X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=arch%2Fx86%2Fkernel%2Fkprobes.c;h=b8c6743a13daddad0446d686d3f36436b3ac7531;hb=d23b200a75f78e62744c3c25d078855eec8a689b;hp=80bcb7635465c2b6936951bf3176f72c77456593;hpb=31f80e45ea26008939790b4363a4fdcff240e0d6;p=linux-2.6

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 80bcb76354..b8c6743a13 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -44,6 +44,7 @@
 #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>
@@ -409,13 +410,13 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 static void __kprobes clear_btf(void)
 {
 	if (test_thread_flag(TIF_DEBUGCTLMSR))
-		wrmsr(MSR_IA32_DEBUGCTLMSR, 0, 0);
+		update_debugctlmsr(0);
 }
 
 static void __kprobes restore_btf(void)
 {
 	if (test_thread_flag(TIF_DEBUGCTLMSR))
-		wrmsr(MSR_IA32_DEBUGCTLMSR, current->thread.debugctlmsr, 0);
+		update_debugctlmsr(current->thread.debugctlmsr);
 }
 
 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -441,6 +442,23 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 	/* 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
@@ -449,13 +467,9 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
 				    struct kprobe_ctlblk *kcb)
 {
-	if (kcb->kprobe_status == KPROBE_HIT_SS &&
-	    *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
-		regs->flags &= ~X86_EFLAGS_TF;
-		regs->flags |= kcb->kprobe_saved_flags;
-		return 0;
+	switch (kcb->kprobe_status) {
+	case KPROBE_HIT_SSDONE:
 #ifdef CONFIG_X86_64
-	} else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
 		/* TODO: Provide re-entrancy from post_kprobes_handler() and
 		 * avoid exception stack corruption while single-stepping on
 		 * the instruction of the new probe.
@@ -463,14 +477,35 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
 		arch_disarm_kprobe(p);
 		regs->ip = (unsigned long)p->addr;
 		reset_current_kprobe();
-		return 1;
+		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;
 	}
-	save_previous_kprobe(kcb);
-	set_current_kprobe(p, regs, kcb);
-	kprobes_inc_nmissed_count(p);
-	prepare_singlestep(p, regs);
-	kcb->kprobe_status = KPROBE_REENTER;
+
 	return 1;
 }
 
@@ -480,95 +515,74 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
  */
 static int __kprobes kprobe_handler(struct pt_regs *regs)
 {
-	struct kprobe *p;
-	int ret = 0;
 	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
+	 * 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);
 
-	/* Check we're not actually recursing */
-	if (kprobe_running()) {
-		p = get_kprobe(addr);
-		if (p) {
-			ret = reenter_kprobe(p, regs, kcb);
-			if (kcb->kprobe_status == KPROBE_REENTER)
+	if (p) {
+		if (kprobe_running()) {
+			if (reenter_kprobe(p, regs, kcb))
 				return 1;
 		} else {
-			if (*addr != BREAKPOINT_INSTRUCTION) {
-			/* The breakpoint instruction was removed by
-			 * another cpu right after we hit, no further
-			 * handling of this interrupt is appropriate
-			 */
-				regs->ip = (unsigned long)addr;
-				ret = 1;
-				goto no_kprobe;
-			}
-			p = __get_cpu_var(current_kprobe);
-			if (p->break_handler && p->break_handler(p, regs))
-				goto ss_probe;
-		}
-		goto no_kprobe;
-	}
+			set_current_kprobe(p, regs, kcb);
+			kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 
-	p = get_kprobe(addr);
-	if (!p) {
-		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.
+			 * 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.
 			 */
-			regs->ip = (unsigned long)addr;
-			ret = 1;
+			if (!p->pre_handler || !p->pre_handler(p, regs))
+				setup_singlestep(p, regs, kcb);
+			return 1;
 		}
-		/* Not one of ours: let kernel handle it */
-		goto no_kprobe;
-	}
-
-	set_current_kprobe(p, regs, kcb);
-	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
-
-	if (p->pre_handler && p->pre_handler(p, regs))
-		/* handler has already set things up, so skip ss setup */
-		return 1;
-
-ss_probe:
-#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 1;
-	}
-#endif
-	prepare_singlestep(p, regs);
-	kcb->kprobe_status = KPROBE_HIT_SS;
-	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 */
 
-no_kprobe:
 	preempt_enable_no_resched();
-	return ret;
+	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)
- {
+static void __used __kprobes kretprobe_trampoline_holder(void)
+{
 	asm volatile (
 			".global kretprobe_trampoline\n"
 			"kretprobe_trampoline: \n"
@@ -654,12 +668,12 @@ no_kprobe:
 			"	popf\n"
 #endif
 			"	ret\n");
- }
+}
 
 /*
  * Called from kretprobe_trampoline
  */
-void * __kprobes trampoline_handler(struct pt_regs *regs)
+static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
 {
 	struct kretprobe_instance *ri = NULL;
 	struct hlist_head *head, empty_rp;
@@ -844,15 +858,15 @@ static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 	if (!cur)
 		return 0;
 
+	resume_execution(cur, regs, kcb);
+	regs->flags |= kcb->kprobe_saved_flags;
+	trace_hardirqs_fixup_flags(regs->flags);
+
 	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);
@@ -939,7 +953,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 				       unsigned long val, void *data)
 {
-	struct die_args *args = (struct die_args *)data;
+	struct die_args *args = data;
 	int ret = NOTIFY_DONE;
 
 	if (args->regs && user_mode_vm(args->regs))
@@ -955,12 +969,14 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 			ret = NOTIFY_STOP;
 		break;
 	case DIE_GPF:
-		/* kprobe_running() needs smp_processor_id() */
-		preempt_disable();
-		if (kprobe_running() &&
+		/*
+		 * 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;
-		preempt_enable();
 		break;
 	default:
 		break;