diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index d105f29..7d0b681 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -186,6 +186,15 @@
 config HAVE_MMIOTRACE_SUPPORT
 	def_bool y
 
+config X86_DECODER_SELFTEST
+     bool "x86 instruction decoder selftest"
+     depends on DEBUG_KERNEL
+	---help---
+	 Perform x86 instruction decoder selftests at build time.
+	 This option is useful for checking the sanity of x86 instruction
+	 decoder code.
+	 If unsure, say "N".
+
 #
 # IO delay types:
 #
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 1b68659..5fe16bf 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -154,6 +154,9 @@
 KBUILD_IMAGE := $(boot)/bzImage
 
 bzImage: vmlinux
+ifeq ($(CONFIG_X86_DECODER_SELFTEST),y)
+	$(Q)$(MAKE) $(build)=arch/x86/tools posttest
+endif
 	$(Q)$(MAKE) $(build)=$(boot) $(KBUILD_IMAGE)
 	$(Q)mkdir -p $(objtree)/arch/$(UTS_MACHINE)/boot
 	$(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/$@
diff --git a/arch/x86/tools/Makefile b/arch/x86/tools/Makefile
new file mode 100644
index 0000000..3dd626b
--- /dev/null
+++ b/arch/x86/tools/Makefile
@@ -0,0 +1,15 @@
+PHONY += posttest
+quiet_cmd_posttest = TEST    $@
+      cmd_posttest = $(OBJDUMP) -d $(objtree)/vmlinux | awk -f $(srctree)/arch/x86/tools/distill.awk | $(obj)/test_get_len
+
+posttest: $(obj)/test_get_len vmlinux
+	$(call cmd,posttest)
+
+hostprogs-y	:= test_get_len
+
+# -I needed for generated C source and C source which in the kernel tree.
+HOSTCFLAGS_test_get_len.o := -Wall -I$(objtree)/arch/x86/lib/ -I$(srctree)/arch/x86/include/ -I$(srctree)/arch/x86/lib/
+
+# Dependancies are also needed.
+$(obj)/test_get_len.o: $(srctree)/arch/x86/lib/insn.c $(srctree)/arch/x86/lib/inat.c $(srctree)/arch/x86/include/asm/inat_types.h $(srctree)/arch/x86/include/asm/inat.h $(srctree)/arch/x86/include/asm/insn.h $(objtree)/arch/x86/lib/inat-tables.c
+
diff --git a/arch/x86/tools/distill.awk b/arch/x86/tools/distill.awk
new file mode 100644
index 0000000..d433619
--- /dev/null
+++ b/arch/x86/tools/distill.awk
@@ -0,0 +1,42 @@
+#!/bin/awk -f
+# Usage: objdump -d a.out | awk -f distill.awk | ./test_get_len
+# Distills the disassembly as follows:
+# - Removes all lines except the disassembled instructions.
+# - For instructions that exceed 1 line (7 bytes), crams all the hex bytes
+# into a single line.
+# - Remove bad(or prefix only) instructions
+
+BEGIN {
+	prev_addr = ""
+	prev_hex = ""
+	prev_mnemonic = ""
+	bad_expr = "(\\(bad\\)|^rex|^.byte|^rep(z|nz)$|^lock$|^es$|^cs$|^ss$|^ds$|^fs$|^gs$|^data(16|32)$|^addr(16|32|64))"
+	fwait_expr = "^9b "
+	fwait_str="9b\tfwait"
+}
+
+/^ *[0-9a-f]+:/ {
+	if (split($0, field, "\t") < 3) {
+		# This is a continuation of the same insn.
+		prev_hex = prev_hex field[2]
+	} else {
+		# Skip bad instructions
+		if (match(prev_mnemonic, bad_expr))
+			prev_addr = ""
+		# Split fwait from other f* instructions
+		if (match(prev_hex, fwait_expr) && prev_mnemonic != "fwait") {
+			printf "%s\t%s\n", prev_addr, fwait_str
+			sub(fwait_expr, "", prev_hex)
+		}
+		if (prev_addr != "")
+			printf "%s\t%s\t%s\n", prev_addr, prev_hex, prev_mnemonic
+		prev_addr = field[1]
+		prev_hex = field[2]
+		prev_mnemonic = field[3]
+	}
+}
+
+END {
+	if (prev_addr != "")
+		printf "%s\t%s\t%s\n", prev_addr, prev_hex, prev_mnemonic
+}
diff --git a/arch/x86/tools/test_get_len.c b/arch/x86/tools/test_get_len.c
new file mode 100644
index 0000000..1e81adb
--- /dev/null
+++ b/arch/x86/tools/test_get_len.c
@@ -0,0 +1,113 @@
+/*
+ * 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, 2009
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#ifdef __x86_64__
+#define CONFIG_X86_64
+#else
+#define CONFIG_X86_32
+#endif
+#define unlikely(cond) (cond)
+
+#include <asm/insn.h>
+#include <inat.c>
+#include <insn.c>
+
+/*
+ * Test of instruction analysis in general and insn_get_length() in
+ * particular.  See if insn_get_length() and the disassembler agree
+ * on the length of each instruction in an elf disassembly.
+ *
+ * Usage: objdump -d a.out | awk -f distill.awk | ./test_get_len
+ */
+
+const char *prog;
+
+static void usage(void)
+{
+	fprintf(stderr, "Usage: objdump -d a.out | awk -f distill.awk |"
+		" ./test_get_len\n");
+	exit(1);
+}
+
+static void malformed_line(const char *line, int line_nr)
+{
+	fprintf(stderr, "%s: malformed line %d:\n%s", prog, line_nr, line);
+	exit(3);
+}
+
+#define BUFSIZE 256
+
+int main(int argc, char **argv)
+{
+	char line[BUFSIZE];
+	unsigned char insn_buf[16];
+	struct insn insn;
+	int insns = 0;
+
+	prog = argv[0];
+	if (argc > 1)
+		usage();
+
+	while (fgets(line, BUFSIZE, stdin)) {
+		char copy[BUFSIZE], *s, *tab1, *tab2;
+		int nb = 0;
+		unsigned int b;
+
+		insns++;
+		memset(insn_buf, 0, 16);
+		strcpy(copy, line);
+		tab1 = strchr(copy, '\t');
+		if (!tab1)
+			malformed_line(line, insns);
+		s = tab1 + 1;
+		s += strspn(s, " ");
+		tab2 = strchr(s, '\t');
+		if (!tab2)
+			malformed_line(line, insns);
+		*tab2 = '\0';	/* Characters beyond tab2 aren't examined */
+		while (s < tab2) {
+			if (sscanf(s, "%x", &b) == 1) {
+				insn_buf[nb++] = (unsigned char) b;
+				s += 3;
+			} else
+				break;
+		}
+		/* Decode an instruction */
+#ifdef __x86_64__
+		insn_init(&insn, insn_buf, 1);
+#else
+		insn_init(&insn, insn_buf, 0);
+#endif
+		insn_get_length(&insn);
+		if (insn.length != nb) {
+			fprintf(stderr, "Error: %s", line);
+			fprintf(stderr, "Error: objdump says %d bytes, but "
+				"insn_get_length() says %d (attr:%x)\n", nb,
+				insn.length, insn.attr);
+			exit(2);
+		}
+	}
+	fprintf(stderr, "Succeed: decoded and checked %d instructions\n",
+		insns);
+	return 0;
+}