[mirror_ubuntu-hirsute-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/module.h>
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
#include <linux/ftrace.h>

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