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Linux/arch/alpha/kernel/ptrace.c

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  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/errno.h>
 12 #include <linux/ptrace.h>
 13 #include <linux/user.h>
 14 #include <linux/slab.h>
 15 #include <linux/security.h>
 16 #include <linux/signal.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 #define PT_REG(reg) \
 75   (PAGE_SIZE*2 - sizeof(struct pt_regs) + offsetof(struct pt_regs, reg))
 76 
 77 #define SW_REG(reg) \
 78  (PAGE_SIZE*2 - sizeof(struct pt_regs) - sizeof(struct switch_stack) \
 79   + offsetof(struct switch_stack, reg))
 80 
 81 static int regoff[] = {
 82         PT_REG(    r0), PT_REG(    r1), PT_REG(    r2), PT_REG(   r3),
 83         PT_REG(    r4), PT_REG(    r5), PT_REG(    r6), PT_REG(   r7),
 84         PT_REG(    r8), SW_REG(    r9), SW_REG(   r10), SW_REG(  r11),
 85         SW_REG(   r12), SW_REG(   r13), SW_REG(   r14), SW_REG(  r15),
 86         PT_REG(   r16), PT_REG(   r17), PT_REG(   r18), PT_REG(  r19),
 87         PT_REG(   r20), PT_REG(   r21), PT_REG(   r22), PT_REG(  r23),
 88         PT_REG(   r24), PT_REG(   r25), PT_REG(   r26), PT_REG(  r27),
 89         PT_REG(   r28), PT_REG(    gp),            -1,             -1,
 90         SW_REG(fp[ 0]), SW_REG(fp[ 1]), SW_REG(fp[ 2]), SW_REG(fp[ 3]),
 91         SW_REG(fp[ 4]), SW_REG(fp[ 5]), SW_REG(fp[ 6]), SW_REG(fp[ 7]),
 92         SW_REG(fp[ 8]), SW_REG(fp[ 9]), SW_REG(fp[10]), SW_REG(fp[11]),
 93         SW_REG(fp[12]), SW_REG(fp[13]), SW_REG(fp[14]), SW_REG(fp[15]),
 94         SW_REG(fp[16]), SW_REG(fp[17]), SW_REG(fp[18]), SW_REG(fp[19]),
 95         SW_REG(fp[20]), SW_REG(fp[21]), SW_REG(fp[22]), SW_REG(fp[23]),
 96         SW_REG(fp[24]), SW_REG(fp[25]), SW_REG(fp[26]), SW_REG(fp[27]),
 97         SW_REG(fp[28]), SW_REG(fp[29]), SW_REG(fp[30]), SW_REG(fp[31]),
 98         PT_REG(    pc)
 99 };
100 
101 static unsigned long zero;
102 
103 /*
104  * Get address of register REGNO in task TASK.
105  */
106 static unsigned long *
107 get_reg_addr(struct task_struct * task, unsigned long regno)
108 {
109         unsigned long *addr;
110 
111         if (regno == 30) {
112                 addr = &task_thread_info(task)->pcb.usp;
113         } else if (regno == 65) {
114                 addr = &task_thread_info(task)->pcb.unique;
115         } else if (regno == 31 || regno > 65) {
116                 zero = 0;
117                 addr = &zero;
118         } else {
119                 addr = task_stack_page(task) + regoff[regno];
120         }
121         return addr;
122 }
123 
124 /*
125  * Get contents of register REGNO in task TASK.
126  */
127 static unsigned long
128 get_reg(struct task_struct * task, unsigned long regno)
129 {
130         /* Special hack for fpcr -- combine hardware and software bits.  */
131         if (regno == 63) {
132                 unsigned long fpcr = *get_reg_addr(task, regno);
133                 unsigned long swcr
134                   = task_thread_info(task)->ieee_state & IEEE_SW_MASK;
135                 swcr = swcr_update_status(swcr, fpcr);
136                 return fpcr | swcr;
137         }
138         return *get_reg_addr(task, regno);
139 }
140 
141 /*
142  * Write contents of register REGNO in task TASK.
143  */
144 static int
145 put_reg(struct task_struct *task, unsigned long regno, unsigned long data)
146 {
147         if (regno == 63) {
148                 task_thread_info(task)->ieee_state
149                   = ((task_thread_info(task)->ieee_state & ~IEEE_SW_MASK)
150                      | (data & IEEE_SW_MASK));
151                 data = (data & FPCR_DYN_MASK) | ieee_swcr_to_fpcr(data);
152         }
153         *get_reg_addr(task, regno) = data;
154         return 0;
155 }
156 
157 static inline int
158 read_int(struct task_struct *task, unsigned long addr, int * data)
159 {
160         int copied = access_process_vm(task, addr, data, sizeof(int), 0);
161         return (copied == sizeof(int)) ? 0 : -EIO;
162 }
163 
164 static inline int
165 write_int(struct task_struct *task, unsigned long addr, int data)
166 {
167         int copied = access_process_vm(task, addr, &data, sizeof(int), 1);
168         return (copied == sizeof(int)) ? 0 : -EIO;
169 }
170 
171 /*
172  * Set breakpoint.
173  */
174 int
175 ptrace_set_bpt(struct task_struct * child)
176 {
177         int displ, i, res, reg_b, nsaved = 0;
178         unsigned int insn, op_code;
179         unsigned long pc;
180 
181         pc  = get_reg(child, REG_PC);
182         res = read_int(child, pc, (int *) &insn);
183         if (res < 0)
184                 return res;
185 
186         op_code = insn >> 26;
187         if (op_code >= 0x30) {
188                 /*
189                  * It's a branch: instead of trying to figure out
190                  * whether the branch will be taken or not, we'll put
191                  * a breakpoint at either location.  This is simpler,
192                  * more reliable, and probably not a whole lot slower
193                  * than the alternative approach of emulating the
194                  * branch (emulation can be tricky for fp branches).
195                  */
196                 displ = ((s32)(insn << 11)) >> 9;
197                 task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
198                 if (displ)              /* guard against unoptimized code */
199                         task_thread_info(child)->bpt_addr[nsaved++]
200                           = pc + 4 + displ;
201                 DBG(DBG_BPT, ("execing branch\n"));
202         } else if (op_code == 0x1a) {
203                 reg_b = (insn >> 16) & 0x1f;
204                 task_thread_info(child)->bpt_addr[nsaved++] = get_reg(child, reg_b);
205                 DBG(DBG_BPT, ("execing jump\n"));
206         } else {
207                 task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
208                 DBG(DBG_BPT, ("execing normal insn\n"));
209         }
210 
211         /* install breakpoints: */
212         for (i = 0; i < nsaved; ++i) {
213                 res = read_int(child, task_thread_info(child)->bpt_addr[i],
214                                (int *) &insn);
215                 if (res < 0)
216                         return res;
217                 task_thread_info(child)->bpt_insn[i] = insn;
218                 DBG(DBG_BPT, ("    -> next_pc=%lx\n",
219                               task_thread_info(child)->bpt_addr[i]));
220                 res = write_int(child, task_thread_info(child)->bpt_addr[i],
221                                 BREAKINST);
222                 if (res < 0)
223                         return res;
224         }
225         task_thread_info(child)->bpt_nsaved = nsaved;
226         return 0;
227 }
228 
229 /*
230  * Ensure no single-step breakpoint is pending.  Returns non-zero
231  * value if child was being single-stepped.
232  */
233 int
234 ptrace_cancel_bpt(struct task_struct * child)
235 {
236         int i, nsaved = task_thread_info(child)->bpt_nsaved;
237 
238         task_thread_info(child)->bpt_nsaved = 0;
239 
240         if (nsaved > 2) {
241                 printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
242                 nsaved = 2;
243         }
244 
245         for (i = 0; i < nsaved; ++i) {
246                 write_int(child, task_thread_info(child)->bpt_addr[i],
247                           task_thread_info(child)->bpt_insn[i]);
248         }
249         return (nsaved != 0);
250 }
251 
252 /*
253  * Called by kernel/ptrace.c when detaching..
254  *
255  * Make sure the single step bit is not set.
256  */
257 void ptrace_disable(struct task_struct *child)
258 { 
259         ptrace_cancel_bpt(child);
260 }
261 
262 long arch_ptrace(struct task_struct *child, long request, long addr, long data)
263 {
264         unsigned long tmp;
265         size_t copied;
266         long ret;
267 
268         switch (request) {
269         /* When I and D space are separate, these will need to be fixed.  */
270         case PTRACE_PEEKTEXT: /* read word at location addr. */
271         case PTRACE_PEEKDATA:
272                 copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
273                 ret = -EIO;
274                 if (copied != sizeof(tmp))
275                         break;
276                 
277                 force_successful_syscall_return();
278                 ret = tmp;
279                 break;
280 
281         /* Read register number ADDR. */
282         case PTRACE_PEEKUSR:
283                 force_successful_syscall_return();
284                 ret = get_reg(child, addr);
285                 DBG(DBG_MEM, ("peek $%ld->%#lx\n", addr, ret));
286                 break;
287 
288         /* When I and D space are separate, this will have to be fixed.  */
289         case PTRACE_POKETEXT: /* write the word at location addr. */
290         case PTRACE_POKEDATA:
291                 ret = generic_ptrace_pokedata(child, addr, data);
292                 break;
293 
294         case PTRACE_POKEUSR: /* write the specified register */
295                 DBG(DBG_MEM, ("poke $%ld<-%#lx\n", addr, data));
296                 ret = put_reg(child, addr, data);
297                 break;
298 
299         case PTRACE_SYSCALL:
300                 /* continue and stop at next (return from) syscall */
301         case PTRACE_CONT:    /* restart after signal. */
302                 ret = -EIO;
303                 if (!valid_signal(data))
304                         break;
305                 if (request == PTRACE_SYSCALL)
306                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
307                 else
308                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
309                 child->exit_code = data;
310                 /* make sure single-step breakpoint is gone. */
311                 ptrace_cancel_bpt(child);
312                 wake_up_process(child);
313                 ret = 0;
314                 break;
315 
316         /*
317          * Make the child exit.  Best I can do is send it a sigkill.
318          * perhaps it should be put in the status that it wants to
319          * exit.
320          */
321         case PTRACE_KILL:
322                 ret = 0;
323                 if (child->exit_state == EXIT_ZOMBIE)
324                         break;
325                 child->exit_code = SIGKILL;
326                 /* make sure single-step breakpoint is gone. */
327                 ptrace_cancel_bpt(child);
328                 wake_up_process(child);
329                 break;
330 
331         case PTRACE_SINGLESTEP:  /* execute single instruction. */
332                 ret = -EIO;
333                 if (!valid_signal(data))
334                         break;
335                 /* Mark single stepping.  */
336                 task_thread_info(child)->bpt_nsaved = -1;
337                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
338                 child->exit_code = data;
339                 wake_up_process(child);
340                 /* give it a chance to run. */
341                 ret = 0;
342                 break;
343 
344         default:
345                 ret = ptrace_request(child, request, addr, data);
346                 break;
347         }
348         return ret;
349 }
350 
351 asmlinkage void
352 syscall_trace(void)
353 {
354         if (!test_thread_flag(TIF_SYSCALL_TRACE))
355                 return;
356         if (!(current->ptrace & PT_PTRACED))
357                 return;
358         /* The 0x80 provides a way for the tracing parent to distinguish
359            between a syscall stop and SIGTRAP delivery */
360         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
361                                  ? 0x80 : 0));
362 
363         /*
364          * This isn't the same as continuing with a signal, but it will do
365          * for normal use.  strace only continues with a signal if the
366          * stopping signal is not SIGTRAP.  -brl
367          */
368         if (current->exit_code) {
369                 send_sig(current->exit_code, current, 1);
370                 current->exit_code = 0;
371         }
372 }
373 

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