2 * entry_from_vm86.c - tests kernel entries from vm86 mode
3 * Copyright (c) 2014-2015 Andrew Lutomirski
5 * This exercises a few paths that need to special-case vm86 mode.
14 #include <sys/syscall.h>
15 #include <sys/signal.h>
16 #include <sys/ucontext.h>
28 static unsigned long load_addr = 0x10000;
31 static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
35 memset(&sa, 0, sizeof(sa));
36 sa.sa_sigaction = handler;
37 sa.sa_flags = SA_SIGINFO | flags;
38 sigemptyset(&sa.sa_mask);
39 if (sigaction(sig, &sa, 0))
43 static void clearhandler(int sig)
46 memset(&sa, 0, sizeof(sa));
47 sa.sa_handler = SIG_DFL;
48 sigemptyset(&sa.sa_mask);
49 if (sigaction(sig, &sa, 0))
53 static sig_atomic_t got_signal;
55 static void sighandler(int sig, siginfo_t *info, void *ctx_void)
57 ucontext_t *ctx = (ucontext_t*)ctx_void;
59 if (ctx->uc_mcontext.gregs[REG_EFL] & X86_EFLAGS_VM ||
60 (ctx->uc_mcontext.gregs[REG_CS] & 3) != 3) {
61 printf("[FAIL]\tSignal frame should not reflect vm86 mode\n");
68 else if (sig == SIGILL)
71 signame = "unexpected signal";
73 printf("[INFO]\t%s: FLAGS = 0x%lx, CS = 0x%hx\n", signame,
74 (unsigned long)ctx->uc_mcontext.gregs[REG_EFL],
75 (unsigned short)ctx->uc_mcontext.gregs[REG_CS]);
81 ".pushsection .rodata\n\t"
82 ".type vmcode_bound, @object\n\t"
86 "bound %ax, (2048)\n\t"
88 "vmcode_sysenter:\n\t"
98 ".size vmcode, . - vmcode\n\t"
104 extern unsigned char vmcode[], end_vmcode[];
105 extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[],
106 vmcode_sti[], vmcode_int3[], vmcode_int80[];
108 /* Returns false if the test was skipped. */
109 static bool do_test(struct vm86plus_struct *v86, unsigned long eip,
110 unsigned int rettype, unsigned int retarg,
115 printf("[RUN]\t%s from vm86 mode\n", text);
117 ret = vm86(VM86_ENTER, v86);
119 if (ret == -1 && (errno == ENOSYS || errno == EPERM)) {
120 printf("[SKIP]\tvm86 %s\n",
121 errno == ENOSYS ? "not supported" : "not allowed");
125 if (VM86_TYPE(ret) == VM86_INTx) {
127 int trapno = VM86_ARG(ret);
129 strcpy(trapname, "GP");
130 else if (trapno == 5)
131 strcpy(trapname, "BR");
132 else if (trapno == 14)
133 strcpy(trapname, "PF");
135 sprintf(trapname, "%d", trapno);
137 printf("[INFO]\tExited vm86 mode due to #%s\n", trapname);
138 } else if (VM86_TYPE(ret) == VM86_UNKNOWN) {
139 printf("[INFO]\tExited vm86 mode due to unhandled GP fault\n");
140 } else if (VM86_TYPE(ret) == VM86_TRAP) {
141 printf("[INFO]\tExited vm86 mode due to a trap (arg=%ld)\n",
143 } else if (VM86_TYPE(ret) == VM86_SIGNAL) {
144 printf("[INFO]\tExited vm86 mode due to a signal\n");
145 } else if (VM86_TYPE(ret) == VM86_STI) {
146 printf("[INFO]\tExited vm86 mode due to STI\n");
148 printf("[INFO]\tExited vm86 mode due to type %ld, arg %ld\n",
149 VM86_TYPE(ret), VM86_ARG(ret));
153 (VM86_TYPE(ret) == rettype && VM86_ARG(ret) == retarg)) {
154 printf("[OK]\tReturned correctly\n");
156 printf("[FAIL]\tIncorrect return reason\n");
165 struct vm86plus_struct v86;
166 unsigned char *addr = mmap((void *)load_addr, 4096,
167 PROT_READ | PROT_WRITE | PROT_EXEC,
168 MAP_ANONYMOUS | MAP_PRIVATE, -1,0);
169 if (addr != (unsigned char *)load_addr)
172 memcpy(addr, vmcode, end_vmcode - vmcode);
176 memset(&v86, 0, sizeof(v86));
178 v86.regs.cs = load_addr / 16;
179 v86.regs.ss = load_addr / 16;
180 v86.regs.ds = load_addr / 16;
181 v86.regs.es = load_addr / 16;
183 assert((v86.regs.cs & 3) == 0); /* Looks like RPL = 0 */
185 /* #BR -- should deliver SIG??? */
186 do_test(&v86, vmcode_bound - vmcode, VM86_INTx, 5, "#BR");
189 * SYSENTER -- should cause #GP or #UD depending on CPU.
190 * Expected return type -1 means that we shouldn't validate
191 * the vm86 return value. This will avoid problems on non-SEP
194 sethandler(SIGILL, sighandler, 0);
195 do_test(&v86, vmcode_sysenter - vmcode, -1, 0, "SYSENTER");
196 clearhandler(SIGILL);
199 * SYSCALL would be a disaster in VM86 mode. Fortunately,
200 * there is no kernel that both enables SYSCALL and sets
201 * EFER.SCE, so it's #UD on all systems. But vm86 is
202 * buggy (or has a "feature"), so the SIGILL will actually
205 sethandler(SIGILL, sighandler, 0);
206 do_test(&v86, vmcode_syscall - vmcode, VM86_SIGNAL, 0, "SYSCALL");
207 clearhandler(SIGILL);
209 /* STI with VIP set */
210 v86.regs.eflags |= X86_EFLAGS_VIP;
211 v86.regs.eflags &= ~X86_EFLAGS_IF;
212 do_test(&v86, vmcode_sti - vmcode, VM86_STI, 0, "STI with VIP set");
214 /* INT3 -- should cause #BP */
215 do_test(&v86, vmcode_int3 - vmcode, VM86_TRAP, 3, "INT3");
217 /* INT80 -- should exit with "INTx 0x80" */
218 v86.regs.eax = (unsigned int)-1;
219 do_test(&v86, vmcode_int80 - vmcode, VM86_INTx, 0x80, "int80");
221 /* Execute a null pointer */
224 sethandler(SIGSEGV, sighandler, 0);
226 if (do_test(&v86, 0, VM86_SIGNAL, 0, "Execute null pointer") &&
228 printf("[FAIL]\tDid not receive SIGSEGV\n");
231 clearhandler(SIGSEGV);
233 return (nerrs == 0 ? 0 : 1);