299 lines
9.8 KiB
C
299 lines
9.8 KiB
C
/*
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* Copyright (C) 2015, Intel Corporation. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* 3. Neither the name of the copyright holder nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "prot-domains.h"
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#include "tss.h"
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#include "helpers.h"
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#include "stacks.h"
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#include "idt.h"
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#include "syscalls.h"
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#include "gdt.h"
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#include "gdt-layout.h"
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#include "interrupt.h"
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/**
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* Current protection domain. Not protected, since it is just a convenience
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* variable to avoid unneeded protection domain switches.
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*/
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dom_id_t cur_dom = DOM_ID_app;
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/* defined in syscalls-int-asm.S */
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void prot_domains_sysret_dispatcher(void);
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/* Maximum depth of inter-domain call stack */
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#define MAX_INTER_DOM_CALL_STK_SZ 4
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/* Protected call stack for inter-domain system calls. The stack grows up. */
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static volatile dom_id_t ATTR_BSS_KERN
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inter_dom_call_stk[MAX_INTER_DOM_CALL_STK_SZ];
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/* Pointer to the next (free) slot in the inter-domain call stack */
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static int ATTR_BSS_KERN inter_dom_call_stk_ptr;
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/*---------------------------------------------------------------------------*/
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static inline void __attribute__((always_inline))
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update_eflags(dom_id_t from_id, dom_id_t to_id, interrupt_stack_t *intr_stk)
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{
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if((to_id == DOM_ID_app) &&
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(DT_SEL_GET_RPL(intr_stk->cs) == PRIV_LVL_USER)) {
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/* Only enable interrupts in the application protection domain cooperative
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* scheduling context.
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*/
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intr_stk->eflags |= EFLAGS_IF;
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} else {
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intr_stk->eflags &= ~EFLAGS_IF;
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}
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}
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/*---------------------------------------------------------------------------*/
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static inline void __attribute__((always_inline))
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dispatcher_tail(dom_id_t from_id, dom_id_t to_id, interrupt_stack_t *intr_stk)
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{
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cur_dom = to_id;
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prot_domains_switch(from_id, to_id, intr_stk);
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prot_domains_set_wp(true);
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update_eflags(from_id, to_id, intr_stk);
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}
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/*---------------------------------------------------------------------------*/
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int main(void);
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static inline void __attribute__((always_inline))
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syscall_dispatcher_tail(interrupt_stack_t *intr_stk,
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dom_id_t to_id,
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uint32_t syscall_eip)
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{
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dom_id_t from_id;
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volatile dom_kern_data_t *from_dkd, *to_dkd;
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to_dkd = prot_domains_kern_data + to_id;
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/* This implementation of protection domains is non-reentrant. For example,
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* it stores the return address taken from the stack of a caller domain
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* while dispatching a system call and stores it in a single field in the
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* kernel data associated with that protection domain. That model does not
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* permit reentrancy.
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*/
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if((to_dkd->flags & PROT_DOMAINS_FLAG_BUSY) == PROT_DOMAINS_FLAG_BUSY) {
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halt();
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}
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to_dkd->flags |= PROT_DOMAINS_FLAG_BUSY;
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/* Update the interrupt stack so that the IRET instruction will return to the
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* system call entrypoint.
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*/
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intr_stk->eip = syscall_eip;
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/* Lookup the information for the caller */
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from_id = inter_dom_call_stk[inter_dom_call_stk_ptr - 1];
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from_dkd = prot_domains_kern_data + from_id;
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/* Save the current return address from the unprivileged stack to a protected
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* location in the kernel-owned data structure. This enforces return
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* entrypoint control.
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*/
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from_dkd->orig_ret_addr = *(uintptr_t *)intr_stk->esp;
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/* Update the unprivileged stack so that when the system call body is
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* complete, it will invoke the system call return stub.
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*/
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*((uintptr_t *)intr_stk->esp) = (uintptr_t)prot_domains_sysret_stub;
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if(MAX_INTER_DOM_CALL_STK_SZ <= inter_dom_call_stk_ptr) {
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halt();
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}
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inter_dom_call_stk[inter_dom_call_stk_ptr] = to_id;
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inter_dom_call_stk_ptr++;
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dispatcher_tail(from_id, to_id, intr_stk);
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}
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/*---------------------------------------------------------------------------*/
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void __attribute__((fastcall))
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prot_domains_syscall_dispatcher_impl(interrupt_stack_t *intr_stk,
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dom_id_t to_id,
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syscalls_entrypoint_t *syscall)
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{
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uint32_t syscall_eip;
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if(PROT_DOMAINS_ACTUAL_CNT <= to_id) {
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halt();
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}
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/* Get the approved entrypoint for the system call being invoked */
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if(!((((uintptr_t)syscalls_entrypoints) <= (uintptr_t)syscall) &&
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(((uintptr_t)syscall) < (uintptr_t)syscalls_entrypoints_end) &&
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(((((uintptr_t)syscall) - (uintptr_t)syscalls_entrypoints)
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% sizeof(syscalls_entrypoint_t)) == 0))) {
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/* Assert is not usable when switching protection domains */
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halt();
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}
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if((BIT(to_id) & syscall->doms) == 0) {
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halt();
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}
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syscall_eip = syscall->entrypoint;
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prot_domains_set_wp(false);
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syscall_dispatcher_tail(intr_stk, to_id, syscall_eip);
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}
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/*---------------------------------------------------------------------------*/
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int main(void);
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void __attribute__((fastcall))
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prot_domains_launch_kernel_impl(interrupt_stack_t *intr_stk)
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{
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inter_dom_call_stk[0] = DOM_ID_app;
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inter_dom_call_stk_ptr = 1;
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syscall_dispatcher_tail(intr_stk, DOM_ID_kern, (uint32_t)main);
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}
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/*---------------------------------------------------------------------------*/
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void __attribute__((fastcall))
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prot_domains_sysret_dispatcher_impl(interrupt_stack_t *intr_stk)
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{
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dom_id_t from_id, to_id;
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if(inter_dom_call_stk_ptr <= 1) {
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halt();
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}
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from_id = inter_dom_call_stk[inter_dom_call_stk_ptr - 1];
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to_id = inter_dom_call_stk[inter_dom_call_stk_ptr - 2];
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intr_stk->eip = prot_domains_kern_data[to_id].orig_ret_addr;
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prot_domains_set_wp(false);
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prot_domains_kern_data[from_id].flags &= ~PROT_DOMAINS_FLAG_BUSY;
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inter_dom_call_stk_ptr--;
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dispatcher_tail(from_id, to_id, intr_stk);
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Lookup the current protection domain.
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* \return Kernel data structure for the current protection domain.
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*/
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static volatile dom_kern_data_t *
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get_current_domain(void)
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{
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dom_id_t id;
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id = inter_dom_call_stk[inter_dom_call_stk_ptr - 1];
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return prot_domains_kern_data + id;
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Check whether the protection domain is authorized to perform port
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* I/O from the cooperative scheduling context.
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* \param dkd Protection domain to check
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* \return Result of the check as a Boolean value
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*/
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static bool
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needs_port_io(volatile dom_kern_data_t *dkd)
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{
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return (dkd->flags & PROT_DOMAINS_FLAG_PIO) == PROT_DOMAINS_FLAG_PIO;
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}
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/*---------------------------------------------------------------------------*/
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/* Mark the context parameter as volatile so that writes to it will not get
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* optimized out. This parameter is not handled like ordinary function
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* parameters. It actually partially includes the contents of the exception
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* stack, so updates to those locations can affect the operation of the
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* subsequent interrupt return.
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*/
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static void
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gp_fault_handler(volatile struct interrupt_context context)
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{
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uint32_t cs_lim;
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uint8_t opcode;
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volatile dom_kern_data_t *dkd = get_current_domain();
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if (needs_port_io(dkd)) {
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__asm__ __volatile__ (
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"mov %%cs, %0\n\t"
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"lsl %0, %0\n\t"
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: "=r"(cs_lim));
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if (cs_lim < context.eip) {
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halt();
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}
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/* Load first byte of faulting instruction */
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__asm__ __volatile__ (
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"movb %%cs:%1, %0"
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: "=q"(opcode)
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: "m"(*(uint8_t *)context.eip));
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switch (opcode) {
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case 0xEC: /* inb */
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context.eax = (context.eax & ~0xFF) | inb((uint16_t)context.edx);
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break;
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case 0xED: /* inl */
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context.eax = inl((uint16_t)context.edx);
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break;
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case 0xEE: /* outb */
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outb((uint16_t)context.edx, (uint8_t)context.eax);
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break;
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case 0xEF: /* outl */
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outl((uint16_t)context.edx, context.eax);
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break;
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default:
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halt();
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}
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/* Skip the faulting port I/O instruction that was emulated. */
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context.eip++;
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} else {
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halt();
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}
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}
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/*---------------------------------------------------------------------------*/
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void
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syscalls_int_init(void)
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{
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tss_init();
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SET_EXCEPTION_HANDLER(13, 1, gp_fault_handler);
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/* Register system call dispatchers: */
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idt_set_intr_gate_desc(PROT_DOMAINS_SYSCALL_DISPATCH_INT,
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(uint32_t)prot_domains_syscall_dispatcher,
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GDT_SEL_CODE_EXC,
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PRIV_LVL_USER);
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idt_set_intr_gate_desc(PROT_DOMAINS_SYSRET_DISPATCH_INT,
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(uint32_t)prot_domains_sysret_dispatcher,
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GDT_SEL_CODE_EXC,
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PRIV_LVL_USER);
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}
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/*---------------------------------------------------------------------------*/
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