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Diffstat (limited to 'Documentation/lguest/lguest.c')
| -rw-r--r-- | Documentation/lguest/lguest.c | 1524 |
1 files changed, 0 insertions, 1524 deletions
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c deleted file mode 100644 index 103e346c8b6..00000000000 --- a/Documentation/lguest/lguest.c +++ /dev/null @@ -1,1524 +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 reads repeatedly from /dev/lguest to run the Guest. - * - * The only trick: the Makefile links it at a high address so it will be clear - * of the guest memory region. It means that each Guest cannot have more than - * about 2.5G of memory on a normally configured Host. :*/ -#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/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> -/*L:110 We can ignore the 28 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 and the header we need uses them, so we define them - * here. - */ -typedef unsigned long long u64; -typedef uint32_t u32; -typedef uint16_t u16; -typedef uint8_t u8; -#include "../../include/linux/lguest_launcher.h" -#include "../../include/asm-x86/e820_32.h" -/*:*/ - -#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 - -/*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 top of guest physical memory. */ -static u32 top; - -/* 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; - - /* The descriptor page for the devices. */ - struct lguest_device_desc *descs; - - /* A single linked list of devices. */ - struct device *dev; - /* ... And an end pointer so we can easily append new devices */ - struct device **lastdev; -}; - -/* The device structure describes a single device. */ -struct device -{ - /* The linked-list pointer. */ - struct device *next; - /* The descriptor for this device, as mapped into the Guest. */ - struct lguest_device_desc *desc; - /* The memory page(s) of this device, if any. Also mapped in Guest. */ - void *mem; - - /* 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); - - /* If handle_output is set, it wants to be called when the Guest sends - * DMA to this key. */ - unsigned long watch_key; - u32 (*handle_output)(int fd, const struct iovec *iov, - unsigned int num, struct device *me); - - /* Device-specific data. */ - void *priv; -}; - -/*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 (page-aligned) address and a number of pages. */ -static void *map_zeroed_pages(unsigned long addr, unsigned int num) -{ - /* We cache the /dev/zero file-descriptor so we only open it once. */ - static int fd = -1; - - if (fd == -1) - fd = open_or_die("/dev/zero", O_RDONLY); - - /* We use a private mapping (ie. if we write to the page, it will be - * copied), and obviously we insist that it be mapped where we ask. */ - if (mmap((void *)addr, getpagesize() * num, - PROT_READ|PROT_WRITE|PROT_EXEC, MAP_FIXED|MAP_PRIVATE, fd, 0) - != (void *)addr) - err(1, "Mmaping %u pages of /dev/zero @%p", num, (void *)addr); - - /* Returning the address is just a courtesy: can simplify callers. */ - return (void *)addr; -} - -/* To find out where to start we look for the magic Guest string, which marks - * the code we see in lguest_asm.S. This is a hack which we are currently - * plotting to replace with the normal Linux entry point. */ -static unsigned long entry_point(void *start, void *end, - unsigned long page_offset) -{ - void *p; - - /* The scan gives us the physical starting address. We want the - * virtual address in this case, and fortunately, we already figured - * out the physical-virtual difference and passed it here in - * "page_offset". */ - for (p = start; p < end; p++) - if (memcmp(p, "GenuineLguest", strlen("GenuineLguest")) == 0) - return (long)p + strlen("GenuineLguest") + page_offset; - - err(1, "Is this image a genuine lguest?"); -} - -/* 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. The Guest kernel expects to be placed in memory at the physical - * address, and the page tables set up so it will correspond to that virtual - * address. We return the difference between the virtual and physical - * addresses in the "page_offset" pointer. - * - * We return the starting address. */ -static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr, - unsigned long *page_offset) -{ - void *addr; - Elf32_Phdr phdr[ehdr->e_phnum]; - unsigned int i; - unsigned long start = -1UL, end = 0; - - /* 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"); - - /* We don't know page_offset yet. */ - *page_offset = 0; - - /* Try all the headers: there are usually only three. A read-only one, - * a read-write one, and a "note" section which isn't loadable. */ - 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 expect a simple linear address space: every segment must - * have the same difference between virtual (p_vaddr) and - * physical (p_paddr) address. */ - if (!*page_offset) - *page_offset = phdr[i].p_vaddr - phdr[i].p_paddr; - else if (*page_offset != phdr[i].p_vaddr - phdr[i].p_paddr) - errx(1, "Page offset of section %i different", i); - - /* We track the first and last address we mapped, so we can - * tell entry_point() where to scan. */ - if (phdr[i].p_paddr < start) - start = phdr[i].p_paddr; - if (phdr[i].p_paddr + phdr[i].p_filesz > end) - end = phdr[i].p_paddr + phdr[i].p_filesz; - - /* We map this section of the file at its physical address. We - * map it read & write even if the header says this segment is - * read-only. The kernel really wants to be writable: it - * patches its own instructions which would normally be - * read-only. - * - * MAP_PRIVATE means that the page won't be copied until a - * write is done to it. This allows us to share much of the - * kernel memory between Guests. */ - addr = mmap((void *)phdr[i].p_paddr, - phdr[i].p_filesz, - PROT_READ|PROT_WRITE|PROT_EXEC, - MAP_FIXED|MAP_PRIVATE, - elf_fd, phdr[i].p_offset); - if (addr != (void *)phdr[i].p_paddr) - err(1, "Mmaping vmlinux seg %i gave %p not %p", - i, addr, (void *)phdr[i].p_paddr); - } - - return entry_point((void *)start, (void *)end, *page_offset); -} - -/*L:170 Prepare to be SHOCKED and AMAZED. And possibly a trifle nauseated. - * - * We know that CONFIG_PAGE_OFFSET sets what virtual address the kernel expects - * to be. We don't know what that option was, but we can figure it out - * approximately by looking at the addresses in the code. I chose the common - * case of reading a memory location into the %eax register: - * - * movl <some-address>, %eax - * - * This gets encoded as five bytes: "0xA1 <4-byte-address>". For example, - * "0xA1 0x18 0x60 0x47 0xC0" reads the address 0xC0476018 into %eax. - * - * In this example can guess that the kernel was compiled with - * CONFIG_PAGE_OFFSET set to 0xC0000000 (it's always a round number). If the - * kernel were larger than 16MB, we might see 0xC1 addresses show up, but our - * kernel isn't that bloated yet. - * - * Unfortunately, x86 has variable-length instructions, so finding this - * particular instruction properly involves writing a disassembler. Instead, - * we rely on statistics. We look for "0xA1" and tally the different bytes - * which occur 4 bytes later (the "0xC0" in our example above). When one of - * those bytes appears three times, we can be reasonably confident that it - * forms the start of CONFIG_PAGE_OFFSET. - * - * This is amazingly reliable. */ -static unsigned long intuit_page_offset(unsigned char *img, unsigned long len) -{ - unsigned int i, possibilities[256] = { 0 }; - - for (i = 0; i + 4 < len; i++) { - /* mov 0xXXXXXXXX,%eax */ - if (img[i] == 0xA1 && ++possibilities[img[i+4]] > 3) - return (unsigned long)img[i+4] << 24; - } - errx(1, "could not determine page offset"); -} - -/*L:160 Unfortunately the entire ELF image isn't compressed: the segments - * which need loading are extracted and compressed raw. This denies us the - * information we need to make a fully-general loader. */ -static unsigned long unpack_bzimage(int fd, unsigned long *page_offset) -{ - gzFile f; - int ret, len = 0; - /* A bzImage always gets loaded at physical address 1M. This is - * actually configurable as CONFIG_PHYSICAL_START, but as the comment - * there says, "Don't change this unless you know what you are doing". - * Indeed. */ - void *img = (void *)0x100000; - - /* gzdopen takes our file descriptor (carefully placed at the start of - * the GZIP header we found) and returns a gzFile. */ - f = gzdopen(fd, "rb"); - /* We read it into memory in 64k chunks until we hit the end. */ - while ((ret = gzread(f, img + len, 65536)) > 0) - len += ret; - if (ret < 0) - err(1, "reading image from bzImage"); - - verbose("Unpacked size %i addr %p\n", len, img); - - /* Without the ELF header, we can't tell virtual-physical gap. This is - * CONFIG_PAGE_OFFSET, and people do actually change it. Fortunately, - * I have a clever way of figuring it out from the code itself. */ - *page_offset = intuit_page_offset(img, len); - - return entry_point(img, img + len, *page_offset); -} - -/*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 can't do that - * because the Guest can't run the unpacking code, and adding features to - * lguest kills puppies, so we don't want to. - * - * The bzImage is formed by putting the decompressing code in front of the - * compressed kernel code. So we can simple scan through it looking for the - * first "gzip" header, and start decompressing from there. */ -static unsigned long load_bzimage(int fd, unsigned long *page_offset) -{ - unsigned char c; - int state = 0; - - /* GZIP header is 0x1F 0x8B <method> <flags>... <compressed-by>. */ - while (read(fd, &c, 1) == 1) { - switch (state) { - case 0: - if (c == 0x1F) - state++; - break; - case 1: - if (c == 0x8B) - state++; - else - state = 0; - break; - case 2 ... 8: - state++; - break; - case 9: - /* Seek back to the start of the gzip header. */ - lseek(fd, -10, SEEK_CUR); - /* One final check: "compressed under UNIX". */ - if (c != 0x03) - state = -1; - else - return unpack_bzimage(fd, page_offset); - } - } - errx(1, "Could not find kernel in bzImage"); -} - -/*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 some funky - * coding, we can load those, too. */ -static unsigned long load_kernel(int fd, unsigned long *page_offset) -{ - 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, page_offset); - - /* Otherwise we assume it's a bzImage, and try to unpack it */ - return load_bzimage(fd, page_offset); -} - -/* 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; - void *iaddr; - - 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); - - /* The length needs to be rounded up to a page size: mmap needs the - * address to be page aligned. */ - len = page_align(st.st_size); - /* We map the initrd at the top of memory. */ - iaddr = mmap((void *)mem - len, st.st_size, - PROT_READ|PROT_EXEC|PROT_WRITE, - MAP_FIXED|MAP_PRIVATE, ifd, 0); - if (iaddr != (void *)mem - len) - err(1, "Mmaping initrd '%s' returned %p not %p", - name, iaddr, (void *)mem - len); - /* 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, st.st_size, iaddr); - - /* We return the initrd size. */ - return len; -} - -/* Once we know how much memory we have, and the address the Guest kernel - * expects, we can construct simple linear page tables 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). */ -static unsigned long setup_pagetables(unsigned long mem, - unsigned long initrd_size, - unsigned long page_offset) -{ - u32 *pgdir, *linear; - unsigned int mapped_pages, i, linear_pages; - unsigned int ptes_per_page = getpagesize()/sizeof(u32); - - /* Ideally we map all physical memory starting at page_offset. - * However, if page_offset is 0xC0000000 we can only map 1G of physical - * (0xC0000000 + 1G overflows). */ - if (mem <= -page_offset) - mapped_pages = mem/getpagesize(); - else - mapped_pages = -page_offset/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 = (void *)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. The - * entry representing page_offset points to the first one, and they - * continue from there. */ - for (i = 0; i < mapped_pages; i += ptes_per_page) { - pgdir[(i + page_offset/getpagesize())/ptes_per_page] - = (((u32)linear + i*sizeof(u32)) | PAGE_PRESENT); - } - - verbose("Linear mapping of %u pages in %u pte pages at %p\n", - mapped_pages, linear_pages, linear); - - /* We return the top level (guest-physical) address: the kernel needs - * to know where it is. */ - return (unsigned long)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++) { - strcpy(dst+len, args[i]); - strcat(dst+len, " "); - len += strlen(args[i]) + 1; - } - /* In case it's empty. */ - dst[len] = '\0'; -} - -/* 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 top physical page to allow, the top level pagetable, the entry point and - * the page_offset constant for the Guest. */ -static int tell_kernel(u32 pgdir, u32 start, u32 page_offset) -{ - u32 args[] = { LHREQ_INITIALIZE, - top/getpagesize(), pgdir, start, page_offset }; - int fd; - - 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 set_fd(int fd, struct device_list *devices) -{ - FD_SET(fd, &devices->infds); - if (fd > devices->max_infd) - devices->max_infd = fd; -} - -/*L:200 - * The Waker. - * - * With a console 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 filedescriptor to tell the Host - * loop to stop running the Guest. This causes it 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, struct device_list *devices) -{ - /* Add the pipe from the Launcher to the fdset in the device_list, so - * we watch it, too. */ - set_fd(pipefd, devices); - - for (;;) { - fd_set rfds = devices->infds; - u32 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 ignorefd; - /* If read() returns 0, it means the Launcher has - * exited. We silently follow. */ - if (read(pipefd, &ignorefd, sizeof(ignorefd)) == 0) - exit(0); - /* Otherwise it's telling us there's a problem with one - * of the devices, and we should ignore that file - * descriptor from now on. */ - FD_CLR(ignorefd, &devices->infds); - } else /* Send LHREQ_BREAK command. */ - write(lguest_fd, args, sizeof(args)); - } -} - -/* This routine just sets up a pipe to the Waker process. */ -static int setup_waker(int lguest_fd, struct device_list *device_list) -{ - 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) { - /* Close the "writing" end of our copy of the pipe */ - close(pipefd[1]); - wake_parent(pipefd[0], lguest_fd, device_list); - } - /* 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]; -} - -/*L:210 - * Device Handling. - * - * When the Guest sends DMA to us, it sends us 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 check 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 >= top || addr + size >= top) - errx(1, "%s:%i: Invalid address %li", __FILE__, line, addr); - /* We return a pointer for the caller's convenience, now we know it's - * safe to use. */ - return (void *)addr; -} -/* A macro which transparently hands the line number to the real function. */ -#define check_pointer(addr,size) _check_pointer(addr, size, __LINE__) - -/* The Guest has given us the address of a "struct lguest_dma". We check it's - * OK and convert it to an iovec (which is a simple array of ptr/size - * pairs). */ -static u32 *dma2iov(unsigned long dma, struct iovec iov[], unsigned *num) -{ - unsigned int i; - struct lguest_dma *udma; - - /* First we make sure that the array memory itself is valid. */ - udma = check_pointer(dma, sizeof(*udma)); - /* Now we check each element */ - for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) { - /* A zero length ends the array. */ - if (!udma->len[i]) - break; - - iov[i].iov_base = check_pointer(udma->addr[i], udma->len[i]); - iov[i].iov_len = udma->len[i]; - } - *num = i; - - /* We return the pointer to where the caller should write the amount of - * the buffer used. */ - return &udma->used_len; -} - -/* This routine gets a DMA buffer from the Guest for a given key, and converts - * it to an iovec array. It returns the interrupt the Guest wants when we're - * finished, and a pointer to the "used_len" field to fill in. */ -static u32 *get_dma_buffer(int fd, void *key, - struct iovec iov[], unsigned int *num, u32 *irq) -{ - u32 buf[] = { LHREQ_GETDMA, (u32)key }; - unsigned long udma; - u32 *res; - - /* Ask the kernel for a DMA buffer corresponding to this key. */ - udma = write(fd, buf, sizeof(buf)); - /* They haven't registered any, or they're all used? */ - if (udma == (unsigned long)-1) - return NULL; - - /* Convert it into our iovec array */ - res = dma2iov(udma, iov, num); - /* The kernel stashes irq in ->used_len to get it out to us. */ - *irq = *res; - /* Return a pointer to ((struct lguest_dma *)udma)->used_len. */ - return res; -} - -/* This is a convenient routine to send the Guest an interrupt. */ -static void trigger_irq(int fd, u32 irq) -{ - u32 buf[] = { LHREQ_IRQ, irq }; - if (write(fd, buf, sizeof(buf)) != 0) - err(1, "Triggering irq %i", irq); -} - -/* This simply sets up an iovec array where we can put data to be discarded. - * This happens when the Guest doesn't want or can't handle the input: we have - * to get rid of it somewhere, and if we bury it in the ceiling space it will - * start to smell after a week. */ -static void discard_iovec(struct iovec *iov, unsigned int *num) -{ - static char discard_buf[1024]; - *num = 1; - iov->iov_base = discard_buf; - iov->iov_len = sizeof(discard_buf); -} - -/* Here is the input terminal setting we save, and the routine to restore them - * on exit so the user can see what they type next. */ -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) -{ - u32 irq = 0, *lenp; - int len; - unsigned int num; - struct iovec iov[LGUEST_MAX_DMA_SECTIONS]; - struct console_abort *abort = dev->priv; - - /* First we get the console buffer from the Guest. The key is dev->mem - * which was set to 0 in setup_console(). */ - lenp = get_dma_buffer(fd, dev->mem, iov, &num, &irq); - if (!lenp) { - /* If it's not ready for input, warn and set up to discard. */ - warn("console: no dma buffer!"); - discard_iovec(iov, &num); - } - - /* 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, num); - if (len <= 0) { - /* This implies that the console is closed, is /dev/null, or - * something went terribly wrong. We still go through the rest - * of the logic, though, especially the exit handling below. */ - warnx("Failed to get console input, ignoring console."); - len = 0; - } - - /* If we read the data into the Guest, fill in the length and send the - * interrupt. */ - if (lenp) { - *lenp = len; - trigger_irq(fd, irq); - } - - /* 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) { - u32 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; - - /* Now, if we didn't read anything, put the input terminal back and - * return failure (meaning, don't call us again). */ - if (!len) { - restore_term(); - return false; - } - /* Everything went OK! */ - return true; -} - -/* Handling console output is much simpler than input. */ -static u32 handle_console_output(int fd, const struct iovec *iov, - unsigned num, struct device*dev) -{ - /* Whatever the Guest sends, write it to standard output. Return the - * number of bytes written. */ - return writev(STDOUT_FILENO, iov, num); -} - -/* Guest->Host network output is also pretty easy. */ -static u32 handle_tun_output(int fd, const struct iovec *iov, - unsigned num, struct device *dev) -{ - /* We put a flag in the "priv" pointer of the network device, and set - * it as soon as we see output. We'll see why in handle_tun_input() */ - *(bool *)dev->priv = true; - /* Whatever packet the Guest sent us, write it out to the tun - * device. */ - return writev(dev->fd, iov, num); -} - -/* This matches the peer_key() in lguest_net.c. The key for any given slot - * is the address of the network device's page plus 4 * the slot number. */ -static unsigned long peer_offset(unsigned int peernum) -{ - return 4 * peernum; -} - -/* This is where we handle a packet coming in from the tun device */ -static bool handle_tun_input(int fd, struct device *dev) -{ - u32 irq = 0, *lenp; - int len; - unsigned num; - struct iovec iov[LGUEST_MAX_DMA_SECTIONS]; - - /* First we get a buffer the Guest has bound to its key. */ - lenp = get_dma_buffer(fd, dev->mem+peer_offset(NET_PEERNUM), iov, &num, - &irq); - if (!lenp) { - /* Now, it's expected that if we try to send a packet too - * early, the Guest won't be ready yet. This is why we set a - * flag when the Guest sends its first packet. If it's sent a - * packet we assume it should be ready to receive them. - * - * Actually, this is what the status bits in the descriptor are - * for: we should *use* them. FIXME! */ - if (*(bool *)dev->priv) - warn("network: no dma buffer!"); - discard_iovec(iov, &num); - } - - /* Read the packet from the device directly into the Guest's buffer. */ - len = readv(dev->fd, iov, num); - if (len <= 0) - err(1, "reading network"); - - /* Write the used_len, and trigger the interrupt for the Guest */ - if (lenp) { - *lenp = len; - trigger_irq(fd, irq); - } - verbose("tun input packet len %i [%02x %02x] (%s)\n", len, - ((u8 *)iov[0].iov_base)[0], ((u8 *)iov[0].iov_base)[1], - lenp ? "sent" : "discarded"); - /* All good. */ - return true; -} - -/* The last device handling routine is block output: the Guest has sent a DMA - * to the block device. It will have placed the command it wants in the - * "struct lguest_block_page". */ -static u32 handle_block_output(int fd, const struct iovec *iov, - unsigned num, struct device *dev) -{ - struct lguest_block_page *p = dev->mem; - u32 irq, *lenp; - unsigned int len, reply_num; - struct iovec reply[LGUEST_MAX_DMA_SECTIONS]; - off64_t device_len, off = (off64_t)p->sector * 512; - - /* First we extract the device length from the dev->priv pointer. */ - device_len = *(off64_t *)dev->priv; - - /* We first check that the read or write is within the length of the - * block file. */ - if (off >= device_len) - err(1, "Bad offset %llu vs %llu", off, device_len); - /* Move to the right location in the block file. This shouldn't fail, - * but best to check. */ - if (lseek64(dev->fd, off, SEEK_SET) != off) - err(1, "Bad seek to sector %i", p->sector); - - verbose("Block: %s at offset %llu\n", p->type ? "WRITE" : "READ", off); - - /* They were supposed to bind a reply buffer at key equal to the start - * of the block device memory. We need this to tell them when the - * request is finished. */ - lenp = get_dma_buffer(fd, dev->mem, reply, &reply_num, &irq); - if (!lenp) - err(1, "Block request didn't give us a dma buffer"); - - if (p->type) { - /* A write request. The DMA they sent contained the data, so - * write it out. */ - len = writev(dev->fd, iov, num); - /* Grr... Now we know how long the "struct lguest_dma" they - * sent was, we make sure they didn't try to write over the end - * of the block file (possibly extending it). */ - if (off + len > device_len) { - /* Trim it back to the correct length */ - ftruncate64(dev->fd, device_len); - /* Die, bad Guest, die. */ - errx(1, "Write past end %llu+%u", off, len); - } - /* The reply length is 0: we just send back an empty DMA to - * interrupt them and tell them the write is finished. */ - *lenp = 0; - } else { - /* A read request. They sent an empty DMA to start the - * request, and we put the read contents into the reply - * buffer. */ - len = readv(dev->fd, reply, reply_num); - *lenp = len; - } - - /* The result is 1 (done), 2 if there was an error (short read or - * write). */ - p->result = 1 + (p->bytes != len); - /* Now tell them we've used their reply buffer. */ - trigger_irq(fd, irq); - - /* We're supposed to return the number of bytes of the output buffer we - * used. But the block device uses the "result" field instead, so we - * don't bother. */ - return 0; -} - -/* This is the generic routine we call when the Guest sends some DMA out. */ -static void handle_output(int fd, unsigned long dma, unsigned long key, - struct device_list *devices) -{ - struct device *i; - u32 *lenp; - struct iovec iov[LGUEST_MAX_DMA_SECTIONS]; - unsigned num = 0; - - /* Convert the "struct lguest_dma" they're sending to a "struct - * iovec". */ - lenp = dma2iov(dma, iov, &num); - - /* Check each device: if they expect output to this key, tell them to - * handle it. */ - for (i = devices->dev; i; i = i->next) { - if (i->handle_output && key == i->watch_key) { - /* We write the result straight into the used_len field - * for them. */ - *lenp = i->handle_output(fd, iov, num, i); - return; - } - } - - /* This can happen: the kernel sends any SEND_DMA which doesn't match - * another Guest to us. It could be that another Guest just left a - * network, for example. But it's unusual. */ - warnx("Pending dma %p, key %p", (void *)dma, (void *)key); -} - -/* This is called when the waker wakes us up: check for incoming file - * descriptors. */ -static void handle_input(int fd, struct device_list *devices) -{ - /* 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)) { - /* If handle_input() returns false, it means we - * should no longer service it. - * handle_console_input() does this. */ - if (!i->handle_input(fd, i)) { - /* Clear it from the set of input file - * descriptors kept at the head of the - * device list. */ - FD_CLR(i->fd, &devices->infds); - /* Tell waker to ignore it too... */ - write(waker_fd, &i->fd, sizeof(i->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 them. - * - * This routine allocates a new "struct lguest_device_desc" from descriptor - * table in the devices array just above the Guest's normal memory. */ -static struct lguest_device_desc * -new_dev_desc(struct lguest_device_desc *descs, - u16 type, u16 features, u16 num_pages) -{ - unsigned int i; - - for (i = 0; i < LGUEST_MAX_DEVICES; i++) { - if (!descs[i].type) { - descs[i].type = type; - descs[i].features = features; - descs[i].num_pages = num_pages; - /* If they said the device needs memory, we allocate - * that now, bumping up the top of Guest memory. */ - if (num_pages) { - map_zeroed_pages(top, num_pages); - descs[i].pfn = top/getpagesize(); - top += num_pages*getpagesize(); - } - return &descs[i]; - } - } - errx(1, "too many devices"); -} - -/* This monster routine does all the creation and setup of a new device, - * including caling new_dev_desc() to allocate the descriptor and device - * memory. */ -static struct device *new_device(struct device_list *devices, - u16 type, u16 num_pages, u16 features, - int fd, - bool (*handle_input)(int, struct device *), - unsigned long watch_off, - u32 (*handle_output)(int, - const struct iovec *, - unsigned, - struct device *)) -{ - struct device *dev = malloc(sizeof(*dev)); - - /* 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/lgba, etc. */ - *devices->lastdev = dev; - dev->next = NULL; - devices->lastdev = &dev->next; - - /* 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) - set_fd(dev->fd, devices); - dev->desc = new_dev_desc(devices->descs, type, features, num_pages); - dev->mem = (void *)(dev->desc->pfn * getpagesize()); - dev->handle_input = handle_input; - dev->watch_key = (unsigned long)dev->mem + watch_off; - dev->handle_output = handle_output; - 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(struct device_list *devices) -{ - 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); - } - - /* We don't currently require any memory for the console, so we ask for - * 0 pages. */ - dev = new_device(devices, LGUEST_DEVICE_T_CONSOLE, 0, 0, - STDIN_FILENO, handle_console_input, - LGUEST_CONSOLE_DMA_KEY, handle_console_output); - /* 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; - verbose("device %p: console\n", - (void *)(dev->desc->pfn * getpagesize())); -} - -/* Setting up a block file is also fairly straightforward. */ -static void setup_block_file(const char *filename, struct device_list *devices) -{ - int fd; - struct device *dev; - off64_t *device_len; - struct lguest_block_page *p; - - /* We open with O_LARGEFILE because otherwise we get stuck at 2G. We - * open with O_DIRECT because otherwise our benchmarks go much too - * fast. */ - fd = open_or_die(filename, O_RDWR|O_LARGEFILE|O_DIRECT); - - /* We want one page, and have no input handler (the block file never - * has anything interesting to say to us). Our timing will be quite - * random, so it should be a reasonable randomness source. */ - dev = new_device(devices, LGUEST_DEVICE_T_BLOCK, 1, - LGUEST_DEVICE_F_RANDOMNESS, - fd, NULL, 0, handle_block_output); - - /* We store the device size in the private area */ - device_len = dev->priv = malloc(sizeof(*device_len)); - /* This is the safe way of establishing the size of our device: it - * might be a normal file or an actual block device like /dev/hdb. */ - *device_len = lseek64(fd, 0, SEEK_END); - - /* The device memory is a "struct lguest_block_page". It's zeroed - * already, we just need to put in the device size. Block devices - * think in sectors (ie. 512 byte chunks), so we translate here. */ - p = dev->mem; - p->num_sectors = *device_len/512; - verbose("device %p: block %i sectors\n", - (void *)(dev->desc->pfn * getpagesize()), p->num_sectors); -} - -/* - * Network Devices. - * - * Setting up network devices is quite a pain, because we have three types. - * First, we have the inter-Guest network. This is a file which is mapped into - * the address space of the Guests who are on the network. Because it is a - * shared mapping, the same page underlies all the devices, and they can send - * DMA to each other. - * - * Remember from our network driver, the Guest is told what slot in the page it - * is to use. We use exclusive fnctl locks to reserve a slot. If another - * Guest is using a slot, the lock will fail and we try another. Because fnctl - * locks are cleaned up automatically when we die, this cleverly means that our - * reservation on the slot will vanish if we crash. */ -static unsigned int find_slot(int netfd, const char *filename) -{ - struct flock fl; - - fl.l_type = F_WRLCK; - fl.l_whence = SEEK_SET; - fl.l_len = 1; - /* Try a 1 byte lock in each possible position number */ - for (fl.l_start = 0; - fl.l_start < getpagesize()/sizeof(struct lguest_net); - fl.l_start++) { - /* If we succeed, return the slot number. */ - if (fcntl(netfd, F_SETLK, &fl) == 0) - return fl.l_start; - } - errx(1, "No free slots in network file %s", filename); -} - -/* This function sets up the network file */ -static void setup_net_file(const char *filename, - struct device_list *devices) -{ - int netfd; - struct device *dev; - - /* We don't use open_or_die() here: for friendliness we create the file - * if it doesn't already exist. */ - netfd = open(filename, O_RDWR, 0); - if (netfd < 0) { - if (errno == ENOENT) { - netfd = open(filename, O_RDWR|O_CREAT, 0600); - if (netfd >= 0) { - /* If we succeeded, initialize the file with a - * blank page. */ - char page[getpagesize()]; - memset(page, 0, sizeof(page)); - write(netfd, page, sizeof(page)); - } - } - if (netfd < 0) - err(1, "cannot open net file '%s'", filename); - } - - /* We need 1 page, and the features indicate the slot to use and that - * no checksum is needed. We never touch this device again; it's - * between the Guests on the network, so we don't register input or - * output handlers. */ - dev = new_device(devices, LGUEST_DEVICE_T_NET, 1, - find_slot(netfd, filename)|LGUEST_NET_F_NOCSUM, - -1, NULL, 0, NULL); - - /* Map the shared file. */ - if (mmap(dev->mem, getpagesize(), PROT_READ|PROT_WRITE, - MAP_FIXED|MAP_SHARED, netfd, 0) != dev->mem) - err(1, "could not mmap '%s'", filename); - verbose("device %p: shared net %s, peer %i\n", - (void *)(dev->desc->pfn * getpagesize()), filename, - dev->desc->features & ~LGUEST_NET_F_NOCSUM); -} -/*:*/ - -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 (in practice, the Host's slot in the network device's memory). */ -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 The other kind of network is a Host<->Guest network. This can either - * use briding 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_list *devices) -{ - struct device *dev; - struct ifreq ifr; - int netfd, ipfd; - u32 ip; - const char *br_name = NULL; - - /* 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); - - /* We create the net device with 1 page, using the features field of - * the descriptor to tell the Guest it is in slot 1 (NET_PEERNUM), and - * that the device has fairly random timing. We do *not* specify - * LGUEST_NET_F_NOCSUM: these packets can reach the real world. - * - * We will put our MAC address is slot 0 for the Guest to see, so - * it will send packets to us using the key "peer_offset(0)": */ - dev = new_device(devices, LGUEST_DEVICE_T_NET, 1, - NET_PEERNUM|LGUEST_DEVICE_F_RANDOMNESS, netfd, - handle_tun_input, peer_offset(0), handle_tun_output); - - /* We keep a flag which says whether we've seen packets come out from - * this network device. */ - dev->priv = malloc(sizeof(bool)); - *(bool *)dev->priv = false; - - /* 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); - - /* We are peer 0, ie. first slot, so we hand dev->mem to this routine - * to write the MAC address at the start of the device memory. */ - configure_device(ipfd, ifr.ifr_name, ip, dev->mem); - - /* Set "promisc" bit: we want every single packet if we're going to - * bridge to other machines (and otherwise it doesn't matter). */ - *((u8 *)dev->mem) |= 0x1; - - close(ipfd); - - verbose("device %p: tun net %u.%u.%u.%u\n", - (void *)(dev->desc->pfn * getpagesize()), - (u8)(ip>>24), (u8)(ip>>16), (u8)(ip>>8), (u8)ip); - if (br_name) - verbose("attached to bridge: %s\n", br_name); -} -/* That's the end of device setup. */ - -/*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, struct device_list *device_list) -{ - for (;;) { - u32 args[] = { LHREQ_BREAK, 0 }; - unsigned long arr[2]; - int readval; - - /* We read from the /dev/lguest device to run the Guest. */ - readval = read(lguest_fd, arr, sizeof(arr)); - - /* The read can only really return sizeof(arr) (the Guest did a - * SEND_DMA to us), or an error. */ - - /* For a successful read, arr[0] is the address of the "struct - * lguest_dma", and arr[1] is the key the Guest sent to. */ - if (readval == sizeof(arr)) { - handle_output(lguest_fd, arr[0], arr[1], device_list); - continue; - /* ENOENT means the Guest died. Reading tells us why. */ - } else if (errno == ENOENT) { - char reason[1024] = { 0 }; - read(lguest_fd, reason, sizeof(reason)-1); - errx(1, "%s", reason); - /* 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"); - - /* Service input, then unset the BREAK which releases - * the Waker. */ - handle_input(lguest_fd, device_list); - if (write(lguest_fd, args, sizeof(args)) < 0) - err(1, "Resetting break"); - } -} -/* - * This is the end of the Launcher. - * - * But wait! We've seen I/O from the Launcher, and we've seen I/O from the - * Drivers. If we were to see the Host kernel I/O code, our understanding - * would be complete... :*/ - -static struct option opts[] = { - { "verbose", 0, NULL, 'v' }, - { "sharenet", 1, NULL, 's' }, - { "tunnet", 1, NULL, 't' }, - { "block", 1, NULL, 'b' }, - { "initrd", 1, NULL, 'i' }, - { NULL }, -}; -static void usage(void) -{ - errx(1, "Usage: lguest [--verbose] " - "[--sharenet=<filename>|--tunnet=(<ipaddr>|bridge:<bridgename>)\n" - "|--block=<filename>|--initrd=<filename>]...\n" - "<mem-in-mb> vmlinux [args...]"); -} - -/*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 like 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 binary sits up high, usually starting at address 0xB8000000. - * Everything below this is the "physical" memory for the Guest. For example, - * if the Guest were to write a "1" at physical address 0, we would see a "1" - * in the Launcher at "(int *)0". Guest physical == Launcher virtual. - * - * This can be tough to get your head around, but usually it just means that we - * don't need to do any conversion when the Guest gives us it's "physical" - * addresses. - */ -int main(int argc, char *argv[]) -{ - /* Memory, top-level pagetable, code startpoint, PAGE_OFFSET and size - * of the (optional) initrd. */ - unsigned long mem = 0, pgdir, start, page_offset, initrd_size = 0; - /* A temporary and the /dev/lguest file descriptor. */ - int i, c, lguest_fd; - /* The list of Guest devices, based on command line arguments. */ - struct device_list device_list; - /* The boot information for the Guest: at guest-physical address 0. */ - void *boot = (void *)0; - /* If they specify an initrd file to load. */ - const char *initrd_name = NULL; - - /* 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, for easy appending - * to the list. */ - device_list.max_infd = -1; - device_list.dev = NULL; - device_list.lastdev = &device_list.dev; - FD_ZERO(&device_list.infds); - - /* 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 = top = atoi(argv[i]) * 1024 * 1024; - device_list.descs = map_zeroed_pages(top, 1); - top += getpagesize(); - 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 's': - setup_net_file(optarg, &device_list); - break; - case 't': - setup_tun_net(optarg, &device_list); - break; - case 'b': - setup_block_file(optarg, &device_list); - 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(); - - /* We always have a console device */ - setup_console(&device_list); - - /* 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. */ - map_zeroed_pages(0, mem / getpagesize()); - - /* Now we load the kernel */ - start = load_kernel(open_or_die(argv[optind+1], O_RDONLY), - &page_offset); - - /* 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. */ - *(unsigned long *)(boot+0x218) = mem - initrd_size; - *(unsigned long *)(boot+0x21c) = initrd_size; - /* The bootloader type 0xFF means "unknown"; that's OK. */ - *(unsigned char *)(boot+0x210) = 0xFF; - } - - /* Set up the initial linear pagetables, starting below the initrd. */ - pgdir = setup_pagetables(mem, initrd_size, page_offset); - - /* The Linux boot header contains an "E820" memory map: ours is a - * simple, single region. */ - *(char*)(boot+E820NR) = 1; - *((struct e820entry *)(boot+E820MAP)) - = ((struct e820entry) { 0, mem, E820_RAM }); - /* The boot header contains a command line pointer: we put the command - * line after the boot header (at address 4096) */ - *(void **)(boot + 0x228) = boot + 4096; - concat(boot + 4096, argv+optind+2); - - /* The guest type value of "1" tells the Guest it's under lguest. */ - *(int *)(boot + 0x23c) = 1; - - /* We tell the kernel to initialize the Guest: this returns the open - * /dev/lguest file descriptor. */ - lguest_fd = tell_kernel(pgdir, start, page_offset); - - /* We fork off a child process, which wakes the Launcher whenever one - * of the input file descriptors needs attention. Otherwise we would - * run the Guest until it tries to output something. */ - waker_fd = setup_waker(lguest_fd, &device_list); - - /* Finally, run the Guest. This doesn't return. */ - run_guest(lguest_fd, &device_list); -} -/*:*/ - -/*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. - */ |