aboutsummaryrefslogtreecommitdiff
path: root/drivers/lguest/segments.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/lguest/segments.c')
-rw-r--r--drivers/lguest/segments.c125
1 files changed, 125 insertions, 0 deletions
diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c
new file mode 100644
index 00000000000..1b2cfe89dcd
--- /dev/null
+++ b/drivers/lguest/segments.c
@@ -0,0 +1,125 @@
+#include "lg.h"
+
+static int desc_ok(const struct desc_struct *gdt)
+{
+ /* MBZ=0, P=1, DT=1 */
+ return ((gdt->b & 0x00209000) == 0x00009000);
+}
+
+static int segment_present(const struct desc_struct *gdt)
+{
+ return gdt->b & 0x8000;
+}
+
+static int ignored_gdt(unsigned int num)
+{
+ return (num == GDT_ENTRY_TSS
+ || num == GDT_ENTRY_LGUEST_CS
+ || num == GDT_ENTRY_LGUEST_DS
+ || num == GDT_ENTRY_DOUBLEFAULT_TSS);
+}
+
+/* We don't allow removal of CS, DS or SS; it doesn't make sense. */
+static void check_segment_use(struct lguest *lg, unsigned int desc)
+{
+ if (lg->regs->gs / 8 == desc)
+ lg->regs->gs = 0;
+ if (lg->regs->fs / 8 == desc)
+ lg->regs->fs = 0;
+ if (lg->regs->es / 8 == desc)
+ lg->regs->es = 0;
+ if (lg->regs->ds / 8 == desc
+ || lg->regs->cs / 8 == desc
+ || lg->regs->ss / 8 == desc)
+ kill_guest(lg, "Removed live GDT entry %u", desc);
+}
+
+static void fixup_gdt_table(struct lguest *lg, unsigned start, unsigned end)
+{
+ unsigned int i;
+
+ for (i = start; i < end; i++) {
+ /* We never copy these ones to real gdt */
+ if (ignored_gdt(i))
+ continue;
+
+ /* We could fault in switch_to_guest if they are using
+ * a removed segment. */
+ if (!segment_present(&lg->gdt[i])) {
+ check_segment_use(lg, i);
+ continue;
+ }
+
+ if (!desc_ok(&lg->gdt[i]))
+ kill_guest(lg, "Bad GDT descriptor %i", i);
+
+ /* DPL 0 presumably means "for use by guest". */
+ if ((lg->gdt[i].b & 0x00006000) == 0)
+ lg->gdt[i].b |= (GUEST_PL << 13);
+
+ /* Set accessed bit, since gdt isn't writable. */
+ lg->gdt[i].b |= 0x00000100;
+ }
+}
+
+void setup_default_gdt_entries(struct lguest_ro_state *state)
+{
+ struct desc_struct *gdt = state->guest_gdt;
+ unsigned long tss = (unsigned long)&state->guest_tss;
+
+ /* Hypervisor segments. */
+ gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
+ gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
+
+ /* This is the one which we *cannot* copy from guest, since tss
+ is depended on this lguest_ro_state, ie. this cpu. */
+ gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16);
+ gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000)
+ | ((tss >> 16) & 0x000000FF);
+}
+
+void setup_guest_gdt(struct lguest *lg)
+{
+ lg->gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT;
+ lg->gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT;
+ lg->gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13);
+ lg->gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13);
+}
+
+/* This is a fast version for the common case where only the three TLS entries
+ * have changed. */
+void copy_gdt_tls(const struct lguest *lg, struct desc_struct *gdt)
+{
+ unsigned int i;
+
+ for (i = GDT_ENTRY_TLS_MIN; i <= GDT_ENTRY_TLS_MAX; i++)
+ gdt[i] = lg->gdt[i];
+}
+
+void copy_gdt(const struct lguest *lg, struct desc_struct *gdt)
+{
+ unsigned int i;
+
+ for (i = 0; i < GDT_ENTRIES; i++)
+ if (!ignored_gdt(i))
+ gdt[i] = lg->gdt[i];
+}
+
+void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num)
+{
+ if (num > ARRAY_SIZE(lg->gdt))
+ kill_guest(lg, "too many gdt entries %i", num);
+
+ lgread(lg, lg->gdt, table, num * sizeof(lg->gdt[0]));
+ fixup_gdt_table(lg, 0, ARRAY_SIZE(lg->gdt));
+ lg->changed |= CHANGED_GDT;
+}
+
+void guest_load_tls(struct lguest *lg, unsigned long gtls)
+{
+ struct desc_struct *tls = &lg->gdt[GDT_ENTRY_TLS_MIN];
+
+ lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES);
+ fixup_gdt_table(lg, GDT_ENTRY_TLS_MIN, GDT_ENTRY_TLS_MAX+1);
+ lg->changed |= CHANGED_GDT_TLS;
+}