diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
index d82f39bb7905..8d33bc5462d1 100644
--- a/arch/x86/include/asm/syscall.h
+++ b/arch/x86/include/asm/syscall.h
@@ -1,7 +1,7 @@
 /*
  * Access to user system call parameters and results
  *
- * Copyright (C) 2008 Red Hat, Inc.  All rights reserved.
+ * Copyright (C) 2008-2009 Red Hat, Inc.  All rights reserved.
  *
  * This copyrighted material is made available to anyone wishing to use,
  * modify, copy, or redistribute it subject to the terms and conditions
@@ -16,13 +16,13 @@
 #include <linux/sched.h>
 #include <linux/err.h>
 
-static inline long syscall_get_nr(struct task_struct *task,
-				  struct pt_regs *regs)
+/*
+ * Only the low 32 bits of orig_ax are meaningful, so we return int.
+ * This importantly ignores the high bits on 64-bit, so comparisons
+ * sign-extend the low 32 bits.
+ */
+static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
 {
-	/*
-	 * We always sign-extend a -1 value being set here,
-	 * so this is always either -1L or a syscall number.
-	 */
 	return regs->orig_ax;
 }
 
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 8d7d5c9c1be3..7b058a2dc66a 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -325,16 +325,6 @@ static int putreg(struct task_struct *child,
 		return set_flags(child, value);
 
 #ifdef CONFIG_X86_64
-	/*
-	 * Orig_ax is really just a flag with small positive and
-	 * negative values, so make sure to always sign-extend it
-	 * from 32 bits so that it works correctly regardless of
-	 * whether we come from a 32-bit environment or not.
-	 */
-	case offsetof(struct user_regs_struct, orig_ax):
-		value = (long) (s32) value;
-		break;
-
 	case offsetof(struct user_regs_struct,fs_base):
 		if (value >= TASK_SIZE_OF(child))
 			return -EIO;
@@ -1126,10 +1116,15 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 value)
 
 	case offsetof(struct user32, regs.orig_eax):
 		/*
-		 * Sign-extend the value so that orig_eax = -1
-		 * causes (long)orig_ax < 0 tests to fire correctly.
+		 * A 32-bit debugger setting orig_eax means to restore
+		 * the state of the task restarting a 32-bit syscall.
+		 * Make sure we interpret the -ERESTART* codes correctly
+		 * in case the task is not actually still sitting at the
+		 * exit from a 32-bit syscall with TS_COMPAT still set.
 		 */
-		regs->orig_ax = (long) (s32) value;
+		regs->orig_ax = value;
+		if (syscall_get_nr(child, regs) >= 0)
+			task_thread_info(child)->status |= TS_COMPAT;
 		break;
 
 	case offsetof(struct user32, regs.eflags):
diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index ea8087b55ffc..5c122ae6bfa6 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -1,7 +1,7 @@
 /*
  * Access to user system call parameters and results
  *
- * Copyright (C) 2008 Red Hat, Inc.  All rights reserved.
+ * Copyright (C) 2008-2009 Red Hat, Inc.  All rights reserved.
  *
  * This copyrighted material is made available to anyone wishing to use,
  * modify, copy, or redistribute it subject to the terms and conditions
@@ -32,9 +32,13 @@ struct pt_regs;
  * If @task is not executing a system call, i.e. it's blocked
  * inside the kernel for a fault or signal, returns -1.
  *
+ * Note this returns int even on 64-bit machines.  Only 32 bits of
+ * system call number can be meaningful.  If the actual arch value
+ * is 64 bits, this truncates to 32 bits so 0xffffffff means -1.
+ *
  * It's only valid to call this when @task is known to be blocked.
  */
-long syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
+int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
 
 /**
  * syscall_rollback - roll back registers after an aborted system call