lguest: the host code

This is the code for the "lg.ko" module, which allows lguest guests to
be launched.

[akpm@linux-foundation.org: update for futex-new-private-futexes]
[akpm@linux-foundation.org: build fix]
[jmorris@namei.org: lguest: use hrtimers]
[akpm@linux-foundation.org: x86_64 build fix]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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;
+}