Rusty Russell | d7e28ff | 2007-07-19 01:49:23 -0700 | [diff] [blame^] | 1 | #include "lg.h" |
| 2 | |
| 3 | static int desc_ok(const struct desc_struct *gdt) |
| 4 | { |
| 5 | /* MBZ=0, P=1, DT=1 */ |
| 6 | return ((gdt->b & 0x00209000) == 0x00009000); |
| 7 | } |
| 8 | |
| 9 | static int segment_present(const struct desc_struct *gdt) |
| 10 | { |
| 11 | return gdt->b & 0x8000; |
| 12 | } |
| 13 | |
| 14 | static int ignored_gdt(unsigned int num) |
| 15 | { |
| 16 | return (num == GDT_ENTRY_TSS |
| 17 | || num == GDT_ENTRY_LGUEST_CS |
| 18 | || num == GDT_ENTRY_LGUEST_DS |
| 19 | || num == GDT_ENTRY_DOUBLEFAULT_TSS); |
| 20 | } |
| 21 | |
| 22 | /* We don't allow removal of CS, DS or SS; it doesn't make sense. */ |
| 23 | static void check_segment_use(struct lguest *lg, unsigned int desc) |
| 24 | { |
| 25 | if (lg->regs->gs / 8 == desc) |
| 26 | lg->regs->gs = 0; |
| 27 | if (lg->regs->fs / 8 == desc) |
| 28 | lg->regs->fs = 0; |
| 29 | if (lg->regs->es / 8 == desc) |
| 30 | lg->regs->es = 0; |
| 31 | if (lg->regs->ds / 8 == desc |
| 32 | || lg->regs->cs / 8 == desc |
| 33 | || lg->regs->ss / 8 == desc) |
| 34 | kill_guest(lg, "Removed live GDT entry %u", desc); |
| 35 | } |
| 36 | |
| 37 | static void fixup_gdt_table(struct lguest *lg, unsigned start, unsigned end) |
| 38 | { |
| 39 | unsigned int i; |
| 40 | |
| 41 | for (i = start; i < end; i++) { |
| 42 | /* We never copy these ones to real gdt */ |
| 43 | if (ignored_gdt(i)) |
| 44 | continue; |
| 45 | |
| 46 | /* We could fault in switch_to_guest if they are using |
| 47 | * a removed segment. */ |
| 48 | if (!segment_present(&lg->gdt[i])) { |
| 49 | check_segment_use(lg, i); |
| 50 | continue; |
| 51 | } |
| 52 | |
| 53 | if (!desc_ok(&lg->gdt[i])) |
| 54 | kill_guest(lg, "Bad GDT descriptor %i", i); |
| 55 | |
| 56 | /* DPL 0 presumably means "for use by guest". */ |
| 57 | if ((lg->gdt[i].b & 0x00006000) == 0) |
| 58 | lg->gdt[i].b |= (GUEST_PL << 13); |
| 59 | |
| 60 | /* Set accessed bit, since gdt isn't writable. */ |
| 61 | lg->gdt[i].b |= 0x00000100; |
| 62 | } |
| 63 | } |
| 64 | |
| 65 | void setup_default_gdt_entries(struct lguest_ro_state *state) |
| 66 | { |
| 67 | struct desc_struct *gdt = state->guest_gdt; |
| 68 | unsigned long tss = (unsigned long)&state->guest_tss; |
| 69 | |
| 70 | /* Hypervisor segments. */ |
| 71 | gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; |
| 72 | gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; |
| 73 | |
| 74 | /* This is the one which we *cannot* copy from guest, since tss |
| 75 | is depended on this lguest_ro_state, ie. this cpu. */ |
| 76 | gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16); |
| 77 | gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000) |
| 78 | | ((tss >> 16) & 0x000000FF); |
| 79 | } |
| 80 | |
| 81 | void setup_guest_gdt(struct lguest *lg) |
| 82 | { |
| 83 | lg->gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT; |
| 84 | lg->gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT; |
| 85 | lg->gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13); |
| 86 | lg->gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13); |
| 87 | } |
| 88 | |
| 89 | /* This is a fast version for the common case where only the three TLS entries |
| 90 | * have changed. */ |
| 91 | void copy_gdt_tls(const struct lguest *lg, struct desc_struct *gdt) |
| 92 | { |
| 93 | unsigned int i; |
| 94 | |
| 95 | for (i = GDT_ENTRY_TLS_MIN; i <= GDT_ENTRY_TLS_MAX; i++) |
| 96 | gdt[i] = lg->gdt[i]; |
| 97 | } |
| 98 | |
| 99 | void copy_gdt(const struct lguest *lg, struct desc_struct *gdt) |
| 100 | { |
| 101 | unsigned int i; |
| 102 | |
| 103 | for (i = 0; i < GDT_ENTRIES; i++) |
| 104 | if (!ignored_gdt(i)) |
| 105 | gdt[i] = lg->gdt[i]; |
| 106 | } |
| 107 | |
| 108 | void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num) |
| 109 | { |
| 110 | if (num > ARRAY_SIZE(lg->gdt)) |
| 111 | kill_guest(lg, "too many gdt entries %i", num); |
| 112 | |
| 113 | lgread(lg, lg->gdt, table, num * sizeof(lg->gdt[0])); |
| 114 | fixup_gdt_table(lg, 0, ARRAY_SIZE(lg->gdt)); |
| 115 | lg->changed |= CHANGED_GDT; |
| 116 | } |
| 117 | |
| 118 | void guest_load_tls(struct lguest *lg, unsigned long gtls) |
| 119 | { |
| 120 | struct desc_struct *tls = &lg->gdt[GDT_ENTRY_TLS_MIN]; |
| 121 | |
| 122 | lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES); |
| 123 | fixup_gdt_table(lg, GDT_ENTRY_TLS_MIN, GDT_ENTRY_TLS_MAX+1); |
| 124 | lg->changed |= CHANGED_GDT_TLS; |
| 125 | } |