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
get_user_regs(struct task_struct * tsk)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
user_enable_single_step(struct task_struct * tsk)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
user_disable_single_step(struct task_struct * child)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 */
ptrace_disable(struct task_struct * child)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 */
ptrace_read_user(struct task_struct * tsk,unsigned long offset,unsigned long __user * data)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 */
ptrace_write_user(struct task_struct * tsk,unsigned long offset,unsigned long value)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
ptrace_getregs(struct task_struct * tsk,void __user * uregs)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
ptrace_setregs(struct task_struct * tsk,const void __user * uregs)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
arch_ptrace(struct task_struct * child,long request,unsigned long addr,unsigned long data)149 long arch_ptrace(struct task_struct *child, long request,
150 unsigned long addr, unsigned long data)
151 {
152 int ret;
153 void __user *datap = (void __user *) data;
154
155 switch (request) {
156 /* Read the word at location addr in the child process */
157 case PTRACE_PEEKTEXT:
158 case PTRACE_PEEKDATA:
159 ret = generic_ptrace_peekdata(child, addr, data);
160 break;
161
162 case PTRACE_PEEKUSR:
163 ret = ptrace_read_user(child, addr, datap);
164 break;
165
166 /* Write the word in data at location addr */
167 case PTRACE_POKETEXT:
168 case PTRACE_POKEDATA:
169 ret = generic_ptrace_pokedata(child, addr, data);
170 break;
171
172 case PTRACE_POKEUSR:
173 ret = ptrace_write_user(child, addr, data);
174 break;
175
176 case PTRACE_GETREGS:
177 ret = ptrace_getregs(child, datap);
178 break;
179
180 case PTRACE_SETREGS:
181 ret = ptrace_setregs(child, datap);
182 break;
183
184 default:
185 ret = ptrace_request(child, request, addr, data);
186 break;
187 }
188
189 return ret;
190 }
191
syscall_trace(void)192 asmlinkage void syscall_trace(void)
193 {
194 if (!test_thread_flag(TIF_SYSCALL_TRACE))
195 return;
196 if (!(current->ptrace & PT_PTRACED))
197 return;
198
199 /* The 0x80 provides a way for the tracing parent to
200 * distinguish between a syscall stop and SIGTRAP delivery */
201 ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
202 ? 0x80 : 0));
203
204 /*
205 * this isn't the same as continuing with a signal, but it
206 * will do for normal use. strace only continues with a
207 * signal if the stopping signal is not SIGTRAP. -brl
208 */
209 if (current->exit_code) {
210 pr_debug("syscall_trace: sending signal %d to PID %u\n",
211 current->exit_code, current->pid);
212 send_sig(current->exit_code, current, 1);
213 current->exit_code = 0;
214 }
215 }
216
217 /*
218 * debug_trampoline() is an assembly stub which will store all user
219 * registers on the stack and execute a breakpoint instruction.
220 *
221 * If we single-step into an exception handler which runs with
222 * interrupts disabled the whole time so it doesn't have to check for
223 * pending work, its return address will be modified so that it ends
224 * up returning to debug_trampoline.
225 *
226 * If the exception handler decides to store the user context and
227 * enable interrupts after all, it will restore the original return
228 * address and status register value. Before it returns, it will
229 * notice that TIF_BREAKPOINT is set and execute a breakpoint
230 * instruction.
231 */
232 extern void debug_trampoline(void);
233
do_debug(struct pt_regs * regs)234 asmlinkage struct pt_regs *do_debug(struct pt_regs *regs)
235 {
236 struct thread_info *ti;
237 unsigned long trampoline_addr;
238 u32 status;
239 u32 ctrl;
240 int code;
241
242 status = ocd_read(DS);
243 ti = current_thread_info();
244 code = TRAP_BRKPT;
245
246 pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n",
247 status, regs->pc, regs->sr, ti->flags);
248
249 if (!user_mode(regs)) {
250 unsigned long die_val = DIE_BREAKPOINT;
251
252 if (status & (1 << OCD_DS_SSS_BIT))
253 die_val = DIE_SSTEP;
254
255 if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP)
256 == NOTIFY_STOP)
257 return regs;
258
259 if ((status & (1 << OCD_DS_SWB_BIT))
260 && test_and_clear_ti_thread_flag(
261 ti, TIF_BREAKPOINT)) {
262 /*
263 * Explicit breakpoint from trampoline or
264 * exception/syscall/interrupt handler.
265 *
266 * The real saved regs are on the stack right
267 * after the ones we saved on entry.
268 */
269 regs++;
270 pr_debug(" -> TIF_BREAKPOINT done, adjusted regs:"
271 "PC=0x%08lx SR=0x%08lx\n",
272 regs->pc, regs->sr);
273 BUG_ON(!user_mode(regs));
274
275 if (test_thread_flag(TIF_SINGLE_STEP)) {
276 pr_debug("Going to do single step...\n");
277 return regs;
278 }
279
280 /*
281 * No TIF_SINGLE_STEP means we're done
282 * stepping over a syscall. Do the trap now.
283 */
284 code = TRAP_TRACE;
285 } else if ((status & (1 << OCD_DS_SSS_BIT))
286 && test_ti_thread_flag(ti, TIF_SINGLE_STEP)) {
287
288 pr_debug("Stepped into something, "
289 "setting TIF_BREAKPOINT...\n");
290 set_ti_thread_flag(ti, TIF_BREAKPOINT);
291
292 /*
293 * We stepped into an exception, interrupt or
294 * syscall handler. Some exception handlers
295 * don't check for pending work, so we need to
296 * set up a trampoline just in case.
297 *
298 * The exception entry code will undo the
299 * trampoline stuff if it does a full context
300 * save (which also means that it'll check for
301 * pending work later.)
302 */
303 if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) {
304 trampoline_addr
305 = (unsigned long)&debug_trampoline;
306
307 pr_debug("Setting up trampoline...\n");
308 ti->rar_saved = sysreg_read(RAR_EX);
309 ti->rsr_saved = sysreg_read(RSR_EX);
310 sysreg_write(RAR_EX, trampoline_addr);
311 sysreg_write(RSR_EX, (MODE_EXCEPTION
312 | SR_EM | SR_GM));
313 BUG_ON(ti->rsr_saved & MODE_MASK);
314 }
315
316 /*
317 * If we stepped into a system call, we
318 * shouldn't do a single step after we return
319 * since the return address is right after the
320 * "scall" instruction we were told to step
321 * over.
322 */
323 if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) {
324 pr_debug("Supervisor; no single step\n");
325 clear_ti_thread_flag(ti, TIF_SINGLE_STEP);
326 }
327
328 ctrl = ocd_read(DC);
329 ctrl &= ~(1 << OCD_DC_SS_BIT);
330 ocd_write(DC, ctrl);
331
332 return regs;
333 } else {
334 printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n",
335 status);
336 printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags);
337 die("Unhandled debug trap in kernel mode",
338 regs, SIGTRAP);
339 }
340 } else if (status & (1 << OCD_DS_SSS_BIT)) {
341 /* Single step in user mode */
342 code = TRAP_TRACE;
343
344 ctrl = ocd_read(DC);
345 ctrl &= ~(1 << OCD_DC_SS_BIT);
346 ocd_write(DC, ctrl);
347 }
348
349 pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n",
350 code, regs->pc, regs->sr);
351
352 clear_thread_flag(TIF_SINGLE_STEP);
353 _exception(SIGTRAP, regs, code, instruction_pointer(regs));
354
355 return regs;
356 }
357