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