Merge branch 'linux-2.6'

1 files changed, 1066 insertions, 0 deletions

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
new file mode 100644
index 000000000000..a99e764fd66a
--- /dev/null
+++ b/arch/x86/kernel/kprobes.c
@@ -0,0 +1,1066 @@
+/*
+ *  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))
+                wrmsrl(MSR_IA32_DEBUGCTLMSR, 0);
+}
+
+static void __kprobes restore_btf(void)
+{
+        if (test_thread_flag(TIF_DEBUGCTLMSR))
+                wrmsrl(MSR_IA32_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;
+}
+
+/* Called with kretprobe_lock held */
+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 &= ~TF_MASK;
+                        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.
+ */
+void __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
+ */
+void * __kprobes 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);
+        spin_lock_irqsave(&kretprobe_lock, flags);
+        head = kretprobe_inst_table_head(current);
+        /* 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);
+
+        spin_unlock_irqrestore(&kretprobe_lock, 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;
+
+        if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
+                kcb->kprobe_status = KPROBE_HIT_SSDONE;
+                cur->post_handler(cur, regs, 0);
+        }
+
+        resume_execution(cur, regs, kcb);
+        regs->flags |= kcb->kprobe_saved_flags;
+        trace_hardirqs_fixup_flags(regs->flags);
+
+        /* 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;
+}