
 219                 nsaved = 2;
 220         }
 221
 222         for (i = 0; i < nsaved; ++i) {
 223                 write_int(child, child->thread.bpt_addr[i],
 224                           child->thread.bpt_insn[i]);
 225         }
 226         return (nsaved != 0);
 227 }
 228
 229 asmlinkage long
 230 sys_ptrace(long request, long pid, long addr, long data,
 231            int a4, int a5, struct pt_regs regs)
 232 {
 233         struct task_struct *child;
 234         long ret;
 235
 236         lock_kernel();
 237         DBG(DBG_MEM, ("request=%ld pid=%ld addr=0x%lx data=0x%lx\n",
 238                       request, pid, addr, data));
 239         ret = -EPERM;
 240         if (request == PTRACE_TRACEME) {
 241                 /* are we already being traced? */
 242                 if (current->flags & PF_PTRACED)
 243                         goto out;
 244                 /* set the ptrace bit in the process flags. */
 245                 current->flags |= PF_PTRACED;
 246                 ret = 0;
 247                 goto out;
 248         }
 249         if (pid == 1)           /* you may not mess with init */
 250                 goto out;
 251         ret = -ESRCH;
 252         if (!(child = find_task_by_pid(pid)))
 253                 goto out;
 254         if (request == PTRACE_ATTACH) {
 255                 ret = -EPERM;
 256                 if (child == current)
 257                         goto out;
 258                 if ((!child->dumpable ||
 259                      (current->uid != child->euid) ||
 260                      (current->uid != child->suid) ||
 261                      (current->uid != child->uid) ||
 262                      (current->gid != child->egid) ||
 263                      (current->gid != child->sgid) ||
 264                      (current->gid != child->gid) ||
 265                      (!cap_issubset(child->cap_permitted, current->cap_permitted)))
 266                     && !capable(CAP_SYS_PTRACE))
 267                         goto out;
 268                 /* the same process cannot be attached many times */
 269                 if (child->flags & PF_PTRACED)
 270                         goto out;
 271                 child->flags |= PF_PTRACED;
 272                 if (child->p_pptr != current) {
 273                         REMOVE_LINKS(child);
 274                         child->p_pptr = current;
 275                         SET_LINKS(child);
 276                 }
 277                 send_sig(SIGSTOP, child, 1);
 278                 ret = 0;
 279                 goto out;
 280         }
 281         ret = -ESRCH;
 282         if (!(child->flags & PF_PTRACED)) {
 283                 DBG(DBG_MEM, ("child not traced\n"));
 284                 goto out;
 285         }
 286         if (child->state != TASK_STOPPED) {
 287                 DBG(DBG_MEM, ("child process not stopped\n"));
 288                 if (request != PTRACE_KILL)
 289                         goto out;
 290         }
 291         if (child->p_pptr != current) {
 292                 DBG(DBG_MEM, ("child not parent of this process\n"));
 293                 goto out;
 294         }
 295
 296         switch (request) {
 297         /* When I and D space are separate, these will need to be fixed.  */
 298         case PTRACE_PEEKTEXT: /* read word at location addr. */
 299         case PTRACE_PEEKDATA: {
 300                 unsigned long tmp;
 301                 int copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 302                 ret = -EIO;
 303                 if (copied != sizeof(tmp))
 304                         goto out;
 305
 306                 regs.r0 = 0;    /* special return: no errors */
 307                 ret = tmp;
 308                 goto out;
 309         }
 310
 311         /* Read register number ADDR. */
 312         case PTRACE_PEEKUSR:
 313                 regs.r0 = 0;    /* special return: no errors */
 314                 ret = get_reg(child, addr);
 315                 DBG(DBG_MEM, ("peek $%ld->%#lx\n", addr, ret));
 316                 goto out;
 317
 318         /* When I and D space are separate, this will have to be fixed.  */
 319         case PTRACE_POKETEXT: /* write the word at location addr. */
 320         case PTRACE_POKEDATA: {
 321                 unsigned long tmp = data;
 322                 int copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 1);
 323                 ret = (copied == sizeof(tmp)) ? 0 : -EIO;
 324                 goto out;
 325         }
 326
 327         case PTRACE_POKEUSR: /* write the specified register */
 328                 DBG(DBG_MEM, ("poke $%ld<-%#lx\n", addr, data));
 329                 ret = put_reg(child, addr, data);
 330                 goto out;
 331
 332         case PTRACE_SYSCALL: /* continue and stop at next
 333                                 (return from) syscall */
 334         case PTRACE_CONT:    /* restart after signal. */
 335                 ret = -EIO;
 336                 if ((unsigned long) data > _NSIG)
 337                         goto out;
 338                 if (request == PTRACE_SYSCALL)
 339                         child->flags |= PF_TRACESYS;
 340                 else
 341                         child->flags &= ~PF_TRACESYS;
 342                 child->exit_code = data;
 343                 wake_up_process(child);
 344                 /* make sure single-step breakpoint is gone. */
 345                 ptrace_cancel_bpt(child);
 346                 ret = data;
 347                 goto out;
 348
 349         /*
 350          * Make the child exit.  Best I can do is send it a sigkill.
 351          * perhaps it should be put in the status that it wants to
 352          * exit.
 353          */
 354         case PTRACE_KILL:
 355                 if (child->state != TASK_ZOMBIE) {
 356                         wake_up_process(child);
 357                         child->exit_code = SIGKILL;
 358                 }
 359                 /* make sure single-step breakpoint is gone. */
 360                 ptrace_cancel_bpt(child);
 361                 ret = 0;
 362                 goto out;
 363
 364         case PTRACE_SINGLESTEP:  /* execute single instruction. */
 365                 ret = -EIO;
 366                 if ((unsigned long) data > _NSIG)
 367                         goto out;
 368                 child->thread.bpt_nsaved = -1;  /* mark single-stepping */
 369                 child->flags &= ~PF_TRACESYS;
 370                 wake_up_process(child);
 371                 child->exit_code = data;
 372                 /* give it a chance to run. */
 373                 ret = 0;
 374                 goto out;
 375
 376         case PTRACE_DETACH: /* detach a process that was attached. */
 377                 ret = -EIO;
 378                 if ((unsigned long) data > _NSIG)
 379                         goto out;
 380                 child->flags &= ~(PF_PTRACED|PF_TRACESYS);
 381                 wake_up_process(child);
 382                 child->exit_code = data;
 383                 REMOVE_LINKS(child);
 384                 child->p_pptr = child->p_opptr;
 385                 SET_LINKS(child);
 386                 /* make sure single-step breakpoint is gone. */
 387                 ptrace_cancel_bpt(child);
 388                 ret = 0;
 389                 goto out;
 390
 391         default:
 392                 ret = -EIO;
 393                 goto out;
 394         }
 395  out:
 396         unlock_kernel();
 397         return ret;
 398 }
 399
 400 asmlinkage void
 401 syscall_trace(void)
 402 {
 403         if ((current->flags & (PF_PTRACED|PF_TRACESYS))
 404             != (PF_PTRACED|PF_TRACESYS))
 405                 return;
 406         current->exit_code = SIGTRAP;
 407         current->state = TASK_STOPPED;
 408         notify_parent(current, SIGCHLD);
 409         schedule();
 410         /*
 411          * This isn't the same as continuing with a signal, but it will do
 412          * for normal use.  strace only continues with a signal if the
 413          * stopping signal is not SIGTRAP.  -brl
 414          */
 415         if (current->exit_code) {
 416                 send_sig(current->exit_code, current, 1);
 417                 current->exit_code = 0;
 418         }
 419 }