1 #include <sys/types.h>
2 #include <sys/ioctl.h>
3 #include "qemu-common.h"
4
5 #ifdef CONFIG_KVM_GS_RESTORE
6
7 #define INVALID_GS_REG 0xffff
8 #define KVM_GS_RESTORE_NODETECTED 0x1
9 #define KVM_GS_RESTORE_NO 0x2
10 #define KVM_GS_RESTORE_YES 0x3
11 int initial_gs = INVALID_GS_REG;
12 int gs_need_restore = KVM_GS_RESTORE_NODETECTED;
13
restoregs(int gs)14 static void restoregs(int gs)
15 {
16 asm("movl %0, %%gs"::"r"(gs));
17 }
18
_getgs()19 static unsigned int _getgs()
20 {
21 unsigned int gs = 0;
22 asm("movl %%gs,%0" :"=r"(gs):);
23 return gs;
24 }
25
26 /* No fprintf or any system call before the gs is restored successfully */
check_and_restore_gs(void)27 static void check_and_restore_gs(void)
28 {
29 if (gs_need_restore == KVM_GS_RESTORE_NO)
30 return;
31
32 restoregs(initial_gs);
33 }
34
35 struct sigact_status
36 {
37 unsigned int sigaction:1;
38 __sighandler_t old_handler;
39 void (*old_sigaction) (int, siginfo_t *, void *);
40 };
41 static struct sigact_status o_sigact[SIGUNUSED];
42
temp_sig_handler(int signum)43 static void temp_sig_handler(int signum)
44 {
45 /* !!! must restore gs firstly */
46 check_and_restore_gs();
47
48 if (signum < SIGHUP || signum >= SIGUNUSED)
49 {
50 fprintf(stderr, "Invalid signal %x in temp_sig_handler\n", signum);
51 abort();
52 }
53
54 if ( !o_sigact[signum].sigaction && o_sigact[signum].old_handler)
55 o_sigact[signum].old_handler(signum);
56 else
57 {
58 fprintf(stderr, "Invalid signal in temp_sig_handler: "
59 "signal %x sa_info %s!!\n",
60 signum, o_sigact[signum].sigaction ? "set":"not set" );
61 abort();
62 }
63 }
64
temp_sig_sigaction(int signum,siginfo_t * info,void * ucontext)65 static void temp_sig_sigaction(int signum, siginfo_t *info, void *ucontext)
66 {
67 /* !!! must restore gs firstly */
68 check_and_restore_gs();
69
70 if (signum < SIGHUP || signum >= SIGUNUSED)
71 {
72 fprintf(stderr, "Invalid signal %x in temp_sig_sigaction\n", signum);
73 abort();
74 }
75
76 if ( o_sigact[signum].sigaction && o_sigact[signum].old_sigaction )
77 o_sigact[signum].old_sigaction(signum, info, ucontext);
78 else
79 {
80 fprintf(stderr, "Invalid signal in temp_sig_sigaction: "
81 "signal %x sa_info %s!!\n",
82 signum, o_sigact[signum].sigaction ? "set":"not set" );
83 abort();
84 }
85 }
86
87 static int sig_taken = 0;
88
take_signal_handler(void)89 static int take_signal_handler(void)
90 {
91 int i;
92
93 if (gs_need_restore == KVM_GS_RESTORE_NO)
94 return 0;
95 if (sig_taken)
96 return 0;
97
98 memset(o_sigact, 0, sizeof(o_sigact));
99
100 /* SIGHUP is 1 in POSIX */
101 for (i = SIGHUP; i < SIGUNUSED; i++)
102 {
103 int sigret;
104 struct sigaction act, old_act;
105
106 sigret = sigaction(i, NULL, &old_act);
107 if (sigret)
108 continue;
109 /* We don't need take the handler for default or ignore signals */
110 if ( !(old_act.sa_flags & SA_SIGINFO) &&
111 ((old_act.sa_handler == SIG_IGN ) ||
112 (old_act.sa_handler == SIG_DFL)))
113 continue;
114
115 memcpy(&act, &old_act, sizeof(struct sigaction));
116
117 if (old_act.sa_flags & SA_SIGINFO)
118 {
119 o_sigact[i].old_sigaction = old_act.sa_sigaction;
120 o_sigact[i].sigaction = 1;
121 act.sa_sigaction = temp_sig_sigaction;
122 }
123 else
124 {
125 o_sigact[i].old_handler = old_act.sa_handler;
126 act.sa_handler = temp_sig_handler;
127 }
128
129 sigaction(i, &act, NULL);
130 continue;
131 }
132 sig_taken = 1;
133 return 1;
134 }
135
gs_base_pre_run(void)136 int gs_base_pre_run(void)
137 {
138 if (unlikely(initial_gs == INVALID_GS_REG) )
139 {
140 initial_gs = _getgs();
141 /*
142 * As 2.6.35-28 lucid will get correct gs but clobbered GS_BASE
143 * we have to always re-write the gs base
144 */
145 if (initial_gs == 0x0)
146 gs_need_restore = KVM_GS_RESTORE_NO;
147 else
148 gs_need_restore = KVM_GS_RESTORE_YES;
149 }
150
151 take_signal_handler();
152 return 0;
153 }
154
gs_base_post_run(void)155 int gs_base_post_run(void)
156 {
157 check_and_restore_gs();
158 return 0;
159 }
160
161 /*
162 * ioctl may update errno, which is in thread local storage and
163 * requires gs register, we have to provide our own ioctl
164 * XXX should "call %%gs:$0x10" be replaced with call to vsyscall
165 * page, which is more generic and clean?
166 */
no_gs_ioctl(int fd,int type,void * arg)167 int no_gs_ioctl(int fd, int type, void *arg)
168 {
169 int ret=0;
170
171 asm(
172 "movl %3, %%edx;\n"
173 "movl %2, %%ecx;\n"
174 "movl %1, %%ebx;\n"
175 "movl $0x36, %%eax;\n"
176 "call *%%gs:0x10;\n"
177 "movl %%eax, %0\n"
178 : "=m"(ret)
179 :"m"(fd),"m"(type),"m"(arg)
180 :"%edx","%ecx","%eax","%ebx"
181 );
182
183 return ret;
184 }
185
186 #endif
187
188