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This patch extends the protection domain framework with an additional plugin to use Task-State Segment (TSS) structures to offload much of the work of switching protection domains to the CPU. This can save space compared to paging, since paging requires two 4KiB page tables and one 32-byte page table plus one whole-system TSS and an additional 32-byte data structure for each protection domain, whereas the approach implemented by this patch just requires a 128-byte data structure for each protection domain. Only a small number of protection domains will typically be used, so n * 128 < 8328 + (n * 32). For additional information, please refer to cpu/x86/mm/README.md. GCC 6 is introducing named address spaces for the FS and GS segments [1]. LLVM Clang also provides address spaces for the FS and GS segments [2]. This patch also adds support to the multi-segment X86 memory management subsystem for using these features instead of inline assembly blocks, which enables type checking to detect some address space mismatches. [1] https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html [2] http://llvm.org/releases/3.3/tools/clang/docs/LanguageExtensions.html#target-specific-extensions
125 lines
4.4 KiB
C
125 lines
4.4 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 "cpu.h"
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#include "gdt.h"
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#include "helpers.h"
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#include "idt.h"
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#include "interrupt.h"
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#include "irq.h"
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#include "stacks.h"
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static void
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double_fault_handler(struct interrupt_context context)
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{
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halt();
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}
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/*---------------------------------------------------------------------------*/
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/* The OS has switched to its own segment descriptors. When multi-segment
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* protection domain support is enabled, this routine runs with the
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* necessary address translations configured to invoke other routines that
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* require those translations to be in place. However, the protection domain
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* support, if enabled, has not yet been fully activated.
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*/
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static void
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boot_stage1(void)
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{
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idt_init();
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/* Set an interrupt handler for Double Fault exception. This way, we avoid
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* the system to triple fault, leaving no trace about what happened.
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*/
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SET_EXCEPTION_HANDLER(8, 1, double_fault_handler);
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/* Initialize protection domain support, if enabled */
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prot_domains_init();
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prot_domains_leave_boot_stage1();
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}
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/*---------------------------------------------------------------------------*/
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int main(void);
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/* This routine runs with the initial, flat address space, even if protection
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* domain support is enabled. The goal behind the design of this routine is to
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* keep it as short as possible, since it is unable to directly reference data
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* and invoke functions that are intended to be accessible later after the
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* system has booted when a multi-segment protection domain model is in use.
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*/
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void
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cpu_boot_stage0(void)
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{
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/* Reserve three stack slots for return addresses */
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uintptr_t top_of_stack = STACKS_INIT_TOP;
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#if X86_CONF_PROT_DOMAINS != X86_CONF_PROT_DOMAINS__NONE
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uintptr_t *top_of_stack_ptr =
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(uintptr_t *)DATA_OFF_TO_PHYS_ADDR(top_of_stack);
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top_of_stack_ptr[0] = (uintptr_t)prot_domains_launch_kernel;
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top_of_stack_ptr[1] = (uintptr_t)prot_domains_launch_app;
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#endif
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/* Perform common GDT initialization */
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gdt_init();
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/* Switch all data segment registers to the newly-initialized flat data
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* descriptor.
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*/
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__asm__(
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"mov %0, %%ds\n\t"
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"mov %0, %%es\n\t"
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"mov %0, %%fs\n\t"
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"mov %0, %%gs\n\t"
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:
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: "r" (GDT_SEL_DATA_FLAT)
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);
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/**
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* Perform specific GDT initialization tasks for the protection domain
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* implementation that is enabled, if any.
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*/
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prot_domains_gdt_init();
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/* Do not pass memory operands to the asm block below, since it is
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* switching from the flat address space to a multi-segment address space
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* model if such a model is used by the enabled protection domain
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* implementation, if any.
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*/
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__asm__(
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"mov %[_ss_], %%ss\n\t"
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"mov %[_esp_], %%esp\n\t"
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"ljmp %[_cs_], %[_stage1_]\n\t"
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:
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: [_ss_] "r" (GDT_SEL_STK_EXC),
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[_esp_] "r" (top_of_stack),
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[_cs_] "i" ((uint16_t)GDT_SEL_CODE_EXC),
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[_stage1_] "i" (boot_stage1)
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);
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}
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