1 files changed, 69 insertions, 37 deletions

diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c
index 482ed5a18750..951c57b0a7e0 100644
--- a/drivers/lguest/segments.c
+++ b/drivers/lguest/segments.c
@@ -1,4 +1,5 @@
-/*P:600 The x86 architecture has segments, which involve a table of descriptors
+/*P:600
+ * The x86 architecture has segments, which involve a table of descriptors
  * which can be used to do funky things with virtual address interpretation.
  * We originally used to use segments so the Guest couldn't alter the
  * Guest<->Host Switcher, and then we had to trim Guest segments, and restore
@@ -8,7 +9,8 @@
  *
  * In these modern times, the segment handling code consists of simple sanity
  * checks, and the worst you'll experience reading this code is butterfly-rash
- * from frolicking through its parklike serenity. :*/
+ * from frolicking through its parklike serenity.
+:*/
 #include "lg.h"
 
 /*H:600
@@ -41,10 +43,12 @@
  * begin.
  */
 
-/* There are several entries we don't let the Guest set.  The TSS entry is the
+/*
+ * There are several entries we don't let the Guest set.  The TSS entry is the
  * "Task State Segment" which controls all kinds of delicate things.  The
  * LGUEST_CS and LGUEST_DS entries are reserved for the Switcher, and the
- * the Guest can't be trusted to deal with double faults. */
+ * the Guest can't be trusted to deal with double faults.
+ */
 static bool ignored_gdt(unsigned int num)
 {
         return (num == GDT_ENTRY_TSS
@@ -53,42 +57,52 @@ static bool ignored_gdt(unsigned int num)
                 || num == GDT_ENTRY_DOUBLEFAULT_TSS);
 }
 
-/*H:630 Once the Guest gave us new GDT entries, we fix them up a little.  We
+/*H:630
+ * Once the Guest gave us new GDT entries, we fix them up a little.  We
  * don't care if they're invalid: the worst that can happen is a General
  * Protection Fault in the Switcher when it restores a Guest segment register
  * which tries to use that entry.  Then we kill the Guest for causing such a
- * mess: the message will be "unhandled trap 256". */
+ * mess: the message will be "unhandled trap 256".
+ */
 static void fixup_gdt_table(struct lg_cpu *cpu, unsigned start, unsigned end)
 {
         unsigned int i;
 
         for (i = start; i < end; i++) {
-                /* We never copy these ones to real GDT, so we don't care what
-                 * they say */
+                /*
+                 * We never copy these ones to real GDT, so we don't care what
+                 * they say
+                 */
                 if (ignored_gdt(i))
                         continue;
 
-                /* Segment descriptors contain a privilege level: the Guest is
+                /*
+                 * Segment descriptors contain a privilege level: the Guest is
                  * sometimes careless and leaves this as 0, even though it's
-                 * running at privilege level 1.  If so, we fix it here. */
+                 * running at privilege level 1.  If so, we fix it here.
+                 */
                 if ((cpu->arch.gdt[i].b & 0x00006000) == 0)
                         cpu->arch.gdt[i].b |= (GUEST_PL << 13);
 
-                /* Each descriptor has an "accessed" bit.  If we don't set it
+                /*
+                 * Each descriptor has an "accessed" bit.  If we don't set it
                  * now, the CPU will try to set it when the Guest first loads
                  * that entry into a segment register.  But the GDT isn't
-                 * writable by the Guest, so bad things can happen. */
+                 * writable by the Guest, so bad things can happen.
+                 */
                 cpu->arch.gdt[i].b |= 0x00000100;
         }
 }
 
-/*H:610 Like the IDT, we never simply use the GDT the Guest gives us.  We keep
+/*H:610
+ * Like the IDT, we never simply use the GDT the Guest gives us.  We keep
  * a GDT for each CPU, and copy across the Guest's entries each time we want to
  * run the Guest on that CPU.
  *
  * This routine is called at boot or modprobe time for each CPU to set up the
  * constant GDT entries: the ones which are the same no matter what Guest we're
- * running. */
+ * running.
+ */
 void setup_default_gdt_entries(struct lguest_ro_state *state)
 {
         struct desc_struct *gdt = state->guest_gdt;
@@ -98,30 +112,37 @@ void setup_default_gdt_entries(struct lguest_ro_state *state)
         gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
         gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
 
-        /* The TSS segment refers to the TSS entry for this particular CPU.
+        /*
+         * The TSS segment refers to the TSS entry for this particular CPU.
          * Forgive the magic flags: the 0x8900 means the entry is Present, it's
          * privilege level 0 Available 386 TSS system segment, and the 0x67
-         * means Saturn is eclipsed by Mercury in the twelfth house. */
+         * means Saturn is eclipsed by Mercury in the twelfth house.
+         */
         gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16);
         gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000)
                 | ((tss >> 16) & 0x000000FF);
 }
 
-/* This routine sets up the initial Guest GDT for booting.  All entries start
- * as 0 (unusable). */
+/*
+ * This routine sets up the initial Guest GDT for booting.  All entries start
+ * as 0 (unusable).
+ */
 void setup_guest_gdt(struct lg_cpu *cpu)
 {
-        /* Start with full 0-4G segments... */
+        /*
+         * Start with full 0-4G segments...except the Guest is allowed to use
+         * them, so set the privilege level appropriately in the flags.
+         */
         cpu->arch.gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT;
         cpu->arch.gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT;
-        /* ...except the Guest is allowed to use them, so set the privilege
-         * level appropriately in the flags. */
         cpu->arch.gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13);
         cpu->arch.gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13);
 }
 
-/*H:650 An optimization of copy_gdt(), for just the three "thead-local storage"
- * entries. */
+/*H:650
+ * An optimization of copy_gdt(), for just the three "thead-local storage"
+ * entries.
+ */
 void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt)
 {
         unsigned int i;
@@ -130,26 +151,34 @@ void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt)
                 gdt[i] = cpu->arch.gdt[i];
 }
 
-/*H:640 When the Guest is run on a different CPU, or the GDT entries have
- * changed, copy_gdt() is called to copy the Guest's GDT entries across to this
- * CPU's GDT. */
+/*H:640
+ * When the Guest is run on a different CPU, or the GDT entries have changed,
+ * copy_gdt() is called to copy the Guest's GDT entries across to this CPU's
+ * GDT.
+ */
 void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt)
 {
         unsigned int i;
 
-        /* The default entries from setup_default_gdt_entries() are not
-         * replaced.  See ignored_gdt() above. */
+        /*
+         * The default entries from setup_default_gdt_entries() are not
+         * replaced.  See ignored_gdt() above.
+         */
         for (i = 0; i < GDT_ENTRIES; i++)
                 if (!ignored_gdt(i))
                         gdt[i] = cpu->arch.gdt[i];
 }
 
-/*H:620 This is where the Guest asks us to load a new GDT entry
- * (LHCALL_LOAD_GDT_ENTRY).  We tweak the entry and copy it in. */
+/*H:620
+ * This is where the Guest asks us to load a new GDT entry
+ * (LHCALL_LOAD_GDT_ENTRY).  We tweak the entry and copy it in.
+ */
 void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi)
 {
-        /* We assume the Guest has the same number of GDT entries as the
-         * Host, otherwise we'd have to dynamically allocate the Guest GDT. */
+        /*
+         * We assume the Guest has the same number of GDT entries as the
+         * Host, otherwise we'd have to dynamically allocate the Guest GDT.
+         */
         if (num >= ARRAY_SIZE(cpu->arch.gdt))
                 kill_guest(cpu, "too many gdt entries %i", num);
 
@@ -157,15 +186,19 @@ void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi)
         cpu->arch.gdt[num].a = lo;
         cpu->arch.gdt[num].b = hi;
         fixup_gdt_table(cpu, num, num+1);
-        /* Mark that the GDT changed so the core knows it has to copy it again,
-         * even if the Guest is run on the same CPU. */
+        /*
+         * Mark that the GDT changed so the core knows it has to copy it again,
+         * even if the Guest is run on the same CPU.
+         */
         cpu->changed |= CHANGED_GDT;
 }
 
-/* This is the fast-track version for just changing the three TLS entries.
+/*
+ * This is the fast-track version for just changing the three TLS entries.
  * Remember that this happens on every context switch, so it's worth
  * optimizing.  But wouldn't it be neater to have a single hypercall to cover
- * both cases? */
+ * both cases?
+ */
 void guest_load_tls(struct lg_cpu *cpu, unsigned long gtls)
 {
         struct desc_struct *tls = &cpu->arch.gdt[GDT_ENTRY_TLS_MIN];
@@ -175,7 +208,6 @@ void guest_load_tls(struct lg_cpu *cpu, unsigned long gtls)
         /* Note that just the TLS entries have changed. */
         cpu->changed |= CHANGED_GDT_TLS;
 }
-/*:*/
 
 /*H:660
  * With this, we have finished the Host.