[RFC][Patch 2/2][take3]kprobe: kprobe-booster against 2.6.15-rc5-mm3 for i386

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[RFC][Patch 2/2][take3]kprobe: kprobe-booster against 2.6.15-rc5-mm3 for i386

Masami Hiramatsu
Hi,

Here is a patch of kprobe-booster for i386 arch.

This patch works with kernel preemption. On preemptable kernel,
kprobe-booster works only when the preemption is disabled.

--
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: [hidden email]

 arch/i386/kernel/kprobes.c |   83 +++++++++++++++++++++++++++++++++++++++++++--
 include/asm-i386/kprobes.h |    4 ++
 2 files changed, 85 insertions(+), 2 deletions(-)
diff -Narup a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
--- a/arch/i386/kernel/kprobes.c 2005-12-20 19:57:56.000000000 +0900
+++ b/arch/i386/kernel/kprobes.c 2005-12-20 20:05:01.000000000 +0900
@@ -41,6 +41,49 @@ void jprobe_return_end(void);
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

+/* insert a jmp code */
+static inline void set_jmp_op(void *from, void *to)
+{
+ struct __arch_jmp_op {
+ char op;
+ long raddr;
+ } __attribute__((packed)) *jop;
+ jop = (struct __arch_jmp_op *)from;
+ jop->raddr = (long)(to) - ((long)(from) + 5);
+ jop->op = RELATIVEJUMP_INSTRUCTION;
+}
+
+/*
+ * returns non-zero if opcodes can be boosted.
+ */
+static inline int can_boost(kprobe_opcode_t opcode)
+{
+ switch (opcode & 0xf0 ) {
+ case 0x70:
+ return 0; /* can't boost conditional jump */
+ case 0x90:
+ /* can't boost call and pushf */
+ return opcode != 0x9a && opcode != 0x9c;
+ case 0xc0:
+ /* can't boost undefined opcodes and soft-interruptions */
+ return (0xc1 < opcode && opcode < 0xc6) ||
+ (0xc7 < 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 (may be) jmps */
+ return (0xe3 < opcode && opcode != 0xe8);
+ case 0xf0:
+ /* clear and set flags can be boost */
+ return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
+ default:
+ /* currently, can't boost 2 bytes opcodes */
+ return opcode != 0x0f;
+ }
+}
+
+
 /*
  * returns non-zero if opcode modifies the interrupt flag.
  */
@@ -60,6 +103,11 @@ int __kprobes arch_prepare_kprobe(struct
 {
  memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  p->opcode = *p->addr;
+ if (can_boost(p->opcode)) {
+ p->ainsn.boostable = 0;
+ } else {
+ p->ainsn.boostable = -1;
+ }
  return 0;
 }

@@ -227,6 +275,19 @@ static int __kprobes kprobe_handler(stru
  /* handler has already set things up, so skip ss setup */
  return 1;

+ if (p->ainsn.boostable == 1 &&
+#ifdef CONFIG_PREEMPT
+    preempt_count() != 1 && /* This enables booster when the
+     direct execution path aren't preempted. */
+#endif /* CONFIG_PREEMPT */
+    !p->post_handler && !p->break_handler ) {
+ /* Boost up -- we can execute copied instructions directly */
+ reset_current_kprobe();
+ regs->eip = (unsigned long)&p->ainsn.insn;
+ preempt_enable_no_resched();
+ return 1;
+ }
+
 ss_probe:
  prepare_singlestep(p, regs);
  kcb->kprobe_status = KPROBE_HIT_SS;
@@ -332,6 +393,8 @@ int __kprobes trampoline_probe_handler(s
  * 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.
+ *
+ * This function also checks instruction size for preparing direct execution.
  */
 static void __kprobes resume_execution(struct kprobe *p,
  struct pt_regs *regs, struct kprobe_ctlblk *kcb)
@@ -352,6 +415,7 @@ static void __kprobes resume_execution(s
  case 0xca:
  case 0xea: /* jmp absolute -- eip is correct */
  /* eip is already adjusted, no more changes required */
+ p->ainsn.boostable = 1;
  goto no_change;
  case 0xe8: /* call relative - Fix return addr */
  *tos = orig_eip + (*tos - copy_eip);
@@ -359,18 +423,33 @@ static void __kprobes resume_execution(s
  case 0xff:
  if ((p->ainsn.insn[1] & 0x30) == 0x10) {
  /* call absolute, indirect */
- /* Fix return addr; eip is correct. */
+ /* Fix return addr; eip is correct
+   But this is not boostable */
  *tos = orig_eip + (*tos - copy_eip);
  goto no_change;
  } else if (((p->ainsn.insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
    ((p->ainsn.insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
- /* eip is correct. */
+ /* eip is correct. And this is boostable */
+ p->ainsn.boostable = 1;
  goto no_change;
  }
  default:
  break;
  }

+ if (p->ainsn.boostable == 0) {
+ if ( regs->eip > copy_eip &&
+     (regs->eip - copy_eip) + 5 < MAX_INSN_SIZE) {
+ /* these instructions can be executed directly if it
+ jumps back to correct address. */
+ set_jmp_op((void *)regs->eip,
+   (void *)orig_eip + (regs->eip - copy_eip));
+ p->ainsn.boostable = 1;
+ } else {
+ p->ainsn.boostable = -1;
+ }
+ }
+
  regs->eip = orig_eip + (regs->eip - copy_eip);

        no_change:
diff -Narup a/include/asm-i386/kprobes.h b/include/asm-i386/kprobes.h
--- a/include/asm-i386/kprobes.h 2005-12-20 19:55:51.000000000 +0900
+++ b/include/asm-i386/kprobes.h 2005-12-20 20:03:11.000000000 +0900
@@ -31,6 +31,7 @@ struct pt_regs;

 typedef u8 kprobe_opcode_t;
 #define BREAKPOINT_INSTRUCTION 0xcc
+#define RELATIVEJUMP_INSTRUCTION 0xe9
 #define MAX_INSN_SIZE 16
 #define MAX_STACK_SIZE 64
 #define MIN_STACK_SIZE(ADDR) (((MAX_STACK_SIZE) < \
@@ -48,6 +49,9 @@ void kretprobe_trampoline(void);
 struct arch_specific_insn {
  /* copy of the original instruction */
  kprobe_opcode_t insn[MAX_INSN_SIZE];
+ /* If this flag is not 0, this kprobe can be boost when its
+   post_handler and break_handler is not set. */
+ int boostable;
 };

 struct prev_kprobe {


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Re: [RFC][Patch 2/2][take3]kprobe: kprobe-booster against 2.6.15-rc5-mm3 for i386

Ananth N Mavinakayanahalli-2
On Thu, Dec 22, 2005 at 10:24:04PM +0900, Masami Hiramatsu wrote:
> Hi,
>
> Here is a patch of kprobe-booster for i386 arch.
>
> This patch works with kernel preemption. On preemptable kernel,
> kprobe-booster works only when the preemption is disabled.

I don't know the intricacies of the IA32 instruction set as well as the
opcode tricks you could play. However, some comments (^^^) below.

Ananth

>
> --
> Masami HIRAMATSU
> 2nd Research Dept.
> Hitachi, Ltd., Systems Development Laboratory
> E-mail: [hidden email]
>
>  arch/i386/kernel/kprobes.c |   83 +++++++++++++++++++++++++++++++++++++++++++--
>  include/asm-i386/kprobes.h |    4 ++
>  2 files changed, 85 insertions(+), 2 deletions(-)
> diff -Narup a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
> --- a/arch/i386/kernel/kprobes.c 2005-12-20 19:57:56.000000000 +0900
> +++ b/arch/i386/kernel/kprobes.c 2005-12-20 20:05:01.000000000 +0900
> @@ -41,6 +41,49 @@ void jprobe_return_end(void);
>  DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
>  DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
>
> +/* insert a jmp code */
> +static inline void set_jmp_op(void *from, void *to)
> +{
> + struct __arch_jmp_op {
> + char op;
> + long raddr;
> + } __attribute__((packed)) *jop;
> + jop = (struct __arch_jmp_op *)from;
> + jop->raddr = (long)(to) - ((long)(from) + 5);
> + jop->op = RELATIVEJUMP_INSTRUCTION;
> +}
> +
> +/*
> + * returns non-zero if opcodes can be boosted.
> + */
> +static inline int can_boost(kprobe_opcode_t opcode)
> +{
> + switch (opcode & 0xf0 ) {
> + case 0x70:
> + return 0; /* can't boost conditional jump */
> + case 0x90:
> + /* can't boost call and pushf */
> + return opcode != 0x9a && opcode != 0x9c;
> + case 0xc0:
> + /* can't boost undefined opcodes and soft-interruptions */
> + return (0xc1 < opcode && opcode < 0xc6) ||
> + (0xc7 < 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 (may be) jmps */
> + return (0xe3 < opcode && opcode != 0xe8);
> + case 0xf0:
> + /* clear and set flags can be boost */
> + return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
> + default:
> + /* currently, can't boost 2 bytes opcodes */
> + return opcode != 0x0f;
> + }
> +}
> +
> +
>  /*
>   * returns non-zero if opcode modifies the interrupt flag.
>   */
> @@ -60,6 +103,11 @@ int __kprobes arch_prepare_kprobe(struct
>  {
>   memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
>   p->opcode = *p->addr;
> + if (can_boost(p->opcode)) {
> + p->ainsn.boostable = 0;
> + } else {
> + p->ainsn.boostable = -1;
> + }
>   return 0;
>  }
>
> @@ -227,6 +275,19 @@ static int __kprobes kprobe_handler(stru
>   /* handler has already set things up, so skip ss setup */
>   return 1;
>
> + if (p->ainsn.boostable == 1 &&
> +#ifdef CONFIG_PREEMPT
> +    preempt_count() != 1 && /* This enables booster when the
> +     direct execution path aren't preempted. */
                             ^^^^^
Why is the comparison against an absolute value? preempt_disable/enable()
can be nested and on each such invocation, the count is
incremented/decremented respectively - this number can be 0 or hold
any positive value.

And multiline comments in
        /*
         *
         */
format please

> +#endif /* CONFIG_PREEMPT */
> +    !p->post_handler && !p->break_handler ) {
> + /* Boost up -- we can execute copied instructions directly */
> + reset_current_kprobe();
> + regs->eip = (unsigned long)&p->ainsn.insn;
> + preempt_enable_no_resched();
> + return 1;
> + }
> +
>  ss_probe:
>   prepare_singlestep(p, regs);
>   kcb->kprobe_status = KPROBE_HIT_SS;
> @@ -332,6 +393,8 @@ int __kprobes trampoline_probe_handler(s
>   * 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.
> + *
> + * This function also checks instruction size for preparing direct execution.
>   */
>  static void __kprobes resume_execution(struct kprobe *p,
>   struct pt_regs *regs, struct kprobe_ctlblk *kcb)
> @@ -352,6 +415,7 @@ static void __kprobes resume_execution(s
>   case 0xca:
>   case 0xea: /* jmp absolute -- eip is correct */
>   /* eip is already adjusted, no more changes required */
> + p->ainsn.boostable = 1;
>   goto no_change;
>   case 0xe8: /* call relative - Fix return addr */
>   *tos = orig_eip + (*tos - copy_eip);
> @@ -359,18 +423,33 @@ static void __kprobes resume_execution(s
>   case 0xff:
>   if ((p->ainsn.insn[1] & 0x30) == 0x10) {
>   /* call absolute, indirect */
> - /* Fix return addr; eip is correct. */
> + /* Fix return addr; eip is correct
> +   But this is not boostable */
                        ^^^ Please fix comment style

>   *tos = orig_eip + (*tos - copy_eip);
>   goto no_change;
>   } else if (((p->ainsn.insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
>     ((p->ainsn.insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
> - /* eip is correct. */
> + /* eip is correct. And this is boostable */
> + p->ainsn.boostable = 1;
>   goto no_change;
>   }
>   default:
>   break;
>   }
>
> + if (p->ainsn.boostable == 0) {
> + if ( regs->eip > copy_eip &&
                   ^^^ Coding-style please :)
                   
> +     (regs->eip - copy_eip) + 5 < MAX_INSN_SIZE) {
> + /* these instructions can be executed directly if it
> + jumps back to correct address. */
                        ^^^ Comment style fix please
                       

> + set_jmp_op((void *)regs->eip,
> +   (void *)orig_eip + (regs->eip - copy_eip));
> + p->ainsn.boostable = 1;
> + } else {
> + p->ainsn.boostable = -1;
> + }
> + }
> +
>   regs->eip = orig_eip + (regs->eip - copy_eip);
>
>         no_change:
> diff -Narup a/include/asm-i386/kprobes.h b/include/asm-i386/kprobes.h
> --- a/include/asm-i386/kprobes.h 2005-12-20 19:55:51.000000000 +0900
> +++ b/include/asm-i386/kprobes.h 2005-12-20 20:03:11.000000000 +0900
> @@ -31,6 +31,7 @@ struct pt_regs;
>
>  typedef u8 kprobe_opcode_t;
>  #define BREAKPOINT_INSTRUCTION 0xcc
> +#define RELATIVEJUMP_INSTRUCTION 0xe9
>  #define MAX_INSN_SIZE 16
>  #define MAX_STACK_SIZE 64
>  #define MIN_STACK_SIZE(ADDR) (((MAX_STACK_SIZE) < \
> @@ -48,6 +49,9 @@ void kretprobe_trampoline(void);
>  struct arch_specific_insn {
>   /* copy of the original instruction */
>   kprobe_opcode_t insn[MAX_INSN_SIZE];
> + /* If this flag is not 0, this kprobe can be boost when its
> +   post_handler and break_handler is not set. */
        ^^^
        Pls fix comment style

> + int boostable;
>  };
>
>  struct prev_kprobe {
>
>
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Re: [RFC][Patch 2/2][take3]kprobe: kprobe-booster against 2.6.15-rc5-mm3 for i386

Masami Hiramatsu
Hi, Ananth

Thank you for review.

Ananth N Mavinakayanahalli wrote:

>>@@ -227,6 +275,19 @@ static int __kprobes kprobe_handler(stru
>> /* handler has already set things up, so skip ss setup */
>> return 1;
>>
>>+ if (p->ainsn.boostable == 1 &&
>>+#ifdef CONFIG_PREEMPT
>>+    preempt_count() != 1 && /* This enables booster when the
>>+     direct execution path aren't preempted. */
>     ^^^^^
> Why is the comparison against an absolute value? preempt_disable/enable()
> can be nested and on each such invocation, the count is
> incremented/decremented respectively - this number can be 0 or hold
> any positive value.

I could not find validate function/macro of preempt_count(), so I used an
absolute value.
I have an idea to remove the absolute value.
I will store the value of preempt_count() into an local variable before
the preempt_disable() calling, and will check the local variable instead
of preempt_count() itself. Thus I can write as below:

#ifdef CONFIG_PREEMPT
        !(local_preempt_count) &&
#endif

Is this OK?

> And multiline comments in
> /*
> *
> */
> format please

OK. I will fix that.


--
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: [hidden email]

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Re: [RFC][Patch 2/2][take3]kprobe: kprobe-booster against 2.6.15-rc5-mm3 for i386

Masami Hiramatsu
Hi,

Here is a cleaned patch of kprobe-booster.
- fix coding style.
- remove an absolute number.

--
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: [hidden email]

 arch/i386/kernel/kprobes.c |   92 ++++++++++++++++++++++++++++++++++++++++++++-
 include/asm-i386/kprobes.h |    6 ++
 2 files changed, 96 insertions(+), 2 deletions(-)
diff -Narup a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
--- a/arch/i386/kernel/kprobes.c 2006-01-24 22:43:17.000000000 +0900
+++ b/arch/i386/kernel/kprobes.c 2006-01-24 23:12:23.000000000 +0900
@@ -41,6 +41,49 @@ void jprobe_return_end(void);
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

+/* insert a jmp code */
+static inline void set_jmp_op(void *from, void *to)
+{
+ struct __arch_jmp_op {
+ char op;
+ long raddr;
+ } __attribute__((packed)) *jop;
+ jop = (struct __arch_jmp_op *)from;
+ jop->raddr = (long)(to) - ((long)(from) + 5);
+ jop->op = RELATIVEJUMP_INSTRUCTION;
+}
+
+/*
+ * returns non-zero if opcodes can be boosted.
+ */
+static inline int can_boost(kprobe_opcode_t opcode)
+{
+ switch (opcode & 0xf0 ) {
+ case 0x70:
+ return 0; /* can't boost conditional jump */
+ case 0x90:
+ /* can't boost call and pushf */
+ return opcode != 0x9a && opcode != 0x9c;
+ case 0xc0:
+ /* can't boost undefined opcodes and soft-interruptions */
+ return (0xc1 < opcode && opcode < 0xc6) ||
+ (0xc7 < 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 (may be) jmps */
+ return (0xe3 < opcode && opcode != 0xe8);
+ case 0xf0:
+ /* clear and set flags can be boost */
+ return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
+ default:
+ /* currently, can't boost 2 bytes opcodes */
+ return opcode != 0x0f;
+ }
+}
+
+
 /*
  * returns non-zero if opcode modifies the interrupt flag.
  */
@@ -60,6 +103,11 @@ int __kprobes arch_prepare_kprobe(struct
 {
  memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  p->opcode = *p->addr;
+ if (can_boost(p->opcode)) {
+ p->ainsn.boostable = 0;
+ } else {
+ p->ainsn.boostable = -1;
+ }
  return 0;
 }

@@ -146,6 +194,9 @@ static int __kprobes kprobe_handler(stru
  kprobe_opcode_t *addr = NULL;
  unsigned long *lp;
  struct kprobe_ctlblk *kcb;
+#ifdef CONFIG_PREEMPT
+ unsigned pre_preempt_count = preempt_count();
+#endif /* CONFIG_PREEMPT */

  /*
  * We don't want to be preempted for the entire
@@ -240,6 +291,21 @@ static int __kprobes kprobe_handler(stru
  /* handler has already set things up, so skip ss setup */
  return 1;

+ if (p->ainsn.boostable == 1 &&
+#ifdef CONFIG_PREEMPT
+    !(pre_preempt_count()) && /*
+       * This enables booster when the direct
+       * execution path aren't preempted.
+       */
+#endif /* CONFIG_PREEMPT */
+    !p->post_handler && !p->break_handler ) {
+ /* Boost up -- we can execute copied instructions directly */
+ reset_current_kprobe();
+ regs->eip = (unsigned long)&p->ainsn.insn;
+ preempt_enable_no_resched();
+ return 1;
+ }
+
 ss_probe:
  prepare_singlestep(p, regs);
  kcb->kprobe_status = KPROBE_HIT_SS;
@@ -345,6 +411,8 @@ int __kprobes trampoline_probe_handler(s
  * 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.
+ *
+ * This function also checks instruction size for preparing direct execution.
  */
 static void __kprobes resume_execution(struct kprobe *p,
  struct pt_regs *regs, struct kprobe_ctlblk *kcb)
@@ -365,6 +433,7 @@ static void __kprobes resume_execution(s
  case 0xca:
  case 0xea: /* jmp absolute -- eip is correct */
  /* eip is already adjusted, no more changes required */
+ p->ainsn.boostable = 1;
  goto no_change;
  case 0xe8: /* call relative - Fix return addr */
  *tos = orig_eip + (*tos - copy_eip);
@@ -372,18 +441,37 @@ static void __kprobes resume_execution(s
  case 0xff:
  if ((p->ainsn.insn[1] & 0x30) == 0x10) {
  /* call absolute, indirect */
- /* Fix return addr; eip is correct. */
+ /*
+ * Fix return addr; eip is correct.
+ * But this is not boostable
+ */
  *tos = orig_eip + (*tos - copy_eip);
  goto no_change;
  } else if (((p->ainsn.insn[1] & 0x31) == 0x20) || /* jmp near, absolute indirect */
    ((p->ainsn.insn[1] & 0x31) == 0x21)) { /* jmp far, absolute indirect */
- /* eip is correct. */
+ /* eip is correct. And this is boostable */
+ p->ainsn.boostable = 1;
  goto no_change;
  }
  default:
  break;
  }

+ if (p->ainsn.boostable == 0) {
+ if ((regs->eip > copy_eip) &&
+    (regs->eip - copy_eip) + 5 < MAX_INSN_SIZE) {
+ /*
+ * These instructions can be executed directly if it
+ * jumps back to correct address.
+ */
+ set_jmp_op((void *)regs->eip,
+   (void *)orig_eip + (regs->eip - copy_eip));
+ p->ainsn.boostable = 1;
+ } else {
+ p->ainsn.boostable = -1;
+ }
+ }
+
  regs->eip = orig_eip + (regs->eip - copy_eip);

 no_change:
diff -Narup a/include/asm-i386/kprobes.h b/include/asm-i386/kprobes.h
--- a/include/asm-i386/kprobes.h 2006-01-24 19:07:39.000000000 +0900
+++ b/include/asm-i386/kprobes.h 2006-01-24 22:54:35.000000000 +0900
@@ -31,6 +31,7 @@ struct pt_regs;

 typedef u8 kprobe_opcode_t;
 #define BREAKPOINT_INSTRUCTION 0xcc
+#define RELATIVEJUMP_INSTRUCTION 0xe9
 #define MAX_INSN_SIZE 16
 #define MAX_STACK_SIZE 64
 #define MIN_STACK_SIZE(ADDR) (((MAX_STACK_SIZE) < \
@@ -48,6 +49,11 @@ void kretprobe_trampoline(void);
 struct arch_specific_insn {
  /* copy of the original instruction */
  kprobe_opcode_t insn[MAX_INSN_SIZE];
+ /*
+ * If this flag is not 0, this kprobe can be boost when its
+ * post_handler and break_handler is not set.
+ */
+ int boostable;
 };

 struct prev_kprobe {