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 the
3 * virtual devices, then reads repeatedly from /dev/lguest to run the Guest.
5 #define _LARGEFILE64_SOURCE
15 #include <sys/param.h>
16 #include <sys/types.h>
23 #include <sys/socket.h>
24 #include <sys/ioctl.h>
27 #include <netinet/in.h>
29 #include <linux/sockios.h>
30 #include <linux/if_tun.h>
37 /*L:110 We can ignore the 30 include files we need for this program, but I do
38 * want to draw attention to the use of kernel-style types.
40 * As Linus said, "C is a Spartan language, and so should your naming be." I
41 * like these abbreviations and the header we need uses them, so we define them
44 typedef unsigned long long u64;
48 #include "linux/lguest_launcher.h"
49 #include "linux/pci_ids.h"
50 #include "linux/virtio_config.h"
51 #include "linux/virtio_net.h"
52 #include "linux/virtio_blk.h"
53 #include "linux/virtio_console.h"
54 #include "linux/virtio_ring.h"
55 #include "asm-x86/e820.h"
58 #define PAGE_PRESENT 0x7 /* Present, RW, Execute */
60 #define BRIDGE_PFX "bridge:"
62 #define SIOCBRADDIF 0x89a2 /* add interface to bridge */
64 /* We can have up to 256 pages for devices. */
65 #define DEVICE_PAGES 256
66 /* This fits nicely in a single 4096-byte page. */
67 #define VIRTQUEUE_NUM 127
69 /*L:120 verbose is both a global flag and a macro. The C preprocessor allows
70 * this, and although I wouldn't recommend it, it works quite nicely here. */
72 #define verbose(args...) \
73 do { if (verbose) printf(args); } while(0)
76 /* The pipe to send commands to the waker process */
78 /* The pointer to the start of guest memory. */
79 static void *guest_base;
80 /* The maximum guest physical address allowed, and maximum possible. */
81 static unsigned long guest_limit, guest_max;
83 /* This is our list of devices. */
86 /* Summary information about the devices in our list: ready to pass to
87 * select() to ask which need servicing.*/
91 /* Counter to assign interrupt numbers. */
92 unsigned int next_irq;
94 /* Counter to print out convenient device numbers. */
95 unsigned int device_num;
97 /* The descriptor page for the devices. */
100 /* The tail of the last descriptor. */
101 unsigned int desc_used;
103 /* A single linked list of devices. */
105 /* ... And an end pointer so we can easily append new devices */
106 struct device **lastdev;
109 /* The list of Guest devices, based on command line arguments. */
110 static struct device_list devices;
112 /* The device structure describes a single device. */
115 /* The linked-list pointer. */
118 /* The this device's descriptor, as mapped into the Guest. */
119 struct lguest_device_desc *desc;
121 /* The name of this device, for --verbose. */
124 /* If handle_input is set, it wants to be called when this file
125 * descriptor is ready. */
127 bool (*handle_input)(int fd, struct device *me);
129 /* Any queues attached to this device */
130 struct virtqueue *vq;
132 /* Device-specific data. */
136 /* The virtqueue structure describes a queue attached to a device. */
139 struct virtqueue *next;
141 /* Which device owns me. */
144 /* The configuration for this queue. */
145 struct lguest_vqconfig config;
147 /* The actual ring of buffers. */
150 /* Last available index we saw. */
153 /* The routine to call when the Guest pings us. */
154 void (*handle_output)(int fd, struct virtqueue *me);
157 /* Since guest is UP and we don't run at the same time, we don't need barriers.
158 * But I include them in the code in case others copy it. */
161 /* Convert an iovec element to the given type.
163 * This is a fairly ugly trick: we need to know the size of the type and
164 * alignment requirement to check the pointer is kosher. It's also nice to
165 * have the name of the type in case we report failure.
167 * Typing those three things all the time is cumbersome and error prone, so we
168 * have a macro which sets them all up and passes to the real function. */
169 #define convert(iov, type) \
170 ((type *)_convert((iov), sizeof(type), __alignof__(type), #type))
172 static void *_convert(struct iovec *iov, size_t size, size_t align,
175 if (iov->iov_len != size)
176 errx(1, "Bad iovec size %zu for %s", iov->iov_len, name);
177 if ((unsigned long)iov->iov_base % align != 0)
178 errx(1, "Bad alignment %p for %s", iov->iov_base, name);
179 return iov->iov_base;
182 /* The virtio configuration space is defined to be little-endian. x86 is
183 * little-endian too, but it's nice to be explicit so we have these helpers. */
184 #define cpu_to_le16(v16) (v16)
185 #define cpu_to_le32(v32) (v32)
186 #define cpu_to_le64(v64) (v64)
187 #define le16_to_cpu(v16) (v16)
188 #define le32_to_cpu(v32) (v32)
189 #define le64_to_cpu(v32) (v64)
191 /*L:100 The Launcher code itself takes us out into userspace, that scary place
192 * where pointers run wild and free! Unfortunately, like most userspace
193 * programs, it's quite boring (which is why everyone likes to hack on the
194 * kernel!). Perhaps if you make up an Lguest Drinking Game at this point, it
195 * will get you through this section. Or, maybe not.
197 * The Launcher sets up a big chunk of memory to be the Guest's "physical"
198 * memory and stores it in "guest_base". In other words, Guest physical ==
199 * Launcher virtual with an offset.
201 * This can be tough to get your head around, but usually it just means that we
202 * use these trivial conversion functions when the Guest gives us it's
203 * "physical" addresses: */
204 static void *from_guest_phys(unsigned long addr)
206 return guest_base + addr;
209 static unsigned long to_guest_phys(const void *addr)
211 return (addr - guest_base);
215 * Loading the Kernel.
217 * We start with couple of simple helper routines. open_or_die() avoids
218 * error-checking code cluttering the callers: */
219 static int open_or_die(const char *name, int flags)
221 int fd = open(name, flags);
223 err(1, "Failed to open %s", name);
227 /* map_zeroed_pages() takes a number of pages. */
228 static void *map_zeroed_pages(unsigned int num)
230 int fd = open_or_die("/dev/zero", O_RDONLY);
233 /* We use a private mapping (ie. if we write to the page, it will be
235 addr = mmap(NULL, getpagesize() * num,
236 PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0);
237 if (addr == MAP_FAILED)
238 err(1, "Mmaping %u pages of /dev/zero", num);
243 /* Get some more pages for a device. */
244 static void *get_pages(unsigned int num)
246 void *addr = from_guest_phys(guest_limit);
248 guest_limit += num * getpagesize();
249 if (guest_limit > guest_max)
250 errx(1, "Not enough memory for devices");
254 /* This routine is used to load the kernel or initrd. It tries mmap, but if
255 * that fails (Plan 9's kernel file isn't nicely aligned on page boundaries),
256 * it falls back to reading the memory in. */
257 static void map_at(int fd, void *addr, unsigned long offset, unsigned long len)
261 /* We map writable even though for some segments are marked read-only.
262 * The kernel really wants to be writable: it patches its own
265 * MAP_PRIVATE means that the page won't be copied until a write is
266 * done to it. This allows us to share untouched memory between
268 if (mmap(addr, len, PROT_READ|PROT_WRITE|PROT_EXEC,
269 MAP_FIXED|MAP_PRIVATE, fd, offset) != MAP_FAILED)
272 /* pread does a seek and a read in one shot: saves a few lines. */
273 r = pread(fd, addr, len, offset);
275 err(1, "Reading offset %lu len %lu gave %zi", offset, len, r);
278 /* This routine takes an open vmlinux image, which is in ELF, and maps it into
279 * the Guest memory. ELF = Embedded Linking Format, which is the format used
280 * by all modern binaries on Linux including the kernel.
282 * The ELF headers give *two* addresses: a physical address, and a virtual
283 * address. We use the physical address; the Guest will map itself to the
286 * We return the starting address. */
287 static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr)
289 Elf32_Phdr phdr[ehdr->e_phnum];
292 /* Sanity checks on the main ELF header: an x86 executable with a
293 * reasonable number of correctly-sized program headers. */
294 if (ehdr->e_type != ET_EXEC
295 || ehdr->e_machine != EM_386
296 || ehdr->e_phentsize != sizeof(Elf32_Phdr)
297 || ehdr->e_phnum < 1 || ehdr->e_phnum > 65536U/sizeof(Elf32_Phdr))
298 errx(1, "Malformed elf header");
300 /* An ELF executable contains an ELF header and a number of "program"
301 * headers which indicate which parts ("segments") of the program to
304 /* We read in all the program headers at once: */
305 if (lseek(elf_fd, ehdr->e_phoff, SEEK_SET) < 0)
306 err(1, "Seeking to program headers");
307 if (read(elf_fd, phdr, sizeof(phdr)) != sizeof(phdr))
308 err(1, "Reading program headers");
310 /* Try all the headers: there are usually only three. A read-only one,
311 * a read-write one, and a "note" section which isn't loadable. */
312 for (i = 0; i < ehdr->e_phnum; i++) {
313 /* If this isn't a loadable segment, we ignore it */
314 if (phdr[i].p_type != PT_LOAD)
317 verbose("Section %i: size %i addr %p\n",
318 i, phdr[i].p_memsz, (void *)phdr[i].p_paddr);
320 /* We map this section of the file at its physical address. */
321 map_at(elf_fd, from_guest_phys(phdr[i].p_paddr),
322 phdr[i].p_offset, phdr[i].p_filesz);
325 /* The entry point is given in the ELF header. */
326 return ehdr->e_entry;
329 /*L:160 Unfortunately the entire ELF image isn't compressed: the segments
330 * which need loading are extracted and compressed raw. This denies us the
331 * information we need to make a fully-general loader. */
332 static unsigned long unpack_bzimage(int fd)
336 /* A bzImage always gets loaded at physical address 1M. This is
337 * actually configurable as CONFIG_PHYSICAL_START, but as the comment
338 * there says, "Don't change this unless you know what you are doing".
340 void *img = from_guest_phys(0x100000);
342 /* gzdopen takes our file descriptor (carefully placed at the start of
343 * the GZIP header we found) and returns a gzFile. */
344 f = gzdopen(fd, "rb");
345 /* We read it into memory in 64k chunks until we hit the end. */
346 while ((ret = gzread(f, img + len, 65536)) > 0)
349 err(1, "reading image from bzImage");
351 verbose("Unpacked size %i addr %p\n", len, img);
353 /* The entry point for a bzImage is always the first byte */
354 return (unsigned long)img;
357 /*L:150 A bzImage, unlike an ELF file, is not meant to be loaded. You're
358 * supposed to jump into it and it will unpack itself. We can't do that
359 * because the Guest can't run the unpacking code, and adding features to
360 * lguest kills puppies, so we don't want to.
362 * The bzImage is formed by putting the decompressing code in front of the
363 * compressed kernel code. So we can simple scan through it looking for the
364 * first "gzip" header, and start decompressing from there. */
365 static unsigned long load_bzimage(int fd)
370 /* GZIP header is 0x1F 0x8B <method> <flags>... <compressed-by>. */
371 while (read(fd, &c, 1) == 1) {
387 /* Seek back to the start of the gzip header. */
388 lseek(fd, -10, SEEK_CUR);
389 /* One final check: "compressed under UNIX". */
393 return unpack_bzimage(fd);
396 errx(1, "Could not find kernel in bzImage");
399 /*L:140 Loading the kernel is easy when it's a "vmlinux", but most kernels
400 * come wrapped up in the self-decompressing "bzImage" format. With some funky
401 * coding, we can load those, too. */
402 static unsigned long load_kernel(int fd)
406 /* Read in the first few bytes. */
407 if (read(fd, &hdr, sizeof(hdr)) != sizeof(hdr))
408 err(1, "Reading kernel");
410 /* If it's an ELF file, it starts with "\177ELF" */
411 if (memcmp(hdr.e_ident, ELFMAG, SELFMAG) == 0)
412 return map_elf(fd, &hdr);
414 /* Otherwise we assume it's a bzImage, and try to unpack it */
415 return load_bzimage(fd);
418 /* This is a trivial little helper to align pages. Andi Kleen hated it because
419 * it calls getpagesize() twice: "it's dumb code."
421 * Kernel guys get really het up about optimization, even when it's not
422 * necessary. I leave this code as a reaction against that. */
423 static inline unsigned long page_align(unsigned long addr)
425 /* Add upwards and truncate downwards. */
426 return ((addr + getpagesize()-1) & ~(getpagesize()-1));
429 /*L:180 An "initial ram disk" is a disk image loaded into memory along with
430 * the kernel which the kernel can use to boot from without needing any
431 * drivers. Most distributions now use this as standard: the initrd contains
432 * the code to load the appropriate driver modules for the current machine.
434 * Importantly, James Morris works for RedHat, and Fedora uses initrds for its
435 * kernels. He sent me this (and tells me when I break it). */
436 static unsigned long load_initrd(const char *name, unsigned long mem)
442 ifd = open_or_die(name, O_RDONLY);
443 /* fstat() is needed to get the file size. */
444 if (fstat(ifd, &st) < 0)
445 err(1, "fstat() on initrd '%s'", name);
447 /* We map the initrd at the top of memory, but mmap wants it to be
448 * page-aligned, so we round the size up for that. */
449 len = page_align(st.st_size);
450 map_at(ifd, from_guest_phys(mem - len), 0, st.st_size);
451 /* Once a file is mapped, you can close the file descriptor. It's a
452 * little odd, but quite useful. */
454 verbose("mapped initrd %s size=%lu @ %p\n", name, len, (void*)mem-len);
456 /* We return the initrd size. */
460 /* Once we know how much memory we have, we can construct simple linear page
461 * tables which set virtual == physical which will get the Guest far enough
462 * into the boot to create its own.
464 * We lay them out of the way, just below the initrd (which is why we need to
466 static unsigned long setup_pagetables(unsigned long mem,
467 unsigned long initrd_size)
469 unsigned long *pgdir, *linear;
470 unsigned int mapped_pages, i, linear_pages;
471 unsigned int ptes_per_page = getpagesize()/sizeof(void *);
473 mapped_pages = mem/getpagesize();
475 /* Each PTE page can map ptes_per_page pages: how many do we need? */
476 linear_pages = (mapped_pages + ptes_per_page-1)/ptes_per_page;
478 /* We put the toplevel page directory page at the top of memory. */
479 pgdir = from_guest_phys(mem) - initrd_size - getpagesize();
481 /* Now we use the next linear_pages pages as pte pages */
482 linear = (void *)pgdir - linear_pages*getpagesize();
484 /* Linear mapping is easy: put every page's address into the mapping in
485 * order. PAGE_PRESENT contains the flags Present, Writable and
487 for (i = 0; i < mapped_pages; i++)
488 linear[i] = ((i * getpagesize()) | PAGE_PRESENT);
490 /* The top level points to the linear page table pages above. */
491 for (i = 0; i < mapped_pages; i += ptes_per_page) {
492 pgdir[i/ptes_per_page]
493 = ((to_guest_phys(linear) + i*sizeof(void *))
497 verbose("Linear mapping of %u pages in %u pte pages at %#lx\n",
498 mapped_pages, linear_pages, to_guest_phys(linear));
500 /* We return the top level (guest-physical) address: the kernel needs
501 * to know where it is. */
502 return to_guest_phys(pgdir);
505 /* Simple routine to roll all the commandline arguments together with spaces
507 static void concat(char *dst, char *args[])
509 unsigned int i, len = 0;
511 for (i = 0; args[i]; i++) {
512 strcpy(dst+len, args[i]);
513 strcat(dst+len, " ");
514 len += strlen(args[i]) + 1;
516 /* In case it's empty. */
520 /* This is where we actually tell the kernel to initialize the Guest. We saw
521 * the arguments it expects when we looked at initialize() in lguest_user.c:
522 * the base of guest "physical" memory, the top physical page to allow, the
523 * top level pagetable and the entry point for the Guest. */
524 static int tell_kernel(unsigned long pgdir, unsigned long start)
526 unsigned long args[] = { LHREQ_INITIALIZE,
527 (unsigned long)guest_base,
528 guest_limit / getpagesize(), pgdir, start };
531 verbose("Guest: %p - %p (%#lx)\n",
532 guest_base, guest_base + guest_limit, guest_limit);
533 fd = open_or_die("/dev/lguest", O_RDWR);
534 if (write(fd, args, sizeof(args)) < 0)
535 err(1, "Writing to /dev/lguest");
537 /* We return the /dev/lguest file descriptor to control this Guest */
542 static void add_device_fd(int fd)
544 FD_SET(fd, &devices.infds);
545 if (fd > devices.max_infd)
546 devices.max_infd = fd;
552 * With a console and network devices, we can have lots of input which we need
553 * to process. We could try to tell the kernel what file descriptors to watch,
554 * but handing a file descriptor mask through to the kernel is fairly icky.
556 * Instead, we fork off a process which watches the file descriptors and writes
557 * the LHREQ_BREAK command to the /dev/lguest filedescriptor to tell the Host
558 * loop to stop running the Guest. This causes it to return from the
559 * /dev/lguest read with -EAGAIN, where it will write to /dev/lguest to reset
560 * the LHREQ_BREAK and wake us up again.
562 * This, of course, is merely a different *kind* of icky.
564 static void wake_parent(int pipefd, int lguest_fd)
566 /* Add the pipe from the Launcher to the fdset in the device_list, so
567 * we watch it, too. */
568 add_device_fd(pipefd);
571 fd_set rfds = devices.infds;
572 unsigned long args[] = { LHREQ_BREAK, 1 };
574 /* Wait until input is ready from one of the devices. */
575 select(devices.max_infd+1, &rfds, NULL, NULL, NULL);
576 /* Is it a message from the Launcher? */
577 if (FD_ISSET(pipefd, &rfds)) {
579 /* If read() returns 0, it means the Launcher has
580 * exited. We silently follow. */
581 if (read(pipefd, &fd, sizeof(fd)) == 0)
583 /* Otherwise it's telling us to change what file
584 * descriptors we're to listen to. */
586 FD_SET(fd, &devices.infds);
588 FD_CLR(-fd - 1, &devices.infds);
589 } else /* Send LHREQ_BREAK command. */
590 write(lguest_fd, args, sizeof(args));
594 /* This routine just sets up a pipe to the Waker process. */
595 static int setup_waker(int lguest_fd)
597 int pipefd[2], child;
599 /* We create a pipe to talk to the waker, and also so it knows when the
600 * Launcher dies (and closes pipe). */
607 /* Close the "writing" end of our copy of the pipe */
609 wake_parent(pipefd[0], lguest_fd);
611 /* Close the reading end of our copy of the pipe. */
614 /* Here is the fd used to talk to the waker. */
621 * When the Guest sends DMA to us, it sends us an array of addresses and sizes.
622 * We need to make sure it's not trying to reach into the Launcher itself, so
623 * we have a convenient routine which check it and exits with an error message
624 * if something funny is going on:
626 static void *_check_pointer(unsigned long addr, unsigned int size,
629 /* We have to separately check addr and addr+size, because size could
630 * be huge and addr + size might wrap around. */
631 if (addr >= guest_limit || addr + size >= guest_limit)
632 errx(1, "%s:%i: Invalid address %#lx", __FILE__, line, addr);
633 /* We return a pointer for the caller's convenience, now we know it's
635 return from_guest_phys(addr);
637 /* A macro which transparently hands the line number to the real function. */
638 #define check_pointer(addr,size) _check_pointer(addr, size, __LINE__)
640 /* This function returns the next descriptor in the chain, or vq->vring.num. */
641 static unsigned next_desc(struct virtqueue *vq, unsigned int i)
645 /* If this descriptor says it doesn't chain, we're done. */
646 if (!(vq->vring.desc[i].flags & VRING_DESC_F_NEXT))
647 return vq->vring.num;
649 /* Check they're not leading us off end of descriptors. */
650 next = vq->vring.desc[i].next;
651 /* Make sure compiler knows to grab that: we don't want it changing! */
654 if (next >= vq->vring.num)
655 errx(1, "Desc next is %u", next);
660 /* This looks in the virtqueue and for the first available buffer, and converts
661 * it to an iovec for convenient access. Since descriptors consist of some
662 * number of output then some number of input descriptors, it's actually two
663 * iovecs, but we pack them into one and note how many of each there were.
665 * This function returns the descriptor number found, or vq->vring.num (which
666 * is never a valid descriptor number) if none was found. */
667 static unsigned get_vq_desc(struct virtqueue *vq,
669 unsigned int *out_num, unsigned int *in_num)
671 unsigned int i, head;
673 /* Check it isn't doing very strange things with descriptor numbers. */
674 if ((u16)(vq->vring.avail->idx - vq->last_avail_idx) > vq->vring.num)
675 errx(1, "Guest moved used index from %u to %u",
676 vq->last_avail_idx, vq->vring.avail->idx);
678 /* If there's nothing new since last we looked, return invalid. */
679 if (vq->vring.avail->idx == vq->last_avail_idx)
680 return vq->vring.num;
682 /* Grab the next descriptor number they're advertising, and increment
683 * the index we've seen. */
684 head = vq->vring.avail->ring[vq->last_avail_idx++ % 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;
695 /* Grab the first descriptor, and check it's OK. */
696 iov[*out_num + *in_num].iov_len = vq->vring.desc[i].len;
697 iov[*out_num + *in_num].iov_base
698 = check_pointer(vq->vring.desc[i].addr,
699 vq->vring.desc[i].len);
700 /* If this is an input descriptor, increment that count. */
701 if (vq->vring.desc[i].flags & VRING_DESC_F_WRITE)
704 /* If it's an output descriptor, they're all supposed
705 * to come before any input descriptors. */
707 errx(1, "Descriptor has out after in");
711 /* If we've got too many, that implies a descriptor loop. */
712 if (*out_num + *in_num > vq->vring.num)
713 errx(1, "Looped descriptor");
714 } while ((i = next_desc(vq, i)) != vq->vring.num);
719 /* Once we've used one of their buffers, we tell them about it. We'll then
720 * want to send them an interrupt, using trigger_irq(). */
721 static void add_used(struct virtqueue *vq, unsigned int head, int len)
723 struct vring_used_elem *used;
725 /* Get a pointer to the next entry in the used ring. */
726 used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num];
729 /* Make sure buffer is written before we update index. */
731 vq->vring.used->idx++;
734 /* This actually sends the interrupt for this virtqueue */
735 static void trigger_irq(int fd, struct virtqueue *vq)
737 unsigned long buf[] = { LHREQ_IRQ, vq->config.irq };
739 if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
742 /* Send the Guest an interrupt tell them we used something up. */
743 if (write(fd, buf, sizeof(buf)) != 0)
744 err(1, "Triggering irq %i", vq->config.irq);
747 /* And here's the combo meal deal. Supersize me! */
748 static void add_used_and_trigger(int fd, struct virtqueue *vq,
749 unsigned int head, int len)
751 add_used(vq, head, len);
755 /* Here is the input terminal setting we save, and the routine to restore them
756 * on exit so the user can see what they type next. */
757 static struct termios orig_term;
758 static void restore_term(void)
760 tcsetattr(STDIN_FILENO, TCSANOW, &orig_term);
763 /* We associate some data with the console for our exit hack. */
766 /* How many times have they hit ^C? */
768 /* When did they start? */
769 struct timeval start;
772 /* This is the routine which handles console input (ie. stdin). */
773 static bool handle_console_input(int fd, struct device *dev)
776 unsigned int head, in_num, out_num;
777 struct iovec iov[dev->vq->vring.num];
778 struct console_abort *abort = dev->priv;
780 /* First we need a console buffer from the Guests's input virtqueue. */
781 head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
783 /* If they're not ready for input, stop listening to this file
784 * descriptor. We'll start again once they add an input buffer. */
785 if (head == dev->vq->vring.num)
789 errx(1, "Output buffers in console in queue?");
791 /* This is why we convert to iovecs: the readv() call uses them, and so
792 * it reads straight into the Guest's buffer. */
793 len = readv(dev->fd, iov, in_num);
795 /* This implies that the console is closed, is /dev/null, or
796 * something went terribly wrong. */
797 warnx("Failed to get console input, ignoring console.");
798 /* Put the input terminal back. */
800 /* Remove callback from input vq, so it doesn't restart us. */
801 dev->vq->handle_output = NULL;
802 /* Stop listening to this fd: don't call us again. */
806 /* Tell the Guest about the new input. */
807 add_used_and_trigger(fd, dev->vq, head, len);
809 /* Three ^C within one second? Exit.
811 * This is such a hack, but works surprisingly well. Each ^C has to be
812 * in a buffer by itself, so they can't be too fast. But we check that
813 * we get three within about a second, so they can't be too slow. */
814 if (len == 1 && ((char *)iov[0].iov_base)[0] == 3) {
816 gettimeofday(&abort->start, NULL);
817 else if (abort->count == 3) {
819 gettimeofday(&now, NULL);
820 if (now.tv_sec <= abort->start.tv_sec+1) {
821 unsigned long args[] = { LHREQ_BREAK, 0 };
822 /* Close the fd so Waker will know it has to
825 /* Just in case waker is blocked in BREAK, send
827 write(fd, args, sizeof(args));
833 /* Any other key resets the abort counter. */
836 /* Everything went OK! */
840 /* Handling output for console is simple: we just get all the output buffers
841 * and write them to stdout. */
842 static void handle_console_output(int fd, struct virtqueue *vq)
844 unsigned int head, out, in;
846 struct iovec iov[vq->vring.num];
848 /* Keep getting output buffers from the Guest until we run out. */
849 while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) {
851 errx(1, "Input buffers in output queue?");
852 len = writev(STDOUT_FILENO, iov, out);
853 add_used_and_trigger(fd, vq, head, len);
857 /* Handling output for network is also simple: we get all the output buffers
858 * and write them (ignoring the first element) to this device's file descriptor
860 static void handle_net_output(int fd, struct virtqueue *vq)
862 unsigned int head, out, in;
864 struct iovec iov[vq->vring.num];
866 /* Keep getting output buffers from the Guest until we run out. */
867 while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) {
869 errx(1, "Input buffers in output queue?");
870 /* Check header, but otherwise ignore it (we said we supported
872 (void)convert(&iov[0], struct virtio_net_hdr);
873 len = writev(vq->dev->fd, iov+1, out-1);
874 add_used_and_trigger(fd, vq, head, len);
878 /* This is where we handle a packet coming in from the tun device to our
880 static bool handle_tun_input(int fd, struct device *dev)
882 unsigned int head, in_num, out_num;
884 struct iovec iov[dev->vq->vring.num];
885 struct virtio_net_hdr *hdr;
887 /* First we need a network buffer from the Guests's recv virtqueue. */
888 head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
889 if (head == dev->vq->vring.num) {
890 /* Now, it's expected that if we try to send a packet too
891 * early, the Guest won't be ready yet. Wait until the device
892 * status says it's ready. */
893 /* FIXME: Actually want DRIVER_ACTIVE here. */
894 if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK)
895 warn("network: no dma buffer!");
896 /* We'll turn this back on if input buffers are registered. */
899 errx(1, "Output buffers in network recv queue?");
901 /* First element is the header: we set it to 0 (no features). */
902 hdr = convert(&iov[0], struct virtio_net_hdr);
904 hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
906 /* Read the packet from the device directly into the Guest's buffer. */
907 len = readv(dev->fd, iov+1, in_num-1);
909 err(1, "reading network");
911 /* Tell the Guest about the new packet. */
912 add_used_and_trigger(fd, dev->vq, head, sizeof(*hdr) + len);
914 verbose("tun input packet len %i [%02x %02x] (%s)\n", len,
915 ((u8 *)iov[1].iov_base)[0], ((u8 *)iov[1].iov_base)[1],
916 head != dev->vq->vring.num ? "sent" : "discarded");
922 /* This callback ensures we try again, in case we stopped console or net
923 * delivery because Guest didn't have any buffers. */
924 static void enable_fd(int fd, struct virtqueue *vq)
926 add_device_fd(vq->dev->fd);
927 /* Tell waker to listen to it again */
928 write(waker_fd, &vq->dev->fd, sizeof(vq->dev->fd));
931 /* This is the generic routine we call when the Guest uses LHCALL_NOTIFY. */
932 static void handle_output(int fd, unsigned long addr)
935 struct virtqueue *vq;
937 /* Check each virtqueue. */
938 for (i = devices.dev; i; i = i->next) {
939 for (vq = i->vq; vq; vq = vq->next) {
940 if (vq->config.pfn == addr/getpagesize()
941 && vq->handle_output) {
942 verbose("Output to %s\n", vq->dev->name);
943 vq->handle_output(fd, vq);
949 /* Early console write is done using notify on a nul-terminated string
950 * in Guest memory. */
951 if (addr >= guest_limit)
952 errx(1, "Bad NOTIFY %#lx", addr);
954 write(STDOUT_FILENO, from_guest_phys(addr),
955 strnlen(from_guest_phys(addr), guest_limit - addr));
958 /* This is called when the waker wakes us up: check for incoming file
960 static void handle_input(int fd)
962 /* select() wants a zeroed timeval to mean "don't wait". */
963 struct timeval poll = { .tv_sec = 0, .tv_usec = 0 };
967 fd_set fds = devices.infds;
969 /* If nothing is ready, we're done. */
970 if (select(devices.max_infd+1, &fds, NULL, NULL, &poll) == 0)
973 /* Otherwise, call the device(s) which have readable
974 * file descriptors and a method of handling them. */
975 for (i = devices.dev; i; i = i->next) {
976 if (i->handle_input && FD_ISSET(i->fd, &fds)) {
978 if (i->handle_input(fd, i))
981 /* If handle_input() returns false, it means we
982 * should no longer service it. Networking and
983 * console do this when there's no input
984 * buffers to deliver into. Console also uses
985 * it when it discovers that stdin is
987 FD_CLR(i->fd, &devices.infds);
988 /* Tell waker to ignore it too, by sending a
989 * negative fd number (-1, since 0 is a valid
992 write(waker_fd, &dev_fd, sizeof(dev_fd));
1001 * All devices need a descriptor so the Guest knows it exists, and a "struct
1002 * device" so the Launcher can keep track of it. We have common helper
1003 * routines to allocate them.
1005 * This routine allocates a new "struct lguest_device_desc" from descriptor
1006 * table just above the Guest's normal memory. It returns a pointer to that
1008 static struct lguest_device_desc *new_dev_desc(u16 type)
1010 struct lguest_device_desc *d;
1012 /* We only have one page for all the descriptors. */
1013 if (devices.desc_used + sizeof(*d) > getpagesize())
1014 errx(1, "Too many devices");
1016 /* We don't need to set config_len or status: page is 0 already. */
1017 d = (void *)devices.descpage + devices.desc_used;
1019 devices.desc_used += sizeof(*d);
1024 /* Each device descriptor is followed by some configuration information.
1025 * The first byte is a "status" byte for the Guest to report what's happening.
1026 * After that are fields: u8 type, u8 len, [... len bytes...].
1028 * This routine adds a new field to an existing device's descriptor. It only
1029 * works for the last device, but that's OK because that's how we use it. */
1030 static void add_desc_field(struct device *dev, u8 type, u8 len, const void *c)
1032 /* This is the last descriptor, right? */
1033 assert(devices.descpage + devices.desc_used
1034 == (u8 *)(dev->desc + 1) + dev->desc->config_len);
1036 /* We only have one page of device descriptions. */
1037 if (devices.desc_used + 2 + len > getpagesize())
1038 errx(1, "Too many devices");
1040 /* Copy in the new config header: type then length. */
1041 devices.descpage[devices.desc_used++] = type;
1042 devices.descpage[devices.desc_used++] = len;
1043 memcpy(devices.descpage + devices.desc_used, c, len);
1044 devices.desc_used += len;
1046 /* Update the device descriptor length: two byte head then data. */
1047 dev->desc->config_len += 2 + len;
1050 /* This routine adds a virtqueue to a device. We specify how many descriptors
1051 * the virtqueue is to have. */
1052 static void add_virtqueue(struct device *dev, unsigned int num_descs,
1053 void (*handle_output)(int fd, struct virtqueue *me))
1056 struct virtqueue **i, *vq = malloc(sizeof(*vq));
1059 /* First we need some pages for this virtqueue. */
1060 pages = (vring_size(num_descs) + getpagesize() - 1) / getpagesize();
1061 p = get_pages(pages);
1063 /* Initialize the configuration. */
1064 vq->config.num = num_descs;
1065 vq->config.irq = devices.next_irq++;
1066 vq->config.pfn = to_guest_phys(p) / getpagesize();
1068 /* Initialize the vring. */
1069 vring_init(&vq->vring, num_descs, p);
1071 /* Add the configuration information to this device's descriptor. */
1072 add_desc_field(dev, VIRTIO_CONFIG_F_VIRTQUEUE,
1073 sizeof(vq->config), &vq->config);
1075 /* Add to tail of list, so dev->vq is first vq, dev->vq->next is
1077 for (i = &dev->vq; *i; i = &(*i)->next);
1080 /* Link virtqueue back to device. */
1083 /* Set up handler. */
1084 vq->handle_output = handle_output;
1086 vq->vring.used->flags = VRING_USED_F_NO_NOTIFY;
1089 /* This routine does all the creation and setup of a new device, including
1090 * caling new_dev_desc() to allocate the descriptor and device memory. */
1091 static struct device *new_device(const char *name, u16 type, int fd,
1092 bool (*handle_input)(int, struct device *))
1094 struct device *dev = malloc(sizeof(*dev));
1096 /* Append to device list. Prepending to a single-linked list is
1097 * easier, but the user expects the devices to be arranged on the bus
1098 * in command-line order. The first network device on the command line
1099 * is eth0, the first block device /dev/lgba, etc. */
1100 *devices.lastdev = dev;
1102 devices.lastdev = &dev->next;
1104 /* Now we populate the fields one at a time. */
1106 /* If we have an input handler for this file descriptor, then we add it
1107 * to the device_list's fdset and maxfd. */
1109 add_device_fd(dev->fd);
1110 dev->desc = new_dev_desc(type);
1111 dev->handle_input = handle_input;
1116 /* Our first setup routine is the console. It's a fairly simple device, but
1117 * UNIX tty handling makes it uglier than it could be. */
1118 static void setup_console(void)
1122 /* If we can save the initial standard input settings... */
1123 if (tcgetattr(STDIN_FILENO, &orig_term) == 0) {
1124 struct termios term = orig_term;
1125 /* Then we turn off echo, line buffering and ^C etc. We want a
1126 * raw input stream to the Guest. */
1127 term.c_lflag &= ~(ISIG|ICANON|ECHO);
1128 tcsetattr(STDIN_FILENO, TCSANOW, &term);
1129 /* If we exit gracefully, the original settings will be
1130 * restored so the user can see what they're typing. */
1131 atexit(restore_term);
1134 dev = new_device("console", VIRTIO_ID_CONSOLE,
1135 STDIN_FILENO, handle_console_input);
1136 /* We store the console state in dev->priv, and initialize it. */
1137 dev->priv = malloc(sizeof(struct console_abort));
1138 ((struct console_abort *)dev->priv)->count = 0;
1140 /* The console needs two virtqueues: the input then the output. When
1141 * they put something the input queue, we make sure we're listening to
1142 * stdin. When they put something in the output queue, we write it to
1144 add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd);
1145 add_virtqueue(dev, VIRTQUEUE_NUM, handle_console_output);
1147 verbose("device %u: console\n", devices.device_num++);
1151 /*M:010 Inter-guest networking is an interesting area. Simplest is to have a
1152 * --sharenet=<name> option which opens or creates a named pipe. This can be
1153 * used to send packets to another guest in a 1:1 manner.
1155 * More sopisticated is to use one of the tools developed for project like UML
1158 * Faster is to do virtio bonding in kernel. Doing this 1:1 would be
1159 * completely generic ("here's my vring, attach to your vring") and would work
1160 * for any traffic. Of course, namespace and permissions issues need to be
1161 * dealt with. A more sophisticated "multi-channel" virtio_net.c could hide
1162 * multiple inter-guest channels behind one interface, although it would
1163 * require some manner of hotplugging new virtio channels.
1165 * Finally, we could implement a virtio network switch in the kernel. :*/
1167 static u32 str2ip(const char *ipaddr)
1169 unsigned int byte[4];
1171 sscanf(ipaddr, "%u.%u.%u.%u", &byte[0], &byte[1], &byte[2], &byte[3]);
1172 return (byte[0] << 24) | (byte[1] << 16) | (byte[2] << 8) | byte[3];
1175 /* This code is "adapted" from libbridge: it attaches the Host end of the
1176 * network device to the bridge device specified by the command line.
1178 * This is yet another James Morris contribution (I'm an IP-level guy, so I
1179 * dislike bridging), and I just try not to break it. */
1180 static void add_to_bridge(int fd, const char *if_name, const char *br_name)
1186 errx(1, "must specify bridge name");
1188 ifidx = if_nametoindex(if_name);
1190 errx(1, "interface %s does not exist!", if_name);
1192 strncpy(ifr.ifr_name, br_name, IFNAMSIZ);
1193 ifr.ifr_ifindex = ifidx;
1194 if (ioctl(fd, SIOCBRADDIF, &ifr) < 0)
1195 err(1, "can't add %s to bridge %s", if_name, br_name);
1198 /* This sets up the Host end of the network device with an IP address, brings
1199 * it up so packets will flow, the copies the MAC address into the hwaddr
1201 static void configure_device(int fd, const char *devname, u32 ipaddr,
1202 unsigned char hwaddr[6])
1205 struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr;
1207 /* Don't read these incantations. Just cut & paste them like I did! */
1208 memset(&ifr, 0, sizeof(ifr));
1209 strcpy(ifr.ifr_name, devname);
1210 sin->sin_family = AF_INET;
1211 sin->sin_addr.s_addr = htonl(ipaddr);
1212 if (ioctl(fd, SIOCSIFADDR, &ifr) != 0)
1213 err(1, "Setting %s interface address", devname);
1214 ifr.ifr_flags = IFF_UP;
1215 if (ioctl(fd, SIOCSIFFLAGS, &ifr) != 0)
1216 err(1, "Bringing interface %s up", devname);
1218 /* SIOC stands for Socket I/O Control. G means Get (vs S for Set
1219 * above). IF means Interface, and HWADDR is hardware address.
1221 if (ioctl(fd, SIOCGIFHWADDR, &ifr) != 0)
1222 err(1, "getting hw address for %s", devname);
1223 memcpy(hwaddr, ifr.ifr_hwaddr.sa_data, 6);
1226 /*L:195 Our network is a Host<->Guest network. This can either use bridging or
1227 * routing, but the principle is the same: it uses the "tun" device to inject
1228 * packets into the Host as if they came in from a normal network card. We
1229 * just shunt packets between the Guest and the tun device. */
1230 static void setup_tun_net(const char *arg)
1236 const char *br_name = NULL;
1239 /* We open the /dev/net/tun device and tell it we want a tap device. A
1240 * tap device is like a tun device, only somehow different. To tell
1241 * the truth, I completely blundered my way through this code, but it
1243 netfd = open_or_die("/dev/net/tun", O_RDWR);
1244 memset(&ifr, 0, sizeof(ifr));
1245 ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
1246 strcpy(ifr.ifr_name, "tap%d");
1247 if (ioctl(netfd, TUNSETIFF, &ifr) != 0)
1248 err(1, "configuring /dev/net/tun");
1249 /* We don't need checksums calculated for packets coming in this
1250 * device: trust us! */
1251 ioctl(netfd, TUNSETNOCSUM, 1);
1253 /* First we create a new network device. */
1254 dev = new_device("net", VIRTIO_ID_NET, netfd, handle_tun_input);
1256 /* Network devices need a receive and a send queue, just like
1258 add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd);
1259 add_virtqueue(dev, VIRTQUEUE_NUM, handle_net_output);
1261 /* We need a socket to perform the magic network ioctls to bring up the
1262 * tap interface, connect to the bridge etc. Any socket will do! */
1263 ipfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
1265 err(1, "opening IP socket");
1267 /* If the command line was --tunnet=bridge:<name> do bridging. */
1268 if (!strncmp(BRIDGE_PFX, arg, strlen(BRIDGE_PFX))) {
1270 br_name = arg + strlen(BRIDGE_PFX);
1271 add_to_bridge(ipfd, ifr.ifr_name, br_name);
1272 } else /* It is an IP address to set up the device with */
1275 /* Set up the tun device, and get the mac address for the interface. */
1276 configure_device(ipfd, ifr.ifr_name, ip, hwaddr);
1278 /* Tell Guest what MAC address to use. */
1279 add_desc_field(dev, VIRTIO_CONFIG_NET_MAC_F, sizeof(hwaddr), hwaddr);
1281 /* We don't seed the socket any more; setup is done. */
1284 verbose("device %u: tun net %u.%u.%u.%u\n",
1285 devices.device_num++,
1286 (u8)(ip>>24),(u8)(ip>>16),(u8)(ip>>8),(u8)ip);
1288 verbose("attached to bridge: %s\n", br_name);
1295 * Serving a block device is really easy: the Guest asks for a block number and
1296 * we read or write that position in the file.
1298 * Unfortunately, this is amazingly slow: the Guest waits until the read is
1299 * finished before running anything else, even if it could be doing useful
1300 * work. We could use async I/O, except it's reputed to suck so hard that
1301 * characters actually go missing from your code when you try to use it.
1303 * So we farm the I/O out to thread, and communicate with it via a pipe. */
1305 /* This hangs off device->priv, with the data. */
1308 /* The size of the file. */
1311 /* The file descriptor for the file. */
1314 /* IO thread listens on this file descriptor [0]. */
1317 /* IO thread writes to this file descriptor to mark it done, then
1318 * Launcher triggers interrupt to Guest. */
1322 /* This is the core of the I/O thread. It returns true if it did something. */
1323 static bool service_io(struct device *dev)
1325 struct vblk_info *vblk = dev->priv;
1326 unsigned int head, out_num, in_num, wlen;
1328 struct virtio_blk_inhdr *in;
1329 struct virtio_blk_outhdr *out;
1330 struct iovec iov[dev->vq->vring.num];
1333 head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
1334 if (head == dev->vq->vring.num)
1337 if (out_num == 0 || in_num == 0)
1338 errx(1, "Bad virtblk cmd %u out=%u in=%u",
1339 head, out_num, in_num);
1341 out = convert(&iov[0], struct virtio_blk_outhdr);
1342 in = convert(&iov[out_num+in_num-1], struct virtio_blk_inhdr);
1343 off = out->sector * 512;
1345 /* This is how we implement barriers. Pretty poor, no? */
1346 if (out->type & VIRTIO_BLK_T_BARRIER)
1347 fdatasync(vblk->fd);
1349 if (out->type & VIRTIO_BLK_T_SCSI_CMD) {
1350 fprintf(stderr, "Scsi commands unsupported\n");
1351 in->status = VIRTIO_BLK_S_UNSUPP;
1353 } else if (out->type & VIRTIO_BLK_T_OUT) {
1356 /* Move to the right location in the block file. This can fail
1357 * if they try to write past end. */
1358 if (lseek64(vblk->fd, off, SEEK_SET) != off)
1359 err(1, "Bad seek to sector %llu", out->sector);
1361 ret = writev(vblk->fd, iov+1, out_num-1);
1362 verbose("WRITE to sector %llu: %i\n", out->sector, ret);
1364 /* Grr... Now we know how long the descriptor they sent was, we
1365 * make sure they didn't try to write over the end of the block
1366 * file (possibly extending it). */
1367 if (ret > 0 && off + ret > vblk->len) {
1368 /* Trim it back to the correct length */
1369 ftruncate64(vblk->fd, vblk->len);
1370 /* Die, bad Guest, die. */
1371 errx(1, "Write past end %llu+%u", off, ret);
1374 in->status = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR);
1378 /* Move to the right location in the block file. This can fail
1379 * if they try to read past end. */
1380 if (lseek64(vblk->fd, off, SEEK_SET) != off)
1381 err(1, "Bad seek to sector %llu", out->sector);
1383 ret = readv(vblk->fd, iov+1, in_num-1);
1384 verbose("READ from sector %llu: %i\n", out->sector, ret);
1386 wlen = sizeof(in) + ret;
1387 in->status = VIRTIO_BLK_S_OK;
1390 in->status = VIRTIO_BLK_S_IOERR;
1394 /* We can't trigger an IRQ, because we're not the Launcher. It does
1395 * that when we tell it we're done. */
1396 add_used(dev->vq, head, wlen);
1400 /* This is the thread which actually services the I/O. */
1401 static int io_thread(void *_dev)
1403 struct device *dev = _dev;
1404 struct vblk_info *vblk = dev->priv;
1407 /* Close other side of workpipe so we get 0 read when main dies. */
1408 close(vblk->workpipe[1]);
1409 /* Close the other side of the done_fd pipe. */
1412 /* When this read fails, it means Launcher died, so we follow. */
1413 while (read(vblk->workpipe[0], &c, 1) == 1) {
1414 /* We acknowledge each request immediately, to reduce latency,
1415 * rather than waiting until we've done them all. I haven't
1416 * measured to see if it makes any difference. */
1417 while (service_io(dev))
1418 write(vblk->done_fd, &c, 1);
1423 /* When the thread says some I/O is done, we interrupt the Guest. */
1424 static bool handle_io_finish(int fd, struct device *dev)
1428 /* If child died, presumably it printed message. */
1429 if (read(dev->fd, &c, 1) != 1)
1432 /* It did some work, so trigger the irq. */
1433 trigger_irq(fd, dev->vq);
1437 /* When the Guest submits some I/O, we wake the I/O thread. */
1438 static void handle_virtblk_output(int fd, struct virtqueue *vq)
1440 struct vblk_info *vblk = vq->dev->priv;
1443 /* Wake up I/O thread and tell it to go to work! */
1444 if (write(vblk->workpipe[1], &c, 1) != 1)
1445 /* Presumably it indicated why it died. */
1449 /* This creates a virtual block device. */
1450 static void setup_block_file(const char *filename)
1454 struct vblk_info *vblk;
1459 /* This is the pipe the I/O thread will use to tell us I/O is done. */
1462 /* The device responds to return from I/O thread. */
1463 dev = new_device("block", VIRTIO_ID_BLOCK, p[0], handle_io_finish);
1465 /* The device has a virtqueue. */
1466 add_virtqueue(dev, VIRTQUEUE_NUM, handle_virtblk_output);
1468 /* Allocate the room for our own bookkeeping */
1469 vblk = dev->priv = malloc(sizeof(*vblk));
1471 /* First we open the file and store the length. */
1472 vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE);
1473 vblk->len = lseek64(vblk->fd, 0, SEEK_END);
1475 /* Tell Guest how many sectors this device has. */
1476 cap = cpu_to_le64(vblk->len / 512);
1477 add_desc_field(dev, VIRTIO_CONFIG_BLK_F_CAPACITY, sizeof(cap), &cap);
1479 /* Tell Guest not to put in too many descriptors at once: two are used
1480 * for the in and out elements. */
1481 val = cpu_to_le32(VIRTQUEUE_NUM - 2);
1482 add_desc_field(dev, VIRTIO_CONFIG_BLK_F_SEG_MAX, sizeof(val), &val);
1484 /* The I/O thread writes to this end of the pipe when done. */
1485 vblk->done_fd = p[1];
1487 /* This is how we tell the I/O thread about more work. */
1488 pipe(vblk->workpipe);
1490 /* Create stack for thread and run it */
1491 stack = malloc(32768);
1492 if (clone(io_thread, stack + 32768, CLONE_VM, dev) == -1)
1493 err(1, "Creating clone");
1495 /* We don't need to keep the I/O thread's end of the pipes open. */
1496 close(vblk->done_fd);
1497 close(vblk->workpipe[0]);
1499 verbose("device %u: virtblock %llu sectors\n",
1500 devices.device_num, cap);
1502 /* That's the end of device setup. */
1504 /*L:220 Finally we reach the core of the Launcher, which runs the Guest, serves
1505 * its input and output, and finally, lays it to rest. */
1506 static void __attribute__((noreturn)) run_guest(int lguest_fd)
1509 unsigned long args[] = { LHREQ_BREAK, 0 };
1510 unsigned long notify_addr;
1513 /* We read from the /dev/lguest device to run the Guest. */
1514 readval = read(lguest_fd, ¬ify_addr, sizeof(notify_addr));
1516 /* One unsigned long means the Guest did HCALL_NOTIFY */
1517 if (readval == sizeof(notify_addr)) {
1518 verbose("Notify on address %#lx\n", notify_addr);
1519 handle_output(lguest_fd, notify_addr);
1521 /* ENOENT means the Guest died. Reading tells us why. */
1522 } else if (errno == ENOENT) {
1523 char reason[1024] = { 0 };
1524 read(lguest_fd, reason, sizeof(reason)-1);
1525 errx(1, "%s", reason);
1526 /* EAGAIN means the waker wanted us to look at some input.
1527 * Anything else means a bug or incompatible change. */
1528 } else if (errno != EAGAIN)
1529 err(1, "Running guest failed");
1531 /* Service input, then unset the BREAK which releases
1533 handle_input(lguest_fd);
1534 if (write(lguest_fd, args, sizeof(args)) < 0)
1535 err(1, "Resetting break");
1539 * This is the end of the Launcher.
1541 * But wait! We've seen I/O from the Launcher, and we've seen I/O from the
1542 * Drivers. If we were to see the Host kernel I/O code, our understanding
1543 * would be complete... :*/
1545 static struct option opts[] = {
1546 { "verbose", 0, NULL, 'v' },
1547 { "tunnet", 1, NULL, 't' },
1548 { "block", 1, NULL, 'b' },
1549 { "initrd", 1, NULL, 'i' },
1552 static void usage(void)
1554 errx(1, "Usage: lguest [--verbose] "
1555 "[--tunnet=(<ipaddr>|bridge:<bridgename>)\n"
1556 "|--block=<filename>|--initrd=<filename>]...\n"
1557 "<mem-in-mb> vmlinux [args...]");
1560 /*L:105 The main routine is where the real work begins: */
1561 int main(int argc, char *argv[])
1563 /* Memory, top-level pagetable, code startpoint and size of the
1564 * (optional) initrd. */
1565 unsigned long mem = 0, pgdir, start, initrd_size = 0;
1566 /* A temporary and the /dev/lguest file descriptor. */
1567 int i, c, lguest_fd;
1568 /* The boot information for the Guest. */
1570 /* If they specify an initrd file to load. */
1571 const char *initrd_name = NULL;
1573 /* First we initialize the device list. Since console and network
1574 * device receive input from a file descriptor, we keep an fdset
1575 * (infds) and the maximum fd number (max_infd) with the head of the
1576 * list. We also keep a pointer to the last device, for easy appending
1577 * to the list. Finally, we keep the next interrupt number to hand out
1578 * (1: remember that 0 is used by the timer). */
1579 FD_ZERO(&devices.infds);
1580 devices.max_infd = -1;
1581 devices.lastdev = &devices.dev;
1582 devices.next_irq = 1;
1584 /* We need to know how much memory so we can set up the device
1585 * descriptor and memory pages for the devices as we parse the command
1586 * line. So we quickly look through the arguments to find the amount
1588 for (i = 1; i < argc; i++) {
1589 if (argv[i][0] != '-') {
1590 mem = atoi(argv[i]) * 1024 * 1024;
1591 /* We start by mapping anonymous pages over all of
1592 * guest-physical memory range. This fills it with 0,
1593 * and ensures that the Guest won't be killed when it
1594 * tries to access it. */
1595 guest_base = map_zeroed_pages(mem / getpagesize()
1598 guest_max = mem + DEVICE_PAGES*getpagesize();
1599 devices.descpage = get_pages(1);
1604 /* The options are fairly straight-forward */
1605 while ((c = getopt_long(argc, argv, "v", opts, NULL)) != EOF) {
1611 setup_tun_net(optarg);
1614 setup_block_file(optarg);
1617 initrd_name = optarg;
1620 warnx("Unknown argument %s", argv[optind]);
1624 /* After the other arguments we expect memory and kernel image name,
1625 * followed by command line arguments for the kernel. */
1626 if (optind + 2 > argc)
1629 verbose("Guest base is at %p\n", guest_base);
1631 /* We always have a console device */
1634 /* Now we load the kernel */
1635 start = load_kernel(open_or_die(argv[optind+1], O_RDONLY));
1637 /* Boot information is stashed at physical address 0 */
1638 boot = from_guest_phys(0);
1640 /* Map the initrd image if requested (at top of physical memory) */
1642 initrd_size = load_initrd(initrd_name, mem);
1643 /* These are the location in the Linux boot header where the
1644 * start and size of the initrd are expected to be found. */
1645 *(unsigned long *)(boot+0x218) = mem - initrd_size;
1646 *(unsigned long *)(boot+0x21c) = initrd_size;
1647 /* The bootloader type 0xFF means "unknown"; that's OK. */
1648 *(unsigned char *)(boot+0x210) = 0xFF;
1651 /* Set up the initial linear pagetables, starting below the initrd. */
1652 pgdir = setup_pagetables(mem, initrd_size);
1654 /* The Linux boot header contains an "E820" memory map: ours is a
1655 * simple, single region. */
1656 *(char*)(boot+E820NR) = 1;
1657 *((struct e820entry *)(boot+E820MAP))
1658 = ((struct e820entry) { 0, mem, E820_RAM });
1659 /* The boot header contains a command line pointer: we put the command
1660 * line after the boot header (at address 4096) */
1661 *(u32 *)(boot + 0x228) = 4096;
1662 concat(boot + 4096, argv+optind+2);
1664 /* Boot protocol version: 2.07 supports the fields for lguest. */
1665 *(u16 *)(boot + 0x206) = 0x207;
1667 /* The hardware_subarch value of "1" tells the Guest it's an lguest. */
1668 *(u32 *)(boot + 0x23c) = 1;
1670 /* Set bit 6 of the loadflags (aka. KEEP_SEGMENTS) so the entry path
1671 * does not try to reload segment registers. */
1672 *(u8 *)(boot + 0x211) |= (1 << 6);
1674 /* We tell the kernel to initialize the Guest: this returns the open
1675 * /dev/lguest file descriptor. */
1676 lguest_fd = tell_kernel(pgdir, start);
1678 /* We fork off a child process, which wakes the Launcher whenever one
1679 * of the input file descriptors needs attention. Otherwise we would
1680 * run the Guest until it tries to output something. */
1681 waker_fd = setup_waker(lguest_fd);
1683 /* Finally, run the Guest. This doesn't return. */
1684 run_guest(lguest_fd);
1689 * Mastery is done: you now know everything I do.
1691 * But surely you have seen code, features and bugs in your wanderings which
1692 * you now yearn to attack? That is the real game, and I look forward to you
1693 * patching and forking lguest into the Your-Name-Here-visor.
1695 * Farewell, and good coding!