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authorDavidlohr Bueso <dave@gnu.org>2012-01-12 15:44:47 +1030
committerRusty Russell <rusty@rustcorp.com.au>2012-01-12 15:44:47 +1030
commit07fe9977b6234ede1bd29e10e0323e478860c871 (patch)
tree802e48e78503b82953b9ff415f882fb6edb05dbc /tools
parent39082f7e5912cdc70f9ab0767e7342711f34b9f8 (diff)
downloadlinux-linaro-stable-07fe9977b6234ede1bd29e10e0323e478860c871.tar.gz
lguest: move the lguest tool to the tools directory
This is a better location instead of having it in Documentation. Signed-off-by: Davidlohr Bueso <dave@gnu.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (fixed compile)
Diffstat (limited to 'tools')
-rw-r--r--tools/lguest/.gitignore1
-rw-r--r--tools/lguest/Makefile8
-rw-r--r--tools/lguest/extract58
-rw-r--r--tools/lguest/lguest.c2065
-rw-r--r--tools/lguest/lguest.txt129
5 files changed, 2261 insertions, 0 deletions
diff --git a/tools/lguest/.gitignore b/tools/lguest/.gitignore
new file mode 100644
index 000000000000..115587fd5f65
--- /dev/null
+++ b/tools/lguest/.gitignore
@@ -0,0 +1 @@
+lguest
diff --git a/tools/lguest/Makefile b/tools/lguest/Makefile
new file mode 100644
index 000000000000..0ac34206f7a7
--- /dev/null
+++ b/tools/lguest/Makefile
@@ -0,0 +1,8 @@
+# This creates the demonstration utility "lguest" which runs a Linux guest.
+# Missing headers? Add "-I../../../include -I../../../arch/x86/include"
+CFLAGS:=-m32 -Wall -Wmissing-declarations -Wmissing-prototypes -O3 -U_FORTIFY_SOURCE
+
+all: lguest
+
+clean:
+ rm -f lguest
diff --git a/tools/lguest/extract b/tools/lguest/extract
new file mode 100644
index 000000000000..7730bb6e4b94
--- /dev/null
+++ b/tools/lguest/extract
@@ -0,0 +1,58 @@
+#! /bin/sh
+
+set -e
+
+PREFIX=$1
+shift
+
+trap 'rm -r $TMPDIR' 0
+TMPDIR=`mktemp -d`
+
+exec 3>/dev/null
+for f; do
+ while IFS="
+" read -r LINE; do
+ case "$LINE" in
+ *$PREFIX:[0-9]*:\**)
+ NUM=`echo "$LINE" | sed "s/.*$PREFIX:\([0-9]*\).*/\1/"`
+ if [ -f $TMPDIR/$NUM ]; then
+ echo "$TMPDIR/$NUM already exits prior to $f"
+ exit 1
+ fi
+ exec 3>>$TMPDIR/$NUM
+ echo $f | sed 's,\.\./,,g' > $TMPDIR/.$NUM
+ /bin/echo "$LINE" | sed -e "s/$PREFIX:[0-9]*//" -e "s/:\*/*/" >&3
+ ;;
+ *$PREFIX:[0-9]*)
+ NUM=`echo "$LINE" | sed "s/.*$PREFIX:\([0-9]*\).*/\1/"`
+ if [ -f $TMPDIR/$NUM ]; then
+ echo "$TMPDIR/$NUM already exits prior to $f"
+ exit 1
+ fi
+ exec 3>>$TMPDIR/$NUM
+ echo $f | sed 's,\.\./,,g' > $TMPDIR/.$NUM
+ /bin/echo "$LINE" | sed "s/$PREFIX:[0-9]*//" >&3
+ ;;
+ *:\**)
+ /bin/echo "$LINE" | sed -e "s/:\*/*/" -e "s,/\*\*/,," >&3
+ echo >&3
+ exec 3>/dev/null
+ ;;
+ *)
+ /bin/echo "$LINE" >&3
+ ;;
+ esac
+ done < $f
+ echo >&3
+ exec 3>/dev/null
+done
+
+LASTFILE=""
+for f in $TMPDIR/*; do
+ if [ "$LASTFILE" != $(cat $TMPDIR/.$(basename $f) ) ]; then
+ LASTFILE=$(cat $TMPDIR/.$(basename $f) )
+ echo "[ $LASTFILE ]"
+ fi
+ cat $f
+done
+
diff --git a/tools/lguest/lguest.c b/tools/lguest/lguest.c
new file mode 100644
index 000000000000..f759f4f097c7
--- /dev/null
+++ b/tools/lguest/lguest.c
@@ -0,0 +1,2065 @@
+/*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 43 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 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;
+
+ /* 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/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) {
+ 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) {
+ warn("Write to stdout gave %i (%d)", len, errno);
+ break;
+ }
+ 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)
+ warnx("Write to tun failed (%d)?", errno);
+
+ /*
+ * 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)
+ warn("Failed to read from tun (%d).", errno);
+
+ /*
+ * 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 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]);
+
+ 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->running)
+ err(1, "Device %s features finalized twice", dev->name);
+ 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 should not be used before features are finalized. */
+ for (vq = i->vq; vq; vq = vq->next) {
+ if (addr != vq->config.pfn*getpagesize())
+ continue;
+ errx(1, "Notification on %s before setup!", i->name);
+ }
+ }
+
+ /*
+ * 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 sophisticated 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 use a virtio network switch in the kernel, ie. vhost.
+:*/
+
+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);
+
+ /* 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, &notify_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);
+
+ /* Set kernel alignment to 16M (CONFIG_PHYSICAL_ALIGN) */
+ boot->hdr.kernel_alignment = 0x1000000;
+
+ /* 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. */
+ 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.
+ */
diff --git a/tools/lguest/lguest.txt b/tools/lguest/lguest.txt
new file mode 100644
index 000000000000..bff0c554485d
--- /dev/null
+++ b/tools/lguest/lguest.txt
@@ -0,0 +1,129 @@
+ __
+ (___()'`; Rusty's Remarkably Unreliable Guide to Lguest
+ /, /` - or, A Young Coder's Illustrated Hypervisor
+ \\"--\\ http://lguest.ozlabs.org
+
+Lguest is designed to be a minimal 32-bit x86 hypervisor for the Linux kernel,
+for Linux developers and users to experiment with virtualization with the
+minimum of complexity. Nonetheless, it should have sufficient features to
+make it useful for specific tasks, and, of course, you are encouraged to fork
+and enhance it (see drivers/lguest/README).
+
+Features:
+
+- Kernel module which runs in a normal kernel.
+- Simple I/O model for communication.
+- Simple program to create new guests.
+- Logo contains cute puppies: http://lguest.ozlabs.org
+
+Developer features:
+
+- Fun to hack on.
+- No ABI: being tied to a specific kernel anyway, you can change anything.
+- Many opportunities for improvement or feature implementation.
+
+Running Lguest:
+
+- The easiest way to run lguest is to use same kernel as guest and host.
+ You can configure them differently, but usually it's easiest not to.
+
+ You will need to configure your kernel with the following options:
+
+ "General setup":
+ "Prompt for development and/or incomplete code/drivers" = Y
+ (CONFIG_EXPERIMENTAL=y)
+
+ "Processor type and features":
+ "Paravirtualized guest support" = Y
+ "Lguest guest support" = Y
+ "High Memory Support" = off/4GB
+ "Alignment value to which kernel should be aligned" = 0x100000
+ (CONFIG_PARAVIRT=y, CONFIG_LGUEST_GUEST=y, CONFIG_HIGHMEM64G=n and
+ CONFIG_PHYSICAL_ALIGN=0x100000)
+
+ "Device Drivers":
+ "Block devices"
+ "Virtio block driver (EXPERIMENTAL)" = M/Y
+ "Network device support"
+ "Universal TUN/TAP device driver support" = M/Y
+ "Virtio network driver (EXPERIMENTAL)" = M/Y
+ (CONFIG_VIRTIO_BLK=m, CONFIG_VIRTIO_NET=m and CONFIG_TUN=m)
+
+ "Virtualization"
+ "Linux hypervisor example code" = M/Y
+ (CONFIG_LGUEST=m)
+
+- A tool called "lguest" is available in this directory: type "make"
+ to build it. If you didn't build your kernel in-tree, use "make
+ O=<builddir>".
+
+- Create or find a root disk image. There are several useful ones
+ around, such as the xm-test tiny root image at
+ http://xm-test.xensource.com/ramdisks/initrd-1.1-i386.img
+
+ For more serious work, I usually use a distribution ISO image and
+ install it under qemu, then make multiple copies:
+
+ dd if=/dev/zero of=rootfile bs=1M count=2048
+ qemu -cdrom image.iso -hda rootfile -net user -net nic -boot d
+
+ Make sure that you install a getty on /dev/hvc0 if you want to log in on the
+ console!
+
+- "modprobe lg" if you built it as a module.
+
+- Run an lguest as root:
+
+ Documentation/virtual/lguest/lguest 64 vmlinux --tunnet=192.168.19.1 \
+ --block=rootfile root=/dev/vda
+
+ Explanation:
+ 64: the amount of memory to use, in MB.
+
+ vmlinux: the kernel image found in the top of your build directory. You
+ can also use a standard bzImage.
+
+ --tunnet=192.168.19.1: configures a "tap" device for networking with this
+ IP address.
+
+ --block=rootfile: a file or block device which becomes /dev/vda
+ inside the guest.
+
+ root=/dev/vda: this (and anything else on the command line) are
+ kernel boot parameters.
+
+- Configuring networking. I usually have the host masquerade, using
+ "iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE" and "echo 1 >
+ /proc/sys/net/ipv4/ip_forward". In this example, I would configure
+ eth0 inside the guest at 192.168.19.2.
+
+ Another method is to bridge the tap device to an external interface
+ using --tunnet=bridge:<bridgename>, and perhaps run dhcp on the guest
+ to obtain an IP address. The bridge needs to be configured first:
+ this option simply adds the tap interface to it.
+
+ A simple example on my system:
+
+ ifconfig eth0 0.0.0.0
+ brctl addbr lg0
+ ifconfig lg0 up
+ brctl addif lg0 eth0
+ dhclient lg0
+
+ Then use --tunnet=bridge:lg0 when launching the guest.
+
+ See:
+
+ http://www.linuxfoundation.org/collaborate/workgroups/networking/bridge
+
+ for general information on how to get bridging to work.
+
+- Random number generation. Using the --rng option will provide a
+ /dev/hwrng in the guest that will read from the host's /dev/random.
+ Use this option in conjunction with rng-tools (see ../hw_random.txt)
+ to provide entropy to the guest kernel's /dev/random.
+
+There is a helpful mailing list at http://ozlabs.org/mailman/listinfo/lguest
+
+Good luck!
+Rusty Russell rusty@rustcorp.com.au.