LXR linux/tools/testing/selftests/x86/iopl.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * iopl.c - Test case for a Linux on Xen 64-bit bug
   4 * Copyright (c) 2015 Andrew Lutomirski
   5 */
   6
   7#define _GNU_SOURCE
   8#include <err.h>
   9#include <stdio.h>
  10#include <stdint.h>
  11#include <signal.h>
  12#include <setjmp.h>
  13#include <stdlib.h>
  14#include <string.h>
  15#include <errno.h>
  16#include <unistd.h>
  17#include <sys/types.h>
  18#include <sys/wait.h>
  19#include <stdbool.h>
  20#include <sched.h>
  21#include <sys/io.h>
  22
  23static int nerrs = 0;
  24
  25static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
  26                       int flags)
  27{
  28        struct sigaction sa;
  29        memset(&sa, 0, sizeof(sa));
  30        sa.sa_sigaction = handler;
  31        sa.sa_flags = SA_SIGINFO | flags;
  32        sigemptyset(&sa.sa_mask);
  33        if (sigaction(sig, &sa, 0))
  34                err(1, "sigaction");
  35
  36}
  37
  38static jmp_buf jmpbuf;
  39
  40static void sigsegv(int sig, siginfo_t *si, void *ctx_void)
  41{
  42        siglongjmp(jmpbuf, 1);
  43}
  44
  45int main(void)
  46{
  47        cpu_set_t cpuset;
  48        CPU_ZERO(&cpuset);
  49        CPU_SET(0, &cpuset);
  50        if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
  51                err(1, "sched_setaffinity to CPU 0");
  52
  53        /* Probe for iopl support.  Note that iopl(0) works even as nonroot. */
  54        if (iopl(3) != 0) {
  55                printf("[OK]\tiopl(3) failed (%d) -- try running as root\n",
  56                       errno);
  57                return 0;
  58        }
  59
  60        /* Restore our original state prior to starting the test. */
  61        if (iopl(0) != 0)
  62                err(1, "iopl(0)");
  63
  64        pid_t child = fork();
  65        if (child == -1)
  66                err(1, "fork");
  67
  68        if (child == 0) {
  69                printf("\tchild: set IOPL to 3\n");
  70                if (iopl(3) != 0)
  71                        err(1, "iopl");
  72
  73                printf("[RUN]\tchild: write to 0x80\n");
  74                asm volatile ("outb %%al, $0x80" : : "a" (0));
  75
  76                return 0;
  77        } else {
  78                int status;
  79                if (waitpid(child, &status, 0) != child ||
  80                    !WIFEXITED(status)) {
  81                        printf("[FAIL]\tChild died\n");
  82                        nerrs++;
  83                } else if (WEXITSTATUS(status) != 0) {
  84                        printf("[FAIL]\tChild failed\n");
  85                        nerrs++;
  86                } else {
  87                        printf("[OK]\tChild succeeded\n");
  88                }
  89        }
  90
  91        printf("[RUN]\tparent: write to 0x80 (should fail)\n");
  92
  93        sethandler(SIGSEGV, sigsegv, 0);
  94        if (sigsetjmp(jmpbuf, 1) != 0) {
  95                printf("[OK]\twrite was denied\n");
  96        } else {
  97                asm volatile ("outb %%al, $0x80" : : "a" (0));
  98                printf("[FAIL]\twrite was allowed\n");
  99                nerrs++;
 100        }
 101
 102        /* Test the capability checks. */
 103        printf("\tiopl(3)\n");
 104        if (iopl(3) != 0)
 105                err(1, "iopl(3)");
 106
 107        printf("\tDrop privileges\n");
 108        if (setresuid(1, 1, 1) != 0) {
 109                printf("[WARN]\tDropping privileges failed\n");
 110                goto done;
 111        }
 112
 113        printf("[RUN]\tiopl(3) unprivileged but with IOPL==3\n");
 114        if (iopl(3) != 0) {
 115                printf("[FAIL]\tiopl(3) should work if iopl is already 3 even if unprivileged\n");
 116                nerrs++;
 117        }
 118
 119        printf("[RUN]\tiopl(0) unprivileged\n");
 120        if (iopl(0) != 0) {
 121                printf("[FAIL]\tiopl(0) should work if iopl is already 3 even if unprivileged\n");
 122                nerrs++;
 123        }
 124
 125        printf("[RUN]\tiopl(3) unprivileged\n");
 126        if (iopl(3) == 0) {
 127                printf("[FAIL]\tiopl(3) should fail if when unprivileged if iopl==0\n");
 128                nerrs++;
 129        } else {
 130                printf("[OK]\tFailed as expected\n");
 131        }
 132
 133done:
 134        return nerrs ? 1 : 0;
 135}
 136
 137