1 files changed, 281 insertions, 0 deletions
diff --git a/tools/testing/selftests/x86/iopl.c b/tools/testing/selftests/x86/iopl.c
new file mode 100644
index 000000000..7e3e09c1a
--- /dev/null
+++ b/tools/testing/selftests/x86/iopl.c
@@ -0,0 +1,281 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * iopl.c - Test case for a Linux on Xen 64-bit bug
+ * 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_outb(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_outb(unsigned short port)
+{
+	if (try_outb(port)) {
+		printf("[FAIL]\toutb to 0x%02hx worked\n", port);
+		nerrs++;
+	}
+
+	printf("[OK]\toutb to 0x%02hx failed\n", port);
+}
+
+#define RET_FAULTED	0
+#define RET_FAIL	1
+#define RET_EMUL	2
+
+static int try_cli(void)
+{
+	unsigned long flags;
+
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return RET_FAULTED;
+	} else {
+		asm volatile("cli; pushf; pop %[flags]"
+				: [flags] "=rm" (flags));
+
+		/* X86_FLAGS_IF */
+		if (!(flags & (1 << 9)))
+			return RET_FAIL;
+		else
+			return RET_EMUL;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static int try_sti(bool irqs_off)
+{
+	unsigned long flags;
+
+	sethandler(SIGSEGV, sigsegv, SA_RESETHAND);
+	if (sigsetjmp(jmpbuf, 1) != 0) {
+		return RET_FAULTED;
+	} else {
+		asm volatile("sti; pushf; pop %[flags]"
+				: [flags] "=rm" (flags));
+
+		/* X86_FLAGS_IF */
+		if (irqs_off && (flags & (1 << 9)))
+			return RET_FAIL;
+		else
+			return RET_EMUL;
+	}
+	clearhandler(SIGSEGV);
+}
+
+static void expect_gp_sti(bool irqs_off)
+{
+	int ret = try_sti(irqs_off);
+
+	switch (ret) {
+	case RET_FAULTED:
+		printf("[OK]\tSTI faulted\n");
+		break;
+	case RET_EMUL:
+		printf("[OK]\tSTI NOPped\n");
+		break;
+	default:
+		printf("[FAIL]\tSTI worked\n");
+		nerrs++;
+	}
+}
+
+/*
+ * Returns whether it managed to disable interrupts.
+ */
+static bool test_cli(void)
+{
+	int ret = try_cli();
+
+	switch (ret) {
+	case RET_FAULTED:
+		printf("[OK]\tCLI faulted\n");
+		break;
+	case RET_EMUL:
+		printf("[OK]\tCLI NOPped\n");
+		break;
+	default:
+		printf("[FAIL]\tCLI worked\n");
+		nerrs++;
+		return true;
+	}
+
+	return false;
+}
+
+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");
+
+	/* Probe for iopl support.  Note that iopl(0) works even as nonroot. */
+	switch(iopl(3)) {
+	case 0:
+		break;
+	case -ENOSYS:
+		printf("[OK]\tiopl() nor supported\n");
+		return 0;
+	default:
+		printf("[OK]\tiopl(3) failed (%d) -- try running as root\n",
+		       errno);
+		return 0;
+	}
+
+	/* Make sure that CLI/STI are blocked even with IOPL level 3 */
+	expect_gp_sti(test_cli());
+	expect_ok_outb(0x80);
+
+	/* Establish an I/O bitmap to test the restore */
+	if (ioperm(0x80, 1, 1) != 0)
+		err(1, "ioperm(0x80, 1, 1) failed\n");
+
+	/* Restore our original state prior to starting the fork test. */
+	if (iopl(0) != 0)
+		err(1, "iopl(0)");
+
+	/*
+	 * Verify that IOPL emulation is disabled and the I/O bitmap still
+	 * works.
+	 */
+	expect_ok_outb(0x80);
+	expect_gp_outb(0xed);
+	/* Drop the I/O bitmap */
+	if (ioperm(0x80, 1, 0) != 0)
+		err(1, "ioperm(0x80, 1, 0) failed\n");
+
+	pid_t child = fork();
+	if (child == -1)
+		err(1, "fork");
+
+	if (child == 0) {
+		printf("\tchild: set IOPL to 3\n");
+		if (iopl(3) != 0)
+			err(1, "iopl");
+
+		printf("[RUN]\tchild: write to 0x80\n");
+		asm volatile ("outb %%al, $0x80" : : "a" (0));
+
+		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");
+		}
+	}
+
+	printf("[RUN]\tparent: write to 0x80 (should fail)\n");
+
+	expect_gp_outb(0x80);
+	expect_gp_sti(test_cli());
+
+	/* Test the capability checks. */
+	printf("\tiopl(3)\n");
+	if (iopl(3) != 0)
+		err(1, "iopl(3)");
+
+	printf("\tDrop privileges\n");
+	if (setresuid(1, 1, 1) != 0) {
+		printf("[WARN]\tDropping privileges failed\n");
+		goto done;
+	}
+
+	printf("[RUN]\tiopl(3) unprivileged but with IOPL==3\n");
+	if (iopl(3) != 0) {
+		printf("[FAIL]\tiopl(3) should work if iopl is already 3 even if unprivileged\n");
+		nerrs++;
+	}
+
+	printf("[RUN]\tiopl(0) unprivileged\n");
+	if (iopl(0) != 0) {
+		printf("[FAIL]\tiopl(0) should work if iopl is already 3 even if unprivileged\n");
+		nerrs++;
+	}
+
+	printf("[RUN]\tiopl(3) unprivileged\n");
+	if (iopl(3) == 0) {
+		printf("[FAIL]\tiopl(3) should fail if when unprivileged if iopl==0\n");
+		nerrs++;
+	} else {
+		printf("[OK]\tFailed as expected\n");
+	}
+
+done:
+	return nerrs ? 1 : 0;
+}