1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-only
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * syscall_nt.c - checks syscalls with NT set
4*4882a593Smuzhiyun * Copyright (c) 2014-2015 Andrew Lutomirski
5*4882a593Smuzhiyun *
6*4882a593Smuzhiyun * Some obscure user-space code requires the ability to make system calls
7*4882a593Smuzhiyun * with FLAGS.NT set. Make sure it works.
8*4882a593Smuzhiyun */
9*4882a593Smuzhiyun
10*4882a593Smuzhiyun #include <stdio.h>
11*4882a593Smuzhiyun #include <unistd.h>
12*4882a593Smuzhiyun #include <string.h>
13*4882a593Smuzhiyun #include <signal.h>
14*4882a593Smuzhiyun #include <err.h>
15*4882a593Smuzhiyun #include <sys/syscall.h>
16*4882a593Smuzhiyun
17*4882a593Smuzhiyun #include "helpers.h"
18*4882a593Smuzhiyun
19*4882a593Smuzhiyun static unsigned int nerrs;
20*4882a593Smuzhiyun
sethandler(int sig,void (* handler)(int,siginfo_t *,void *),int flags)21*4882a593Smuzhiyun static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
22*4882a593Smuzhiyun int flags)
23*4882a593Smuzhiyun {
24*4882a593Smuzhiyun struct sigaction sa;
25*4882a593Smuzhiyun memset(&sa, 0, sizeof(sa));
26*4882a593Smuzhiyun sa.sa_sigaction = handler;
27*4882a593Smuzhiyun sa.sa_flags = SA_SIGINFO | flags;
28*4882a593Smuzhiyun sigemptyset(&sa.sa_mask);
29*4882a593Smuzhiyun if (sigaction(sig, &sa, 0))
30*4882a593Smuzhiyun err(1, "sigaction");
31*4882a593Smuzhiyun }
32*4882a593Smuzhiyun
sigtrap(int sig,siginfo_t * si,void * ctx_void)33*4882a593Smuzhiyun static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
34*4882a593Smuzhiyun {
35*4882a593Smuzhiyun }
36*4882a593Smuzhiyun
do_it(unsigned long extraflags)37*4882a593Smuzhiyun static void do_it(unsigned long extraflags)
38*4882a593Smuzhiyun {
39*4882a593Smuzhiyun unsigned long flags;
40*4882a593Smuzhiyun
41*4882a593Smuzhiyun set_eflags(get_eflags() | extraflags);
42*4882a593Smuzhiyun syscall(SYS_getpid);
43*4882a593Smuzhiyun flags = get_eflags();
44*4882a593Smuzhiyun set_eflags(X86_EFLAGS_IF | X86_EFLAGS_FIXED);
45*4882a593Smuzhiyun if ((flags & extraflags) == extraflags) {
46*4882a593Smuzhiyun printf("[OK]\tThe syscall worked and flags are still set\n");
47*4882a593Smuzhiyun } else {
48*4882a593Smuzhiyun printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n",
49*4882a593Smuzhiyun flags, extraflags);
50*4882a593Smuzhiyun nerrs++;
51*4882a593Smuzhiyun }
52*4882a593Smuzhiyun }
53*4882a593Smuzhiyun
main(void)54*4882a593Smuzhiyun int main(void)
55*4882a593Smuzhiyun {
56*4882a593Smuzhiyun printf("[RUN]\tSet NT and issue a syscall\n");
57*4882a593Smuzhiyun do_it(X86_EFLAGS_NT);
58*4882a593Smuzhiyun
59*4882a593Smuzhiyun printf("[RUN]\tSet AC and issue a syscall\n");
60*4882a593Smuzhiyun do_it(X86_EFLAGS_AC);
61*4882a593Smuzhiyun
62*4882a593Smuzhiyun printf("[RUN]\tSet NT|AC and issue a syscall\n");
63*4882a593Smuzhiyun do_it(X86_EFLAGS_NT | X86_EFLAGS_AC);
64*4882a593Smuzhiyun
65*4882a593Smuzhiyun /*
66*4882a593Smuzhiyun * Now try it again with TF set -- TF forces returns via IRET in all
67*4882a593Smuzhiyun * cases except non-ptregs-using 64-bit full fast path syscalls.
68*4882a593Smuzhiyun */
69*4882a593Smuzhiyun
70*4882a593Smuzhiyun sethandler(SIGTRAP, sigtrap, 0);
71*4882a593Smuzhiyun
72*4882a593Smuzhiyun printf("[RUN]\tSet TF and issue a syscall\n");
73*4882a593Smuzhiyun do_it(X86_EFLAGS_TF);
74*4882a593Smuzhiyun
75*4882a593Smuzhiyun printf("[RUN]\tSet NT|TF and issue a syscall\n");
76*4882a593Smuzhiyun do_it(X86_EFLAGS_NT | X86_EFLAGS_TF);
77*4882a593Smuzhiyun
78*4882a593Smuzhiyun printf("[RUN]\tSet AC|TF and issue a syscall\n");
79*4882a593Smuzhiyun do_it(X86_EFLAGS_AC | X86_EFLAGS_TF);
80*4882a593Smuzhiyun
81*4882a593Smuzhiyun printf("[RUN]\tSet NT|AC|TF and issue a syscall\n");
82*4882a593Smuzhiyun do_it(X86_EFLAGS_NT | X86_EFLAGS_AC | X86_EFLAGS_TF);
83*4882a593Smuzhiyun
84*4882a593Smuzhiyun /*
85*4882a593Smuzhiyun * Now try DF. This is evil and it's plausible that we will crash
86*4882a593Smuzhiyun * glibc, but glibc would have to do something rather surprising
87*4882a593Smuzhiyun * for this to happen.
88*4882a593Smuzhiyun */
89*4882a593Smuzhiyun printf("[RUN]\tSet DF and issue a syscall\n");
90*4882a593Smuzhiyun do_it(X86_EFLAGS_DF);
91*4882a593Smuzhiyun
92*4882a593Smuzhiyun printf("[RUN]\tSet TF|DF and issue a syscall\n");
93*4882a593Smuzhiyun do_it(X86_EFLAGS_TF | X86_EFLAGS_DF);
94*4882a593Smuzhiyun
95*4882a593Smuzhiyun return nerrs == 0 ? 0 : 1;
96*4882a593Smuzhiyun }
97