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 /* How many are used since we sent last irq? */
155 unsigned int pending_used;
157 /* Eventfd where Guest notifications arrive. */
160 /* Function for the thread which is servicing this virtqueue. */
161 void (*service)(struct virtqueue *vq);
165 /* Remember the arguments to the program so we can "reboot" */
166 static char **main_args;
168 /* The original tty settings to restore on exit. */
169 static struct termios orig_term;
171 /* We have to be careful with barriers: our devices are all run in separate
172 * threads and so we need to make sure that changes visible to the Guest happen
173 * in precise order. */
174 #define wmb() __asm__ __volatile__("" : : : "memory")
175 #define mb() __asm__ __volatile__("" : : : "memory")
177 /* Convert an iovec element to the given type.
179 * This is a fairly ugly trick: we need to know the size of the type and
180 * alignment requirement to check the pointer is kosher. It's also nice to
181 * have the name of the type in case we report failure.
183 * Typing those three things all the time is cumbersome and error prone, so we
184 * have a macro which sets them all up and passes to the real function. */
185 #define convert(iov, type) \
186 ((type *)_convert((iov), sizeof(type), __alignof__(type), #type))
188 static void *_convert(struct iovec *iov, size_t size, size_t align,
191 if (iov->iov_len != size)
192 errx(1, "Bad iovec size %zu for %s", iov->iov_len, name);
193 if ((unsigned long)iov->iov_base % align != 0)
194 errx(1, "Bad alignment %p for %s", iov->iov_base, name);
195 return iov->iov_base;
198 /* Wrapper for the last available index. Makes it easier to change. */
199 #define lg_last_avail(vq) ((vq)->last_avail_idx)
201 /* The virtio configuration space is defined to be little-endian. x86 is
202 * little-endian too, but it's nice to be explicit so we have these helpers. */
203 #define cpu_to_le16(v16) (v16)
204 #define cpu_to_le32(v32) (v32)
205 #define cpu_to_le64(v64) (v64)
206 #define le16_to_cpu(v16) (v16)
207 #define le32_to_cpu(v32) (v32)
208 #define le64_to_cpu(v64) (v64)
210 /* Is this iovec empty? */
211 static bool iov_empty(const struct iovec iov[], unsigned int num_iov)
215 for (i = 0; i < num_iov; i++)
221 /* Take len bytes from the front of this iovec. */
222 static void iov_consume(struct iovec iov[], unsigned num_iov, unsigned len)
226 for (i = 0; i < num_iov; i++) {
229 used = iov[i].iov_len < len ? iov[i].iov_len : len;
230 iov[i].iov_base += used;
231 iov[i].iov_len -= used;
237 /* The device virtqueue descriptors are followed by feature bitmasks. */
238 static u8 *get_feature_bits(struct device *dev)
240 return (u8 *)(dev->desc + 1)
241 + dev->num_vq * sizeof(struct lguest_vqconfig);
244 /*L:100 The Launcher code itself takes us out into userspace, that scary place
245 * where pointers run wild and free! Unfortunately, like most userspace
246 * programs, it's quite boring (which is why everyone likes to hack on the
247 * kernel!). Perhaps if you make up an Lguest Drinking Game at this point, it
248 * will get you through this section. Or, maybe not.
250 * The Launcher sets up a big chunk of memory to be the Guest's "physical"
251 * memory and stores it in "guest_base". In other words, Guest physical ==
252 * Launcher virtual with an offset.
254 * This can be tough to get your head around, but usually it just means that we
255 * use these trivial conversion functions when the Guest gives us it's
256 * "physical" addresses: */
257 static void *from_guest_phys(unsigned long addr)
259 return guest_base + addr;
262 static unsigned long to_guest_phys(const void *addr)
264 return (addr - guest_base);
268 * Loading the Kernel.
270 * We start with couple of simple helper routines. open_or_die() avoids
271 * error-checking code cluttering the callers: */
272 static int open_or_die(const char *name, int flags)
274 int fd = open(name, flags);
276 err(1, "Failed to open %s", name);
280 /* map_zeroed_pages() takes a number of pages. */
281 static void *map_zeroed_pages(unsigned int num)
283 int fd = open_or_die("/dev/zero", O_RDONLY);
286 /* We use a private mapping (ie. if we write to the page, it will be
288 addr = mmap(NULL, getpagesize() * num,
289 PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0);
290 if (addr == MAP_FAILED)
291 err(1, "Mmaping %u pages of /dev/zero", num);
297 /* Get some more pages for a device. */
298 static void *get_pages(unsigned int num)
300 void *addr = from_guest_phys(guest_limit);
302 guest_limit += num * getpagesize();
303 if (guest_limit > guest_max)
304 errx(1, "Not enough memory for devices");
308 /* This routine is used to load the kernel or initrd. It tries mmap, but if
309 * that fails (Plan 9's kernel file isn't nicely aligned on page boundaries),
310 * it falls back to reading the memory in. */
311 static void map_at(int fd, void *addr, unsigned long offset, unsigned long len)
315 /* We map writable even though for some segments are marked read-only.
316 * The kernel really wants to be writable: it patches its own
319 * MAP_PRIVATE means that the page won't be copied until a write is
320 * done to it. This allows us to share untouched memory between
322 if (mmap(addr, len, PROT_READ|PROT_WRITE|PROT_EXEC,
323 MAP_FIXED|MAP_PRIVATE, fd, offset) != MAP_FAILED)
326 /* pread does a seek and a read in one shot: saves a few lines. */
327 r = pread(fd, addr, len, offset);
329 err(1, "Reading offset %lu len %lu gave %zi", offset, len, r);
332 /* This routine takes an open vmlinux image, which is in ELF, and maps it into
333 * the Guest memory. ELF = Embedded Linking Format, which is the format used
334 * by all modern binaries on Linux including the kernel.
336 * The ELF headers give *two* addresses: a physical address, and a virtual
337 * address. We use the physical address; the Guest will map itself to the
340 * We return the starting address. */
341 static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr)
343 Elf32_Phdr phdr[ehdr->e_phnum];
346 /* Sanity checks on the main ELF header: an x86 executable with a
347 * reasonable number of correctly-sized program headers. */
348 if (ehdr->e_type != ET_EXEC
349 || ehdr->e_machine != EM_386
350 || ehdr->e_phentsize != sizeof(Elf32_Phdr)
351 || ehdr->e_phnum < 1 || ehdr->e_phnum > 65536U/sizeof(Elf32_Phdr))
352 errx(1, "Malformed elf header");
354 /* An ELF executable contains an ELF header and a number of "program"
355 * headers which indicate which parts ("segments") of the program to
358 /* We read in all the program headers at once: */
359 if (lseek(elf_fd, ehdr->e_phoff, SEEK_SET) < 0)
360 err(1, "Seeking to program headers");
361 if (read(elf_fd, phdr, sizeof(phdr)) != sizeof(phdr))
362 err(1, "Reading program headers");
364 /* Try all the headers: there are usually only three. A read-only one,
365 * a read-write one, and a "note" section which we don't load. */
366 for (i = 0; i < ehdr->e_phnum; i++) {
367 /* If this isn't a loadable segment, we ignore it */
368 if (phdr[i].p_type != PT_LOAD)
371 verbose("Section %i: size %i addr %p\n",
372 i, phdr[i].p_memsz, (void *)phdr[i].p_paddr);
374 /* We map this section of the file at its physical address. */
375 map_at(elf_fd, from_guest_phys(phdr[i].p_paddr),
376 phdr[i].p_offset, phdr[i].p_filesz);
379 /* The entry point is given in the ELF header. */
380 return ehdr->e_entry;
383 /*L:150 A bzImage, unlike an ELF file, is not meant to be loaded. You're
384 * supposed to jump into it and it will unpack itself. We used to have to
385 * perform some hairy magic because the unpacking code scared me.
387 * Fortunately, Jeremy Fitzhardinge convinced me it wasn't that hard and wrote
388 * a small patch to jump over the tricky bits in the Guest, so now we just read
389 * the funky header so we know where in the file to load, and away we go! */
390 static unsigned long load_bzimage(int fd)
392 struct boot_params boot;
394 /* Modern bzImages get loaded at 1M. */
395 void *p = from_guest_phys(0x100000);
397 /* Go back to the start of the file and read the header. It should be
398 * a Linux boot header (see Documentation/x86/i386/boot.txt) */
399 lseek(fd, 0, SEEK_SET);
400 read(fd, &boot, sizeof(boot));
402 /* Inside the setup_hdr, we expect the magic "HdrS" */
403 if (memcmp(&boot.hdr.header, "HdrS", 4) != 0)
404 errx(1, "This doesn't look like a bzImage to me");
406 /* Skip over the extra sectors of the header. */
407 lseek(fd, (boot.hdr.setup_sects+1) * 512, SEEK_SET);
409 /* Now read everything into memory. in nice big chunks. */
410 while ((r = read(fd, p, 65536)) > 0)
413 /* Finally, code32_start tells us where to enter the kernel. */
414 return boot.hdr.code32_start;
417 /*L:140 Loading the kernel is easy when it's a "vmlinux", but most kernels
418 * come wrapped up in the self-decompressing "bzImage" format. With a little
419 * work, we can load those, too. */
420 static unsigned long load_kernel(int fd)
424 /* Read in the first few bytes. */
425 if (read(fd, &hdr, sizeof(hdr)) != sizeof(hdr))
426 err(1, "Reading kernel");
428 /* If it's an ELF file, it starts with "\177ELF" */
429 if (memcmp(hdr.e_ident, ELFMAG, SELFMAG) == 0)
430 return map_elf(fd, &hdr);
432 /* Otherwise we assume it's a bzImage, and try to load it. */
433 return load_bzimage(fd);
436 /* This is a trivial little helper to align pages. Andi Kleen hated it because
437 * it calls getpagesize() twice: "it's dumb code."
439 * Kernel guys get really het up about optimization, even when it's not
440 * necessary. I leave this code as a reaction against that. */
441 static inline unsigned long page_align(unsigned long addr)
443 /* Add upwards and truncate downwards. */
444 return ((addr + getpagesize()-1) & ~(getpagesize()-1));
447 /*L:180 An "initial ram disk" is a disk image loaded into memory along with
448 * the kernel which the kernel can use to boot from without needing any
449 * drivers. Most distributions now use this as standard: the initrd contains
450 * the code to load the appropriate driver modules for the current machine.
452 * Importantly, James Morris works for RedHat, and Fedora uses initrds for its
453 * kernels. He sent me this (and tells me when I break it). */
454 static unsigned long load_initrd(const char *name, unsigned long mem)
460 ifd = open_or_die(name, O_RDONLY);
461 /* fstat() is needed to get the file size. */
462 if (fstat(ifd, &st) < 0)
463 err(1, "fstat() on initrd '%s'", name);
465 /* We map the initrd at the top of memory, but mmap wants it to be
466 * page-aligned, so we round the size up for that. */
467 len = page_align(st.st_size);
468 map_at(ifd, from_guest_phys(mem - len), 0, st.st_size);
469 /* Once a file is mapped, you can close the file descriptor. It's a
470 * little odd, but quite useful. */
472 verbose("mapped initrd %s size=%lu @ %p\n", name, len, (void*)mem-len);
474 /* We return the initrd size. */
479 /* Simple routine to roll all the commandline arguments together with spaces
481 static void concat(char *dst, char *args[])
483 unsigned int i, len = 0;
485 for (i = 0; args[i]; i++) {
487 strcat(dst+len, " ");
490 strcpy(dst+len, args[i]);
491 len += strlen(args[i]);
493 /* In case it's empty. */
497 /*L:185 This is where we actually tell the kernel to initialize the Guest. We
498 * saw the arguments it expects when we looked at initialize() in lguest_user.c:
499 * the base of Guest "physical" memory, the top physical page to allow and the
500 * entry point for the Guest. */
501 static void tell_kernel(unsigned long start)
503 unsigned long args[] = { LHREQ_INITIALIZE,
504 (unsigned long)guest_base,
505 guest_limit / getpagesize(), start };
506 verbose("Guest: %p - %p (%#lx)\n",
507 guest_base, guest_base + guest_limit, guest_limit);
508 lguest_fd = open_or_die("/dev/lguest", O_RDWR);
509 if (write(lguest_fd, args, sizeof(args)) < 0)
510 err(1, "Writing to /dev/lguest");
517 * When the Guest gives us a buffer, it sends an array of addresses and sizes.
518 * We need to make sure it's not trying to reach into the Launcher itself, so
519 * we have a convenient routine which checks it and exits with an error message
520 * if something funny is going on:
522 static void *_check_pointer(unsigned long addr, unsigned int size,
525 /* We have to separately check addr and addr+size, because size could
526 * be huge and addr + size might wrap around. */
527 if (addr >= guest_limit || addr + size >= guest_limit)
528 errx(1, "%s:%i: Invalid address %#lx", __FILE__, line, addr);
529 /* We return a pointer for the caller's convenience, now we know it's
531 return from_guest_phys(addr);
533 /* A macro which transparently hands the line number to the real function. */
534 #define check_pointer(addr,size) _check_pointer(addr, size, __LINE__)
536 /* Each buffer in the virtqueues is actually a chain of descriptors. This
537 * function returns the next descriptor in the chain, or vq->vring.num if we're
539 static unsigned next_desc(struct virtqueue *vq, unsigned int i)
543 /* If this descriptor says it doesn't chain, we're done. */
544 if (!(vq->vring.desc[i].flags & VRING_DESC_F_NEXT))
545 return vq->vring.num;
547 /* Check they're not leading us off end of descriptors. */
548 next = vq->vring.desc[i].next;
549 /* Make sure compiler knows to grab that: we don't want it changing! */
552 if (next >= vq->vring.num)
553 errx(1, "Desc next is %u", next);
558 /* This actually sends the interrupt for this virtqueue */
559 static void trigger_irq(struct virtqueue *vq)
561 unsigned long buf[] = { LHREQ_IRQ, vq->config.irq };
563 /* Don't inform them if nothing used. */
564 if (!vq->pending_used)
566 vq->pending_used = 0;
568 /* If they don't want an interrupt, don't send one, unless empty. */
569 if ((vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
570 && lg_last_avail(vq) != vq->vring.avail->idx)
573 /* Send the Guest an interrupt tell them we used something up. */
574 if (write(lguest_fd, buf, sizeof(buf)) != 0)
575 err(1, "Triggering irq %i", vq->config.irq);
578 /* This looks in the virtqueue and for the first available buffer, and converts
579 * it to an iovec for convenient access. Since descriptors consist of some
580 * number of output then some number of input descriptors, it's actually two
581 * iovecs, but we pack them into one and note how many of each there were.
583 * This function returns the descriptor number found. */
584 static unsigned wait_for_vq_desc(struct virtqueue *vq,
586 unsigned int *out_num, unsigned int *in_num)
588 unsigned int i, head;
589 u16 last_avail = lg_last_avail(vq);
591 while (last_avail == vq->vring.avail->idx) {
594 /* OK, tell Guest about progress up to now. */
597 /* OK, now we need to know about added descriptors. */
598 vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY;
600 /* They could have slipped one in as we were doing that: make
601 * sure it's written, then check again. */
603 if (last_avail != vq->vring.avail->idx) {
604 vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
608 /* Nothing new? Wait for eventfd to tell us they refilled. */
609 if (read(vq->eventfd, &event, sizeof(event)) != sizeof(event))
610 errx(1, "Event read failed?");
612 /* We don't need to be notified again. */
613 vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
616 /* Check it isn't doing very strange things with descriptor numbers. */
617 if ((u16)(vq->vring.avail->idx - last_avail) > vq->vring.num)
618 errx(1, "Guest moved used index from %u to %u",
619 last_avail, vq->vring.avail->idx);
621 /* Grab the next descriptor number they're advertising, and increment
622 * the index we've seen. */
623 head = vq->vring.avail->ring[last_avail % vq->vring.num];
626 /* If their number is silly, that's a fatal mistake. */
627 if (head >= vq->vring.num)
628 errx(1, "Guest says index %u is available", head);
630 /* When we start there are none of either input nor output. */
631 *out_num = *in_num = 0;
635 /* Grab the first descriptor, and check it's OK. */
636 iov[*out_num + *in_num].iov_len = vq->vring.desc[i].len;
637 iov[*out_num + *in_num].iov_base
638 = check_pointer(vq->vring.desc[i].addr,
639 vq->vring.desc[i].len);
640 /* If this is an input descriptor, increment that count. */
641 if (vq->vring.desc[i].flags & VRING_DESC_F_WRITE)
644 /* If it's an output descriptor, they're all supposed
645 * to come before any input descriptors. */
647 errx(1, "Descriptor has out after in");
651 /* If we've got too many, that implies a descriptor loop. */
652 if (*out_num + *in_num > vq->vring.num)
653 errx(1, "Looped descriptor");
654 } while ((i = next_desc(vq, i)) != vq->vring.num);
659 /* After we've used one of their buffers, we tell them about it. We'll then
660 * want to send them an interrupt, using trigger_irq(). */
661 static void add_used(struct virtqueue *vq, unsigned int head, int len)
663 struct vring_used_elem *used;
665 /* The virtqueue contains a ring of used buffers. Get a pointer to the
666 * next entry in that used ring. */
667 used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num];
670 /* Make sure buffer is written before we update index. */
672 vq->vring.used->idx++;
676 /* And here's the combo meal deal. Supersize me! */
677 static void add_used_and_trigger(struct virtqueue *vq, unsigned head, int len)
679 add_used(vq, head, len);
686 * We associate some data with the console for our exit hack. */
689 /* How many times have they hit ^C? */
691 /* When did they start? */
692 struct timeval start;
695 /* This is the routine which handles console input (ie. stdin). */
696 static void console_input(struct virtqueue *vq)
699 unsigned int head, in_num, out_num;
700 struct console_abort *abort = vq->dev->priv;
701 struct iovec iov[vq->vring.num];
703 /* Make sure there's a descriptor waiting. */
704 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
706 errx(1, "Output buffers in console in queue?");
709 len = readv(STDIN_FILENO, iov, in_num);
711 /* Ran out of input? */
712 warnx("Failed to get console input, ignoring console.");
713 /* For simplicity, dying threads kill the whole Launcher. So
719 add_used_and_trigger(vq, head, len);
721 /* Three ^C within one second? Exit.
723 * This is such a hack, but works surprisingly well. Each ^C has to
724 * be in a buffer by itself, so they can't be too fast. But we check
725 * that we get three within about a second, so they can't be too
727 if (len != 1 || ((char *)iov[0].iov_base)[0] != 3) {
733 if (abort->count == 1)
734 gettimeofday(&abort->start, NULL);
735 else if (abort->count == 3) {
737 gettimeofday(&now, NULL);
738 /* Kill all Launcher processes with SIGINT, like normal ^C */
739 if (now.tv_sec <= abort->start.tv_sec+1)
745 /* This is the routine which handles console output (ie. stdout). */
746 static void console_output(struct virtqueue *vq)
748 unsigned int head, out, in;
749 struct iovec iov[vq->vring.num];
751 head = wait_for_vq_desc(vq, iov, &out, &in);
753 errx(1, "Input buffers in console output queue?");
754 while (!iov_empty(iov, out)) {
755 int len = writev(STDOUT_FILENO, iov, out);
757 err(1, "Write to stdout gave %i", len);
758 iov_consume(iov, out, len);
760 add_used(vq, head, 0);
766 * Handling output for network is also simple: we get all the output buffers
767 * and write them to /dev/net/tun.
773 static void net_output(struct virtqueue *vq)
775 struct net_info *net_info = vq->dev->priv;
776 unsigned int head, out, in;
777 struct iovec iov[vq->vring.num];
779 head = wait_for_vq_desc(vq, iov, &out, &in);
781 errx(1, "Input buffers in net output queue?");
782 if (writev(net_info->tunfd, iov, out) < 0)
783 errx(1, "Write to tun failed?");
784 add_used(vq, head, 0);
787 /* Will reading from this file descriptor block? */
788 static bool will_block(int fd)
791 struct timeval zero = { 0, 0 };
794 return select(fd+1, &fdset, NULL, NULL, &zero) != 1;
797 /* This is where we handle packets coming in from the tun device to our
799 static void net_input(struct virtqueue *vq)
802 unsigned int head, out, in;
803 struct iovec iov[vq->vring.num];
804 struct net_info *net_info = vq->dev->priv;
806 head = wait_for_vq_desc(vq, iov, &out, &in);
808 errx(1, "Output buffers in net input queue?");
810 /* Deliver interrupt now, since we're about to sleep. */
811 if (vq->pending_used && will_block(net_info->tunfd))
814 len = readv(net_info->tunfd, iov, in);
816 err(1, "Failed to read from tun.");
817 add_used(vq, head, len);
820 /* This is the helper to create threads. */
821 static int do_thread(void *_vq)
823 struct virtqueue *vq = _vq;
830 /* When a child dies, we kill our entire process group with SIGTERM. This
831 * also has the side effect that the shell restores the console for us! */
832 static void kill_launcher(int signal)
837 static void reset_device(struct device *dev)
839 struct virtqueue *vq;
841 verbose("Resetting device %s\n", dev->name);
843 /* Clear any features they've acked. */
844 memset(get_feature_bits(dev) + dev->feature_len, 0, dev->feature_len);
846 /* We're going to be explicitly killing threads, so ignore them. */
847 signal(SIGCHLD, SIG_IGN);
849 /* Zero out the virtqueues, get rid of their threads */
850 for (vq = dev->vq; vq; vq = vq->next) {
851 if (vq->thread != (pid_t)-1) {
852 kill(vq->thread, SIGTERM);
853 waitpid(vq->thread, NULL, 0);
854 vq->thread = (pid_t)-1;
856 memset(vq->vring.desc, 0,
857 vring_size(vq->config.num, LGUEST_VRING_ALIGN));
858 lg_last_avail(vq) = 0;
860 dev->running = false;
862 /* Now we care if threads die. */
863 signal(SIGCHLD, (void *)kill_launcher);
866 static void create_thread(struct virtqueue *vq)
868 /* Create stack for thread and run it. Since stack grows
869 * upwards, we point the stack pointer to the end of this
871 char *stack = malloc(32768);
872 unsigned long args[] = { LHREQ_EVENTFD,
873 vq->config.pfn*getpagesize(), 0 };
875 /* Create a zero-initialized eventfd. */
876 vq->eventfd = eventfd(0, 0);
878 err(1, "Creating eventfd");
879 args[2] = vq->eventfd;
881 /* Attach an eventfd to this virtqueue: it will go off
882 * when the Guest does an LHCALL_NOTIFY for this vq. */
883 if (write(lguest_fd, &args, sizeof(args)) != 0)
884 err(1, "Attaching eventfd");
886 /* CLONE_VM: because it has to access the Guest memory, and
887 * SIGCHLD so we get a signal if it dies. */
888 vq->thread = clone(do_thread, stack + 32768, CLONE_VM | SIGCHLD, vq);
889 if (vq->thread == (pid_t)-1)
890 err(1, "Creating clone");
891 /* We close our local copy, now the child has it. */
895 static void start_device(struct device *dev)
898 struct virtqueue *vq;
900 verbose("Device %s OK: offered", dev->name);
901 for (i = 0; i < dev->feature_len; i++)
902 verbose(" %02x", get_feature_bits(dev)[i]);
903 verbose(", accepted");
904 for (i = 0; i < dev->feature_len; i++)
905 verbose(" %02x", get_feature_bits(dev)
906 [dev->feature_len+i]);
908 for (vq = dev->vq; vq; vq = vq->next) {
915 static void cleanup_devices(void)
919 for (dev = devices.dev; dev; dev = dev->next)
922 /* If we saved off the original terminal settings, restore them now. */
923 if (orig_term.c_lflag & (ISIG|ICANON|ECHO))
924 tcsetattr(STDIN_FILENO, TCSANOW, &orig_term);
927 /* When the Guest tells us they updated the status field, we handle it. */
928 static void update_device_status(struct device *dev)
930 /* A zero status is a reset, otherwise it's a set of flags. */
931 if (dev->desc->status == 0)
933 else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) {
934 warnx("Device %s configuration FAILED", dev->name);
937 } else if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK) {
943 /* This is the generic routine we call when the Guest uses LHCALL_NOTIFY. */
944 static void handle_output(unsigned long addr)
948 /* Check each device. */
949 for (i = devices.dev; i; i = i->next) {
950 struct virtqueue *vq;
952 /* Notifications to device descriptors update device status. */
953 if (from_guest_phys(addr) == i->desc) {
954 update_device_status(i);
958 /* Devices *can* be used before status is set to DRIVER_OK. */
959 for (vq = i->vq; vq; vq = vq->next) {
960 if (addr != vq->config.pfn*getpagesize())
963 errx(1, "Notification on running %s", i->name);
969 /* Early console write is done using notify on a nul-terminated string
970 * in Guest memory. */
971 if (addr >= guest_limit)
972 errx(1, "Bad NOTIFY %#lx", addr);
974 write(STDOUT_FILENO, from_guest_phys(addr),
975 strnlen(from_guest_phys(addr), guest_limit - addr));
981 * All devices need a descriptor so the Guest knows it exists, and a "struct
982 * device" so the Launcher can keep track of it. We have common helper
983 * routines to allocate and manage them.
986 /* The layout of the device page is a "struct lguest_device_desc" followed by a
987 * number of virtqueue descriptors, then two sets of feature bits, then an
988 * array of configuration bytes. This routine returns the configuration
990 static u8 *device_config(const struct device *dev)
992 return (void *)(dev->desc + 1)
993 + dev->num_vq * sizeof(struct lguest_vqconfig)
994 + dev->feature_len * 2;
997 /* This routine allocates a new "struct lguest_device_desc" from descriptor
998 * table page just above the Guest's normal memory. It returns a pointer to
999 * that descriptor. */
1000 static struct lguest_device_desc *new_dev_desc(u16 type)
1002 struct lguest_device_desc d = { .type = type };
1005 /* Figure out where the next device config is, based on the last one. */
1006 if (devices.lastdev)
1007 p = device_config(devices.lastdev)
1008 + devices.lastdev->desc->config_len;
1010 p = devices.descpage;
1012 /* We only have one page for all the descriptors. */
1013 if (p + sizeof(d) > (void *)devices.descpage + getpagesize())
1014 errx(1, "Too many devices");
1016 /* p might not be aligned, so we memcpy in. */
1017 return memcpy(p, &d, sizeof(d));
1020 /* Each device descriptor is followed by the description of its virtqueues. We
1021 * specify how many descriptors the virtqueue is to have. */
1022 static void add_virtqueue(struct device *dev, unsigned int num_descs,
1023 void (*service)(struct virtqueue *))
1026 struct virtqueue **i, *vq = malloc(sizeof(*vq));
1029 /* First we need some memory for this virtqueue. */
1030 pages = (vring_size(num_descs, LGUEST_VRING_ALIGN) + getpagesize() - 1)
1032 p = get_pages(pages);
1034 /* Initialize the virtqueue */
1036 vq->last_avail_idx = 0;
1038 vq->service = service;
1039 vq->thread = (pid_t)-1;
1041 /* Initialize the configuration. */
1042 vq->config.num = num_descs;
1043 vq->config.irq = devices.next_irq++;
1044 vq->config.pfn = to_guest_phys(p) / getpagesize();
1046 /* Initialize the vring. */
1047 vring_init(&vq->vring, num_descs, p, LGUEST_VRING_ALIGN);
1049 /* Append virtqueue to this device's descriptor. We use
1050 * device_config() to get the end of the device's current virtqueues;
1051 * we check that we haven't added any config or feature information
1052 * yet, otherwise we'd be overwriting them. */
1053 assert(dev->desc->config_len == 0 && dev->desc->feature_len == 0);
1054 memcpy(device_config(dev), &vq->config, sizeof(vq->config));
1056 dev->desc->num_vq++;
1058 verbose("Virtqueue page %#lx\n", to_guest_phys(p));
1060 /* Add to tail of list, so dev->vq is first vq, dev->vq->next is
1062 for (i = &dev->vq; *i; i = &(*i)->next);
1066 /* The first half of the feature bitmask is for us to advertise features. The
1067 * second half is for the Guest to accept features. */
1068 static void add_feature(struct device *dev, unsigned bit)
1070 u8 *features = get_feature_bits(dev);
1072 /* We can't extend the feature bits once we've added config bytes */
1073 if (dev->desc->feature_len <= bit / CHAR_BIT) {
1074 assert(dev->desc->config_len == 0);
1075 dev->feature_len = dev->desc->feature_len = (bit/CHAR_BIT) + 1;
1078 features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT));
1081 /* This routine sets the configuration fields for an existing device's
1082 * descriptor. It only works for the last device, but that's OK because that's
1084 static void set_config(struct device *dev, unsigned len, const void *conf)
1086 /* Check we haven't overflowed our single page. */
1087 if (device_config(dev) + len > devices.descpage + getpagesize())
1088 errx(1, "Too many devices");
1090 /* Copy in the config information, and store the length. */
1091 memcpy(device_config(dev), conf, len);
1092 dev->desc->config_len = len;
1095 /* This routine does all the creation and setup of a new device, including
1096 * calling new_dev_desc() to allocate the descriptor and device memory.
1098 * See what I mean about userspace being boring? */
1099 static struct device *new_device(const char *name, u16 type)
1101 struct device *dev = malloc(sizeof(*dev));
1103 /* Now we populate the fields one at a time. */
1104 dev->desc = new_dev_desc(type);
1107 dev->feature_len = 0;
1109 dev->running = false;
1111 /* Append to device list. Prepending to a single-linked list is
1112 * easier, but the user expects the devices to be arranged on the bus
1113 * in command-line order. The first network device on the command line
1114 * is eth0, the first block device /dev/vda, etc. */
1115 if (devices.lastdev)
1116 devices.lastdev->next = dev;
1119 devices.lastdev = dev;
1124 /* Our first setup routine is the console. It's a fairly simple device, but
1125 * UNIX tty handling makes it uglier than it could be. */
1126 static void setup_console(void)
1130 /* If we can save the initial standard input settings... */
1131 if (tcgetattr(STDIN_FILENO, &orig_term) == 0) {
1132 struct termios term = orig_term;
1133 /* Then we turn off echo, line buffering and ^C etc. We want a
1134 * raw input stream to the Guest. */
1135 term.c_lflag &= ~(ISIG|ICANON|ECHO);
1136 tcsetattr(STDIN_FILENO, TCSANOW, &term);
1139 dev = new_device("console", VIRTIO_ID_CONSOLE);
1141 /* We store the console state in dev->priv, and initialize it. */
1142 dev->priv = malloc(sizeof(struct console_abort));
1143 ((struct console_abort *)dev->priv)->count = 0;
1145 /* The console needs two virtqueues: the input then the output. When
1146 * they put something the input queue, we make sure we're listening to
1147 * stdin. When they put something in the output queue, we write it to
1149 add_virtqueue(dev, VIRTQUEUE_NUM, console_input);
1150 add_virtqueue(dev, VIRTQUEUE_NUM, console_output);
1152 verbose("device %u: console\n", ++devices.device_num);
1156 /*M:010 Inter-guest networking is an interesting area. Simplest is to have a
1157 * --sharenet=<name> option which opens or creates a named pipe. This can be
1158 * used to send packets to another guest in a 1:1 manner.
1160 * More sopisticated is to use one of the tools developed for project like UML
1163 * Faster is to do virtio bonding in kernel. Doing this 1:1 would be
1164 * completely generic ("here's my vring, attach to your vring") and would work
1165 * for any traffic. Of course, namespace and permissions issues need to be
1166 * dealt with. A more sophisticated "multi-channel" virtio_net.c could hide
1167 * multiple inter-guest channels behind one interface, although it would
1168 * require some manner of hotplugging new virtio channels.
1170 * Finally, we could implement a virtio network switch in the kernel. :*/
1172 static u32 str2ip(const char *ipaddr)
1176 if (sscanf(ipaddr, "%u.%u.%u.%u", &b[0], &b[1], &b[2], &b[3]) != 4)
1177 errx(1, "Failed to parse IP address '%s'", ipaddr);
1178 return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3];
1181 static void str2mac(const char *macaddr, unsigned char mac[6])
1184 if (sscanf(macaddr, "%02x:%02x:%02x:%02x:%02x:%02x",
1185 &m[0], &m[1], &m[2], &m[3], &m[4], &m[5]) != 6)
1186 errx(1, "Failed to parse mac address '%s'", macaddr);
1195 /* This code is "adapted" from libbridge: it attaches the Host end of the
1196 * network device to the bridge device specified by the command line.
1198 * This is yet another James Morris contribution (I'm an IP-level guy, so I
1199 * dislike bridging), and I just try not to break it. */
1200 static void add_to_bridge(int fd, const char *if_name, const char *br_name)
1206 errx(1, "must specify bridge name");
1208 ifidx = if_nametoindex(if_name);
1210 errx(1, "interface %s does not exist!", if_name);
1212 strncpy(ifr.ifr_name, br_name, IFNAMSIZ);
1213 ifr.ifr_name[IFNAMSIZ-1] = '\0';
1214 ifr.ifr_ifindex = ifidx;
1215 if (ioctl(fd, SIOCBRADDIF, &ifr) < 0)
1216 err(1, "can't add %s to bridge %s", if_name, br_name);
1219 /* This sets up the Host end of the network device with an IP address, brings
1220 * it up so packets will flow, the copies the MAC address into the hwaddr
1222 static void configure_device(int fd, const char *tapif, u32 ipaddr)
1225 struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr;
1227 memset(&ifr, 0, sizeof(ifr));
1228 strcpy(ifr.ifr_name, tapif);
1230 /* Don't read these incantations. Just cut & paste them like I did! */
1231 sin->sin_family = AF_INET;
1232 sin->sin_addr.s_addr = htonl(ipaddr);
1233 if (ioctl(fd, SIOCSIFADDR, &ifr) != 0)
1234 err(1, "Setting %s interface address", tapif);
1235 ifr.ifr_flags = IFF_UP;
1236 if (ioctl(fd, SIOCSIFFLAGS, &ifr) != 0)
1237 err(1, "Bringing interface %s up", tapif);
1240 static int get_tun_device(char tapif[IFNAMSIZ])
1245 /* Start with this zeroed. Messy but sure. */
1246 memset(&ifr, 0, sizeof(ifr));
1248 /* We open the /dev/net/tun device and tell it we want a tap device. A
1249 * tap device is like a tun device, only somehow different. To tell
1250 * the truth, I completely blundered my way through this code, but it
1252 netfd = open_or_die("/dev/net/tun", O_RDWR);
1253 ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
1254 strcpy(ifr.ifr_name, "tap%d");
1255 if (ioctl(netfd, TUNSETIFF, &ifr) != 0)
1256 err(1, "configuring /dev/net/tun");
1258 if (ioctl(netfd, TUNSETOFFLOAD,
1259 TUN_F_CSUM|TUN_F_TSO4|TUN_F_TSO6|TUN_F_TSO_ECN) != 0)
1260 err(1, "Could not set features for tun device");
1262 /* We don't need checksums calculated for packets coming in this
1263 * device: trust us! */
1264 ioctl(netfd, TUNSETNOCSUM, 1);
1266 memcpy(tapif, ifr.ifr_name, IFNAMSIZ);
1270 /*L:195 Our network is a Host<->Guest network. This can either use bridging or
1271 * routing, but the principle is the same: it uses the "tun" device to inject
1272 * packets into the Host as if they came in from a normal network card. We
1273 * just shunt packets between the Guest and the tun device. */
1274 static void setup_tun_net(char *arg)
1277 struct net_info *net_info = malloc(sizeof(*net_info));
1279 u32 ip = INADDR_ANY;
1280 bool bridging = false;
1281 char tapif[IFNAMSIZ], *p;
1282 struct virtio_net_config conf;
1284 net_info->tunfd = get_tun_device(tapif);
1286 /* First we create a new network device. */
1287 dev = new_device("net", VIRTIO_ID_NET);
1288 dev->priv = net_info;
1290 /* Network devices need a receive and a send queue, just like
1292 add_virtqueue(dev, VIRTQUEUE_NUM, net_input);
1293 add_virtqueue(dev, VIRTQUEUE_NUM, net_output);
1295 /* We need a socket to perform the magic network ioctls to bring up the
1296 * tap interface, connect to the bridge etc. Any socket will do! */
1297 ipfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
1299 err(1, "opening IP socket");
1301 /* If the command line was --tunnet=bridge:<name> do bridging. */
1302 if (!strncmp(BRIDGE_PFX, arg, strlen(BRIDGE_PFX))) {
1303 arg += strlen(BRIDGE_PFX);
1307 /* A mac address may follow the bridge name or IP address */
1308 p = strchr(arg, ':');
1310 str2mac(p+1, conf.mac);
1311 add_feature(dev, VIRTIO_NET_F_MAC);
1315 /* arg is now either an IP address or a bridge name */
1317 add_to_bridge(ipfd, tapif, arg);
1321 /* Set up the tun device. */
1322 configure_device(ipfd, tapif, ip);
1324 add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
1325 /* Expect Guest to handle everything except UFO */
1326 add_feature(dev, VIRTIO_NET_F_CSUM);
1327 add_feature(dev, VIRTIO_NET_F_GUEST_CSUM);
1328 add_feature(dev, VIRTIO_NET_F_GUEST_TSO4);
1329 add_feature(dev, VIRTIO_NET_F_GUEST_TSO6);
1330 add_feature(dev, VIRTIO_NET_F_GUEST_ECN);
1331 add_feature(dev, VIRTIO_NET_F_HOST_TSO4);
1332 add_feature(dev, VIRTIO_NET_F_HOST_TSO6);
1333 add_feature(dev, VIRTIO_NET_F_HOST_ECN);
1334 set_config(dev, sizeof(conf), &conf);
1336 /* We don't need the socket any more; setup is done. */
1339 devices.device_num++;
1342 verbose("device %u: tun %s attached to bridge: %s\n",
1343 devices.device_num, tapif, arg);
1345 verbose("device %u: tun %s: %s\n",
1346 devices.device_num, tapif, arg);
1349 /* Our block (disk) device should be really simple: the Guest asks for a block
1350 * number and we read or write that position in the file. Unfortunately, that
1351 * was amazingly slow: the Guest waits until the read is finished before
1352 * running anything else, even if it could have been doing useful work.
1354 * We could use async I/O, except it's reputed to suck so hard that characters
1355 * actually go missing from your code when you try to use it.
1357 * So we farm the I/O out to thread, and communicate with it via a pipe. */
1359 /* This hangs off device->priv. */
1362 /* The size of the file. */
1365 /* The file descriptor for the file. */
1368 /* IO thread listens on this file descriptor [0]. */
1371 /* IO thread writes to this file descriptor to mark it done, then
1372 * Launcher triggers interrupt to Guest. */
1379 * Remember that the block device is handled by a separate I/O thread. We head
1380 * straight into the core of that thread here:
1382 static void blk_request(struct virtqueue *vq)
1384 struct vblk_info *vblk = vq->dev->priv;
1385 unsigned int head, out_num, in_num, wlen;
1388 struct virtio_blk_outhdr *out;
1389 struct iovec iov[vq->vring.num];
1392 /* Get the next request. */
1393 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
1395 /* Every block request should contain at least one output buffer
1396 * (detailing the location on disk and the type of request) and one
1397 * input buffer (to hold the result). */
1398 if (out_num == 0 || in_num == 0)
1399 errx(1, "Bad virtblk cmd %u out=%u in=%u",
1400 head, out_num, in_num);
1402 out = convert(&iov[0], struct virtio_blk_outhdr);
1403 in = convert(&iov[out_num+in_num-1], u8);
1404 off = out->sector * 512;
1406 /* The block device implements "barriers", where the Guest indicates
1407 * that it wants all previous writes to occur before this write. We
1408 * don't have a way of asking our kernel to do a barrier, so we just
1409 * synchronize all the data in the file. Pretty poor, no? */
1410 if (out->type & VIRTIO_BLK_T_BARRIER)
1411 fdatasync(vblk->fd);
1413 /* In general the virtio block driver is allowed to try SCSI commands.
1414 * It'd be nice if we supported eject, for example, but we don't. */
1415 if (out->type & VIRTIO_BLK_T_SCSI_CMD) {
1416 fprintf(stderr, "Scsi commands unsupported\n");
1417 *in = VIRTIO_BLK_S_UNSUPP;
1419 } else if (out->type & VIRTIO_BLK_T_OUT) {
1422 /* Move to the right location in the block file. This can fail
1423 * if they try to write past end. */
1424 if (lseek64(vblk->fd, off, SEEK_SET) != off)
1425 err(1, "Bad seek to sector %llu", out->sector);
1427 ret = writev(vblk->fd, iov+1, out_num-1);
1428 verbose("WRITE to sector %llu: %i\n", out->sector, ret);
1430 /* Grr... Now we know how long the descriptor they sent was, we
1431 * make sure they didn't try to write over the end of the block
1432 * file (possibly extending it). */
1433 if (ret > 0 && off + ret > vblk->len) {
1434 /* Trim it back to the correct length */
1435 ftruncate64(vblk->fd, vblk->len);
1436 /* Die, bad Guest, die. */
1437 errx(1, "Write past end %llu+%u", off, ret);
1440 *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR);
1444 /* Move to the right location in the block file. This can fail
1445 * if they try to read past end. */
1446 if (lseek64(vblk->fd, off, SEEK_SET) != off)
1447 err(1, "Bad seek to sector %llu", out->sector);
1449 ret = readv(vblk->fd, iov+1, in_num-1);
1450 verbose("READ from sector %llu: %i\n", out->sector, ret);
1452 wlen = sizeof(*in) + ret;
1453 *in = VIRTIO_BLK_S_OK;
1456 *in = VIRTIO_BLK_S_IOERR;
1460 /* OK, so we noted that it was pretty poor to use an fdatasync as a
1461 * barrier. But Christoph Hellwig points out that we need a sync
1462 * *afterwards* as well: "Barriers specify no reordering to the front
1463 * or the back." And Jens Axboe confirmed it, so here we are: */
1464 if (out->type & VIRTIO_BLK_T_BARRIER)
1465 fdatasync(vblk->fd);
1467 add_used(vq, head, wlen);
1470 /*L:198 This actually sets up a virtual block device. */
1471 static void setup_block_file(const char *filename)
1474 struct vblk_info *vblk;
1475 struct virtio_blk_config conf;
1477 /* The device responds to return from I/O thread. */
1478 dev = new_device("block", VIRTIO_ID_BLOCK);
1480 /* The device has one virtqueue, where the Guest places requests. */
1481 add_virtqueue(dev, VIRTQUEUE_NUM, blk_request);
1483 /* Allocate the room for our own bookkeeping */
1484 vblk = dev->priv = malloc(sizeof(*vblk));
1486 /* First we open the file and store the length. */
1487 vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE);
1488 vblk->len = lseek64(vblk->fd, 0, SEEK_END);
1490 /* We support barriers. */
1491 add_feature(dev, VIRTIO_BLK_F_BARRIER);
1493 /* Tell Guest how many sectors this device has. */
1494 conf.capacity = cpu_to_le64(vblk->len / 512);
1496 /* Tell Guest not to put in too many descriptors at once: two are used
1497 * for the in and out elements. */
1498 add_feature(dev, VIRTIO_BLK_F_SEG_MAX);
1499 conf.seg_max = cpu_to_le32(VIRTQUEUE_NUM - 2);
1501 set_config(dev, sizeof(conf), &conf);
1503 verbose("device %u: virtblock %llu sectors\n",
1504 ++devices.device_num, le64_to_cpu(conf.capacity));
1511 /* Our random number generator device reads from /dev/random into the Guest's
1512 * input buffers. The usual case is that the Guest doesn't want random numbers
1513 * and so has no buffers although /dev/random is still readable, whereas
1514 * console is the reverse.
1516 * The same logic applies, however. */
1517 static void rng_input(struct virtqueue *vq)
1520 unsigned int head, in_num, out_num, totlen = 0;
1521 struct rng_info *rng_info = vq->dev->priv;
1522 struct iovec iov[vq->vring.num];
1524 /* First we need a buffer from the Guests's virtqueue. */
1525 head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
1527 errx(1, "Output buffers in rng?");
1529 /* This is why we convert to iovecs: the readv() call uses them, and so
1530 * it reads straight into the Guest's buffer. We loop to make sure we
1532 while (!iov_empty(iov, in_num)) {
1533 len = readv(rng_info->rfd, iov, in_num);
1535 err(1, "Read from /dev/random gave %i", len);
1536 iov_consume(iov, in_num, len);
1540 /* Tell the Guest about the new input. */
1541 add_used(vq, head, totlen);
1544 /* And this creates a "hardware" random number device for the Guest. */
1545 static void setup_rng(void)
1548 struct rng_info *rng_info = malloc(sizeof(*rng_info));
1550 rng_info->rfd = open_or_die("/dev/random", O_RDONLY);
1552 /* The device responds to return from I/O thread. */
1553 dev = new_device("rng", VIRTIO_ID_RNG);
1554 dev->priv = rng_info;
1556 /* The device has one virtqueue, where the Guest places inbufs. */
1557 add_virtqueue(dev, VIRTQUEUE_NUM, rng_input);
1559 verbose("device %u: rng\n", devices.device_num++);
1561 /* That's the end of device setup. */
1563 /*L:230 Reboot is pretty easy: clean up and exec() the Launcher afresh. */
1564 static void __attribute__((noreturn)) restart_guest(void)
1568 /* Since we don't track all open fds, we simply close everything beyond
1570 for (i = 3; i < FD_SETSIZE; i++)
1573 /* Reset all the devices (kills all threads). */
1576 execv(main_args[0], main_args);
1577 err(1, "Could not exec %s", main_args[0]);
1580 /*L:220 Finally we reach the core of the Launcher which runs the Guest, serves
1581 * its input and output, and finally, lays it to rest. */
1582 static void __attribute__((noreturn)) run_guest(void)
1585 unsigned long notify_addr;
1588 /* We read from the /dev/lguest device to run the Guest. */
1589 readval = pread(lguest_fd, ¬ify_addr,
1590 sizeof(notify_addr), cpu_id);
1592 /* One unsigned long means the Guest did HCALL_NOTIFY */
1593 if (readval == sizeof(notify_addr)) {
1594 verbose("Notify on address %#lx\n", notify_addr);
1595 handle_output(notify_addr);
1596 /* ENOENT means the Guest died. Reading tells us why. */
1597 } else if (errno == ENOENT) {
1598 char reason[1024] = { 0 };
1599 pread(lguest_fd, reason, sizeof(reason)-1, cpu_id);
1600 errx(1, "%s", reason);
1601 /* ERESTART means that we need to reboot the guest */
1602 } else if (errno == ERESTART) {
1604 /* Anything else means a bug or incompatible change. */
1606 err(1, "Running guest failed");
1610 * This is the end of the Launcher. The good news: we are over halfway
1611 * through! The bad news: the most fiendish part of the code still lies ahead
1614 * Are you ready? Take a deep breath and join me in the core of the Host, in
1618 static struct option opts[] = {
1619 { "verbose", 0, NULL, 'v' },
1620 { "tunnet", 1, NULL, 't' },
1621 { "block", 1, NULL, 'b' },
1622 { "rng", 0, NULL, 'r' },
1623 { "initrd", 1, NULL, 'i' },
1626 static void usage(void)
1628 errx(1, "Usage: lguest [--verbose] "
1629 "[--tunnet=(<ipaddr>:<macaddr>|bridge:<bridgename>:<macaddr>)\n"
1630 "|--block=<filename>|--initrd=<filename>]...\n"
1631 "<mem-in-mb> vmlinux [args...]");
1634 /*L:105 The main routine is where the real work begins: */
1635 int main(int argc, char *argv[])
1637 /* Memory, top-level pagetable, code startpoint and size of the
1638 * (optional) initrd. */
1639 unsigned long mem = 0, start, initrd_size = 0;
1640 /* Two temporaries. */
1642 /* The boot information for the Guest. */
1643 struct boot_params *boot;
1644 /* If they specify an initrd file to load. */
1645 const char *initrd_name = NULL;
1647 /* Save the args: we "reboot" by execing ourselves again. */
1650 /* First we initialize the device list. We keep a pointer to the last
1651 * device, and the next interrupt number to use for devices (1:
1652 * remember that 0 is used by the timer). */
1653 devices.lastdev = NULL;
1654 devices.next_irq = 1;
1657 /* We need to know how much memory so we can set up the device
1658 * descriptor and memory pages for the devices as we parse the command
1659 * line. So we quickly look through the arguments to find the amount
1661 for (i = 1; i < argc; i++) {
1662 if (argv[i][0] != '-') {
1663 mem = atoi(argv[i]) * 1024 * 1024;
1664 /* We start by mapping anonymous pages over all of
1665 * guest-physical memory range. This fills it with 0,
1666 * and ensures that the Guest won't be killed when it
1667 * tries to access it. */
1668 guest_base = map_zeroed_pages(mem / getpagesize()
1671 guest_max = mem + DEVICE_PAGES*getpagesize();
1672 devices.descpage = get_pages(1);
1677 /* The options are fairly straight-forward */
1678 while ((c = getopt_long(argc, argv, "v", opts, NULL)) != EOF) {
1684 setup_tun_net(optarg);
1687 setup_block_file(optarg);
1693 initrd_name = optarg;
1696 warnx("Unknown argument %s", argv[optind]);
1700 /* After the other arguments we expect memory and kernel image name,
1701 * followed by command line arguments for the kernel. */
1702 if (optind + 2 > argc)
1705 verbose("Guest base is at %p\n", guest_base);
1707 /* We always have a console device */
1710 /* Now we load the kernel */
1711 start = load_kernel(open_or_die(argv[optind+1], O_RDONLY));
1713 /* Boot information is stashed at physical address 0 */
1714 boot = from_guest_phys(0);
1716 /* Map the initrd image if requested (at top of physical memory) */
1718 initrd_size = load_initrd(initrd_name, mem);
1719 /* These are the location in the Linux boot header where the
1720 * start and size of the initrd are expected to be found. */
1721 boot->hdr.ramdisk_image = mem - initrd_size;
1722 boot->hdr.ramdisk_size = initrd_size;
1723 /* The bootloader type 0xFF means "unknown"; that's OK. */
1724 boot->hdr.type_of_loader = 0xFF;
1727 /* The Linux boot header contains an "E820" memory map: ours is a
1728 * simple, single region. */
1729 boot->e820_entries = 1;
1730 boot->e820_map[0] = ((struct e820entry) { 0, mem, E820_RAM });
1731 /* The boot header contains a command line pointer: we put the command
1732 * line after the boot header. */
1733 boot->hdr.cmd_line_ptr = to_guest_phys(boot + 1);
1734 /* We use a simple helper to copy the arguments separated by spaces. */
1735 concat((char *)(boot + 1), argv+optind+2);
1737 /* Boot protocol version: 2.07 supports the fields for lguest. */
1738 boot->hdr.version = 0x207;
1740 /* The hardware_subarch value of "1" tells the Guest it's an lguest. */
1741 boot->hdr.hardware_subarch = 1;
1743 /* Tell the entry path not to try to reload segment registers. */
1744 boot->hdr.loadflags |= KEEP_SEGMENTS;
1746 /* We tell the kernel to initialize the Guest: this returns the open
1747 * /dev/lguest file descriptor. */
1750 /* Ensure that we terminate if a child dies. */
1751 signal(SIGCHLD, kill_launcher);
1753 /* If we exit via err(), this kills all the threads, restores tty. */
1754 atexit(cleanup_devices);
1756 /* Finally, run the Guest. This doesn't return. */
1762 * Mastery is done: you now know everything I do.
1764 * But surely you have seen code, features and bugs in your wanderings which
1765 * you now yearn to attack? That is the real game, and I look forward to you
1766 * patching and forking lguest into the Your-Name-Here-visor.
1768 * Farewell, and good coding!