1/*
2 * entry_from_vm86.c - tests kernel entries from vm86 mode
3 * Copyright (c) 2014-2015 Andrew Lutomirski
4 *
5 * This exercises a few paths that need to special-case vm86 mode.
6 *
7 * GPL v2.
8 */
9
10#define _GNU_SOURCE
11
12#include <assert.h>
13#include <stdlib.h>
14#include <sys/syscall.h>
15#include <sys/signal.h>
16#include <sys/ucontext.h>
17#include <unistd.h>
18#include <stdio.h>
19#include <string.h>
20#include <inttypes.h>
21#include <sys/mman.h>
22#include <err.h>
23#include <stddef.h>
24#include <stdbool.h>
25#include <errno.h>
26#include <sys/vm86.h>
27
28static unsigned long load_addr = 0x10000;
29static int nerrs = 0;
30
31asm (
32	".pushsection .rodata\n\t"
33	".type vmcode_bound, @object\n\t"
34	"vmcode:\n\t"
35	"vmcode_bound:\n\t"
36	".code16\n\t"
37	"bound %ax, (2048)\n\t"
38	"int3\n\t"
39	"vmcode_sysenter:\n\t"
40	"sysenter\n\t"
41	".size vmcode, . - vmcode\n\t"
42	"end_vmcode:\n\t"
43	".code32\n\t"
44	".popsection"
45	);
46
47extern unsigned char vmcode[], end_vmcode[];
48extern unsigned char vmcode_bound[], vmcode_sysenter[];
49
50static void do_test(struct vm86plus_struct *v86, unsigned long eip,
51		    const char *text)
52{
53	long ret;
54
55	printf("[RUN]\t%s from vm86 mode\n", text);
56	v86->regs.eip = eip;
57	ret = vm86(VM86_ENTER, v86);
58
59	if (ret == -1 && errno == ENOSYS) {
60		printf("[SKIP]\tvm86 not supported\n");
61		return;
62	}
63
64	if (VM86_TYPE(ret) == VM86_INTx) {
65		char trapname[32];
66		int trapno = VM86_ARG(ret);
67		if (trapno == 13)
68			strcpy(trapname, "GP");
69		else if (trapno == 5)
70			strcpy(trapname, "BR");
71		else if (trapno == 14)
72			strcpy(trapname, "PF");
73		else
74			sprintf(trapname, "%d", trapno);
75
76		printf("[OK]\tExited vm86 mode due to #%s\n", trapname);
77	} else if (VM86_TYPE(ret) == VM86_UNKNOWN) {
78		printf("[OK]\tExited vm86 mode due to unhandled GP fault\n");
79	} else {
80		printf("[OK]\tExited vm86 mode due to type %ld, arg %ld\n",
81		       VM86_TYPE(ret), VM86_ARG(ret));
82	}
83}
84
85int main(void)
86{
87	struct vm86plus_struct v86;
88	unsigned char *addr = mmap((void *)load_addr, 4096,
89				   PROT_READ | PROT_WRITE | PROT_EXEC,
90				   MAP_ANONYMOUS | MAP_PRIVATE, -1,0);
91	if (addr != (unsigned char *)load_addr)
92		err(1, "mmap");
93
94	memcpy(addr, vmcode, end_vmcode - vmcode);
95	addr[2048] = 2;
96	addr[2050] = 3;
97
98	memset(&v86, 0, sizeof(v86));
99
100	v86.regs.cs = load_addr / 16;
101	v86.regs.ss = load_addr / 16;
102	v86.regs.ds = load_addr / 16;
103	v86.regs.es = load_addr / 16;
104
105	assert((v86.regs.cs & 3) == 0);	/* Looks like RPL = 0 */
106
107	/* #BR -- should deliver SIG??? */
108	do_test(&v86, vmcode_bound - vmcode, "#BR");
109
110	/* SYSENTER -- should cause #GP or #UD depending on CPU */
111	do_test(&v86, vmcode_sysenter - vmcode, "SYSENTER");
112
113	return (nerrs == 0 ? 0 : 1);
114}
115