Initial import

1 files changed, 308 insertions, 0 deletions

diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c
new file mode 100644
index 000000000..19a322807
--- /dev/null
+++ b/drivers/lguest/hypercalls.c
@@ -0,0 +1,308 @@
+/*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.
+:*/
+
+/*  Copyright (C) 2006 Rusty Russell IBM Corporation
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+*/
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+#include <linux/mm.h>
+#include <linux/ktime.h>
+#include <asm/page.h>
+#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.
+ */
+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.
+		 */
+		break;
+	case LHCALL_SEND_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.
+		 */
+		kill_guest(cpu, "already have lguest_data");
+		break;
+	case LHCALL_SHUTDOWN: {
+		char msg[128];
+		/*
+		 * 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);
+		if (args->arg2 == LGUEST_SHUTDOWN_RESTART)
+			cpu->lg->dead = ERR_PTR(-ERESTART);
+		break;
+	}
+	case LHCALL_FLUSH_TLB:
+		/* 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.
+	 */
+	case LHCALL_NEW_PGTABLE:
+		guest_new_pagetable(cpu, args->arg1);
+		break;
+	case LHCALL_SET_STACK:
+		guest_set_stack(cpu, args->arg1, args->arg2, args->arg3);
+		break;
+	case LHCALL_SET_PTE:
+#ifdef CONFIG_X86_PAE
+		guest_set_pte(cpu, args->arg1, args->arg2,
+				__pte(args->arg3 | (u64)args->arg4 << 32));
+#else
+		guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3));
+#endif
+		break;
+	case LHCALL_SET_PGD:
+		guest_set_pgd(cpu->lg, args->arg1, args->arg2);
+		break;
+#ifdef CONFIG_X86_PAE
+	case LHCALL_SET_PMD:
+		guest_set_pmd(cpu->lg, args->arg1, args->arg2);
+		break;
+#endif
+	case LHCALL_SET_CLOCKEVENT:
+		guest_set_clockevent(cpu, args->arg1);
+		break;
+	case LHCALL_TS:
+		/* This sets the TS flag, as we saw used in run_guest(). */
+		cpu->ts = args->arg1;
+		break;
+	case LHCALL_HALT:
+		/* Similarly, this sets the halted flag for run_guest(). */
+		cpu->halted = 1;
+		break;
+	default:
+		/* It should be an architecture-specific hypercall. */
+		if (lguest_arch_do_hcall(cpu, args))
+			kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
+	}
+}
+
+/*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).
+ */
+static void do_async_hcalls(struct lg_cpu *cpu)
+{
+	unsigned int i;
+	u8 st[LHCALL_RING_SIZE];
+
+	/* For simplicity, we copy the entire call status array in at once. */
+	if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st)))
+		return;
+
+	/* 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
+		 * sure that the hypercalls are done in the order the Guest
+		 * 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.
+		 */
+		if (++cpu->next_hcall == LHCALL_RING_SIZE)
+			cpu->next_hcall = 0;
+
+		/*
+		 * 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");
+			break;
+		}
+
+		/* Do the hypercall, same as a normal one. */
+		do_hcall(cpu, &args);
+
+		/* Mark the hypercall done. */
+		if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) {
+			kill_guest(cpu, "Writing result for async hypercall");
+			break;
+		}
+
+		/*
+		 * Stop doing hypercalls if they want to notify the Launcher:
+		 * it needs to service this first.
+		 */
+		if (cpu->pending.trap)
+			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:
+ */
+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.
+	 */
+	if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
+		kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
+		return;
+	}
+
+	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 instruction address into "struct lguest_data".
+	 */
+	if (get_user(cpu->lg->noirq_iret, &cpu->lg->lguest_data->noirq_iret))
+		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.
+	 */
+	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
+	 * 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.
+	 */
+	guest_pagetable_clear_all(cpu);
+}
+/*:*/
+
+/*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.
+ *
+ * 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
+ *
+ * Remember from the Guest, hypercalls come in two flavors: normal and
+ * asynchronous.  This file handles both of types.
+ */
+void do_hypercalls(struct lg_cpu *cpu)
+{
+	/* Not initialized yet?  This hypercall must do it. */
+	if (unlikely(!cpu->lg->lguest_data)) {
+		/* Set up the "struct lguest_data" */
+		initialize(cpu);
+		/* Hcall is done. */
+		cpu->hcall = NULL;
+		return;
+	}
+
+	/*
+	 * The Guest has initialized.
+	 *
+	 * 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
+	 * NOTIFY to the Launcher, we want to return now.  Otherwise we do
+	 * the hypercall.
+	 */
+	if (!cpu->pending.trap) {
+		do_hcall(cpu, cpu->hcall);
+		/*
+		 * 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
+		 * update the trap number before we come back here.
+		 *
+		 * 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.
+		 */
+		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.
+ */
+void write_timestamp(struct lg_cpu *cpu)
+{
+	struct timespec now;
+	ktime_get_real_ts(&now);
+	if (copy_to_user(&cpu->lg->lguest_data->time,
+			 &now, sizeof(struct timespec)))
+		kill_guest(cpu, "Writing timestamp");
+}