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Diffstat (limited to 'Documentation/virtual/lguest/lguest.c')
| -rw-r--r-- | Documentation/virtual/lguest/lguest.c | 2095 |
1 files changed, 2095 insertions, 0 deletions
diff --git a/Documentation/virtual/lguest/lguest.c b/Documentation/virtual/lguest/lguest.c new file mode 100644 index 000000000000..d9da7e148538 --- /dev/null +++ b/Documentation/virtual/lguest/lguest.c @@ -0,0 +1,2095 @@ +/*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 <stdio.h> +#include <string.h> +#include <unistd.h> +#include <err.h> +#include <stdint.h> +#include <stdlib.h> +#include <elf.h> +#include <sys/mman.h> +#include <sys/param.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/wait.h> +#include <sys/eventfd.h> +#include <fcntl.h> +#include <stdbool.h> +#include <errno.h> +#include <ctype.h> +#include <sys/socket.h> +#include <sys/ioctl.h> +#include <sys/time.h> +#include <time.h> +#include <netinet/in.h> +#include <net/if.h> +#include <linux/sockios.h> +#include <linux/if_tun.h> +#include <sys/uio.h> +#include <termios.h> +#include <getopt.h> +#include <assert.h> +#include <sched.h> +#include <limits.h> +#include <stddef.h> +#include <signal.h> +#include <pwd.h> +#include <grp.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> +#include "../../include/linux/lguest_launcher.h" +/*L:110 + * We can ignore the 42 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 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) +/*:*/ + +/* 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 /dev/lguest file descriptor. */ +static int lguest_fd; + +/* 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 { + /* 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. */ + 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 device's descriptor, as mapped into the Guest. */ + struct lguest_device_desc *desc; + + /* We can't trust desc values once Guest has booted: we use these. */ + unsigned int feature_len; + unsigned int num_vq; + + /* The name of this device, for --verbose. */ + const char *name; + + /* Any queues attached to this device */ + struct virtqueue *vq; + + /* Is it operational */ + bool running; + + /* Does Guest want an intrrupt on empty? */ + bool irq_on_empty; + + /* 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; + + /* How many are used since we sent last irq? */ + unsigned int pending_used; + + /* Eventfd where Guest notifications arrive. */ + int eventfd; + + /* Function for the thread which is servicing this virtqueue. */ + void (*service)(struct virtqueue *vq); + pid_t thread; +}; + +/* Remember the arguments to the program so we can "reboot" */ +static char **main_args; + +/* The original tty settings to restore on exit. */ +static struct termios orig_term; + +/* + * We have to be careful with barriers: our devices are all run in separate + * threads and so we need to make sure that changes visible to the Guest happen + * in precise order. + */ +#define wmb() __asm__ __volatile__("" : : : "memory") +#define mb() __asm__ __volatile__("" : : : "memory") + +/* + * 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->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 its + * "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). We allocate an extra two pages PROT_NONE to act as guard + * pages against read/write attempts that exceed allocated space. + */ + addr = mmap(NULL, getpagesize() * (num+2), + PROT_NONE, MAP_PRIVATE, fd, 0); + + if (addr == MAP_FAILED) + err(1, "Mmapping %u pages of /dev/zero", num); + + if (mprotect(addr + getpagesize(), getpagesize() * num, + PROT_READ|PROT_WRITE) == -1) + err(1, "mprotect rw %u pages failed", num); + + /* + * One neat mmap feature is that you can close the fd, and it + * stays mapped. + */ + close(fd); + + /* Return address after PROT_NONE page */ + return addr + getpagesize(); +} + +/* 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, + 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 void tell_kernel(unsigned long start) +{ + unsigned long args[] = { LHREQ_INITIALIZE, + (unsigned long)guest_base, + guest_limit / getpagesize(), start }; + verbose("Guest: %p - %p (%#lx)\n", + guest_base, guest_base + guest_limit, guest_limit); + lguest_fd = open_or_die("/dev/lguest", O_RDWR); + if (write(lguest_fd, args, sizeof(args)) < 0) + err(1, "Writing to /dev/lguest"); +} +/*:*/ + +/*L:200 + * 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) +{ + /* + * Check if the requested address and size exceeds the allocated memory, + * or addr + size wraps around. + */ + if ((addr + size) > guest_limit || (addr + size) < addr) + 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 vring_desc *desc, + unsigned int i, unsigned int max) +{ + unsigned int next; + + /* If this descriptor says it doesn't chain, we're done. */ + if (!(desc[i].flags & VRING_DESC_F_NEXT)) + return max; + + /* Check they're not leading us off end of descriptors. */ + next = desc[i].next; + /* Make sure compiler knows to grab that: we don't want it changing! */ + wmb(); + + if (next >= max) + errx(1, "Desc next is %u", next); + + return next; +} + +/* + * This actually sends the interrupt for this virtqueue, if we've used a + * buffer. + */ +static void trigger_irq(struct virtqueue *vq) +{ + unsigned long buf[] = { LHREQ_IRQ, vq->config.irq }; + + /* Don't inform them if nothing used. */ + if (!vq->pending_used) + return; + vq->pending_used = 0; + + /* If they don't want an interrupt, don't send one... */ + if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT) { + /* ... unless they've asked us to force one on empty. */ + if (!vq->dev->irq_on_empty + || lg_last_avail(vq) != vq->vring.avail->idx) + return; + } + + /* Send the Guest an interrupt tell them we used something up. */ + if (write(lguest_fd, buf, sizeof(buf)) != 0) + err(1, "Triggering irq %i", vq->config.irq); +} + +/* + * This looks in the virtqueue 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 waits if necessary, and returns the descriptor number found. + */ +static unsigned wait_for_vq_desc(struct virtqueue *vq, + struct iovec iov[], + unsigned int *out_num, unsigned int *in_num) +{ + unsigned int i, head, max; + struct vring_desc *desc; + u16 last_avail = lg_last_avail(vq); + + /* There's nothing available? */ + while (last_avail == vq->vring.avail->idx) { + u64 event; + + /* + * Since we're about to sleep, now is a good time to tell the + * Guest about what we've used up to now. + */ + trigger_irq(vq); + + /* OK, now we need to know about added descriptors. */ + vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY; + + /* + * They could have slipped one in as we were doing that: make + * sure it's written, then check again. + */ + mb(); + if (last_avail != vq->vring.avail->idx) { + vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY; + break; + } + + /* Nothing new? Wait for eventfd to tell us they refilled. */ + if (read(vq->eventfd, &event, sizeof(event)) != sizeof(event)) + errx(1, "Event read failed?"); + + /* We don't need to be notified again. */ + vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY; + } + + /* Check it isn't doing very strange things with descriptor numbers. */ + 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); + + /* + * 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; + + max = vq->vring.num; + desc = vq->vring.desc; + i = head; + + /* + * If this is an indirect entry, then this buffer contains a descriptor + * table which we handle as if it's any normal descriptor chain. + */ + if (desc[i].flags & VRING_DESC_F_INDIRECT) { + if (desc[i].len % sizeof(struct vring_desc)) + errx(1, "Invalid size for indirect buffer table"); + + max = desc[i].len / sizeof(struct vring_desc); + desc = check_pointer(desc[i].addr, desc[i].len); + i = 0; + } + + do { + /* Grab the first descriptor, and check it's OK. */ + iov[*out_num + *in_num].iov_len = desc[i].len; + iov[*out_num + *in_num].iov_base + = check_pointer(desc[i].addr, desc[i].len); + /* If this is an input descriptor, increment that count. */ + if (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 > max) + errx(1, "Looped descriptor"); + } while ((i = next_desc(desc, i, max)) != max); + + return head; +} + +/* + * After we've used one of their buffers, we tell the Guest about it. Sometime + * later we'll want to send them an interrupt using trigger_irq(); note that + * wait_for_vq_desc() does that for us if it has to wait. + */ +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->pending_used++; +} + +/* And here's the combo meal deal. Supersize me! */ +static void add_used_and_trigger(struct virtqueue *vq, unsigned head, int len) +{ + add_used(vq, head, len); + trigger_irq(vq); +} + +/* + * The Console + * + * 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 void console_input(struct virtqueue *vq) +{ + int len; + unsigned int head, in_num, out_num; + struct console_abort *abort = vq->dev->priv; + struct iovec iov[vq->vring.num]; + + /* Make sure there's a descriptor available. */ + head = wait_for_vq_desc(vq, iov, &out_num, &in_num); + if (out_num) + errx(1, "Output buffers in console in queue?"); + + /* Read into it. This is where we usually wait. */ + len = readv(STDIN_FILENO, iov, in_num); + if (len <= 0) { + /* Ran out of input? */ + warnx("Failed to get console input, ignoring console."); + /* + * For simplicity, dying threads kill the whole Launcher. So + * just nap here. + */ + for (;;) + pause(); + } + + /* Tell the Guest we used a buffer. */ + add_used_and_trigger(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) { + abort->count = 0; + return; + } + + abort->count++; + if (abort->count == 1) + gettimeofday(&abort->start, NULL); + else if (abort->count == 3) { + struct timeval now; + gettimeofday(&now, NULL); + /* Kill all Launcher processes with SIGINT, like normal ^C */ + if (now.tv_sec <= abort->start.tv_sec+1) + kill(0, SIGINT); + abort->count = 0; + } +} + +/* This is the routine which handles console output (ie. stdout). */ +static void console_output(struct virtqueue *vq) +{ + unsigned int head, out, in; + struct iovec iov[vq->vring.num]; + + /* We usually wait in here, for the Guest to give us something. */ + head = wait_for_vq_desc(vq, iov, &out, &in); + if (in) + errx(1, "Input buffers in console output queue?"); + + /* writev can return a partial write, so we loop here. */ + while (!iov_empty(iov, out)) { + int len = writev(STDOUT_FILENO, iov, out); + if (len <= 0) + err(1, "Write to stdout gave %i", len); + iov_consume(iov, out, len); + } + + /* + * We're finished with that buffer: if we're going to sleep, + * wait_for_vq_desc() will prod the Guest with an interrupt. + */ + add_used(vq, head, 0); +} + +/* + * The Network + * + * Handling output for network is also simple: we get all the output buffers + * and write them to /dev/net/tun. + */ +struct net_info { + int tunfd; +}; + +static void net_output(struct virtqueue *vq) +{ + struct net_info *net_info = vq->dev->priv; + unsigned int head, out, in; + struct iovec iov[vq->vring.num]; + + /* We usually wait in here for the Guest to give us a packet. */ + head = wait_for_vq_desc(vq, iov, &out, &in); + if (in) + errx(1, "Input buffers in net output queue?"); + /* + * Send the whole thing through to /dev/net/tun. It expects the exact + * same format: what a coincidence! + */ + if (writev(net_info->tunfd, iov, out) < 0) + errx(1, "Write to tun failed?"); + + /* + * Done with that one; wait_for_vq_desc() will send the interrupt if + * all packets are processed. + */ + add_used(vq, head, 0); +} + +/* + * Handling network input is a bit trickier, because I've tried to optimize it. + * + * First we have a helper routine which tells is if from this file descriptor + * (ie. the /dev/net/tun device) will block: + */ +static bool will_block(int fd) +{ + fd_set fdset; + struct timeval zero = { 0, 0 }; + FD_ZERO(&fdset); + FD_SET(fd, &fdset); + return select(fd+1, &fdset, NULL, NULL, &zero) != 1; +} + +/* + * This handles packets coming in from the tun device to our Guest. Like all + * service routines, it gets called again as soon as it returns, so you don't + * see a while(1) loop here. + */ +static void net_input(struct virtqueue *vq) +{ + int len; + unsigned int head, out, in; + struct iovec iov[vq->vring.num]; + struct net_info *net_info = vq->dev->priv; + + /* + * Get a descriptor to write an incoming packet into. This will also + * send an interrupt if they're out of descriptors. + */ + head = wait_for_vq_desc(vq, iov, &out, &in); + if (out) + errx(1, "Output buffers in net input queue?"); + + /* + * If it looks like we'll block reading from the tun device, send them + * an interrupt. + */ + if (vq->pending_used && will_block(net_info->tunfd)) + trigger_irq(vq); + + /* + * Read in the packet. This is where we normally wait (when there's no + * incoming network traffic). + */ + len = readv(net_info->tunfd, iov, in); + if (len <= 0) + err(1, "Failed to read from tun."); + + /* + * Mark that packet buffer as used, but don't interrupt here. We want + * to wait until we've done as much work as we can. + */ + add_used(vq, head, len); +} +/*:*/ + +/* This is the helper to create threads: run the service routine in a loop. */ +static int do_thread(void *_vq) +{ + struct virtqueue *vq = _vq; + + for (;;) + vq->service(vq); + return 0; +} + +/* + * When a child dies, we kill our entire process group with SIGTERM. This + * also has the side effect that the shell restores the console for us! + */ +static void kill_launcher(int signal) +{ + kill(0, SIGTERM); +} + +static void reset_device(struct device *dev) +{ + struct virtqueue *vq; + + verbose("Resetting device %s\n", dev->name); + + /* Clear any features they've acked. */ + memset(get_feature_bits(dev) + dev->feature_len, 0, dev->feature_len); + + /* We're going to be explicitly killing threads, so ignore them. */ + signal(SIGCHLD, SIG_IGN); + + /* Zero out the virtqueues, get rid of their threads */ + for (vq = dev->vq; vq; vq = vq->next) { + if (vq->thread != (pid_t)-1) { + kill(vq->thread, SIGTERM); + waitpid(vq->thread, NULL, 0); + vq->thread = (pid_t)-1; + } + memset(vq->vring.desc, 0, + vring_size(vq->config.num, LGUEST_VRING_ALIGN)); + lg_last_avail(vq) = 0; + } + dev->running = false; + + /* Now we care if threads die. */ + signal(SIGCHLD, (void *)kill_launcher); +} + +/*L:216 + * This actually creates the thread which services the virtqueue for a device. + */ +static void create_thread(struct virtqueue *vq) +{ + /* + * Create stack for thread. Since the stack grows upwards, we point + * the stack pointer to the end of this region. + */ + char *stack = malloc(32768); + unsigned long args[] = { LHREQ_EVENTFD, + vq->config.pfn*getpagesize(), 0 }; + + /* Create a zero-initialized eventfd. */ + vq->eventfd = eventfd(0, 0); + if (vq->eventfd < 0) + err(1, "Creating eventfd"); + args[2] = vq->eventfd; + + /* + * Attach an eventfd to this virtqueue: it will go off when the Guest + * does an LHCALL_NOTIFY for this vq. + */ + if (write(lguest_fd, &args, sizeof(args)) != 0) + err(1, "Attaching eventfd"); + + /* + * CLONE_VM: because it has to access the Guest memory, and SIGCHLD so + * we get a signal if it dies. + */ + vq->thread = clone(do_thread, stack + 32768, CLONE_VM | SIGCHLD, vq); + if (vq->thread == (pid_t)-1) + err(1, "Creating clone"); + + /* We close our local copy now the child has it. */ + close(vq->eventfd); +} + +static bool accepted_feature(struct device *dev, unsigned int bit) +{ + const u8 *features = get_feature_bits(dev) + dev->feature_len; + + if (dev->feature_len < bit / CHAR_BIT) + return false; + return features[bit / CHAR_BIT] & (1 << (bit % CHAR_BIT)); +} + +static void start_device(struct device *dev) +{ + unsigned int i; + struct virtqueue *vq; + + verbose("Device %s OK: offered", dev->name); + for (i = 0; i < dev->feature_len; i++) + verbose(" %02x", get_feature_bits(dev)[i]); + verbose(", accepted"); + for (i = 0; i < dev->feature_len; i++) + verbose(" %02x", get_feature_bits(dev) + [dev->feature_len+i]); + + dev->irq_on_empty = accepted_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY); + + for (vq = dev->vq; vq; vq = vq->next) { + if (vq->service) + create_thread(vq); + } + dev->running = true; +} + +static void cleanup_devices(void) +{ + struct device *dev; + + for (dev = devices.dev; dev; dev = dev->next) + reset_device(dev); + + /* If we saved off the original terminal settings, restore them now. */ + if (orig_term.c_lflag & (ISIG|ICANON|ECHO)) + tcsetattr(STDIN_FILENO, TCSANOW, &orig_term); +} + +/* When the Guest tells us they updated the status field, we handle it. */ +static void update_device_status(struct device *dev) +{ + /* A zero status is a reset, otherwise it's a set of flags. */ + if (dev->desc->status == 0) + reset_device(dev); + else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) { + warnx("Device %s configuration FAILED", dev->name); + if (dev->running) + reset_device(dev); + } else if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK) { + if (!dev->running) + start_device(dev); + } +} + +/*L:215 + * This is the generic routine we call when the Guest uses LHCALL_NOTIFY. In + * particular, it's used to notify us of device status changes during boot. + */ +static void handle_output(unsigned long addr) +{ + struct device *i; + + /* Check each device. */ + for (i = devices.dev; i; i = i->next) { + struct virtqueue *vq; + + /* + * Notifications to device descriptors mean they updated the + * device status. + */ + if (from_guest_phys(addr) == i->desc) { + update_device_status(i); + return; + } + + /* + * Devices *can* be used before status is set to DRIVER_OK. + * The original plan was that they would never do this: they + * would always finish setting up their status bits before + * actually touching the virtqueues. In practice, we allowed + * them to, and they do (eg. the disk probes for partition + * tables as part of initialization). + * + * If we see this, we start the device: once it's running, we + * expect the device to catch all the notifications. + */ + for (vq = i->vq; vq; vq = vq->next) { + if (addr != vq->config.pfn*getpagesize()) + continue; + if (i->running) + errx(1, "Notification on running %s", i->name); + /* This just calls create_thread() for each virtqueue */ + start_device(i); + return; + } + } + + /* + * Early console write is done using notify on a nul-terminated string + * in Guest memory. It's also great for hacking debugging messages + * into a Guest. + */ + 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)); +} + +/*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->num_vq * sizeof(struct lguest_vqconfig) + + dev->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 (*service)(struct virtqueue *)) +{ + 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; + + /* + * This is the routine the service thread will run, and its Process ID + * once it's running. + */ + vq->service = service; + vq->thread = (pid_t)-1; + + /* 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->num_vq++; + 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; +} + +/* + * 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->feature_len = 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; + + /* Size must fit in config_len field (8 bits)! */ + assert(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. We + * don't actually start the service threads until later. + * + * See what I mean about userspace being boring? + */ +static struct device *new_device(const char *name, u16 type) +{ + struct device *dev = malloc(sizeof(*dev)); + + /* Now we populate the fields one at a time. */ + dev->desc = new_dev_desc(type); + dev->name = name; + dev->vq = NULL; + dev->feature_len = 0; + dev->num_vq = 0; + dev->running = false; + + /* + * 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); + } + + dev = new_device("console", VIRTIO_ID_CONSOLE); + + /* 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, console_input); + add_virtqueue(dev, VIRTQUEUE_NUM, console_output); + + verbose("device %u: console\n", ++devices.device_num); +} +/*:*/ + +/*M:010 + * Inter-guest networking is an interesting area. Simplest is to have a + * --sharenet=<name> 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; + + 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); + memcpy(&ifr.ifr_addr, &sin, sizeof(sin)); + 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; + struct net_info *net_info = malloc(sizeof(*net_info)); + int ipfd; + u32 ip = INADDR_ANY; + bool bridging = false; + char tapif[IFNAMSIZ], *p; + struct virtio_net_config conf; + + net_info->tunfd = get_tun_device(tapif); + + /* First we create a new network device. */ + dev = new_device("net", VIRTIO_ID_NET); + dev->priv = net_info; + + /* Network devices need a recv and a send queue, just like console. */ + add_virtqueue(dev, VIRTQUEUE_NUM, net_input); + add_virtqueue(dev, VIRTQUEUE_NUM, 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:<name> 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); + /* We handle indirect ring entries */ + add_feature(dev, VIRTIO_RING_F_INDIRECT_DESC); + 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); +} +/*:*/ + +/* This hangs off device->priv. */ +struct vblk_info { + /* The size of the file. */ + off64_t len; + + /* The file descriptor for the file. */ + int fd; + +}; + +/*L:210 + * The Disk + * + * The disk only has one virtqueue, so it only has one thread. It is really + * simple: the Guest asks for a block number and we read or write that position + * in the file. + * + * Before we serviced each virtqueue in a separate thread, that was unacceptably + * slow: the Guest waits until the read is finished before running anything + * else, even if it could have been doing useful work. + * + * We could have used 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. + */ +static void blk_request(struct virtqueue *vq) +{ + struct vblk_info *vblk = vq->dev->priv; + unsigned int head, out_num, in_num, wlen; + int ret; + u8 *in; + struct virtio_blk_outhdr *out; + struct iovec iov[vq->vring.num]; + off64_t off; + + /* + * Get the next request, where we normally wait. It triggers the + * interrupt to acknowledge previously serviced requests (if any). + */ + head = wait_for_vq_desc(vq, iov, &out_num, &in_num); + + /* + * 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); + /* + * For historical reasons, block operations are expressed in 512 byte + * "sectors". + */ + off = out->sector * 512; + + /* + * 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 if (out->type & VIRTIO_BLK_T_FLUSH) { + /* Flush */ + ret = fdatasync(vblk->fd); + verbose("FLUSH fdatasync: %i\n", 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; + } + } + + /* Finished that request. */ + add_used(vq, head, wlen); +} + +/*L:198 This actually sets up a virtual block device. */ +static void setup_block_file(const char *filename) +{ + struct device *dev; + struct vblk_info *vblk; + struct virtio_blk_config conf; + + /* Creat the device. */ + dev = new_device("block", VIRTIO_ID_BLOCK); + + /* The device has one virtqueue, where the Guest places requests. */ + add_virtqueue(dev, VIRTQUEUE_NUM, blk_request); + + /* 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 FLUSH. */ + add_feature(dev, VIRTIO_BLK_F_FLUSH); + + /* 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); + + /* Don't try to put whole struct: we have 8 bit limit. */ + set_config(dev, offsetof(struct virtio_blk_config, geometry), &conf); + + verbose("device %u: virtblock %llu sectors\n", + ++devices.device_num, le64_to_cpu(conf.capacity)); +} + +/*L:211 + * 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. + */ +struct rng_info { + int rfd; +}; + +static void rng_input(struct virtqueue *vq) +{ + int len; + unsigned int head, in_num, out_num, totlen = 0; + struct rng_info *rng_info = vq->dev->priv; + struct iovec iov[vq->vring.num]; + + /* First we need a buffer from the Guests's virtqueue. */ + head = wait_for_vq_desc(vq, iov, &out_num, &in_num); + if (out_num) + errx(1, "Output buffers in rng?"); + + /* + * Just like the console write, we loop to cover the whole iovec. + * In this case, short reads actually happen quite a bit. + */ + while (!iov_empty(iov, in_num)) { + len = readv(rng_info->rfd, 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(vq, head, totlen); +} + +/*L:199 + * This creates a "hardware" random number device for the Guest. + */ +static void setup_rng(void) +{ + struct device *dev; + struct rng_info *rng_info = malloc(sizeof(*rng_info)); + + /* Our device's privat info simply contains the /dev/random fd. */ + rng_info->rfd = open_or_die("/dev/random", O_RDONLY); + + /* Create the new device. */ + dev = new_device("rng", VIRTIO_ID_RNG); + dev->priv = rng_info; + + /* The device has one virtqueue, where the Guest places inbufs. */ + add_virtqueue(dev, VIRTQUEUE_NUM, rng_input); + + 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); + + /* Reset all the devices (kills all threads). */ + cleanup_devices(); + + 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(void) +{ + for (;;) { + 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(notify_addr); + /* 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(); + /* Anything else means a bug or incompatible change. */ + } else + err(1, "Running guest failed"); + } +} +/*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' }, + { "username", 1, NULL, 'u' }, + { "chroot", 1, NULL, 'c' }, + { NULL }, +}; +static void usage(void) +{ + errx(1, "Usage: lguest [--verbose] " + "[--tunnet=(<ipaddr>:<macaddr>|bridge:<bridgename>:<macaddr>)\n" + "|--block=<filename>|--initrd=<filename>]...\n" + "<mem-in-mb> vmlinux [args...]"); +} + +/*L:105 The main routine is where the real work begins: */ +int main(int argc, char *argv[]) +{ + /* Memory, code startpoint and size of the (optional) initrd. */ + unsigned long mem = 0, start, initrd_size = 0; + /* Two temporaries. */ + int i, c; + /* The boot information for the Guest. */ + struct boot_params *boot; + /* If they specify an initrd file to load. */ + const char *initrd_name = NULL; + + /* Password structure for initgroups/setres[gu]id */ + struct passwd *user_details = NULL; + + /* Directory to chroot to */ + char *chroot_path = NULL; + + /* Save the args: we "reboot" by execing ourselves again. */ + main_args = argv; + + /* + * First we initialize the device list. We keep a pointer to the last + * device, and the next interrupt number to use for devices (1: + * remember that 0 is used by the timer). + */ + devices.lastdev = NULL; + devices.next_irq = 1; + + /* We're CPU 0. In fact, that's the only CPU possible right now. */ + 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; + case 'u': + user_details = getpwnam(optarg); + if (!user_details) + err(1, "getpwnam failed, incorrect username?"); + break; + case 'c': + chroot_path = 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(); + + /* 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. + */ + tell_kernel(start); + + /* Ensure that we terminate if a device-servicing child dies. */ + signal(SIGCHLD, kill_launcher); + + /* If we exit via err(), this kills all the threads, restores tty. */ + atexit(cleanup_devices); + + /* If requested, chroot to a directory */ + if (chroot_path) { + if (chroot(chroot_path) != 0) + err(1, "chroot(\"%s\") failed", chroot_path); + + if (chdir("/") != 0) + err(1, "chdir(\"/\") failed"); + + verbose("chroot done\n"); + } + + /* If requested, drop privileges */ + if (user_details) { + uid_t u; + gid_t g; + + u = user_details->pw_uid; + g = user_details->pw_gid; + + if (initgroups(user_details->pw_name, g) != 0) + err(1, "initgroups failed"); + + if (setresgid(g, g, g) != 0) + err(1, "setresgid failed"); + + if (setresuid(u, u, u) != 0) + err(1, "setresuid failed"); + + verbose("Dropping privileges completed\n"); + } + + /* Finally, run the Guest. This doesn't return. */ + run_guest(); +} +/*:*/ + +/*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. + */ |