ptrace.c

  1// SPDX-License-Identifier: GPL-2.0
  2/* ptrace.c */
  3/* By Ross Biro 1/23/92 */
  4/* edited by Linus Torvalds */
  5/* mangled further by Bob Manson (manson@santafe.edu) */
  6/* more mutilation by David Mosberger (davidm@azstarnet.com) */
  7
  8#include <linux/kernel.h>
  9#include <linux/sched.h>
 10#include <linux/sched/task_stack.h>
 11#include <linux/mm.h>
 12#include <linux/smp.h>
 13#include <linux/errno.h>
 14#include <linux/ptrace.h>
 15#include <linux/user.h>
 16#include <linux/security.h>
 17#include <linux/signal.h>
 18#include <linux/audit.h>
 19
 20#include <linux/uaccess.h>
 21#include <asm/fpu.h>
 22
 23#include "proto.h"
 24
 25#define DEBUG	DBG_MEM
 26#undef DEBUG
 27
 28#ifdef DEBUG
 29enum {
 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 */
 70enum {
 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#define FP_REG(reg) (offsetof(struct thread_info, reg))
 82
 83static int regoff[] = {
 84	PT_REG(	   r0), PT_REG(	   r1), PT_REG(	   r2), PT_REG(	  r3),
 85	PT_REG(	   r4), PT_REG(	   r5), PT_REG(	   r6), PT_REG(	  r7),
 86	PT_REG(	   r8), SW_REG(	   r9), SW_REG(	  r10), SW_REG(	 r11),
 87	SW_REG(	  r12), SW_REG(	  r13), SW_REG(	  r14), SW_REG(	 r15),
 88	PT_REG(	  r16), PT_REG(	  r17), PT_REG(	  r18), PT_REG(	 r19),
 89	PT_REG(	  r20), PT_REG(	  r21), PT_REG(	  r22), PT_REG(	 r23),
 90	PT_REG(	  r24), PT_REG(	  r25), PT_REG(	  r26), PT_REG(	 r27),
 91	PT_REG(	  r28), PT_REG(	   gp),		   -1,		   -1,
 92	FP_REG(fp[ 0]), FP_REG(fp[ 1]), FP_REG(fp[ 2]), FP_REG(fp[ 3]),
 93	FP_REG(fp[ 4]), FP_REG(fp[ 5]), FP_REG(fp[ 6]), FP_REG(fp[ 7]),
 94	FP_REG(fp[ 8]), FP_REG(fp[ 9]), FP_REG(fp[10]), FP_REG(fp[11]),
 95	FP_REG(fp[12]), FP_REG(fp[13]), FP_REG(fp[14]), FP_REG(fp[15]),
 96	FP_REG(fp[16]), FP_REG(fp[17]), FP_REG(fp[18]), FP_REG(fp[19]),
 97	FP_REG(fp[20]), FP_REG(fp[21]), FP_REG(fp[22]), FP_REG(fp[23]),
 98	FP_REG(fp[24]), FP_REG(fp[25]), FP_REG(fp[26]), FP_REG(fp[27]),
 99	FP_REG(fp[28]), FP_REG(fp[29]), FP_REG(fp[30]), FP_REG(fp[31]),
100	PT_REG(	   pc)
101};
102
103static unsigned long zero;
104
105/*
106 * Get address of register REGNO in task TASK.
107 */
108static unsigned long *
109get_reg_addr(struct task_struct * task, unsigned long regno)
110{
111	unsigned long *addr;
112
113	if (regno == 30) {
114		addr = &task_thread_info(task)->pcb.usp;
115	} else if (regno == 65) {
116		addr = &task_thread_info(task)->pcb.unique;
117	} else if (regno == 31 || regno > 65) {
118		zero = 0;
119		addr = &zero;
120	} else {
121		addr = task_stack_page(task) + regoff[regno];
122	}
123	return addr;
124}
125
126/*
127 * Get contents of register REGNO in task TASK.
128 */
129static unsigned long
130get_reg(struct task_struct * task, unsigned long regno)
131{
132	/* Special hack for fpcr -- combine hardware and software bits.  */
133	if (regno == 63) {
134		unsigned long fpcr = *get_reg_addr(task, regno);
135		unsigned long swcr
136		  = task_thread_info(task)->ieee_state & IEEE_SW_MASK;
137		swcr = swcr_update_status(swcr, fpcr);
138		return fpcr | swcr;
139	}
140	return *get_reg_addr(task, regno);
141}
142
143/*
144 * Write contents of register REGNO in task TASK.
145 */
146static int
147put_reg(struct task_struct *task, unsigned long regno, unsigned long data)
148{
149	if (regno == 63) {
150		task_thread_info(task)->ieee_state
151		  = ((task_thread_info(task)->ieee_state & ~IEEE_SW_MASK)
152		     | (data & IEEE_SW_MASK));
153		data = (data & FPCR_DYN_MASK) | ieee_swcr_to_fpcr(data);
154	}
155	*get_reg_addr(task, regno) = data;
156	return 0;
157}
158
159static inline int
160read_int(struct task_struct *task, unsigned long addr, int * data)
161{
162	int copied = access_process_vm(task, addr, data, sizeof(int),
163			FOLL_FORCE);
164	return (copied == sizeof(int)) ? 0 : -EIO;
165}
166
167static inline int
168write_int(struct task_struct *task, unsigned long addr, int data)
169{
170	int copied = access_process_vm(task, addr, &data, sizeof(int),
171			FOLL_FORCE | FOLL_WRITE);
172	return (copied == sizeof(int)) ? 0 : -EIO;
173}
174
175/*
176 * Set breakpoint.
177 */
178int
179ptrace_set_bpt(struct task_struct * child)
180{
181	int displ, i, res, reg_b, nsaved = 0;
182	unsigned int insn, op_code;
183	unsigned long pc;
184
185	pc  = get_reg(child, REG_PC);
186	res = read_int(child, pc, (int *) &insn);
187	if (res < 0)
188		return res;
189
190	op_code = insn >> 26;
191	if (op_code >= 0x30) {
192		/*
193		 * It's a branch: instead of trying to figure out
194		 * whether the branch will be taken or not, we'll put
195		 * a breakpoint at either location.  This is simpler,
196		 * more reliable, and probably not a whole lot slower
197		 * than the alternative approach of emulating the
198		 * branch (emulation can be tricky for fp branches).
199		 */
200		displ = ((s32)(insn << 11)) >> 9;
201		task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
202		if (displ)		/* guard against unoptimized code */
203			task_thread_info(child)->bpt_addr[nsaved++]
204			  = pc + 4 + displ;
205		DBG(DBG_BPT, ("execing branch\n"));
206	} else if (op_code == 0x1a) {
207		reg_b = (insn >> 16) & 0x1f;
208		task_thread_info(child)->bpt_addr[nsaved++] = get_reg(child, reg_b);
209		DBG(DBG_BPT, ("execing jump\n"));
210	} else {
211		task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
212		DBG(DBG_BPT, ("execing normal insn\n"));
213	}
214
215	/* install breakpoints: */
216	for (i = 0; i < nsaved; ++i) {
217		res = read_int(child, task_thread_info(child)->bpt_addr[i],
218			       (int *) &insn);
219		if (res < 0)
220			return res;
221		task_thread_info(child)->bpt_insn[i] = insn;
222		DBG(DBG_BPT, ("    -> next_pc=%lx\n",
223			      task_thread_info(child)->bpt_addr[i]));
224		res = write_int(child, task_thread_info(child)->bpt_addr[i],
225				BREAKINST);
226		if (res < 0)
227			return res;
228	}
229	task_thread_info(child)->bpt_nsaved = nsaved;
230	return 0;
231}
232
233/*
234 * Ensure no single-step breakpoint is pending.  Returns non-zero
235 * value if child was being single-stepped.
236 */
237int
238ptrace_cancel_bpt(struct task_struct * child)
239{
240	int i, nsaved = task_thread_info(child)->bpt_nsaved;
241
242	task_thread_info(child)->bpt_nsaved = 0;
243
244	if (nsaved > 2) {
245		printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
246		nsaved = 2;
247	}
248
249	for (i = 0; i < nsaved; ++i) {
250		write_int(child, task_thread_info(child)->bpt_addr[i],
251			  task_thread_info(child)->bpt_insn[i]);
252	}
253	return (nsaved != 0);
254}
255
256void user_enable_single_step(struct task_struct *child)
257{
258	/* Mark single stepping.  */
259	task_thread_info(child)->bpt_nsaved = -1;
260}
261
262void user_disable_single_step(struct task_struct *child)
263{
264	ptrace_cancel_bpt(child);
265}
266
267/*
268 * Called by kernel/ptrace.c when detaching..
269 *
270 * Make sure the single step bit is not set.
271 */
272void ptrace_disable(struct task_struct *child)
273{ 
274	user_disable_single_step(child);
275}
276
277long arch_ptrace(struct task_struct *child, long request,
278		 unsigned long addr, unsigned long data)
279{
280	unsigned long tmp;
281	size_t copied;
282	long ret;
283
284	switch (request) {
285	/* When I and D space are separate, these will need to be fixed.  */
286	case PTRACE_PEEKTEXT: /* read word at location addr. */
287	case PTRACE_PEEKDATA:
288		copied = ptrace_access_vm(child, addr, &tmp, sizeof(tmp),
289				FOLL_FORCE);
290		ret = -EIO;
291		if (copied != sizeof(tmp))
292			break;
293		
294		force_successful_syscall_return();
295		ret = tmp;
296		break;
297
298	/* Read register number ADDR. */
299	case PTRACE_PEEKUSR:
300		force_successful_syscall_return();
301		ret = get_reg(child, addr);
302		DBG(DBG_MEM, ("peek $%lu->%#lx\n", addr, ret));
303		break;
304
305	/* When I and D space are separate, this will have to be fixed.  */
306	case PTRACE_POKETEXT: /* write the word at location addr. */
307	case PTRACE_POKEDATA:
308		ret = generic_ptrace_pokedata(child, addr, data);
309		break;
310
311	case PTRACE_POKEUSR: /* write the specified register */
312		DBG(DBG_MEM, ("poke $%lu<-%#lx\n", addr, data));
313		ret = put_reg(child, addr, data);
314		break;
315	default:
316		ret = ptrace_request(child, request, addr, data);
317		break;
318	}
319	return ret;
320}
321
322asmlinkage unsigned long syscall_trace_enter(void)
323{
324	unsigned long ret = 0;
325	struct pt_regs *regs = current_pt_regs();
326	if (test_thread_flag(TIF_SYSCALL_TRACE) &&
327	    ptrace_report_syscall_entry(current_pt_regs()))
328		ret = -1UL;
329	audit_syscall_entry(regs->r0, regs->r16, regs->r17, regs->r18, regs->r19);
330	return ret ?: current_pt_regs()->r0;
331}
332
333asmlinkage void
334syscall_trace_leave(void)
335{
336	audit_syscall_exit(current_pt_regs());
337	if (test_thread_flag(TIF_SYSCALL_TRACE))
338		ptrace_report_syscall_exit(current_pt_regs(), 0);
339}