1 files changed, 96 insertions, 49 deletions

diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c
index c29ffa19cb74..83511eb0923d 100644
--- a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -1,8 +1,10 @@
-/*P:500 Just as userspace programs request kernel operations through a system
+/*P:500
+ * Just as userspace programs request kernel operations through a system
  * call, the Guest requests Host operations through a "hypercall".  You might
  * notice this nomenclature doesn't really follow any logic, but the name has
  * been around for long enough that we're stuck with it.  As you'd expect, this
- * code is basically a one big switch statement. :*/
+ * code is basically a one big switch statement.
+:*/
 
 /*  Copyright (C) 2006 Rusty Russell IBM Corporation
 
@@ -28,30 +30,41 @@
 #include <asm/pgtable.h>
 #include "lg.h"
 
-/*H:120 This is the core hypercall routine: where the Guest gets what it wants.
- * Or gets killed.  Or, in the case of LHCALL_SHUTDOWN, both. */
+/*H:120
+ * This is the core hypercall routine: where the Guest gets what it wants.
+ * Or gets killed.  Or, in the case of LHCALL_SHUTDOWN, both.
+ */
 static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
 {
         switch (args->arg0) {
         case LHCALL_FLUSH_ASYNC:
-                /* This call does nothing, except by breaking out of the Guest
-                 * it makes us process all the asynchronous hypercalls. */
+                /*
+                 * This call does nothing, except by breaking out of the Guest
+                 * it makes us process all the asynchronous hypercalls.
+                 */
                 break;
         case LHCALL_SEND_INTERRUPTS:
-                /* This call does nothing too, but by breaking out of the Guest
-                 * it makes us process any pending interrupts. */
+                /*
+                 * This call does nothing too, but by breaking out of the Guest
+                 * it makes us process any pending interrupts.
+                 */
                 break;
         case LHCALL_LGUEST_INIT:
-                /* You can't get here unless you're already initialized.  Don't
-                 * do that. */
+                /*
+                 * You can't get here unless you're already initialized.  Don't
+                 * do that.
+                 */
                 kill_guest(cpu, "already have lguest_data");
                 break;
         case LHCALL_SHUTDOWN: {
-                /* Shutdown is such a trivial hypercall that we do it in four
-                 * lines right here. */
                 char msg[128];
-                /* If the lgread fails, it will call kill_guest() itself; the
-                 * kill_guest() with the message will be ignored. */
+                /*
+                 * Shutdown is such a trivial hypercall that we do it in five
+                 * lines right here.
+                 *
+                 * If the lgread fails, it will call kill_guest() itself; the
+                 * kill_guest() with the message will be ignored.
+                 */
                 __lgread(cpu, msg, args->arg1, sizeof(msg));
                 msg[sizeof(msg)-1] = '\0';
                 kill_guest(cpu, "CRASH: %s", msg);
@@ -60,16 +73,17 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
                 break;
         }
         case LHCALL_FLUSH_TLB:
-                /* FLUSH_TLB comes in two flavors, depending on the
-                 * argument: */
+                /* FLUSH_TLB comes in two flavors, depending on the argument: */
                 if (args->arg1)
                         guest_pagetable_clear_all(cpu);
                 else
                         guest_pagetable_flush_user(cpu);
                 break;
 
-        /* All these calls simply pass the arguments through to the right
-         * routines. */
+        /*
+         * All these calls simply pass the arguments through to the right
+         * routines.
+         */
         case LHCALL_NEW_PGTABLE:
                 guest_new_pagetable(cpu, args->arg1);
                 break;
@@ -112,15 +126,16 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
                         kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
         }
 }
-/*:*/
 
-/*H:124 Asynchronous hypercalls are easy: we just look in the array in the
+/*H:124
+ * Asynchronous hypercalls are easy: we just look in the array in the
  * Guest's "struct lguest_data" to see if any new ones are marked "ready".
  *
  * We are careful to do these in order: obviously we respect the order the
  * Guest put them in the ring, but we also promise the Guest that they will
  * happen before any normal hypercall (which is why we check this before
- * checking for a normal hcall). */
+ * checking for a normal hcall).
+ */
 static void do_async_hcalls(struct lg_cpu *cpu)
 {
         unsigned int i;
@@ -133,22 +148,28 @@ static void do_async_hcalls(struct lg_cpu *cpu)
         /* We process "struct lguest_data"s hcalls[] ring once. */
         for (i = 0; i < ARRAY_SIZE(st); i++) {
                 struct hcall_args args;
-                /* We remember where we were up to from last time.  This makes
+                /*
+                 * We remember where we were up to from last time.  This makes
                  * sure that the hypercalls are done in the order the Guest
-                 * places them in the ring. */
+                 * places them in the ring.
+                 */
                 unsigned int n = cpu->next_hcall;
 
                 /* 0xFF means there's no call here (yet). */
                 if (st[n] == 0xFF)
                         break;
 
-                /* OK, we have hypercall.  Increment the "next_hcall" cursor,
-                 * and wrap back to 0 if we reach the end. */
+                /*
+                 * OK, we have hypercall.  Increment the "next_hcall" cursor,
+                 * and wrap back to 0 if we reach the end.
+                 */
                 if (++cpu->next_hcall == LHCALL_RING_SIZE)
                         cpu->next_hcall = 0;
 
-                /* Copy the hypercall arguments into a local copy of
-                 * the hcall_args struct. */
+                /*
+                 * Copy the hypercall arguments into a local copy of the
+                 * hcall_args struct.
+                 */
                 if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
                                    sizeof(struct hcall_args))) {
                         kill_guest(cpu, "Fetching async hypercalls");
@@ -164,19 +185,25 @@ static void do_async_hcalls(struct lg_cpu *cpu)
                         break;
                 }
 
-                /* Stop doing hypercalls if they want to notify the Launcher:
-                 * it needs to service this first. */
+                /*
+                 * Stop doing hypercalls if they want to notify the Launcher:
+                 * it needs to service this first.
+                 */
                 if (cpu->pending_notify)
                         break;
         }
 }
 
-/* Last of all, we look at what happens first of all.  The very first time the
- * Guest makes a hypercall, we end up here to set things up: */
+/*
+ * Last of all, we look at what happens first of all.  The very first time the
+ * Guest makes a hypercall, we end up here to set things up:
+ */
 static void initialize(struct lg_cpu *cpu)
 {
-        /* You can't do anything until you're initialized.  The Guest knows the
-         * rules, so we're unforgiving here. */
+        /*
+         * You can't do anything until you're initialized.  The Guest knows the
+         * rules, so we're unforgiving here.
+         */
         if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
                 kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
                 return;
@@ -185,32 +212,44 @@ static void initialize(struct lg_cpu *cpu)
         if (lguest_arch_init_hypercalls(cpu))
                 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
 
-        /* The Guest tells us where we're not to deliver interrupts by putting
-         * the range of addresses into "struct lguest_data". */
+        /*
+         * The Guest tells us where we're not to deliver interrupts by putting
+         * the range of addresses into "struct lguest_data".
+         */
         if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
             || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
                 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
 
-        /* We write the current time into the Guest's data page once so it can
-         * set its clock. */
+        /*
+         * We write the current time into the Guest's data page once so it can
+         * set its clock.
+         */
         write_timestamp(cpu);
 
         /* page_tables.c will also do some setup. */
         page_table_guest_data_init(cpu);
 
-        /* This is the one case where the above accesses might have been the
+        /*
+         * This is the one case where the above accesses might have been the
          * first write to a Guest page.  This may have caused a copy-on-write
          * fault, but the old page might be (read-only) in the Guest
-         * pagetable. */
+         * pagetable.
+         */
         guest_pagetable_clear_all(cpu);
 }
 /*:*/
 
-/*M:013 If a Guest reads from a page (so creates a mapping) that it has never
+/*M:013
+ * If a Guest reads from a page (so creates a mapping) that it has never
  * written to, and then the Launcher writes to it (ie. the output of a virtual
  * device), the Guest will still see the old page.  In practice, this never
  * happens: why would the Guest read a page which it has never written to?  But
- * a similar scenario might one day bite us, so it's worth mentioning. :*/
+ * a similar scenario might one day bite us, so it's worth mentioning.
+ *
+ * Note that if we used a shared anonymous mapping in the Launcher instead of
+ * mapping /dev/zero private, we wouldn't worry about cop-on-write.  And we
+ * need that to switch the Launcher to processes (away from threads) anyway.
+:*/
 
 /*H:100
  * Hypercalls
@@ -229,17 +268,22 @@ void do_hypercalls(struct lg_cpu *cpu)
                 return;
         }
 
-        /* The Guest has initialized.
+        /*
+         * The Guest has initialized.
          *
-         * Look in the hypercall ring for the async hypercalls: */
+         * Look in the hypercall ring for the async hypercalls:
+         */
         do_async_hcalls(cpu);
 
-        /* If we stopped reading the hypercall ring because the Guest did a
+        /*
+         * If we stopped reading the hypercall ring because the Guest did a
          * NOTIFY to the Launcher, we want to return now.  Otherwise we do
-         * the hypercall. */
+         * the hypercall.
+         */
         if (!cpu->pending_notify) {
                 do_hcall(cpu, cpu->hcall);
-                /* Tricky point: we reset the hcall pointer to mark the
+                /*
+                 * Tricky point: we reset the hcall pointer to mark the
                  * hypercall as "done".  We use the hcall pointer rather than
                  * the trap number to indicate a hypercall is pending.
                  * Normally it doesn't matter: the Guest will run again and
@@ -248,13 +292,16 @@ void do_hypercalls(struct lg_cpu *cpu)
                  * However, if we are signalled or the Guest sends I/O to the
                  * Launcher, the run_guest() loop will exit without running the
                  * Guest.  When it comes back it would try to re-run the
-                 * hypercall.  Finding that bug sucked. */
+                 * hypercall.  Finding that bug sucked.
+                 */
                 cpu->hcall = NULL;
         }
 }
 
-/* This routine supplies the Guest with time: it's used for wallclock time at
- * initial boot and as a rough time source if the TSC isn't available. */
+/*
+ * This routine supplies the Guest with time: it's used for wallclock time at
+ * initial boot and as a rough time source if the TSC isn't available.
+ */
 void write_timestamp(struct lg_cpu *cpu)
 {
         struct timespec now;