xtensa: fix high memory/reserved memory collision
[cris-mirror.git] / tools / testing / selftests / x86 / single_step_syscall.c
bloba48da95c18fdf1f0ea46e7cb628ff9a9caba931b
1 /*
2 * single_step_syscall.c - single-steps various x86 syscalls
3 * Copyright (c) 2014-2015 Andrew Lutomirski
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.
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.
14 * This is a very simple series of tests that makes system calls with
15 * the TF flag set. This exercises some nasty kernel code in the
16 * SYSENTER case: SYSENTER does not clear TF, so SYSENTER with TF set
17 * immediately issues #DB from CPL 0. This requires special handling in
18 * the kernel.
21 #define _GNU_SOURCE
23 #include <sys/time.h>
24 #include <time.h>
25 #include <stdlib.h>
26 #include <sys/syscall.h>
27 #include <unistd.h>
28 #include <stdio.h>
29 #include <string.h>
30 #include <inttypes.h>
31 #include <sys/mman.h>
32 #include <sys/signal.h>
33 #include <sys/ucontext.h>
34 #include <asm/ldt.h>
35 #include <err.h>
36 #include <setjmp.h>
37 #include <stddef.h>
38 #include <stdbool.h>
39 #include <sys/ptrace.h>
40 #include <sys/user.h>
42 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
43 int flags)
45 struct sigaction sa;
46 memset(&sa, 0, sizeof(sa));
47 sa.sa_sigaction = handler;
48 sa.sa_flags = SA_SIGINFO | flags;
49 sigemptyset(&sa.sa_mask);
50 if (sigaction(sig, &sa, 0))
51 err(1, "sigaction");
54 static volatile sig_atomic_t sig_traps;
56 #ifdef __x86_64__
57 # define REG_IP REG_RIP
58 # define WIDTH "q"
59 # define INT80_CLOBBERS "r8", "r9", "r10", "r11"
60 #else
61 # define REG_IP REG_EIP
62 # define WIDTH "l"
63 # define INT80_CLOBBERS
64 #endif
66 static unsigned long get_eflags(void)
68 unsigned long eflags;
69 asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags));
70 return eflags;
73 static void set_eflags(unsigned long eflags)
75 asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH
76 : : "rm" (eflags) : "flags");
79 #define X86_EFLAGS_TF (1UL << 8)
81 static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
83 ucontext_t *ctx = (ucontext_t*)ctx_void;
85 if (get_eflags() & X86_EFLAGS_TF) {
86 set_eflags(get_eflags() & ~X86_EFLAGS_TF);
87 printf("[WARN]\tSIGTRAP handler had TF set\n");
88 _exit(1);
91 sig_traps++;
93 if (sig_traps == 10000 || sig_traps == 10001) {
94 printf("[WARN]\tHit %d SIGTRAPs with si_addr 0x%lx, ip 0x%lx\n",
95 (int)sig_traps,
96 (unsigned long)info->si_addr,
97 (unsigned long)ctx->uc_mcontext.gregs[REG_IP]);
101 static void check_result(void)
103 unsigned long new_eflags = get_eflags();
104 set_eflags(new_eflags & ~X86_EFLAGS_TF);
106 if (!sig_traps) {
107 printf("[FAIL]\tNo SIGTRAP\n");
108 exit(1);
111 if (!(new_eflags & X86_EFLAGS_TF)) {
112 printf("[FAIL]\tTF was cleared\n");
113 exit(1);
116 printf("[OK]\tSurvived with TF set and %d traps\n", (int)sig_traps);
117 sig_traps = 0;
120 int main()
122 int tmp;
124 sethandler(SIGTRAP, sigtrap, 0);
126 printf("[RUN]\tSet TF and check nop\n");
127 set_eflags(get_eflags() | X86_EFLAGS_TF);
128 asm volatile ("nop");
129 check_result();
131 #ifdef __x86_64__
132 printf("[RUN]\tSet TF and check syscall-less opportunistic sysret\n");
133 set_eflags(get_eflags() | X86_EFLAGS_TF);
134 extern unsigned char post_nop[];
135 asm volatile ("pushf" WIDTH "\n\t"
136 "pop" WIDTH " %%r11\n\t"
137 "nop\n\t"
138 "post_nop:"
139 : : "c" (post_nop) : "r11");
140 check_result();
141 #endif
143 printf("[RUN]\tSet TF and check int80\n");
144 set_eflags(get_eflags() | X86_EFLAGS_TF);
145 asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid)
146 : INT80_CLOBBERS);
147 check_result();
150 * This test is particularly interesting if fast syscalls use
151 * SYSENTER: it triggers a nasty design flaw in SYSENTER.
152 * Specifically, SYSENTER does not clear TF, so either SYSENTER
153 * or the next instruction traps at CPL0. (Of course, Intel
154 * mostly forgot to document exactly what happens here.) So we
155 * get a CPL0 fault with usergs (on 64-bit kernels) and possibly
156 * no stack. The only sane way the kernel can possibly handle
157 * it is to clear TF on return from the #DB handler, but this
158 * happens way too early to set TF in the saved pt_regs, so the
159 * kernel has to do something clever to avoid losing track of
160 * the TF bit.
162 * Needless to say, we've had bugs in this area.
164 syscall(SYS_getpid); /* Force symbol binding without TF set. */
165 printf("[RUN]\tSet TF and check a fast syscall\n");
166 set_eflags(get_eflags() | X86_EFLAGS_TF);
167 syscall(SYS_getpid);
168 check_result();
170 /* Now make sure that another fast syscall doesn't set TF again. */
171 printf("[RUN]\tFast syscall with TF cleared\n");
172 fflush(stdout); /* Force a syscall */
173 if (get_eflags() & X86_EFLAGS_TF) {
174 printf("[FAIL]\tTF is now set\n");
175 exit(1);
177 if (sig_traps) {
178 printf("[FAIL]\tGot SIGTRAP\n");
179 exit(1);
181 printf("[OK]\tNothing unexpected happened\n");
183 return 0;