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#include <sys/types.h>
#include <sys/ioctl.h>
#include "qemu-common.h"
#ifdef CONFIG_KVM_GS_RESTORE
#define INVALID_GS_REG 0xffff
#define KVM_GS_RESTORE_NODETECTED 0x1
#define KVM_GS_RESTORE_NO 0x2
#define KVM_GS_RESTORE_YES 0x3
int initial_gs = INVALID_GS_REG;
int gs_need_restore = KVM_GS_RESTORE_NODETECTED;
static void restoregs(int gs)
{
asm("movl %0, %%gs"::"r"(gs));
}
static unsigned int _getgs()
{
unsigned int gs = 0;
asm("movl %%gs,%0" :"=r"(gs):);
return gs;
}
/* No fprintf or any system call before the gs is restored successfully */
static void check_and_restore_gs(void)
{
if (gs_need_restore == KVM_GS_RESTORE_NO)
return;
restoregs(initial_gs);
}
static struct sigaction old_alarm_act, old_gio_act, old_pipe_act,old_usr1_act, old_chld_act;
static void temp_sig_handler(int host_signum)
{
/* !!! must restore gs firstly */
check_and_restore_gs();
switch (host_signum)
{
case SIGALRM:
old_alarm_act.sa_handler(host_signum);
break;
case SIGIO:
old_gio_act.sa_handler(host_signum);
break;
case SIGUSR1:
old_usr1_act.sa_handler(host_signum);
break;
case SIGPIPE:
old_pipe_act.sa_handler(host_signum);
break;
case SIGCHLD:
old_chld_act.sa_handler(host_signum);
break;
default:
fprintf(stderr, "Not take signal %x!!\n", host_signum);
break;
}
}
static int sig_taken = 0;
static int take_signal_handler(void)
{
struct sigaction act;
int ret;
if (gs_need_restore == KVM_GS_RESTORE_NO)
return 0;
if (sig_taken)
return 0;
sig_taken = 1;
sigfillset(&act.sa_mask);
act.sa_flags = 0;
act.sa_handler = temp_sig_handler;
/* Did we missed any other signal ? */
sigaction(SIGALRM, &act, &old_alarm_act);
sigaction(SIGIO, &act, &old_gio_act);
sigaction(SIGUSR1, &act, &old_usr1_act);
sigaction(SIGPIPE, &act, &old_pipe_act);
act.sa_flags = SA_NOCLDSTOP;
sigaction(SIGCHLD, &act, &old_chld_act);
return 1;
}
int gs_base_pre_run(void)
{
if (unlikely(initial_gs == INVALID_GS_REG) )
{
initial_gs = _getgs();
/*
* As 2.6.35-28 lucid will get correct gs but clobbered GS_BASE
* we have to always re-write the gs base
*/
if (initial_gs == 0x0)
gs_need_restore = KVM_GS_RESTORE_NO;
else
gs_need_restore = KVM_GS_RESTORE_YES;
}
take_signal_handler();
return 0;
}
int gs_base_post_run(void)
{
check_and_restore_gs();
return 0;
}
/*
* ioctl may update errno, which is in thread local storage and
* requires gs register, we have to provide our own ioctl
* XXX should "call %%gs:$0x10" be replaced with call to vsyscall
* page, which is more generic and clean?
*/
int no_gs_ioctl(int fd, int type, void *arg)
{
int ret=0;
asm(
"movl %3, %%edx;\n"
"movl %2, %%ecx;\n"
"movl %1, %%ebx;\n"
"movl $0x36, %%eax;\n"
"call *%%gs:0x10;\n"
"movl %%eax, %0\n"
: "=m"(ret)
:"m"(fd),"m"(type),"m"(arg)
:"%edx","%ecx","%eax","%ebx"
);
return ret;
}
#endif
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