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of the kernel address space already. Intel recommend this anyway, because using a non-4GB limit adds an additional clock cycle to address generation. We were able to install 4GB segments into the LDT, so any limits we imposed on %cs and %ds were academic anyway. More importantly, this allows us to make a page in the kernel readable to user applications, for holding things like the signal trampoline and other fun things. Move the user %cs/%ds segments from the LDT to the GDT. There was no good reason for them to be there anyway. The old LDT entries are still there but we can now relax the restriction that prevented users from emptying the default LDT entries. Putting user and kernel %cs and %ds together allows us to access the fast sysenter/sysexit/syscall/sysret instructions. syscall/sysret in particular require that the user/kernel segments be laid out this way. Reserve a slot specifically for NDIS while here. Create two user controllable slots in the GDT that are context switched with the (kernel) thread. This allows user applications to set two user privilige selectors to arbitary values. Create i386_set_fsbase(void *base) and friends. (get/set, fs/gs). For i386, %gs is used by tls and the thread libraries and this means that user processes no longer have to have the cost of having a custom LDT, and we will no longer to do a ldt switch when activating a kthread/ithread in the usual case any more. In other words, we can now set the base address for %fs and %gs to arbitary addresses without the pain of messing with ldt segments.
257 lines
10 KiB
C
257 lines
10 KiB
C
/*-
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* Copyright (c) 1989, 1990 William F. Jolitz
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* William Jolitz.
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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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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR 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, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)segments.h 7.1 (Berkeley) 5/9/91
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* $FreeBSD$
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*/
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#ifndef _MACHINE_SEGMENTS_H_
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#define _MACHINE_SEGMENTS_H_
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/*
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* 386 Segmentation Data Structures and definitions
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* William F. Jolitz (william@ernie.berkeley.edu) 6/20/1989
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*/
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/*
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* Selectors
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*/
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#define ISPL(s) ((s)&3) /* what is the priority level of a selector */
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#define SEL_KPL 0 /* kernel priority level */
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#define SEL_UPL 3 /* user priority level */
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#define ISLDT(s) ((s)&SEL_LDT) /* is it local or global */
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#define SEL_LDT 4 /* local descriptor table */
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#define IDXSEL(s) (((s)>>3) & 0x1fff) /* index of selector */
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#define LSEL(s,r) (((s)<<3) | SEL_LDT | r) /* a local selector */
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#define GSEL(s,r) (((s)<<3) | r) /* a global selector */
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/*
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* Memory and System segment descriptors
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*/
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struct segment_descriptor {
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unsigned sd_lolimit:16 ; /* segment extent (lsb) */
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unsigned sd_lobase:24 __packed; /* segment base address (lsb) */
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unsigned sd_type:5 ; /* segment type */
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unsigned sd_dpl:2 ; /* segment descriptor priority level */
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unsigned sd_p:1 ; /* segment descriptor present */
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unsigned sd_hilimit:4 ; /* segment extent (msb) */
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unsigned sd_xx:2 ; /* unused */
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unsigned sd_def32:1 ; /* default 32 vs 16 bit size */
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unsigned sd_gran:1 ; /* limit granularity (byte/page units)*/
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unsigned sd_hibase:8 ; /* segment base address (msb) */
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} ;
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/*
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* Gate descriptors (e.g. indirect descriptors)
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*/
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struct gate_descriptor {
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unsigned gd_looffset:16 ; /* gate offset (lsb) */
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unsigned gd_selector:16 ; /* gate segment selector */
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unsigned gd_stkcpy:5 ; /* number of stack wds to cpy */
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unsigned gd_xx:3 ; /* unused */
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unsigned gd_type:5 ; /* segment type */
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unsigned gd_dpl:2 ; /* segment descriptor priority level */
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unsigned gd_p:1 ; /* segment descriptor present */
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unsigned gd_hioffset:16 ; /* gate offset (msb) */
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} ;
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/*
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* Generic descriptor
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*/
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union descriptor {
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struct segment_descriptor sd;
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struct gate_descriptor gd;
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};
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/* system segments and gate types */
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#define SDT_SYSNULL 0 /* system null */
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#define SDT_SYS286TSS 1 /* system 286 TSS available */
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#define SDT_SYSLDT 2 /* system local descriptor table */
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#define SDT_SYS286BSY 3 /* system 286 TSS busy */
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#define SDT_SYS286CGT 4 /* system 286 call gate */
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#define SDT_SYSTASKGT 5 /* system task gate */
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#define SDT_SYS286IGT 6 /* system 286 interrupt gate */
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#define SDT_SYS286TGT 7 /* system 286 trap gate */
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#define SDT_SYSNULL2 8 /* system null again */
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#define SDT_SYS386TSS 9 /* system 386 TSS available */
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#define SDT_SYSNULL3 10 /* system null again */
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#define SDT_SYS386BSY 11 /* system 386 TSS busy */
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#define SDT_SYS386CGT 12 /* system 386 call gate */
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#define SDT_SYSNULL4 13 /* system null again */
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#define SDT_SYS386IGT 14 /* system 386 interrupt gate */
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#define SDT_SYS386TGT 15 /* system 386 trap gate */
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/* memory segment types */
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#define SDT_MEMRO 16 /* memory read only */
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#define SDT_MEMROA 17 /* memory read only accessed */
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#define SDT_MEMRW 18 /* memory read write */
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#define SDT_MEMRWA 19 /* memory read write accessed */
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#define SDT_MEMROD 20 /* memory read only expand dwn limit */
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#define SDT_MEMRODA 21 /* memory read only expand dwn limit accessed */
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#define SDT_MEMRWD 22 /* memory read write expand dwn limit */
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#define SDT_MEMRWDA 23 /* memory read write expand dwn limit accessed */
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#define SDT_MEME 24 /* memory execute only */
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#define SDT_MEMEA 25 /* memory execute only accessed */
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#define SDT_MEMER 26 /* memory execute read */
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#define SDT_MEMERA 27 /* memory execute read accessed */
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#define SDT_MEMEC 28 /* memory execute only conforming */
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#define SDT_MEMEAC 29 /* memory execute only accessed conforming */
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#define SDT_MEMERC 30 /* memory execute read conforming */
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#define SDT_MEMERAC 31 /* memory execute read accessed conforming */
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/*
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* Software definitions are in this convenient format,
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* which are translated into inconvenient segment descriptors
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* when needed to be used by the 386 hardware
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*/
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struct soft_segment_descriptor {
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unsigned ssd_base ; /* segment base address */
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unsigned ssd_limit ; /* segment extent */
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unsigned ssd_type:5 ; /* segment type */
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unsigned ssd_dpl:2 ; /* segment descriptor priority level */
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unsigned ssd_p:1 ; /* segment descriptor present */
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unsigned ssd_xx:4 ; /* unused */
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unsigned ssd_xx1:2 ; /* unused */
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unsigned ssd_def32:1 ; /* default 32 vs 16 bit size */
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unsigned ssd_gran:1 ; /* limit granularity (byte/page units)*/
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};
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/*
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* region descriptors, used to load gdt/idt tables before segments yet exist.
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*/
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struct region_descriptor {
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unsigned rd_limit:16; /* segment extent */
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unsigned rd_base:32 __packed; /* base address */
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};
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/*
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* Segment Protection Exception code bits
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*/
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#define SEGEX_EXT 0x01 /* recursive or externally induced */
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#define SEGEX_IDT 0x02 /* interrupt descriptor table */
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#define SEGEX_TI 0x04 /* local descriptor table */
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/* other bits are affected descriptor index */
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#define SEGEX_IDX(s) (((s)>>3)&0x1fff)
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/*
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* Size of IDT table
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*/
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#define NIDT 256 /* 32 reserved, 0x80 syscall, most are h/w */
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#define NRSVIDT 32 /* reserved entries for cpu exceptions */
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/*
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* Entries in the Interrupt Descriptor Table (IDT)
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*/
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#define IDT_DE 0 /* #DE: Divide Error */
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#define IDT_DB 1 /* #DB: Debug */
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#define IDT_NMI 2 /* Nonmaskable External Interrupt */
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#define IDT_BP 3 /* #BP: Breakpoint */
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#define IDT_OF 4 /* #OF: Overflow */
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#define IDT_BR 5 /* #BR: Bound Range Exceeded */
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#define IDT_UD 6 /* #UD: Undefined/Invalid Opcode */
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#define IDT_NM 7 /* #NM: No Math Coprocessor */
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#define IDT_DF 8 /* #DF: Double Fault */
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#define IDT_FPUGP 9 /* Coprocessor Segment Overrun */
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#define IDT_TS 10 /* #TS: Invalid TSS */
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#define IDT_NP 11 /* #NP: Segment Not Present */
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#define IDT_SS 12 /* #SS: Stack Segment Fault */
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#define IDT_GP 13 /* #GP: General Protection Fault */
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#define IDT_PF 14 /* #PF: Page Fault */
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#define IDT_MF 16 /* #MF: FPU Floating-Point Error */
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#define IDT_AC 17 /* #AC: Alignment Check */
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#define IDT_MC 18 /* #MC: Machine Check */
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#define IDT_XF 19 /* #XF: SIMD Floating-Point Exception */
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#define IDT_IO_INTS NRSVIDT /* Base of IDT entries for I/O interrupts. */
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#define IDT_SYSCALL 0x80 /* System Call Interrupt Vector */
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/*
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* Entries in the Global Descriptor Table (GDT)
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* Note that each 4 entries share a single 32 byte L1 cache line.
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* Some of the fast syscall instructions require a specific order here.
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*/
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#define GNULL_SEL 0 /* Null Descriptor */
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#define GPRIV_SEL 1 /* SMP Per-Processor Private Data */
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#define GUFS_SEL 2 /* User %fs Descriptor (order critical: 1) */
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#define GUGS_SEL 3 /* User %gs Descriptor (order critical: 2) */
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#define GCODE_SEL 4 /* Kernel Code Descriptor (order critical: 1) */
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#define GDATA_SEL 5 /* Kernel Data Descriptor (order critical: 2) */
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#define GUCODE_SEL 6 /* User Code Descriptor (order critical: 3) */
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#define GUDATA_SEL 7 /* User Data Descriptor (order critical: 4) */
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#define GBIOSLOWMEM_SEL 8 /* BIOS low memory access (must be entry 8) */
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#define GPROC0_SEL 9 /* Task state process slot zero and up */
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#define GLDT_SEL 10 /* Default User LDT */
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#define GUSERLDT_SEL 11 /* User LDT */
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#define GPANIC_SEL 12 /* Task state to consider panic from */
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#define GBIOSCODE32_SEL 13 /* BIOS interface (32bit Code) */
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#define GBIOSCODE16_SEL 14 /* BIOS interface (16bit Code) */
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#define GBIOSDATA_SEL 15 /* BIOS interface (Data) */
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#define GBIOSUTIL_SEL 16 /* BIOS interface (Utility) */
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#define GBIOSARGS_SEL 17 /* BIOS interface (Arguments) */
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#define GNDIS_SEL 18 /* For the NDIS layer */
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#define NGDT 19
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/*
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* Entries in the Local Descriptor Table (LDT)
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*/
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#define LSYS5CALLS_SEL 0 /* forced by intel BCS */
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#define LSYS5SIGR_SEL 1
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#define L43BSDCALLS_SEL 2 /* notyet */
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#define LUCODE_SEL 3
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#define LSOL26CALLS_SEL 4 /* Solaris >= 2.6 system call gate */
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#define LUDATA_SEL 5
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/* separate stack, es,fs,gs sels ? */
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/* #define LPOSIXCALLS_SEL 5*/ /* notyet */
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#define LBSDICALLS_SEL 16 /* BSDI system call gate */
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#define NLDT (LBSDICALLS_SEL + 1)
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#ifdef _KERNEL
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extern int _default_ldt;
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extern union descriptor gdt[];
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extern struct soft_segment_descriptor gdt_segs[];
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extern struct gate_descriptor *idt;
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extern union descriptor ldt[NLDT];
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extern struct region_descriptor r_gdt, r_idt;
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void lgdt(struct region_descriptor *rdp);
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void sdtossd(struct segment_descriptor *sdp,
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struct soft_segment_descriptor *ssdp);
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void ssdtosd(struct soft_segment_descriptor *ssdp,
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struct segment_descriptor *sdp);
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#endif /* _KERNEL */
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#endif /* !_MACHINE_SEGMENTS_H_ */
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