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Diffstat (limited to 'Documentation/lguest/lguest.c')
| -rw-r--r-- | Documentation/lguest/lguest.c | 1820 |
1 files changed, 0 insertions, 1820 deletions
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c deleted file mode 100644 index 4c1fc65a8b3..00000000000 --- a/Documentation/lguest/lguest.c +++ /dev/null @@ -1,1820 +0,0 @@ -/*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 <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 <zlib.h> -#include <assert.h> -#include <sched.h> -#include <limits.h> -#include <stddef.h> -#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_ring.h" -#include "asm-x86/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 2 pages: it must be a power of 2. */ -#define VIRTQUEUE_NUM 128 - -/*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 pipe to send commands to the waker process */ -static int waker_fd; -/* 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; - -/* 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; - - /* 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. */ - void (*handle_output)(int fd, struct virtqueue *me); -}; - -/* 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; -} - -/* 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) - -/* 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); - - 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/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; -} - -/* Once we know how much memory we have we can construct simple linear page - * tables which set virtual == physical which will get the Guest far enough - * into the boot to create its own. - * - * We lay them out of the way, just below the initrd (which is why we need to - * know its size here). */ -static unsigned long setup_pagetables(unsigned long mem, - unsigned long initrd_size) -{ - unsigned long *pgdir, *linear; - unsigned int mapped_pages, i, linear_pages; - unsigned int ptes_per_page = getpagesize()/sizeof(void *); - - mapped_pages = mem/getpagesize(); - - /* Each PTE page can map ptes_per_page pages: how many do we need? */ - linear_pages = (mapped_pages + ptes_per_page-1)/ptes_per_page; - - /* We put the toplevel page directory page at the top of memory. */ - pgdir = from_guest_phys(mem) - initrd_size - getpagesize(); - - /* Now we use the next linear_pages pages as pte pages */ - linear = (void *)pgdir - linear_pages*getpagesize(); - - /* Linear mapping is easy: put every page's address into the mapping in - * order. PAGE_PRESENT contains the flags Present, Writable and - * Executable. */ - for (i = 0; i < mapped_pages; i++) - linear[i] = ((i * getpagesize()) | PAGE_PRESENT); - - /* The top level points to the linear page table pages above. */ - for (i = 0; i < mapped_pages; i += ptes_per_page) { - pgdir[i/ptes_per_page] - = ((to_guest_phys(linear) + i*sizeof(void *)) - | PAGE_PRESENT); - } - - verbose("Linear mapping of %u pages in %u pte pages at %#lx\n", - mapped_pages, linear_pages, to_guest_phys(linear)); - - /* We return the top level (guest-physical) address: the kernel needs - * to know where it is. */ - return to_guest_phys(pgdir); -} -/*:*/ - -/* 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, the - * top level pagetable and the entry point for the Guest. */ -static int tell_kernel(unsigned long pgdir, unsigned long start) -{ - unsigned long args[] = { LHREQ_INITIALIZE, - (unsigned long)guest_base, - guest_limit / getpagesize(), pgdir, 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 fork off a process 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. - */ -static void wake_parent(int pipefd, int lguest_fd) -{ - /* Add the pipe from the Launcher to the fdset in the device_list, so - * we watch it, too. */ - add_device_fd(pipefd); - - for (;;) { - fd_set rfds = devices.infds; - unsigned long args[] = { LHREQ_BREAK, 1 }; - - /* Wait until input is ready from one of the devices. */ - select(devices.max_infd+1, &rfds, NULL, NULL, NULL); - /* Is it a message from the Launcher? */ - if (FD_ISSET(pipefd, &rfds)) { - int fd; - /* If read() returns 0, it means the Launcher has - * exited. We silently follow. */ - if (read(pipefd, &fd, sizeof(fd)) == 0) - exit(0); - /* Otherwise it's telling us to change what file - * descriptors we're to listen to. Positive means - * listen to a new one, negative means stop - * listening. */ - if (fd >= 0) - FD_SET(fd, &devices.infds); - else - FD_CLR(-fd - 1, &devices.infds); - } else /* Send LHREQ_BREAK command. */ - pwrite(lguest_fd, args, sizeof(args), cpu_id); - } -} - -/* This routine just sets up a pipe to the Waker process. */ -static int setup_waker(int lguest_fd) -{ - int pipefd[2], child; - - /* We create a pipe to talk to the Waker, and also so it knows when the - * Launcher dies (and closes pipe). */ - pipe(pipefd); - child = fork(); - if (child == -1) - err(1, "forking"); - - if (child == 0) { - /* We are the Waker: close the "writing" end of our copy of the - * pipe and start waiting for input. */ - close(pipefd[1]); - wake_parent(pipefd[0], lguest_fd); - } - /* Close the reading end of our copy of the pipe. */ - close(pipefd[0]); - - /* Here is the fd used to talk to the waker. */ - return pipefd[1]; -} - -/* - * 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; - - /* Check it isn't doing very strange things with descriptor numbers. */ - if ((u16)(vq->vring.avail->idx - vq->last_avail_idx) > vq->vring.num) - errx(1, "Guest moved used index from %u to %u", - vq->last_avail_idx, vq->vring.avail->idx); - - /* If there's nothing new since last we looked, return invalid. */ - if (vq->vring.avail->idx == vq->last_avail_idx) - return vq->vring.num; - - /* Grab the next descriptor number they're advertising, and increment - * the index we've seen. */ - head = vq->vring.avail->ring[vq->last_avail_idx++ % vq->vring.num]; - - /* 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); - - 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++; -} - -/* 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. */ - if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT) - 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_fd); - /* 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) -{ - 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); - } -} - -/* - * 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) -{ - 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?"); - /* Check header, but otherwise ignore it (we told the Guest we - * supported no features, so it shouldn't have anything - * interesting). */ - (void)convert(&iov[0], struct virtio_net_hdr); - len = writev(vq->dev->fd, iov+1, out-1); - add_used_and_trigger(fd, vq, head, len); - } -} - -/* 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]; - struct virtio_net_hdr *hdr; - - /* 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. */ - if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK) - warn("network: no dma buffer!"); - /* 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?"); - - /* First element is the header: we set it to 0 (no features). */ - hdr = convert(&iov[0], struct virtio_net_hdr); - hdr->flags = 0; - hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE; - - /* Read the packet from the device directly into the Guest's buffer. */ - len = readv(dev->fd, iov+1, in_num-1); - if (len <= 0) - err(1, "reading network"); - - /* Tell the Guest about the new packet. */ - add_used_and_trigger(fd, dev->vq, head, sizeof(*hdr) + 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) -{ - add_device_fd(vq->dev->fd); - /* Tell waker to listen to it again */ - write(waker_fd, &vq->dev->fd, sizeof(vq->dev->fd)); -} - -/* When the Guest asks us to reset a device, it's is fairly easy. */ -static void reset_device(struct device *dev) -{ - struct virtqueue *vq; - - verbose("Resetting device %s\n", dev->name); - /* Clear the status. */ - dev->desc->status = 0; - - /* 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, getpagesize())); - vq->last_avail_idx = 0; - } -} - -/* 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 reset the device. */ - if (from_guest_phys(addr) == i->desc) { - reset_device(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); - 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)); -} - -/* 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; - - /* If nothing is ready, we're done. */ - if (select(devices.max_infd+1, &fds, NULL, NULL, &poll) == 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)) { - int dev_fd; - 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); - /* Tell waker to ignore it too, by sending a - * negative fd number (-1, since 0 is a valid - * FD number). */ - dev_fd = -i->fd - 1; - write(waker_fd, &dev_fd, sizeof(dev_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 fd, struct virtqueue *me)) -{ - 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, getpagesize()) + getpagesize() - 1) - / getpagesize(); - p = get_pages(pages); - - /* Initialize the virtqueue */ - vq->next = NULL; - vq->last_avail_idx = 0; - vq->dev = dev; - - /* 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, getpagesize()); - - /* 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; - - /* 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++); -} -/*:*/ - -/*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 byte[4]; - - sscanf(ipaddr, "%u.%u.%u.%u", &byte[0], &byte[1], &byte[2], &byte[3]); - return (byte[0] << 24) | (byte[1] << 16) | (byte[2] << 8) | byte[3]; -} - -/* 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_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 *devname, u32 ipaddr, - unsigned char hwaddr[6]) -{ - struct ifreq ifr; - struct sockaddr_in *sin = (struct sockaddr_in *)&ifr.ifr_addr; - - /* Don't read these incantations. Just cut & paste them like I did! */ - memset(&ifr, 0, sizeof(ifr)); - strcpy(ifr.ifr_name, devname); - sin->sin_family = AF_INET; - sin->sin_addr.s_addr = htonl(ipaddr); - if (ioctl(fd, SIOCSIFADDR, &ifr) != 0) - err(1, "Setting %s interface address", devname); - ifr.ifr_flags = IFF_UP; - if (ioctl(fd, SIOCSIFFLAGS, &ifr) != 0) - err(1, "Bringing interface %s up", devname); - - /* SIOC stands for Socket I/O Control. G means Get (vs S for Set - * above). IF means Interface, and HWADDR is hardware address. - * Simple! */ - if (ioctl(fd, SIOCGIFHWADDR, &ifr) != 0) - err(1, "getting hw address for %s", devname); - memcpy(hwaddr, ifr.ifr_hwaddr.sa_data, 6); -} - -/*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(const char *arg) -{ - struct device *dev; - struct ifreq ifr; - int netfd, ipfd; - u32 ip; - const char *br_name = NULL; - struct virtio_net_config conf; - - /* 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); - memset(&ifr, 0, sizeof(ifr)); - ifr.ifr_flags = IFF_TAP | IFF_NO_PI; - strcpy(ifr.ifr_name, "tap%d"); - if (ioctl(netfd, TUNSETIFF, &ifr) != 0) - err(1, "configuring /dev/net/tun"); - /* We don't need checksums calculated for packets coming in this - * device: trust us! */ - ioctl(netfd, TUNSETNOCSUM, 1); - - /* 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, 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:<name> do bridging. */ - if (!strncmp(BRIDGE_PFX, arg, strlen(BRIDGE_PFX))) { - ip = INADDR_ANY; - br_name = arg + strlen(BRIDGE_PFX); - add_to_bridge(ipfd, ifr.ifr_name, br_name); - } else /* It is an IP address to set up the device with */ - ip = str2ip(arg); - - /* Set up the tun device, and get the mac address for the interface. */ - configure_device(ipfd, ifr.ifr_name, ip, conf.mac); - - /* Tell Guest what MAC address to use. */ - add_feature(dev, VIRTIO_NET_F_MAC); - set_config(dev, sizeof(conf), &conf); - - /* We don't need the socket any more; setup is done. */ - close(ipfd); - - verbose("device %u: tun net %u.%u.%u.%u\n", - devices.device_num++, - (u8)(ip>>24),(u8)(ip>>16),(u8)(ip>>8),(u8)ip); - if (br_name) - verbose("attached to bridge: %s\n", br_name); -} - -/* 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; - struct virtio_blk_inhdr *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], struct virtio_blk_inhdr); - 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->status = 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->status = (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->status = VIRTIO_BLK_S_OK; - } else { - wlen = sizeof(*in); - in->status = 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) -{ - 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)); -} -/* 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; - - /* Closing pipes causes the Waker thread and io_threads to die, and - * closing /dev/lguest cleans up the Guest. Since we don't track all - * open fds, we simply close everything beyond stderr. */ - for (i = 3; i < FD_SETSIZE; i++) - close(i); - 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 the Waker wanted us to look at some input. - * 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' }, - { "initrd", 1, NULL, 'i' }, - { NULL }, -}; -static void usage(void) -{ - errx(1, "Usage: lguest [--verbose] " - "[--tunnet=(<ipaddr>|bridge:<bridgename>)\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, top-level pagetable, code startpoint and size of the - * (optional) initrd. */ - unsigned long mem = 0, pgdir, 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 '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(); - - /* 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; - } - - /* Set up the initial linear pagetables, starting below the initrd. */ - pgdir = setup_pagetables(mem, initrd_size); - - /* 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(pgdir, start); - - /* We fork off a child process, 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. */ - waker_fd = 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. - */ |