// 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;
}
Codebase Browser
linux