1 /*P:100 This is the Launcher code, a simple program which lays out the
2 * "physical" memory for the new Guest by mapping the kernel image and
3 * the virtual devices, then opens /dev/lguest to tell the kernel
4 * about the Guest and control it. :*/
5 #define _LARGEFILE64_SOURCE
15 #include <sys/param.h>
16 #include <sys/types.h>
19 #include <sys/eventfd.h>
24 #include <sys/socket.h>
25 #include <sys/ioctl.h>
28 #include <netinet/in.h>
30 #include <linux/sockios.h>
31 #include <linux/if_tun.h>
41 #include "linux/lguest_launcher.h"
42 #include "linux/virtio_config.h"
43 #include "linux/virtio_net.h"
44 #include "linux/virtio_blk.h"
45 #include "linux/virtio_console.h"
46 #include "linux/virtio_rng.h"
47 #include "linux/virtio_ring.h"
48 #include "asm/bootparam.h"
49 /*L:110 We can ignore the 39 include files we need for this program, but I do
50 * want to draw attention to the use of kernel-style types.
52 * As Linus said, "C is a Spartan language, and so should your naming be." I
53 * like these abbreviations, so we define them here. Note that u64 is always
54 * unsigned long long, which works on all Linux systems: this means that we can
55 * use %llu in printf for any u64. */
56 typedef unsigned long long u64;
62 #define PAGE_PRESENT 0x7 /* Present, RW, Execute */
63 #define BRIDGE_PFX "bridge:"
65 #define SIOCBRADDIF 0x89a2 /* add interface to bridge */
67 /* We can have up to 256 pages for devices. */
68 #define DEVICE_PAGES 256
69 /* This will occupy 3 pages: it must be a power of 2. */
70 #define VIRTQUEUE_NUM 256
72 /*L:120 verbose is both a global flag and a macro. The C preprocessor allows
73 * this, and although I wouldn't recommend it, it works quite nicely here. */
75 #define verbose(args...) \
76 do { if (verbose) printf(args); } while(0)
79 /* The pointer to the start of guest memory. */
80 static void *guest_base;
81 /* The maximum guest physical address allowed, and maximum possible. */
82 static unsigned long guest_limit, guest_max;
83 /* The /dev/lguest file descriptor. */
86 /* a per-cpu variable indicating whose vcpu is currently running */
87 static unsigned int __thread cpu_id;
89 /* This is our list of devices. */
92 /* Counter to assign interrupt numbers. */
93 unsigned int next_irq;
95 /* Counter to print out convenient device numbers. */
96 unsigned int device_num;
98 /* The descriptor page for the devices. */
101 /* A single linked list of devices. */
103 /* And a pointer to the last device for easy append and also for
104 * configuration appending. */
105 struct device *lastdev;
108 /* The list of Guest devices, based on command line arguments. */
109 static struct device_list devices;
111 /* The device structure describes a single device. */
114 /* The linked-list pointer. */
117 /* The device's descriptor, as mapped into the Guest. */
118 struct lguest_device_desc *desc;
120 /* We can't trust desc values once Guest has booted: we use these. */
121 unsigned int feature_len;
124 /* The name of this device, for --verbose. */
127 /* Any queues attached to this device */
128 struct virtqueue *vq;
130 /* Is it operational */
133 /* Device-specific data. */
137 /* The virtqueue structure describes a queue attached to a device. */
140 struct virtqueue *next;
142 /* Which device owns me. */
145 /* The configuration for this queue. */
146 struct lguest_vqconfig config;
148 /* The actual ring of buffers. */
151 /* Last available index we saw. */
154 /* Eventfd where Guest notifications arrive. */
157 /* Function for the thread which is servicing this virtqueue. */
158 void (*service)(struct virtqueue *vq);
162 /* Remember the arguments to the program so we can "reboot" */
163 static char **main_args;
165 /* The original tty settings to restore on exit. */
166 static struct termios orig_term;
168 /* We have to be careful with barriers: our devices are all run in separate
169 * threads and so we need to make sure that changes visible to the Guest happen
170 * in precise order. */
171 #define wmb() __asm__ __volatile__("" : : : "memory")
173 /* Convert an iovec element to the given type.
175 * This is a fairly ugly trick: we need to know the size of the type and
176 * alignment requirement to check the pointer is kosher. It's also nice to
177 * have the name of the type in case we report failure.
179 * Typing those three things all the time is cumbersome and error prone, so we
180 * have a macro which sets them all up and passes to the real function. */
181 #define convert(iov, type) \
182 ((type *)_convert((iov), sizeof(type), __alignof__(type), #type))
184 static void *_convert(struct iovec *iov, size_t size, size_t align,
187 if (iov->iov_len != size)
188 errx(1, "Bad iovec size %zu for %s", iov->iov_len, name);
189 if ((unsigned long)iov->iov_base % align != 0)
190 errx(1, "Bad alignment %p for %s", iov->iov_base, name);
191 return iov->iov_base;
194 /* Wrapper for the last available index. Makes it easier to change. */
195 #define lg_last_avail(vq) ((vq)->last_avail_idx)
197 /* The virtio configuration space is defined to be little-endian. x86 is
198 * little-endian too, but it's nice to be explicit so we have these helpers. */
199 #define cpu_to_le16(v16) (v16)
200 #define cpu_to_le32(v32) (v32)
201 #define cpu_to_le64(v64) (v64)
202 #define le16_to_cpu(v16) (v16)
203 #define le32_to_cpu(v32) (v32)
204 #define le64_to_cpu(v64) (v64)
206 /* Is this iovec empty? */
207 static bool iov_empty(const struct iovec iov[], unsigned int num_iov)
211 for (i = 0; i < num_iov; i++)
217 /* Take len bytes from the front of this iovec. */
218 static void iov_consume(struct iovec iov[], unsigned num_iov, unsigned len)
222 for (i = 0; i < num_iov; i++) {
225 used = iov[i].iov_len < len ? iov[i].iov_len : len;
226 iov[i].iov_base += used;
227 iov[i].iov_len -= used;
233 /* The device virtqueue descriptors are followed by feature bitmasks. */
234 static u8 *get_feature_bits(struct device *dev)
236 return (u8 *)(dev->desc + 1)
237 + dev->num_vq * sizeof(struct lguest_vqconfig);
240 /*L:100 The Launcher code itself takes us out into userspace, that scary place
241 * where pointers run wild and free! Unfortunately, like most userspace
242 * programs, it's quite boring (which is why everyone likes to hack on the
243 * kernel!). Perhaps if you make up an Lguest Drinking Game at this point, it
244 * will get you through this section. Or, maybe not.
246 * The Launcher sets up a big chunk of memory to be the Guest's "physical"
247 * memory and stores it in "guest_base". In other words, Guest physical ==
248 * Launcher virtual with an offset.
250 * This can be tough to get your head around, but usually it just means that we
251 * use these trivial conversion functions when the Guest gives us it's
252 * "physical" addresses: */
253 static void *from_guest_phys(unsigned long addr)
255 return guest_base + addr;
258 static unsigned long to_guest_phys(const void *addr)
260 return (addr - guest_base);
264 * Loading the Kernel.
266 * We start with couple of simple helper routines. open_or_die() avoids
267 * error-checking code cluttering the callers: */
268 static int open_or_die(const char *name, int flags)
270 int fd = open(name, flags);
272 err(1, "Failed to open %s", name);
276 /* map_zeroed_pages() takes a number of pages. */
277 static void *map_zeroed_pages(unsigned int num)
279 int fd = open_or_die("/dev/zero", O_RDONLY);
282 /* We use a private mapping (ie. if we write to the page, it will be
284 addr = mmap(NULL, getpagesize() * num,
285 PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0);
286 if (addr == MAP_FAILED)
287 err(1, "Mmaping %u pages of /dev/zero", num);
293 /* Get some more pages for a device. */
294 static void *get_pages(unsigned int num)
296 void *addr = from_guest_phys(guest_limit);
298 guest_limit += num * getpagesize();
299 if (guest_limit > guest_max)
300 errx(1, "Not enough memory for devices");
304 /* This routine is used to load the kernel or initrd. It tries mmap, but if
305 * that fails (Plan 9's kernel file isn't nicely aligned on page boundaries),
306 * it falls back to reading the memory in. */
307 static void map_at(int fd, void *addr, unsigned long offset, unsigned long len)
311 /* We map writable even though for some segments are marked read-only.
312 * The kernel really wants to be writable: it patches its own
315 * MAP_PRIVATE means that the page won't be copied until a write is
316 * done to it. This allows us to share untouched memory between
318 if (mmap(addr, len, PROT_READ|PROT_WRITE|PROT_EXEC,
319 MAP_FIXED|MAP_PRIVATE, fd, offset) != MAP_FAILED)
322 /* pread does a seek and a read in one shot: saves a few lines. */
323 r = pread(fd, addr, len, offset);
325 err(1, "Reading offset %lu len %lu gave %zi", offset, len, r);
328 /* This routine takes an open vmlinux image, which is in ELF, and maps it into
329 * the Guest memory. ELF = Embedded Linking Format, which is the format used
330 * by all modern binaries on Linux including the kernel.
332 * The ELF headers give *two* addresses: a physical address, and a virtual
333 * address. We use the physical address; the Guest will map itself to the
336 * We return the starting address. */
337 static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr)
339 Elf32_Phdr phdr[ehdr->e_phnum];
342 /* Sanity checks on the main ELF header: an x86 executable with a
343 * reasonable number of correctly-sized program headers. */
344 if (ehdr->e_type != ET_EXEC
345 || ehdr->e_machine != EM_386
346 || ehdr->e_phentsize != sizeof(Elf32_Phdr)
347 || ehdr->e_phnum < 1 || ehdr->e_phnum > 65536U/sizeof(Elf32_Phdr))
348 errx(1, "Malformed elf header");
350 /* An ELF executable contains an ELF header and a number of "program"
351 * headers which indicate which parts ("segments") of the program to
354 /* We read in all the program headers at once: */
355 if (lseek(elf_fd, ehdr->e_phoff, SEEK_SET) < 0)
356 err(1, "Seeking to program headers");
357 if (read(elf_fd, phdr, sizeof(phdr)) != sizeof(phdr))
358 err(1, "Reading program headers");
360 /* Try all the headers: there are usually only three. A read-only one,
361 * a read-write one, and a "note" section which we don't load. */
362 for (i = 0; i < ehdr->e_phnum; i++) {
363 /* If this isn't a loadable segment, we ignore it */
364 if (phdr[i].p_type != PT_LOAD)
367 verbose("Section %i: size %i addr %p\n",
368 i, phdr[i].p_memsz, (void *)phdr[i].p_paddr);
370 /* We map this section of the file at its physical address. */
371 map_at(elf_fd, from_guest_phys(phdr[i].p_paddr),
372 phdr[i].p_offset, phdr[i].p_filesz);
375 /* The entry point is given in the ELF header. */
376 return ehdr->e_entry;
379 /*L:150 A bzImage, unlike an ELF file, is not meant to be loaded. You're
380 * supposed to jump into it and it will unpack itself. We used to have to
381 * perform some hairy magic because the unpacking code scared me.
383 * Fortunately, Jeremy Fitzhardinge convinced me it wasn't that hard and wrote
384 * a small patch to jump over the tricky bits in the Guest, so now we just read
385 * the funky header so we know where in the file to load, and away we go! */
386 static unsigned long load_bzimage(int fd)
388 struct boot_params boot;
390 /* Modern bzImages get loaded at 1M. */
391 void *p = from_guest_phys(0x100000);
393 /* Go back to the start of the file and read the header. It should be
394 * a Linux boot header (see Documentation/x86/i386/boot.txt) */
395 lseek(fd, 0, SEEK_SET);
396 read(fd, &boot, sizeof(boot));
398 /* Inside the setup_hdr, we expect the magic "HdrS" */
399 if (memcmp(&boot.hdr.header, "HdrS", 4) != 0)
400 errx(1, "This doesn't look like a bzImage to me");
402 /* Skip over the extra sectors of the header. */
403 lseek(fd, (boot.hdr.setup_sects+1) * 512, SEEK_SET);
405 /* Now read everything into memory. in nice big chunks. */
406 while ((r = read(fd, p, 65536)) > 0)
409 /* Finally, code32_start tells us where to enter the kernel. */
410 return boot.hdr.code32_start;
413 /*L:140 Loading the kernel is easy when it's a "vmlinux", but most kernels
414 * come wrapped up in the self-decompressing "bzImage" format. With a little
415 * work, we can load those, too. */
416 static unsigned long load_kernel(int fd)
420 /* Read in the first few bytes. */
421 if (read(fd, &hdr, sizeof(hdr)) != sizeof(hdr))
422 err(1, "Reading kernel");
424 /* If it's an ELF file, it starts with "\177ELF" */
425 if (memcmp(hdr.e_ident, ELFMAG, SELFMAG) == 0)
426 return map_elf(fd, &hdr);
428 /* Otherwise we assume it's a bzImage, and try to load it. */
429 return load_bzimage(fd);
432 /* This is a trivial little helper to align pages. Andi Kleen hated it because
433 * it calls getpagesize() twice: "it's dumb code."
435 * Kernel guys get really het up about optimization, even when it's not
436 * necessary. I leave this code as a reaction against that. */
437 static inline unsigned long page_align(unsigned long addr)
439 /* Add upwards and truncate downwards. */
440 return ((addr + getpagesize()-1) & ~(getpagesize()-1));
443 /*L:180 An "initial ram disk" is a disk image loaded into memory along with
444 * the kernel which the kernel can use to boot from without needing any
445 * drivers. Most distributions now use this as standard: the initrd contains
446 * the code to load the appropriate driver modules for the current machine.
448 * Importantly, James Morris works for RedHat, and Fedora uses initrds for its
449 * kernels. He sent me this (and tells me when I break it). */
450 static unsigned long load_initrd(const char *name, unsigned long mem)
456 ifd = open_or_die(name, O_RDONLY);
457 /* fstat() is needed to get the file size. */
458 if (fstat(ifd, &st) < 0)
459 err(1, "fstat() on initrd '%s'", name);
461 /* We map the initrd at the top of memory, but mmap wants it to be
462 * page-aligned, so we round the size up for that. */
463 len = page_align(st.st_size);
464 map_at(ifd, from_guest_phys(mem - len), 0, st.st_size);
465 /* Once a file is mapped, you can close the file descriptor. It's a
466 * little odd, but quite useful. */
468 verbose("mapped initrd %s size=%lu @ %p\n", name, len, (void*)mem-len);
470 /* We return the initrd size. */
475 /* Simple routine to roll all the commandline arguments together with spaces
477 static void concat(char *dst, char *args[])
479 unsigned int i, len = 0;
481 for (i = 0; args[i]; i++) {
483 strcat(dst+len, " ");
486 strcpy(dst+len, args[i]);
487 len += strlen(args[i]);
489 /* In case it's empty. */
493 /*L:185 This is where we actually tell the kernel to initialize the Guest. We
494 * saw the arguments it expects when we looked at initialize() in lguest_user.c:
495 * the base of Guest "physical" memory, the top physical page to allow and the
496 * entry point for the Guest. */
497 static void tell_kernel(unsigned long start)
499 unsigned long args[] = { LHREQ_INITIALIZE,
500 (unsigned long)guest_base,
501 guest_limit / getpagesize(), start };
502 verbose("Guest: %p - %p (%#lx)\n",
503 guest_base, guest_base + guest_limit, guest_limit);
504 lguest_fd = open_or_die("/dev/lguest", O_RDWR);
505 if (write(lguest_fd, args, sizeof(args)) < 0)
506 err(1, "Writing to /dev/lguest");
513 * When the Guest gives us a buffer, it sends an array of addresses and sizes.
514 * We need to make sure it's not trying to reach into the Launcher itself, so
515 * we have a convenient routine which checks it and exits with an error message
516 * if something funny is going on:
518 static void *_check_pointer(unsigned long addr, unsigned int size,
521 /* We have to separately check addr and addr+size, because size could
522 * be huge and addr + size might wrap around. */
523 if (addr >= guest_limit || addr + size >= guest_limit)
524 errx(1, "%s:%i: Invalid address %#lx", __FILE__, line, addr);
525 /* We return a pointer for the caller's convenience, now we know it's
527 return from_guest_phys(addr);
529 /* A macro which transparently hands the line number to the real function. */
530 #define check_pointer(addr,size) _check_pointer(addr, size, __LINE__)
532 /* Each buffer in the virtqueues is actually a chain of descriptors. This
533 * function returns the next descriptor in the chain, or vq->vring.num if we're
535 static unsigned next_desc(struct virtqueue *vq, unsigned int i)
539 /* If this descriptor says it doesn't chain, we're done. */
540 if (!(vq->vring.desc[i].flags & VRING_DESC_F_NEXT))
541 return vq->vring.num;
543 /* Check they're not leading us off end of descriptors. */
544 next = vq->vring.desc[i].next;
545 /* Make sure compiler knows to grab that: we don't want it changing! */
548 if (next >= vq->vring.num)
549 errx(1, "Desc next is %u", next);
554 /* This looks in the virtqueue and for the first available buffer, and converts
555 * it to an iovec for convenient access. Since descriptors consist of some
556 * number of output then some number of input descriptors, it's actually two
557 * iovecs, but we pack them into one and note how many of each there were.
559 * This function returns the descriptor number found. */
560 static unsigned wait_for_vq_desc(struct virtqueue *vq,
562 unsigned int *out_num, unsigned int *in_num)
564 unsigned int i, head;
565 u16 last_avail = lg_last_avail(vq);
567 while (last_avail == vq->vring.avail->idx) {
570 /* Nothing new? Wait for eventfd to tell us they refilled. */
571 if (read(vq->eventfd, &event, sizeof(event)) != sizeof(event))
572 errx(1, "Event read failed?");
575 /* Check it isn't doing very strange things with descriptor numbers. */
576 if ((u16)(vq->vring.avail->idx - last_avail) > vq->vring.num)
577 errx(1, "Guest moved used index from %u to %u",
578 last_avail, vq->vring.avail->idx);
580 /* Grab the next descriptor number they're advertising, and increment
581 * the index we've seen. */
582 head = vq->vring.avail->ring[last_avail % vq->vring.num];
585 /* If their number is silly, that's a fatal mistake. */
586 if (head >= vq->vring.num)
587 errx(1, "Guest says index %u is available", head);
589 /* When we start there are none of either input nor output. */
590 *out_num = *in_num = 0;
594 /* Grab the first descriptor, and check it's OK. */
595 iov[*out_num + *in_num].iov_len = vq->vring.desc[i].len;
596 iov[*out_num + *in_num].iov_base
597 = check_pointer(vq->vring.desc[i].addr,
598 vq->vring.desc[i].len);
599 /* If this is an input descriptor, increment that count. */
600 if (vq->vring.desc[i].flags & VRING_DESC_F_WRITE)
603 /* If it's an output descriptor, they're all supposed
604 * to come before any input descriptors. */
606 errx(1, "Descriptor has out after in");
610 /* If we've got too many, that implies a descriptor loop. */
611 if (*out_num + *in_num > vq->vring.num)
612 errx(1, "Looped descriptor");
613 } while ((i = next_desc(vq, i)) != vq->vring.num);
618 /* After we've used one of their buffers, we tell them about it. We'll then
619 * want to send them an interrupt, using trigger_irq(). */
620 static void add_used(struct virtqueue *vq, unsigned int head, int len)
622 struct vring_used_elem *used;
624 /* The virtqueue contains a ring of used buffers. Get a pointer to the
625 * next entry in that used ring. */
626 used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num];
629 /* Make sure buffer is written before we update index. */
631 vq->vring.used->idx++;
634 /* This actually sends the interrupt for this virtqueue */
635 static void trigger_irq(struct virtqueue *vq)
637 unsigned long buf[] = { LHREQ_IRQ, vq->config.irq };
639 /* If they don't want an interrupt, don't send one, unless empty. */
640 if ((vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
641 && lg_last_avail(vq) != vq->vring.avail->idx)
644 /* Send the Guest an interrupt tell them we used something up. */
645 if (write(lguest_fd, buf, sizeof(buf)) != 0)
646 err(1, "Triggering irq %i", vq->config.irq);
649 /* And here's the combo meal deal. Supersize me! */
650 static void add_used_and_trigger(struct virtqueue *vq, unsigned head, int len)
652 add_used(vq, head, len);
659 * We associate some data with the console for our exit hack. */
662 /* How many times have they hit ^C? */
664 /* When did they start? */
665 struct timeval start;
668 /* This is the routine which handles console input (ie. stdin). */
669 static void console_input(struct virtqueue *vq)
672 unsigned int head, in_num, out_num;
673 struct console_abort *abort = vq->dev->priv;
674 struct iovec iov[vq->vring.num];
676 /* Make sure there's a descriptor waiting. */
677 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
679 errx(1, "Output buffers in console in queue?");
682 len = readv(STDIN_FILENO, iov, in_num);
684 /* Ran out of input? */
685 warnx("Failed to get console input, ignoring console.");
686 /* For simplicity, dying threads kill the whole Launcher. So
692 add_used_and_trigger(vq, head, len);
694 /* Three ^C within one second? Exit.
696 * This is such a hack, but works surprisingly well. Each ^C has to
697 * be in a buffer by itself, so they can't be too fast. But we check
698 * that we get three within about a second, so they can't be too
700 if (len != 1 || ((char *)iov[0].iov_base)[0] != 3) {
706 if (abort->count == 1)
707 gettimeofday(&abort->start, NULL);
708 else if (abort->count == 3) {
710 gettimeofday(&now, NULL);
711 /* Kill all Launcher processes with SIGINT, like normal ^C */
712 if (now.tv_sec <= abort->start.tv_sec+1)
718 /* This is the routine which handles console output (ie. stdout). */
719 static void console_output(struct virtqueue *vq)
721 unsigned int head, out, in;
722 struct iovec iov[vq->vring.num];
724 head = wait_for_vq_desc(vq, iov, &out, &in);
726 errx(1, "Input buffers in console output queue?");
727 while (!iov_empty(iov, out)) {
728 int len = writev(STDOUT_FILENO, iov, out);
730 err(1, "Write to stdout gave %i", len);
731 iov_consume(iov, out, len);
733 add_used_and_trigger(vq, head, 0);
739 * Handling output for network is also simple: we get all the output buffers
740 * and write them to /dev/net/tun.
746 static void net_output(struct virtqueue *vq)
748 struct net_info *net_info = vq->dev->priv;
749 unsigned int head, out, in;
750 struct iovec iov[vq->vring.num];
752 head = wait_for_vq_desc(vq, iov, &out, &in);
754 errx(1, "Input buffers in net output queue?");
755 if (writev(net_info->tunfd, iov, out) < 0)
756 errx(1, "Write to tun failed?");
757 add_used_and_trigger(vq, head, 0);
760 /* This is where we handle packets coming in from the tun device to our
762 static void net_input(struct virtqueue *vq)
765 unsigned int head, out, in;
766 struct iovec iov[vq->vring.num];
767 struct net_info *net_info = vq->dev->priv;
769 head = wait_for_vq_desc(vq, iov, &out, &in);
771 errx(1, "Output buffers in net input queue?");
772 len = readv(net_info->tunfd, iov, in);
774 err(1, "Failed to read from tun.");
775 add_used_and_trigger(vq, head, len);
778 /* This is the helper to create threads. */
779 static int do_thread(void *_vq)
781 struct virtqueue *vq = _vq;
788 /* When a child dies, we kill our entire process group with SIGTERM. This
789 * also has the side effect that the shell restores the console for us! */
790 static void kill_launcher(int signal)
795 static void reset_device(struct device *dev)
797 struct virtqueue *vq;
799 verbose("Resetting device %s\n", dev->name);
801 /* Clear any features they've acked. */
802 memset(get_feature_bits(dev) + dev->feature_len, 0, dev->feature_len);
804 /* We're going to be explicitly killing threads, so ignore them. */
805 signal(SIGCHLD, SIG_IGN);
807 /* Zero out the virtqueues, get rid of their threads */
808 for (vq = dev->vq; vq; vq = vq->next) {
809 if (vq->thread != (pid_t)-1) {
810 kill(vq->thread, SIGTERM);
811 waitpid(vq->thread, NULL, 0);
812 vq->thread = (pid_t)-1;
814 memset(vq->vring.desc, 0,
815 vring_size(vq->config.num, LGUEST_VRING_ALIGN));
816 lg_last_avail(vq) = 0;
818 dev->running = false;
820 /* Now we care if threads die. */
821 signal(SIGCHLD, (void *)kill_launcher);
824 static void create_thread(struct virtqueue *vq)
826 /* Create stack for thread and run it. Since stack grows
827 * upwards, we point the stack pointer to the end of this
829 char *stack = malloc(32768);
830 unsigned long args[] = { LHREQ_EVENTFD,
831 vq->config.pfn*getpagesize(), 0 };
833 /* Create a zero-initialized eventfd. */
834 vq->eventfd = eventfd(0, 0);
836 err(1, "Creating eventfd");
837 args[2] = vq->eventfd;
839 /* Attach an eventfd to this virtqueue: it will go off
840 * when the Guest does an LHCALL_NOTIFY for this vq. */
841 if (write(lguest_fd, &args, sizeof(args)) != 0)
842 err(1, "Attaching eventfd");
844 /* CLONE_VM: because it has to access the Guest memory, and
845 * SIGCHLD so we get a signal if it dies. */
846 vq->thread = clone(do_thread, stack + 32768, CLONE_VM | SIGCHLD, vq);
847 if (vq->thread == (pid_t)-1)
848 err(1, "Creating clone");
849 /* We close our local copy, now the child has it. */
853 static void start_device(struct device *dev)
856 struct virtqueue *vq;
858 verbose("Device %s OK: offered", dev->name);
859 for (i = 0; i < dev->feature_len; i++)
860 verbose(" %02x", get_feature_bits(dev)[i]);
861 verbose(", accepted");
862 for (i = 0; i < dev->feature_len; i++)
863 verbose(" %02x", get_feature_bits(dev)
864 [dev->feature_len+i]);
866 for (vq = dev->vq; vq; vq = vq->next) {
873 static void cleanup_devices(void)
877 for (dev = devices.dev; dev; dev = dev->next)
880 /* If we saved off the original terminal settings, restore them now. */
881 if (orig_term.c_lflag & (ISIG|ICANON|ECHO))
882 tcsetattr(STDIN_FILENO, TCSANOW, &orig_term);
885 /* When the Guest tells us they updated the status field, we handle it. */
886 static void update_device_status(struct device *dev)
888 /* A zero status is a reset, otherwise it's a set of flags. */
889 if (dev->desc->status == 0)
891 else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) {
892 warnx("Device %s configuration FAILED", dev->name);
895 } else if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK) {
901 /* This is the generic routine we call when the Guest uses LHCALL_NOTIFY. */
902 static void handle_output(unsigned long addr)
906 /* Check each device. */
907 for (i = devices.dev; i; i = i->next) {
908 struct virtqueue *vq;
910 /* Notifications to device descriptors update device status. */
911 if (from_guest_phys(addr) == i->desc) {
912 update_device_status(i);
916 /* Devices *can* be used before status is set to DRIVER_OK. */
917 for (vq = i->vq; vq; vq = vq->next) {
918 if (addr != vq->config.pfn*getpagesize())
921 errx(1, "Notification on running %s", i->name);
927 /* Early console write is done using notify on a nul-terminated string
928 * in Guest memory. */
929 if (addr >= guest_limit)
930 errx(1, "Bad NOTIFY %#lx", addr);
932 write(STDOUT_FILENO, from_guest_phys(addr),
933 strnlen(from_guest_phys(addr), guest_limit - addr));
939 * All devices need a descriptor so the Guest knows it exists, and a "struct
940 * device" so the Launcher can keep track of it. We have common helper
941 * routines to allocate and manage them.
944 /* The layout of the device page is a "struct lguest_device_desc" followed by a
945 * number of virtqueue descriptors, then two sets of feature bits, then an
946 * array of configuration bytes. This routine returns the configuration
948 static u8 *device_config(const struct device *dev)
950 return (void *)(dev->desc + 1)
951 + dev->num_vq * sizeof(struct lguest_vqconfig)
952 + dev->feature_len * 2;
955 /* This routine allocates a new "struct lguest_device_desc" from descriptor
956 * table page just above the Guest's normal memory. It returns a pointer to
957 * that descriptor. */
958 static struct lguest_device_desc *new_dev_desc(u16 type)
960 struct lguest_device_desc d = { .type = type };
963 /* Figure out where the next device config is, based on the last one. */
965 p = device_config(devices.lastdev)
966 + devices.lastdev->desc->config_len;
968 p = devices.descpage;
970 /* We only have one page for all the descriptors. */
971 if (p + sizeof(d) > (void *)devices.descpage + getpagesize())
972 errx(1, "Too many devices");
974 /* p might not be aligned, so we memcpy in. */
975 return memcpy(p, &d, sizeof(d));
978 /* Each device descriptor is followed by the description of its virtqueues. We
979 * specify how many descriptors the virtqueue is to have. */
980 static void add_virtqueue(struct device *dev, unsigned int num_descs,
981 void (*service)(struct virtqueue *))
984 struct virtqueue **i, *vq = malloc(sizeof(*vq));
987 /* First we need some memory for this virtqueue. */
988 pages = (vring_size(num_descs, LGUEST_VRING_ALIGN) + getpagesize() - 1)
990 p = get_pages(pages);
992 /* Initialize the virtqueue */
994 vq->last_avail_idx = 0;
996 vq->service = service;
997 vq->thread = (pid_t)-1;
999 /* Initialize the configuration. */
1000 vq->config.num = num_descs;
1001 vq->config.irq = devices.next_irq++;
1002 vq->config.pfn = to_guest_phys(p) / getpagesize();
1004 /* Initialize the vring. */
1005 vring_init(&vq->vring, num_descs, p, LGUEST_VRING_ALIGN);
1007 /* Append virtqueue to this device's descriptor. We use
1008 * device_config() to get the end of the device's current virtqueues;
1009 * we check that we haven't added any config or feature information
1010 * yet, otherwise we'd be overwriting them. */
1011 assert(dev->desc->config_len == 0 && dev->desc->feature_len == 0);
1012 memcpy(device_config(dev), &vq->config, sizeof(vq->config));
1014 dev->desc->num_vq++;
1016 verbose("Virtqueue page %#lx\n", to_guest_phys(p));
1018 /* Add to tail of list, so dev->vq is first vq, dev->vq->next is
1020 for (i = &dev->vq; *i; i = &(*i)->next);
1024 /* The first half of the feature bitmask is for us to advertise features. The
1025 * second half is for the Guest to accept features. */
1026 static void add_feature(struct device *dev, unsigned bit)
1028 u8 *features = get_feature_bits(dev);
1030 /* We can't extend the feature bits once we've added config bytes */
1031 if (dev->desc->feature_len <= bit / CHAR_BIT) {
1032 assert(dev->desc->config_len == 0);
1033 dev->feature_len = dev->desc->feature_len = (bit/CHAR_BIT) + 1;
1036 features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT));
1039 /* This routine sets the configuration fields for an existing device's
1040 * descriptor. It only works for the last device, but that's OK because that's
1042 static void set_config(struct device *dev, unsigned len, const void *conf)
1044 /* Check we haven't overflowed our single page. */
1045 if (device_config(dev) + len > devices.descpage + getpagesize())
1046 errx(1, "Too many devices");
1048 /* Copy in the config information, and store the length. */
1049 memcpy(device_config(dev), conf, len);
1050 dev->desc->config_len = len;
1053 /* This routine does all the creation and setup of a new device, including
1054 * calling new_dev_desc() to allocate the descriptor and device memory.
1056 * See what I mean about userspace being boring? */
1057 static struct device *new_device(const char *name, u16 type)
1059 struct device *dev = malloc(sizeof(*dev));
1061 /* Now we populate the fields one at a time. */
1062 dev->desc = new_dev_desc(type);
1065 dev->feature_len = 0;
1067 dev->running = false;
1069 /* Append to device list. Prepending to a single-linked list is
1070 * easier, but the user expects the devices to be arranged on the bus
1071 * in command-line order. The first network device on the command line
1072 * is eth0, the first block device /dev/vda, etc. */
1073 if (devices.lastdev)
1074 devices.lastdev->next = dev;
1077 devices.lastdev = dev;
1082 /* Our first setup routine is the console. It's a fairly simple device, but
1083 * UNIX tty handling makes it uglier than it could be. */
1084 static void setup_console(void)
1088 /* If we can save the initial standard input settings... */
1089 if (tcgetattr(STDIN_FILENO, &orig_term) == 0) {
1090 struct termios term = orig_term;
1091 /* Then we turn off echo, line buffering and ^C etc. We want a
1092 * raw input stream to the Guest. */
1093 term.c_lflag &= ~(ISIG|ICANON|ECHO);
1094 tcsetattr(STDIN_FILENO, TCSANOW, &term);
1097 dev = new_device("console", VIRTIO_ID_CONSOLE);
1099 /* We store the console state in dev->priv, and initialize it. */
1100 dev->priv = malloc(sizeof(struct console_abort));
1101 ((struct console_abort *)dev->priv)->count = 0;
1103 /* The console needs two virtqueues: the input then the output. When
1104 * they put something the input queue, we make sure we're listening to
1105 * stdin. When they put something in the output queue, we write it to
1107 add_virtqueue(dev, VIRTQUEUE_NUM, console_input);
1108 add_virtqueue(dev, VIRTQUEUE_NUM, console_output);
1110 verbose("device %u: console\n", ++devices.device_num);
1114 /*M:010 Inter-guest networking is an interesting area. Simplest is to have a
1115 * --sharenet=<name> option which opens or creates a named pipe. This can be
1116 * used to send packets to another guest in a 1:1 manner.
1118 * More sopisticated is to use one of the tools developed for project like UML
1121 * Faster is to do virtio bonding in kernel. Doing this 1:1 would be
1122 * completely generic ("here's my vring, attach to your vring") and would work
1123 * for any traffic. Of course, namespace and permissions issues need to be
1124 * dealt with. A more sophisticated "multi-channel" virtio_net.c could hide
1125 * multiple inter-guest channels behind one interface, although it would
1126 * require some manner of hotplugging new virtio channels.
1128 * Finally, we could implement a virtio network switch in the kernel. :*/
1130 static u32 str2ip(const char *ipaddr)
1134 if (sscanf(ipaddr, "%u.%u.%u.%u", &b[0], &b[1], &b[2], &b[3]) != 4)
1135 errx(1, "Failed to parse IP address '%s'", ipaddr);
1136 return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3];
1139 static void str2mac(const char *macaddr, unsigned char mac[6])
1142 if (sscanf(macaddr, "%02x:%02x:%02x:%02x:%02x:%02x",
1143 &m[0], &m[1], &m[2], &m[3], &m[4], &m[5]) != 6)
1144 errx(1, "Failed to parse mac address '%s'", macaddr);
1153 /* This code is "adapted" from libbridge: it attaches the Host end of the
1154 * network device to the bridge device specified by the command line.
1156 * This is yet another James Morris contribution (I'm an IP-level guy, so I
1157 * dislike bridging), and I just try not to break it. */
1158 static void add_to_bridge(int fd, const char *if_name, const char *br_name)
1164 errx(1, "must specify bridge name");
1166 ifidx = if_nametoindex(if_name);
1168 errx(1, "interface %s does not exist!", if_name);
1170 strncpy(ifr.ifr_name, br_name, IFNAMSIZ);
1171 ifr.ifr_name[IFNAMSIZ-1] = '\0';
1172 ifr.ifr_ifindex = ifidx;
1173 if (ioctl(fd, SIOCBRADDIF, &ifr) < 0)
1174 err(1, "can't add %s to bridge %s", if_name, br_name);
1177 /* This sets up the Host end of the network device with an IP address, brings
1178 * it up so packets will flow, the copies the MAC address into the hwaddr
1180 static void configure_device(int fd, const char *tapif, u32 ipaddr)
1183 struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr;
1185 memset(&ifr, 0, sizeof(ifr));
1186 strcpy(ifr.ifr_name, tapif);
1188 /* Don't read these incantations. Just cut & paste them like I did! */
1189 sin->sin_family = AF_INET;
1190 sin->sin_addr.s_addr = htonl(ipaddr);
1191 if (ioctl(fd, SIOCSIFADDR, &ifr) != 0)
1192 err(1, "Setting %s interface address", tapif);
1193 ifr.ifr_flags = IFF_UP;
1194 if (ioctl(fd, SIOCSIFFLAGS, &ifr) != 0)
1195 err(1, "Bringing interface %s up", tapif);
1198 static int get_tun_device(char tapif[IFNAMSIZ])
1203 /* Start with this zeroed. Messy but sure. */
1204 memset(&ifr, 0, sizeof(ifr));
1206 /* We open the /dev/net/tun device and tell it we want a tap device. A
1207 * tap device is like a tun device, only somehow different. To tell
1208 * the truth, I completely blundered my way through this code, but it
1210 netfd = open_or_die("/dev/net/tun", O_RDWR);
1211 ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
1212 strcpy(ifr.ifr_name, "tap%d");
1213 if (ioctl(netfd, TUNSETIFF, &ifr) != 0)
1214 err(1, "configuring /dev/net/tun");
1216 if (ioctl(netfd, TUNSETOFFLOAD,
1217 TUN_F_CSUM|TUN_F_TSO4|TUN_F_TSO6|TUN_F_TSO_ECN) != 0)
1218 err(1, "Could not set features for tun device");
1220 /* We don't need checksums calculated for packets coming in this
1221 * device: trust us! */
1222 ioctl(netfd, TUNSETNOCSUM, 1);
1224 memcpy(tapif, ifr.ifr_name, IFNAMSIZ);
1228 /*L:195 Our network is a Host<->Guest network. This can either use bridging or
1229 * routing, but the principle is the same: it uses the "tun" device to inject
1230 * packets into the Host as if they came in from a normal network card. We
1231 * just shunt packets between the Guest and the tun device. */
1232 static void setup_tun_net(char *arg)
1235 struct net_info *net_info = malloc(sizeof(*net_info));
1237 u32 ip = INADDR_ANY;
1238 bool bridging = false;
1239 char tapif[IFNAMSIZ], *p;
1240 struct virtio_net_config conf;
1242 net_info->tunfd = get_tun_device(tapif);
1244 /* First we create a new network device. */
1245 dev = new_device("net", VIRTIO_ID_NET);
1246 dev->priv = net_info;
1248 /* Network devices need a receive and a send queue, just like
1250 add_virtqueue(dev, VIRTQUEUE_NUM, net_input);
1251 add_virtqueue(dev, VIRTQUEUE_NUM, net_output);
1253 /* We need a socket to perform the magic network ioctls to bring up the
1254 * tap interface, connect to the bridge etc. Any socket will do! */
1255 ipfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
1257 err(1, "opening IP socket");
1259 /* If the command line was --tunnet=bridge:<name> do bridging. */
1260 if (!strncmp(BRIDGE_PFX, arg, strlen(BRIDGE_PFX))) {
1261 arg += strlen(BRIDGE_PFX);
1265 /* A mac address may follow the bridge name or IP address */
1266 p = strchr(arg, ':');
1268 str2mac(p+1, conf.mac);
1269 add_feature(dev, VIRTIO_NET_F_MAC);
1273 /* arg is now either an IP address or a bridge name */
1275 add_to_bridge(ipfd, tapif, arg);
1279 /* Set up the tun device. */
1280 configure_device(ipfd, tapif, ip);
1282 add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
1283 /* Expect Guest to handle everything except UFO */
1284 add_feature(dev, VIRTIO_NET_F_CSUM);
1285 add_feature(dev, VIRTIO_NET_F_GUEST_CSUM);
1286 add_feature(dev, VIRTIO_NET_F_GUEST_TSO4);
1287 add_feature(dev, VIRTIO_NET_F_GUEST_TSO6);
1288 add_feature(dev, VIRTIO_NET_F_GUEST_ECN);
1289 add_feature(dev, VIRTIO_NET_F_HOST_TSO4);
1290 add_feature(dev, VIRTIO_NET_F_HOST_TSO6);
1291 add_feature(dev, VIRTIO_NET_F_HOST_ECN);
1292 set_config(dev, sizeof(conf), &conf);
1294 /* We don't need the socket any more; setup is done. */
1297 devices.device_num++;
1300 verbose("device %u: tun %s attached to bridge: %s\n",
1301 devices.device_num, tapif, arg);
1303 verbose("device %u: tun %s: %s\n",
1304 devices.device_num, tapif, arg);
1307 /* Our block (disk) device should be really simple: the Guest asks for a block
1308 * number and we read or write that position in the file. Unfortunately, that
1309 * was amazingly slow: the Guest waits until the read is finished before
1310 * running anything else, even if it could have been doing useful work.
1312 * We could use async I/O, except it's reputed to suck so hard that characters
1313 * actually go missing from your code when you try to use it.
1315 * So we farm the I/O out to thread, and communicate with it via a pipe. */
1317 /* This hangs off device->priv. */
1320 /* The size of the file. */
1323 /* The file descriptor for the file. */
1326 /* IO thread listens on this file descriptor [0]. */
1329 /* IO thread writes to this file descriptor to mark it done, then
1330 * Launcher triggers interrupt to Guest. */
1337 * Remember that the block device is handled by a separate I/O thread. We head
1338 * straight into the core of that thread here:
1340 static void blk_request(struct virtqueue *vq)
1342 struct vblk_info *vblk = vq->dev->priv;
1343 unsigned int head, out_num, in_num, wlen;
1346 struct virtio_blk_outhdr *out;
1347 struct iovec iov[vq->vring.num];
1350 /* Get the next request. */
1351 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
1353 /* Every block request should contain at least one output buffer
1354 * (detailing the location on disk and the type of request) and one
1355 * input buffer (to hold the result). */
1356 if (out_num == 0 || in_num == 0)
1357 errx(1, "Bad virtblk cmd %u out=%u in=%u",
1358 head, out_num, in_num);
1360 out = convert(&iov[0], struct virtio_blk_outhdr);
1361 in = convert(&iov[out_num+in_num-1], u8);
1362 off = out->sector * 512;
1364 /* The block device implements "barriers", where the Guest indicates
1365 * that it wants all previous writes to occur before this write. We
1366 * don't have a way of asking our kernel to do a barrier, so we just
1367 * synchronize all the data in the file. Pretty poor, no? */
1368 if (out->type & VIRTIO_BLK_T_BARRIER)
1369 fdatasync(vblk->fd);
1371 /* In general the virtio block driver is allowed to try SCSI commands.
1372 * It'd be nice if we supported eject, for example, but we don't. */
1373 if (out->type & VIRTIO_BLK_T_SCSI_CMD) {
1374 fprintf(stderr, "Scsi commands unsupported\n");
1375 *in = VIRTIO_BLK_S_UNSUPP;
1377 } else if (out->type & VIRTIO_BLK_T_OUT) {
1380 /* Move to the right location in the block file. This can fail
1381 * if they try to write past end. */
1382 if (lseek64(vblk->fd, off, SEEK_SET) != off)
1383 err(1, "Bad seek to sector %llu", out->sector);
1385 ret = writev(vblk->fd, iov+1, out_num-1);
1386 verbose("WRITE to sector %llu: %i\n", out->sector, ret);
1388 /* Grr... Now we know how long the descriptor they sent was, we
1389 * make sure they didn't try to write over the end of the block
1390 * file (possibly extending it). */
1391 if (ret > 0 && off + ret > vblk->len) {
1392 /* Trim it back to the correct length */
1393 ftruncate64(vblk->fd, vblk->len);
1394 /* Die, bad Guest, die. */
1395 errx(1, "Write past end %llu+%u", off, ret);
1398 *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR);
1402 /* Move to the right location in the block file. This can fail
1403 * if they try to read past end. */
1404 if (lseek64(vblk->fd, off, SEEK_SET) != off)
1405 err(1, "Bad seek to sector %llu", out->sector);
1407 ret = readv(vblk->fd, iov+1, in_num-1);
1408 verbose("READ from sector %llu: %i\n", out->sector, ret);
1410 wlen = sizeof(*in) + ret;
1411 *in = VIRTIO_BLK_S_OK;
1414 *in = VIRTIO_BLK_S_IOERR;
1418 /* OK, so we noted that it was pretty poor to use an fdatasync as a
1419 * barrier. But Christoph Hellwig points out that we need a sync
1420 * *afterwards* as well: "Barriers specify no reordering to the front
1421 * or the back." And Jens Axboe confirmed it, so here we are: */
1422 if (out->type & VIRTIO_BLK_T_BARRIER)
1423 fdatasync(vblk->fd);
1425 add_used_and_trigger(vq, head, wlen);
1428 /*L:198 This actually sets up a virtual block device. */
1429 static void setup_block_file(const char *filename)
1432 struct vblk_info *vblk;
1433 struct virtio_blk_config conf;
1435 /* The device responds to return from I/O thread. */
1436 dev = new_device("block", VIRTIO_ID_BLOCK);
1438 /* The device has one virtqueue, where the Guest places requests. */
1439 add_virtqueue(dev, VIRTQUEUE_NUM, blk_request);
1441 /* Allocate the room for our own bookkeeping */
1442 vblk = dev->priv = malloc(sizeof(*vblk));
1444 /* First we open the file and store the length. */
1445 vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE);
1446 vblk->len = lseek64(vblk->fd, 0, SEEK_END);
1448 /* We support barriers. */
1449 add_feature(dev, VIRTIO_BLK_F_BARRIER);
1451 /* Tell Guest how many sectors this device has. */
1452 conf.capacity = cpu_to_le64(vblk->len / 512);
1454 /* Tell Guest not to put in too many descriptors at once: two are used
1455 * for the in and out elements. */
1456 add_feature(dev, VIRTIO_BLK_F_SEG_MAX);
1457 conf.seg_max = cpu_to_le32(VIRTQUEUE_NUM - 2);
1459 set_config(dev, sizeof(conf), &conf);
1461 verbose("device %u: virtblock %llu sectors\n",
1462 ++devices.device_num, le64_to_cpu(conf.capacity));
1469 /* Our random number generator device reads from /dev/random into the Guest's
1470 * input buffers. The usual case is that the Guest doesn't want random numbers
1471 * and so has no buffers although /dev/random is still readable, whereas
1472 * console is the reverse.
1474 * The same logic applies, however. */
1475 static void rng_input(struct virtqueue *vq)
1478 unsigned int head, in_num, out_num, totlen = 0;
1479 struct rng_info *rng_info = vq->dev->priv;
1480 struct iovec iov[vq->vring.num];
1482 /* First we need a buffer from the Guests's virtqueue. */
1483 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
1485 errx(1, "Output buffers in rng?");
1487 /* This is why we convert to iovecs: the readv() call uses them, and so
1488 * it reads straight into the Guest's buffer. We loop to make sure we
1490 while (!iov_empty(iov, in_num)) {
1491 len = readv(rng_info->rfd, iov, in_num);
1493 err(1, "Read from /dev/random gave %i", len);
1494 iov_consume(iov, in_num, len);
1498 /* Tell the Guest about the new input. */
1499 add_used_and_trigger(vq, head, totlen);
1502 /* And this creates a "hardware" random number device for the Guest. */
1503 static void setup_rng(void)
1506 struct rng_info *rng_info = malloc(sizeof(*rng_info));
1508 rng_info->rfd = open_or_die("/dev/random", O_RDONLY);
1510 /* The device responds to return from I/O thread. */
1511 dev = new_device("rng", VIRTIO_ID_RNG);
1512 dev->priv = rng_info;
1514 /* The device has one virtqueue, where the Guest places inbufs. */
1515 add_virtqueue(dev, VIRTQUEUE_NUM, rng_input);
1517 verbose("device %u: rng\n", devices.device_num++);
1519 /* That's the end of device setup. */
1521 /*L:230 Reboot is pretty easy: clean up and exec() the Launcher afresh. */
1522 static void __attribute__((noreturn)) restart_guest(void)
1526 /* Since we don't track all open fds, we simply close everything beyond
1528 for (i = 3; i < FD_SETSIZE; i++)
1531 /* Reset all the devices (kills all threads). */
1534 execv(main_args[0], main_args);
1535 err(1, "Could not exec %s", main_args[0]);
1538 /*L:220 Finally we reach the core of the Launcher which runs the Guest, serves
1539 * its input and output, and finally, lays it to rest. */
1540 static void __attribute__((noreturn)) run_guest(void)
1543 unsigned long notify_addr;
1546 /* We read from the /dev/lguest device to run the Guest. */
1547 readval = pread(lguest_fd, ¬ify_addr,
1548 sizeof(notify_addr), cpu_id);
1550 /* One unsigned long means the Guest did HCALL_NOTIFY */
1551 if (readval == sizeof(notify_addr)) {
1552 verbose("Notify on address %#lx\n", notify_addr);
1553 handle_output(notify_addr);
1554 /* ENOENT means the Guest died. Reading tells us why. */
1555 } else if (errno == ENOENT) {
1556 char reason[1024] = { 0 };
1557 pread(lguest_fd, reason, sizeof(reason)-1, cpu_id);
1558 errx(1, "%s", reason);
1559 /* ERESTART means that we need to reboot the guest */
1560 } else if (errno == ERESTART) {
1562 /* Anything else means a bug or incompatible change. */
1564 err(1, "Running guest failed");
1568 * This is the end of the Launcher. The good news: we are over halfway
1569 * through! The bad news: the most fiendish part of the code still lies ahead
1572 * Are you ready? Take a deep breath and join me in the core of the Host, in
1576 static struct option opts[] = {
1577 { "verbose", 0, NULL, 'v' },
1578 { "tunnet", 1, NULL, 't' },
1579 { "block", 1, NULL, 'b' },
1580 { "rng", 0, NULL, 'r' },
1581 { "initrd", 1, NULL, 'i' },
1584 static void usage(void)
1586 errx(1, "Usage: lguest [--verbose] "
1587 "[--tunnet=(<ipaddr>:<macaddr>|bridge:<bridgename>:<macaddr>)\n"
1588 "|--block=<filename>|--initrd=<filename>]...\n"
1589 "<mem-in-mb> vmlinux [args...]");
1592 /*L:105 The main routine is where the real work begins: */
1593 int main(int argc, char *argv[])
1595 /* Memory, top-level pagetable, code startpoint and size of the
1596 * (optional) initrd. */
1597 unsigned long mem = 0, start, initrd_size = 0;
1598 /* Two temporaries. */
1600 /* The boot information for the Guest. */
1601 struct boot_params *boot;
1602 /* If they specify an initrd file to load. */
1603 const char *initrd_name = NULL;
1605 /* Save the args: we "reboot" by execing ourselves again. */
1608 /* First we initialize the device list. We keep a pointer to the last
1609 * device, and the next interrupt number to use for devices (1:
1610 * remember that 0 is used by the timer). */
1611 devices.lastdev = NULL;
1612 devices.next_irq = 1;
1615 /* We need to know how much memory so we can set up the device
1616 * descriptor and memory pages for the devices as we parse the command
1617 * line. So we quickly look through the arguments to find the amount
1619 for (i = 1; i < argc; i++) {
1620 if (argv[i][0] != '-') {
1621 mem = atoi(argv[i]) * 1024 * 1024;
1622 /* We start by mapping anonymous pages over all of
1623 * guest-physical memory range. This fills it with 0,
1624 * and ensures that the Guest won't be killed when it
1625 * tries to access it. */
1626 guest_base = map_zeroed_pages(mem / getpagesize()
1629 guest_max = mem + DEVICE_PAGES*getpagesize();
1630 devices.descpage = get_pages(1);
1635 /* The options are fairly straight-forward */
1636 while ((c = getopt_long(argc, argv, "v", opts, NULL)) != EOF) {
1642 setup_tun_net(optarg);
1645 setup_block_file(optarg);
1651 initrd_name = optarg;
1654 warnx("Unknown argument %s", argv[optind]);
1658 /* After the other arguments we expect memory and kernel image name,
1659 * followed by command line arguments for the kernel. */
1660 if (optind + 2 > argc)
1663 verbose("Guest base is at %p\n", guest_base);
1665 /* We always have a console device */
1668 /* Now we load the kernel */
1669 start = load_kernel(open_or_die(argv[optind+1], O_RDONLY));
1671 /* Boot information is stashed at physical address 0 */
1672 boot = from_guest_phys(0);
1674 /* Map the initrd image if requested (at top of physical memory) */
1676 initrd_size = load_initrd(initrd_name, mem);
1677 /* These are the location in the Linux boot header where the
1678 * start and size of the initrd are expected to be found. */
1679 boot->hdr.ramdisk_image = mem - initrd_size;
1680 boot->hdr.ramdisk_size = initrd_size;
1681 /* The bootloader type 0xFF means "unknown"; that's OK. */
1682 boot->hdr.type_of_loader = 0xFF;
1685 /* The Linux boot header contains an "E820" memory map: ours is a
1686 * simple, single region. */
1687 boot->e820_entries = 1;
1688 boot->e820_map[0] = ((struct e820entry) { 0, mem, E820_RAM });
1689 /* The boot header contains a command line pointer: we put the command
1690 * line after the boot header. */
1691 boot->hdr.cmd_line_ptr = to_guest_phys(boot + 1);
1692 /* We use a simple helper to copy the arguments separated by spaces. */
1693 concat((char *)(boot + 1), argv+optind+2);
1695 /* Boot protocol version: 2.07 supports the fields for lguest. */
1696 boot->hdr.version = 0x207;
1698 /* The hardware_subarch value of "1" tells the Guest it's an lguest. */
1699 boot->hdr.hardware_subarch = 1;
1701 /* Tell the entry path not to try to reload segment registers. */
1702 boot->hdr.loadflags |= KEEP_SEGMENTS;
1704 /* We tell the kernel to initialize the Guest: this returns the open
1705 * /dev/lguest file descriptor. */
1708 /* Ensure that we terminate if a child dies. */
1709 signal(SIGCHLD, kill_launcher);
1711 /* If we exit via err(), this kills all the threads, restores tty. */
1712 atexit(cleanup_devices);
1714 /* Finally, run the Guest. This doesn't return. */
1720 * Mastery is done: you now know everything I do.
1722 * But surely you have seen code, features and bugs in your wanderings which
1723 * you now yearn to attack? That is the real game, and I look forward to you
1724 * patching and forking lguest into the Your-Name-Here-visor.
1726 * Farewell, and good coding!