[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / kprobes / opt.c

/*
 *  Kernel Probes Jump Optimization (Optprobes)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) IBM Corporation, 2002, 2004
 * Copyright (C) Hitachi Ltd., 2012
 */
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/hardirq.h>
#include <linux/preempt.h>
#include <linux/extable.h>
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
#include <linux/ftrace.h>

#include <asm/text-patching.h>
#include <asm/cacheflush.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <linux/uaccess.h>
#include <asm/alternative.h>
#include <asm/insn.h>
#include <asm/debugreg.h>

#include "common.h"

unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
{
	struct optimized_kprobe *op;
	struct kprobe *kp;
	long offs;
	int i;

	for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
		kp = get_kprobe((void *)addr - i);
		/* This function only handles jump-optimized kprobe */
		if (kp && kprobe_optimized(kp)) {
			op = container_of(kp, struct optimized_kprobe, kp);
			/* If op->list is not empty, op is under optimizing */
			if (list_empty(&op->list))
				goto found;
		}
	}

	return addr;
found:
	/*
	 * If the kprobe can be optimized, original bytes which can be
	 * overwritten by jump destination address. In this case, original
	 * bytes must be recovered from op->optinsn.copied_insn buffer.
	 */
	memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
	if (addr == (unsigned long)kp->addr) {
		buf[0] = kp->opcode;
		memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
	} else {
		offs = addr - (unsigned long)kp->addr - 1;
		memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
	}

	return (unsigned long)buf;
}

/* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
{
#ifdef CONFIG_X86_64
	*addr++ = 0x48;
	*addr++ = 0xbf;
#else
	*addr++ = 0xb8;
#endif
	*(unsigned long *)addr = val;
}

asm (
			".global optprobe_template_entry\n"
			"optprobe_template_entry:\n"
#ifdef CONFIG_X86_64
			/* We don't bother saving the ss register */
			"	pushq %rsp\n"
			"	pushfq\n"
			SAVE_REGS_STRING
			"	movq %rsp, %rsi\n"
			".global optprobe_template_val\n"
			"optprobe_template_val:\n"
			ASM_NOP5
			ASM_NOP5
			".global optprobe_template_call\n"
			"optprobe_template_call:\n"
			ASM_NOP5
			/* Move flags to rsp */
			"	movq 144(%rsp), %rdx\n"
			"	movq %rdx, 152(%rsp)\n"
			RESTORE_REGS_STRING
			/* Skip flags entry */
			"	addq $8, %rsp\n"
			"	popfq\n"
#else /* CONFIG_X86_32 */
			"	pushf\n"
			SAVE_REGS_STRING
			"	movl %esp, %edx\n"
			".global optprobe_template_val\n"
			"optprobe_template_val:\n"
			ASM_NOP5
			".global optprobe_template_call\n"
			"optprobe_template_call:\n"
			ASM_NOP5
			RESTORE_REGS_STRING
			"	addl $4, %esp\n"	/* skip cs */
			"	popf\n"
#endif
			".global optprobe_template_end\n"
			"optprobe_template_end:\n");

#define TMPL_MOVE_IDX \
	((long)&optprobe_template_val - (long)&optprobe_template_entry)
#define TMPL_CALL_IDX \
	((long)&optprobe_template_call - (long)&optprobe_template_entry)
#define TMPL_END_IDX \
	((long)&optprobe_template_end - (long)&optprobe_template_entry)

#define INT3_SIZE sizeof(kprobe_opcode_t)

/* Optimized kprobe call back function: called from optinsn */
static void
optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
{
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	unsigned long flags;

	/* This is possible if op is under delayed unoptimizing */
	if (kprobe_disabled(&op->kp))
		return;

	local_irq_save(flags);
	if (kprobe_running()) {
		kprobes_inc_nmissed_count(&op->kp);
	} else {
		/* Save skipped registers */
#ifdef CONFIG_X86_64
		regs->cs = __KERNEL_CS;
#else
		regs->cs = __KERNEL_CS | get_kernel_rpl();
		regs->gs = 0;
#endif
		regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
		regs->orig_ax = ~0UL;

		__this_cpu_write(current_kprobe, &op->kp);
		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
		opt_pre_handler(&op->kp, regs);
		__this_cpu_write(current_kprobe, NULL);
	}
	local_irq_restore(flags);
}
NOKPROBE_SYMBOL(optimized_callback);

static int copy_optimized_instructions(u8 *dest, u8 *src)
{
	int len = 0, ret;

	while (len < RELATIVEJUMP_SIZE) {
		ret = __copy_instruction(dest + len, src + len);
		if (!ret || !can_boost(dest + len))
			return -EINVAL;
		len += ret;
	}
	/* Check whether the address range is reserved */
	if (ftrace_text_reserved(src, src + len - 1) ||
	    alternatives_text_reserved(src, src + len - 1) ||
	    jump_label_text_reserved(src, src + len - 1))
		return -EBUSY;

	return len;
}

/* Check whether insn is indirect jump */
static int insn_is_indirect_jump(struct insn *insn)
{
	return ((insn->opcode.bytes[0] == 0xff &&
		(X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
		insn->opcode.bytes[0] == 0xea);	/* Segment based jump */
}

/* Check whether insn jumps into specified address range */
static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
{
	unsigned long target = 0;

	switch (insn->opcode.bytes[0]) {
	case 0xe0:	/* loopne */
	case 0xe1:	/* loope */
	case 0xe2:	/* loop */
	case 0xe3:	/* jcxz */
	case 0xe9:	/* near relative jump */
	case 0xeb:	/* short relative jump */
		break;
	case 0x0f:
		if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
			break;
		return 0;
	default:
		if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
			break;
		return 0;
	}
	target = (unsigned long)insn->next_byte + insn->immediate.value;

	return (start <= target && target <= start + len);
}

/* Decode whole function to ensure any instructions don't jump into target */
static int can_optimize(unsigned long paddr)
{
	unsigned long addr, size = 0, offset = 0;
	struct insn insn;
	kprobe_opcode_t buf[MAX_INSN_SIZE];

	/* Lookup symbol including addr */
	if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
		return 0;

	/*
	 * Do not optimize in the entry code due to the unstable
	 * stack handling.
	 */
	if ((paddr >= (unsigned long)__entry_text_start) &&
	    (paddr <  (unsigned long)__entry_text_end))
		return 0;

	/* Check there is enough space for a relative jump. */
	if (size - offset < RELATIVEJUMP_SIZE)
		return 0;

	/* Decode instructions */
	addr = paddr - offset;
	while (addr < paddr - offset + size) { /* Decode until function end */
		unsigned long recovered_insn;
		if (search_exception_tables(addr))
			/*
			 * Since some fixup code will jumps into this function,
			 * we can't optimize kprobe in this function.
			 */
			return 0;
		recovered_insn = recover_probed_instruction(buf, addr);
		if (!recovered_insn)
			return 0;
		kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
		insn_get_length(&insn);
		/* Another subsystem puts a breakpoint */
		if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
			return 0;
		/* Recover address */
		insn.kaddr = (void *)addr;
		insn.next_byte = (void *)(addr + insn.length);
		/* Check any instructions don't jump into target */
		if (insn_is_indirect_jump(&insn) ||
		    insn_jump_into_range(&insn, paddr + INT3_SIZE,
					 RELATIVE_ADDR_SIZE))
			return 0;
		addr += insn.length;
	}

	return 1;
}

/* Check optimized_kprobe can actually be optimized. */
int arch_check_optimized_kprobe(struct optimized_kprobe *op)
{
	int i;
	struct kprobe *p;

	for (i = 1; i < op->optinsn.size; i++) {
		p = get_kprobe(op->kp.addr + i);
		if (p && !kprobe_disabled(p))
			return -EEXIST;
	}

	return 0;
}

/* Check the addr is within the optimized instructions. */
int arch_within_optimized_kprobe(struct optimized_kprobe *op,
				 unsigned long addr)
{
	return ((unsigned long)op->kp.addr <= addr &&
		(unsigned long)op->kp.addr + op->optinsn.size > addr);
}

/* Free optimized instruction slot */
static
void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
{
	if (op->optinsn.insn) {
		free_optinsn_slot(op->optinsn.insn, dirty);
		op->optinsn.insn = NULL;
		op->optinsn.size = 0;
	}
}

void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
{
	__arch_remove_optimized_kprobe(op, 1);
}

/*
 * Copy replacing target instructions
 * Target instructions MUST be relocatable (checked inside)
 * This is called when new aggr(opt)probe is allocated or reused.
 */
int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
				  struct kprobe *__unused)
{
	u8 *buf;
	int ret;
	long rel;

	if (!can_optimize((unsigned long)op->kp.addr))
		return -EILSEQ;

	op->optinsn.insn = get_optinsn_slot();
	if (!op->optinsn.insn)
		return -ENOMEM;

	/*
	 * Verify if the address gap is in 2GB range, because this uses
	 * a relative jump.
	 */
	rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
	if (abs(rel) > 0x7fffffff) {
		__arch_remove_optimized_kprobe(op, 0);
		return -ERANGE;
	}

	buf = (u8 *)op->optinsn.insn;

	/* Copy instructions into the out-of-line buffer */
	ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
	if (ret < 0) {
		__arch_remove_optimized_kprobe(op, 0);
		return ret;
	}
	op->optinsn.size = ret;

	/* Copy arch-dep-instance from template */
	memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);

	/* Set probe information */
	synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);

	/* Set probe function call */
	synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);

	/* Set returning jmp instruction at the tail of out-of-line buffer */
	synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
			   (u8 *)op->kp.addr + op->optinsn.size);

	flush_icache_range((unsigned long) buf,
			   (unsigned long) buf + TMPL_END_IDX +
			   op->optinsn.size + RELATIVEJUMP_SIZE);
	return 0;
}

/*
 * Replace breakpoints (int3) with relative jumps.
 * Caller must call with locking kprobe_mutex and text_mutex.
 */
void arch_optimize_kprobes(struct list_head *oplist)
{
	struct optimized_kprobe *op, *tmp;
	u8 insn_buf[RELATIVEJUMP_SIZE];

	list_for_each_entry_safe(op, tmp, oplist, list) {
		s32 rel = (s32)((long)op->optinsn.insn -
			((long)op->kp.addr + RELATIVEJUMP_SIZE));

		WARN_ON(kprobe_disabled(&op->kp));

		/* Backup instructions which will be replaced by jump address */
		memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
		       RELATIVE_ADDR_SIZE);

		insn_buf[0] = RELATIVEJUMP_OPCODE;
		*(s32 *)(&insn_buf[1]) = rel;

		text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
			     op->optinsn.insn);

		list_del_init(&op->list);
	}
}

/* Replace a relative jump with a breakpoint (int3).  */
void arch_unoptimize_kprobe(struct optimized_kprobe *op)
{
	u8 insn_buf[RELATIVEJUMP_SIZE];

	/* Set int3 to first byte for kprobes */
	insn_buf[0] = BREAKPOINT_INSTRUCTION;
	memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
	text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
		     op->optinsn.insn);
}

/*
 * Recover original instructions and breakpoints from relative jumps.
 * Caller must call with locking kprobe_mutex.
 */
extern void arch_unoptimize_kprobes(struct list_head *oplist,
				    struct list_head *done_list)
{
	struct optimized_kprobe *op, *tmp;

	list_for_each_entry_safe(op, tmp, oplist, list) {
		arch_unoptimize_kprobe(op);
		list_move(&op->list, done_list);
	}
}

int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter)
{
	struct optimized_kprobe *op;

	if (p->flags & KPROBE_FLAG_OPTIMIZED) {
		/* This kprobe is really able to run optimized path. */
		op = container_of(p, struct optimized_kprobe, kp);
		/* Detour through copied instructions */
		regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
		if (!reenter)
			reset_current_kprobe();
		preempt_enable_no_resched();
		return 1;
	}
	return 0;
}
NOKPROBE_SYMBOL(setup_detour_execution);
Commit	Line	Data
3f33ab1c MH	1	/*
	2	* Kernel Probes Jump Optimization (Optprobes)
	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, 2002, 2004
	19	* Copyright (C) Hitachi Ltd., 2012
	20	*/
	21	#include <linux/kprobes.h>
	22	#include <linux/ptrace.h>
	23	#include <linux/string.h>
	24	#include <linux/slab.h>
	25	#include <linux/hardirq.h>
	26	#include <linux/preempt.h>
744c193e	27	#include <linux/extable.h>
3f33ab1c MH	28	#include <linux/kdebug.h>
	29	#include <linux/kallsyms.h>
	30	#include <linux/ftrace.h>
	31
35de5b06	32	#include <asm/text-patching.h>
3f33ab1c MH	33	#include <asm/cacheflush.h>
	34	#include <asm/desc.h>
	35	#include <asm/pgtable.h>
7c0f6ba6	36	#include <linux/uaccess.h>
3f33ab1c MH	37	#include <asm/alternative.h>
	38	#include <asm/insn.h>
	39	#include <asm/debugreg.h>
	40
f684199f	41	#include "common.h"
3f33ab1c MH	42
	43	unsigned long __recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
	44	{
	45	struct optimized_kprobe *op;
	46	struct kprobe *kp;
	47	long offs;
	48	int i;
	49
	50	for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
	51	kp = get_kprobe((void *)addr - i);
	52	/* This function only handles jump-optimized kprobe */
	53	if (kp && kprobe_optimized(kp)) {
	54	op = container_of(kp, struct optimized_kprobe, kp);
	55	/* If op->list is not empty, op is under optimizing */
	56	if (list_empty(&op->list))
	57	goto found;
	58	}
	59	}
	60
	61	return addr;
	62	found:
	63	/*
	64	* If the kprobe can be optimized, original bytes which can be
	65	* overwritten by jump destination address. In this case, original
	66	* bytes must be recovered from op->optinsn.copied_insn buffer.
	67	*/
	68	memcpy(buf, (void )addr, MAX_INSN_SIZE sizeof(kprobe_opcode_t));
	69	if (addr == (unsigned long)kp->addr) {
	70	buf[0] = kp->opcode;
	71	memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
	72	} else {
	73	offs = addr - (unsigned long)kp->addr - 1;
	74	memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
	75	}
	76
	77	return (unsigned long)buf;
	78	}
	79
	80	/* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */
7ec8a97a	81	static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
3f33ab1c MH	82	{
	83	#ifdef CONFIG_X86_64
	84	*addr++ = 0x48;
	85	*addr++ = 0xbf;
	86	#else
	87	*addr++ = 0xb8;
	88	#endif
	89	(unsigned long )addr = val;
	90	}
	91
04bb591c	92	asm (
3f33ab1c MH	93	".global optprobe_template_entry\n"
	94	"optprobe_template_entry:\n"
	95	#ifdef CONFIG_X86_64
	96	/* We don't bother saving the ss register */
	97	" pushq %rsp\n"
	98	" pushfq\n"
	99	SAVE_REGS_STRING
	100	" movq %rsp, %rsi\n"
	101	".global optprobe_template_val\n"
	102	"optprobe_template_val:\n"
	103	ASM_NOP5
	104	ASM_NOP5
	105	".global optprobe_template_call\n"
	106	"optprobe_template_call:\n"
	107	ASM_NOP5
	108	/* Move flags to rsp */
	109	" movq 144(%rsp), %rdx\n"
	110	" movq %rdx, 152(%rsp)\n"
	111	RESTORE_REGS_STRING
	112	/* Skip flags entry */
	113	" addq $8, %rsp\n"
	114	" popfq\n"
	115	#else /* CONFIG_X86_32 */
	116	" pushf\n"
	117	SAVE_REGS_STRING
	118	" movl %esp, %edx\n"
	119	".global optprobe_template_val\n"
	120	"optprobe_template_val:\n"
	121	ASM_NOP5
	122	".global optprobe_template_call\n"
	123	"optprobe_template_call:\n"
	124	ASM_NOP5
	125	RESTORE_REGS_STRING
	126	" addl $4, %esp\n" /* skip cs */
	127	" popf\n"
	128	#endif
	129	".global optprobe_template_end\n"
	130	"optprobe_template_end:\n");
3f33ab1c MH	131
	132	#define TMPL_MOVE_IDX \
	133	((long)&optprobe_template_val - (long)&optprobe_template_entry)
	134	#define TMPL_CALL_IDX \
	135	((long)&optprobe_template_call - (long)&optprobe_template_entry)
	136	#define TMPL_END_IDX \
	137	((long)&optprobe_template_end - (long)&optprobe_template_entry)
	138
	139	#define INT3_SIZE sizeof(kprobe_opcode_t)
	140
	141	/* Optimized kprobe call back function: called from optinsn */
9326638c MH	142	static void
9326638c MH	143	optimized_callback(struct optimized_kprobe op, struct pt_regs regs)
3f33ab1c MH	144	{
	145	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
	146	unsigned long flags;
	147
	148	/* This is possible if op is under delayed unoptimizing */
	149	if (kprobe_disabled(&op->kp))
	150	return;
	151
	152	local_irq_save(flags);
	153	if (kprobe_running()) {
	154	kprobes_inc_nmissed_count(&op->kp);
	155	} else {
	156	/* Save skipped registers */
	157	#ifdef CONFIG_X86_64
	158	regs->cs = __KERNEL_CS;
	159	#else
	160	regs->cs = __KERNEL_CS \| get_kernel_rpl();
	161	regs->gs = 0;
	162	#endif
	163	regs->ip = (unsigned long)op->kp.addr + INT3_SIZE;
	164	regs->orig_ax = ~0UL;
	165
	166	__this_cpu_write(current_kprobe, &op->kp);
	167	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
	168	opt_pre_handler(&op->kp, regs);
	169	__this_cpu_write(current_kprobe, NULL);
	170	}
	171	local_irq_restore(flags);
	172	}
9326638c	173	NOKPROBE_SYMBOL(optimized_callback);
3f33ab1c	174
7ec8a97a	175	static int copy_optimized_instructions(u8 dest, u8 src)
3f33ab1c MH	176	{
	177	int len = 0, ret;
	178
	179	while (len < RELATIVEJUMP_SIZE) {
	180	ret = __copy_instruction(dest + len, src + len);
	181	if (!ret \|\| !can_boost(dest + len))
	182	return -EINVAL;
	183	len += ret;
	184	}
	185	/* Check whether the address range is reserved */
	186	if (ftrace_text_reserved(src, src + len - 1) \|\|
	187	alternatives_text_reserved(src, src + len - 1) \|\|
	188	jump_label_text_reserved(src, src + len - 1))
	189	return -EBUSY;
	190
	191	return len;
	192	}
	193
	194	/* Check whether insn is indirect jump */
7ec8a97a	195	static int insn_is_indirect_jump(struct insn *insn)
3f33ab1c MH	196	{
	197	return ((insn->opcode.bytes[0] == 0xff &&
	198	(X86_MODRM_REG(insn->modrm.value) & 6) == 4) \|\| /* Jump */
	199	insn->opcode.bytes[0] == 0xea); /* Segment based jump */
	200	}
	201
	202	/* Check whether insn jumps into specified address range */
	203	static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
	204	{
	205	unsigned long target = 0;
	206
	207	switch (insn->opcode.bytes[0]) {
	208	case 0xe0: /* loopne */
	209	case 0xe1: /* loope */
	210	case 0xe2: /* loop */
	211	case 0xe3: /* jcxz */
	212	case 0xe9: /* near relative jump */
	213	case 0xeb: /* short relative jump */
	214	break;
	215	case 0x0f:
	216	if ((insn->opcode.bytes[1] & 0xf0) == 0x80) /* jcc near */
	217	break;
	218	return 0;
	219	default:
	220	if ((insn->opcode.bytes[0] & 0xf0) == 0x70) /* jcc short */
	221	break;
	222	return 0;
	223	}
	224	target = (unsigned long)insn->next_byte + insn->immediate.value;
	225
	226	return (start <= target && target <= start + len);
	227	}
	228
	229	/* Decode whole function to ensure any instructions don't jump into target */
7ec8a97a	230	static int can_optimize(unsigned long paddr)
3f33ab1c MH	231	{
	232	unsigned long addr, size = 0, offset = 0;
	233	struct insn insn;
	234	kprobe_opcode_t buf[MAX_INSN_SIZE];
	235
	236	/* Lookup symbol including addr */
	237	if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
	238	return 0;
	239
	240	/*
	241	* Do not optimize in the entry code due to the unstable
	242	* stack handling.
	243	*/
	244	if ((paddr >= (unsigned long)__entry_text_start) &&
	245	(paddr < (unsigned long)__entry_text_end))
	246	return 0;
	247
	248	/* Check there is enough space for a relative jump. */
	249	if (size - offset < RELATIVEJUMP_SIZE)
	250	return 0;
	251
	252	/* Decode instructions */
	253	addr = paddr - offset;
	254	while (addr < paddr - offset + size) { /* Decode until function end */
6ba48ff4	255	unsigned long recovered_insn;
3f33ab1c MH	256	if (search_exception_tables(addr))
	257	/*
	258	* Since some fixup code will jumps into this function,
	259	* we can't optimize kprobe in this function.
	260	*/
	261	return 0;
6ba48ff4	262	recovered_insn = recover_probed_instruction(buf, addr);
2a6730c8 PM	263	if (!recovered_insn)
2a6730c8 PM	264	return 0;
6ba48ff4	265	kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
3f33ab1c MH	266	insn_get_length(&insn);
	267	/* Another subsystem puts a breakpoint */
	268	if (insn.opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
	269	return 0;
	270	/* Recover address */
	271	insn.kaddr = (void *)addr;
	272	insn.next_byte = (void *)(addr + insn.length);
	273	/* Check any instructions don't jump into target */
	274	if (insn_is_indirect_jump(&insn) \|\|
	275	insn_jump_into_range(&insn, paddr + INT3_SIZE,
	276	RELATIVE_ADDR_SIZE))
	277	return 0;
	278	addr += insn.length;
	279	}
	280
	281	return 1;
	282	}
	283
	284	/* Check optimized_kprobe can actually be optimized. */
7ec8a97a	285	int arch_check_optimized_kprobe(struct optimized_kprobe *op)
3f33ab1c MH	286	{
	287	int i;
	288	struct kprobe *p;
	289
	290	for (i = 1; i < op->optinsn.size; i++) {
	291	p = get_kprobe(op->kp.addr + i);
	292	if (p && !kprobe_disabled(p))
	293	return -EEXIST;
	294	}
	295
	296	return 0;
	297	}
	298
	299	/* Check the addr is within the optimized instructions. */
7ec8a97a MH	300	int arch_within_optimized_kprobe(struct optimized_kprobe *op,
7ec8a97a MH	301	unsigned long addr)
3f33ab1c MH	302	{
	303	return ((unsigned long)op->kp.addr <= addr &&
	304	(unsigned long)op->kp.addr + op->optinsn.size > addr);
	305	}
	306
	307	/* Free optimized instruction slot */
7ec8a97a	308	static
3f33ab1c MH	309	void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
	310	{
	311	if (op->optinsn.insn) {
	312	free_optinsn_slot(op->optinsn.insn, dirty);
	313	op->optinsn.insn = NULL;
	314	op->optinsn.size = 0;
	315	}
	316	}
	317
7ec8a97a	318	void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
3f33ab1c MH	319	{
	320	__arch_remove_optimized_kprobe(op, 1);
	321	}
	322
	323	/*
	324	* Copy replacing target instructions
	325	* Target instructions MUST be relocatable (checked inside)
	326	* This is called when new aggr(opt)probe is allocated or reused.
	327	*/
cbf6ab52 MH	328	int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
cbf6ab52 MH	329	struct kprobe *__unused)
3f33ab1c MH	330	{
	331	u8 *buf;
	332	int ret;
	333	long rel;
	334
	335	if (!can_optimize((unsigned long)op->kp.addr))
	336	return -EILSEQ;
	337
	338	op->optinsn.insn = get_optinsn_slot();
	339	if (!op->optinsn.insn)
	340	return -ENOMEM;
	341
	342	/*
	343	* Verify if the address gap is in 2GB range, because this uses
	344	* a relative jump.
	345	*/
	346	rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
256aae5e WN	347	if (abs(rel) > 0x7fffffff) {
256aae5e WN	348	__arch_remove_optimized_kprobe(op, 0);
3f33ab1c	349	return -ERANGE;
256aae5e	350	}
3f33ab1c MH	351
	352	buf = (u8 *)op->optinsn.insn;
	353
	354	/* Copy instructions into the out-of-line buffer */
	355	ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
	356	if (ret < 0) {
	357	__arch_remove_optimized_kprobe(op, 0);
	358	return ret;
	359	}
	360	op->optinsn.size = ret;
	361
	362	/* Copy arch-dep-instance from template */
	363	memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
	364
	365	/* Set probe information */
	366	synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);
	367
	368	/* Set probe function call */
	369	synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
	370
	371	/* Set returning jmp instruction at the tail of out-of-line buffer */
	372	synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
	373	(u8 *)op->kp.addr + op->optinsn.size);
	374
	375	flush_icache_range((unsigned long) buf,
	376	(unsigned long) buf + TMPL_END_IDX +
	377	op->optinsn.size + RELATIVEJUMP_SIZE);
	378	return 0;
	379	}
	380
3f33ab1c MH	381	/*
	382	* Replace breakpoints (int3) with relative jumps.
	383	* Caller must call with locking kprobe_mutex and text_mutex.
	384	*/
7ec8a97a	385	void arch_optimize_kprobes(struct list_head *oplist)
3f33ab1c MH	386	{
3f33ab1c MH	387	struct optimized_kprobe op, tmp;
a7b0133e	388	u8 insn_buf[RELATIVEJUMP_SIZE];
3f33ab1c MH	389
3f33ab1c MH	390	list_for_each_entry_safe(op, tmp, oplist, list) {
a7b0133e MH	391	s32 rel = (s32)((long)op->optinsn.insn -
	392	((long)op->kp.addr + RELATIVEJUMP_SIZE));
	393
3f33ab1c	394	WARN_ON(kprobe_disabled(&op->kp));
a7b0133e MH	395
	396	/* Backup instructions which will be replaced by jump address */
	397	memcpy(op->optinsn.copied_insn, op->kp.addr + INT3_SIZE,
	398	RELATIVE_ADDR_SIZE);
	399
	400	insn_buf[0] = RELATIVEJUMP_OPCODE;
	401	(s32 )(&insn_buf[1]) = rel;
	402
	403	text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
	404	op->optinsn.insn);
	405
3f33ab1c	406	list_del_init(&op->list);
3f33ab1c	407	}
3f33ab1c MH	408	}
3f33ab1c MH	409
a7b0133e	410	/* Replace a relative jump with a breakpoint (int3). */
7ec8a97a	411	void arch_unoptimize_kprobe(struct optimized_kprobe *op)
3f33ab1c	412	{
a7b0133e MH	413	u8 insn_buf[RELATIVEJUMP_SIZE];
a7b0133e MH	414
3f33ab1c MH	415	/* Set int3 to first byte for kprobes */
	416	insn_buf[0] = BREAKPOINT_INSTRUCTION;
	417	memcpy(insn_buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
a7b0133e MH	418	text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
a7b0133e MH	419	op->optinsn.insn);
3f33ab1c MH	420	}
	421
	422	/*
	423	* Recover original instructions and breakpoints from relative jumps.
	424	* Caller must call with locking kprobe_mutex.
	425	*/
	426	extern void arch_unoptimize_kprobes(struct list_head *oplist,
	427	struct list_head *done_list)
	428	{
	429	struct optimized_kprobe op, tmp;
3f33ab1c MH	430
3f33ab1c MH	431	list_for_each_entry_safe(op, tmp, oplist, list) {
a7b0133e	432	arch_unoptimize_kprobe(op);
3f33ab1c	433	list_move(&op->list, done_list);
3f33ab1c	434	}
3f33ab1c MH	435	}
3f33ab1c MH	436
9326638c	437	int setup_detour_execution(struct kprobe p, struct pt_regs regs, int reenter)
3f33ab1c MH	438	{
	439	struct optimized_kprobe *op;
	440
	441	if (p->flags & KPROBE_FLAG_OPTIMIZED) {
	442	/* This kprobe is really able to run optimized path. */
	443	op = container_of(p, struct optimized_kprobe, kp);
	444	/* Detour through copied instructions */
	445	regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX;
	446	if (!reenter)
	447	reset_current_kprobe();
	448	preempt_enable_no_resched();
	449	return 1;
	450	}
	451	return 0;
	452	}
9326638c	453	NOKPROBE_SYMBOL(setup_detour_execution);