x86, selftests: Add sigreturn selftest

This is my sigreturn test, added mostly unchanged from its old
home. It exercises the sigreturn(2) syscall, specifically
focusing on its interactions with various IRET corner cases.

It tests for correct behavior in several areas that were
historically dangerously buggy. For example, it exercises espfix
on kernels of both bitnesses under various conditions, and it
contains testcases for several now-fixed bugs in IRET error
handling.

If you run it on older kernels without the fixes, your system will
crash. It probably won't eat your data in the process.

There is no released kernel on which the sigreturn_64 test will
pass, but it passes on tip:x86/asm.

I plan to switch to lib.mk for Linux 4.2.

I'm not using the ksft_ helpers at all yet.  I can do that later.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/89d10b76b92c7202d8123654dc8d36701c017b3d.1428386971.git.luto@kernel.org
[ Fixed empty format string GCC build warning in trivial_32bit_program.c ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

tools/testing/selftests/Makefile

@@ -17,6 +17,7 @@ TARGETS += sysctl
 TARGETS += timers
 TARGETS += user
 TARGETS += vm
+TARGETS += x86
 #Please keep the TARGETS list alphabetically sorted
 
 TARGETS_HOTPLUG = cpu-hotplug

tools/testing/selftests/x86/.gitignore

@@ -0,0 +1,2 @@
+*_32
+*_64

tools/testing/selftests/x86/Makefile

@@ -0,0 +1,48 @@
+.PHONY: all all_32 all_64 check_build32 clean run_tests
+
+TARGETS_C_BOTHBITS := sigreturn
+
+BINARIES_32 := $(TARGETS_C_BOTHBITS:%=%_32)
+BINARIES_64 := $(TARGETS_C_BOTHBITS:%=%_64)
+
+CFLAGS := -O2 -g -std=gnu99 -pthread -Wall
+
+UNAME_P := $(shell uname -p)
+
+# Always build 32-bit tests
+all: all_32
+
+# If we're on a 64-bit host, build 64-bit tests as well
+ifeq ($(shell uname -p),x86_64)
+all: all_64
+endif
+
+all_32: check_build32 $(BINARIES_32)
+
+all_64: $(BINARIES_64)
+
+clean:
+	$(RM) $(BINARIES_32) $(BINARIES_64)
+
+run_tests:
+	./run_x86_tests.sh
+
+$(TARGETS_C_BOTHBITS:%=%_32): %_32: %.c
+	$(CC) -m32 -o $@ $(CFLAGS) $(EXTRA_CFLAGS) $^ -lrt -ldl
+
+$(TARGETS_C_BOTHBITS:%=%_64): %_64: %.c
+	$(CC) -m64 -o $@ $(CFLAGS) $(EXTRA_CFLAGS) $^ -lrt -ldl
+
+check_build32:
+	@if ! $(CC) -m32 -o /dev/null trivial_32bit_program.c; then	\
+	  echo "Warning: you seem to have a broken 32-bit build" 2>&1; 	\
+	  echo "environment.  If you are using a Debian-like";		\
+	  echo " distribution, try:"; 					\
+	  echo "";							\
+	  echo "  apt-get install gcc-multilib libc6-i386 libc6-dev-i386"; \
+	  echo "";							\
+	  echo "If you are using a Fedora-like distribution, try:";	\
+	  echo "";							\
+	  echo "  yum install glibc-devel.*i686";			\
+	  exit 1;							\
+	fi

tools/testing/selftests/x86/run_x86_tests.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+# This is deliberately minimal.  IMO kselftests should provide a standard
+# script here.
+./sigreturn_32 || exit 1
+
+if [[ "$uname -p" -eq "x86_64" ]]; then
+    ./sigreturn_64 || exit 1
+fi
+
+exit 0

tools/testing/selftests/x86/trivial_32bit_program.c

@@ -0,0 +1,14 @@
+/*
+ * Trivial program to check that we have a valid 32-bit build environment.
+ * Copyright (c) 2015 Andy Lutomirski
+ * GPL v2
+ */
+
+#include <stdio.h>
+
+int main()
+{
+	printf("\n");
+
+	return 0;
+}