--- /dev/null
+/*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 <linux/slab.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"
+
+unsigned long switcher_addr;
+struct page **lg_switcher_pages;
+static struct vm_struct *switcher_vma;
+
+/* 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;
+
+ /*
+ * 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 assume Switcher text fits into a single page. */
+ if (end_switcher_text - start_switcher_text > PAGE_SIZE) {
+ printk(KERN_ERR "lguest: switcher text too large (%zu)\n",
+ end_switcher_text - start_switcher_text);
+ return -EINVAL;
+ }
+
+ /*
+ * We allocate an array of struct page pointers. map_vm_area() wants
+ * this, rather than just an array of pages.
+ */
+ lg_switcher_pages = kmalloc(sizeof(lg_switcher_pages[0])
+ * TOTAL_SWITCHER_PAGES,
+ GFP_KERNEL);
+ if (!lg_switcher_pages) {
+ 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++) {
+ lg_switcher_pages[i] = alloc_page(GFP_KERNEL|__GFP_ZERO);
+ if (!lg_switcher_pages[i]) {
+ err = -ENOMEM;
+ goto free_some_pages;
+ }
+ }
+
+ /*
+ * We place the Switcher underneath the fixmap area, which is the
+ * highest virtual address we can get. This is important, since we
+ * tell the Guest it can't access this memory, so we want its ceiling
+ * as high as possible.
+ */
+ switcher_addr = FIXADDR_START - (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE;
+
+ /*
+ * Now we reserve the "virtual memory area" we want. 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.
+ */
+ err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, lg_switcher_pages);
+ 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 x86/switcher_32.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(lg_switcher_pages[i], 0);
+ kfree(lg_switcher_pages);
+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(lg_switcher_pages[i], 0);
+ kfree(lg_switcher_pages);
+}
+
+/*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.
+ */
+bool lguest_address_ok(const struct lguest *lg,
+ unsigned long addr, unsigned long len)
+{
+ return addr+len <= lg->pfn_limit * PAGE_SIZE && (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)
+{
+ /* If the launcher asked for a register with LHREQ_GETREG */
+ if (cpu->reg_read) {
+ if (put_user(*cpu->reg_read, user))
+ return -EFAULT;
+ cpu->reg_read = NULL;
+ return sizeof(*cpu->reg_read);
+ }
+
+ /* We stop running once the Guest is dead. */
+ while (!cpu->lg->dead) {
+ unsigned int irq;
+ bool more;
+
+ /* First we run any hypercalls the Guest wants done. */
+ if (cpu->hcall)
+ do_hypercalls(cpu);
+
+ /* Do we have to tell the Launcher about a trap? */
+ if (cpu->pending.trap) {
+ if (copy_to_user(user, &cpu->pending,
+ sizeof(cpu->pending)))
+ return -EFAULT;
+ return sizeof(cpu->pending);
+ }
+
+ /*
+ * 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();
+
+ /* Check for signals */
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+
+ /*
+ * 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.
+ */
+ irq = interrupt_pending(cpu, &more);
+ if (irq < LGUEST_IRQS)
+ try_deliver_interrupt(cpu, irq, more);
+
+ /*
+ * 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 will wake us.
+ */
+ if (cpu->halted) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ /*
+ * Just before we sleep, make sure no interrupt snuck in
+ * which we should be doing.
+ */
+ if (interrupt_pending(cpu, &more) < LGUEST_IRQS)
+ set_current_state(TASK_RUNNING);
+ else
+ 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 (get_kernel_rpl() != 0) {
+ 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;
+
+ /* We might need to reserve an interrupt vector. */
+ err = init_interrupts();
+ if (err)
+ goto unmap;
+
+ /* /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();
+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();
+ 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>");
Code Review / kvmfornfv.git / blobdiff