// 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>

#include "helpers.h"

static int nerrs = 0;

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;
}