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