1/*
  2 * User-space Probes (UProbes) for x86
  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 as published by
  6 * the Free Software Foundation; either version 2 of the License, or
  7 * (at your option) any later version.
  8 *
  9 * This program is distributed in the hope that it will be useful,
 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 * GNU General Public License for more details.
 13 *
 14 * You should have received a copy of the GNU General Public License
 15 * along with this program; if not, write to the Free Software
 16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 17 *
 18 * Copyright (C) IBM Corporation, 2008-2011
 19 * Authors:
 20 *	Srikar Dronamraju
 21 *	Jim Keniston
 22 */
 23#include <linux/kernel.h>
 24#include <linux/sched.h>
 25#include <linux/ptrace.h>
 26#include <linux/uprobes.h>
 27#include <linux/uaccess.h>
 28
 29#include <linux/kdebug.h>
 30#include <asm/processor.h>
 31#include <asm/insn.h>
 
 32
 33/* Post-execution fixups. */
 34
 35/* No fixup needed */
 36#define UPROBE_FIX_NONE		0x0
 37
 38/* Adjust IP back to vicinity of actual insn */
 39#define UPROBE_FIX_IP		0x1
 40
 41/* Adjust the return address of a call insn */
 42#define UPROBE_FIX_CALL	0x2
 
 
 
 43
 44#define UPROBE_FIX_RIP_AX	0x8000
 45#define UPROBE_FIX_RIP_CX	0x4000
 
 
 
 46
 47#define	UPROBE_TRAP_NR		UINT_MAX
 48
 49/* Adaptations for mhiramat x86 decoder v14. */
 50#define OPCODE1(insn)		((insn)->opcode.bytes[0])
 51#define OPCODE2(insn)		((insn)->opcode.bytes[1])
 52#define OPCODE3(insn)		((insn)->opcode.bytes[2])
 53#define MODRM_REG(insn)		X86_MODRM_REG(insn->modrm.value)
 54
 55#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
 56	(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
 57	  (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
 58	  (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
 59	  (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
 60	 << (row % 32))
 61
 62/*
 63 * Good-instruction tables for 32-bit apps.  This is non-const and volatile
 64 * to keep gcc from statically optimizing it out, as variable_test_bit makes
 65 * some versions of gcc to think only *(unsigned long*) is used.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 66 */
 
 67static volatile u32 good_insns_32[256 / 32] = {
 68	/*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f         */
 69	/*      ----------------------------------------------         */
 70	W(0x00, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) | /* 00 */
 71	W(0x10, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0) , /* 10 */
 72	W(0x20, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1) | /* 20 */
 73	W(0x30, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1) , /* 30 */
 74	W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
 75	W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
 76	W(0x60, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */
 77	W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */
 78	W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
 79	W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
 80	W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */
 81	W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
 82	W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */
 83	W(0xd0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
 84	W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* e0 */
 85	W(0xf0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1)   /* f0 */
 86	/*      ----------------------------------------------         */
 87	/*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f         */
 88};
 
 
 
 89
 90/* Using this for both 64-bit and 32-bit apps */
 91static volatile u32 good_2byte_insns[256 / 32] = {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 92	/*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f         */
 93	/*      ----------------------------------------------         */
 94	W(0x00, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1) | /* 00 */
 95	W(0x10, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1) , /* 10 */
 96	W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* 20 */
 97	W(0x30, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
 98	W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
 99	W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
100	W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 60 */
101	W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
102	W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
103	W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
104	W(0xa0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1) | /* a0 */
105	W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
106	W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
107	W(0xd0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
108	W(0xe0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* e0 */
109	W(0xf0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0)   /* f0 */
110	/*      ----------------------------------------------         */
111	/*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f         */
112};
 
 
 
113
114#ifdef CONFIG_X86_64
115/* Good-instruction tables for 64-bit apps */
116static volatile u32 good_insns_64[256 / 32] = {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
117	/*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f         */
118	/*      ----------------------------------------------         */
119	W(0x00, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) | /* 00 */
120	W(0x10, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) , /* 10 */
121	W(0x20, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) | /* 20 */
122	W(0x30, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0) , /* 30 */
123	W(0x40, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 40 */
124	W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 50 */
125	W(0x60, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* 60 */
126	W(0x70, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 70 */
127	W(0x80, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
128	W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
129	W(0xa0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* a0 */
130	W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* b0 */
131	W(0xc0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0) | /* c0 */
132	W(0xd0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
133	W(0xe0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* e0 */
134	W(0xf0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1)   /* f0 */
135	/*      ----------------------------------------------         */
136	/*      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f         */
137};
138#endif
139#undef W
140
141/*
142 * opcodes we'll probably never support:
143 *
144 *  6c-6d, e4-e5, ec-ed - in
145 *  6e-6f, e6-e7, ee-ef - out
146 *  cc, cd - int3, int
147 *  cf - iret
148 *  d6 - illegal instruction
149 *  f1 - int1/icebp
150 *  f4 - hlt
151 *  fa, fb - cli, sti
152 *  0f - lar, lsl, syscall, clts, sysret, sysenter, sysexit, invd, wbinvd, ud2
153 *
154 * invalid opcodes in 64-bit mode:
155 *
156 *  06, 0e, 16, 1e, 27, 2f, 37, 3f, 60-62, 82, c4-c5, d4-d5
157 *  63 - we support this opcode in x86_64 but not in i386.
158 *
159 * opcodes we may need to refine support for:
160 *
161 *  0f - 2-byte instructions: For many of these instructions, the validity
162 *  depends on the prefix and/or the reg field.  On such instructions, we
163 *  just consider the opcode combination valid if it corresponds to any
164 *  valid instruction.
165 *
166 *  8f - Group 1 - only reg = 0 is OK
167 *  c6-c7 - Group 11 - only reg = 0 is OK
168 *  d9-df - fpu insns with some illegal encodings
169 *  f2, f3 - repnz, repz prefixes.  These are also the first byte for
170 *  certain floating-point instructions, such as addsd.
171 *
172 *  fe - Group 4 - only reg = 0 or 1 is OK
173 *  ff - Group 5 - only reg = 0-6 is OK
174 *
175 * others -- Do we need to support these?
176 *
177 *  0f - (floating-point?) prefetch instructions
178 *  07, 17, 1f - pop es, pop ss, pop ds
179 *  26, 2e, 36, 3e - es:, cs:, ss:, ds: segment prefixes --
180 *	but 64 and 65 (fs: and gs:) seem to be used, so we support them
181 *  67 - addr16 prefix
182 *  ce - into
183 *  f0 - lock prefix
184 */
185
186/*
187 * TODO:
188 * - Where necessary, examine the modrm byte and allow only valid instructions
189 * in the different Groups and fpu instructions.
190 */
191
192static bool is_prefix_bad(struct insn *insn)
193{
 
194	int i;
195
196	for (i = 0; i < insn->prefixes.nbytes; i++) {
197		switch (insn->prefixes.bytes[i]) {
198		case 0x26:	/* INAT_PFX_ES   */
199		case 0x2E:	/* INAT_PFX_CS   */
200		case 0x36:	/* INAT_PFX_DS   */
201		case 0x3E:	/* INAT_PFX_SS   */
202		case 0xF0:	/* INAT_PFX_LOCK */
 
 
 
203			return true;
204		}
205	}
206	return false;
207}
208
209static int validate_insn_32bits(struct arch_uprobe *auprobe, struct insn *insn)
210{
211	insn_init(insn, auprobe->insn, false);
 
 
 
 
 
 
212
213	/* Skip good instruction prefixes; reject "bad" ones. */
214	insn_get_opcode(insn);
215	if (is_prefix_bad(insn))
216		return -ENOTSUPP;
217
218	if (test_bit(OPCODE1(insn), (unsigned long *)good_insns_32))
 
 
 
 
 
 
 
 
 
219		return 0;
220
221	if (insn->opcode.nbytes == 2) {
222		if (test_bit(OPCODE2(insn), (unsigned long *)good_2byte_insns))
223			return 0;
224	}
225
226	return -ENOTSUPP;
227}
228
229/*
230 * Figure out which fixups arch_uprobe_post_xol() will need to perform, and
231 * annotate arch_uprobe->fixups accordingly.  To start with,
232 * arch_uprobe->fixups is either zero or it reflects rip-related fixups.
233 */
234static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn)
235{
236	bool fix_ip = true, fix_call = false;	/* defaults */
237	int reg;
238
239	insn_get_opcode(insn);	/* should be a nop */
240
241	switch (OPCODE1(insn)) {
242	case 0xc3:		/* ret/lret */
243	case 0xcb:
244	case 0xc2:
245	case 0xca:
246		/* ip is correct */
247		fix_ip = false;
248		break;
249	case 0xe8:		/* call relative - Fix return addr */
250		fix_call = true;
251		break;
252	case 0x9a:		/* call absolute - Fix return addr, not ip */
253		fix_call = true;
254		fix_ip = false;
255		break;
256	case 0xff:
257		insn_get_modrm(insn);
258		reg = MODRM_REG(insn);
259		if (reg == 2 || reg == 3) {
260			/* call or lcall, indirect */
261			/* Fix return addr; ip is correct. */
262			fix_call = true;
263			fix_ip = false;
264		} else if (reg == 4 || reg == 5) {
265			/* jmp or ljmp, indirect */
266			/* ip is correct. */
267			fix_ip = false;
268		}
269		break;
270	case 0xea:		/* jmp absolute -- ip is correct */
271		fix_ip = false;
272		break;
273	default:
274		break;
275	}
276	if (fix_ip)
277		auprobe->fixups |= UPROBE_FIX_IP;
278	if (fix_call)
279		auprobe->fixups |= UPROBE_FIX_CALL;
280}
281
282#ifdef CONFIG_X86_64
283/*
284 * If arch_uprobe->insn doesn't use rip-relative addressing, return
285 * immediately.  Otherwise, rewrite the instruction so that it accesses
286 * its memory operand indirectly through a scratch register.  Set
287 * arch_uprobe->fixups and arch_uprobe->rip_rela_target_address
288 * accordingly.  (The contents of the scratch register will be saved
289 * before we single-step the modified instruction, and restored
290 * afterward.)
291 *
292 * We do this because a rip-relative instruction can access only a
293 * relatively small area (+/- 2 GB from the instruction), and the XOL
294 * area typically lies beyond that area.  At least for instructions
295 * that store to memory, we can't execute the original instruction
296 * and "fix things up" later, because the misdirected store could be
297 * disastrous.
298 *
299 * Some useful facts about rip-relative instructions:
300 *
301 *  - There's always a modrm byte.
302 *  - There's never a SIB byte.
303 *  - The displacement is always 4 bytes.
 
 
 
304 */
305static void
306handle_riprel_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, struct insn *insn)
307{
308	u8 *cursor;
309	u8 reg;
 
310
311	if (mm->context.ia32_compat)
312		return;
313
314	auprobe->rip_rela_target_address = 0x0;
315	if (!insn_rip_relative(insn))
316		return;
317
318	/*
319	 * insn_rip_relative() would have decoded rex_prefix, modrm.
320	 * Clear REX.b bit (extension of MODRM.rm field):
321	 * we want to encode rax/rcx, not r8/r9.
322	 */
323	if (insn->rex_prefix.nbytes) {
324		cursor = auprobe->insn + insn_offset_rex_prefix(insn);
325		*cursor &= 0xfe;	/* Clearing REX.B bit */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
326	}
327
328	/*
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
329	 * Point cursor at the modrm byte.  The next 4 bytes are the
330	 * displacement.  Beyond the displacement, for some instructions,
331	 * is the immediate operand.
332	 */
333	cursor = auprobe->insn + insn_offset_modrm(insn);
334	insn_get_length(insn);
335
336	/*
337	 * Convert from rip-relative addressing to indirect addressing
338	 * via a scratch register.  Change the r/m field from 0x5 (%rip)
339	 * to 0x0 (%rax) or 0x1 (%rcx), and squeeze out the offset field.
340	 */
341	reg = MODRM_REG(insn);
342	if (reg == 0) {
343		/*
344		 * The register operand (if any) is either the A register
345		 * (%rax, %eax, etc.) or (if the 0x4 bit is set in the
346		 * REX prefix) %r8.  In any case, we know the C register
347		 * is NOT the register operand, so we use %rcx (register
348		 * #1) for the scratch register.
349		 */
350		auprobe->fixups = UPROBE_FIX_RIP_CX;
351		/* Change modrm from 00 000 101 to 00 000 001. */
352		*cursor = 0x1;
353	} else {
354		/* Use %rax (register #0) for the scratch register. */
355		auprobe->fixups = UPROBE_FIX_RIP_AX;
356		/* Change modrm from 00 xxx 101 to 00 xxx 000 */
357		*cursor = (reg << 3);
358	}
359
360	/* Target address = address of next instruction + (signed) offset */
361	auprobe->rip_rela_target_address = (long)insn->length + insn->displacement.value;
362
363	/* Displacement field is gone; slide immediate field (if any) over. */
364	if (insn->immediate.nbytes) {
365		cursor++;
366		memmove(cursor, cursor + insn->displacement.nbytes, insn->immediate.nbytes);
367	}
368	return;
369}
370
371static int validate_insn_64bits(struct arch_uprobe *auprobe, struct insn *insn)
 
372{
373	insn_init(insn, auprobe->insn, true);
374
375	/* Skip good instruction prefixes; reject "bad" ones. */
376	insn_get_opcode(insn);
377	if (is_prefix_bad(insn))
378		return -ENOTSUPP;
379
380	if (test_bit(OPCODE1(insn), (unsigned long *)good_insns_64))
381		return 0;
 
 
 
 
 
 
 
382
383	if (insn->opcode.nbytes == 2) {
384		if (test_bit(OPCODE2(insn), (unsigned long *)good_2byte_insns))
385			return 0;
386	}
387	return -ENOTSUPP;
388}
389
390static int validate_insn_bits(struct arch_uprobe *auprobe, struct mm_struct *mm, struct insn *insn)
391{
392	if (mm->context.ia32_compat)
393		return validate_insn_32bits(auprobe, insn);
394	return validate_insn_64bits(auprobe, insn);
 
 
 
395}
396#else /* 32-bit: */
397static void handle_riprel_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, struct insn *insn)
 
 
 
398{
399	/* No RIP-relative addressing on 32-bit */
400}
401
402static int validate_insn_bits(struct arch_uprobe *auprobe, struct mm_struct *mm,  struct insn *insn)
 
 
403{
404	return validate_insn_32bits(auprobe, insn);
405}
406#endif /* CONFIG_X86_64 */
407
408/**
409 * arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
410 * @mm: the probed address space.
411 * @arch_uprobe: the probepoint information.
412 * Return 0 on success or a -ve number on error.
413 */
414int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm)
 
415{
416	int ret;
417	struct insn insn;
 
 
 
418
419	auprobe->fixups = 0;
420	ret = validate_insn_bits(auprobe, mm, &insn);
421	if (ret != 0)
422		return ret;
 
 
 
 
 
423
424	handle_riprel_insn(auprobe, mm, &insn);
425	prepare_fixups(auprobe, &insn);
426
 
427	return 0;
428}
429
430#ifdef CONFIG_X86_64
431/*
432 * If we're emulating a rip-relative instruction, save the contents
433 * of the scratch register and store the target address in that register.
 
 
 
 
 
 
 
 
 
 
 
 
 
434 */
435static void
436pre_xol_rip_insn(struct arch_uprobe *auprobe, struct pt_regs *regs,
437				struct arch_uprobe_task *autask)
438{
439	if (auprobe->fixups & UPROBE_FIX_RIP_AX) {
440		autask->saved_scratch_register = regs->ax;
441		regs->ax = current->utask->vaddr;
442		regs->ax += auprobe->rip_rela_target_address;
443	} else if (auprobe->fixups & UPROBE_FIX_RIP_CX) {
444		autask->saved_scratch_register = regs->cx;
445		regs->cx = current->utask->vaddr;
446		regs->cx += auprobe->rip_rela_target_address;
447	}
 
 
 
 
 
448}
449#else
450static void
451pre_xol_rip_insn(struct arch_uprobe *auprobe, struct pt_regs *regs,
452				struct arch_uprobe_task *autask)
453{
454	/* No RIP-relative addressing on 32-bit */
455}
456#endif
457
458/*
459 * arch_uprobe_pre_xol - prepare to execute out of line.
460 * @auprobe: the probepoint information.
461 * @regs: reflects the saved user state of current task.
462 */
463int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 
464{
465	struct arch_uprobe_task *autask;
 
466
467	autask = &current->utask->autask;
468	autask->saved_trap_nr = current->thread.trap_nr;
469	current->thread.trap_nr = UPROBE_TRAP_NR;
470	regs->ip = current->utask->xol_vaddr;
471	pre_xol_rip_insn(auprobe, regs, autask);
 
 
 
 
 
 
 
 
472
473	return 0;
 
 
 
 
 
 
 
 
 
 
 
 
474}
475
476/*
477 * This function is called by arch_uprobe_post_xol() to adjust the return
478 * address pushed by a call instruction executed out of line.
479 */
480static int adjust_ret_addr(unsigned long sp, long correction)
481{
482	int rasize, ncopied;
483	long ra = 0;
484
485	if (is_ia32_task())
486		rasize = 4;
487	else
488		rasize = 8;
 
489
490	ncopied = copy_from_user(&ra, (void __user *)sp, rasize);
491	if (unlikely(ncopied))
492		return -EFAULT;
 
493
494	ra += correction;
495	ncopied = copy_to_user((void __user *)sp, &ra, rasize);
496	if (unlikely(ncopied))
497		return -EFAULT;
498
499	return 0;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
500}
501
502#ifdef CONFIG_X86_64
503static bool is_riprel_insn(struct arch_uprobe *auprobe)
 
 
 
 
 
 
 
 
 
504{
505	return ((auprobe->fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) != 0);
 
 
 
 
 
 
 
 
506}
507
508static void
509handle_riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs, long *correction)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
510{
511	if (is_riprel_insn(auprobe)) {
512		struct arch_uprobe_task *autask;
 
 
 
 
 
 
 
 
513
514		autask = &current->utask->autask;
515		if (auprobe->fixups & UPROBE_FIX_RIP_AX)
516			regs->ax = autask->saved_scratch_register;
517		else
518			regs->cx = autask->saved_scratch_register;
519
 
 
 
520		/*
521		 * The original instruction includes a displacement, and so
522		 * is 4 bytes longer than what we've just single-stepped.
523		 * Fall through to handle stuff like "jmpq *...(%rip)" and
524		 * "callq *...(%rip)".
525		 */
526		if (correction)
527			*correction += 4;
 
 
 
528	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
529}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
530#else
531static void
532handle_riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs, long *correction)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
533{
534	/* No RIP-relative addressing on 32-bit */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
535}
536#endif
537
538/*
539 * If xol insn itself traps and generates a signal(Say,
540 * SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
541 * instruction jumps back to its own address. It is assumed that anything
542 * like do_page_fault/do_trap/etc sets thread.trap_nr != -1.
543 *
544 * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
545 * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
546 * UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
547 */
548bool arch_uprobe_xol_was_trapped(struct task_struct *t)
549{
550	if (t->thread.trap_nr != UPROBE_TRAP_NR)
551		return true;
552
553	return false;
554}
555
556/*
557 * Called after single-stepping. To avoid the SMP problems that can
558 * occur when we temporarily put back the original opcode to
559 * single-step, we single-stepped a copy of the instruction.
560 *
561 * This function prepares to resume execution after the single-step.
562 * We have to fix things up as follows:
563 *
564 * Typically, the new ip is relative to the copied instruction.  We need
565 * to make it relative to the original instruction (FIX_IP).  Exceptions
566 * are return instructions and absolute or indirect jump or call instructions.
567 *
568 * If the single-stepped instruction was a call, the return address that
569 * is atop the stack is the address following the copied instruction.  We
570 * need to make it the address following the original instruction (FIX_CALL).
571 *
572 * If the original instruction was a rip-relative instruction such as
573 * "movl %edx,0xnnnn(%rip)", we have instead executed an equivalent
574 * instruction using a scratch register -- e.g., "movl %edx,(%rax)".
575 * We need to restore the contents of the scratch register and adjust
576 * the ip, keeping in mind that the instruction we executed is 4 bytes
577 * shorter than the original instruction (since we squeezed out the offset
578 * field).  (FIX_RIP_AX or FIX_RIP_CX)
579 */
580int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
581{
582	struct uprobe_task *utask;
583	long correction;
584	int result = 0;
585
586	WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
587
588	utask = current->utask;
589	current->thread.trap_nr = utask->autask.saved_trap_nr;
590	correction = (long)(utask->vaddr - utask->xol_vaddr);
591	handle_riprel_post_xol(auprobe, regs, &correction);
592	if (auprobe->fixups & UPROBE_FIX_IP)
593		regs->ip += correction;
594
595	if (auprobe->fixups & UPROBE_FIX_CALL)
596		result = adjust_ret_addr(regs->sp, correction);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
597
598	return result;
599}
600
601/* callback routine for handling exceptions. */
602int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
603{
604	struct die_args *args = data;
605	struct pt_regs *regs = args->regs;
606	int ret = NOTIFY_DONE;
607
608	/* We are only interested in userspace traps */
609	if (regs && !user_mode_vm(regs))
610		return NOTIFY_DONE;
611
612	switch (val) {
613	case DIE_INT3:
614		if (uprobe_pre_sstep_notifier(regs))
615			ret = NOTIFY_STOP;
616
617		break;
618
619	case DIE_DEBUG:
620		if (uprobe_post_sstep_notifier(regs))
621			ret = NOTIFY_STOP;
622
 
 
623	default:
624		break;
625	}
626
627	return ret;
628}
629
630/*
631 * This function gets called when XOL instruction either gets trapped or
632 * the thread has a fatal signal, so reset the instruction pointer to its
633 * probed address.
634 */
635void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
636{
637	struct uprobe_task *utask = current->utask;
638
 
 
 
639	current->thread.trap_nr = utask->autask.saved_trap_nr;
640	handle_riprel_post_xol(auprobe, regs, NULL);
641	instruction_pointer_set(regs, utask->vaddr);
 
 
 
 
 
 
 
 
 
642}
643
644/*
645 * Skip these instructions as per the currently known x86 ISA.
646 * 0x66* { 0x90 | 0x0f 0x1f | 0x0f 0x19 | 0x87 0xc0 }
647 */
648bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
649{
650	int i;
 
 
 
 
651
652	for (i = 0; i < MAX_UINSN_BYTES; i++) {
653		if ((auprobe->insn[i] == 0x66))
654			continue;
 
 
655
656		if (auprobe->insn[i] == 0x90)
657			return true;
658
659		if (i == (MAX_UINSN_BYTES - 1))
660			break;
 
661
662		if ((auprobe->insn[i] == 0x0f) && (auprobe->insn[i+1] == 0x1f))
663			return true;
 
664
665		if ((auprobe->insn[i] == 0x0f) && (auprobe->insn[i+1] == 0x19))
666			return true;
667
668		if ((auprobe->insn[i] == 0x87) && (auprobe->insn[i+1] == 0xc0))
669			return true;
670
671		break;
672	}
673	return false;
 
 
 
 
 
 
 
 
 
 
674}