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

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