// SPDX-License-Identifier: GPL-2.0-only
/*
 * syscall_nt.c - checks syscalls with NT set
 * Copyright (c) 2014-2015 Andrew Lutomirski
 *
 * Some obscure user-space code requires the ability to make system calls
 * with FLAGS.NT set.  Make sure it works.
 */

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <err.h>
#include <sys/syscall.h>

#include "helpers.h"

static unsigned int nerrs;

static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
{
}

static void do_it(unsigned long extraflags)
{
        unsigned long flags;

        set_eflags(get_eflags() | extraflags);
        syscall(SYS_getpid);
        flags = get_eflags();
        set_eflags(X86_EFLAGS_IF | X86_EFLAGS_FIXED);
        if ((flags & extraflags) == extraflags) {
                printf("[OK]\tThe syscall worked and flags are still set\n");
        } else {
                printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n",
                       flags, extraflags);
                nerrs++;
        }
}

int main(void)
{
        printf("[RUN]\tSet NT and issue a syscall\n");
        do_it(X86_EFLAGS_NT);

        printf("[RUN]\tSet AC and issue a syscall\n");
        do_it(X86_EFLAGS_AC);

        printf("[RUN]\tSet NT|AC and issue a syscall\n");
        do_it(X86_EFLAGS_NT | X86_EFLAGS_AC);

        /*
         * Now try it again with TF set -- TF forces returns via IRET in all
         * cases except non-ptregs-using 64-bit full fast path syscalls.
         */

        sethandler(SIGTRAP, sigtrap, 0);

        printf("[RUN]\tSet TF and issue a syscall\n");
        do_it(X86_EFLAGS_TF);

        printf("[RUN]\tSet NT|TF and issue a syscall\n");
        do_it(X86_EFLAGS_NT | X86_EFLAGS_TF);

        printf("[RUN]\tSet AC|TF and issue a syscall\n");
        do_it(X86_EFLAGS_AC | X86_EFLAGS_TF);

        printf("[RUN]\tSet NT|AC|TF and issue a syscall\n");
        do_it(X86_EFLAGS_NT | X86_EFLAGS_AC | X86_EFLAGS_TF);

        /*
         * Now try DF.  This is evil and it's plausible that we will crash
         * glibc, but glibc would have to do something rather surprising
         * for this to happen.
         */
        printf("[RUN]\tSet DF and issue a syscall\n");
        do_it(X86_EFLAGS_DF);

        printf("[RUN]\tSet TF|DF and issue a syscall\n");
        do_it(X86_EFLAGS_TF | X86_EFLAGS_DF);

        return nerrs == 0 ? 0 : 1;
}