1/*- 2 * Copyright (c) 2014, 2015 Antti Kantee. All Rights Reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 14 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 16 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 19 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23 * SUCH DAMAGE. 24 */ 25 26/* 27 * We need to provide a segment for gs for TLS to work, so we need to 28 * install our own gdt. Hence, all this complexity follows. 29 */ 30 31#include <bmk-core/platform.h> 32#include <bmk-core/string.h> 33 34#include <mini-os/hypervisor.h> 35#include <mini-os/mm.h> 36#include <mini-os/os.h> 37 38#if defined(__i386__) 39 40/* 41 * i386 MD desciptor, assimilated from NetBSD sys/arch/i386/include/segments.h 42 */ 43 44struct segment_descriptor { 45 unsigned sd_lolimit:16; 46 unsigned sd_lobase:24; 47 unsigned sd_type:5; 48 unsigned sd_dpl:2; 49 unsigned sd_p:1; 50 unsigned sd_hilimit:4; 51 unsigned sd_xx:2; 52 unsigned sd_def32:1; 53 unsigned sd_gran:1; 54 unsigned sd_hibase:8; 55} __attribute__((__packed__)); 56 57#define SDT_MEMRWA 19 /* memory read write accessed */ 58#define SDT_MEMERA 27 /* memory execute read accessed */ 59 60#define SEGMENT_CODE (__KERNEL_CS>>3) 61#define SEGMENT_DATA (__KERNEL_DS>>3) 62#define SEGMENT_GS (__KERNEL_GS>>3) 63 64/* 65 * Make sure the gdt takes up exactly 1 page since we need(?) to 66 * map it read-only before we pass it up to Xen. 67 */ 68#define GDTCOUNT (PAGE_SIZE/sizeof(struct segment_descriptor)) 69static struct segment_descriptor gdt[GDTCOUNT] 70 __attribute__((aligned(PAGE_SIZE))); 71static unsigned long long gs_pa; 72 73static union { 74 struct segment_descriptor gs; 75 unsigned long long gs_raw; 76} gs; 77 78void _minios_entry_load_segmentregs(void); 79 80static void 81fillsegment(struct segment_descriptor *sd, int type) 82{ 83 84 sd->sd_lobase = 0; 85 sd->sd_hibase = 0; 86 87 sd->sd_lolimit = 0xffff; 88 sd->sd_hilimit = 0xf; 89 90 sd->sd_type = type; 91 92 sd->sd_dpl = 1; 93 sd->sd_p = 1; 94 sd->sd_xx = 0; 95 sd->sd_def32 = 1; 96 sd->sd_gran = 1; 97} 98 99void 100tlsswitch32(unsigned long p) 101{ 102 103 gs.gs.sd_lobase = p & 0xffffff; 104 gs.gs.sd_hibase = (p >> 24) & 0xff; 105 if (HYPERVISOR_update_descriptor(gs_pa, gs.gs_raw)) 106 bmk_platform_halt("updating TLS descriptor failed"); 107 108 /* reload gs register to finalize change */ 109 __asm__ __volatile__("mov %0, %%gs" :: "r"(__KERNEL_GS)); 110} 111 112void 113gdtinit32(void) 114{ 115 pte_t pte; 116 unsigned long frames[1]; 117 int error; 118 119 fillsegment(&gdt[SEGMENT_CODE], SDT_MEMERA); 120 fillsegment(&gdt[SEGMENT_DATA], SDT_MEMRWA); 121 fillsegment(&gdt[SEGMENT_GS], SDT_MEMRWA); 122 123 pte = __pte((virt_to_mach(&gdt)) | L1_PROT_RO); 124 if (HYPERVISOR_update_va_mapping((unsigned long)&gdt, pte, UVMF_INVLPG)) 125 bmk_platform_halt("make gdt r/o"); 126 127 frames[0] = virt_to_mfn(&gdt); 128 if ((error = HYPERVISOR_set_gdt(frames, 512) != 0)) { 129 bmk_platform_halt("set_gdt"); 130 } 131 _minios_entry_load_segmentregs(); 132 133 /* cache things for the TLS switch */ 134 bmk_memcpy(&gs, &gdt[SEGMENT_GS], sizeof(gs)); 135 gs_pa = virt_to_mach(&gdt[SEGMENT_GS]); 136} 137#endif /* __i386__ */ 138