126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
#include "lg.h"
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static int desc_ok(const struct desc_struct *gdt)
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{
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/* MBZ=0, P=1, DT=1 */
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return ((gdt->b & 0x00209000) == 0x00009000);
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}
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static int segment_present(const struct desc_struct *gdt)
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{
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return gdt->b & 0x8000;
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}
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static int ignored_gdt(unsigned int num)
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{
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return (num == GDT_ENTRY_TSS
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|| num == GDT_ENTRY_LGUEST_CS
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|| num == GDT_ENTRY_LGUEST_DS
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|| num == GDT_ENTRY_DOUBLEFAULT_TSS);
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}
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/* We don't allow removal of CS, DS or SS; it doesn't make sense. */
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static void check_segment_use(struct lguest *lg, unsigned int desc)
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{
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if (lg->regs->gs / 8 == desc)
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lg->regs->gs = 0;
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if (lg->regs->fs / 8 == desc)
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lg->regs->fs = 0;
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if (lg->regs->es / 8 == desc)
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lg->regs->es = 0;
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if (lg->regs->ds / 8 == desc
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|| lg->regs->cs / 8 == desc
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|| lg->regs->ss / 8 == desc)
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kill_guest(lg, "Removed live GDT entry %u", desc);
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}
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static void fixup_gdt_table(struct lguest *lg, unsigned start, unsigned end)
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{
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unsigned int i;
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for (i = start; i < end; i++) {
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/* We never copy these ones to real gdt */
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if (ignored_gdt(i))
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continue;
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/* We could fault in switch_to_guest if they are using
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* a removed segment. */
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if (!segment_present(&lg->gdt[i])) {
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check_segment_use(lg, i);
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continue;
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}
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if (!desc_ok(&lg->gdt[i]))
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kill_guest(lg, "Bad GDT descriptor %i", i);
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/* DPL 0 presumably means "for use by guest". */
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if ((lg->gdt[i].b & 0x00006000) == 0)
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lg->gdt[i].b |= (GUEST_PL << 13);
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/* Set accessed bit, since gdt isn't writable. */
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lg->gdt[i].b |= 0x00000100;
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}
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}
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void setup_default_gdt_entries(struct lguest_ro_state *state)
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{
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struct desc_struct *gdt = state->guest_gdt;
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unsigned long tss = (unsigned long)&state->guest_tss;
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/* Hypervisor segments. */
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gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
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gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
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/* This is the one which we *cannot* copy from guest, since tss
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is depended on this lguest_ro_state, ie. this cpu. */
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gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16);
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gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000)
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| ((tss >> 16) & 0x000000FF);
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}
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void setup_guest_gdt(struct lguest *lg)
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{
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lg->gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT;
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lg->gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT;
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lg->gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13);
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lg->gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13);
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}
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/* This is a fast version for the common case where only the three TLS entries
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* have changed. */
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void copy_gdt_tls(const struct lguest *lg, struct desc_struct *gdt)
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{
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unsigned int i;
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for (i = GDT_ENTRY_TLS_MIN; i <= GDT_ENTRY_TLS_MAX; i++)
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gdt[i] = lg->gdt[i];
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}
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void copy_gdt(const struct lguest *lg, struct desc_struct *gdt)
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{
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unsigned int i;
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for (i = 0; i < GDT_ENTRIES; i++)
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if (!ignored_gdt(i))
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gdt[i] = lg->gdt[i];
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}
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void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num)
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{
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if (num > ARRAY_SIZE(lg->gdt))
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kill_guest(lg, "too many gdt entries %i", num);
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lgread(lg, lg->gdt, table, num * sizeof(lg->gdt[0]));
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fixup_gdt_table(lg, 0, ARRAY_SIZE(lg->gdt));
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lg->changed |= CHANGED_GDT;
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}
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void guest_load_tls(struct lguest *lg, unsigned long gtls)
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{
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struct desc_struct *tls = &lg->gdt[GDT_ENTRY_TLS_MIN];
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lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES);
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fixup_gdt_table(lg, GDT_ENTRY_TLS_MIN, GDT_ENTRY_TLS_MAX+1);
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lg->changed |= CHANGED_GDT_TLS;
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}
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