<URL:
http://funnyman:26776/markup/xen-3.1-testing.hg/linux-2.6-xen-sparse/arch/i386/kernel/vm86.c?q=do_vm86_irq_handling#l175
257:
258: static void do_sys_vm86(struct kernel_vm86_struct *info, struct
task_struct *tsk)
259: {
260: #ifndef CONFIG_X86_NO_TSS
261: struct tss_struct *tss;
262: #endif
263: long eax;
264: /*
265: * make sure the vm86() system call doesn't try to do anything silly
266: */
267: info->regs.__null_ds = 0;
268: info->regs.__null_es = 0;
269:
270: /* we are clearing fs,gs later just before "jmp resume_userspace",
271: * because starting with Linux 2.1.x they aren't no longer
saved/restored
272: */
273:
274: /*
275: * The eflags register is also special: we cannot trust that the
user
276: * has set it up safely, so this makes sure interrupt etc flags are
277: * inherited from protected mode.
278: */
279: VEFLAGS = info->regs.eflags;
280: info->regs.eflags &= SAFE_MASK;
281: info->regs.eflags |= info->regs32->eflags & ~SAFE_MASK;
282: info->regs.eflags |= VM_MASK;
283:
284: switch (info->cpu_type) {
285: case CPU_286:
286: tsk->thread.v86mask = 0;
287: break;
288: case CPU_386:
289: tsk->thread.v86mask = NT_MASK | IOPL_MASK;
290: break;
291: case CPU_486:
292: tsk->thread.v86mask = AC_MASK | NT_MASK |
IOPL_MASK;
293: break;
294: default:
295: tsk->thread.v86mask = ID_MASK | AC_MASK |
NT_MASK | IOPL_MASK;
296: break;
297: }
298:
299: /*
300: * Save old state, set default return value (%eax) to 0
301: */
302: info->regs32->eax = 0;
303: tsk->thread.saved_esp0 = tsk->thread.esp0;
304: savesegment(fs, tsk->thread.saved_fs);
305: savesegment(gs, tsk->thread.saved_gs);
306:
307: #ifndef CONFIG_X86_NO_TSS
308: tss = &per_cpu(init_tss, get_cpu());
309: #endif
310: tsk->thread.esp0 = (unsigned long) &info->VM86_TSS_ESP0;
311: if (cpu_has_sep)
312: tsk->thread.sysenter_cs = 0;
313: load_esp0(tss, &tsk->thread);
314: #ifndef CONFIG_X86_NO_TSS
315: put_cpu();
316: #endif
317:
318: tsk->thread.screen_bitmap = info->screen_bitmap;
319: if (info->flags & VM86_SCREEN_BITMAP)
320: mark_screen_rdonly(tsk->mm);
321: __asm__ __volatile__("xorl %eax,%eax; movl %eax,%fs; movl
%eax,%gs\n\t");
322: __asm__ __volatile__("movl %%eax, %0\n" :"=r"(eax));
323:
324: /*call audit_syscall_exit since we do not exit via the
normal paths */
325: if (unlikely(current->audit_context))
326: audit_syscall_exit(AUDITSC_RESULT(eax), eax);
327:
328: __asm__ __volatile__(
329: "movl %0,%%esp\n\t"
330: "movl %1,%%ebp\n\t"
331: "jmp resume_userspace"
332: : /* no outputs */
333: :"r" (&info->regs), "r" (task_thread_info(tsk)));
334: /* we never return here */
335: }
336:
