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1 /*
2  * Kernel support for the ptrace() and syscall tracing interfaces.
3  *
4  * Copyright (C) 2000 Hewlett-Packard Co, Linuxcare Inc.
5  * Copyright (C) 2000 Matthew Wilcox <matthew@wil.cx>
6  * Copyright (C) 2000 David Huggins-Daines <dhd@debian.org>
7  * Copyright (C) 2008 Helge Deller <deller@gmx.de>
8  */
9 
10 #include <linux/kernel.h>
11 #include <linux/sched.h>
12 #include <linux/mm.h>
13 #include <linux/smp.h>
14 #include <linux/errno.h>
15 #include <linux/ptrace.h>
16 #include <linux/tracehook.h>
17 #include <linux/user.h>
18 #include <linux/personality.h>
19 #include <linux/security.h>
20 #include <linux/seccomp.h>
21 #include <linux/compat.h>
22 #include <linux/signal.h>
23 #include <linux/audit.h>
24 
25 #include <asm/uaccess.h>
26 #include <asm/pgtable.h>
27 #include <asm/processor.h>
28 #include <asm/asm-offsets.h>
29 
30 /* PSW bits we allow the debugger to modify */
31 #define USER_PSW_BITS	(PSW_N | PSW_B | PSW_V | PSW_CB)
32 
33 /*
34  * Called by kernel/ptrace.c when detaching..
35  *
36  * Make sure single step bits etc are not set.
37  */
ptrace_disable(struct task_struct * task)38 void ptrace_disable(struct task_struct *task)
39 {
40 	clear_tsk_thread_flag(task, TIF_SINGLESTEP);
41 	clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
42 
43 	/* make sure the trap bits are not set */
44 	pa_psw(task)->r = 0;
45 	pa_psw(task)->t = 0;
46 	pa_psw(task)->h = 0;
47 	pa_psw(task)->l = 0;
48 }
49 
50 /*
51  * The following functions are called by ptrace_resume() when
52  * enabling or disabling single/block tracing.
53  */
user_disable_single_step(struct task_struct * task)54 void user_disable_single_step(struct task_struct *task)
55 {
56 	ptrace_disable(task);
57 }
58 
user_enable_single_step(struct task_struct * task)59 void user_enable_single_step(struct task_struct *task)
60 {
61 	clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
62 	set_tsk_thread_flag(task, TIF_SINGLESTEP);
63 
64 	if (pa_psw(task)->n) {
65 		struct siginfo si;
66 
67 		/* Nullified, just crank over the queue. */
68 		task_regs(task)->iaoq[0] = task_regs(task)->iaoq[1];
69 		task_regs(task)->iasq[0] = task_regs(task)->iasq[1];
70 		task_regs(task)->iaoq[1] = task_regs(task)->iaoq[0] + 4;
71 		pa_psw(task)->n = 0;
72 		pa_psw(task)->x = 0;
73 		pa_psw(task)->y = 0;
74 		pa_psw(task)->z = 0;
75 		pa_psw(task)->b = 0;
76 		ptrace_disable(task);
77 		/* Don't wake up the task, but let the
78 		   parent know something happened. */
79 		si.si_code = TRAP_TRACE;
80 		si.si_addr = (void __user *) (task_regs(task)->iaoq[0] & ~3);
81 		si.si_signo = SIGTRAP;
82 		si.si_errno = 0;
83 		force_sig_info(SIGTRAP, &si, task);
84 		/* notify_parent(task, SIGCHLD); */
85 		return;
86 	}
87 
88 	/* Enable recovery counter traps.  The recovery counter
89 	 * itself will be set to zero on a task switch.  If the
90 	 * task is suspended on a syscall then the syscall return
91 	 * path will overwrite the recovery counter with a suitable
92 	 * value such that it traps once back in user space.  We
93 	 * disable interrupts in the tasks PSW here also, to avoid
94 	 * interrupts while the recovery counter is decrementing.
95 	 */
96 	pa_psw(task)->r = 1;
97 	pa_psw(task)->t = 0;
98 	pa_psw(task)->h = 0;
99 	pa_psw(task)->l = 0;
100 }
101 
user_enable_block_step(struct task_struct * task)102 void user_enable_block_step(struct task_struct *task)
103 {
104 	clear_tsk_thread_flag(task, TIF_SINGLESTEP);
105 	set_tsk_thread_flag(task, TIF_BLOCKSTEP);
106 
107 	/* Enable taken branch trap. */
108 	pa_psw(task)->r = 0;
109 	pa_psw(task)->t = 1;
110 	pa_psw(task)->h = 0;
111 	pa_psw(task)->l = 0;
112 }
113 
arch_ptrace(struct task_struct * child,long request,unsigned long addr,unsigned long data)114 long arch_ptrace(struct task_struct *child, long request,
115 		 unsigned long addr, unsigned long data)
116 {
117 	unsigned long tmp;
118 	long ret = -EIO;
119 
120 	switch (request) {
121 
122 	/* Read the word at location addr in the USER area.  For ptraced
123 	   processes, the kernel saves all regs on a syscall. */
124 	case PTRACE_PEEKUSR:
125 		if ((addr & (sizeof(unsigned long)-1)) ||
126 		     addr >= sizeof(struct pt_regs))
127 			break;
128 		tmp = *(unsigned long *) ((char *) task_regs(child) + addr);
129 		ret = put_user(tmp, (unsigned long __user *) data);
130 		break;
131 
132 	/* Write the word at location addr in the USER area.  This will need
133 	   to change when the kernel no longer saves all regs on a syscall.
134 	   FIXME.  There is a problem at the moment in that r3-r18 are only
135 	   saved if the process is ptraced on syscall entry, and even then
136 	   those values are overwritten by actual register values on syscall
137 	   exit. */
138 	case PTRACE_POKEUSR:
139 		/* Some register values written here may be ignored in
140 		 * entry.S:syscall_restore_rfi; e.g. iaoq is written with
141 		 * r31/r31+4, and not with the values in pt_regs.
142 		 */
143 		if (addr == PT_PSW) {
144 			/* Allow writing to Nullify, Divide-step-correction,
145 			 * and carry/borrow bits.
146 			 * BEWARE, if you set N, and then single step, it won't
147 			 * stop on the nullified instruction.
148 			 */
149 			data &= USER_PSW_BITS;
150 			task_regs(child)->gr[0] &= ~USER_PSW_BITS;
151 			task_regs(child)->gr[0] |= data;
152 			ret = 0;
153 			break;
154 		}
155 
156 		if ((addr & (sizeof(unsigned long)-1)) ||
157 		     addr >= sizeof(struct pt_regs))
158 			break;
159 		if ((addr >= PT_GR1 && addr <= PT_GR31) ||
160 				addr == PT_IAOQ0 || addr == PT_IAOQ1 ||
161 				(addr >= PT_FR0 && addr <= PT_FR31 + 4) ||
162 				addr == PT_SAR) {
163 			*(unsigned long *) ((char *) task_regs(child) + addr) = data;
164 			ret = 0;
165 		}
166 		break;
167 
168 	default:
169 		ret = ptrace_request(child, request, addr, data);
170 		break;
171 	}
172 
173 	return ret;
174 }
175 
176 
177 #ifdef CONFIG_COMPAT
178 
179 /* This function is needed to translate 32 bit pt_regs offsets in to
180  * 64 bit pt_regs offsets.  For example, a 32 bit gdb under a 64 bit kernel
181  * will request offset 12 if it wants gr3, but the lower 32 bits of
182  * the 64 bit kernels view of gr3 will be at offset 28 (3*8 + 4).
183  * This code relies on a 32 bit pt_regs being comprised of 32 bit values
184  * except for the fp registers which (a) are 64 bits, and (b) follow
185  * the gr registers at the start of pt_regs.  The 32 bit pt_regs should
186  * be half the size of the 64 bit pt_regs, plus 32*4 to allow for fr[]
187  * being 64 bit in both cases.
188  */
189 
translate_usr_offset(compat_ulong_t offset)190 static compat_ulong_t translate_usr_offset(compat_ulong_t offset)
191 {
192 	if (offset < 0)
193 		return sizeof(struct pt_regs);
194 	else if (offset <= 32*4)	/* gr[0..31] */
195 		return offset * 2 + 4;
196 	else if (offset <= 32*4+32*8)	/* gr[0..31] + fr[0..31] */
197 		return offset + 32*4;
198 	else if (offset < sizeof(struct pt_regs)/2 + 32*4)
199 		return offset * 2 + 4 - 32*8;
200 	else
201 		return sizeof(struct pt_regs);
202 }
203 
compat_arch_ptrace(struct task_struct * child,compat_long_t request,compat_ulong_t addr,compat_ulong_t data)204 long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
205 			compat_ulong_t addr, compat_ulong_t data)
206 {
207 	compat_uint_t tmp;
208 	long ret = -EIO;
209 
210 	switch (request) {
211 
212 	case PTRACE_PEEKUSR:
213 		if (addr & (sizeof(compat_uint_t)-1))
214 			break;
215 		addr = translate_usr_offset(addr);
216 		if (addr >= sizeof(struct pt_regs))
217 			break;
218 
219 		tmp = *(compat_uint_t *) ((char *) task_regs(child) + addr);
220 		ret = put_user(tmp, (compat_uint_t *) (unsigned long) data);
221 		break;
222 
223 	/* Write the word at location addr in the USER area.  This will need
224 	   to change when the kernel no longer saves all regs on a syscall.
225 	   FIXME.  There is a problem at the moment in that r3-r18 are only
226 	   saved if the process is ptraced on syscall entry, and even then
227 	   those values are overwritten by actual register values on syscall
228 	   exit. */
229 	case PTRACE_POKEUSR:
230 		/* Some register values written here may be ignored in
231 		 * entry.S:syscall_restore_rfi; e.g. iaoq is written with
232 		 * r31/r31+4, and not with the values in pt_regs.
233 		 */
234 		if (addr == PT_PSW) {
235 			/* Since PT_PSW==0, it is valid for 32 bit processes
236 			 * under 64 bit kernels as well.
237 			 */
238 			ret = arch_ptrace(child, request, addr, data);
239 		} else {
240 			if (addr & (sizeof(compat_uint_t)-1))
241 				break;
242 			addr = translate_usr_offset(addr);
243 			if (addr >= sizeof(struct pt_regs))
244 				break;
245 			if (addr >= PT_FR0 && addr <= PT_FR31 + 4) {
246 				/* Special case, fp regs are 64 bits anyway */
247 				*(__u64 *) ((char *) task_regs(child) + addr) = data;
248 				ret = 0;
249 			}
250 			else if ((addr >= PT_GR1+4 && addr <= PT_GR31+4) ||
251 					addr == PT_IAOQ0+4 || addr == PT_IAOQ1+4 ||
252 					addr == PT_SAR+4) {
253 				/* Zero the top 32 bits */
254 				*(__u32 *) ((char *) task_regs(child) + addr - 4) = 0;
255 				*(__u32 *) ((char *) task_regs(child) + addr) = data;
256 				ret = 0;
257 			}
258 		}
259 		break;
260 
261 	default:
262 		ret = compat_ptrace_request(child, request, addr, data);
263 		break;
264 	}
265 
266 	return ret;
267 }
268 #endif
269 
do_syscall_trace_enter(struct pt_regs * regs)270 long do_syscall_trace_enter(struct pt_regs *regs)
271 {
272 	/* Do the secure computing check first. */
273 	secure_computing_strict(regs->gr[20]);
274 
275 	if (test_thread_flag(TIF_SYSCALL_TRACE) &&
276 	    tracehook_report_syscall_entry(regs)) {
277 		/*
278 		 * Tracing decided this syscall should not happen or the
279 		 * debugger stored an invalid system call number. Skip
280 		 * the system call and the system call restart handling.
281 		 */
282 		regs->gr[20] = -1UL;
283 		goto out;
284 	}
285 
286 #ifdef CONFIG_64BIT
287 	if (!is_compat_task())
288 		audit_syscall_entry(regs->gr[20], regs->gr[26], regs->gr[25],
289 				    regs->gr[24], regs->gr[23]);
290 	else
291 #endif
292 		audit_syscall_entry(regs->gr[20] & 0xffffffff,
293 			regs->gr[26] & 0xffffffff,
294 			regs->gr[25] & 0xffffffff,
295 			regs->gr[24] & 0xffffffff,
296 			regs->gr[23] & 0xffffffff);
297 
298 out:
299 	return regs->gr[20];
300 }
301 
do_syscall_trace_exit(struct pt_regs * regs)302 void do_syscall_trace_exit(struct pt_regs *regs)
303 {
304 	int stepping = test_thread_flag(TIF_SINGLESTEP) ||
305 		test_thread_flag(TIF_BLOCKSTEP);
306 
307 	audit_syscall_exit(regs);
308 
309 	if (stepping || test_thread_flag(TIF_SYSCALL_TRACE))
310 		tracehook_report_syscall_exit(regs, stepping);
311 }
312