/*P:100 This is the Launcher code, a simple program which lays out the * "physical" memory for the new Guest by mapping the kernel image and * the virtual devices, then opens /dev/lguest to tell the kernel * about the Guest and control it. :*/ #define _LARGEFILE64_SOURCE #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "linux/lguest_launcher.h" #include "linux/virtio_config.h" #include "linux/virtio_net.h" #include "linux/virtio_blk.h" #include "linux/virtio_console.h" #include "linux/virtio_rng.h" #include "linux/virtio_ring.h" #include "asm/bootparam.h" /*L:110 We can ignore the 39 include files we need for this program, but I do * want to draw attention to the use of kernel-style types. * * As Linus said, "C is a Spartan language, and so should your naming be." I * like these abbreviations, so we define them here. Note that u64 is always * unsigned long long, which works on all Linux systems: this means that we can * use %llu in printf for any u64. */ typedef unsigned long long u64; typedef uint32_t u32; typedef uint16_t u16; typedef uint8_t u8; /*:*/ #define PAGE_PRESENT 0x7 /* Present, RW, Execute */ #define NET_PEERNUM 1 #define BRIDGE_PFX "bridge:" #ifndef SIOCBRADDIF #define SIOCBRADDIF 0x89a2 /* add interface to bridge */ #endif /* We can have up to 256 pages for devices. */ #define DEVICE_PAGES 256 /* This will occupy 3 pages: it must be a power of 2. */ #define VIRTQUEUE_NUM 256 /*L:120 verbose is both a global flag and a macro. The C preprocessor allows * this, and although I wouldn't recommend it, it works quite nicely here. */ static bool verbose; #define verbose(args...) \ do { if (verbose) printf(args); } while(0) /*:*/ /* File descriptors for the Waker. */ struct { int pipe[2]; int lguest_fd; } waker_fds; /* The pointer to the start of guest memory. */ static void *guest_base; /* The maximum guest physical address allowed, and maximum possible. */ static unsigned long guest_limit, guest_max; /* The pipe for signal hander to write to. */ static int timeoutpipe[2]; static unsigned int timeout_usec = 500; /* a per-cpu variable indicating whose vcpu is currently running */ static unsigned int __thread cpu_id; /* This is our list of devices. */ struct device_list { /* Summary information about the devices in our list: ready to pass to * select() to ask which need servicing.*/ fd_set infds; int max_infd; /* Counter to assign interrupt numbers. */ unsigned int next_irq; /* Counter to print out convenient device numbers. */ unsigned int device_num; /* The descriptor page for the devices. */ u8 *descpage; /* A single linked list of devices. */ struct device *dev; /* And a pointer to the last device for easy append and also for * configuration appending. */ struct device *lastdev; }; /* The list of Guest devices, based on command line arguments. */ static struct device_list devices; /* The device structure describes a single device. */ struct device { /* The linked-list pointer. */ struct device *next; /* The this device's descriptor, as mapped into the Guest. */ struct lguest_device_desc *desc; /* The name of this device, for --verbose. */ const char *name; /* If handle_input is set, it wants to be called when this file * descriptor is ready. */ int fd; bool (*handle_input)(int fd, struct device *me); /* Any queues attached to this device */ struct virtqueue *vq; /* Handle status being finalized (ie. feature bits stable). */ void (*ready)(struct device *me); /* Device-specific data. */ void *priv; }; /* The virtqueue structure describes a queue attached to a device. */ struct virtqueue { struct virtqueue *next; /* Which device owns me. */ struct device *dev; /* The configuration for this queue. */ struct lguest_vqconfig config; /* The actual ring of buffers. */ struct vring vring; /* Last available index we saw. */ u16 last_avail_idx; /* The routine to call when the Guest pings us, or timeout. */ void (*handle_output)(int fd, struct virtqueue *me, bool timeout); /* Outstanding buffers */ unsigned int inflight; /* Is this blocked awaiting a timer? */ bool blocked; }; /* Remember the arguments to the program so we can "reboot" */ static char **main_args; /* Since guest is UP and we don't run at the same time, we don't need barriers. * But I include them in the code in case others copy it. */ #define wmb() /* Convert an iovec element to the given type. * * This is a fairly ugly trick: we need to know the size of the type and * alignment requirement to check the pointer is kosher. It's also nice to * have the name of the type in case we report failure. * * Typing those three things all the time is cumbersome and error prone, so we * have a macro which sets them all up and passes to the real function. */ #define convert(iov, type) \ ((type *)_convert((iov), sizeof(type), __alignof__(type), #type)) static void *_convert(struct iovec *iov, size_t size, size_t align, const char *name) { if (iov->iov_len != size) errx(1, "Bad iovec size %zu for %s", iov->iov_len, name); if ((unsigned long)iov->iov_base % align != 0) errx(1, "Bad alignment %p for %s", iov->iov_base, name); return iov->iov_base; } /* Wrapper for the last available index. Makes it easier to change. */ #define lg_last_avail(vq) ((vq)->last_avail_idx) /* The virtio configuration space is defined to be little-endian. x86 is * little-endian too, but it's nice to be explicit so we have these helpers. */ #define cpu_to_le16(v16) (v16) #define cpu_to_le32(v32) (v32) #define cpu_to_le64(v64) (v64) #define le16_to_cpu(v16) (v16) #define le32_to_cpu(v32) (v32) #define le64_to_cpu(v64) (v64) /* Is this iovec empty? */ static bool iov_empty(const struct iovec iov[], unsigned int num_iov) { unsigned int i; for (i = 0; i < num_iov; i++) if (iov[i].iov_len) return false; return true; } /* Take len bytes from the front of this iovec. */ static void iov_consume(struct iovec iov[], unsigned num_iov, unsigned len) { unsigned int i; for (i = 0; i < num_iov; i++) { unsigned int used; used = iov[i].iov_len < len ? iov[i].iov_len : len; iov[i].iov_base += used; iov[i].iov_len -= used; len -= used; } assert(len == 0); } /* The device virtqueue descriptors are followed by feature bitmasks. */ static u8 *get_feature_bits(struct device *dev) { return (u8 *)(dev->desc + 1) + dev->desc->num_vq * sizeof(struct lguest_vqconfig); } /*L:100 The Launcher code itself takes us out into userspace, that scary place * where pointers run wild and free! Unfortunately, like most userspace * programs, it's quite boring (which is why everyone likes to hack on the * kernel!). Perhaps if you make up an Lguest Drinking Game at this point, it * will get you through this section. Or, maybe not. * * The Launcher sets up a big chunk of memory to be the Guest's "physical" * memory and stores it in "guest_base". In other words, Guest physical == * Launcher virtual with an offset. * * This can be tough to get your head around, but usually it just means that we * use these trivial conversion functions when the Guest gives us it's * "physical" addresses: */ static void *from_guest_phys(unsigned long addr) { return guest_base + addr; } static unsigned long to_guest_phys(const void *addr) { return (addr - guest_base); } /*L:130 * Loading the Kernel. * * We start with couple of simple helper routines. open_or_die() avoids * error-checking code cluttering the callers: */ static int open_or_die(const char *name, int flags) { int fd = open(name, flags); if (fd < 0) err(1, "Failed to open %s", name); return fd; } /* map_zeroed_pages() takes a number of pages. */ static void *map_zeroed_pages(unsigned int num) { int fd = open_or_die("/dev/zero", O_RDONLY); void *addr; /* We use a private mapping (ie. if we write to the page, it will be * copied). */ addr = mmap(NULL, getpagesize() * num, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, fd, 0); if (addr == MAP_FAILED) err(1, "Mmaping %u pages of /dev/zero", num); close(fd); return addr; } /* Get some more pages for a device. */ static void *get_pages(unsigned int num) { void *addr = from_guest_phys(guest_limit); guest_limit += num * getpagesize(); if (guest_limit > guest_max) errx(1, "Not enough memory for devices"); return addr; } /* This routine is used to load the kernel or initrd. It tries mmap, but if * that fails (Plan 9's kernel file isn't nicely aligned on page boundaries), * it falls back to reading the memory in. */ static void map_at(int fd, void *addr, unsigned long offset, unsigned long len) { ssize_t r; /* We map writable even though for some segments are marked read-only. * The kernel really wants to be writable: it patches its own * instructions. * * MAP_PRIVATE means that the page won't be copied until a write is * done to it. This allows us to share untouched memory between * Guests. */ if (mmap(addr, len, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_FIXED|MAP_PRIVATE, fd, offset) != MAP_FAILED) return; /* pread does a seek and a read in one shot: saves a few lines. */ r = pread(fd, addr, len, offset); if (r != len) err(1, "Reading offset %lu len %lu gave %zi", offset, len, r); } /* This routine takes an open vmlinux image, which is in ELF, and maps it into * the Guest memory. ELF = Embedded Linking Format, which is the format used * by all modern binaries on Linux including the kernel. * * The ELF headers give *two* addresses: a physical address, and a virtual * address. We use the physical address; the Guest will map itself to the * virtual address. * * We return the starting address. */ static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr) { Elf32_Phdr phdr[ehdr->e_phnum]; unsigned int i; /* Sanity checks on the main ELF header: an x86 executable with a * reasonable number of correctly-sized program headers. */ if (ehdr->e_type != ET_EXEC || ehdr->e_machine != EM_386 || ehdr->e_phentsize != sizeof(Elf32_Phdr) || ehdr->e_phnum < 1 || ehdr->e_phnum > 65536U/sizeof(Elf32_Phdr)) errx(1, "Malformed elf header"); /* An ELF executable contains an ELF header and a number of "program" * headers which indicate which parts ("segments") of the program to * load where. */ /* We read in all the program headers at once: */ if (lseek(elf_fd, ehdr->e_phoff, SEEK_SET) < 0) err(1, "Seeking to program headers"); if (read(elf_fd, phdr, sizeof(phdr)) != sizeof(phdr)) err(1, "Reading program headers"); /* Try all the headers: there are usually only three. A read-only one, * a read-write one, and a "note" section which we don't load. */ for (i = 0; i < ehdr->e_phnum; i++) { /* If this isn't a loadable segment, we ignore it */ if (phdr[i].p_type != PT_LOAD) continue; verbose("Section %i: size %i addr %p\n", i, phdr[i].p_memsz, (void *)phdr[i].p_paddr); /* We map this section of the file at its physical address. */ map_at(elf_fd, from_guest_phys(phdr[i].p_paddr), phdr[i].p_offset, phdr[i].p_filesz); } /* The entry point is given in the ELF header. */ return ehdr->e_entry; } /*L:150 A bzImage, unlike an ELF file, is not meant to be loaded. You're * supposed to jump into it and it will unpack itself. We used to have to * perform some hairy magic because the unpacking code scared me. * * Fortunately, Jeremy Fitzhardinge convinced me it wasn't that hard and wrote * a small patch to jump over the tricky bits in the Guest, so now we just read * the funky header so we know where in the file to load, and away we go! */ static unsigned long load_bzimage(int fd) { struct boot_params boot; int r; /* Modern bzImages get loaded at 1M. */ void *p = from_guest_phys(0x100000); /* Go back to the start of the file and read the header. It should be * a Linux boot header (see Documentation/x86/i386/boot.txt) */ lseek(fd, 0, SEEK_SET); read(fd, &boot, sizeof(boot)); /* Inside the setup_hdr, we expect the magic "HdrS" */ if (memcmp(&boot.hdr.header, "HdrS", 4) != 0) errx(1, "This doesn't look like a bzImage to me"); /* Skip over the extra sectors of the header. */ lseek(fd, (boot.hdr.setup_sects+1) * 512, SEEK_SET); /* Now read everything into memory. in nice big chunks. */ while ((r = read(fd, p, 65536)) > 0) p += r; /* Finally, code32_start tells us where to enter the kernel. */ return boot.hdr.code32_start; } /*L:140 Loading the kernel is easy when it's a "vmlinux", but most kernels * come wrapped up in the self-decompressing "bzImage" format. With a little * work, we can load those, too. */ static unsigned long load_kernel(int fd) { Elf32_Ehdr hdr; /* Read in the first few bytes. */ if (read(fd, &hdr, sizeof(hdr)) != sizeof(hdr)) err(1, "Reading kernel"); /* If it's an ELF file, it starts with "\177ELF" */ if (memcmp(hdr.e_ident, ELFMAG, SELFMAG) == 0) return map_elf(fd, &hdr); /* Otherwise we assume it's a bzImage, and try to load it. */ return load_bzimage(fd); } /* This is a trivial little helper to align pages. Andi Kleen hated it because * it calls getpagesize() twice: "it's dumb code." * * Kernel guys get really het up about optimization, even when it's not * necessary. I leave this code as a reaction against that. */ static inline unsigned long page_align(unsigned long addr) { /* Add upwards and truncate downwards. */ return ((addr + getpagesize()-1) & ~(getpagesize()-1)); } /*L:180 An "initial ram disk" is a disk image loaded into memory along with * the kernel which the kernel can use to boot from without needing any * drivers. Most distributions now use this as standard: the initrd contains * the code to load the appropriate driver modules for the current machine. * * Importantly, James Morris works for RedHat, and Fedora uses initrds for its * kernels. He sent me this (and tells me when I break it). */ static unsigned long load_initrd(const char *name, unsigned long mem) { int ifd; struct stat st; unsigned long len; ifd = open_or_die(name, O_RDONLY); /* fstat() is needed to get the file size. */ if (fstat(ifd, &st) < 0) err(1, "fstat() on initrd '%s'", name); /* We map the initrd at the top of memory, but mmap wants it to be * page-aligned, so we round the size up for that. */ len = page_align(st.st_size); map_at(ifd, from_guest_phys(mem - len), 0, st.st_size); /* Once a file is mapped, you can close the file descriptor. It's a * little odd, but quite useful. */ close(ifd); verbose("mapped initrd %s size=%lu @ %p\n", name, len, (void*)mem-len); /* We return the initrd size. */ return len; } /*:*/ /* Simple routine to roll all the commandline arguments together with spaces * between them. */ static void concat(char *dst, char *args[]) { unsigned int i, len = 0; for (i = 0; args[i]; i++) { if (i) { strcat(dst+len, " "); len++; } strcpy(dst+len, args[i]); len += strlen(args[i]); } /* In case it's empty. */ dst[len] = '\0'; } /*L:185 This is where we actually tell the kernel to initialize the Guest. We * saw the arguments it expects when we looked at initialize() in lguest_user.c: * the base of Guest "physical" memory, the top physical page to allow and the * entry point for the Guest. */ static int tell_kernel(unsigned long start) { unsigned long args[] = { LHREQ_INITIALIZE, (unsigned long)guest_base, guest_limit / getpagesize(), start }; int fd; verbose("Guest: %p - %p (%#lx)\n", guest_base, guest_base + guest_limit, guest_limit); fd = open_or_die("/dev/lguest", O_RDWR); if (write(fd, args, sizeof(args)) < 0) err(1, "Writing to /dev/lguest"); /* We return the /dev/lguest file descriptor to control this Guest */ return fd; } /*:*/ static void add_device_fd(int fd) { FD_SET(fd, &devices.infds); if (fd > devices.max_infd) devices.max_infd = fd; } /*L:200 * The Waker. * * With console, block and network devices, we can have lots of input which we * need to process. We could try to tell the kernel what file descriptors to * watch, but handing a file descriptor mask through to the kernel is fairly * icky. * * Instead, we clone off a thread which watches the file descriptors and writes * the LHREQ_BREAK command to the /dev/lguest file descriptor to tell the Host * stop running the Guest. This causes the Launcher to return from the * /dev/lguest read with -EAGAIN, where it will write to /dev/lguest to reset * the LHREQ_BREAK and wake us up again. * * This, of course, is merely a different *kind* of icky. * * Given my well-known antipathy to threads, I'd prefer to use processes. But * it's easier to share Guest memory with threads, and trivial to share the * devices.infds as the Launcher changes it. */ static int waker(void *unused) { /* Close the write end of the pipe: only the Launcher has it open. */ close(waker_fds.pipe[1]); for (;;) { fd_set rfds = devices.infds; unsigned long args[] = { LHREQ_BREAK, 1 }; unsigned int maxfd = devices.max_infd; /* We also listen to the pipe from the Launcher. */ FD_SET(waker_fds.pipe[0], &rfds); if (waker_fds.pipe[0] > maxfd) maxfd = waker_fds.pipe[0]; /* Wait until input is ready from one of the devices. */ select(maxfd+1, &rfds, NULL, NULL, NULL); /* Message from Launcher? */ if (FD_ISSET(waker_fds.pipe[0], &rfds)) { char c; /* If this fails, then assume Launcher has exited. * Don't do anything on exit: we're just a thread! */ if (read(waker_fds.pipe[0], &c, 1) != 1) _exit(0); continue; } /* Send LHREQ_BREAK command to snap the Launcher out of it. */ pwrite(waker_fds.lguest_fd, args, sizeof(args), cpu_id); } return 0; } /* This routine just sets up a pipe to the Waker process. */ static void setup_waker(int lguest_fd) { /* This pipe is closed when Launcher dies, telling Waker. */ if (pipe(waker_fds.pipe) != 0) err(1, "Creating pipe for Waker"); /* Waker also needs to know the lguest fd */ waker_fds.lguest_fd = lguest_fd; if (clone(waker, malloc(4096) + 4096, CLONE_VM | SIGCHLD, NULL) == -1) err(1, "Creating Waker"); } /* * Device Handling. * * When the Guest gives us a buffer, it sends an array of addresses and sizes. * We need to make sure it's not trying to reach into the Launcher itself, so * we have a convenient routine which checks it and exits with an error message * if something funny is going on: */ static void *_check_pointer(unsigned long addr, unsigned int size, unsigned int line) { /* We have to separately check addr and addr+size, because size could * be huge and addr + size might wrap around. */ if (addr >= guest_limit || addr + size >= guest_limit) errx(1, "%s:%i: Invalid address %#lx", __FILE__, line, addr); /* We return a pointer for the caller's convenience, now we know it's * safe to use. */ return from_guest_phys(addr); } /* A macro which transparently hands the line number to the real function. */ #define check_pointer(addr,size) _check_pointer(addr, size, __LINE__) /* Each buffer in the virtqueues is actually a chain of descriptors. This * function returns the next descriptor in the chain, or vq->vring.num if we're * at the end. */ static unsigned next_desc(struct virtqueue *vq, unsigned int i) { unsigned int next; /* If this descriptor says it doesn't chain, we're done. */ if (!(vq->vring.desc[i].flags & VRING_DESC_F_NEXT)) return vq->vring.num; /* Check they're not leading us off end of descriptors. */ next = vq->vring.desc[i].next; /* Make sure compiler knows to grab that: we don't want it changing! */ wmb(); if (next >= vq->vring.num) errx(1, "Desc next is %u", next); return next; } /* This looks in the virtqueue and for the first available buffer, and converts * it to an iovec for convenient access. Since descriptors consist of some * number of output then some number of input descriptors, it's actually two * iovecs, but we pack them into one and note how many of each there were. * * This function returns the descriptor number found, or vq->vring.num (which * is never a valid descriptor number) if none was found. */ static unsigned get_vq_desc(struct virtqueue *vq, struct iovec iov[], unsigned int *out_num, unsigned int *in_num) { unsigned int i, head; u16 last_avail; /* Check it isn't doing very strange things with descriptor numbers. */ last_avail = lg_last_avail(vq); if ((u16)(vq->vring.avail->idx - last_avail) > vq->vring.num) errx(1, "Guest moved used index from %u to %u", last_avail, vq->vring.avail->idx); /* If there's nothing new since last we looked, return invalid. */ if (vq->vring.avail->idx == last_avail) return vq->vring.num; /* Grab the next descriptor number they're advertising, and increment * the index we've seen. */ head = vq->vring.avail->ring[last_avail % vq->vring.num]; lg_last_avail(vq)++; /* If their number is silly, that's a fatal mistake. */ if (head >= vq->vring.num) errx(1, "Guest says index %u is available", head); /* When we start there are none of either input nor output. */ *out_num = *in_num = 0; i = head; do { /* Grab the first descriptor, and check it's OK. */ iov[*out_num + *in_num].iov_len = vq->vring.desc[i].len; iov[*out_num + *in_num].iov_base = check_pointer(vq->vring.desc[i].addr, vq->vring.desc[i].len); /* If this is an input descriptor, increment that count. */ if (vq->vring.desc[i].flags & VRING_DESC_F_WRITE) (*in_num)++; else { /* If it's an output descriptor, they're all supposed * to come before any input descriptors. */ if (*in_num) errx(1, "Descriptor has out after in"); (*out_num)++; } /* If we've got too many, that implies a descriptor loop. */ if (*out_num + *in_num > vq->vring.num) errx(1, "Looped descriptor"); } while ((i = next_desc(vq, i)) != vq->vring.num); vq->inflight++; return head; } /* After we've used one of their buffers, we tell them about it. We'll then * want to send them an interrupt, using trigger_irq(). */ static void add_used(struct virtqueue *vq, unsigned int head, int len) { struct vring_used_elem *used; /* The virtqueue contains a ring of used buffers. Get a pointer to the * next entry in that used ring. */ used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num]; used->id = head; used->len = len; /* Make sure buffer is written before we update index. */ wmb(); vq->vring.used->idx++; vq->inflight--; } /* This actually sends the interrupt for this virtqueue */ static void trigger_irq(int fd, struct virtqueue *vq) { unsigned long buf[] = { LHREQ_IRQ, vq->config.irq }; /* If they don't want an interrupt, don't send one, unless empty. */ if ((vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT) && vq->inflight) return; /* Send the Guest an interrupt tell them we used something up. */ if (write(fd, buf, sizeof(buf)) != 0) err(1, "Triggering irq %i", vq->config.irq); } /* And here's the combo meal deal. Supersize me! */ static void add_used_and_trigger(int fd, struct virtqueue *vq, unsigned int head, int len) { add_used(vq, head, len); trigger_irq(fd, vq); } /* * The Console * * Here is the input terminal setting we save, and the routine to restore them * on exit so the user gets their terminal back. */ static struct termios orig_term; static void restore_term(void) { tcsetattr(STDIN_FILENO, TCSANOW, &orig_term); } /* We associate some data with the console for our exit hack. */ struct console_abort { /* How many times have they hit ^C? */ int count; /* When did they start? */ struct timeval start; }; /* This is the routine which handles console input (ie. stdin). */ static bool handle_console_input(int fd, struct device *dev) { int len; unsigned int head, in_num, out_num; struct iovec iov[dev->vq->vring.num]; struct console_abort *abort = dev->priv; /* First we need a console buffer from the Guests's input virtqueue. */ head = get_vq_desc(dev->vq, iov, &out_num, &in_num); /* If they're not ready for input, stop listening to this file * descriptor. We'll start again once they add an input buffer. */ if (head == dev->vq->vring.num) return false; if (out_num) errx(1, "Output buffers in console in queue?"); /* This is why we convert to iovecs: the readv() call uses them, and so * it reads straight into the Guest's buffer. */ len = readv(dev->fd, iov, in_num); if (len <= 0) { /* This implies that the console is closed, is /dev/null, or * something went terribly wrong. */ warnx("Failed to get console input, ignoring console."); /* Put the input terminal back. */ restore_term(); /* Remove callback from input vq, so it doesn't restart us. */ dev->vq->handle_output = NULL; /* Stop listening to this fd: don't call us again. */ return false; } /* Tell the Guest about the new input. */ add_used_and_trigger(fd, dev->vq, head, len); /* Three ^C within one second? Exit. * * This is such a hack, but works surprisingly well. Each ^C has to be * in a buffer by itself, so they can't be too fast. But we check that * we get three within about a second, so they can't be too slow. */ if (len == 1 && ((char *)iov[0].iov_base)[0] == 3) { if (!abort->count++) gettimeofday(&abort->start, NULL); else if (abort->count == 3) { struct timeval now; gettimeofday(&now, NULL); if (now.tv_sec <= abort->start.tv_sec+1) { unsigned long args[] = { LHREQ_BREAK, 0 }; /* Close the fd so Waker will know it has to * exit. */ close(waker_fds.pipe[1]); /* Just in case Waker is blocked in BREAK, send * unbreak now. */ write(fd, args, sizeof(args)); exit(2); } abort->count = 0; } } else /* Any other key resets the abort counter. */ abort->count = 0; /* Everything went OK! */ return true; } /* Handling output for console is simple: we just get all the output buffers * and write them to stdout. */ static void handle_console_output(int fd, struct virtqueue *vq, bool timeout) { unsigned int head, out, in; int len; struct iovec iov[vq->vring.num]; /* Keep getting output buffers from the Guest until we run out. */ while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) { if (in) errx(1, "Input buffers in output queue?"); len = writev(STDOUT_FILENO, iov, out); add_used_and_trigger(fd, vq, head, len); } } /* This is called when we no longer want to hear about Guest changes to a * virtqueue. This is more efficient in high-traffic cases, but it means we * have to set a timer to check if any more changes have occurred. */ static void block_vq(struct virtqueue *vq) { struct itimerval itm; vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY; vq->blocked = true; itm.it_interval.tv_sec = 0; itm.it_interval.tv_usec = 0; itm.it_value.tv_sec = 0; itm.it_value.tv_usec = timeout_usec; setitimer(ITIMER_REAL, &itm, NULL); } /* * The Network * * Handling output for network is also simple: we get all the output buffers * and write them (ignoring the first element) to this device's file descriptor * (/dev/net/tun). */ static void handle_net_output(int fd, struct virtqueue *vq, bool timeout) { unsigned int head, out, in, num = 0; int len; struct iovec iov[vq->vring.num]; static int last_timeout_num; /* Keep getting output buffers from the Guest until we run out. */ while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) { if (in) errx(1, "Input buffers in output queue?"); len = writev(vq->dev->fd, iov, out); if (len < 0) err(1, "Writing network packet to tun"); add_used_and_trigger(fd, vq, head, len); num++; } /* Block further kicks and set up a timer if we saw anything. */ if (!timeout && num) block_vq(vq); /* We never quite know how long should we wait before we check the * queue again for more packets. We start at 500 microseconds, and if * we get fewer packets than last time, we assume we made the timeout * too small and increase it by 10 microseconds. Otherwise, we drop it * by one microsecond every time. It seems to work well enough. */ if (timeout) { if (num < last_timeout_num) timeout_usec += 10; else if (timeout_usec > 1) timeout_usec--; last_timeout_num = num; } } /* This is where we handle a packet coming in from the tun device to our * Guest. */ static bool handle_tun_input(int fd, struct device *dev) { unsigned int head, in_num, out_num; int len; struct iovec iov[dev->vq->vring.num]; /* First we need a network buffer from the Guests's recv virtqueue. */ head = get_vq_desc(dev->vq, iov, &out_num, &in_num); if (head == dev->vq->vring.num) { /* Now, it's expected that if we try to send a packet too * early, the Guest won't be ready yet. Wait until the device * status says it's ready. */ /* FIXME: Actually want DRIVER_ACTIVE here. */ /* Now tell it we want to know if new things appear. */ dev->vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY; wmb(); /* We'll turn this back on if input buffers are registered. */ return false; } else if (out_num) errx(1, "Output buffers in network recv queue?"); /* Read the packet from the device directly into the Guest's buffer. */ len = readv(dev->fd, iov, in_num); if (len <= 0) err(1, "reading network"); /* Tell the Guest about the new packet. */ add_used_and_trigger(fd, dev->vq, head, len); verbose("tun input packet len %i [%02x %02x] (%s)\n", len, ((u8 *)iov[1].iov_base)[0], ((u8 *)iov[1].iov_base)[1], head != dev->vq->vring.num ? "sent" : "discarded"); /* All good. */ return true; } /*L:215 This is the callback attached to the network and console input * virtqueues: it ensures we try again, in case we stopped console or net * delivery because Guest didn't have any buffers. */ static void enable_fd(int fd, struct virtqueue *vq, bool timeout) { add_device_fd(vq->dev->fd); /* Snap the Waker out of its select loop. */ write(waker_fds.pipe[1], "", 1); } static void net_enable_fd(int fd, struct virtqueue *vq, bool timeout) { /* We don't need to know again when Guest refills receive buffer. */ vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY; enable_fd(fd, vq, timeout); } /* When the Guest tells us they updated the status field, we handle it. */ static void update_device_status(struct device *dev) { struct virtqueue *vq; /* This is a reset. */ if (dev->desc->status == 0) { verbose("Resetting device %s\n", dev->name); /* Clear any features they've acked. */ memset(get_feature_bits(dev) + dev->desc->feature_len, 0, dev->desc->feature_len); /* Zero out the virtqueues. */ for (vq = dev->vq; vq; vq = vq->next) { memset(vq->vring.desc, 0, vring_size(vq->config.num, LGUEST_VRING_ALIGN)); lg_last_avail(vq) = 0; } } else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) { warnx("Device %s configuration FAILED", dev->name); } else if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK) { unsigned int i; verbose("Device %s OK: offered", dev->name); for (i = 0; i < dev->desc->feature_len; i++) verbose(" %02x", get_feature_bits(dev)[i]); verbose(", accepted"); for (i = 0; i < dev->desc->feature_len; i++) verbose(" %02x", get_feature_bits(dev) [dev->desc->feature_len+i]); if (dev->ready) dev->ready(dev); } } /* This is the generic routine we call when the Guest uses LHCALL_NOTIFY. */ static void handle_output(int fd, unsigned long addr) { struct device *i; struct virtqueue *vq; /* Check each device and virtqueue. */ for (i = devices.dev; i; i = i->next) { /* Notifications to device descriptors update device status. */ if (from_guest_phys(addr) == i->desc) { update_device_status(i); return; } /* Notifications to virtqueues mean output has occurred. */ for (vq = i->vq; vq; vq = vq->next) { if (vq->config.pfn != addr/getpagesize()) continue; /* Guest should acknowledge (and set features!) before * using the device. */ if (i->desc->status == 0) { warnx("%s gave early output", i->name); return; } if (strcmp(vq->dev->name, "console") != 0) verbose("Output to %s\n", vq->dev->name); if (vq->handle_output) vq->handle_output(fd, vq, false); return; } } /* Early console write is done using notify on a nul-terminated string * in Guest memory. */ if (addr >= guest_limit) errx(1, "Bad NOTIFY %#lx", addr); write(STDOUT_FILENO, from_guest_phys(addr), strnlen(from_guest_phys(addr), guest_limit - addr)); } static void handle_timeout(int fd) { char buf[32]; struct device *i; struct virtqueue *vq; /* Clear the pipe */ read(timeoutpipe[0], buf, sizeof(buf)); /* Check each device and virtqueue: flush blocked ones. */ for (i = devices.dev; i; i = i->next) { for (vq = i->vq; vq; vq = vq->next) { if (!vq->blocked) continue; vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY; vq->blocked = false; if (vq->handle_output) vq->handle_output(fd, vq, true); } } } /* This is called when the Waker wakes us up: check for incoming file * descriptors. */ static void handle_input(int fd) { /* select() wants a zeroed timeval to mean "don't wait". */ struct timeval poll = { .tv_sec = 0, .tv_usec = 0 }; for (;;) { struct device *i; fd_set fds = devices.infds; int num; num = select(devices.max_infd+1, &fds, NULL, NULL, &poll); /* Could get interrupted */ if (num < 0) continue; /* If nothing is ready, we're done. */ if (num == 0) break; /* Otherwise, call the device(s) which have readable file * descriptors and a method of handling them. */ for (i = devices.dev; i; i = i->next) { if (i->handle_input && FD_ISSET(i->fd, &fds)) { if (i->handle_input(fd, i)) continue; /* If handle_input() returns false, it means we * should no longer service it. Networking and * console do this when there's no input * buffers to deliver into. Console also uses * it when it discovers that stdin is closed. */ FD_CLR(i->fd, &devices.infds); } } /* Is this the timeout fd? */ if (FD_ISSET(timeoutpipe[0], &fds)) handle_timeout(fd); } } /*L:190 * Device Setup * * All devices need a descriptor so the Guest knows it exists, and a "struct * device" so the Launcher can keep track of it. We have common helper * routines to allocate and manage them. */ /* The layout of the device page is a "struct lguest_device_desc" followed by a * number of virtqueue descriptors, then two sets of feature bits, then an * array of configuration bytes. This routine returns the configuration * pointer. */ static u8 *device_config(const struct device *dev) { return (void *)(dev->desc + 1) + dev->desc->num_vq * sizeof(struct lguest_vqconfig) + dev->desc->feature_len * 2; } /* This routine allocates a new "struct lguest_device_desc" from descriptor * table page just above the Guest's normal memory. It returns a pointer to * that descriptor. */ static struct lguest_device_desc *new_dev_desc(u16 type) { struct lguest_device_desc d = { .type = type }; void *p; /* Figure out where the next device config is, based on the last one. */ if (devices.lastdev) p = device_config(devices.lastdev) + devices.lastdev->desc->config_len; else p = devices.descpage; /* We only have one page for all the descriptors. */ if (p + sizeof(d) > (void *)devices.descpage + getpagesize()) errx(1, "Too many devices"); /* p might not be aligned, so we memcpy in. */ return memcpy(p, &d, sizeof(d)); } /* Each device descriptor is followed by the description of its virtqueues. We * specify how many descriptors the virtqueue is to have. */ static void add_virtqueue(struct device *dev, unsigned int num_descs, void (*handle_output)(int, struct virtqueue *, bool)) { unsigned int pages; struct virtqueue **i, *vq = malloc(sizeof(*vq)); void *p; /* First we need some memory for this virtqueue. */ pages = (vring_size(num_descs, LGUEST_VRING_ALIGN) + getpagesize() - 1) / getpagesize(); p = get_pages(pages); /* Initialize the virtqueue */ vq->next = NULL; vq->last_avail_idx = 0; vq->dev = dev; vq->inflight = 0; vq->blocked = false; /* Initialize the configuration. */ vq->config.num = num_descs; vq->config.irq = devices.next_irq++; vq->config.pfn = to_guest_phys(p) / getpagesize(); /* Initialize the vring. */ vring_init(&vq->vring, num_descs, p, LGUEST_VRING_ALIGN); /* Append virtqueue to this device's descriptor. We use * device_config() to get the end of the device's current virtqueues; * we check that we haven't added any config or feature information * yet, otherwise we'd be overwriting them. */ assert(dev->desc->config_len == 0 && dev->desc->feature_len == 0); memcpy(device_config(dev), &vq->config, sizeof(vq->config)); dev->desc->num_vq++; verbose("Virtqueue page %#lx\n", to_guest_phys(p)); /* Add to tail of list, so dev->vq is first vq, dev->vq->next is * second. */ for (i = &dev->vq; *i; i = &(*i)->next); *i = vq; /* Set the routine to call when the Guest does something to this * virtqueue. */ vq->handle_output = handle_output; /* As an optimization, set the advisory "Don't Notify Me" flag if we * don't have a handler */ if (!handle_output) vq->vring.used->flags = VRING_USED_F_NO_NOTIFY; } /* The first half of the feature bitmask is for us to advertise features. The * second half is for the Guest to accept features. */ static void add_feature(struct device *dev, unsigned bit) { u8 *features = get_feature_bits(dev); /* We can't extend the feature bits once we've added config bytes */ if (dev->desc->feature_len <= bit / CHAR_BIT) { assert(dev->desc->config_len == 0); dev->desc->feature_len = (bit / CHAR_BIT) + 1; } features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT)); } /* This routine sets the configuration fields for an existing device's * descriptor. It only works for the last device, but that's OK because that's * how we use it. */ static void set_config(struct device *dev, unsigned len, const void *conf) { /* Check we haven't overflowed our single page. */ if (device_config(dev) + len > devices.descpage + getpagesize()) errx(1, "Too many devices"); /* Copy in the config information, and store the length. */ memcpy(device_config(dev), conf, len); dev->desc->config_len = len; } /* This routine does all the creation and setup of a new device, including * calling new_dev_desc() to allocate the descriptor and device memory. * * See what I mean about userspace being boring? */ static struct device *new_device(const char *name, u16 type, int fd, bool (*handle_input)(int, struct device *)) { struct device *dev = malloc(sizeof(*dev)); /* Now we populate the fields one at a time. */ dev->fd = fd; /* If we have an input handler for this file descriptor, then we add it * to the device_list's fdset and maxfd. */ if (handle_input) add_device_fd(dev->fd); dev->desc = new_dev_desc(type); dev->handle_input = handle_input; dev->name = name; dev->vq = NULL; dev->ready = NULL; /* Append to device list. Prepending to a single-linked list is * easier, but the user expects the devices to be arranged on the bus * in command-line order. The first network device on the command line * is eth0, the first block device /dev/vda, etc. */ if (devices.lastdev) devices.lastdev->next = dev; else devices.dev = dev; devices.lastdev = dev; return dev; } /* Our first setup routine is the console. It's a fairly simple device, but * UNIX tty handling makes it uglier than it could be. */ static void setup_console(void) { struct device *dev; /* If we can save the initial standard input settings... */ if (tcgetattr(STDIN_FILENO, &orig_term) == 0) { struct termios term = orig_term; /* Then we turn off echo, line buffering and ^C etc. We want a * raw input stream to the Guest. */ term.c_lflag &= ~(ISIG|ICANON|ECHO); tcsetattr(STDIN_FILENO, TCSANOW, &term); /* If we exit gracefully, the original settings will be * restored so the user can see what they're typing. */ atexit(restore_term); } dev = new_device("console", VIRTIO_ID_CONSOLE, STDIN_FILENO, handle_console_input); /* We store the console state in dev->priv, and initialize it. */ dev->priv = malloc(sizeof(struct console_abort)); ((struct console_abort *)dev->priv)->count = 0; /* The console needs two virtqueues: the input then the output. When * they put something the input queue, we make sure we're listening to * stdin. When they put something in the output queue, we write it to * stdout. */ add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd); add_virtqueue(dev, VIRTQUEUE_NUM, handle_console_output); verbose("device %u: console\n", devices.device_num++); } /*:*/ static void timeout_alarm(int sig) { write(timeoutpipe[1], "", 1); } static void setup_timeout(void) { if (pipe(timeoutpipe) != 0) err(1, "Creating timeout pipe"); if (fcntl(timeoutpipe[1], F_SETFL, fcntl(timeoutpipe[1], F_GETFL) | O_NONBLOCK) != 0) err(1, "Making timeout pipe nonblocking"); add_device_fd(timeoutpipe[0]); signal(SIGALRM, timeout_alarm); } /*M:010 Inter-guest networking is an interesting area. Simplest is to have a * --sharenet= option which opens or creates a named pipe. This can be * used to send packets to another guest in a 1:1 manner. * * More sopisticated is to use one of the tools developed for project like UML * to do networking. * * Faster is to do virtio bonding in kernel. Doing this 1:1 would be * completely generic ("here's my vring, attach to your vring") and would work * for any traffic. Of course, namespace and permissions issues need to be * dealt with. A more sophisticated "multi-channel" virtio_net.c could hide * multiple inter-guest channels behind one interface, although it would * require some manner of hotplugging new virtio channels. * * Finally, we could implement a virtio network switch in the kernel. :*/ static u32 str2ip(const char *ipaddr) { unsigned int b[4]; if (sscanf(ipaddr, "%u.%u.%u.%u", &b[0], &b[1], &b[2], &b[3]) != 4) errx(1, "Failed to parse IP address '%s'", ipaddr); return (b[0] << 24) | (b[1] << 16) | (b[2] << 8) | b[3]; } static void str2mac(const char *macaddr, unsigned char mac[6]) { unsigned int m[6]; if (sscanf(macaddr, "%02x:%02x:%02x:%02x:%02x:%02x", &m[0], &m[1], &m[2], &m[3], &m[4], &m[5]) != 6) errx(1, "Failed to parse mac address '%s'", macaddr); mac[0] = m[0]; mac[1] = m[1]; mac[2] = m[2]; mac[3] = m[3]; mac[4] = m[4]; mac[5] = m[5]; } /* This code is "adapted" from libbridge: it attaches the Host end of the * network device to the bridge device specified by the command line. * * This is yet another James Morris contribution (I'm an IP-level guy, so I * dislike bridging), and I just try not to break it. */ static void add_to_bridge(int fd, const char *if_name, const char *br_name) { int ifidx; struct ifreq ifr; if (!*br_name) errx(1, "must specify bridge name"); ifidx = if_nametoindex(if_name); if (!ifidx) errx(1, "interface %s does not exist!", if_name); strncpy(ifr.ifr_name, br_name, IFNAMSIZ); ifr.ifr_name[IFNAMSIZ-1] = '\0'; ifr.ifr_ifindex = ifidx; if (ioctl(fd, SIOCBRADDIF, &ifr) < 0) err(1, "can't add %s to bridge %s", if_name, br_name); } /* This sets up the Host end of the network device with an IP address, brings * it up so packets will flow, the copies the MAC address into the hwaddr * pointer. */ static void configure_device(int fd, const char *tapif, u32 ipaddr) { struct ifreq ifr; struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr; memset(&ifr, 0, sizeof(ifr)); strcpy(ifr.ifr_name, tapif); /* Don't read these incantations. Just cut & paste them like I did! */ sin->sin_family = AF_INET; sin->sin_addr.s_addr = htonl(ipaddr); if (ioctl(fd, SIOCSIFADDR, &ifr) != 0) err(1, "Setting %s interface address", tapif); ifr.ifr_flags = IFF_UP; if (ioctl(fd, SIOCSIFFLAGS, &ifr) != 0) err(1, "Bringing interface %s up", tapif); } static int get_tun_device(char tapif[IFNAMSIZ]) { struct ifreq ifr; int netfd; /* Start with this zeroed. Messy but sure. */ memset(&ifr, 0, sizeof(ifr)); /* We open the /dev/net/tun device and tell it we want a tap device. A * tap device is like a tun device, only somehow different. To tell * the truth, I completely blundered my way through this code, but it * works now! */ netfd = open_or_die("/dev/net/tun", O_RDWR); ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR; strcpy(ifr.ifr_name, "tap%d"); if (ioctl(netfd, TUNSETIFF, &ifr) != 0) err(1, "configuring /dev/net/tun"); if (ioctl(netfd, TUNSETOFFLOAD, TUN_F_CSUM|TUN_F_TSO4|TUN_F_TSO6|TUN_F_TSO_ECN) != 0) err(1, "Could not set features for tun device"); /* We don't need checksums calculated for packets coming in this * device: trust us! */ ioctl(netfd, TUNSETNOCSUM, 1); memcpy(tapif, ifr.ifr_name, IFNAMSIZ); return netfd; } /*L:195 Our network is a Host<->Guest network. This can either use bridging or * routing, but the principle is the same: it uses the "tun" device to inject * packets into the Host as if they came in from a normal network card. We * just shunt packets between the Guest and the tun device. */ static void setup_tun_net(char *arg) { struct device *dev; int netfd, ipfd; u32 ip = INADDR_ANY; bool bridging = false; char tapif[IFNAMSIZ], *p; struct virtio_net_config conf; netfd = get_tun_device(tapif); /* First we create a new network device. */ dev = new_device("net", VIRTIO_ID_NET, netfd, handle_tun_input); /* Network devices need a receive and a send queue, just like * console. */ add_virtqueue(dev, VIRTQUEUE_NUM, net_enable_fd); add_virtqueue(dev, VIRTQUEUE_NUM, handle_net_output); /* We need a socket to perform the magic network ioctls to bring up the * tap interface, connect to the bridge etc. Any socket will do! */ ipfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP); if (ipfd < 0) err(1, "opening IP socket"); /* If the command line was --tunnet=bridge: do bridging. */ if (!strncmp(BRIDGE_PFX, arg, strlen(BRIDGE_PFX))) { arg += strlen(BRIDGE_PFX); bridging = true; } /* A mac address may follow the bridge name or IP address */ p = strchr(arg, ':'); if (p) { str2mac(p+1, conf.mac); add_feature(dev, VIRTIO_NET_F_MAC); *p = '\0'; } /* arg is now either an IP address or a bridge name */ if (bridging) add_to_bridge(ipfd, tapif, arg); else ip = str2ip(arg); /* Set up the tun device. */ configure_device(ipfd, tapif, ip); add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY); /* Expect Guest to handle everything except UFO */ add_feature(dev, VIRTIO_NET_F_CSUM); add_feature(dev, VIRTIO_NET_F_GUEST_CSUM); add_feature(dev, VIRTIO_NET_F_GUEST_TSO4); add_feature(dev, VIRTIO_NET_F_GUEST_TSO6); add_feature(dev, VIRTIO_NET_F_GUEST_ECN); add_feature(dev, VIRTIO_NET_F_HOST_TSO4); add_feature(dev, VIRTIO_NET_F_HOST_TSO6); add_feature(dev, VIRTIO_NET_F_HOST_ECN); set_config(dev, sizeof(conf), &conf); /* We don't need the socket any more; setup is done. */ close(ipfd); devices.device_num++; if (bridging) verbose("device %u: tun %s attached to bridge: %s\n", devices.device_num, tapif, arg); else verbose("device %u: tun %s: %s\n", devices.device_num, tapif, arg); } /* Our block (disk) device should be really simple: the Guest asks for a block * number and we read or write that position in the file. Unfortunately, that * was amazingly slow: the Guest waits until the read is finished before * running anything else, even if it could have been doing useful work. * * We could use async I/O, except it's reputed to suck so hard that characters * actually go missing from your code when you try to use it. * * So we farm the I/O out to thread, and communicate with it via a pipe. */ /* This hangs off device->priv. */ struct vblk_info { /* The size of the file. */ off64_t len; /* The file descriptor for the file. */ int fd; /* IO thread listens on this file descriptor [0]. */ int workpipe[2]; /* IO thread writes to this file descriptor to mark it done, then * Launcher triggers interrupt to Guest. */ int done_fd; }; /*L:210 * The Disk * * Remember that the block device is handled by a separate I/O thread. We head * straight into the core of that thread here: */ static bool service_io(struct device *dev) { struct vblk_info *vblk = dev->priv; unsigned int head, out_num, in_num, wlen; int ret; u8 *in; struct virtio_blk_outhdr *out; struct iovec iov[dev->vq->vring.num]; off64_t off; /* See if there's a request waiting. If not, nothing to do. */ head = get_vq_desc(dev->vq, iov, &out_num, &in_num); if (head == dev->vq->vring.num) return false; /* Every block request should contain at least one output buffer * (detailing the location on disk and the type of request) and one * input buffer (to hold the result). */ if (out_num == 0 || in_num == 0) errx(1, "Bad virtblk cmd %u out=%u in=%u", head, out_num, in_num); out = convert(&iov[0], struct virtio_blk_outhdr); in = convert(&iov[out_num+in_num-1], u8); off = out->sector * 512; /* The block device implements "barriers", where the Guest indicates * that it wants all previous writes to occur before this write. We * don't have a way of asking our kernel to do a barrier, so we just * synchronize all the data in the file. Pretty poor, no? */ if (out->type & VIRTIO_BLK_T_BARRIER) fdatasync(vblk->fd); /* In general the virtio block driver is allowed to try SCSI commands. * It'd be nice if we supported eject, for example, but we don't. */ if (out->type & VIRTIO_BLK_T_SCSI_CMD) { fprintf(stderr, "Scsi commands unsupported\n"); *in = VIRTIO_BLK_S_UNSUPP; wlen = sizeof(*in); } else if (out->type & VIRTIO_BLK_T_OUT) { /* Write */ /* Move to the right location in the block file. This can fail * if they try to write past end. */ if (lseek64(vblk->fd, off, SEEK_SET) != off) err(1, "Bad seek to sector %llu", out->sector); ret = writev(vblk->fd, iov+1, out_num-1); verbose("WRITE to sector %llu: %i\n", out->sector, ret); /* Grr... Now we know how long the descriptor they sent was, we * make sure they didn't try to write over the end of the block * file (possibly extending it). */ if (ret > 0 && off + ret > vblk->len) { /* Trim it back to the correct length */ ftruncate64(vblk->fd, vblk->len); /* Die, bad Guest, die. */ errx(1, "Write past end %llu+%u", off, ret); } wlen = sizeof(*in); *in = (ret >= 0 ? VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR); } else { /* Read */ /* Move to the right location in the block file. This can fail * if they try to read past end. */ if (lseek64(vblk->fd, off, SEEK_SET) != off) err(1, "Bad seek to sector %llu", out->sector); ret = readv(vblk->fd, iov+1, in_num-1); verbose("READ from sector %llu: %i\n", out->sector, ret); if (ret >= 0) { wlen = sizeof(*in) + ret; *in = VIRTIO_BLK_S_OK; } else { wlen = sizeof(*in); *in = VIRTIO_BLK_S_IOERR; } } /* We can't trigger an IRQ, because we're not the Launcher. It does * that when we tell it we're done. */ add_used(dev->vq, head, wlen); return true; } /* This is the thread which actually services the I/O. */ static int io_thread(void *_dev) { struct device *dev = _dev; struct vblk_info *vblk = dev->priv; char c; /* Close other side of workpipe so we get 0 read when main dies. */ close(vblk->workpipe[1]); /* Close the other side of the done_fd pipe. */ close(dev->fd); /* When this read fails, it means Launcher died, so we follow. */ while (read(vblk->workpipe[0], &c, 1) == 1) { /* We acknowledge each request immediately to reduce latency, * rather than waiting until we've done them all. I haven't * measured to see if it makes any difference. * * That would be an interesting test, wouldn't it? You could * also try having more than one I/O thread. */ while (service_io(dev)) write(vblk->done_fd, &c, 1); } return 0; } /* Now we've seen the I/O thread, we return to the Launcher to see what happens * when that thread tells us it's completed some I/O. */ static bool handle_io_finish(int fd, struct device *dev) { char c; /* If the I/O thread died, presumably it printed the error, so we * simply exit. */ if (read(dev->fd, &c, 1) != 1) exit(1); /* It did some work, so trigger the irq. */ trigger_irq(fd, dev->vq); return true; } /* When the Guest submits some I/O, we just need to wake the I/O thread. */ static void handle_virtblk_output(int fd, struct virtqueue *vq, bool timeout) { struct vblk_info *vblk = vq->dev->priv; char c = 0; /* Wake up I/O thread and tell it to go to work! */ if (write(vblk->workpipe[1], &c, 1) != 1) /* Presumably it indicated why it died. */ exit(1); } /*L:198 This actually sets up a virtual block device. */ static void setup_block_file(const char *filename) { int p[2]; struct device *dev; struct vblk_info *vblk; void *stack; struct virtio_blk_config conf; /* This is the pipe the I/O thread will use to tell us I/O is done. */ pipe(p); /* The device responds to return from I/O thread. */ dev = new_device("block", VIRTIO_ID_BLOCK, p[0], handle_io_finish); /* The device has one virtqueue, where the Guest places requests. */ add_virtqueue(dev, VIRTQUEUE_NUM, handle_virtblk_output); /* Allocate the room for our own bookkeeping */ vblk = dev->priv = malloc(sizeof(*vblk)); /* First we open the file and store the length. */ vblk->fd = open_or_die(filename, O_RDWR|O_LARGEFILE); vblk->len = lseek64(vblk->fd, 0, SEEK_END); /* We support barriers. */ add_feature(dev, VIRTIO_BLK_F_BARRIER); /* Tell Guest how many sectors this device has. */ conf.capacity = cpu_to_le64(vblk->len / 512); /* Tell Guest not to put in too many descriptors at once: two are used * for the in and out elements. */ add_feature(dev, VIRTIO_BLK_F_SEG_MAX); conf.seg_max = cpu_to_le32(VIRTQUEUE_NUM - 2); set_config(dev, sizeof(conf), &conf); /* The I/O thread writes to this end of the pipe when done. */ vblk->done_fd = p[1]; /* This is the second pipe, which is how we tell the I/O thread about * more work. */ pipe(vblk->workpipe); /* Create stack for thread and run it. Since stack grows upwards, we * point the stack pointer to the end of this region. */ stack = malloc(32768); /* SIGCHLD - We dont "wait" for our cloned thread, so prevent it from * becoming a zombie. */ if (clone(io_thread, stack + 32768, CLONE_VM | SIGCHLD, dev) == -1) err(1, "Creating clone"); /* We don't need to keep the I/O thread's end of the pipes open. */ close(vblk->done_fd); close(vblk->workpipe[0]); verbose("device %u: virtblock %llu sectors\n", devices.device_num, le64_to_cpu(conf.capacity)); } /* Our random number generator device reads from /dev/random into the Guest's * input buffers. The usual case is that the Guest doesn't want random numbers * and so has no buffers although /dev/random is still readable, whereas * console is the reverse. * * The same logic applies, however. */ static bool handle_rng_input(int fd, struct device *dev) { int len; unsigned int head, in_num, out_num, totlen = 0; struct iovec iov[dev->vq->vring.num]; /* First we need a buffer from the Guests's virtqueue. */ head = get_vq_desc(dev->vq, iov, &out_num, &in_num); /* If they're not ready for input, stop listening to this file * descriptor. We'll start again once they add an input buffer. */ if (head == dev->vq->vring.num) return false; if (out_num) errx(1, "Output buffers in rng?"); /* This is why we convert to iovecs: the readv() call uses them, and so * it reads straight into the Guest's buffer. We loop to make sure we * fill it. */ while (!iov_empty(iov, in_num)) { len = readv(dev->fd, iov, in_num); if (len <= 0) err(1, "Read from /dev/random gave %i", len); iov_consume(iov, in_num, len); totlen += len; } /* Tell the Guest about the new input. */ add_used_and_trigger(fd, dev->vq, head, totlen); /* Everything went OK! */ return true; } /* And this creates a "hardware" random number device for the Guest. */ static void setup_rng(void) { struct device *dev; int fd; fd = open_or_die("/dev/random", O_RDONLY); /* The device responds to return from I/O thread. */ dev = new_device("rng", VIRTIO_ID_RNG, fd, handle_rng_input); /* The device has one virtqueue, where the Guest places inbufs. */ add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd); verbose("device %u: rng\n", devices.device_num++); } /* That's the end of device setup. */ /*L:230 Reboot is pretty easy: clean up and exec() the Launcher afresh. */ static void __attribute__((noreturn)) restart_guest(void) { unsigned int i; /* Since we don't track all open fds, we simply close everything beyond * stderr. */ for (i = 3; i < FD_SETSIZE; i++) close(i); /* The exec automatically gets rid of the I/O and Waker threads. */ execv(main_args[0], main_args); err(1, "Could not exec %s", main_args[0]); } /*L:220 Finally we reach the core of the Launcher which runs the Guest, serves * its input and output, and finally, lays it to rest. */ static void __attribute__((noreturn)) run_guest(int lguest_fd) { for (;;) { unsigned long args[] = { LHREQ_BREAK, 0 }; unsigned long notify_addr; int readval; /* We read from the /dev/lguest device to run the Guest. */ readval = pread(lguest_fd, ¬ify_addr, sizeof(notify_addr), cpu_id); /* One unsigned long means the Guest did HCALL_NOTIFY */ if (readval == sizeof(notify_addr)) { verbose("Notify on address %#lx\n", notify_addr); handle_output(lguest_fd, notify_addr); continue; /* ENOENT means the Guest died. Reading tells us why. */ } else if (errno == ENOENT) { char reason[1024] = { 0 }; pread(lguest_fd, reason, sizeof(reason)-1, cpu_id); errx(1, "%s", reason); /* ERESTART means that we need to reboot the guest */ } else if (errno == ERESTART) { restart_guest(); /* EAGAIN means a signal (timeout). * Anything else means a bug or incompatible change. */ } else if (errno != EAGAIN) err(1, "Running guest failed"); /* Only service input on thread for CPU 0. */ if (cpu_id != 0) continue; /* Service input, then unset the BREAK to release the Waker. */ handle_input(lguest_fd); if (pwrite(lguest_fd, args, sizeof(args), cpu_id) < 0) err(1, "Resetting break"); } } /*L:240 * This is the end of the Launcher. The good news: we are over halfway * through! The bad news: the most fiendish part of the code still lies ahead * of us. * * Are you ready? Take a deep breath and join me in the core of the Host, in * "make Host". :*/ static struct option opts[] = { { "verbose", 0, NULL, 'v' }, { "tunnet", 1, NULL, 't' }, { "block", 1, NULL, 'b' }, { "rng", 0, NULL, 'r' }, { "initrd", 1, NULL, 'i' }, { NULL }, }; static void usage(void) { errx(1, "Usage: lguest [--verbose] " "[--tunnet=(:|bridge::)\n" "|--block=|--initrd=]...\n" " vmlinux [args...]"); } /*L:105 The main routine is where the real work begins: */ int main(int argc, char *argv[]) { /* Memory, top-level pagetable, code startpoint and size of the * (optional) initrd. */ unsigned long mem = 0, start, initrd_size = 0; /* Two temporaries and the /dev/lguest file descriptor. */ int i, c, lguest_fd; /* The boot information for the Guest. */ struct boot_params *boot; /* If they specify an initrd file to load. */ const char *initrd_name = NULL; /* Save the args: we "reboot" by execing ourselves again. */ main_args = argv; /* We don't "wait" for the children, so prevent them from becoming * zombies. */ signal(SIGCHLD, SIG_IGN); /* First we initialize the device list. Since console and network * device receive input from a file descriptor, we keep an fdset * (infds) and the maximum fd number (max_infd) with the head of the * list. We also keep a pointer to the last device. Finally, we keep * the next interrupt number to use for devices (1: remember that 0 is * used by the timer). */ FD_ZERO(&devices.infds); devices.max_infd = -1; devices.lastdev = NULL; devices.next_irq = 1; cpu_id = 0; /* We need to know how much memory so we can set up the device * descriptor and memory pages for the devices as we parse the command * line. So we quickly look through the arguments to find the amount * of memory now. */ for (i = 1; i < argc; i++) { if (argv[i][0] != '-') { mem = atoi(argv[i]) * 1024 * 1024; /* We start by mapping anonymous pages over all of * guest-physical memory range. This fills it with 0, * and ensures that the Guest won't be killed when it * tries to access it. */ guest_base = map_zeroed_pages(mem / getpagesize() + DEVICE_PAGES); guest_limit = mem; guest_max = mem + DEVICE_PAGES*getpagesize(); devices.descpage = get_pages(1); break; } } /* The options are fairly straight-forward */ while ((c = getopt_long(argc, argv, "v", opts, NULL)) != EOF) { switch (c) { case 'v': verbose = true; break; case 't': setup_tun_net(optarg); break; case 'b': setup_block_file(optarg); break; case 'r': setup_rng(); break; case 'i': initrd_name = optarg; break; default: warnx("Unknown argument %s", argv[optind]); usage(); } } /* After the other arguments we expect memory and kernel image name, * followed by command line arguments for the kernel. */ if (optind + 2 > argc) usage(); verbose("Guest base is at %p\n", guest_base); /* We always have a console device */ setup_console(); /* We can timeout waiting for Guest network transmit. */ setup_timeout(); /* Now we load the kernel */ start = load_kernel(open_or_die(argv[optind+1], O_RDONLY)); /* Boot information is stashed at physical address 0 */ boot = from_guest_phys(0); /* Map the initrd image if requested (at top of physical memory) */ if (initrd_name) { initrd_size = load_initrd(initrd_name, mem); /* These are the location in the Linux boot header where the * start and size of the initrd are expected to be found. */ boot->hdr.ramdisk_image = mem - initrd_size; boot->hdr.ramdisk_size = initrd_size; /* The bootloader type 0xFF means "unknown"; that's OK. */ boot->hdr.type_of_loader = 0xFF; } /* The Linux boot header contains an "E820" memory map: ours is a * simple, single region. */ boot->e820_entries = 1; boot->e820_map[0] = ((struct e820entry) { 0, mem, E820_RAM }); /* The boot header contains a command line pointer: we put the command * line after the boot header. */ boot->hdr.cmd_line_ptr = to_guest_phys(boot + 1); /* We use a simple helper to copy the arguments separated by spaces. */ concat((char *)(boot + 1), argv+optind+2); /* Boot protocol version: 2.07 supports the fields for lguest. */ boot->hdr.version = 0x207; /* The hardware_subarch value of "1" tells the Guest it's an lguest. */ boot->hdr.hardware_subarch = 1; /* Tell the entry path not to try to reload segment registers. */ boot->hdr.loadflags |= KEEP_SEGMENTS; /* We tell the kernel to initialize the Guest: this returns the open * /dev/lguest file descriptor. */ lguest_fd = tell_kernel(start); /* We clone off a thread, which wakes the Launcher whenever one of the * input file descriptors needs attention. We call this the Waker, and * we'll cover it in a moment. */ setup_waker(lguest_fd); /* Finally, run the Guest. This doesn't return. */ run_guest(lguest_fd); } /*:*/ /*M:999 * Mastery is done: you now know everything I do. * * But surely you have seen code, features and bugs in your wanderings which * you now yearn to attack? That is the real game, and I look forward to you * patching and forking lguest into the Your-Name-Here-visor. * * Farewell, and good coding! * Rusty Russell. */