1 files changed, 327 insertions, 0 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
new file mode 100644
index 0000000..90663e0
--- /dev/null
+++ b/drivers/lguest/core.c
@@ -0,0 +1,327 @@
+/*P:400 This contains run_guest() which actually calls into the Host<->Guest
+ * Switcher and analyzes the return, such as determining if the Guest wants the
+ * Host to do something.  This file also contains useful helper routines. :*/
+#include <linux/module.h>
+#include <linux/stringify.h>
+#include <linux/stddef.h>
+#include <linux/io.h>
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/cpu.h>
+#include <linux/freezer.h>
+#include <linux/highmem.h>
+#include <asm/paravirt.h>
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/poll.h>
+#include <asm/asm-offsets.h>
+#include "lg.h"
+
+
+static struct vm_struct *switcher_vma;
+static struct page **switcher_page;
+
+/* This One Big lock protects all inter-guest data structures. */
+DEFINE_MUTEX(lguest_lock);
+
+/*H:010 We need to set up the Switcher at a high virtual address.  Remember the
+ * Switcher is a few hundred bytes of assembler code which actually changes the
+ * CPU to run the Guest, and then changes back to the Host when a trap or
+ * interrupt happens.
+ *
+ * The Switcher code must be at the same virtual address in the Guest as the
+ * Host since it will be running as the switchover occurs.
+ *
+ * Trying to map memory at a particular address is an unusual thing to do, so
+ * it's not a simple one-liner. */
+static __init int map_switcher(void)
+{
+	int i, err;
+	struct page **pagep;
+
+	/*
+	 * Map the Switcher in to high memory.
+	 *
+	 * It turns out that if we choose the address 0xFFC00000 (4MB under the
+	 * top virtual address), it makes setting up the page tables really
+	 * easy.
+	 */
+
+	/* We allocate an array of struct page pointers.  map_vm_area() wants
+	 * this, rather than just an array of pages. */
+	switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
+				GFP_KERNEL);
+	if (!switcher_page) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	/* Now we actually allocate the pages.  The Guest will see these pages,
+	 * so we make sure they're zeroed. */
+	for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
+		unsigned long addr = get_zeroed_page(GFP_KERNEL);
+		if (!addr) {
+			err = -ENOMEM;
+			goto free_some_pages;
+		}
+		switcher_page[i] = virt_to_page(addr);
+	}
+
+	/* First we check that the Switcher won't overlap the fixmap area at
+	 * the top of memory.  It's currently nowhere near, but it could have
+	 * very strange effects if it ever happened. */
+	if (SWITCHER_ADDR + (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE > FIXADDR_START){
+		err = -ENOMEM;
+		printk("lguest: mapping switcher would thwack fixmap\n");
+		goto free_pages;
+	}
+
+	/* Now we reserve the "virtual memory area" we want: 0xFFC00000
+	 * (SWITCHER_ADDR).  We might not get it in theory, but in practice
+	 * it's worked so far.  The end address needs +1 because __get_vm_area
+	 * allocates an extra guard page, so we need space for that. */
+	switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
+				     VM_ALLOC, SWITCHER_ADDR, SWITCHER_ADDR
+				     + (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE);
+	if (!switcher_vma) {
+		err = -ENOMEM;
+		printk("lguest: could not map switcher pages high\n");
+		goto free_pages;
+	}
+
+	/* This code actually sets up the pages we've allocated to appear at
+	 * SWITCHER_ADDR.  map_vm_area() takes the vma we allocated above, the
+	 * kind of pages we're mapping (kernel pages), and a pointer to our
+	 * array of struct pages.  It increments that pointer, but we don't
+	 * care. */
+	pagep = switcher_page;
+	err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep);
+	if (err) {
+		printk("lguest: map_vm_area failed: %i\n", err);
+		goto free_vma;
+	}
+
+	/* Now the Switcher is mapped at the right address, we can't fail!
+	 * Copy in the compiled-in Switcher code (from <arch>_switcher.S). */
+	memcpy(switcher_vma->addr, start_switcher_text,
+	       end_switcher_text - start_switcher_text);
+
+	printk(KERN_INFO "lguest: mapped switcher at %p\n",
+	       switcher_vma->addr);
+	/* And we succeeded... */
+	return 0;
+
+free_vma:
+	vunmap(switcher_vma->addr);
+free_pages:
+	i = TOTAL_SWITCHER_PAGES;
+free_some_pages:
+	for (--i; i >= 0; i--)
+		__free_pages(switcher_page[i], 0);
+	kfree(switcher_page);
+out:
+	return err;
+}
+/*:*/
+
+/* Cleaning up the mapping when the module is unloaded is almost...
+ * too easy. */
+static void unmap_switcher(void)
+{
+	unsigned int i;
+
+	/* vunmap() undoes *both* map_vm_area() and __get_vm_area(). */
+	vunmap(switcher_vma->addr);
+	/* Now we just need to free the pages we copied the switcher into */
+	for (i = 0; i < TOTAL_SWITCHER_PAGES; i++)
+		__free_pages(switcher_page[i], 0);
+	kfree(switcher_page);
+}
+
+/*H:032
+ * Dealing With Guest Memory.
+ *
+ * Before we go too much further into the Host, we need to grok the routines
+ * we use to deal with Guest memory.
+ *
+ * When the Guest gives us (what it thinks is) a physical address, we can use
+ * the normal copy_from_user() & copy_to_user() on the corresponding place in
+ * the memory region allocated by the Launcher.
+ *
+ * But we can't trust the Guest: it might be trying to access the Launcher
+ * code.  We have to check that the range is below the pfn_limit the Launcher
+ * gave us.  We have to make sure that addr + len doesn't give us a false
+ * positive by overflowing, too. */
+int lguest_address_ok(const struct lguest *lg,
+		      unsigned long addr, unsigned long len)
+{
+	return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
+}
+
+/* This routine copies memory from the Guest.  Here we can see how useful the
+ * kill_lguest() routine we met in the Launcher can be: we return a random
+ * value (all zeroes) instead of needing to return an error. */
+void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes)
+{
+	if (!lguest_address_ok(cpu->lg, addr, bytes)
+	    || copy_from_user(b, cpu->lg->mem_base + addr, bytes) != 0) {
+		/* copy_from_user should do this, but as we rely on it... */
+		memset(b, 0, bytes);
+		kill_guest(cpu, "bad read address %#lx len %u", addr, bytes);
+	}
+}
+
+/* This is the write (copy into Guest) version. */
+void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b,
+	       unsigned bytes)
+{
+	if (!lguest_address_ok(cpu->lg, addr, bytes)
+	    || copy_to_user(cpu->lg->mem_base + addr, b, bytes) != 0)
+		kill_guest(cpu, "bad write address %#lx len %u", addr, bytes);
+}
+/*:*/
+
+/*H:030 Let's jump straight to the the main loop which runs the Guest.
+ * Remember, this is called by the Launcher reading /dev/lguest, and we keep
+ * going around and around until something interesting happens. */
+int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
+{
+	/* We stop running once the Guest is dead. */
+	while (!cpu->lg->dead) {
+		/* First we run any hypercalls the Guest wants done. */
+		if (cpu->hcall)
+			do_hypercalls(cpu);
+
+		/* It's possible the Guest did a NOTIFY hypercall to the
+		 * Launcher, in which case we return from the read() now. */
+		if (cpu->pending_notify) {
+			if (put_user(cpu->pending_notify, user))
+				return -EFAULT;
+			return sizeof(cpu->pending_notify);
+		}
+
+		/* Check for signals */
+		if (signal_pending(current))
+			return -ERESTARTSYS;
+
+		/* If Waker set break_out, return to Launcher. */
+		if (cpu->break_out)
+			return -EAGAIN;
+
+		/* Check if there are any interrupts which can be delivered now:
+		 * if so, this sets up the hander to be executed when we next
+		 * run the Guest. */
+		maybe_do_interrupt(cpu);
+
+		/* All long-lived kernel loops need to check with this horrible
+		 * thing called the freezer.  If the Host is trying to suspend,
+		 * it stops us. */
+		try_to_freeze();
+
+		/* Just make absolutely sure the Guest is still alive.  One of
+		 * those hypercalls could have been fatal, for example. */
+		if (cpu->lg->dead)
+			break;
+
+		/* If the Guest asked to be stopped, we sleep.  The Guest's
+		 * clock timer or LHCALL_BREAK from the Waker will wake us. */
+		if (cpu->halted) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			schedule();
+			continue;
+		}
+
+		/* OK, now we're ready to jump into the Guest.  First we put up
+		 * the "Do Not Disturb" sign: */
+		local_irq_disable();
+
+		/* Actually run the Guest until something happens. */
+		lguest_arch_run_guest(cpu);
+
+		/* Now we're ready to be interrupted or moved to other CPUs */
+		local_irq_enable();
+
+		/* Now we deal with whatever happened to the Guest. */
+		lguest_arch_handle_trap(cpu);
+	}
+
+	/* Special case: Guest is 'dead' but wants a reboot. */
+	if (cpu->lg->dead == ERR_PTR(-ERESTART))
+		return -ERESTART;
+
+	/* The Guest is dead => "No such file or directory" */
+	return -ENOENT;
+}
+
+/*H:000
+ * Welcome to the Host!
+ *
+ * By this point your brain has been tickled by the Guest code and numbed by
+ * the Launcher code; prepare for it to be stretched by the Host code.  This is
+ * the heart.  Let's begin at the initialization routine for the Host's lg
+ * module.
+ */
+static int __init init(void)
+{
+	int err;
+
+	/* Lguest can't run under Xen, VMI or itself.  It does Tricky Stuff. */
+	if (paravirt_enabled()) {
+		printk("lguest is afraid of being a guest\n");
+		return -EPERM;
+	}
+
+	/* First we put the Switcher up in very high virtual memory. */
+	err = map_switcher();
+	if (err)
+		goto out;
+
+	/* Now we set up the pagetable implementation for the Guests. */
+	err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES);
+	if (err)
+		goto unmap;
+
+	/* We might need to reserve an interrupt vector. */
+	err = init_interrupts();
+	if (err)
+		goto free_pgtables;
+
+	/* /dev/lguest needs to be registered. */
+	err = lguest_device_init();
+	if (err)
+		goto free_interrupts;
+
+	/* Finally we do some architecture-specific setup. */
+	lguest_arch_host_init();
+
+	/* All good! */
+	return 0;
+
+free_interrupts:
+	free_interrupts();
+free_pgtables:
+	free_pagetables();
+unmap:
+	unmap_switcher();
+out:
+	return err;
+}
+
+/* Cleaning up is just the same code, backwards.  With a little French. */
+static void __exit fini(void)
+{
+	lguest_device_remove();
+	free_interrupts();
+	free_pagetables();
+	unmap_switcher();
+
+	lguest_arch_host_fini();
+}
+/*:*/
+
+/* The Host side of lguest can be a module.  This is a nice way for people to
+ * play with it.  */
+module_init(init);
+module_exit(fini);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");