selftests/x86: Add a basic selftest for ioperm

This doesn't fully exercise the interaction between KVM and ioperm(),
but it does test basic functionality.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

tools/testing/selftests/x86/Makefile

@@ -5,7 +5,7 @@ include ../lib.mk
 .PHONY: all all_32 all_64 warn_32bit_failure clean
 
 TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
-			check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test \
+			check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test ioperm \
 			protection_keys test_vdso
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \

tools/testing/selftests/x86/ioperm.c

+/*
+ * ioperm.c - Test case for ioperm(2)
+ * Copyright (c) 2015 Andrew Lutomirski
+ */
+
+#define _GNU_SOURCE
+#include <err.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <signal.h>
+#include <setjmp.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdbool.h>
+#include <sched.h>
+#include <sys/io.h>
+
+static int nerrs = 0;
+
+static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
+		       int flags)
+{
+	struct sigaction sa;
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_sigaction = handler;
+	sa.sa_flags = SA_SIGINFO | flags;
+	sigemptyset(&sa.sa_mask);
+	if (sigaction(sig, &sa, 0))
+		err(1, "sigaction");
+
+}
+
+static void clearhandler(int sig)
+{
+	struct sigaction sa;
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = SIG_DFL;
+	sigemptyset(&sa.sa_mask);
+	if (sigaction(sig, &sa, 0))
+		err(1, "sigaction");
+}
+
+static jmp_buf jmpbuf;
+
+static void sigsegv(int sig, siginfo_t *si, void *ctx_void)
+{
+	siglongjmp(jmpbuf, 1);
+}
+
+static bool try_outb(unsigned short port)
+{
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return false;
+	} else {
+		asm volatile ("outb %%al, %w[port]"
+			      : : [port] "Nd" (port), "a" (0));
+		return true;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static void expect_ok(unsigned short port)
+{
+	if (!try_outb(port)) {
+		printf("[FAIL]\toutb to 0x%02hx failed\n", port);
+		exit(1);
+	}
+
+	printf("[OK]\toutb to 0x%02hx worked\n", port);
+}
+
+static void expect_gp(unsigned short port)
+{
+	if (try_outb(port)) {
+		printf("[FAIL]\toutb to 0x%02hx worked\n", port);
+		exit(1);
+	}
+
+	printf("[OK]\toutb to 0x%02hx failed\n", port);
+}
+
+int main(void)
+{
+	cpu_set_t cpuset;
+	CPU_ZERO(&cpuset);
+	CPU_SET(0, &cpuset);
+	if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
+		err(1, "sched_setaffinity to CPU 0");
+
+	expect_gp(0x80);
+	expect_gp(0xed);
+
+	/*
+	 * Probe for ioperm support.  Note that clearing ioperm bits
+	 * works even as nonroot.
+	 */
+	printf("[RUN]\tenable 0x80\n");
+	if (ioperm(0x80, 1, 1) != 0) {
+		printf("[OK]\tioperm(0x80, 1, 1) failed (%d) -- try running as root\n",
+		       errno);
+		return 0;
+	}
+	expect_ok(0x80);
+	expect_gp(0xed);
+
+	printf("[RUN]\tdisable 0x80\n");
+	if (ioperm(0x80, 1, 0) != 0) {
+		printf("[FAIL]\tioperm(0x80, 1, 0) failed (%d)", errno);
+		return 1;
+	}
+	expect_gp(0x80);
+	expect_gp(0xed);
+
+	/* Make sure that fork() preserves ioperm. */
+	if (ioperm(0x80, 1, 1) != 0) {
+		printf("[FAIL]\tioperm(0x80, 1, 0) failed (%d)", errno);
+		return 1;
+	}
+
+	pid_t child = fork();
+	if (child == -1)
+		err(1, "fork");
+
+	if (child == 0) {
+		printf("[RUN]\tchild: check that we inherited permissions\n");
+		expect_ok(0x80);
+		expect_gp(0xed);
+		return 0;
+	} else {
+		int status;
+		if (waitpid(child, &status, 0) != child ||
+		    !WIFEXITED(status)) {
+			printf("[FAIL]\tChild died\n");
+			nerrs++;
+		} else if (WEXITSTATUS(status) != 0) {
+			printf("[FAIL]\tChild failed\n");
+			nerrs++;
+		} else {
+			printf("[OK]\tChild succeeded\n");
+		}
+	}
+
+	/* Test the capability checks. */
+
+	printf("\tDrop privileges\n");
+	if (setresuid(1, 1, 1) != 0) {
+		printf("[WARN]\tDropping privileges failed\n");
+		return 0;
+	}
+
+	printf("[RUN]\tdisable 0x80\n");
+	if (ioperm(0x80, 1, 0) != 0) {
+		printf("[FAIL]\tioperm(0x80, 1, 0) failed (%d)", errno);
+		return 1;
+	}
+	printf("[OK]\tit worked\n");
+
+	printf("[RUN]\tenable 0x80 again\n");
+	if (ioperm(0x80, 1, 1) == 0) {
+		printf("[FAIL]\tit succeeded but should have failed.\n");
+		return 1;
+	}
+	printf("[OK]\tit failed\n");
+	return 0;
+}