1 files changed, 194 insertions, 59 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 7a59050242a7..f19768789e8a 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -35,12 +35,56 @@
 #include <asm/cacheflush.h>
 #include <asm/kdebug.h>
 #include <asm/desc.h>
+#include <asm/uaccess.h>
 
 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.
  */
@@ -65,6 +109,11 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 
         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;
 }
 
@@ -155,9 +204,13 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 {
         struct kprobe *p;
         int ret = 0;
-        kprobe_opcode_t *addr = NULL;
-        unsigned long *lp;
+        kprobe_opcode_t *addr;
         struct kprobe_ctlblk *kcb;
+#ifdef CONFIG_PREEMPT
+        unsigned pre_preempt_count = preempt_count();
+#endif /* CONFIG_PREEMPT */
+
+        addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
 
         /*
          * We don't want to be preempted for the entire
@@ -166,17 +219,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
         preempt_disable();
         kcb = get_kprobe_ctlblk();
 
-        /* Check if the application is using LDT entry for its code segment and
-         * calculate the address by reading the base address from the LDT entry.
-         */
-        if ((regs->xcs & 4) && (current->mm)) {
-                lp = (unsigned long *) ((unsigned long)((regs->xcs >> 3) * 8)
-                                        + (char *) current->mm->context.ldt);
-                addr = (kprobe_opcode_t *) (get_desc_base(lp) + regs->eip -
-                                                sizeof(kprobe_opcode_t));
-        } else {
-                addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
-        }
         /* Check we're not actually recursing */
         if (kprobe_running()) {
                 p = get_kprobe(addr);
@@ -252,6 +294,21 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
                 /* 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;
@@ -267,17 +324,44 @@ no_kprobe:
  * here. When a retprobed function returns, this probe is hit and
  * trampoline_probe_handler() runs, calling the kretprobe's handler.
  */
- void kretprobe_trampoline_holder(void)
+ void __kprobes kretprobe_trampoline_holder(void)
  {
-        asm volatile (  ".global kretprobe_trampoline\n"
+        asm volatile ( ".global kretprobe_trampoline\n"
                         "kretprobe_trampoline: \n"
-                        "nop\n");
- }
+                        "       pushf\n"
+                        /* skip cs, eip, orig_eax, es, ds */
+                        "       subl $20, %esp\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 eflags to cs */
+                        "       movl 48(%esp), %edx\n"
+                        "       movl %edx, 44(%esp)\n"
+                        /* save true return address on eflags */
+                        "       movl %eax, 48(%esp)\n"
+                        "       popl %ebx\n"
+                        "       popl %ecx\n"
+                        "       popl %edx\n"
+                        "       popl %esi\n"
+                        "       popl %edi\n"
+                        "       popl %ebp\n"
+                        "       popl %eax\n"
+                        /* skip eip, orig_eax, es, ds */
+                        "       addl $16, %esp\n"
+                        "       popf\n"
+                        "       ret\n");
+}
 
 /*
- * Called when we hit the probe point at kretprobe_trampoline
+ * Called from kretprobe_trampoline
  */
-int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
 {
         struct kretprobe_instance *ri = NULL;
         struct hlist_head *head;
@@ -306,8 +390,11 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
                         /* another task is sharing our hash bucket */
                         continue;
 
-                if (ri->rp && ri->rp->handler)
+                if (ri->rp && ri->rp->handler){
+                        __get_cpu_var(current_kprobe) = &ri->rp->kp;
                         ri->rp->handler(ri, regs);
+                        __get_cpu_var(current_kprobe) = NULL;
+                }
 
                 orig_ret_address = (unsigned long)ri->ret_addr;
                 recycle_rp_inst(ri);
@@ -322,18 +409,10 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
         }
 
         BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
-        regs->eip = orig_ret_address;
 
-        reset_current_kprobe();
         spin_unlock_irqrestore(&kretprobe_lock, flags);
-        preempt_enable_no_resched();
 
-        /*
-         * By returning a non-zero value, we are telling
-         * kprobe_handler() that we don't want the post_handler
-         * to run (and have re-enabled preemption)
-         */
-        return 1;
+        return (void*)orig_ret_address;
 }
 
 /*
@@ -357,15 +436,17 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
  * 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)
 {
         unsigned long *tos = (unsigned long *)&regs->esp;
-        unsigned long next_eip = 0;
         unsigned long copy_eip = (unsigned long)p->ainsn.insn;
         unsigned long orig_eip = (unsigned long)p->addr;
 
+        regs->eflags &= ~TF_MASK;
         switch (p->ainsn.insn[0]) {
         case 0x9c:              /* pushfl */
                 *tos &= ~(TF_MASK | IF_MASK);
@@ -375,37 +456,51 @@ static void __kprobes resume_execution(struct kprobe *p,
         case 0xcb:
         case 0xc2:
         case 0xca:
-                regs->eflags &= ~TF_MASK;
-                /* eip is already adjusted, no more changes required*/
-                return;
+        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);
                 break;
         case 0xff:
                 if ((p->ainsn.insn[1] & 0x30) == 0x10) {
                         /* call absolute, indirect */
-                        /* Fix return addr; eip is correct. */
-                        next_eip = regs->eip;
+                        /*
+                         * 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. */
-                        next_eip = regs->eip;
+                        /* eip is correct. And this is boostable */
+                        p->ainsn.boostable = 1;
+                        goto no_change;
                 }
-                break;
-        case 0xea:              /* jmp absolute -- eip is correct */
-                next_eip = regs->eip;
-                break;
         default:
                 break;
         }
 
-        regs->eflags &= ~TF_MASK;
-        if (next_eip) {
-                regs->eip = next_eip;
-        } else {
-                regs->eip = orig_eip + (regs->eip - copy_eip);
+        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:
+        return;
 }
 
 /*
@@ -453,15 +548,57 @@ static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
         struct kprobe *cur = kprobe_running();
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 
-        if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
-                return 1;
-
-        if (kcb->kprobe_status & KPROBE_HIT_SS) {
-                resume_execution(cur, regs, kcb);
+        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 eip points back to the probe address
+                 * and allow the page fault handler to continue as a
+                 * normal page fault.
+                 */
+                regs->eip = (unsigned long)cur->addr;
                 regs->eflags |= kcb->kprobe_old_eflags;
-
-                reset_current_kprobe();
+                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 accouting
+                 * 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_exception() could not handle it,
+                 * Let do_page_fault() fix it.
+                 */
+                break;
+        default:
+                break;
         }
         return 0;
 }
@@ -475,6 +612,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
         struct die_args *args = (struct die_args *)data;
         int ret = NOTIFY_DONE;
 
+        if (args->regs && user_mode(args->regs))
+                return ret;
+
         switch (val) {
         case DIE_INT3:
                 if (kprobe_handler(args->regs))
@@ -564,12 +704,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
         return 0;
 }
 
-static struct kprobe trampoline_p = {
-        .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
-        .pre_handler = trampoline_probe_handler
-};
-
 int __init arch_init_kprobes(void)
 {
-        return register_kprobe(&trampoline_p);
+        return 0;
 }