diff options
Diffstat (limited to 'drivers/lguest/segments.c')
| -rw-r--r-- | drivers/lguest/segments.c | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c new file mode 100644 index 000000000000..1b2cfe89dcd5 --- /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; +} |