/* * linux/kernel/vm86.c * * Copyright (C) 1994 Linus Torvalds */ #include #include #include #include #include #include #include #include #include #include #include #include /* * Known problems: * * Interrupt handling is not guaranteed: * - a real x86 will disable all interrupts for one instruction * after a "mov ss,xx" to make stack handling atomic even without * the 'lss' instruction. We can't guarantee this in v86 mode, * as the next instruction might result in a page fault or similar. * - a real x86 will have interrupts disabled for one instruction * past the 'sti' that enables them. We don't bother with all the * details yet.. * * Hopefully these problems do not actually matter for anything. */ #define KVM86 ((struct kernel_vm86_struct *)regs) #define VMPI KVM86->vm86plus /* * 8- and 16-bit register defines.. */ #define AL(regs) (((unsigned char *)&((regs)->eax))[0]) #define AH(regs) (((unsigned char *)&((regs)->eax))[1]) #define IP(regs) (*(unsigned short *)&((regs)->eip)) #define SP(regs) (*(unsigned short *)&((regs)->esp)) /* * virtual flags (16 and 32-bit versions) */ #define VFLAGS (*(unsigned short *)&(current->tss.v86flags)) #define VEFLAGS (current->tss.v86flags) #define set_flags(X,new,mask) \ ((X) = ((X) & ~(mask)) | ((new) & (mask))) #define SAFE_MASK (0xDD5) #define RETURN_MASK (0xDFF) #define VM86_REGS_PART2 orig_eax #define VM86_REGS_SIZE1 \ ( (unsigned)( & (((struct kernel_vm86_regs *)0)->VM86_REGS_PART2) ) ) #define VM86_REGS_SIZE2 (sizeof(struct kernel_vm86_regs) - VM86_REGS_SIZE1) asmlinkage struct pt_regs * save_v86_state(struct kernel_vm86_regs * regs) { struct pt_regs *ret; unsigned long tmp; lock_kernel(); if (!current->tss.vm86_info) { printk("no vm86_info: BAD\n"); do_exit(SIGSEGV); } set_flags(regs->eflags, VEFLAGS, VIF_MASK | current->tss.v86mask); tmp = copy_to_user(¤t->tss.vm86_info->regs,regs, VM86_REGS_SIZE1); tmp += copy_to_user(¤t->tss.vm86_info->regs.VM86_REGS_PART2, ®s->VM86_REGS_PART2, VM86_REGS_SIZE2); tmp += put_user(current->tss.screen_bitmap,¤t->tss.vm86_info->screen_bitmap); if (tmp) { printk("vm86: could not access userspace vm86_info\n"); do_exit(SIGSEGV); } current->tss.esp0 = current->saved_kernel_stack; current->saved_kernel_stack = 0; ret = KVM86->regs32; unlock_kernel(); return ret; } static void mark_screen_rdonly(struct task_struct * tsk) { pgd_t *pgd; pmd_t *pmd; pte_t *pte; int i; pgd = pgd_offset(tsk->mm, 0xA0000); if (pgd_none(*pgd)) return; if (pgd_bad(*pgd)) { printk("vm86: bad pgd entry [%p]:%08lx\n", pgd, pgd_val(*pgd)); pgd_clear(pgd); return; } pmd = pmd_offset(pgd, 0xA0000); if (pmd_none(*pmd)) return; if (pmd_bad(*pmd)) { printk("vm86: bad pmd entry [%p]:%08lx\n", pmd, pmd_val(*pmd)); pmd_clear(pmd); return; } pte = pte_offset(pmd, 0xA0000); for (i = 0; i < 32; i++) { if (pte_present(*pte)) set_pte(pte, pte_wrprotect(*pte)); pte++; } flush_tlb(); } static do_vm86_irq_handling(int subfunction, int irqnumber); static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk); asmlinkage int sys_vm86old(struct vm86_struct * v86) { struct kernel_vm86_struct info; /* declare this _on top_, * this avoids wasting of stack space. * This remains on the stack until we * return to 32 bit user space. */ struct task_struct *tsk; int tmp, ret = -EPERM; lock_kernel(); tsk = current; if (tsk->saved_kernel_stack) goto out; tmp = copy_from_user(&info, v86, VM86_REGS_SIZE1); tmp += copy_from_user(&info.regs.VM86_REGS_PART2, &v86->regs.VM86_REGS_PART2, (long)&info.vm86plus - (long)&info.regs.VM86_REGS_PART2); ret = -EFAULT; if (tmp) goto out; memset(&info.vm86plus, 0, (int)&info.regs32 - (int)&info.vm86plus); info.regs32 = (struct pt_regs *) &v86; tsk->tss.vm86_info = v86; do_sys_vm86(&info, tsk); ret = 0; /* we never return here */ out: unlock_kernel(); return ret; } asmlinkage int sys_vm86(unsigned long subfunction, struct vm86plus_struct * v86) { struct kernel_vm86_struct info; /* declare this _on top_, * this avoids wasting of stack space. * This remains on the stack until we * return to 32 bit user space. */ struct task_struct *tsk; int tmp, ret; lock_kernel(); tsk = current; switch (subfunction) { case VM86_REQUEST_IRQ: case VM86_FREE_IRQ: case VM86_GET_IRQ_BITS: case VM86_GET_AND_RESET_IRQ: ret = do_vm86_irq_handling(subfunction,(int)v86); goto out; case VM86_PLUS_INSTALL_CHECK: /* NOTE: on old vm86 stuff this will return the error from verify_area(), because the subfunction is interpreted as (invalid) address to vm86_struct. So the installation check works. */ ret = 0; goto out; } /* we come here only for functions VM86_ENTER, VM86_ENTER_NO_BYPASS */ ret = -EPERM; if (tsk->saved_kernel_stack) goto out; tmp = copy_from_user(&info, v86, VM86_REGS_SIZE1); tmp += copy_from_user(&info.regs.VM86_REGS_PART2, &v86->regs.VM86_REGS_PART2, (long)&info.regs32 - (long)&info.regs.VM86_REGS_PART2); ret = -EFAULT; if (tmp) goto out; info.regs32 = (struct pt_regs *) &subfunction; info.vm86plus.is_vm86pus = 1; tsk->tss.vm86_info = (struct vm86_struct *)v86; do_sys_vm86(&info, tsk); ret = 0; /* we never return here */ out: unlock_kernel(); return ret; } static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk) { /* * make sure the vm86() system call doesn't try to do anything silly */ info->regs.__null_ds = 0; info->regs.__null_es = 0; /* we are clearing fs,gs later just before "jmp ret_from_sys_call", * because starting with Linux 2.1.x they aren't no longer saved/restored */ /* * The eflags register is also special: we cannot trust that the user * has set it up safely, so this makes sure interrupt etc flags are * inherited from protected mode. */ VEFLAGS = info->regs.eflags; info->regs.eflags &= SAFE_MASK; info->regs.eflags |= info->regs32->eflags & ~SAFE_MASK; info->regs.eflags |= VM_MASK; switch (info->cpu_type) { case CPU_286: tsk->tss.v86mask = 0; break; case CPU_386: tsk->tss.v86mask = NT_MASK | IOPL_MASK; break; case CPU_486: tsk->tss.v86mask = AC_MASK | NT_MASK | IOPL_MASK; break; default: tsk->tss.v86mask = ID_MASK | AC_MASK | NT_MASK | IOPL_MASK; break; } /* * Save old state, set default return value (%eax) to 0 */ info->regs32->eax = 0; tsk->saved_kernel_stack = tsk->tss.esp0; tsk->tss.esp0 = (unsigned long) &info->VM86_TSS_ESP0; tsk->tss.screen_bitmap = info->screen_bitmap; if (info->flags & VM86_SCREEN_BITMAP) mark_screen_rdonly(tsk); unlock_kernel(); __asm__ __volatile__( "xorl %%eax,%%eax; mov %%ax,%%fs; mov %%ax,%%gs\n\t" "movl %0,%%esp\n\t" "jmp ret_from_sys_call" : /* no outputs */ :"r" (&info->regs), "b" (tsk) : "ax"); /* we never return here */ } static inline void return_to_32bit(struct kernel_vm86_regs * regs16, int retval) { struct pt_regs * regs32; regs32 = save_v86_state(regs16); regs32->eax = retval; unlock_kernel(); __asm__ __volatile__("movl %0,%%esp\n\t" "jmp ret_from_sys_call" : : "r" (regs32), "b" (current)); } static inline void set_IF(struct kernel_vm86_regs * regs) { VEFLAGS |= VIF_MASK; if (VEFLAGS & VIP_MASK) return_to_32bit(regs, VM86_STI); } static inline void clear_IF(struct kernel_vm86_regs * regs) { VEFLAGS &= ~VIF_MASK; } static inline void clear_TF(struct kernel_vm86_regs * regs) { regs->eflags &= ~TF_MASK; } static inline void set_vflags_long(unsigned long eflags, struct kernel_vm86_regs * regs) { set_flags(VEFLAGS, eflags, current->tss.v86mask); set_flags(regs->eflags, eflags, SAFE_MASK); if (eflags & IF_MASK) set_IF(regs); } static inline void set_vflags_short(unsigned short flags, struct kernel_vm86_regs * regs) { set_flags(VFLAGS, flags, current->tss.v86mask); set_flags(regs->eflags, flags, SAFE_MASK); if (flags & IF_MASK) set_IF(regs); } static inline unsigned long get_vflags(struct kernel_vm86_regs * regs) { unsigned long flags = regs->eflags & RETURN_MASK; if (VEFLAGS & VIF_MASK) flags |= IF_MASK; return flags | (VEFLAGS & current->tss.v86mask); } static inline int is_revectored(int nr, struct revectored_struct * bitmap) { __asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0" :"=r" (nr) :"m" (*bitmap),"r" (nr)); return nr; } /* * Boy are these ugly, but we need to do the correct 16-bit arithmetic. * Gcc makes a mess of it, so we do it inline and use non-obvious calling * conventions.. */ #define pushb(base, ptr, val) \ __asm__ __volatile__( \ "decw %w0\n\t" \ "movb %2,0(%1,%0)" \ : "=r" (ptr) \ : "r" (base), "q" (val), "0" (ptr)) #define pushw(base, ptr, val) \ __asm__ __volatile__( \ "decw %w0\n\t" \ "movb %h2,0(%1,%0)\n\t" \ "decw %w0\n\t" \ "movb %b2,0(%1,%0)" \ : "=r" (ptr) \ : "r" (base), "q" (val), "0" (ptr)) #define pushl(base, ptr, val) \ __asm__ __volatile__( \ "decw %w0\n\t" \ "rorl $16,%2\n\t" \ "movb %h2,0(%1,%0)\n\t" \ "decw %w0\n\t" \ "movb %b2,0(%1,%0)\n\t" \ "decw %w0\n\t" \ "rorl $16,%2\n\t" \ "movb %h2,0(%1,%0)\n\t" \ "decw %w0\n\t" \ "movb %b2,0(%1,%0)" \ : "=r" (ptr) \ : "r" (base), "q" (val), "0" (ptr)) #define popb(base, ptr) \ ({ unsigned long __res; \ __asm__ __volatile__( \ "movb 0(%1,%0),%b2\n\t" \ "incw %w0" \ : "=r" (ptr), "=r" (base), "=q" (__res) \ : "0" (ptr), "1" (base), "2" (0)); \ __res; }) #define popw(base, ptr) \ ({ unsigned long __res; \ __asm__ __volatile__( \ "movb 0(%1,%0),%b2\n\t" \ "incw %w0\n\t" \ "movb 0(%1,%0),%h2\n\t" \ "incw %w0" \ : "=r" (ptr), "=r" (base), "=q" (__res) \ : "0" (ptr), "1" (base), "2" (0)); \ __res; }) #define popl(base, ptr) \ ({ unsigned long __res; \ __asm__ __volatile__( \ "movb 0(%1,%0),%b2\n\t" \ "incw %w0\n\t" \ "movb 0(%1,%0),%h2\n\t" \ "incw %w0\n\t" \ "rorl $16,%2\n\t" \ "movb 0(%1,%0),%b2\n\t" \ "incw %w0\n\t" \ "movb 0(%1,%0),%h2\n\t" \ "incw %w0\n\t" \ "rorl $16,%2" \ : "=r" (ptr), "=r" (base), "=q" (__res) \ : "0" (ptr), "1" (base)); \ __res; }) static void do_int(struct kernel_vm86_regs *regs, int i, unsigned char * ssp, unsigned long sp) { unsigned long *intr_ptr, segoffs; if (regs->cs == BIOSSEG) goto cannot_handle; if (is_revectored(i, &KVM86->int_revectored)) goto cannot_handle; if (i==0x21 && is_revectored(AH(regs),&KVM86->int21_revectored)) goto cannot_handle; intr_ptr = (unsigned long *) (i << 2); if (get_user(segoffs, intr_ptr)) goto cannot_handle; if ((segoffs >> 16) == BIOSSEG) goto cannot_handle; pushw(ssp, sp, get_vflags(regs)); pushw(ssp, sp, regs->cs); pushw(ssp, sp, IP(regs)); regs->cs = segoffs >> 16; SP(regs) -= 6; IP(regs) = segoffs & 0xffff; clear_TF(regs); clear_IF(regs); return; cannot_handle: return_to_32bit(regs, VM86_INTx + (i << 8)); } /* This must be called with the kernel lock held. */ int handle_vm86_trap(struct kernel_vm86_regs * regs, long error_code, int trapno) { if (VMPI.is_vm86pus) { if ( (trapno==3) || (trapno==1) ) return_to_32bit(regs, VM86_TRAP + (trapno << 8)); do_int(regs, trapno, (unsigned char *) (regs->ss << 4), SP(regs)); return 0; } if (trapno !=1) return 1; /* we let this handle by the calling routine */ if (current->flags & PF_PTRACED) current->blocked &= ~(1 << (SIGTRAP-1)); send_sig(SIGTRAP, current, 1); current->tss.trap_no = trapno; current->tss.error_code = error_code; return 0; } /* This must be called with the kernel lock held. */ void handle_vm86_fault(struct kernel_vm86_regs * regs, long error_code) { unsigned char *csp, *ssp; unsigned long ip, sp; #define CHECK_IF_IN_TRAP \ if (VMPI.vm86dbg_active && VMPI.vm86dbg_TFpendig) \ pushw(ssp,sp,popw(ssp,sp) | TF_MASK); #define VM86_FAULT_RETURN \ if (VMPI.force_return_for_pic && (VEFLAGS & IF_MASK)) \ return_to_32bit(regs, VM86_PICRETURN); \ return; csp = (unsigned char *) (regs->cs << 4); ssp = (unsigned char *) (regs->ss << 4); sp = SP(regs); ip = IP(regs); switch (popb(csp, ip)) { /* operand size override */ case 0x66: switch (popb(csp, ip)) { /* pushfd */ case 0x9c: SP(regs) -= 4; IP(regs) += 2; pushl(ssp, sp, get_vflags(regs)); VM86_FAULT_RETURN; /* popfd */ case 0x9d: SP(regs) += 4; IP(regs) += 2; CHECK_IF_IN_TRAP set_vflags_long(popl(ssp, sp), regs); VM86_FAULT_RETURN; /* iretd */ case 0xcf: SP(regs) += 12; IP(regs) = (unsigned short)popl(ssp, sp); regs->cs = (unsigned short)popl(ssp, sp); CHECK_IF_IN_TRAP set_vflags_long(popl(ssp, sp), regs); VM86_FAULT_RETURN; /* need this to avoid a fallthrough */ default: return_to_32bit(regs, VM86_UNKNOWN); } /* pushf */ case 0x9c: SP(regs) -= 2; IP(regs)++; pushw(ssp, sp, get_vflags(regs)); VM86_FAULT_RETURN; /* popf */ case 0x9d: SP(regs) += 2; IP(regs)++; CHECK_IF_IN_TRAP set_vflags_short(popw(ssp, sp), regs); VM86_FAULT_RETURN; /* int xx */ case 0xcd: { int intno=popb(csp, ip); IP(regs) += 2; if (VMPI.vm86dbg_active) { if ( (1 << (intno &7)) & VMPI.vm86dbg_intxxtab[intno >> 3] ) return_to_32bit(regs, VM86_INTx + (intno << 8)); } do_int(regs, intno, ssp, sp); return; } /* iret */ case 0xcf: SP(regs) += 6; IP(regs) = popw(ssp, sp); regs->cs = popw(ssp, sp); CHECK_IF_IN_TRAP set_vflags_short(popw(ssp, sp), regs); VM86_FAULT_RETURN; /* cli */ case 0xfa: IP(regs)++; clear_IF(regs); VM86_FAULT_RETURN; /* sti */ /* * Damn. This is incorrect: the 'sti' instruction should actually * enable interrupts after the /next/ instruction. Not good. * * Probably needs some horsing around with the TF flag. Aiee.. */ case 0xfb: IP(regs)++; set_IF(regs); VM86_FAULT_RETURN; default: return_to_32bit(regs, VM86_UNKNOWN); } } /* ---------------- vm86 special IRQ passing stuff ----------------- */ #define VM86_IRQNAME "vm86irq" static struct vm86_irqs { struct task_struct *tsk; int sig; } vm86_irqs[16] = {{0},}; static int irqbits=0; #define ALLOWED_SIGS ( 1 /* 0 = don't send a signal */ \ | (1 << SIGUSR1) | (1 << SIGUSR2) | (1 << SIGIO) | (1 << SIGURG) \ | (1 << SIGUNUSED) ) static void irq_handler(int intno, void *dev_id, struct pt_regs * regs) { int irq_bit; unsigned long flags; lock_kernel(); save_flags(flags); cli(); irq_bit = 1 << intno; if ((irqbits & irq_bit) || ! vm86_irqs[intno].tsk) goto out; irqbits |= irq_bit; if (vm86_irqs[intno].sig) send_sig(vm86_irqs[intno].sig, vm86_irqs[intno].tsk, 1); /* else user will poll for IRQs */ out: restore_flags(flags); unlock_kernel(); } static inline void free_vm86_irq(int irqnumber) { free_irq(irqnumber,0); vm86_irqs[irqnumber].tsk = 0; irqbits &= ~(1 << irqnumber); } static inline int task_valid(struct task_struct *tsk) { struct task_struct *p; for_each_task(p) { if ((p == tsk) && (p->sig)) return 1; } return 0; } static inline void handle_irq_zombies(void) { int i; for (i=3; i<16; i++) { if (vm86_irqs[i].tsk) { if (task_valid(vm86_irqs[i].tsk)) continue; free_vm86_irq(i); } } } static inline int get_and_reset_irq(int irqnumber) { int bit; unsigned long flags; if ( (irqnumber<3) || (irqnumber>15) ) return 0; if (vm86_irqs[irqnumber].tsk != current) return 0; save_flags(flags); cli(); bit = irqbits & (1 << irqnumber); irqbits &= ~bit; restore_flags(flags); return bit; } static int do_vm86_irq_handling(int subfunction, int irqnumber) { int ret; switch (subfunction) { case VM86_GET_AND_RESET_IRQ: { return get_and_reset_irq(irqnumber); } case VM86_GET_IRQ_BITS: { return irqbits; } case VM86_REQUEST_IRQ: { int sig = irqnumber >> 8; int irq = irqnumber & 255; handle_irq_zombies(); if (!suser()) return -EPERM; if (!((1 << sig) & ALLOWED_SIGS)) return -EPERM; if ( (irq<3) || (irq>15) ) return -EPERM; if (vm86_irqs[irq].tsk) return -EPERM; ret = request_irq(irq, &irq_handler, 0, VM86_IRQNAME, 0); if (ret) return ret; vm86_irqs[irq].sig = sig; vm86_irqs[irq].tsk = current; return irq; } case VM86_FREE_IRQ: { handle_irq_zombies(); if ( (irqnumber<3) || (irqnumber>15) ) return -EPERM; if (!vm86_irqs[irqnumber].tsk) return 0; if (vm86_irqs[irqnumber].tsk != current) return -EPERM; free_vm86_irq(irqnumber); return 0; } } return -EINVAL; }