/*
* 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 __kprobes 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 __kprobes 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);
}
static int __kprobes 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 __kprobes 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 __kprobes 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 */
if (search_exception_tables(addr))
/*
* Since some fixup code will jumps into this function,
* we can't optimize kprobe in this function.
*/
return 0;
kernel_insn_init(&insn, (void *)recover_probed_instruction(buf, addr));
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 __kprobes 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 __kprobes
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 __kprobes
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 __kprobes 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 __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
{
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)
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 __kprobes 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 __kprobes 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 __kprobes
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;
}