Commit | Line | Data |
---|---|---|
a9c909ce AL |
1 | /* |
2 | * syscall_nt.c - checks syscalls with NT set | |
3 | * Copyright (c) 2014-2015 Andrew Lutomirski | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms and conditions of the GNU General Public License, | |
7 | * version 2, as published by the Free Software Foundation. | |
8 | * | |
9 | * This program is distributed in the hope it will be useful, but | |
10 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
12 | * General Public License for more details. | |
13 | * | |
14 | * Some obscure user-space code requires the ability to make system calls | |
15 | * with FLAGS.NT set. Make sure it works. | |
16 | */ | |
17 | ||
18 | #include <stdio.h> | |
19 | #include <unistd.h> | |
a318beea AL |
20 | #include <string.h> |
21 | #include <signal.h> | |
22 | #include <err.h> | |
a9c909ce AL |
23 | #include <sys/syscall.h> |
24 | #include <asm/processor-flags.h> | |
25 | ||
26 | #ifdef __x86_64__ | |
27 | # define WIDTH "q" | |
28 | #else | |
29 | # define WIDTH "l" | |
30 | #endif | |
31 | ||
a318beea AL |
32 | static unsigned int nerrs; |
33 | ||
a9c909ce AL |
34 | static unsigned long get_eflags(void) |
35 | { | |
36 | unsigned long eflags; | |
37 | asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags)); | |
38 | return eflags; | |
39 | } | |
40 | ||
41 | static void set_eflags(unsigned long eflags) | |
42 | { | |
43 | asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH | |
44 | : : "rm" (eflags) : "flags"); | |
45 | } | |
46 | ||
a318beea AL |
47 | static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), |
48 | int flags) | |
a9c909ce | 49 | { |
a318beea AL |
50 | struct sigaction sa; |
51 | memset(&sa, 0, sizeof(sa)); | |
52 | sa.sa_sigaction = handler; | |
53 | sa.sa_flags = SA_SIGINFO | flags; | |
54 | sigemptyset(&sa.sa_mask); | |
55 | if (sigaction(sig, &sa, 0)) | |
56 | err(1, "sigaction"); | |
57 | } | |
58 | ||
59 | static void sigtrap(int sig, siginfo_t *si, void *ctx_void) | |
60 | { | |
61 | } | |
62 | ||
63 | static void do_it(unsigned long extraflags) | |
64 | { | |
65 | unsigned long flags; | |
66 | ||
67 | set_eflags(get_eflags() | extraflags); | |
a9c909ce | 68 | syscall(SYS_getpid); |
a318beea AL |
69 | flags = get_eflags(); |
70 | if ((flags & extraflags) == extraflags) { | |
71 | printf("[OK]\tThe syscall worked and flags are still set\n"); | |
a9c909ce | 72 | } else { |
a318beea AL |
73 | printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n", |
74 | flags, extraflags); | |
75 | nerrs++; | |
a9c909ce AL |
76 | } |
77 | } | |
a318beea AL |
78 | |
79 | int main(void) | |
80 | { | |
81 | printf("[RUN]\tSet NT and issue a syscall\n"); | |
82 | do_it(X86_EFLAGS_NT); | |
83 | ||
84 | /* | |
85 | * Now try it again with TF set -- TF forces returns via IRET in all | |
86 | * cases except non-ptregs-using 64-bit full fast path syscalls. | |
87 | */ | |
88 | ||
89 | sethandler(SIGTRAP, sigtrap, 0); | |
90 | ||
91 | printf("[RUN]\tSet NT|TF and issue a syscall\n"); | |
92 | do_it(X86_EFLAGS_NT | X86_EFLAGS_TF); | |
93 | ||
94 | return nerrs == 0 ? 0 : 1; | |
95 | } |