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linux/arch/x86/kernel/kprobes.c
Srinivasa D S ef53d9c5e4 kprobes: improve kretprobe scalability with hashed locking 
Currently list of kretprobe instances are stored in kretprobe object (as
used_instances,free_instances) and in kretprobe hash table.  We have one
global kretprobe lock to serialise the access to these lists.  This causes
only one kretprobe handler to execute at a time.  Hence affects system
performance, particularly on SMP systems and when return probe is set on
lot of functions (like on all systemcalls).

Solution proposed here gives fine-grain locks that performs better on SMP
system compared to present kretprobe implementation.

Solution:

 1) Instead of having one global lock to protect kretprobe instances
    present in kretprobe object and kretprobe hash table.  We will have
    two locks, one lock for protecting kretprobe hash table and another
    lock for kretporbe object.

 2) We hold lock present in kretprobe object while we modify kretprobe
    instance in kretprobe object and we hold per-hash-list lock while
    modifying kretprobe instances present in that hash list.  To prevent
    deadlock, we never grab a per-hash-list lock while holding a kretprobe
    lock.

 3) We can remove used_instances from struct kretprobe, as we can
    track used instances of kretprobe instances using kretprobe hash
    table.

Time duration for kernel compilation ("make -j 8") on a 8-way ppc64 system
with return probes set on all systemcalls looks like this.

cacheline              non-cacheline             Un-patched kernel
aligned patch 	       aligned patch
===============================================================================
real    9m46.784s       9m54.412s                  10m2.450s
user    40m5.715s       40m7.142s                  40m4.273s
sys     2m57.754s       2m58.583s                  3m17.430s
===========================================================

Time duration for kernel compilation ("make -j 8) on the same system, when
kernel is not probed.
=========================
real    9m26.389s
user    40m8.775s
sys     2m7.283s
=========================

Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com>
Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-25 10:53:30 -07:00

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/*
* Kernel Probes (KProbes)
*
* 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
*
* 2002-Oct Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
* Probes initial implementation ( includes contributions from
* Rusty Russell).
* 2004-July Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
* interface to access function arguments.
* 2004-Oct Jim Keniston <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
* <prasanna@in.ibm.com> adapted for x86_64 from i386.
* 2005-Mar Roland McGrath <roland@redhat.com>
* Fixed to handle %rip-relative addressing mode correctly.
* 2005-May Hien Nguyen <hien@us.ibm.com>, Jim Keniston
* <jkenisto@us.ibm.com> and Prasanna S Panchamukhi
* <prasanna@in.ibm.com> added function-return probes.
* 2005-May Rusty Lynch <rusty.lynch@intel.com>
* Added function return probes functionality
* 2006-Feb Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp> added
* kprobe-booster and kretprobe-booster for i386.
* 2007-Dec Masami Hiramatsu <mhiramat@redhat.com> added kprobe-booster
* and kretprobe-booster for x86-64
* 2007-Dec Masami Hiramatsu <mhiramat@redhat.com>, Arjan van de Ven
* <arjan@infradead.org> and Jim Keniston <jkenisto@us.ibm.com>
* unified x86 kprobes code.
*/
#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 <asm/cacheflush.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/alternative.h>
void jprobe_return_end(void);
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
#ifdef CONFIG_X86_64
#define stack_addr(regs) ((unsigned long *)regs->sp)
#else
/*
* "&regs->sp" looks wrong, but it's correct for x86_32. x86_32 CPUs
* don't save the ss and esp registers if the CPU is already in kernel
* mode when it traps. So for kprobes, regs->sp and regs->ss are not
* the [nonexistent] saved stack pointer and ss register, but rather
* the top 8 bytes of the pre-int3 stack. So &regs->sp happens to
* point to the top of the pre-int3 stack.
*/
#define stack_addr(regs) ((unsigned long *)&regs->sp)
#endif
#define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
(b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) | \
(b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) | \
(bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf)) \
<< (row % 32))
/*
* Undefined/reserved opcodes, conditional jump, Opcode Extension
* Groups, and some special opcodes can not boost.
*/
static const u32 twobyte_is_boostable[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ---------------------------------------------- */
W(0x00, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0) | /* 00 */
W(0x10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 10 */
W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 20 */
W(0x30, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 30 */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 40 */
W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1) | /* 60 */
W(0x70, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) , /* 70 */
W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 80 */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 90 */
W(0xa0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* a0 */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) , /* b0 */
W(0xc0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* c0 */
W(0xd0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) , /* d0 */
W(0xe0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1) | /* e0 */
W(0xf0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0) /* f0 */
/* ----------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
static const u32 onebyte_has_modrm[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ----------------------------------------------- */
W(0x00, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* 00 */
W(0x10, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) , /* 10 */
W(0x20, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) | /* 20 */
W(0x30, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0) , /* 30 */
W(0x40, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 40 */
W(0x50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 50 */
W(0x60, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0) | /* 60 */
W(0x70, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 70 */
W(0x80, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 80 */
W(0x90, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 90 */
W(0xa0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* a0 */
W(0xb0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* b0 */
W(0xc0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0) | /* c0 */
W(0xd0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1) , /* d0 */
W(0xe0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* e0 */
W(0xf0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1) /* f0 */
/* ----------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
static const u32 twobyte_has_modrm[256 / 32] = {
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
/* ----------------------------------------------- */
W(0x00, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1) | /* 0f */
W(0x10, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0) , /* 1f */
W(0x20, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1) | /* 2f */
W(0x30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) , /* 3f */
W(0x40, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 4f */
W(0x50, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 5f */
W(0x60, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* 6f */
W(0x70, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1) , /* 7f */
W(0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) | /* 8f */
W(0x90, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* 9f */
W(0xa0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1) | /* af */
W(0xb0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1) , /* bf */
W(0xc0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0) | /* cf */
W(0xd0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) , /* df */
W(0xe0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1) | /* ef */
W(0xf0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0) /* ff */
/* ----------------------------------------------- */
/* 0 1 2 3 4 5 6 7 8 9 a b c d e f */
};
#undef W
struct kretprobe_blackpoint kretprobe_blacklist[] = {
{"__switch_to", }, /* This function switches only current task, but
doesn't switch kernel stack.*/
{NULL, NULL} /* Terminator */
};
const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
/* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
static void __kprobes set_jmp_op(void *from, void *to)
{
struct __arch_jmp_op {
char op;
s32 raddr;
} __attribute__((packed)) * jop;
jop = (struct __arch_jmp_op *)from;
jop->raddr = (s32)((long)(to) - ((long)(from) + 5));
jop->op = RELATIVEJUMP_INSTRUCTION;
}
/*
* Check for the REX prefix which can only exist on X86_64
* X86_32 always returns 0
*/
static int __kprobes is_REX_prefix(kprobe_opcode_t *insn)
{
#ifdef CONFIG_X86_64
if ((*insn & 0xf0) == 0x40)
return 1;
#endif
return 0;
}
/*
* Returns non-zero if opcode is boostable.
* RIP relative instructions are adjusted at copying time in 64 bits mode
*/
static int __kprobes can_boost(kprobe_opcode_t *opcodes)
{
kprobe_opcode_t opcode;
kprobe_opcode_t *orig_opcodes = opcodes;
retry:
if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
return 0;
opcode = *(opcodes++);
/* 2nd-byte opcode */
if (opcode == 0x0f) {
if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
return 0;
return test_bit(*opcodes,
(unsigned long *)twobyte_is_boostable);
}
switch (opcode & 0xf0) {
#ifdef CONFIG_X86_64
case 0x40:
goto retry; /* REX prefix is boostable */
#endif
case 0x60:
if (0x63 < opcode && opcode < 0x67)
goto retry; /* prefixes */
/* can't boost Address-size override and bound */
return (opcode != 0x62 && opcode != 0x67);
case 0x70:
return 0; /* can't boost conditional jump */
case 0xc0:
/* can't boost software-interruptions */
return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
case 0xd0:
/* can boost AA* and XLAT */
return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
case 0xe0:
/* can boost in/out and absolute jmps */
return ((opcode & 0x04) || opcode == 0xea);
case 0xf0:
if ((opcode & 0x0c) == 0 && opcode != 0xf1)
goto retry; /* lock/rep(ne) prefix */
/* clear and set flags are boostable */
return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
default:
/* segment override prefixes are boostable */
if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e)
goto retry; /* prefixes */
/* CS override prefix and call are not boostable */
return (opcode != 0x2e && opcode != 0x9a);
}
}
/*
* Returns non-zero if opcode modifies the interrupt flag.
*/
static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
{
switch (*insn) {
case 0xfa: /* cli */
case 0xfb: /* sti */
case 0xcf: /* iret/iretd */
case 0x9d: /* popf/popfd */
return 1;
}
/*
* on X86_64, 0x40-0x4f are REX prefixes so we need to look
* at the next byte instead.. but of course not recurse infinitely
*/
if (is_REX_prefix(insn))
return is_IF_modifier(++insn);
return 0;
}
/*
* Adjust the displacement if the instruction uses the %rip-relative
* addressing mode.
* If it does, Return the address of the 32-bit displacement word.
* If not, return null.
* Only applicable to 64-bit x86.
*/
static void __kprobes fix_riprel(struct kprobe *p)
{
#ifdef CONFIG_X86_64
u8 *insn = p->ainsn.insn;
s64 disp;
int need_modrm;
/* Skip legacy instruction prefixes. */
while (1) {
switch (*insn) {
case 0x66:
case 0x67:
case 0x2e:
case 0x3e:
case 0x26:
case 0x64:
case 0x65:
case 0x36:
case 0xf0:
case 0xf3:
case 0xf2:
++insn;
continue;
}
break;
}
/* Skip REX instruction prefix. */
if (is_REX_prefix(insn))
++insn;
if (*insn == 0x0f) {
/* Two-byte opcode. */
++insn;
need_modrm = test_bit(*insn,
(unsigned long *)twobyte_has_modrm);
} else
/* One-byte opcode. */
need_modrm = test_bit(*insn,
(unsigned long *)onebyte_has_modrm);
if (need_modrm) {
u8 modrm = *++insn;
if ((modrm & 0xc7) == 0x05) {
/* %rip+disp32 addressing mode */
/* Displacement follows ModRM byte. */
++insn;
/*
* The copied instruction uses the %rip-relative
* addressing mode. Adjust the displacement for the
* difference between the original location of this
* instruction and the location of the copy that will
* actually be run. The tricky bit here is making sure
* that the sign extension happens correctly in this
* calculation, since we need a signed 32-bit result to
* be sign-extended to 64 bits when it's added to the
* %rip value and yield the same 64-bit result that the
* sign-extension of the original signed 32-bit
* displacement would have given.
*/
disp = (u8 *) p->addr + *((s32 *) insn) -
(u8 *) p->ainsn.insn;
BUG_ON((s64) (s32) disp != disp); /* Sanity check. */
*(s32 *)insn = (s32) disp;
}
}
#endif
}
static void __kprobes arch_copy_kprobe(struct kprobe *p)
{
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
fix_riprel(p);
if (can_boost(p->addr))
p->ainsn.boostable = 0;
else
p->ainsn.boostable = -1;
p->opcode = *p->addr;
}
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
/* insn: must be on special executable page on x86. */
p->ainsn.insn = get_insn_slot();
if (!p->ainsn.insn)
return -ENOMEM;
arch_copy_kprobe(p);
return 0;
}
void __kprobes arch_arm_kprobe(struct kprobe *p)
{
text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
}
void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
text_poke(p->addr, &p->opcode, 1);
}
void __kprobes arch_remove_kprobe(struct kprobe *p)
{
mutex_lock(&kprobe_mutex);
free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1));
mutex_unlock(&kprobe_mutex);
}
static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
kcb->prev_kprobe.kp = kprobe_running();
kcb->prev_kprobe.status = kcb->kprobe_status;
kcb->prev_kprobe.old_flags = kcb->kprobe_old_flags;
kcb->prev_kprobe.saved_flags = kcb->kprobe_saved_flags;
}
static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
kcb->kprobe_status = kcb->prev_kprobe.status;
kcb->kprobe_old_flags = kcb->prev_kprobe.old_flags;
kcb->kprobe_saved_flags = kcb->prev_kprobe.saved_flags;
}
static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
__get_cpu_var(current_kprobe) = p;
kcb->kprobe_saved_flags = kcb->kprobe_old_flags
= (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
if (is_IF_modifier(p->ainsn.insn))
kcb->kprobe_saved_flags &= ~X86_EFLAGS_IF;
}
static void __kprobes clear_btf(void)
{
if (test_thread_flag(TIF_DEBUGCTLMSR))
update_debugctlmsr(0);
}
static void __kprobes restore_btf(void)
{
if (test_thread_flag(TIF_DEBUGCTLMSR))
update_debugctlmsr(current->thread.debugctlmsr);
}
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
clear_btf();
regs->flags |= X86_EFLAGS_TF;
regs->flags &= ~X86_EFLAGS_IF;
/* single step inline if the instruction is an int3 */
if (p->opcode == BREAKPOINT_INSTRUCTION)
regs->ip = (unsigned long)p->addr;
else
regs->ip = (unsigned long)p->ainsn.insn;
}
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
unsigned long *sara = stack_addr(regs);
ri->ret_addr = (kprobe_opcode_t *) *sara;
/* Replace the return addr with trampoline addr */
*sara = (unsigned long) &kretprobe_trampoline;
}
static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM)
if (p->ainsn.boostable == 1 && !p->post_handler) {
/* Boost up -- we can execute copied instructions directly */
reset_current_kprobe();
regs->ip = (unsigned long)p->ainsn.insn;
preempt_enable_no_resched();
return;
}
#endif
prepare_singlestep(p, regs);
kcb->kprobe_status = KPROBE_HIT_SS;
}
/*
* We have reentered the kprobe_handler(), since another probe was hit while
* within the handler. We save the original kprobes variables and just single
* step on the instruction of the new probe without calling any user handlers.
*/
static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
switch (kcb->kprobe_status) {
case KPROBE_HIT_SSDONE:
#ifdef CONFIG_X86_64
/* TODO: Provide re-entrancy from post_kprobes_handler() and
* avoid exception stack corruption while single-stepping on
* the instruction of the new probe.
*/
arch_disarm_kprobe(p);
regs->ip = (unsigned long)p->addr;
reset_current_kprobe();
preempt_enable_no_resched();
break;
#endif
case KPROBE_HIT_ACTIVE:
save_previous_kprobe(kcb);
set_current_kprobe(p, regs, kcb);
kprobes_inc_nmissed_count(p);
prepare_singlestep(p, regs);
kcb->kprobe_status = KPROBE_REENTER;
break;
case KPROBE_HIT_SS:
if (p == kprobe_running()) {
regs->flags &= ~X86_EFLAGS_TF;
regs->flags |= kcb->kprobe_saved_flags;
return 0;
} else {
/* A probe has been hit in the codepath leading up
* to, or just after, single-stepping of a probed
* instruction. This entire codepath should strictly
* reside in .kprobes.text section. Raise a warning
* to highlight this peculiar case.
*/
}
default:
/* impossible cases */
WARN_ON(1);
return 0;
}
return 1;
}
/*
* Interrupts are disabled on entry as trap3 is an interrupt gate and they
* remain disabled thorough out this function.
*/
static int __kprobes kprobe_handler(struct pt_regs *regs)
{
kprobe_opcode_t *addr;
struct kprobe *p;
struct kprobe_ctlblk *kcb;
addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
if (*addr != BREAKPOINT_INSTRUCTION) {
/*
* The breakpoint instruction was removed right
* after we hit it. Another cpu has removed
* either a probepoint or a debugger breakpoint
* at this address. In either case, no further
* handling of this interrupt is appropriate.
* Back up over the (now missing) int3 and run
* the original instruction.
*/
regs->ip = (unsigned long)addr;
return 1;
}
/*
* We don't want to be preempted for the entire
* duration of kprobe processing. We conditionally
* re-enable preemption at the end of this function,
* and also in reenter_kprobe() and setup_singlestep().
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
p = get_kprobe(addr);
if (p) {
if (kprobe_running()) {
if (reenter_kprobe(p, regs, kcb))
return 1;
} else {
set_current_kprobe(p, regs, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
/*
* If we have no pre-handler or it returned 0, we
* continue with normal processing. If we have a
* pre-handler and it returned non-zero, it prepped
* for calling the break_handler below on re-entry
* for jprobe processing, so get out doing nothing
* more here.
*/
if (!p->pre_handler || !p->pre_handler(p, regs))
setup_singlestep(p, regs, kcb);
return 1;
}
} else if (kprobe_running()) {
p = __get_cpu_var(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
setup_singlestep(p, regs, kcb);
return 1;
}
} /* else: not a kprobe fault; let the kernel handle it */
preempt_enable_no_resched();
return 0;
}
/*
* When a retprobed function returns, this code saves registers and
* calls trampoline_handler() runs, which calls the kretprobe's handler.
*/
static void __used __kprobes kretprobe_trampoline_holder(void)
{
asm volatile (
".global kretprobe_trampoline\n"
"kretprobe_trampoline: \n"
#ifdef CONFIG_X86_64
/* We don't bother saving the ss register */
" pushq %rsp\n"
" pushfq\n"
/*
* Skip cs, ip, orig_ax.
* trampoline_handler() will plug in these values
*/
" subq $24, %rsp\n"
" pushq %rdi\n"
" pushq %rsi\n"
" pushq %rdx\n"
" pushq %rcx\n"
" pushq %rax\n"
" pushq %r8\n"
" pushq %r9\n"
" pushq %r10\n"
" pushq %r11\n"
" pushq %rbx\n"
" pushq %rbp\n"
" pushq %r12\n"
" pushq %r13\n"
" pushq %r14\n"
" pushq %r15\n"
" movq %rsp, %rdi\n"
" call trampoline_handler\n"
/* Replace saved sp with true return address. */
" movq %rax, 152(%rsp)\n"
" popq %r15\n"
" popq %r14\n"
" popq %r13\n"
" popq %r12\n"
" popq %rbp\n"
" popq %rbx\n"
" popq %r11\n"
" popq %r10\n"
" popq %r9\n"
" popq %r8\n"
" popq %rax\n"
" popq %rcx\n"
" popq %rdx\n"
" popq %rsi\n"
" popq %rdi\n"
/* Skip orig_ax, ip, cs */
" addq $24, %rsp\n"
" popfq\n"
#else
" pushf\n"
/*
* Skip cs, ip, orig_ax.
* trampoline_handler() will plug in these values
*/
" subl $12, %esp\n"
" pushl %fs\n"
" pushl %ds\n"
" pushl %es\n"
" pushl %eax\n"
" pushl %ebp\n"
" pushl %edi\n"
" pushl %esi\n"
" pushl %edx\n"
" pushl %ecx\n"
" pushl %ebx\n"
" movl %esp, %eax\n"
" call trampoline_handler\n"
/* Move flags to cs */
" movl 52(%esp), %edx\n"
" movl %edx, 48(%esp)\n"
/* Replace saved flags with true return address. */
" movl %eax, 52(%esp)\n"
" popl %ebx\n"
" popl %ecx\n"
" popl %edx\n"
" popl %esi\n"
" popl %edi\n"
" popl %ebp\n"
" popl %eax\n"
/* Skip ip, orig_ax, es, ds, fs */
" addl $20, %esp\n"
" popf\n"
#endif
" ret\n");
}
/*
* Called from kretprobe_trampoline
*/
static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
{
struct kretprobe_instance *ri = NULL;
struct hlist_head *head, empty_rp;
struct hlist_node *node, *tmp;
unsigned long flags, orig_ret_address = 0;
unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
INIT_HLIST_HEAD(&empty_rp);
kretprobe_hash_lock(current, &head, &flags);
/* fixup registers */
#ifdef CONFIG_X86_64
regs->cs = __KERNEL_CS;
#else
regs->cs = __KERNEL_CS | get_kernel_rpl();
#endif
regs->ip = trampoline_address;
regs->orig_ax = ~0UL;
/*
* It is possible to have multiple instances associated with a given
* task either because multiple functions in the call path have
* return probes installed on them, and/or more then one
* return probe was registered for a target function.
*
* We can handle this because:
* - instances are always pushed into the head of the list
* - when multiple return probes are registered for the same
* function, the (chronologically) first instance's ret_addr
* will be the real return address, and all the rest will
* point to kretprobe_trampoline.
*/
hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
if (ri->task != current)
/* another task is sharing our hash bucket */
continue;
if (ri->rp && ri->rp->handler) {
__get_cpu_var(current_kprobe) = &ri->rp->kp;
get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
ri->rp->handler(ri, regs);
__get_cpu_var(current_kprobe) = NULL;
}
orig_ret_address = (unsigned long)ri->ret_addr;
recycle_rp_inst(ri, &empty_rp);
if (orig_ret_address != trampoline_address)
/*
* This is the real return address. Any other
* instances associated with this task are for
* other calls deeper on the call stack
*/
break;
}
kretprobe_assert(ri, orig_ret_address, trampoline_address);
kretprobe_hash_unlock(current, &flags);
hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
hlist_del(&ri->hlist);
kfree(ri);
}
return (void *)orig_ret_address;
}
/*
* Called after single-stepping. p->addr is the address of the
* instruction whose first byte has been replaced by the "int 3"
* instruction. To avoid the SMP problems that can occur when we
* temporarily put back the original opcode to single-step, we
* single-stepped a copy of the instruction. The address of this
* copy is p->ainsn.insn.
*
* This function prepares to return from the post-single-step
* interrupt. We have to fix up the stack as follows:
*
* 0) Except in the case of absolute or indirect jump or call instructions,
* the new ip is relative to the copied instruction. We need to make
* it relative to the original instruction.
*
* 1) If the single-stepped instruction was pushfl, then the TF and IF
* flags are set in the just-pushed flags, and may need to be cleared.
*
* 2) If the single-stepped instruction was a call, the return address
* that is atop the stack is the address following the copied instruction.
* We need to make it the address following the original instruction.
*
* If this is the first time we've single-stepped the instruction at
* this probepoint, and the instruction is boostable, boost it: add a
* jump instruction after the copied instruction, that jumps to the next
* instruction after the probepoint.
*/
static void __kprobes resume_execution(struct kprobe *p,
struct pt_regs *regs, struct kprobe_ctlblk *kcb)
{
unsigned long *tos = stack_addr(regs);
unsigned long copy_ip = (unsigned long)p->ainsn.insn;
unsigned long orig_ip = (unsigned long)p->addr;
kprobe_opcode_t *insn = p->ainsn.insn;
/*skip the REX prefix*/
if (is_REX_prefix(insn))
insn++;
regs->flags &= ~X86_EFLAGS_TF;
switch (*insn) {
case 0x9c: /* pushfl */
*tos &= ~(X86_EFLAGS_TF | X86_EFLAGS_IF);
*tos |= kcb->kprobe_old_flags;
break;
case 0xc2: /* iret/ret/lret */
case 0xc3:
case 0xca:
case 0xcb:
case 0xcf:
case 0xea: /* jmp absolute -- ip is correct */
/* ip is already adjusted, no more changes required */
p->ainsn.boostable = 1;
goto no_change;
case 0xe8: /* call relative - Fix return addr */
*tos = orig_ip + (*tos - copy_ip);
break;
#ifdef CONFIG_X86_32
case 0x9a: /* call absolute -- same as call absolute, indirect */
*tos = orig_ip + (*tos - copy_ip);
goto no_change;
#endif
case 0xff:
if ((insn[1] & 0x30) == 0x10) {
/*
* call absolute, indirect
* Fix return addr; ip is correct.
* But this is not boostable
*/
*tos = orig_ip + (*tos - copy_ip);
goto no_change;
} else if (((insn[1] & 0x31) == 0x20) ||
((insn[1] & 0x31) == 0x21)) {
/*
* jmp near and far, absolute indirect
* ip is correct. And this is boostable
*/
p->ainsn.boostable = 1;
goto no_change;
}
default:
break;
}
if (p->ainsn.boostable == 0) {
if ((regs->ip > copy_ip) &&
(regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) {
/*
* These instructions can be executed directly if it
* jumps back to correct address.
*/
set_jmp_op((void *)regs->ip,
(void *)orig_ip + (regs->ip - copy_ip));
p->ainsn.boostable = 1;
} else {
p->ainsn.boostable = -1;
}
}
regs->ip += orig_ip - copy_ip;
no_change:
restore_btf();
}
/*
* Interrupts are disabled on entry as trap1 is an interrupt gate and they
* remain disabled thoroughout this function.
*/
static int __kprobes post_kprobe_handler(struct pt_regs *regs)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if (!cur)
return 0;
resume_execution(cur, regs, kcb);
regs->flags |= kcb->kprobe_saved_flags;
if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
kcb->kprobe_status = KPROBE_HIT_SSDONE;
cur->post_handler(cur, regs, 0);
}
/* Restore back the original saved kprobes variables and continue. */
if (kcb->kprobe_status == KPROBE_REENTER) {
restore_previous_kprobe(kcb);
goto out;
}
reset_current_kprobe();
out:
preempt_enable_no_resched();
/*
* if somebody else is singlestepping across a probe point, flags
* will have TF set, in which case, continue the remaining processing
* of do_debug, as if this is not a probe hit.
*/
if (regs->flags & X86_EFLAGS_TF)
return 0;
return 1;
}
int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
switch (kcb->kprobe_status) {
case KPROBE_HIT_SS:
case KPROBE_REENTER:
/*
* We are here because the instruction being single
* stepped caused a page fault. We reset the current
* kprobe and the ip points back to the probe address
* and allow the page fault handler to continue as a
* normal page fault.
*/
regs->ip = (unsigned long)cur->addr;
regs->flags |= kcb->kprobe_old_flags;
if (kcb->kprobe_status == KPROBE_REENTER)
restore_previous_kprobe(kcb);
else
reset_current_kprobe();
preempt_enable_no_resched();
break;
case KPROBE_HIT_ACTIVE:
case KPROBE_HIT_SSDONE:
/*
* We increment the nmissed count for accounting,
* we can also use npre/npostfault count for accounting
* these specific fault cases.
*/
kprobes_inc_nmissed_count(cur);
/*
* We come here because instructions in the pre/post
* handler caused the page_fault, this could happen
* if handler tries to access user space by
* copy_from_user(), get_user() etc. Let the
* user-specified handler try to fix it first.
*/
if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
return 1;
/*
* In case the user-specified fault handler returned
* zero, try to fix up.
*/
if (fixup_exception(regs))
return 1;
/*
* fixup routine could not handle it,
* Let do_page_fault() fix it.
*/
break;
default:
break;
}
return 0;
}
/*
* Wrapper routine for handling exceptions.
*/
int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
unsigned long val, void *data)
{
struct die_args *args = data;
int ret = NOTIFY_DONE;
if (args->regs && user_mode_vm(args->regs))
return ret;
switch (val) {
case DIE_INT3:
if (kprobe_handler(args->regs))
ret = NOTIFY_STOP;
break;
case DIE_DEBUG:
if (post_kprobe_handler(args->regs))
ret = NOTIFY_STOP;
break;
case DIE_GPF:
/*
* To be potentially processing a kprobe fault and to
* trust the result from kprobe_running(), we have
* be non-preemptible.
*/
if (!preemptible() && kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
break;
default:
break;
}
return ret;
}
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
struct jprobe *jp = container_of(p, struct jprobe, kp);
unsigned long addr;
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
kcb->jprobe_saved_regs = *regs;
kcb->jprobe_saved_sp = stack_addr(regs);
addr = (unsigned long)(kcb->jprobe_saved_sp);
/*
* As Linus pointed out, gcc assumes that the callee
* owns the argument space and could overwrite it, e.g.
* tailcall optimization. So, to be absolutely safe
* we also save and restore enough stack bytes to cover
* the argument area.
*/
memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
MIN_STACK_SIZE(addr));
regs->flags &= ~X86_EFLAGS_IF;
trace_hardirqs_off();
regs->ip = (unsigned long)(jp->entry);
return 1;
}
void __kprobes jprobe_return(void)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
asm volatile (
#ifdef CONFIG_X86_64
" xchg %%rbx,%%rsp \n"
#else
" xchgl %%ebx,%%esp \n"
#endif
" int3 \n"
" .globl jprobe_return_end\n"
" jprobe_return_end: \n"
" nop \n"::"b"
(kcb->jprobe_saved_sp):"memory");
}
int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
u8 *addr = (u8 *) (regs->ip - 1);
struct jprobe *jp = container_of(p, struct jprobe, kp);
if ((addr > (u8 *) jprobe_return) &&
(addr < (u8 *) jprobe_return_end)) {
if (stack_addr(regs) != kcb->jprobe_saved_sp) {
struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
printk(KERN_ERR
"current sp %p does not match saved sp %p\n",
stack_addr(regs), kcb->jprobe_saved_sp);
printk(KERN_ERR "Saved registers for jprobe %p\n", jp);
show_registers(saved_regs);
printk(KERN_ERR "Current registers\n");
show_registers(regs);
BUG();
}
*regs = kcb->jprobe_saved_regs;
memcpy((kprobe_opcode_t *)(kcb->jprobe_saved_sp),
kcb->jprobes_stack,
MIN_STACK_SIZE(kcb->jprobe_saved_sp));
preempt_enable_no_resched();
return 1;
}
return 0;
}
int __init arch_init_kprobes(void)
{
return 0;
}
int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
return 0;
}
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