2 * This is the Launcher code, a simple program which lays out the "physical"
3 * memory for the new Guest by mapping the kernel image and the virtual
4 * devices, then opens /dev/lguest to tell the kernel about the Guest and
7 #define _LARGEFILE64_SOURCE
17 #include <sys/param.h>
18 #include <sys/types.h>
21 #include <sys/eventfd.h>
26 #include <sys/socket.h>
27 #include <sys/ioctl.h>
30 #include <netinet/in.h>
32 #include <linux/sockios.h>
33 #include <linux/if_tun.h>
43 #include "linux/lguest_launcher.h"
44 #include "linux/virtio_config.h"
45 #include "linux/virtio_net.h"
46 #include "linux/virtio_blk.h"
47 #include "linux/virtio_console.h"
48 #include "linux/virtio_rng.h"
49 #include "linux/virtio_ring.h"
50 #include "asm/bootparam.h"
52 * We can ignore the 39 include files we need for this program, but I do want
53 * to draw attention to the use of kernel-style types.
55 * As Linus said, "C is a Spartan language, and so should your naming be." I
56 * like these abbreviations, so we define them here. Note that u64 is always
57 * unsigned long long, which works on all Linux systems: this means that we can
58 * use %llu in printf for any u64.
60 typedef unsigned long long u64;
66 #define PAGE_PRESENT 0x7 /* Present, RW, Execute */
67 #define BRIDGE_PFX "bridge:"
69 #define SIOCBRADDIF 0x89a2 /* add interface to bridge */
71 /* We can have up to 256 pages for devices. */
72 #define DEVICE_PAGES 256
73 /* This will occupy 3 pages: it must be a power of 2. */
74 #define VIRTQUEUE_NUM 256
77 * verbose is both a global flag and a macro. The C preprocessor allows
78 * this, and although I wouldn't recommend it, it works quite nicely here.
81 #define verbose(args...) \
82 do { if (verbose) printf(args); } while(0)
85 /* The pointer to the start of guest memory. */
86 static void *guest_base;
87 /* The maximum guest physical address allowed, and maximum possible. */
88 static unsigned long guest_limit, guest_max;
89 /* The /dev/lguest file descriptor. */
92 /* a per-cpu variable indicating whose vcpu is currently running */
93 static unsigned int __thread cpu_id;
95 /* This is our list of devices. */
98 /* Counter to assign interrupt numbers. */
99 unsigned int next_irq;
101 /* Counter to print out convenient device numbers. */
102 unsigned int device_num;
104 /* The descriptor page for the devices. */
107 /* A single linked list of devices. */
109 /* And a pointer to the last device for easy append. */
110 struct device *lastdev;
113 /* The list of Guest devices, based on command line arguments. */
114 static struct device_list devices;
116 /* The device structure describes a single device. */
119 /* The linked-list pointer. */
122 /* The device's descriptor, as mapped into the Guest. */
123 struct lguest_device_desc *desc;
125 /* We can't trust desc values once Guest has booted: we use these. */
126 unsigned int feature_len;
129 /* The name of this device, for --verbose. */
132 /* Any queues attached to this device */
133 struct virtqueue *vq;
135 /* Is it operational */
138 /* Device-specific data. */
142 /* The virtqueue structure describes a queue attached to a device. */
145 struct virtqueue *next;
147 /* Which device owns me. */
150 /* The configuration for this queue. */
151 struct lguest_vqconfig config;
153 /* The actual ring of buffers. */
156 /* Last available index we saw. */
159 /* How many are used since we sent last irq? */
160 unsigned int pending_used;
162 /* Eventfd where Guest notifications arrive. */
165 /* Function for the thread which is servicing this virtqueue. */
166 void (*service)(struct virtqueue *vq);
170 /* Remember the arguments to the program so we can "reboot" */
171 static char **main_args;
173 /* The original tty settings to restore on exit. */
174 static struct termios orig_term;
177 * We have to be careful with barriers: our devices are all run in separate
178 * threads and so we need to make sure that changes visible to the Guest happen
181 #define wmb() __asm__ __volatile__("" : : : "memory")
182 #define mb() __asm__ __volatile__("" : : : "memory")
185 * Convert an iovec element to the given type.
187 * This is a fairly ugly trick: we need to know the size of the type and
188 * alignment requirement to check the pointer is kosher. It's also nice to
189 * have the name of the type in case we report failure.
191 * Typing those three things all the time is cumbersome and error prone, so we
192 * have a macro which sets them all up and passes to the real function.
194 #define convert(iov, type) \
195 ((type *)_convert((iov), sizeof(type), __alignof__(type), #type))
197 static void *_convert(struct iovec *iov, size_t size, size_t align,
200 if (iov->iov_len != size)
201 errx(1, "Bad iovec size %zu for %s", iov->iov_len, name);
202 if ((unsigned long)iov->iov_base % align != 0)
203 errx(1, "Bad alignment %p for %s", iov->iov_base, name);
204 return iov->iov_base;
207 /* Wrapper for the last available index. Makes it easier to change. */
208 #define lg_last_avail(vq) ((vq)->last_avail_idx)
211 * The virtio configuration space is defined to be little-endian. x86 is
212 * little-endian too, but it's nice to be explicit so we have these helpers.
214 #define cpu_to_le16(v16) (v16)
215 #define cpu_to_le32(v32) (v32)
216 #define cpu_to_le64(v64) (v64)
217 #define le16_to_cpu(v16) (v16)
218 #define le32_to_cpu(v32) (v32)
219 #define le64_to_cpu(v64) (v64)
221 /* Is this iovec empty? */
222 static bool iov_empty(const struct iovec iov[], unsigned int num_iov)
226 for (i = 0; i < num_iov; i++)
232 /* Take len bytes from the front of this iovec. */
233 static void iov_consume(struct iovec iov[], unsigned num_iov, unsigned len)
237 for (i = 0; i < num_iov; i++) {
240 used = iov[i].iov_len < len ? iov[i].iov_len : len;
241 iov[i].iov_base += used;
242 iov[i].iov_len -= used;
248 /* The device virtqueue descriptors are followed by feature bitmasks. */
249 static u8 *get_feature_bits(struct device *dev)
251 return (u8 *)(dev->desc + 1)
252 + dev->num_vq * sizeof(struct lguest_vqconfig);
256 * The Launcher code itself takes us out into userspace, that scary place where
257 * pointers run wild and free! Unfortunately, like most userspace programs,
258 * it's quite boring (which is why everyone likes to hack on the kernel!).
259 * Perhaps if you make up an Lguest Drinking Game at this point, it will get
260 * you through this section. Or, maybe not.
262 * The Launcher sets up a big chunk of memory to be the Guest's "physical"
263 * memory and stores it in "guest_base". In other words, Guest physical ==
264 * Launcher virtual with an offset.
266 * This can be tough to get your head around, but usually it just means that we
267 * use these trivial conversion functions when the Guest gives us it's
268 * "physical" addresses:
270 static void *from_guest_phys(unsigned long addr)
272 return guest_base + addr;
275 static unsigned long to_guest_phys(const void *addr)
277 return (addr - guest_base);
281 * Loading the Kernel.
283 * We start with couple of simple helper routines. open_or_die() avoids
284 * error-checking code cluttering the callers:
286 static int open_or_die(const char *name, int flags)
288 int fd = open(name, flags);
290 err(1, "Failed to open %s", name);
294 /* map_zeroed_pages() takes a number of pages. */
295 static void *map_zeroed_pages(unsigned int num)
297 int fd = open_or_die("/dev/zero", O_RDONLY);
301 * We use a private mapping (ie. if we write to the page, it will be
304 addr = mmap(NULL, getpagesize() * num,
305 PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0);
306 if (addr == MAP_FAILED)
307 err(1, "Mmaping %u pages of /dev/zero", num);
313 /* Get some more pages for a device. */
314 static void *get_pages(unsigned int num)
316 void *addr = from_guest_phys(guest_limit);
318 guest_limit += num * getpagesize();
319 if (guest_limit > guest_max)
320 errx(1, "Not enough memory for devices");
325 * This routine is used to load the kernel or initrd. It tries mmap, but if
326 * that fails (Plan 9's kernel file isn't nicely aligned on page boundaries),
327 * it falls back to reading the memory in.
329 static void map_at(int fd, void *addr, unsigned long offset, unsigned long len)
334 * We map writable even though for some segments are marked read-only.
335 * The kernel really wants to be writable: it patches its own
338 * MAP_PRIVATE means that the page won't be copied until a write is
339 * done to it. This allows us to share untouched memory between
342 if (mmap(addr, len, PROT_READ|PROT_WRITE|PROT_EXEC,
343 MAP_FIXED|MAP_PRIVATE, fd, offset) != MAP_FAILED)
346 /* pread does a seek and a read in one shot: saves a few lines. */
347 r = pread(fd, addr, len, offset);
349 err(1, "Reading offset %lu len %lu gave %zi", offset, len, r);
353 * This routine takes an open vmlinux image, which is in ELF, and maps it into
354 * the Guest memory. ELF = Embedded Linking Format, which is the format used
355 * by all modern binaries on Linux including the kernel.
357 * The ELF headers give *two* addresses: a physical address, and a virtual
358 * address. We use the physical address; the Guest will map itself to the
361 * We return the starting address.
363 static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr)
365 Elf32_Phdr phdr[ehdr->e_phnum];
369 * Sanity checks on the main ELF header: an x86 executable with a
370 * reasonable number of correctly-sized program headers.
372 if (ehdr->e_type != ET_EXEC
373 || ehdr->e_machine != EM_386
374 || ehdr->e_phentsize != sizeof(Elf32_Phdr)
375 || ehdr->e_phnum < 1 || ehdr->e_phnum > 65536U/sizeof(Elf32_Phdr))
376 errx(1, "Malformed elf header");
379 * An ELF executable contains an ELF header and a number of "program"
380 * headers which indicate which parts ("segments") of the program to
384 /* We read in all the program headers at once: */
385 if (lseek(elf_fd, ehdr->e_phoff, SEEK_SET) < 0)
386 err(1, "Seeking to program headers");
387 if (read(elf_fd, phdr, sizeof(phdr)) != sizeof(phdr))
388 err(1, "Reading program headers");
391 * Try all the headers: there are usually only three. A read-only one,
392 * a read-write one, and a "note" section which we don't load.
394 for (i = 0; i < ehdr->e_phnum; i++) {
395 /* If this isn't a loadable segment, we ignore it */
396 if (phdr[i].p_type != PT_LOAD)
399 verbose("Section %i: size %i addr %p\n",
400 i, phdr[i].p_memsz, (void *)phdr[i].p_paddr);
402 /* We map this section of the file at its physical address. */
403 map_at(elf_fd, from_guest_phys(phdr[i].p_paddr),
404 phdr[i].p_offset, phdr[i].p_filesz);
407 /* The entry point is given in the ELF header. */
408 return ehdr->e_entry;
412 * A bzImage, unlike an ELF file, is not meant to be loaded. You're supposed
413 * to jump into it and it will unpack itself. We used to have to perform some
414 * hairy magic because the unpacking code scared me.
416 * Fortunately, Jeremy Fitzhardinge convinced me it wasn't that hard and wrote
417 * a small patch to jump over the tricky bits in the Guest, so now we just read
418 * the funky header so we know where in the file to load, and away we go!
420 static unsigned long load_bzimage(int fd)
422 struct boot_params boot;
424 /* Modern bzImages get loaded at 1M. */
425 void *p = from_guest_phys(0x100000);
428 * Go back to the start of the file and read the header. It should be
429 * a Linux boot header (see Documentation/x86/i386/boot.txt)
431 lseek(fd, 0, SEEK_SET);
432 read(fd, &boot, sizeof(boot));
434 /* Inside the setup_hdr, we expect the magic "HdrS" */
435 if (memcmp(&boot.hdr.header, "HdrS", 4) != 0)
436 errx(1, "This doesn't look like a bzImage to me");
438 /* Skip over the extra sectors of the header. */
439 lseek(fd, (boot.hdr.setup_sects+1) * 512, SEEK_SET);
441 /* Now read everything into memory. in nice big chunks. */
442 while ((r = read(fd, p, 65536)) > 0)
445 /* Finally, code32_start tells us where to enter the kernel. */
446 return boot.hdr.code32_start;
450 * Loading the kernel is easy when it's a "vmlinux", but most kernels
451 * come wrapped up in the self-decompressing "bzImage" format. With a little
452 * work, we can load those, too.
454 static unsigned long load_kernel(int fd)
458 /* Read in the first few bytes. */
459 if (read(fd, &hdr, sizeof(hdr)) != sizeof(hdr))
460 err(1, "Reading kernel");
462 /* If it's an ELF file, it starts with "\177ELF" */
463 if (memcmp(hdr.e_ident, ELFMAG, SELFMAG) == 0)
464 return map_elf(fd, &hdr);
466 /* Otherwise we assume it's a bzImage, and try to load it. */
467 return load_bzimage(fd);
471 * This is a trivial little helper to align pages. Andi Kleen hated it because
472 * it calls getpagesize() twice: "it's dumb code."
474 * Kernel guys get really het up about optimization, even when it's not
475 * necessary. I leave this code as a reaction against that.
477 static inline unsigned long page_align(unsigned long addr)
479 /* Add upwards and truncate downwards. */
480 return ((addr + getpagesize()-1) & ~(getpagesize()-1));
484 * An "initial ram disk" is a disk image loaded into memory along with the
485 * kernel which the kernel can use to boot from without needing any drivers.
486 * Most distributions now use this as standard: the initrd contains the code to
487 * load the appropriate driver modules for the current machine.
489 * Importantly, James Morris works for RedHat, and Fedora uses initrds for its
490 * kernels. He sent me this (and tells me when I break it).
492 static unsigned long load_initrd(const char *name, unsigned long mem)
498 ifd = open_or_die(name, O_RDONLY);
499 /* fstat() is needed to get the file size. */
500 if (fstat(ifd, &st) < 0)
501 err(1, "fstat() on initrd '%s'", name);
504 * We map the initrd at the top of memory, but mmap wants it to be
505 * page-aligned, so we round the size up for that.
507 len = page_align(st.st_size);
508 map_at(ifd, from_guest_phys(mem - len), 0, st.st_size);
510 * Once a file is mapped, you can close the file descriptor. It's a
511 * little odd, but quite useful.
514 verbose("mapped initrd %s size=%lu @ %p\n", name, len, (void*)mem-len);
516 /* We return the initrd size. */
522 * Simple routine to roll all the commandline arguments together with spaces
525 static void concat(char *dst, char *args[])
527 unsigned int i, len = 0;
529 for (i = 0; args[i]; i++) {
531 strcat(dst+len, " ");
534 strcpy(dst+len, args[i]);
535 len += strlen(args[i]);
537 /* In case it's empty. */
542 * This is where we actually tell the kernel to initialize the Guest. We
543 * saw the arguments it expects when we looked at initialize() in lguest_user.c:
544 * the base of Guest "physical" memory, the top physical page to allow and the
545 * entry point for the Guest.
547 static void tell_kernel(unsigned long start)
549 unsigned long args[] = { LHREQ_INITIALIZE,
550 (unsigned long)guest_base,
551 guest_limit / getpagesize(), start };
552 verbose("Guest: %p - %p (%#lx)\n",
553 guest_base, guest_base + guest_limit, guest_limit);
554 lguest_fd = open_or_die("/dev/lguest", O_RDWR);
555 if (write(lguest_fd, args, sizeof(args)) < 0)
556 err(1, "Writing to /dev/lguest");
563 * When the Guest gives us a buffer, it sends an array of addresses and sizes.
564 * We need to make sure it's not trying to reach into the Launcher itself, so
565 * we have a convenient routine which checks it and exits with an error message
566 * if something funny is going on:
568 static void *_check_pointer(unsigned long addr, unsigned int size,
572 * We have to separately check addr and addr+size, because size could
573 * be huge and addr + size might wrap around.
575 if (addr >= guest_limit || addr + size >= guest_limit)
576 errx(1, "%s:%i: Invalid address %#lx", __FILE__, line, addr);
578 * We return a pointer for the caller's convenience, now we know it's
581 return from_guest_phys(addr);
583 /* A macro which transparently hands the line number to the real function. */
584 #define check_pointer(addr,size) _check_pointer(addr, size, __LINE__)
587 * Each buffer in the virtqueues is actually a chain of descriptors. This
588 * function returns the next descriptor in the chain, or vq->vring.num if we're
591 static unsigned next_desc(struct vring_desc *desc,
592 unsigned int i, unsigned int max)
596 /* If this descriptor says it doesn't chain, we're done. */
597 if (!(desc[i].flags & VRING_DESC_F_NEXT))
600 /* Check they're not leading us off end of descriptors. */
602 /* Make sure compiler knows to grab that: we don't want it changing! */
606 errx(1, "Desc next is %u", next);
611 /* This actually sends the interrupt for this virtqueue */
612 static void trigger_irq(struct virtqueue *vq)
614 unsigned long buf[] = { LHREQ_IRQ, vq->config.irq };
616 /* Don't inform them if nothing used. */
617 if (!vq->pending_used)
619 vq->pending_used = 0;
621 /* If they don't want an interrupt, don't send one, unless empty. */
622 if ((vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
623 && lg_last_avail(vq) != vq->vring.avail->idx)
626 /* Send the Guest an interrupt tell them we used something up. */
627 if (write(lguest_fd, buf, sizeof(buf)) != 0)
628 err(1, "Triggering irq %i", vq->config.irq);
632 * This looks in the virtqueue and for the first available buffer, and converts
633 * it to an iovec for convenient access. Since descriptors consist of some
634 * number of output then some number of input descriptors, it's actually two
635 * iovecs, but we pack them into one and note how many of each there were.
637 * This function returns the descriptor number found.
639 static unsigned wait_for_vq_desc(struct virtqueue *vq,
641 unsigned int *out_num, unsigned int *in_num)
643 unsigned int i, head, max;
644 struct vring_desc *desc;
645 u16 last_avail = lg_last_avail(vq);
647 while (last_avail == vq->vring.avail->idx) {
650 /* OK, tell Guest about progress up to now. */
653 /* OK, now we need to know about added descriptors. */
654 vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY;
657 * They could have slipped one in as we were doing that: make
658 * sure it's written, then check again.
661 if (last_avail != vq->vring.avail->idx) {
662 vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
666 /* Nothing new? Wait for eventfd to tell us they refilled. */
667 if (read(vq->eventfd, &event, sizeof(event)) != sizeof(event))
668 errx(1, "Event read failed?");
670 /* We don't need to be notified again. */
671 vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
674 /* Check it isn't doing very strange things with descriptor numbers. */
675 if ((u16)(vq->vring.avail->idx - last_avail) > vq->vring.num)
676 errx(1, "Guest moved used index from %u to %u",
677 last_avail, vq->vring.avail->idx);
680 * Grab the next descriptor number they're advertising, and increment
681 * the index we've seen.
683 head = vq->vring.avail->ring[last_avail % vq->vring.num];
686 /* If their number is silly, that's a fatal mistake. */
687 if (head >= vq->vring.num)
688 errx(1, "Guest says index %u is available", head);
690 /* When we start there are none of either input nor output. */
691 *out_num = *in_num = 0;
694 desc = vq->vring.desc;
698 * If this is an indirect entry, then this buffer contains a descriptor
699 * table which we handle as if it's any normal descriptor chain.
701 if (desc[i].flags & VRING_DESC_F_INDIRECT) {
702 if (desc[i].len % sizeof(struct vring_desc))
703 errx(1, "Invalid size for indirect buffer table");
705 max = desc[i].len / sizeof(struct vring_desc);
706 desc = check_pointer(desc[i].addr, desc[i].len);
711 /* Grab the first descriptor, and check it's OK. */
712 iov[*out_num + *in_num].iov_len = desc[i].len;
713 iov[*out_num + *in_num].iov_base
714 = check_pointer(desc[i].addr, desc[i].len);
715 /* If this is an input descriptor, increment that count. */
716 if (desc[i].flags & VRING_DESC_F_WRITE)
720 * If it's an output descriptor, they're all supposed
721 * to come before any input descriptors.
724 errx(1, "Descriptor has out after in");
728 /* If we've got too many, that implies a descriptor loop. */
729 if (*out_num + *in_num > max)
730 errx(1, "Looped descriptor");
731 } while ((i = next_desc(desc, i, max)) != max);
737 * After we've used one of their buffers, we tell them about it. We'll then
738 * want to send them an interrupt, using trigger_irq().
740 static void add_used(struct virtqueue *vq, unsigned int head, int len)
742 struct vring_used_elem *used;
745 * The virtqueue contains a ring of used buffers. Get a pointer to the
746 * next entry in that used ring.
748 used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num];
751 /* Make sure buffer is written before we update index. */
753 vq->vring.used->idx++;
757 /* And here's the combo meal deal. Supersize me! */
758 static void add_used_and_trigger(struct virtqueue *vq, unsigned head, int len)
760 add_used(vq, head, len);
767 * We associate some data with the console for our exit hack.
771 /* How many times have they hit ^C? */
773 /* When did they start? */
774 struct timeval start;
777 /* This is the routine which handles console input (ie. stdin). */
778 static void console_input(struct virtqueue *vq)
781 unsigned int head, in_num, out_num;
782 struct console_abort *abort = vq->dev->priv;
783 struct iovec iov[vq->vring.num];
785 /* Make sure there's a descriptor waiting. */
786 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
788 errx(1, "Output buffers in console in queue?");
791 len = readv(STDIN_FILENO, iov, in_num);
793 /* Ran out of input? */
794 warnx("Failed to get console input, ignoring console.");
796 * For simplicity, dying threads kill the whole Launcher. So
803 add_used_and_trigger(vq, head, len);
806 * Three ^C within one second? Exit.
808 * This is such a hack, but works surprisingly well. Each ^C has to
809 * be in a buffer by itself, so they can't be too fast. But we check
810 * that we get three within about a second, so they can't be too
813 if (len != 1 || ((char *)iov[0].iov_base)[0] != 3) {
819 if (abort->count == 1)
820 gettimeofday(&abort->start, NULL);
821 else if (abort->count == 3) {
823 gettimeofday(&now, NULL);
824 /* Kill all Launcher processes with SIGINT, like normal ^C */
825 if (now.tv_sec <= abort->start.tv_sec+1)
831 /* This is the routine which handles console output (ie. stdout). */
832 static void console_output(struct virtqueue *vq)
834 unsigned int head, out, in;
835 struct iovec iov[vq->vring.num];
837 head = wait_for_vq_desc(vq, iov, &out, &in);
839 errx(1, "Input buffers in console output queue?");
840 while (!iov_empty(iov, out)) {
841 int len = writev(STDOUT_FILENO, iov, out);
843 err(1, "Write to stdout gave %i", len);
844 iov_consume(iov, out, len);
846 add_used(vq, head, 0);
852 * Handling output for network is also simple: we get all the output buffers
853 * and write them to /dev/net/tun.
859 static void net_output(struct virtqueue *vq)
861 struct net_info *net_info = vq->dev->priv;
862 unsigned int head, out, in;
863 struct iovec iov[vq->vring.num];
865 head = wait_for_vq_desc(vq, iov, &out, &in);
867 errx(1, "Input buffers in net output queue?");
868 if (writev(net_info->tunfd, iov, out) < 0)
869 errx(1, "Write to tun failed?");
870 add_used(vq, head, 0);
873 /* Will reading from this file descriptor block? */
874 static bool will_block(int fd)
877 struct timeval zero = { 0, 0 };
880 return select(fd+1, &fdset, NULL, NULL, &zero) != 1;
883 /* This handles packets coming in from the tun device to our Guest. */
884 static void net_input(struct virtqueue *vq)
887 unsigned int head, out, in;
888 struct iovec iov[vq->vring.num];
889 struct net_info *net_info = vq->dev->priv;
891 head = wait_for_vq_desc(vq, iov, &out, &in);
893 errx(1, "Output buffers in net input queue?");
895 /* Deliver interrupt now, since we're about to sleep. */
896 if (vq->pending_used && will_block(net_info->tunfd))
899 len = readv(net_info->tunfd, iov, in);
901 err(1, "Failed to read from tun.");
902 add_used(vq, head, len);
905 /* This is the helper to create threads. */
906 static int do_thread(void *_vq)
908 struct virtqueue *vq = _vq;
916 * When a child dies, we kill our entire process group with SIGTERM. This
917 * also has the side effect that the shell restores the console for us!
919 static void kill_launcher(int signal)
924 static void reset_device(struct device *dev)
926 struct virtqueue *vq;
928 verbose("Resetting device %s\n", dev->name);
930 /* Clear any features they've acked. */
931 memset(get_feature_bits(dev) + dev->feature_len, 0, dev->feature_len);
933 /* We're going to be explicitly killing threads, so ignore them. */
934 signal(SIGCHLD, SIG_IGN);
936 /* Zero out the virtqueues, get rid of their threads */
937 for (vq = dev->vq; vq; vq = vq->next) {
938 if (vq->thread != (pid_t)-1) {
939 kill(vq->thread, SIGTERM);
940 waitpid(vq->thread, NULL, 0);
941 vq->thread = (pid_t)-1;
943 memset(vq->vring.desc, 0,
944 vring_size(vq->config.num, LGUEST_VRING_ALIGN));
945 lg_last_avail(vq) = 0;
947 dev->running = false;
949 /* Now we care if threads die. */
950 signal(SIGCHLD, (void *)kill_launcher);
953 static void create_thread(struct virtqueue *vq)
956 * Create stack for thread and run it. Since the stack grows upwards,
957 * we point the stack pointer to the end of this region.
959 char *stack = malloc(32768);
960 unsigned long args[] = { LHREQ_EVENTFD,
961 vq->config.pfn*getpagesize(), 0 };
963 /* Create a zero-initialized eventfd. */
964 vq->eventfd = eventfd(0, 0);
966 err(1, "Creating eventfd");
967 args[2] = vq->eventfd;
969 /* Attach an eventfd to this virtqueue: it will go off
970 * when the Guest does an LHCALL_NOTIFY for this vq. */
971 if (write(lguest_fd, &args, sizeof(args)) != 0)
972 err(1, "Attaching eventfd");
974 /* CLONE_VM: because it has to access the Guest memory, and
975 * SIGCHLD so we get a signal if it dies. */
976 vq->thread = clone(do_thread, stack + 32768, CLONE_VM | SIGCHLD, vq);
977 if (vq->thread == (pid_t)-1)
978 err(1, "Creating clone");
979 /* We close our local copy, now the child has it. */
983 static void start_device(struct device *dev)
986 struct virtqueue *vq;
988 verbose("Device %s OK: offered", dev->name);
989 for (i = 0; i < dev->feature_len; i++)
990 verbose(" %02x", get_feature_bits(dev)[i]);
991 verbose(", accepted");
992 for (i = 0; i < dev->feature_len; i++)
993 verbose(" %02x", get_feature_bits(dev)
994 [dev->feature_len+i]);
996 for (vq = dev->vq; vq; vq = vq->next) {
1000 dev->running = true;
1003 static void cleanup_devices(void)
1007 for (dev = devices.dev; dev; dev = dev->next)
1010 /* If we saved off the original terminal settings, restore them now. */
1011 if (orig_term.c_lflag & (ISIG|ICANON|ECHO))
1012 tcsetattr(STDIN_FILENO, TCSANOW, &orig_term);
1015 /* When the Guest tells us they updated the status field, we handle it. */
1016 static void update_device_status(struct device *dev)
1018 /* A zero status is a reset, otherwise it's a set of flags. */
1019 if (dev->desc->status == 0)
1021 else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) {
1022 warnx("Device %s configuration FAILED", dev->name);
1025 } else if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK) {
1031 /* This is the generic routine we call when the Guest uses LHCALL_NOTIFY. */
1032 static void handle_output(unsigned long addr)
1036 /* Check each device. */
1037 for (i = devices.dev; i; i = i->next) {
1038 struct virtqueue *vq;
1040 /* Notifications to device descriptors update device status. */
1041 if (from_guest_phys(addr) == i->desc) {
1042 update_device_status(i);
1046 /* Devices *can* be used before status is set to DRIVER_OK. */
1047 for (vq = i->vq; vq; vq = vq->next) {
1048 if (addr != vq->config.pfn*getpagesize())
1051 errx(1, "Notification on running %s", i->name);
1058 * Early console write is done using notify on a nul-terminated string
1059 * in Guest memory. It's also great for hacking debugging messages
1062 if (addr >= guest_limit)
1063 errx(1, "Bad NOTIFY %#lx", addr);
1065 write(STDOUT_FILENO, from_guest_phys(addr),
1066 strnlen(from_guest_phys(addr), guest_limit - addr));
1072 * All devices need a descriptor so the Guest knows it exists, and a "struct
1073 * device" so the Launcher can keep track of it. We have common helper
1074 * routines to allocate and manage them.
1078 * The layout of the device page is a "struct lguest_device_desc" followed by a
1079 * number of virtqueue descriptors, then two sets of feature bits, then an
1080 * array of configuration bytes. This routine returns the configuration
1083 static u8 *device_config(const struct device *dev)
1085 return (void *)(dev->desc + 1)
1086 + dev->num_vq * sizeof(struct lguest_vqconfig)
1087 + dev->feature_len * 2;
1091 * This routine allocates a new "struct lguest_device_desc" from descriptor
1092 * table page just above the Guest's normal memory. It returns a pointer to
1095 static struct lguest_device_desc *new_dev_desc(u16 type)
1097 struct lguest_device_desc d = { .type = type };
1100 /* Figure out where the next device config is, based on the last one. */
1101 if (devices.lastdev)
1102 p = device_config(devices.lastdev)
1103 + devices.lastdev->desc->config_len;
1105 p = devices.descpage;
1107 /* We only have one page for all the descriptors. */
1108 if (p + sizeof(d) > (void *)devices.descpage + getpagesize())
1109 errx(1, "Too many devices");
1111 /* p might not be aligned, so we memcpy in. */
1112 return memcpy(p, &d, sizeof(d));
1116 * Each device descriptor is followed by the description of its virtqueues. We
1117 * specify how many descriptors the virtqueue is to have.
1119 static void add_virtqueue(struct device *dev, unsigned int num_descs,
1120 void (*service)(struct virtqueue *))
1123 struct virtqueue **i, *vq = malloc(sizeof(*vq));
1126 /* First we need some memory for this virtqueue. */
1127 pages = (vring_size(num_descs, LGUEST_VRING_ALIGN) + getpagesize() - 1)
1129 p = get_pages(pages);
1131 /* Initialize the virtqueue */
1133 vq->last_avail_idx = 0;
1135 vq->service = service;
1136 vq->thread = (pid_t)-1;
1138 /* Initialize the configuration. */
1139 vq->config.num = num_descs;
1140 vq->config.irq = devices.next_irq++;
1141 vq->config.pfn = to_guest_phys(p) / getpagesize();
1143 /* Initialize the vring. */
1144 vring_init(&vq->vring, num_descs, p, LGUEST_VRING_ALIGN);
1147 * Append virtqueue to this device's descriptor. We use
1148 * device_config() to get the end of the device's current virtqueues;
1149 * we check that we haven't added any config or feature information
1150 * yet, otherwise we'd be overwriting them.
1152 assert(dev->desc->config_len == 0 && dev->desc->feature_len == 0);
1153 memcpy(device_config(dev), &vq->config, sizeof(vq->config));
1155 dev->desc->num_vq++;
1157 verbose("Virtqueue page %#lx\n", to_guest_phys(p));
1160 * Add to tail of list, so dev->vq is first vq, dev->vq->next is
1163 for (i = &dev->vq; *i; i = &(*i)->next);
1168 * The first half of the feature bitmask is for us to advertise features. The
1169 * second half is for the Guest to accept features.
1171 static void add_feature(struct device *dev, unsigned bit)
1173 u8 *features = get_feature_bits(dev);
1175 /* We can't extend the feature bits once we've added config bytes */
1176 if (dev->desc->feature_len <= bit / CHAR_BIT) {
1177 assert(dev->desc->config_len == 0);
1178 dev->feature_len = dev->desc->feature_len = (bit/CHAR_BIT) + 1;
1181 features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT));
1185 * This routine sets the configuration fields for an existing device's
1186 * descriptor. It only works for the last device, but that's OK because that's
1189 static void set_config(struct device *dev, unsigned len, const void *conf)
1191 /* Check we haven't overflowed our single page. */
1192 if (device_config(dev) + len > devices.descpage + getpagesize())
1193 errx(1, "Too many devices");
1195 /* Copy in the config information, and store the length. */
1196 memcpy(device_config(dev), conf, len);
1197 dev->desc->config_len = len;
1199 /* Size must fit in config_len field (8 bits)! */
1200 assert(dev->desc->config_len == len);
1204 * This routine does all the creation and setup of a new device, including
1205 * calling new_dev_desc() to allocate the descriptor and device memory.
1207 * See what I mean about userspace being boring?
1209 static struct device *new_device(const char *name, u16 type)
1211 struct device *dev = malloc(sizeof(*dev));
1213 /* Now we populate the fields one at a time. */
1214 dev->desc = new_dev_desc(type);
1217 dev->feature_len = 0;
1219 dev->running = false;
1222 * Append to device list. Prepending to a single-linked list is
1223 * easier, but the user expects the devices to be arranged on the bus
1224 * in command-line order. The first network device on the command line
1225 * is eth0, the first block device /dev/vda, etc.
1227 if (devices.lastdev)
1228 devices.lastdev->next = dev;
1231 devices.lastdev = dev;
1237 * Our first setup routine is the console. It's a fairly simple device, but
1238 * UNIX tty handling makes it uglier than it could be.
1240 static void setup_console(void)
1244 /* If we can save the initial standard input settings... */
1245 if (tcgetattr(STDIN_FILENO, &orig_term) == 0) {
1246 struct termios term = orig_term;
1248 * Then we turn off echo, line buffering and ^C etc: We want a
1249 * raw input stream to the Guest.
1251 term.c_lflag &= ~(ISIG|ICANON|ECHO);
1252 tcsetattr(STDIN_FILENO, TCSANOW, &term);
1255 dev = new_device("console", VIRTIO_ID_CONSOLE);
1257 /* We store the console state in dev->priv, and initialize it. */
1258 dev->priv = malloc(sizeof(struct console_abort));
1259 ((struct console_abort *)dev->priv)->count = 0;
1262 * The console needs two virtqueues: the input then the output. When
1263 * they put something the input queue, we make sure we're listening to
1264 * stdin. When they put something in the output queue, we write it to
1267 add_virtqueue(dev, VIRTQUEUE_NUM, console_input);
1268 add_virtqueue(dev, VIRTQUEUE_NUM, console_output);
1270 verbose("device %u: console\n", ++devices.device_num);
1275 * Inter-guest networking is an interesting area. Simplest is to have a
1276 * --sharenet=<name> option which opens or creates a named pipe. This can be
1277 * used to send packets to another guest in a 1:1 manner.
1279 * More sopisticated is to use one of the tools developed for project like UML
1282 * Faster is to do virtio bonding in kernel. Doing this 1:1 would be
1283 * completely generic ("here's my vring, attach to your vring") and would work
1284 * for any traffic. Of course, namespace and permissions issues need to be
1285 * dealt with. A more sophisticated "multi-channel" virtio_net.c could hide
1286 * multiple inter-guest channels behind one interface, although it would
1287 * require some manner of hotplugging new virtio channels.
1289 * Finally, we could implement a virtio network switch in the kernel.
1292 static u32 str2ip(const char *ipaddr)
1296 if (sscanf(ipaddr, "%u.%u.%u.%u", &b[0], &b[1], &b[2], &b[3]) != 4)
1297 errx(1, "Failed to parse IP address '%s'", ipaddr);
1298 return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3];
1301 static void str2mac(const char *macaddr, unsigned char mac[6])
1304 if (sscanf(macaddr, "%02x:%02x:%02x:%02x:%02x:%02x",
1305 &m[0], &m[1], &m[2], &m[3], &m[4], &m[5]) != 6)
1306 errx(1, "Failed to parse mac address '%s'", macaddr);
1316 * This code is "adapted" from libbridge: it attaches the Host end of the
1317 * network device to the bridge device specified by the command line.
1319 * This is yet another James Morris contribution (I'm an IP-level guy, so I
1320 * dislike bridging), and I just try not to break it.
1322 static void add_to_bridge(int fd, const char *if_name, const char *br_name)
1328 errx(1, "must specify bridge name");
1330 ifidx = if_nametoindex(if_name);
1332 errx(1, "interface %s does not exist!", if_name);
1334 strncpy(ifr.ifr_name, br_name, IFNAMSIZ);
1335 ifr.ifr_name[IFNAMSIZ-1] = '\0';
1336 ifr.ifr_ifindex = ifidx;
1337 if (ioctl(fd, SIOCBRADDIF, &ifr) < 0)
1338 err(1, "can't add %s to bridge %s", if_name, br_name);
1342 * This sets up the Host end of the network device with an IP address, brings
1343 * it up so packets will flow, the copies the MAC address into the hwaddr
1346 static void configure_device(int fd, const char *tapif, u32 ipaddr)
1349 struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr;
1351 memset(&ifr, 0, sizeof(ifr));
1352 strcpy(ifr.ifr_name, tapif);
1354 /* Don't read these incantations. Just cut & paste them like I did! */
1355 sin->sin_family = AF_INET;
1356 sin->sin_addr.s_addr = htonl(ipaddr);
1357 if (ioctl(fd, SIOCSIFADDR, &ifr) != 0)
1358 err(1, "Setting %s interface address", tapif);
1359 ifr.ifr_flags = IFF_UP;
1360 if (ioctl(fd, SIOCSIFFLAGS, &ifr) != 0)
1361 err(1, "Bringing interface %s up", tapif);
1364 static int get_tun_device(char tapif[IFNAMSIZ])
1369 /* Start with this zeroed. Messy but sure. */
1370 memset(&ifr, 0, sizeof(ifr));
1373 * We open the /dev/net/tun device and tell it we want a tap device. A
1374 * tap device is like a tun device, only somehow different. To tell
1375 * the truth, I completely blundered my way through this code, but it
1378 netfd = open_or_die("/dev/net/tun", O_RDWR);
1379 ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
1380 strcpy(ifr.ifr_name, "tap%d");
1381 if (ioctl(netfd, TUNSETIFF, &ifr) != 0)
1382 err(1, "configuring /dev/net/tun");
1384 if (ioctl(netfd, TUNSETOFFLOAD,
1385 TUN_F_CSUM|TUN_F_TSO4|TUN_F_TSO6|TUN_F_TSO_ECN) != 0)
1386 err(1, "Could not set features for tun device");
1389 * We don't need checksums calculated for packets coming in this
1392 ioctl(netfd, TUNSETNOCSUM, 1);
1394 memcpy(tapif, ifr.ifr_name, IFNAMSIZ);
1399 * Our network is a Host<->Guest network. This can either use bridging or
1400 * routing, but the principle is the same: it uses the "tun" device to inject
1401 * packets into the Host as if they came in from a normal network card. We
1402 * just shunt packets between the Guest and the tun device.
1404 static void setup_tun_net(char *arg)
1407 struct net_info *net_info = malloc(sizeof(*net_info));
1409 u32 ip = INADDR_ANY;
1410 bool bridging = false;
1411 char tapif[IFNAMSIZ], *p;
1412 struct virtio_net_config conf;
1414 net_info->tunfd = get_tun_device(tapif);
1416 /* First we create a new network device. */
1417 dev = new_device("net", VIRTIO_ID_NET);
1418 dev->priv = net_info;
1420 /* Network devices need a recv and a send queue, just like console. */
1421 add_virtqueue(dev, VIRTQUEUE_NUM, net_input);
1422 add_virtqueue(dev, VIRTQUEUE_NUM, net_output);
1425 * We need a socket to perform the magic network ioctls to bring up the
1426 * tap interface, connect to the bridge etc. Any socket will do!
1428 ipfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
1430 err(1, "opening IP socket");
1432 /* If the command line was --tunnet=bridge:<name> do bridging. */
1433 if (!strncmp(BRIDGE_PFX, arg, strlen(BRIDGE_PFX))) {
1434 arg += strlen(BRIDGE_PFX);
1438 /* A mac address may follow the bridge name or IP address */
1439 p = strchr(arg, ':');
1441 str2mac(p+1, conf.mac);
1442 add_feature(dev, VIRTIO_NET_F_MAC);
1446 /* arg is now either an IP address or a bridge name */
1448 add_to_bridge(ipfd, tapif, arg);
1452 /* Set up the tun device. */
1453 configure_device(ipfd, tapif, ip);
1455 add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
1456 /* Expect Guest to handle everything except UFO */
1457 add_feature(dev, VIRTIO_NET_F_CSUM);
1458 add_feature(dev, VIRTIO_NET_F_GUEST_CSUM);
1459 add_feature(dev, VIRTIO_NET_F_GUEST_TSO4);
1460 add_feature(dev, VIRTIO_NET_F_GUEST_TSO6);
1461 add_feature(dev, VIRTIO_NET_F_GUEST_ECN);
1462 add_feature(dev, VIRTIO_NET_F_HOST_TSO4);
1463 add_feature(dev, VIRTIO_NET_F_HOST_TSO6);
1464 add_feature(dev, VIRTIO_NET_F_HOST_ECN);
1465 /* We handle indirect ring entries */
1466 add_feature(dev, VIRTIO_RING_F_INDIRECT_DESC);
1467 set_config(dev, sizeof(conf), &conf);
1469 /* We don't need the socket any more; setup is done. */
1472 devices.device_num++;
1475 verbose("device %u: tun %s attached to bridge: %s\n",
1476 devices.device_num, tapif, arg);
1478 verbose("device %u: tun %s: %s\n",
1479 devices.device_num, tapif, arg);
1483 * Our block (disk) device should be really simple: the Guest asks for a block
1484 * number and we read or write that position in the file. Unfortunately, that
1485 * was amazingly slow: the Guest waits until the read is finished before
1486 * running anything else, even if it could have been doing useful work.
1488 * We could use async I/O, except it's reputed to suck so hard that characters
1489 * actually go missing from your code when you try to use it.
1491 * So this was one reason why lguest now does all virtqueue servicing in
1492 * separate threads: it's more efficient and more like a real device.
1495 /* This hangs off device->priv. */
1498 /* The size of the file. */
1501 /* The file descriptor for the file. */
1504 /* IO thread listens on this file descriptor [0]. */
1507 /* IO thread writes to this file descriptor to mark it done, then
1508 * Launcher triggers interrupt to Guest. */
1515 * Remember that the block device is handled by a separate I/O thread. We head
1516 * straight into the core of that thread here:
1518 static void blk_request(struct virtqueue *vq)
1520 struct vblk_info *vblk = vq->dev->priv;
1521 unsigned int head, out_num, in_num, wlen;
1524 struct virtio_blk_outhdr *out;
1525 struct iovec iov[vq->vring.num];
1528 /* Get the next request. */
1529 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
1532 * Every block request should contain at least one output buffer
1533 * (detailing the location on disk and the type of request) and one
1534 * input buffer (to hold the result).
1536 if (out_num == 0 || in_num == 0)
1537 errx(1, "Bad virtblk cmd %u out=%u in=%u",
1538 head, out_num, in_num);
1540 out = convert(&iov[0], struct virtio_blk_outhdr);
1541 in = convert(&iov[out_num+in_num-1], u8);
1542 off = out->sector * 512;
1545 * The block device implements "barriers", where the Guest indicates
1546 * that it wants all previous writes to occur before this write. We
1547 * don't have a way of asking our kernel to do a barrier, so we just
1548 * synchronize all the data in the file. Pretty poor, no?
1550 if (out->type & VIRTIO_BLK_T_BARRIER)
1551 fdatasync(vblk->fd);
1554 * In general the virtio block driver is allowed to try SCSI commands.
1555 * It'd be nice if we supported eject, for example, but we don't.
1557 if (out->type & VIRTIO_BLK_T_SCSI_CMD) {
1558 fprintf(stderr, "Scsi commands unsupported\n");
1559 *in = VIRTIO_BLK_S_UNSUPP;
1561 } else if (out->type & VIRTIO_BLK_T_OUT) {
1565 * Move to the right location in the block file. This can fail
1566 * if they try to write past end.
1568 if (lseek64(vblk->fd, off, SEEK_SET) != off)
1569 err(1, "Bad seek to sector %llu", out->sector);
1571 ret = writev(vblk->fd, iov+1, out_num-1);
1572 verbose("WRITE to sector %llu: %i\n", out->sector, ret);
1575 * Grr... Now we know how long the descriptor they sent was, we
1576 * make sure they didn't try to write over the end of the block
1577 * file (possibly extending it).
1579 if (ret > 0 && off + ret > vblk->len) {
1580 /* Trim it back to the correct length */
1581 ftruncate64(vblk->fd, vblk->len);
1582 /* Die, bad Guest, die. */
1583 errx(1, "Write past end %llu+%u", off, ret);
1586 *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR);
1591 * Move to the right location in the block file. This can fail
1592 * if they try to read past end.
1594 if (lseek64(vblk->fd, off, SEEK_SET) != off)
1595 err(1, "Bad seek to sector %llu", out->sector);
1597 ret = readv(vblk->fd, iov+1, in_num-1);
1598 verbose("READ from sector %llu: %i\n", out->sector, ret);
1600 wlen = sizeof(*in) + ret;
1601 *in = VIRTIO_BLK_S_OK;
1604 *in = VIRTIO_BLK_S_IOERR;
1609 * OK, so we noted that it was pretty poor to use an fdatasync as a
1610 * barrier. But Christoph Hellwig points out that we need a sync
1611 * *afterwards* as well: "Barriers specify no reordering to the front
1612 * or the back." And Jens Axboe confirmed it, so here we are:
1614 if (out->type & VIRTIO_BLK_T_BARRIER)
1615 fdatasync(vblk->fd);
1617 add_used(vq, head, wlen);
1620 /*L:198 This actually sets up a virtual block device. */
1621 static void setup_block_file(const char *filename)
1624 struct vblk_info *vblk;
1625 struct virtio_blk_config conf;
1627 /* Creat the device. */
1628 dev = new_device("block", VIRTIO_ID_BLOCK);
1630 /* The device has one virtqueue, where the Guest places requests. */
1631 add_virtqueue(dev, VIRTQUEUE_NUM, blk_request);
1633 /* Allocate the room for our own bookkeeping */
1634 vblk = dev->priv = malloc(sizeof(*vblk));
1636 /* First we open the file and store the length. */
1637 vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE);
1638 vblk->len = lseek64(vblk->fd, 0, SEEK_END);
1640 /* We support barriers. */
1641 add_feature(dev, VIRTIO_BLK_F_BARRIER);
1643 /* Tell Guest how many sectors this device has. */
1644 conf.capacity = cpu_to_le64(vblk->len / 512);
1647 * Tell Guest not to put in too many descriptors at once: two are used
1648 * for the in and out elements.
1650 add_feature(dev, VIRTIO_BLK_F_SEG_MAX);
1651 conf.seg_max = cpu_to_le32(VIRTQUEUE_NUM - 2);
1653 /* Don't try to put whole struct: we have 8 bit limit. */
1654 set_config(dev, offsetof(struct virtio_blk_config, geometry), &conf);
1656 verbose("device %u: virtblock %llu sectors\n",
1657 ++devices.device_num, le64_to_cpu(conf.capacity));
1661 * Our random number generator device reads from /dev/random into the Guest's
1662 * input buffers. The usual case is that the Guest doesn't want random numbers
1663 * and so has no buffers although /dev/random is still readable, whereas
1664 * console is the reverse.
1666 * The same logic applies, however.
1672 static void rng_input(struct virtqueue *vq)
1675 unsigned int head, in_num, out_num, totlen = 0;
1676 struct rng_info *rng_info = vq->dev->priv;
1677 struct iovec iov[vq->vring.num];
1679 /* First we need a buffer from the Guests's virtqueue. */
1680 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
1682 errx(1, "Output buffers in rng?");
1685 * This is why we convert to iovecs: the readv() call uses them, and so
1686 * it reads straight into the Guest's buffer. We loop to make sure we
1689 while (!iov_empty(iov, in_num)) {
1690 len = readv(rng_info->rfd, iov, in_num);
1692 err(1, "Read from /dev/random gave %i", len);
1693 iov_consume(iov, in_num, len);
1697 /* Tell the Guest about the new input. */
1698 add_used(vq, head, totlen);
1702 * This creates a "hardware" random number device for the Guest.
1704 static void setup_rng(void)
1707 struct rng_info *rng_info = malloc(sizeof(*rng_info));
1709 /* Our device's privat info simply contains the /dev/random fd. */
1710 rng_info->rfd = open_or_die("/dev/random", O_RDONLY);
1712 /* Create the new device. */
1713 dev = new_device("rng", VIRTIO_ID_RNG);
1714 dev->priv = rng_info;
1716 /* The device has one virtqueue, where the Guest places inbufs. */
1717 add_virtqueue(dev, VIRTQUEUE_NUM, rng_input);
1719 verbose("device %u: rng\n", devices.device_num++);
1721 /* That's the end of device setup. */
1723 /*L:230 Reboot is pretty easy: clean up and exec() the Launcher afresh. */
1724 static void __attribute__((noreturn)) restart_guest(void)
1729 * Since we don't track all open fds, we simply close everything beyond
1732 for (i = 3; i < FD_SETSIZE; i++)
1735 /* Reset all the devices (kills all threads). */
1738 execv(main_args[0], main_args);
1739 err(1, "Could not exec %s", main_args[0]);
1743 * Finally we reach the core of the Launcher which runs the Guest, serves
1744 * its input and output, and finally, lays it to rest.
1746 static void __attribute__((noreturn)) run_guest(void)
1749 unsigned long notify_addr;
1752 /* We read from the /dev/lguest device to run the Guest. */
1753 readval = pread(lguest_fd, ¬ify_addr,
1754 sizeof(notify_addr), cpu_id);
1756 /* One unsigned long means the Guest did HCALL_NOTIFY */
1757 if (readval == sizeof(notify_addr)) {
1758 verbose("Notify on address %#lx\n", notify_addr);
1759 handle_output(notify_addr);
1760 /* ENOENT means the Guest died. Reading tells us why. */
1761 } else if (errno == ENOENT) {
1762 char reason[1024] = { 0 };
1763 pread(lguest_fd, reason, sizeof(reason)-1, cpu_id);
1764 errx(1, "%s", reason);
1765 /* ERESTART means that we need to reboot the guest */
1766 } else if (errno == ERESTART) {
1768 /* Anything else means a bug or incompatible change. */
1770 err(1, "Running guest failed");
1774 * This is the end of the Launcher. The good news: we are over halfway
1775 * through! The bad news: the most fiendish part of the code still lies ahead
1778 * Are you ready? Take a deep breath and join me in the core of the Host, in
1782 static struct option opts[] = {
1783 { "verbose", 0, NULL, 'v' },
1784 { "tunnet", 1, NULL, 't' },
1785 { "block", 1, NULL, 'b' },
1786 { "rng", 0, NULL, 'r' },
1787 { "initrd", 1, NULL, 'i' },
1790 static void usage(void)
1792 errx(1, "Usage: lguest [--verbose] "
1793 "[--tunnet=(<ipaddr>:<macaddr>|bridge:<bridgename>:<macaddr>)\n"
1794 "|--block=<filename>|--initrd=<filename>]...\n"
1795 "<mem-in-mb> vmlinux [args...]");
1798 /*L:105 The main routine is where the real work begins: */
1799 int main(int argc, char *argv[])
1801 /* Memory, code startpoint and size of the (optional) initrd. */
1802 unsigned long mem = 0, start, initrd_size = 0;
1803 /* Two temporaries. */
1805 /* The boot information for the Guest. */
1806 struct boot_params *boot;
1807 /* If they specify an initrd file to load. */
1808 const char *initrd_name = NULL;
1810 /* Save the args: we "reboot" by execing ourselves again. */
1814 * First we initialize the device list. We keep a pointer to the last
1815 * device, and the next interrupt number to use for devices (1:
1816 * remember that 0 is used by the timer).
1818 devices.lastdev = NULL;
1819 devices.next_irq = 1;
1823 * We need to know how much memory so we can set up the device
1824 * descriptor and memory pages for the devices as we parse the command
1825 * line. So we quickly look through the arguments to find the amount
1828 for (i = 1; i < argc; i++) {
1829 if (argv[i][0] != '-') {
1830 mem = atoi(argv[i]) * 1024 * 1024;
1832 * We start by mapping anonymous pages over all of
1833 * guest-physical memory range. This fills it with 0,
1834 * and ensures that the Guest won't be killed when it
1835 * tries to access it.
1837 guest_base = map_zeroed_pages(mem / getpagesize()
1840 guest_max = mem + DEVICE_PAGES*getpagesize();
1841 devices.descpage = get_pages(1);
1846 /* The options are fairly straight-forward */
1847 while ((c = getopt_long(argc, argv, "v", opts, NULL)) != EOF) {
1853 setup_tun_net(optarg);
1856 setup_block_file(optarg);
1862 initrd_name = optarg;
1865 warnx("Unknown argument %s", argv[optind]);
1870 * After the other arguments we expect memory and kernel image name,
1871 * followed by command line arguments for the kernel.
1873 if (optind + 2 > argc)
1876 verbose("Guest base is at %p\n", guest_base);
1878 /* We always have a console device */
1881 /* Now we load the kernel */
1882 start = load_kernel(open_or_die(argv[optind+1], O_RDONLY));
1884 /* Boot information is stashed at physical address 0 */
1885 boot = from_guest_phys(0);
1887 /* Map the initrd image if requested (at top of physical memory) */
1889 initrd_size = load_initrd(initrd_name, mem);
1891 * These are the location in the Linux boot header where the
1892 * start and size of the initrd are expected to be found.
1894 boot->hdr.ramdisk_image = mem - initrd_size;
1895 boot->hdr.ramdisk_size = initrd_size;
1896 /* The bootloader type 0xFF means "unknown"; that's OK. */
1897 boot->hdr.type_of_loader = 0xFF;
1901 * The Linux boot header contains an "E820" memory map: ours is a
1902 * simple, single region.
1904 boot->e820_entries = 1;
1905 boot->e820_map[0] = ((struct e820entry) { 0, mem, E820_RAM });
1907 * The boot header contains a command line pointer: we put the command
1908 * line after the boot header.
1910 boot->hdr.cmd_line_ptr = to_guest_phys(boot + 1);
1911 /* We use a simple helper to copy the arguments separated by spaces. */
1912 concat((char *)(boot + 1), argv+optind+2);
1914 /* Boot protocol version: 2.07 supports the fields for lguest. */
1915 boot->hdr.version = 0x207;
1917 /* The hardware_subarch value of "1" tells the Guest it's an lguest. */
1918 boot->hdr.hardware_subarch = 1;
1920 /* Tell the entry path not to try to reload segment registers. */
1921 boot->hdr.loadflags |= KEEP_SEGMENTS;
1924 * We tell the kernel to initialize the Guest: this returns the open
1925 * /dev/lguest file descriptor.
1929 /* Ensure that we terminate if a child dies. */
1930 signal(SIGCHLD, kill_launcher);
1932 /* If we exit via err(), this kills all the threads, restores tty. */
1933 atexit(cleanup_devices);
1935 /* Finally, run the Guest. This doesn't return. */
1941 * Mastery is done: you now know everything I do.
1943 * But surely you have seen code, features and bugs in your wanderings which
1944 * you now yearn to attack? That is the real game, and I look forward to you
1945 * patching and forking lguest into the Your-Name-Here-visor.
1947 * Farewell, and good coding!