From 71f6ba47b2141e263b2900a71f419183f6eca908 Mon Sep 17 00:00:00 2001
From: Zachary Amsden <zach@vmware.com>
Date: Fri, 6 Jan 2006 00:11:50 -0800
Subject: [PATCH] --- yaml --- r: 16369 b: refs/heads/master c:
 ff6e8c0d5e47f0ceeebde86ec2f5919dbd5beb67 h: refs/heads/master i:   16367:
 2d5e057e812be99caf664003b3650eafb580e8c4 v: v3

---
 [refs]                           |  2 +-
 trunk/arch/i386/kernel/process.c |  4 +---
 trunk/include/asm-i386/system.h  | 13 +++++++++++++
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/[refs] b/[refs]
index df25ef623aaa..7988ee53445c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: eb05c3249a8e8a675e79d221f4a0874dc10ec903
+refs/heads/master: ff6e8c0d5e47f0ceeebde86ec2f5919dbd5beb67
diff --git a/trunk/arch/i386/kernel/process.c b/trunk/arch/i386/kernel/process.c
index 2333aead0563..6081a10d3416 100644
--- a/trunk/arch/i386/kernel/process.c
+++ b/trunk/arch/i386/kernel/process.c
@@ -308,9 +308,7 @@ void show_regs(struct pt_regs * regs)
 	cr0 = read_cr0();
 	cr2 = read_cr2();
 	cr3 = read_cr3();
-	if (current_cpu_data.x86 > 4) {
-		cr4 = read_cr4();
-	}
+	cr4 = read_cr4_safe();
 	printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", cr0, cr2, cr3, cr4);
 	show_trace(NULL, &regs->esp);
 }
diff --git a/trunk/include/asm-i386/system.h b/trunk/include/asm-i386/system.h
index 772f85da1206..88b4d5c6f37a 100644
--- a/trunk/include/asm-i386/system.h
+++ b/trunk/include/asm-i386/system.h
@@ -140,6 +140,19 @@ static inline unsigned long _get_base(char * addr)
 		:"=r" (__dummy)); \
 	__dummy; \
 })
+
+#define read_cr4_safe() ({			      \
+	unsigned int __dummy;			      \
+	/* This could fault if %cr4 does not exist */ \
+	__asm__("1: movl %%cr4, %0		\n"   \
+		"2:				\n"   \
+		".section __ex_table,\"a\"	\n"   \
+		".long 1b,2b			\n"   \
+		".previous			\n"   \
+		: "=r" (__dummy): "0" (0));	      \
+	__dummy;				      \
+})
+
 #define write_cr4(x) \
 	__asm__ __volatile__("movl %0,%%cr4": :"r" (x));
 #define stts() write_cr0(8 | read_cr0())