ClabureDB: Classified Bug-Reports Database

   /*
    *  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;
}